What kind of terrain -> weather relations are you thinking of?

It first calculates a general reference data for whole year, which is then modified by latitude - the norhter you go, the colder it gets. So, at this level the location affects the weather. More spesific relations could be possible to program, although my first goal is just to make a fully functional basic version first. So, if you have some good ideas I'd be interested to hear - they might then get implemented later on, depending on how the development goes.

(After the weather engine I got two or three other programming tasks waiting to be done...)