80-84 should be ok. I would be more concerned with pollution getting into your tank from your garage.
Either get and ac in the garage or a Chiller if your worried about temp.Im not worried about pollution, im more worried about keeping it cool during the summer.
In a emergency fill up a plastic soda bottle with ice water. Put a air stone or a power head underneath. Same can be done with hot water to warm a tank.I have a 24x30 garage and would love to put 2 or 3 tanks in there to watch my fish when i work on my car. Worried about the water getting to hot in the summer since the garage doesnt have a/c.