@drdrang for the color range, my personal guess is that it is meant to reflect the overall temperature of the day, as experienced by a person mostly up during daylight.

You can ignore temperatures during the night because you won’t leave the house before 7-8am.
In your example, the day ranging from 71-87 will probably be experienced as 80-87. While the day ranging 59-80 will probably be experienced as 70-80. So little to no overlap. This way the overall color of the color gradient reflects at a glance how the day will feal.

With an accurate gradient, a chill night and a huge temp span, most of the gradient would be blue, even if the day could feel hot.