Depends on what the high temp is going to be for the day or what it'll be like later in the ride. If it's 30 at the start and only going to go up 5 or so degrees for the whole day, then no, I have no problem skipping the group ride, but if it's going to get above 40 45 or more then I'll probably do it. My general rule is 40 degrees or higher, then I'll ride.
Benjamin