diff --git a/.github/workflows/benchmarks.yml b/.github/workflows/benchmarks.yml
index c3b07ebbc..6aca49db1 100644
--- a/.github/workflows/benchmarks.yml
+++ b/.github/workflows/benchmarks.yml
@@ -10,10 +10,15 @@ jobs:
   benchmark:
     if: ${{ contains( github.event.pull_request.labels.*.name, 'run-benchmark') && github.event_name == 'pull_request' || github.event_name == 'workflow_dispatch' }}
     name: Linux
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     env:
       ASV_DIR: "./asv_bench"
-
+    defaults:
+      run:
+        shell: bash -l {0}
+    strategy:
+      matrix:
+        python-version: ["3.10"]
     steps:
       # We need the full repo to avoid this issue
       # https://github.com/actions/checkout/issues/23
@@ -21,19 +26,20 @@ jobs:
         with:
           fetch-depth: 0
 
-      - name: Setup Miniconda
-        uses: conda-incubator/setup-miniconda@v3
+      - name: Set up conda (micromamba)
+        uses: mamba-org/setup-micromamba@v1
         with:
-          # installer-url: https://github.com/conda-forge/miniforge/releases/latest/download/Mambaforge-Linux-x86_64.sh
-          installer-url: https://github.com/conda-forge/miniforge/releases/latest/download/Miniforge3-Linux-x86_64.sh
+          environment-name: climpred-benchmarks
+          cache-environment: true
+          create-args: >-
+            python=${{ matrix.python-version }}
+            conda
 
-      - name: Setup some dependencies
-        shell: bash -l {0}
+      - name: Set Up Dependencies
         run: |
-          pip install asv
+          python -m pip install asv
           sudo apt-get update -y
       - name: Run benchmarks
-        shell: bash -l {0}
         id: benchmark
         env:
           OPENBLAS_NUM_THREADS: 1
diff --git a/.github/workflows/climpred_installs.yml b/.github/workflows/climpred_installs.yml
index 40294610e..7b22c1589 100644
--- a/.github/workflows/climpred_installs.yml
+++ b/.github/workflows/climpred_installs.yml
@@ -25,7 +25,7 @@ jobs:
           keyword: "[skip-ci]"
 
   install-climpred-complete:  # Installs climpred on various OS.
-    name: Install climpred[complete], ${{ matrix.os }}
+    name: Install climpred[complete], ${{ matrix.os }}, Python${{ matrix.python-version }}
     runs-on: ${{ matrix.os }}
     needs: detect-ci-trigger
     if: needs.detect-ci-trigger.outputs.triggered == 'false'
@@ -33,19 +33,20 @@ jobs:
       fail-fast: false
       matrix:
         os: ["ubuntu-latest", "macos-latest", "windows-latest"]
+        python-version: ["3.9"]
     steps:
     - uses: actions/checkout@v4
     - name: Setup Python
       uses: actions/setup-python@v5
       with:
-        python-version: 3.9
+        python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
         pip install -e .[complete]
         python -c "import climpred"
 
   install-climpred:  # Installs climpred on various OS.
-    name: Install climpred, ${{ matrix.os }}
+    name: Install climpred, ${{ matrix.os }}, Python${{ matrix.python-version }}
     runs-on: ${{ matrix.os }}
     needs: detect-ci-trigger
     if: needs.detect-ci-trigger.outputs.triggered == 'false'
@@ -53,6 +54,7 @@ jobs:
       fail-fast: false
       matrix:
         os: ["ubuntu-latest", "macos-latest", "windows-latest"]
+        python-version: ["3.9"]
     steps:
     - uses: actions/checkout@v4
       with:
@@ -60,7 +62,7 @@ jobs:
     - name: Setup Python
       uses: actions/setup-python@v5
       with:
-        python-version: 3.9
+        python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
         pip install -e .
diff --git a/.github/workflows/climpred_testing.yml b/.github/workflows/climpred_testing.yml
index 7f84f6734..af9532850 100644
--- a/.github/workflows/climpred_testing.yml
+++ b/.github/workflows/climpred_testing.yml
@@ -27,13 +27,16 @@ jobs:
           keyword: "[skip-ci]"
 
   minimum-test:  # Runs testing suite with minimal dependencies
-    name: Test minimum dependencies, Python3.9
+    name: Test minimum dependencies, Python${{ matrix.python-version }}
     runs-on: ubuntu-latest
     needs: detect-ci-trigger
     if: needs.detect-ci-trigger.outputs.triggered == 'false'
     defaults:
         run:
           shell: bash -l {0}
+    strategy:
+      matrix:
+        python-version: ["3.9", "3.12"]
     steps:
       - uses: actions/checkout@v4
         with:
@@ -45,7 +48,7 @@ jobs:
           environment-name: climpred-minimum-tests
           cache-environment: true
           create-args: >-
-            python=3.9
+            python=${{ matrix.python-version }}
             conda
       - name: Install climpred
         run: |
@@ -75,16 +78,22 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        env: [""]
         include:
           - env: "climpred-maximum-tests"
             python-version: "3.9"
+            extras: "esmpy=*=mpi*"  # Ensures MPI works with version of esmpy.
             os: ubuntu-latest
           - env: "climpred-maximum-tests"
             python-version: "3.10"
+            extras: "esmpy=*=mpi*"  # Ensures MPI works with version of esmpy.
             os: ubuntu-latest
           - env: "climpred-maximum-tests-upstream"
             python-version: "3.11"
+            extras: "esmpy=*=mpi*"  # Ensures MPI works with version of esmpy.
+            os: ubuntu-latest
+          - env: "climpred-maximum-tests"
+            python-version: "3.12"
+            extras: "esmpy"  # MPI is not supported in lastest esmpy conda packages for Python3.12
             os: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -96,10 +105,11 @@ jobs:
           environment-file: ci/requirements/maximum-tests.yml
           environment-name: climpred-maximum-tests
           cache-environment: true
-          cache-environment-key: "${{runner.os}}-${{runner.arch}}-py${{matrix.python-version}}-${{env.TODAY}}-${{hashFiles(env.CONDA_ENV_FILE)}}"
+          cache-environment-key: "${{ runner.os }}-${{ runner.arch }}-py${{ matrix.python-version }}-${{ env.TODAY }}-${{ hashFiles(env.CONDA_ENV_FILE) }}"
           create-args: >-
-            python=${{matrix.python-version}}
             conda
+            python=${{ matrix.python-version }}
+            ${{ matrix.extras }}
       - name: Install climpred[complete]
         run: |
           python -m pip install -e .[complete]
@@ -128,11 +138,14 @@ jobs:
           fail_ci_if_error: false
 
