I get pretty significant SAD and 5000 IUs of Vitamin D helps a lot, but it's not enough for me. I'm planning to move to somewhere else in a year or two, maybe Seattle.
You want sunny days per year. Which Seattle gets less than 90. Most cities in California get over 200.
Last year was unusually warm and sunny in the summer as too, though I guess a couple years isn't really a climate change, it's just unusual weather.
On the flip side, people that got along without air conditioners 5 or 10 years ago are revisiting that decision, I called around a few places to get a quote for a split unit to be installed, and they were booked up through August.
Not to mention the week of smoke we've had the last 2 summers. ;)
The May-August period has very few clouds and a not-too-hot sun, so that is a fine season from the point of view of spending time outdoors and letting your skin work for your body.
Winnipeg might be much sunnier in the winter, but I'm not sure you'd get much more sun exposure given things like wind chill.
BTW, where on VI are you? Quadra here.
Was a great choice for me.