[guybrush threepwood]

Originally posted by Graeme Dice:
The spells have nothing to do with each other. Second sun increases the heat scale in all provinces in the world. Utterdark reduces income, causes unrest, causes shade attacks in enemy provinces, and makes every battle fought under the effects of the darkness spell.

Technically, yes.

But fluff-wise, it seems weird. If they for instance were to cancel the effect of each other, then that would certainly be yet another nice small detail.