Fall is the best season. It never lasts long enough. I get sick of summer after a while. Fall is too sporadic here. If it would just stay at 60 degrees for a few weeks I'd be happy. But it's 70 for a few days, and then 45, then back up.
I think seasonal depression is sort of made up. It has to with the days getting shorter. Since your body normally equates darkness with going to bed, you get a little sleepy earlier in the evening, and people equate the sluggishness with depression. Plus there's generally less to do during the winter, so boredom contributes too.
If someone is from California, or Arizona, or any other hot states, or countries then I doubt you will get depressed during winter, cos its probably still quite hot. But North-Western Europeans countries have shit, rainy, cold weather and its a bummer.
No, it's not always hot here in Tucson, Arizona. We get down around freezing on some nights in the winter, and we have cold, wet and rainy times, and just regular old cold winter temps (you know, 40F-60F). But I think this depression thing is tied more to the sun than to the temperature. Maybe I am wrong. But we have close to 365 days of sunshine here in Tucson. That is, days where the sun becomes visible at some point during the day. And probably 250-300 of them are mostly sunny.