keep in mind thats air temp.. which means that is in the shade.. surface temps will be about 130-160 depending on what surface (grass vs pavement)
104 in the daytime.. 58 overnight.. thats a 40+ change in temp... my heaters run overnight and fans blow over the tank all day...
however there are 2 tanks i dont run heaters in... 1 is the 60gallon "pond" tank in the backyard which has tons of surface plants and an air pump that runs from 9am-8pm.. the other is the 25gallon shrimp tank in the livingroom.. it stays about 80 durring the summer about 65 in the winter.. the shrimp are a LOT slower in the winter..
I've taken all of the heaters out of my tanks . . . living in south Florida, our home is generally in the high 70s anyway, usually I am more concerned with not letting the tanks get too hot . . .