Nether are way too hot. It requires about a 30 seconds to die from a hyperthermia with a jelled slime armor. If this is a feature, it's very annoying.

And also, time affects temperature too much. I live in Extreme Hills+ biome (y=141) and, if there's a day, i still getting high temperature while i in the house. All coils are disabled and torches removed.
Minecraft 1.12.2, TAN 3.0.0.68