Why can't I beat Hypothermia?

I cannot beat Hypothermia when I begin a new rimworld. Every(!) game I start, even in the dessert, my colonists immediately suffer from Hypothermia.
Group hugging around campfires doesn’t work, the hypothermia goes up and up and up. Temperature at this spot is 28°C.

So, what’s the trick beating hypothermia early in game, when it doesn’t appear random anymore and even kills the settlers standing at a fireplace?

Two of them are wearing Hyperthread winter cloaks, that are supposed to keep them warm and dry
Difficulty is level 2, storyteller is Chillax