diff --git a/Marlin/src/HAL/AVR/HAL.h b/Marlin/src/HAL/AVR/HAL.h
index e825b4def3af..c7454a523477 100644
--- a/Marlin/src/HAL/AVR/HAL.h
+++ b/Marlin/src/HAL/AVR/HAL.h
@@ -229,7 +229,7 @@ class MarlinHAL {
     SBI(DIDR0, ch);
   }
 
-  // Begin ADC sampling on the given channel
+  // Begin ADC sampling on the given channel. Called from Temperature::isr!
   static void adc_start(const uint8_t ch) {
     #ifdef MUX5
       ADCSRB = ch > 7 ? _BV(MUX5) : 0;
diff --git a/Marlin/src/HAL/DUE/HAL.h b/Marlin/src/HAL/DUE/HAL.h
index 9a02c9a0dcf5..d00c4d3da102 100644
--- a/Marlin/src/HAL/DUE/HAL.h
+++ b/Marlin/src/HAL/DUE/HAL.h
@@ -209,7 +209,7 @@ class MarlinHAL {
   // Called by Temperature::init for each sensor at startup
   static void adc_enable(const uint8_t ch) {}
 
-  // Begin ADC sampling on the given channel
+  // Begin ADC sampling on the given channel. Called from Temperature::isr!
   static void adc_start(const uint8_t ch) { adc_result = analogRead(ch); }
 
   // Is the ADC ready for reading?
diff --git a/Marlin/src/HAL/ESP32/HAL.cpp b/Marlin/src/HAL/ESP32/HAL.cpp
index e204e0b6fe2b..767f65d341bc 100644
--- a/Marlin/src/HAL/ESP32/HAL.cpp
+++ b/Marlin/src/HAL/ESP32/HAL.cpp
@@ -244,7 +244,8 @@ void MarlinHAL::adc_start(const pin_t pin) {
   const adc1_channel_t chan = get_channel(pin);
   uint32_t mv;
   esp_adc_cal_get_voltage((adc_channel_t)chan, &characteristics[attenuations[chan]], &mv);
-  adc_result = mv * 1023.0f / float(ADC_REFERENCE_VOLTAGE) / 1000.0f;
+
+  adc_result = mv * isr_float_t(1023) / isr_float_t(ADC_REFERENCE_VOLTAGE) / isr_float_t(1000);
 
   // Change the attenuation level based on the new reading
   adc_atten_t atten;
diff --git a/Marlin/src/HAL/ESP32/HAL.h b/Marlin/src/HAL/ESP32/HAL.h
index 8b26c3471d39..f7e4383a85f4 100644
--- a/Marlin/src/HAL/ESP32/HAL.h
+++ b/Marlin/src/HAL/ESP32/HAL.h
@@ -74,6 +74,7 @@
 // Types
 // ------------------------
 
+typedef double isr_float_t;   // FPU ops are used for single-precision, so use double for ISRs.
 typedef int16_t pin_t;
 
 class Servo;
@@ -205,7 +206,7 @@ class MarlinHAL {
   // Called by Temperature::init for each sensor at startup
   static void adc_enable(const pin_t pin) {}
 
-  // Begin ADC sampling on the given channel
+  // Begin ADC sampling on the given pin. Called from Temperature::isr!
   static void adc_start(const pin_t pin);
 
   // Is the ADC ready for reading?
diff --git a/Marlin/src/HAL/LPC1768/HAL.h b/Marlin/src/HAL/LPC1768/HAL.h
index eefacae99549..0f26509129d5 100644
--- a/Marlin/src/HAL/LPC1768/HAL.h
+++ b/Marlin/src/HAL/LPC1768/HAL.h
@@ -234,7 +234,7 @@ class MarlinHAL {
     FilteredADC::enable_channel(pin);
   }
 
-  // Begin ADC sampling on the given pin
+  // Begin ADC sampling on the given pin. Called from Temperature::isr!
   static uint32_t adc_result;
   static void adc_start(const pin_t pin) {
     adc_result = FilteredADC::read(pin) >> (16 - HAL_ADC_RESOLUTION); // returns 16bit value, reduce to required bits
diff --git a/Marlin/src/HAL/NATIVE_SIM/HAL.h b/Marlin/src/HAL/NATIVE_SIM/HAL.h
index ee2e31fc7fa4..49a5b6ea560b 100644
--- a/Marlin/src/HAL/NATIVE_SIM/HAL.h
+++ b/Marlin/src/HAL/NATIVE_SIM/HAL.h
@@ -242,7 +242,7 @@ class MarlinHAL {
   // Called by Temperature::init for each sensor at startup
   static void adc_enable(const uint8_t ch);
 
-  // Begin ADC sampling on the given channel
+  // Begin ADC sampling on the given channel. Called from Temperature::isr!
   static void adc_start(const uint8_t ch);
 
   // Is the ADC ready for reading?
diff --git a/Marlin/src/HAL/SAMD51/HAL.h b/Marlin/src/HAL/SAMD51/HAL.h
index 3b09a885a53b..abcc28098776 100644
--- a/Marlin/src/HAL/SAMD51/HAL.h
+++ b/Marlin/src/HAL/SAMD51/HAL.h
@@ -190,7 +190,7 @@ class MarlinHAL {
   // Called by Temperature::init for each sensor at startup
   static void adc_enable(const uint8_t ch) {}
 
-  // Begin ADC sampling on the given channel
+  // Begin ADC sampling on the given pin. Called from Temperature::isr!
   static void adc_start(const pin_t pin);
 
