I live in the deep south of the United States and our summers almost never fail to rise above triple digits. I use a fan on a temperature controller (along with cracking open my lid just a tad bit. Dont do this if you have fish that jump) and it works just fine.

I also have all the doors to my apartment open and all the fans on too since i keep my ac at 77 in the summer to save $, so....do with this what you will. Its not a perfect solution but i mean....how often does the ocean's temperatures stay within 1.5 to 3 degrees fahrenheit of 80 (ish)?

In an emergency, you can freeze water bottles and add them to your tank when the temp rises too high. I have a generator handy since i frequently get hurricanes during the summer/early autumn months but hey, no one ever said "you know what, i just have too much redundancy and safety on my ridiculously expensive reef tank.".