We live in SoCal and used to warmer temps.
So I might sound pretty whimpy when I say we don't like to ride when it gets below 50, I don't see how 20 is even possible.
When it is dark and cold then my wife really doesn't want to ride. Somehow its not as bad when it is 50 and sunny compared to riding at night.
This weekend its supposed to be 90 on the coast so we will starting early before 8am. We are a long way from snow or ice. I used to enjoy skating at indoor ice rinks as a kid. We used to ski both downhill and XC but it has become too expensive and its a long drive to the nearest ski area so at most we would ski a couple weeks a year.