[JimMorrison]

I belong to the camp that doesn't believe in seasonal variation. I mean, I have seen temperature fluctuations sure, but in my experience they are far too subtle to be a factor in a strategy. It's not as if all provinces are +1 Heat in summer and +1 Cold in winter, in fact it's far from that.

For me, one of the major deciding factors is the fact that the other temperature is so extremely debilitating to you, that you want to push in your direction as hard as possible, to insure more favorable conditions. The other being that your dominion hampers most other nations more than the excess temp scale hampers you. There is nothing "free" about a -5% income in your capital from turn 1 through the entirety of the game, that's for sure. And the longer the game goes, the more of your territory will have the extra scale, and thus be generating less income. It just happens that the tradeoff is worth it, you give your neighbors a large penalty, and you suffer a smaller penalty yourself.