   doctest:  # tests all docstrings
-    name: Doctests, Python3.9
-    runs-on: "ubuntu-latest"
+    name: Doctests, Python${{ matrix.python-version }}
+    runs-on: ubuntu-latest
     defaults:
       run:
         shell: bash -l {0}
+    strategy:
+      matrix:
+        python-version: ["3.9"]
     steps:
       - uses: actions/checkout@v4
       - name: Setup conda (micromamba)
@@ -142,7 +155,7 @@ jobs:
           environment-name: climpred-maximum-tests
           cache-environment: true
           create-args: >-
-            python=3.9
+            python=${{ matrix.python-version }}
             conda
       - name: Install climpred[complete]
         run: |
@@ -156,14 +169,17 @@ jobs:
           conda list
       - name: Run doctests
         run: |
-          python -m pytest --doctest-modules climpred --ignore climpred/tests
+          python -m pytest --doctest-modules src/climpred --ignore src/climpred/tests
 
   notebooks:  # Checks that pre-compiled notebooks in docs still work.
-    name: Notebooks, Python3.9
+    name: Notebooks, Python${{ matrix.python-version }}
     runs-on: ubuntu-latest
     defaults:
         run:
           shell: bash -l {0}
+    strategy:
+      matrix:
+        python-version: ["3.9"]
     steps:
       - uses: actions/checkout@v4
       - name: Set up conda (micromamba)
@@ -173,7 +189,7 @@ jobs:
           environment-name: climpred-docs
           cache-environment: true
           create-args: >-
-            python=3.9
+            python=${{ matrix.python-version }}
             conda
       - name: Install climpred
         run: |
diff --git a/.github/workflows/publish-production-pypi.yml b/.github/workflows/publish-production-pypi.yml
index ca775f328..8988b16e1 100644
--- a/.github/workflows/publish-production-pypi.yml
+++ b/.github/workflows/publish-production-pypi.yml
@@ -17,7 +17,7 @@ jobs:
       - name: Set up Python3
         uses: actions/setup-python@v5
         with:
-          python-version: '3.x'
+          python-version: "3.x"
       - name: Install packaging libraries
         run: |
           python -m pip install --upgrade pip
diff --git a/.github/workflows/publish-staging-testpypi.yml b/.github/workflows/publish-staging-testpypi.yml
index 17042ef3a..822cba1c8 100644
--- a/.github/workflows/publish-staging-testpypi.yml
+++ b/.github/workflows/publish-staging-testpypi.yml
@@ -34,7 +34,7 @@ jobs:
     - name: Set up Python3
       uses: actions/setup-python@v5
       with:
-        python-version: '3.x'
+        python-version: "3.x"
     - name: Install packaging libraries
       run: |
         python -m pip install --upgrade pip
diff --git a/.github/workflows/upstream-dev-ci.yml b/.github/workflows/upstream-dev-ci.yml
index 953433c31..7b6bf1c56 100644
--- a/.github/workflows/upstream-dev-ci.yml
+++ b/.github/workflows/upstream-dev-ci.yml
@@ -28,7 +28,7 @@ jobs:
           keyword: "[test-upstream]"
 
   upstream-dev:
-    name: upstream-dev
+    name: upstream-dev, Python${{ matrix.python-version }}
     runs-on: ubuntu-latest
     needs: detect-ci-trigger
     if: |
diff --git a/.gitignore b/.gitignore
index 80b2ee324..238a9947a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -114,6 +114,10 @@ asv_bench/.asv/
 # VS Code
 .vscode/
 
+# PyCharm
+.idea/
+
+# dask
 dask-worker-space
 
 # End of https://www.gitignore.io/api/python
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index e0c08fcea..10b7a292f 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -21,6 +21,11 @@ repos:
         exclude: '.ipynb|asv.conf.json'
       - id: trailing-whitespace
 
+  -   repo: https://github.com/pappasam/toml-sort
+      rev: v0.23.1
+      hooks:
+      - id: toml-sort-fix
+
   -   repo: https://github.com/psf/black-pre-commit-mirror
       rev: 24.4.2
       hooks:
@@ -30,6 +35,7 @@ repos:
       rev: 7.1.0
       hooks:
       - id: flake8
+        args: [ '--max-line-length=93', '--extend-ignore=W503' ]
 
