There are a lot of days in the south and all across the country, when, even though it's winter, the temperature is warm enough for bees to fly. And when it's warm enough, they will fly.
Our bees in Georgia have year round pollen sources so when it's warm enough to fly, the bees will be out, looking for camellia or whatever might be a winter-blooming plant. Every day that my bees fly, I see them flying into the hives with pollen on their legs.
The other thing they are looking for is water. This year I'm in a new house (old, but new to me!) and have set up bird feeders. I also put a bird bath on my deck railing. I see birds in it on every sunny day. Because I know that bees can't swim, I have floated two corks in the bird bath to give the bees a landing place. I'll add a few more as a few more bottles of wine are opened.
The other night on January 4, our temperatures dropped to the 20s and in the morning, my bird bath looked like Lake Michigan in the winter: