No. All breeds of squirrels are active during the daytime rather than the overnight hours. There are some breeds of squirrels that only roam at dawn and there are others that are most active around sunset. Most tree squirrels are active at both sunrise and sunset rather than during the warmer hours of the day or overnight hours. Squirrels fall prey to many nocturnal predators, so if you see a squirrel out at night, it's probably running from something that's trying to eat it.