Yeah- I hear you on the colder weather! Brrrr.....

If you have a stand alone tub, it will probably need temp regulation on the hot and cool side. However, if you have the tub in an enclosed rack system (RBI's for example) then just some flex watt on one end will do the trick.

Here in Bend we've already had freezing (and below) night temps and my racks are all doing fine with the aforementioned set-up.