I personally don't mind extreme cold as far as my body is concerned. However, the tires never reach operating temps when it gets close to freezing and I'm extremely careful, especially when cornering, because it feels like I'm riding on a sheet of ice. Not fun.
Years ago I rode for about 1/2 hour when the actual temp was 7*F BELOW zero as a challenge between my next door neighbor and myself. He rode, too. Nowadays my lower limit would be about 40*F, as far as motorcycle riding goes. I'll still ride down to about 15 degrees on my bicycle.
I don't ride when it's below 30, that's if I happen to have a car.
it does not snow in San Antonio so I love it as I ride everyday.
What's worst of riding in the cold was my fingurs they actually hurt in a very cold weather as if a giant door slammed on my hands, man it hurts lol, at the light I had to look at my hand to see if I'm holding the clutch or not as I couldnt feel a damn thing.
I'm in until it drops below 40 as well. Colder doesn't bother me (although heated gloves are sounding more and more appealing!), but once it get colder, I figure there's a good chance there will be salt on the road, and I don't want that crap on my bike.