Mine wear their overcoats (cold weather gear) even if the thermostat is set on warm. I have to manually put them into their casuals. But I haven't seen anyone get cold on community lots though but I haven't had my Sims travel to many of them since winter rolled through. For instance, I took one of my Sims on the talent show case at winter time and it was snowing. Everyone was in their finest (formal wear). I didn't notice a thermostat though. Could have been present as Get Famous comes after Seasons?