A friend asked me this question at dinner Saturday night. My answer was: It depends. Like some others on this thread, I use a matrix of temperature, wind and precipitation. With fair skies and wind under 20–25 mph, the temps can go down into the 30s and I'll play. Cold rain, sleet or snow and wind? That's a no-go. I'm a walker and self-propulsion, combined with proper layering, helps keep me warm here in southeastern Virginia.
Mike T.