During the late season muzz and bow we usually get some really cold days. Normally the morning hunts are all but a waste of time until around 9:00 when the sun gets high. I've had the best activity starting around 1:00 and then going until about 4:00. They don't seem to want to hang around right until dark as much when it is that cold. There is usually very good movement though when it gets real cold. Food sources are the key.