The temperature now falls down when you are riding a boat, the faster you go the lower the temperature, so I assume it is the feature, but I can't find it in the changelogs. So on Sakhal it nerfs the early boat finding and going straight for the crashed ship.
However for some reson the temperature reduction effects you even if you have a heat buff (Had 3 pluses and still got to dark blue) and even with best insulation clothes it goes to dark blue (or even blinking) when you are goning full speed in Sakhal.
Heatbuff itsef is not getteing effected (you dont loose it faster same as if you go in the water when it just dissapears in couple of seconds).

Give yourself a heat buff
Hop on boat in Sakhal
Give it a ride
Freeze to death i guess =D

I think the temperature decrease while on boat is a good feature, though it shouldn't be that brutal when you have collected decent gear
And also effecting your character when having a heat buff, is just weird