Temperature during day and night should be different. Nights are colder, days are warmer. When measuring temperature shouldn't you measure it whether that tile has some shade or none? Example, a tree has a shade on its nearby tiles, this making it a good sleeping spot on early game when you don't have coolers during heatwaves.
Also, change the slept outside buff. Maybe it should be slept without roof. And add a trait outside lover who wants to sleep without any roof.
Just my suggestions. Don't kill me.
There actually is day/night cycle temperature difference in game. Different maps, it is more apparent. The temp when shade/under roof vs open... That is a bit different. In small size, the air temps would be the same abouts but one feels warmer. The shadow temperature difference usually needs a massive effect to cause variation in ambient temp.
I agree that would be fun to get an outdoors lover trait.
The effect of sun is not simulated. Not only nights are barely colder than days. Outdoors areas with rock roof are just as warm as those without roof.