Hot take: I don't think Celsius is a great temperature scale for weather.
It's fantastic for scientific purposes, but for weather the ranges are weird. 0 is cold, yes, that makes sense. 30 is extremely hot? Hmm. Don't like that.
Honestly it's entirely subjective, but I would love to see a temperature scale where 100 is "hot" for a human scale w.r.t. the weather.
So an adjusted temperature scale:
0 = freezing point of water. It's a very cold temperature that is not unreasonable to hit in the real world. It's a pretty good reference "cold".
100 = "average" human body/skin temperature. Above this, the air is definitely going to be heating you up, not cooling you down. This is colloquially defined at, what, 98 F?
This feels like a reasonable compromise to me. Lock "hot" and "cold" to known "hot" and "cold" points you might reasonably expect in weather, scaled on 0-100 so it's a nice spread of numbers.