I would also think that if you can keep the water airated with battery bubblers you should be OK. Heaven knows you don't need a heater today. As long as the water doesn't get O2 depleted the fish should be OK.
Corals may be a bit stressed due to lack of light, but then again, in the ocean there are stormy days where there isn't much light, so I wouldn't think a day or two without light would really be that much of a problem.
Assuming you keep the water circulating, I would think the only concerns would be low PH, and possible elevated temps due to the hot weather.
PH down probally wouldn't be much of an issue for the fish, and for a short time I would think most corals would be fine also. As for elevated temps (and the likelyhood of a prolonged outage) I wouldn't worry as last I heard tommorow is supposed to be MUCH cooler.
Edit: "Lord knows I dont have to worry about heaters" Yea!
Hang in there and get extra batteries just in case (assuming you do have battery bubblers, if not, just get some)