   -   repo: https://github.com/PyCQA/isort
       rev: 5.13.2
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index d70fa3127..86fa860d5 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -22,6 +22,9 @@ Internals/Minor Fixes
 - Fixed some issues with the documentation build to address rendering errors and reduce the number of warnings on ReadTheDocs. (pr:`843`) `Trevor James Smith`_
 - Fixed some issues with the typing hints of classes functions. (pr:`850`) `Trevor James Smith`_
 - Fixed several issues with incompatible dependency configurations in the CI and addressed a few deprecations. (pr:`861`) `Trevor James Smith`_
+- `climpred` has adopted `PEP 621 <https://peps.python.org/pep-0621/>`_ for specifying project metadata. (pr:`862`) `Trevor James Smith`_
+- `climpred` now uses the `src layout <https://packaging.python.org/en/latest/discussions/src-layout-vs-flat-layout/>`_  for the package file structure. (pr:`862`) `Trevor James Smith`_
+- Drop ``python<=3.8`` support. (:pr:`862`) `Trevor James Smith`_.
 
 climpred v2.4.0 (2023-11-09)
 ============================
@@ -224,7 +227,6 @@ Data variables:
   using :py:func:`~climpred.reference.compute_persistence_from_first_lead`.
   (:issue:`637`, :pr:`706`) `Aaron Spring`_.
 
-
 Internals/Minor Fixes
 ---------------------
 - Reduce dependencies. (:pr:`686`) `Aaron Spring`_.
@@ -1038,6 +1040,7 @@ Documentation
 - Add page for `publications <publications.html>`_ and
   `helpful links <helpful-links.html>`_. (:pr:`270`) `Riley X. Brady`_.
 
+
 climpred v1.1.0 (2019-09-23)
 ============================
 
@@ -1072,6 +1075,7 @@ Documentation
 - Add scope of package to docs for clarity for users and developers. (:pr:`235`)
   `Riley X. Brady`_.
 
+
 climpred v1.0.1 (2019-07-04)
 ============================
 
diff --git a/README.rst b/README.rst
index 0442c3350..324c86597 100644
--- a/README.rst
+++ b/README.rst
@@ -1,6 +1,6 @@
 .. image:: https://i.imgur.com/HPOdOsR.png
 
-Verification of weather and climate forecasts.
+Verification of weather and climate forecasts
 
 ..
     Table version of badges inspired by pySTEPS.
@@ -128,7 +128,7 @@ You can install the latest release of ``climpred`` using ``pip`` or ``conda``:
 
 .. code-block:: bash
 
-    pip install climpred[complete]
+    python -m pip install climpred[complete]
 
 .. code-block:: bash
 
@@ -141,7 +141,7 @@ repository or installing directly from GitHub:
 
     git clone https://github.com/pangeo-data/climpred.git
     cd climpred
-    pip install . --upgrade
+    python -m pip install . --upgrade
 
 .. code-block:: bash
 
diff --git a/ci/requirements/docs.yml b/ci/requirements/docs.yml
index d72256738..e0043da2d 100644
--- a/ci/requirements/docs.yml
+++ b/ci/requirements/docs.yml
@@ -29,7 +29,7 @@ dependencies:
   - importlib-metadata <8.0.0 # Pin needed for esmpy compatibility. See: https://github.com/pangeo-data/xESMF/issues/374
   - nc-time-axis >=1.4.0
   - numba >=0.52
-  - numpy >=1.25.0
+  - numpy >=1.25.0,<2.0.0  # Pin below v2.0.0 until xclim supports it.
   - xclim
   - xesmf
   - xrft
diff --git a/ci/requirements/maximum-tests.yml b/ci/requirements/maximum-tests.yml
index e91ee1a19..3964f510f 100644
--- a/ci/requirements/maximum-tests.yml
+++ b/ci/requirements/maximum-tests.yml
@@ -3,18 +3,18 @@ channels:
   - conda-forge
   - nodefaults
 dependencies:
-  - python >=3.9
+  - python >=3.9,<3.13
   - bias_correction
   - cftime >=1.5.0
   - coveralls
   - dask-core
   - eofs
-  - esmpy =*=mpi*  # Ensures MPI works with version of esmpy.
