Dangerous Temperatures is a small mod that add dangers to heat an cold.
If you happen to pass by a desert it might be the case that you catch on fire.
If you happen to visit a snowy biome or similar you might start to freeze.
You can get used to some temperatures meaning you will not be affected by that bias, so if you spent a long time in color biomes, you can be there without problem, just dont visit hot biomes, the same goes switched around.
The base temperatur is based off the biome, the light and height you are on shifts it and if it rains it also puts it down some degrees.