[st.patrik]

I guess I had always seen cold +3 provinces as places where it's always winter - places where it's about as cold as can be - all the time. I guess it might make sense for such a place to be a *little* bit warmer in summer, but pretty much as cold as it gets the rest of the year.

So your idea isn't bad - but I don't think seasonal change is enough of a factor to change the scales. Think about really really cold places on earth, where maybe it gets a bit warmer during the summer months, but not significantly so - pretty much its just always cold. Similarly with very hot places - seasonal variation is nowhere near as pronounced as in temperate regions.