+  # - esmpy =*=mpi*  # Ensures MPI works with version of esmpy. # Commented out for CI testing.
   - h5netcdf
-  - importlib-metadata <8.0.0 # Pin needed for esmpy compatibility. See: https://github.com/pangeo-data/xESMF/issues/374
+  - importlib-metadata <8.0.0  # Pin needed for esmpy compatibility. See: https://github.com/pangeo-data/xESMF/issues/374
   - matplotlib-base
   - nc-time-axis >=1.4.0
-  - numpy >=1.25.0
+  - numpy >=1.25.0,<2.0.0  # Pin below v2.0.0 until xclim supports it.
   - pip
   - pooch
   - pytest <8.0.0
diff --git a/ci/requirements/minimum-tests.yml b/ci/requirements/minimum-tests.yml
index d9be0fa2a..a6cd92acd 100644
--- a/ci/requirements/minimum-tests.yml
+++ b/ci/requirements/minimum-tests.yml
@@ -3,7 +3,7 @@ channels:
   - conda-forge
   - nodefaults
 dependencies:
-  - python >=3.9,<3.10
+  - python >=3.9,<3.13
   - cftime >=1.5.0
   - coveralls
   - dask-core
diff --git a/pyproject.toml b/pyproject.toml
index 09c112759..2d9c6391c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,14 +1,160 @@
+[build-system]
+requires = [
+  "setuptools>=64",
+  "setuptools_scm>=8",
+  "wheel"
+]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "climpred"
+authors = [
+  {name = "Aaron Spring", email = "aaron.spring@mpimet.mpg.de"},
+  {name = "Riley Brady", email = "riley.brady@colorado.edu"}
+]
+maintainers = [
+  {name = "Aaron Spring", email = "aaron.spring@mpimet.mpg.de"},
+  {name = "Trevor James Smith", email = "smith.trevorj@ouranos.ca"}
+]
+readme = "README.rst"
+license = {file = "LICENSE.txt"}
+requires-python = ">=3.9"
+classifiers = [
+  "Development Status :: 5 - Production/Stable",
+  "Intended Audience :: Education",
+  "Intended Audience :: Science/Research",
+  "License :: OSI Approved :: MIT License",
+  "Natural Language :: English",
+  "Operating System :: OS Independent",
+  "Programming Language :: Python :: 3 :: Only",
+  "Programming Language :: Python :: 3.9",
+  "Programming Language :: Python :: 3.10",
+  "Programming Language :: Python :: 3.11",
+  "Programming Language :: Python :: 3.12",
+  "Topic :: Scientific/Engineering :: Atmospheric Science"
+]
+dependencies = [
+  "cf_xarray >=0.6.0",
+  "cftime >=1.5.0",
+  "dask >=2021.10.0",
+  "numpy >=1.25.0",
+  "packaging",
+  "pooch >=1.4",
+  "xarray >=0.19.0",
+  "xskillscore >=0.0.20"
+]
+dynamic = ["version", "description"]
+
+[project.optional-dependencies]
+accel = ["numba >=0.52", "bottleneck"]
+bias-correction = ["xclim >=0.46", "bias-correction >=0.4", "numpy >=1.25.0,<2.0.0"] # pinned until xclim supports numpy>=2.0.0
+io = ["netcdf4"] # use h5netcdf when encountering seg faults as in GitHub Actions CI
+regridding = ["xesmf"] # for installation see https://pangeo-xesmf.readthedocs.io/
+relative_entropy = ["eofs"]
+test = ["netcdf4", "pre-commit", "pytest <8.0.0", "pytest-cov", "pytest-lazy-fixture", "pytest-xdist"]
+viz = ["matplotlib", "nc-time-axis >=1.4.0"]
+vwmp = ["xrft"]
+complete = ["climpred[accel,bias-correction,viz,io,test,relative_entropy,vwmp]"]
+docs = [
+  "climpred[complete]",
+  "myst_nb",
+  "sphinx",
+  "sphinx-book-theme >=0.3.3",
+  "sphinx-copybutton",
+  "sphinxcontrib-bibtex",
+  "sphinxcontrib-napoleon"
+]
+
+[project.urls]
+"Homepage" = "https://climpred.readthedocs.io/en/stable/"
+"Source" = "https://github.com/pangeo-data/climpred"
+"Changelog" = "https://climpred.readthedocs.io/en/stable/changelog.html"
+"Issue Tracker" = "https://github.com/pangeo-data/climpred/issues"
+
 [tool.black]
 line-length = 88
+target-version = ["py39", "py310", "py311", "py312"]
 
