Ya got me wondering there Emy.I just looked at mine it's about 72F. but I rarely check it except for winter time.My turtles all are in my partialy finished basement with no heat yet.I'ld guess that the air temp in winter down there is probally around 68F.I don't use a water heater in my spotty enclosure at all. With that *average* air temp plus the 3 bulbs I have on over the tank (basking temp 85-90)and water depth not going over 6 inches,The water couldn;t possibly get very cold.I'ld guess it's always low to mid 70's.