Unless the ambient temperature of your room is below 65, don't worry about heat and unplug the UTH until you can get a thermostat or at least a rheostat to control it. If it is going to be longer than a day or so then raise the temps in your house to at least 72 and get something as soon as you can. You can go a easily go a couple days in the 70s without risk of an RI, but unregulated UTH, you can't go 10 minutes without the risk of a serious burn.