-[build-system]
- requires = [
-     "setuptools>=42",
-     "wheel",
-     "setuptools_scm[toml]>=3.4",
-     "setuptools_scm_git_archive",
- ]
- build-backend = "setuptools.build_meta"
-
- [tool.setuptools_scm]
- fallback_version = "999"
+[tool.isort]
+known_first_party = "climpred"
+multi_line_output = 3
+include_trailing_comma = true
+force_grid_wrap = 0
+use_parentheses = true
+line_length = 88
+combine_as_imports = true
+skip = [
+  "docs/source/conf.py"
+]
+
+[tool.mypy]
+exclude = "asv_bench|doc"
+files = "."
+show_error_codes = true
+ignore_missing_imports = true
+
+[tool.mypy.overrides]
+"bottleneck.*" = {ignore_missing_imports = true}
+"cftime.*" = {ignore_missing_imports = true}
+"mypy-dask.*" = {ignore_missing_imports = true}
+"mypy-distributed.*" = {ignore_missing_imports = true}
+"mypy-fsspec.*" = {ignore_missing_imports = true}
+"mypy-matplotlib.*" = {ignore_missing_imports = true}
+"mypy-nc_time_axis.*" = {ignore_missing_imports = true}
+"mypy-numpy.*" = {ignore_missing_imports = true}
+"mypy-netCDF4.*" = {ignore_missing_imports = true}
+"mypy-pandas.*" = {ignore_missing_imports = true}
+"mypy-pytest.*" = {ignore_missing_imports = true}
+"mypy-scipy.*" = {ignore_missing_imports = true}
+"mypy-setuptools" = {ignore_missing_imports = true}
+"mypy-toolz.*" = {ignore_missing_imports = true}
+
+[tool.pytest.ini_options]
+python_files = ["test_*.py"]
+addopts = [
+  "--color=yes",
+  "--verbose"
+]
+testpaths = [
+  "climpred/tests"
+]
+filterwarnings = [
+  # xarray
+  "ignore: Using a non-tuple sequence for multidimensional indexing is deprecated:FutureWarning",
+  # upstream xarray
+  "ignore: Mean of empty slice:RuntimeWarning",
+  # only shows up during CI: no idea where its coming from, something inside bootstrapping
+  "ignore: `np.alen` is deprecated, use `len` instead:DeprecationWarning",
+  # ignore UserWarnings raise by warnings.warn() which do not break functionality
+  # therefore ignore in testing
+  "ignore::UserWarning",
+  # xarray
+  "ignore: tostring:DeprecationWarning",
+  # properscoring
+  "ignore: invalid value encountered:RuntimeWarning",
+  "ignore: divide by zero:RuntimeWarning",
+  # xarray
+  "ignore: 'base' in .resample():FutureWarning",
+  # matplotlib
+  "ignore: More than 20 figures:RuntimeWarning",
+  # numpy https://stackoverflow.com/questions/40659212/futurewarning-elementwise-comparison-failed-returning-scalar-but-in-the-futur#46721064
+  "ignore: elementwise comparison failed",
+  # pydap
+  "ignore: Using or importing the ABCs from",
+  # xarray
+  "ignore: Passing method to CFTimeIndex.get_loc is deprecated",
+  # statsmodels
+  "ignore: pandas.Int64Index is deprecated"
+]
+markers = [
+  "mistral: tests requiring being on MPI supercomputer",
+  "slow: marks tests as slow (deselect with '-m \"not slow\"')"
+]
+
+[tool.setuptools.dynamic]
+description = {file = "src/climpred/__init__.py"}
+
+[tool.setuptools_scm]
+fallback_version = "999"
+version_scheme = "post-release"
+local_scheme = "dirty-tag"
diff --git a/requirements.txt b/requirements.txt
deleted file mode 100644
index 8fbfcefd8..000000000
--- a/requirements.txt
+++ /dev/null
@@ -1,8 +0,0 @@
-cf_xarray>=0.6.0
-cftime>=1.5.0
-dask>=2021.10.0
-numpy>=1.25.0
-packaging
-pooch>=1.4
-xarray>=0.19.0
-xskillscore>=0.0.20
diff --git a/setup.cfg b/setup.cfg
deleted file mode 100644
index 928477613..000000000
--- a/setup.cfg
+++ /dev/null
@@ -1,109 +0,0 @@
-[bdist_wheel]
-universal = 1
-
-[flake8]
-ignore = W503
-# allowing doctests
-max-line-length = 93
-
-[black]
-line-length = 88
-
-[isort]
-known_first_party=climpred
-multi_line_output=3
-include_trailing_comma=True
-force_grid_wrap=0
-use_parentheses=True
-line_length = 88
-combine_as_imports=True
-skip=
-    docs/source/conf.py
-    setup.py
-
-[tool:pytest]
-python_files=test_*.py
-addopts =
-    --color=yes
-    --verbose
-testpaths=climpred/tests
-filterwarnings =
-    # from xarray
-    ignore:Using a non-tuple sequence for multidimensional indexing is deprecated:FutureWarning
-    # upstream xarray
-    ignore: Mean of empty slice:RuntimeWarning
-    # upstream xarray
-    ignore:dropping variables using `drop` will be deprecated; using drop_vars is encouraged:PendingDeprecationWarning
-    # only shows up during CI: no idea where its coming from, something inside bootstrapping
-    ignore:`np.alen` is deprecated, use `len` instead:DeprecationWarning
-    # ignore UserWarnings raise by warnings.warn() which do not break functionality
-    # therefore ignore in testing
-    ignore::UserWarning
-    # from xarray
-    ignore:tostring:DeprecationWarning
-    # from properscoring
-    ignore: invalid value encountered:RuntimeWarning
-    ignore: divide by zero:RuntimeWarning
-    # from xarray
-    ignore: 'base' in .resample():FutureWarning
-    # matplotlib
