I live in Arizona, it still gets up to the 90s so we are still playing. Of course we play in the mornings or evenings to avoid the heat. I Feel bad for all you yanks covered in snow and locked inside. You should plan a trip down south where the snow doesn't last and the disc golf doesn't stop.
It is under 20 degrees here and we still play, not as often as we do during the summer. That isn't because of the temp though, we lose TONS of daylight here, so unless you get off way early (well before 5pm) you're playing in the dark. During the peak of the winter (Dec 21), we'll be at just under 5 hrs of daylight. We go to work when it is dark and we get off work when it is dark. The only other time is during the weekend. Outside of that, I just putt.