We live in Bermuda and it very rarely drops below 70 (even 75), even in winter. We have our Betta in a 5-gallon tank with filtration and water tested this morning was 'perfect' according to our local aquarium shop (the owner is a really good friend and KNOWS her aquarium chemistry!)
Anyway, thanks to the cold front in the North east, we've got some major wind going on and, as a result, the temperature has dropped suddenly. When I came home, I realized that the tank temperature had dropped, although only slightly. Because it is so normally so warm here, we don't have a heater for our tank. I have wrapped it in some towels to serve as insulation, the tank has a lid, and there is a lamp on the tank as well.
Any suggestions about what else I can do? I will imagine that the air temperature will be back to normal in a day or so. And no, we don't have a heater in our house (central or space).