-    ignore: More than 20 figures:RuntimeWarning
-    # numpy https://stackoverflow.com/questions/40659212/futurewarning-elementwise-comparison-failed-returning-scalar-but-in-the-futur#46721064
-    ignore: elementwise comparison failed
-    # pydap
-    ignore: Using or importing the ABCs from
-    # xarray
-    ignore: Passing method to CFTimeIndex.get_loc is deprecated
-    # statsmodels
-    ignore: pandas.Int64Index is deprecated
-markers =
-    mistral: tests requiring being on MPI supercomputer
-    markers =
-    slow: marks tests as slow (deselect with '-m "not slow"')
-    serial
-
-[aliases]
-test = pytest
-
-[doc8]
-max-line-length=88
-ignore-path=climpred/tests
-
-[mypy]
-exclude = asv_bench|doc
-files = .
-show_error_codes = True
-
-# Most of the numerical computing stack doesn't have type annotations yet.
-[mypy-bottleneck.*]
-ignore_missing_imports = True
-[mypy-cftime.*]
-ignore_missing_imports = True
-[mypy-dask.*]
-ignore_missing_imports = True
-[mypy-distributed.*]
-ignore_missing_imports = True
-[mypy-fsspec.*]
-ignore_missing_imports = True
-[mypy-matplotlib.*]
-ignore_missing_imports = True
-[mypy-nc_time_axis.*]
-ignore_missing_imports = True
-[mypy-numpy.*]
-ignore_missing_imports = True
-[mypy-netCDF4.*]
-ignore_missing_imports = True
-[mypy-pandas.*]
-ignore_missing_imports = True
-[mypy-pytest.*]
-ignore_missing_imports = True
-[mypy-scipy.*]
-ignore_missing_imports = True
-[mypy-setuptools]
-ignore_missing_imports = True
-[mypy-toolz.*]
-ignore_missing_imports = True
-# version spanning code is hard to type annotate (and most of this module will
-# be going away soon anyways)
-[mypy-xarray.core.pycompat]
-ignore_errors = True
diff --git a/setup.py b/setup.py
deleted file mode 100644
index 07c59210e..000000000
--- a/setup.py
+++ /dev/null
@@ -1,79 +0,0 @@
-from os.path import exists
-
-from setuptools import find_packages, setup
-
-if exists("README.rst"):
-    with open("README.rst") as f:
-        long_description = f.read()
-else:
-    long_description = ""
-
-with open("requirements.txt") as f:
-    install_requires = f.read().strip().split("\n")
-
-CLASSIFIERS = [
-    "Development Status :: 5 - Production/Stable",
-    "Intended Audience :: Education",
-    "Intended Audience :: Science/Research",
-    "License :: OSI Approved :: MIT License",
-    "Natural Language :: English",
-    "Operating System :: OS Independent",
-    "Programming Language :: Python :: 3 :: Only",
-    "Programming Language :: Python :: 3.8",
-    "Programming Language :: Python :: 3.9",
-    "Programming Language :: Python :: 3.10",
-    "Programming Language :: Python :: 3.11",
-    "Topic :: Scientific/Engineering :: Atmospheric Science",
-]
-
-extras_require = {
-    "accel": ["numba>=0.52", "bottleneck"],
-    "bias-correction": ["xclim>=0.46", "bias-correction>=0.4"],
-    "viz": ["matplotlib", "nc-time-axis>=1.4.0"],
-    "io": ["netcdf4"],  # use h5netcdf when encountering seg faults as in GHA CI
-    "regridding": [
-        "xesmf"
-    ],  # for installation see https://pangeo-xesmf.readthedocs.io/
-    "relative_entropy": ["eofs"],
-    "vwmp": ["xrft"],
-}
-extras_require["complete"] = sorted({v for req in extras_require.values() for v in req})
-extras_require["complete"].remove(
-    "xesmf"
-)  # circumventing esmpy/xesmf installation issues; use conda
-# after complete is set, add in test
-extras_require["test"] = [
-    "netcdf4",
-    "pre-commit",
-    "pytest<8",
-    "pytest-cov",
-    "pytest-lazy-fixture",
-    "pytest-xdist",
-]
-extras_require["docs"] = extras_require["complete"] + [
-    "myst_nb",
-    "sphinx",
-    "sphinx-copybutton",
-    "sphinx-book-theme>=0.3.3",
-    "sphinxcontrib-bibtex",
-    "sphinxcontrib-napoleon",
-]
-
-setup(
-    maintainer="Aaron Spring",
-    maintainer_email="aaron.spring@mpimet.mpg.de",
-    description="Verification of weather and climate forecasts." + " prediction.",
-    install_requires=install_requires,
-    python_requires=">=3.8",
-    license="MIT",
-    long_description=long_description,
-    classifiers=CLASSIFIERS,
-    name="climpred",
-    packages=find_packages(),
-    test_suite="climpred/tests",
-    tests_require=["pytest"],
-    url="https://github.com/pangeo-data/climpred",
-    use_scm_version={"version_scheme": "post-release", "local_scheme": "dirty-tag"},
-    zip_safe=False,
-    extras_require=extras_require,
-)
diff --git a/climpred/__init__.py b/src/climpred/__init__.py
similarity index 90%
rename from climpred/__init__.py
rename to src/climpred/__init__.py
index 6e3de9023..6fed9f331 100644
--- a/climpred/__init__.py
+++ b/src/climpred/__init__.py
@@ -1,3 +1,5 @@
+"""Verification of weather and climate forecasts and prediction."""
+
 # flake8: noqa
 from importlib.metadata import PackageNotFoundError, version as _get_version
 