   // Is the ADC ready for reading?
diff --git a/Marlin/src/HAL/STM32/HAL.h b/Marlin/src/HAL/STM32/HAL.h
index f5e8c1187da7..d88342b889b5 100644
--- a/Marlin/src/HAL/STM32/HAL.h
+++ b/Marlin/src/HAL/STM32/HAL.h
@@ -127,6 +127,8 @@
 // Types
 // ------------------------
 
+typedef double isr_float_t;   // FPU ops are used for single-precision, so use double for ISRs.
+
 #ifdef STM32G0B1xx
   typedef int32_t pin_t;
 #else
@@ -241,7 +243,7 @@ class MarlinHAL {
   // Called by Temperature::init for each sensor at startup
   static void adc_enable(const pin_t pin) { pinMode(pin, INPUT); }
 
-  // Begin ADC sampling on the given channel
+  // Begin ADC sampling on the given pin. Called from Temperature::isr!
   static void adc_start(const pin_t pin) { adc_result = analogRead(pin); }
 
   // Is the ADC ready for reading?
diff --git a/Marlin/src/HAL/STM32F1/HAL.h b/Marlin/src/HAL/STM32F1/HAL.h
index ceb17b48848b..a42dd89b8d27 100644
--- a/Marlin/src/HAL/STM32F1/HAL.h
+++ b/Marlin/src/HAL/STM32F1/HAL.h
@@ -280,7 +280,7 @@ class MarlinHAL {
   // Called by Temperature::init for each sensor at startup
   static void adc_enable(const pin_t pin) { pinMode(pin, INPUT_ANALOG); }
 
-  // Begin ADC sampling on the given channel
+  // Begin ADC sampling on the given pin. Called from Temperature::isr!
   static void adc_start(const pin_t pin);
 
   // Is the ADC ready for reading?
diff --git a/Marlin/src/HAL/TEENSY31_32/HAL.h b/Marlin/src/HAL/TEENSY31_32/HAL.h
index 50c0f411cf92..dc0d2d3fa939 100644
--- a/Marlin/src/HAL/TEENSY31_32/HAL.h
+++ b/Marlin/src/HAL/TEENSY31_32/HAL.h
@@ -166,7 +166,7 @@ class MarlinHAL {
   // Called by Temperature::init for each sensor at startup
   static void adc_enable(const pin_t ch) {}
 
-  // Begin ADC sampling on the given channel
+  // Begin ADC sampling on the given channel. Called from Temperature::isr!
   static void adc_start(const pin_t ch);
 
   // Is the ADC ready for reading?
diff --git a/Marlin/src/HAL/TEENSY35_36/HAL.h b/Marlin/src/HAL/TEENSY35_36/HAL.h
index e4c57f8d1e10..c45f2aa49307 100644
--- a/Marlin/src/HAL/TEENSY35_36/HAL.h
+++ b/Marlin/src/HAL/TEENSY35_36/HAL.h
@@ -173,7 +173,7 @@ class MarlinHAL {
   // Called by Temperature::init for each sensor at startup
   static void adc_enable(const pin_t) {}
 
-  // Begin ADC sampling on the given channel
+  // Begin ADC sampling on the given pin. Called from Temperature::isr!
   static void adc_start(const pin_t pin);
 
   // Is the ADC ready for reading?
diff --git a/Marlin/src/HAL/TEENSY40_41/HAL.h b/Marlin/src/HAL/TEENSY40_41/HAL.h
index a21e65285409..ea874da2faea 100644
--- a/Marlin/src/HAL/TEENSY40_41/HAL.h
+++ b/Marlin/src/HAL/TEENSY40_41/HAL.h
@@ -195,7 +195,7 @@ class MarlinHAL {
   // Called by Temperature::init for each sensor at startup
   static void adc_enable(const pin_t pin) {}
 
-  // Begin ADC sampling on the given channel
+  // Begin ADC sampling on the given pin. Called from Temperature::isr!
   static void adc_start(const pin_t pin);
 
   // Is the ADC ready for reading?
diff --git a/Marlin/src/lcd/e3v2/marlinui/ui_status_480x272.cpp b/Marlin/src/lcd/e3v2/marlinui/ui_status_480x272.cpp
index 2a4909d921b6..ba6814a57a10 100644
--- a/Marlin/src/lcd/e3v2/marlinui/ui_status_480x272.cpp
+++ b/Marlin/src/lcd/e3v2/marlinui/ui_status_480x272.cpp
@@ -196,13 +196,13 @@ FORCE_INLINE void _draw_heater_status(const heater_id_t heater, const uint16_t x
     #else
       #define HOTEND_STATS 1
     #endif
-    static celsius_t old_temp[HOTEND_STATS] = ARRAY_N_1(HOTEND_STATS, 500),
-                   old_target[HOTEND_STATS] = ARRAY_N_1(HOTEND_STATS, 500);
-    static bool old_on[HOTEND_STATS] = ARRAY_N_1(HOTEND_STATS, false);
+    static celsius_t old_temp[HOTEND_STATS] = { 0 },
+                   old_target[HOTEND_STATS] = { 0 };
+    static bool old_on[HOTEND_STATS] = { false };
   #endif
 
   #if HAS_HEATED_BED
-    static celsius_t old_bed_temp = 500, old_bed_target = 500;
+    static celsius_t old_bed_temp = 0, old_bed_target = 0;
     static bool old_bed_on = false;
     #if HAS_LEVELING
       static bool old_leveling_on = false;