Here is a screenshot of what wintermod will do for snowcover:
For now (I'm still pretty desperate for ideas) it just puts snowcover where it belongs, with no transitional climates.
There are 4 turns (Weeks) per Month, and 12 months in a year.
Snowcover changes ever 1&1/2 Months (6 turns). So summer, summer/fall, fall, fall/winter, winter, and then backwards.
Ice (not shown, already done) changes ever 3 months (12 turns)(summer, fall, winter, fall, etc).
In the screenshot, a lighter colour means snow cover close to the summer (ie areas that are snow-covered pretty much year-round) and reds are areas that are snow-covered only in winter.
Snow will currently give 1 food, to balance things out.
Units will also suffer penalties on snow. There will be a promotion for units of northern civs to disregard this.
Additionally, I was wrong about the performance. It takes 5 1/2 seconds to process ice changes. I do not know how long changing the snowcover will take (will update next post). To increase performance, I had an idea- make my sim-years longer, so that the changes happen less often.
Resource work still to come- this is definitely the harder part so I am getting it over with.
EDIT: Ignore the graphic glith in Africa! I accidentally changed the colour of those tiles with one of the macros.
EDIT: Also in the summer and summer/spring and summer/fall, there will be some snowcover in the southern mountain ranges of South America
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Also, summermod looks like it will be removed. Even though tropical regions do have a distinct seasonal pattern, unlike with wintermod, it would balance out, meaning it essentially has no effect and would just slow the game down.