Seasonal Affective Disorder. You can read the full Wikipedia article if you’d like: https://en.wikipedia.org/wiki/Seasonal_affective_disorder In short, some people get depressed in the winter time when there’s a lot less light. As you’ve probably guessed it’s not much of an issue in Florida and a real problem in Alaska.
Here in New Hampshire we are more like Alaska than Florida. Our winter days are short and dark.
To treat it you can get outside as much as possible and get what natural light exposure there is. It’s also treated with artificial light sources such as a light box.
Personally I don’t SAD, which is real depression. However, those dark days do make me a little sad. I’ve found good bright full spectrum lights really help.
What brought this to my attention recently was the purchase of new light bulbs for the kitchen. I went too cheap when I bought replacements. The cheap Walmart bulbs aren’t going to cut it. They appear weaker than their stated lumens and the spectrum is just weird. They made me feel crappy right after I installed them. No way would they get me through the winter. Next time I’m in town I’m going to upgrade to decent bulbs. It’s way cheaper than psychotherapy.