I currently have my grain in air tight containers that I store inside. I would like to move them out to the garage which gets very hot. (100 degree summer days are common).
Will the heat negatively effect the storage of the grain?
Grain, and foodstuffs in general should be stored in a cool, dry area, since the warm temperature can increase the rate of staling. It depends upon how long the grain will be around for. If you can use it up within 6 months then I doubt you would notice much change, especially if it's stored in a sealed container.