I think people in warmer climates are generally happier. Well not like middle east kind of warm... that's way too hot. Probably the reason why they're pissed and want you all dead.
Probably all burns down to Vitamin D levels.
30 minutes in European winter sun, with only arms and face exposed lets your body produce 10.000 i.u. of Vitamin D, and the European Union's recommendation for daily intake is 2000 i.u.
