If you are talking about using it inside the patio to stop it freezing, why not?.
If you are talking about using it to melt the snow once it has settled, if it is an electric one, you may have have a safety problem with the damp. "Out in the back of the garage with a plastic hat", it may not be safe to use without:-
(1) bringing it indoors for a few days to dry out'
(2) have it checked by a competant person for safety.