diff --git a/climpred/alignment.py b/src/climpred/alignment.py
similarity index 100%
rename from climpred/alignment.py
rename to src/climpred/alignment.py
diff --git a/climpred/bias_removal.py b/src/climpred/bias_removal.py
similarity index 100%
rename from climpred/bias_removal.py
rename to src/climpred/bias_removal.py
diff --git a/climpred/bootstrap.py b/src/climpred/bootstrap.py
similarity index 99%
rename from climpred/bootstrap.py
rename to src/climpred/bootstrap.py
index 066b60c7f..4ef60a2a2 100644
--- a/climpred/bootstrap.py
+++ b/src/climpred/bootstrap.py
@@ -394,7 +394,7 @@ def _maybe_auto_chunk(ds, dims):
         xr.Dataset: auto-chunked along `dims`
 
     """
-    if dask.is_dask_collection(ds) and dims is not []:
+    if dask.is_dask_collection(ds) and dims != []:
         if isinstance(dims, str):
             dims = [dims]
         chunks = [d for d in dims if d in ds.dims]
diff --git a/climpred/checks.py b/src/climpred/checks.py
similarity index 100%
rename from climpred/checks.py
rename to src/climpred/checks.py
diff --git a/climpred/classes.py b/src/climpred/classes.py
similarity index 100%
rename from climpred/classes.py
rename to src/climpred/classes.py
diff --git a/climpred/comparisons.py b/src/climpred/comparisons.py
similarity index 100%
rename from climpred/comparisons.py
rename to src/climpred/comparisons.py
diff --git a/climpred/conftest.py b/src/climpred/conftest.py
similarity index 100%
rename from climpred/conftest.py
rename to src/climpred/conftest.py
diff --git a/climpred/constants.py b/src/climpred/constants.py
similarity index 100%
rename from climpred/constants.py
rename to src/climpred/constants.py
diff --git a/climpred/exceptions.py b/src/climpred/exceptions.py
similarity index 100%
rename from climpred/exceptions.py
rename to src/climpred/exceptions.py
diff --git a/climpred/graphics.py b/src/climpred/graphics.py
similarity index 100%
rename from climpred/graphics.py
rename to src/climpred/graphics.py
diff --git a/climpred/horizon.py b/src/climpred/horizon.py
similarity index 100%
rename from climpred/horizon.py
rename to src/climpred/horizon.py
diff --git a/climpred/logging.py b/src/climpred/logging.py
similarity index 100%
rename from climpred/logging.py
rename to src/climpred/logging.py
diff --git a/climpred/metrics.py b/src/climpred/metrics.py
similarity index 100%
rename from climpred/metrics.py
rename to src/climpred/metrics.py
diff --git a/climpred/options.py b/src/climpred/options.py
similarity index 100%
rename from climpred/options.py
rename to src/climpred/options.py
diff --git a/climpred/prediction.py b/src/climpred/prediction.py
similarity index 100%
rename from climpred/prediction.py
rename to src/climpred/prediction.py
diff --git a/climpred/preprocessing/__init__.py b/src/climpred/preprocessing/__init__.py
similarity index 100%
rename from climpred/preprocessing/__init__.py
rename to src/climpred/preprocessing/__init__.py
diff --git a/climpred/preprocessing/mpi.py b/src/climpred/preprocessing/mpi.py
similarity index 100%
rename from climpred/preprocessing/mpi.py
rename to src/climpred/preprocessing/mpi.py
diff --git a/climpred/preprocessing/shared.py b/src/climpred/preprocessing/shared.py
similarity index 100%
rename from climpred/preprocessing/shared.py
rename to src/climpred/preprocessing/shared.py
diff --git a/climpred/reference.py b/src/climpred/reference.py
similarity index 99%
rename from climpred/reference.py
rename to src/climpred/reference.py
index a0ce9b40c..b0cc85639 100644
--- a/climpred/reference.py
+++ b/src/climpred/reference.py
@@ -103,7 +103,9 @@ def climatology(
         init_lead["time"] = init_lead["time"].to_index().to_datetimeindex()
         init_lead = init_lead["time"]
     climatology_day = verif.groupby(f"time.{seasonality_str}").mean()
-    with warnings.catch_warnings():  # ignore numpy warning https://stackoverflow.com/questions/40659212/futurewarning-elementwise-comparison-failed-returning-scalar-but-in-the-futur#46721064 # noqa: E501
+    with (
+        warnings.catch_warnings()
+    ):  # ignore numpy warning https://stackoverflow.com/questions/40659212/futurewarning-elementwise-comparison-failed-returning-scalar-but-in-the-futur#46721064 # noqa: E501
         warnings.simplefilter(action="ignore", category=FutureWarning)
         # enlarge times to get climatology_forecast times
         # this prevents errors if verification.time and hindcast.init are too much apart
diff --git a/climpred/relative_entropy.py b/src/climpred/relative_entropy.py
similarity index 100%
rename from climpred/relative_entropy.py
rename to src/climpred/relative_entropy.py
diff --git a/climpred/smoothing.py b/src/climpred/smoothing.py
similarity index 100%
rename from climpred/smoothing.py
rename to src/climpred/smoothing.py
diff --git a/climpred/stats.py b/src/climpred/stats.py
similarity index 100%
rename from climpred/stats.py
rename to src/climpred/stats.py
diff --git a/climpred/testing.py b/src/climpred/testing.py
similarity index 100%
rename from climpred/testing.py
rename to src/climpred/testing.py
diff --git a/climpred/tests/__init__.py b/src/climpred/tests/__init__.py
similarity index 100%
rename from climpred/tests/__init__.py
rename to src/climpred/tests/__init__.py
diff --git a/climpred/tests/test_HindcastEnsemble_class.py b/src/climpred/tests/test_HindcastEnsemble_class.py
similarity index 100%
rename from climpred/tests/test_HindcastEnsemble_class.py
rename to src/climpred/tests/test_HindcastEnsemble_class.py
diff --git a/climpred/tests/test_PerfectModelEnsemble_class.py b/src/climpred/tests/test_PerfectModelEnsemble_class.py
similarity index 100%
rename from climpred/tests/test_PerfectModelEnsemble_class.py
rename to src/climpred/tests/test_PerfectModelEnsemble_class.py
diff --git a/climpred/tests/test_PredictionEnsemble.py b/src/climpred/tests/test_PredictionEnsemble.py
similarity index 100%
rename from climpred/tests/test_PredictionEnsemble.py
rename to src/climpred/tests/test_PredictionEnsemble.py
diff --git a/climpred/tests/test_alignment.py b/src/climpred/tests/test_alignment.py
similarity index 100%
rename from climpred/tests/test_alignment.py
rename to src/climpred/tests/test_alignment.py
diff --git a/climpred/tests/test_bias_removal.py b/src/climpred/tests/test_bias_removal.py
similarity index 100%
rename from climpred/tests/test_bias_removal.py
