Warm temperatures, on the contrary, make us want to go outside and explore, and we all know that close interaction with nature makes us kind, caring, and loving. And while it might be true, it doesn’t explain Canadians, for example. They live in lower temperatures than most Americans and Chinese do, but yet they score better on the personality test.
In fact, Canada is considered to be one of the happiest countries to live in. But I think the government contributes just as much to form a positive environment as the people who live there do. So I guess climate zone you grew up in might not be that important after all.