Colors for temperatures and dual scales

[Crissov]

Figure 20.12

Nice style, but isnʼt a gradient from dark red = coldest to light yellow = warmest counter-conventional and thus to be avoided?

Also, I would use lines at increments of 32 °F and a second x-axis label for Celsius #i18n #m11n, which would preferably use vertical lines at increments of 10 °C.

[clauswilke]

Dark red = coldest to light yellow = warmest is a heat color scale and it is inspired by the colors of black body radiation: https://en.wikipedia.org/wiki/Black-body_radiation

See in particular this image: https://en.wikipedia.org/wiki/File:Pahoehoe_toe.jpg