If they are the fish in your sig, the temp shouldn't bother them unless it starts to get below 72F. It may start to affect the platys, cats do ok in cooler water.
If it looks like a long, more than a couple hours, without power, you could wrap the tank with a blanket to conserve heat. If it starts to drop severely, fill some clean water bottles with warm water from the tap, cap them & float them in the tank.
For the filter, as long as the media is wet it should be fine for a couple hours. If it's out longer than that, float the media in the tank.
To insure proper aeration of the water, take a large clean (no soap residue!) container or cup, & pour some of the water from the tank into the tank.
Tolak