Where can I store supplies?

Does the garage have vented eaves and a peak vent?  I would say 100 is tolerable but not much over that.

Yes it's is safe. I have been doing that for the past 30 years or so. If you buy your thinners in bulk like hardware store gallon cans, store it as far as possible from any possible ignition sources for fumes such as water heaters or other appliances with a pilot light, and near some sort of vent. Glues and paints of the size that you get from the hobby shop you don't have to worry about so much as long as you seal them all up properly at the end of each bench session. 

Like Stick said, I have 30 year old paints that are still good and they have gone through 100+ and -0 temps. It's opening them constantly exposing them to air that eventually kills them.