Frost would be a bummer. But can you cut the temperature way back?
(cut back in stages a few degrees each day. I think there are
potentailly three problems with growing cooler (above freezing of
course) - 1.inciting some mildew, 2. blossom pollination may fail
(everybody knows hot tomatos like hot sex) ), 3. takes longer for the
fruit to ripen.

Bob in sunny soCal