rename to src/climpred/tests/test_bias_removal.py
diff --git a/climpred/tests/test_bootstrap.py b/src/climpred/tests/test_bootstrap.py
similarity index 100%
rename from climpred/tests/test_bootstrap.py
rename to src/climpred/tests/test_bootstrap.py
diff --git a/climpred/tests/test_checks.py b/src/climpred/tests/test_checks.py
similarity index 100%
rename from climpred/tests/test_checks.py
rename to src/climpred/tests/test_checks.py
diff --git a/climpred/tests/test_comparisons.py b/src/climpred/tests/test_comparisons.py
similarity index 100%
rename from climpred/tests/test_comparisons.py
rename to src/climpred/tests/test_comparisons.py
diff --git a/climpred/tests/test_compute_dims.py b/src/climpred/tests/test_compute_dims.py
similarity index 100%
rename from climpred/tests/test_compute_dims.py
rename to src/climpred/tests/test_compute_dims.py
diff --git a/climpred/tests/test_demo_data.py b/src/climpred/tests/test_demo_data.py
similarity index 100%
rename from climpred/tests/test_demo_data.py
rename to src/climpred/tests/test_demo_data.py
diff --git a/climpred/tests/test_effective_p_value.py b/src/climpred/tests/test_effective_p_value.py
similarity index 100%
rename from climpred/tests/test_effective_p_value.py
rename to src/climpred/tests/test_effective_p_value.py
diff --git a/climpred/tests/test_graphics.py b/src/climpred/tests/test_graphics.py
similarity index 100%
rename from climpred/tests/test_graphics.py
rename to src/climpred/tests/test_graphics.py
diff --git a/climpred/tests/test_hindcast_prediction.py b/src/climpred/tests/test_hindcast_prediction.py
similarity index 100%
rename from climpred/tests/test_hindcast_prediction.py
rename to src/climpred/tests/test_hindcast_prediction.py
diff --git a/climpred/tests/test_horizon.py b/src/climpred/tests/test_horizon.py
similarity index 100%
rename from climpred/tests/test_horizon.py
rename to src/climpred/tests/test_horizon.py
diff --git a/climpred/tests/test_lead_time_resolutions.py b/src/climpred/tests/test_lead_time_resolutions.py
similarity index 100%
rename from climpred/tests/test_lead_time_resolutions.py
rename to src/climpred/tests/test_lead_time_resolutions.py
diff --git a/climpred/tests/test_logging.py b/src/climpred/tests/test_logging.py
similarity index 100%
rename from climpred/tests/test_logging.py
rename to src/climpred/tests/test_logging.py
diff --git a/climpred/tests/test_map.py b/src/climpred/tests/test_map.py
similarity index 100%
rename from climpred/tests/test_map.py
rename to src/climpred/tests/test_map.py
diff --git a/climpred/tests/test_metrics.py b/src/climpred/tests/test_metrics.py
similarity index 100%
rename from climpred/tests/test_metrics.py
rename to src/climpred/tests/test_metrics.py
diff --git a/climpred/tests/test_metrics_perfect.py b/src/climpred/tests/test_metrics_perfect.py
similarity index 100%
rename from climpred/tests/test_metrics_perfect.py
rename to src/climpred/tests/test_metrics_perfect.py
diff --git a/climpred/tests/test_options.py b/src/climpred/tests/test_options.py
similarity index 100%
rename from climpred/tests/test_options.py
rename to src/climpred/tests/test_options.py
diff --git a/climpred/tests/test_perfect_model_prediction.py b/src/climpred/tests/test_perfect_model_prediction.py
similarity index 100%
rename from climpred/tests/test_perfect_model_prediction.py
rename to src/climpred/tests/test_perfect_model_prediction.py
diff --git a/climpred/tests/test_preprocessing.py b/src/climpred/tests/test_preprocessing.py
similarity index 100%
rename from climpred/tests/test_preprocessing.py
rename to src/climpred/tests/test_preprocessing.py
diff --git a/climpred/tests/test_probabilistic.py b/src/climpred/tests/test_probabilistic.py
similarity index 100%
rename from climpred/tests/test_probabilistic.py
rename to src/climpred/tests/test_probabilistic.py
diff --git a/climpred/tests/test_reference.py b/src/climpred/tests/test_reference.py
similarity index 100%
rename from climpred/tests/test_reference.py
rename to src/climpred/tests/test_reference.py
diff --git a/climpred/tests/test_relative_entropy.py b/src/climpred/tests/test_relative_entropy.py
similarity index 100%
rename from climpred/tests/test_relative_entropy.py
rename to src/climpred/tests/test_relative_entropy.py
diff --git a/climpred/tests/test_repr.py b/src/climpred/tests/test_repr.py
similarity index 100%
rename from climpred/tests/test_repr.py
rename to src/climpred/tests/test_repr.py
diff --git a/climpred/tests/test_smoothing.py b/src/climpred/tests/test_smoothing.py
similarity index 100%
rename from climpred/tests/test_smoothing.py
rename to src/climpred/tests/test_smoothing.py
diff --git a/climpred/tests/test_stats.py b/src/climpred/tests/test_stats.py
similarity index 100%
rename from climpred/tests/test_stats.py
rename to src/climpred/tests/test_stats.py
diff --git a/climpred/tests/test_uninitialized.py b/src/climpred/tests/test_uninitialized.py
similarity index 100%
rename from climpred/tests/test_uninitialized.py
rename to src/climpred/tests/test_uninitialized.py
diff --git a/climpred/tests/test_utils.py b/src/climpred/tests/test_utils.py
similarity index 100%
rename from climpred/tests/test_utils.py
rename to src/climpred/tests/test_utils.py
diff --git a/climpred/tests/test_valid_time.py b/src/climpred/tests/test_valid_time.py
similarity index 100%
rename from climpred/tests/test_valid_time.py
rename to src/climpred/tests/test_valid_time.py
diff --git a/climpred/tests/test_versioning.py b/src/climpred/tests/test_versioning.py
similarity index 100%
rename from climpred/tests/test_versioning.py
rename to src/climpred/tests/test_versioning.py
diff --git a/climpred/tutorial.py b/src/climpred/tutorial.py
similarity index 100%
rename from climpred/tutorial.py
rename to src/climpred/tutorial.py
diff --git a/climpred/utils.py b/src/climpred/utils.py
similarity index 100%
rename from climpred/utils.py
rename to src/climpred/utils.py
diff --git a/climpred/versioning/__init__.py b/src/climpred/versioning/__init__.py
similarity index 100%
rename from climpred/versioning/__init__.py
rename to src/climpred/versioning/__init__.py
diff --git a/climpred/versioning/print_versions.py b/src/climpred/versioning/print_versions.py
similarity index 100%
rename from climpred/versioning/print_versions.py
rename to src/climpred/versioning/print_versions.py