Speaking of storing explosive materials in your garage, here's a funny story!
So there was this guy.. he liked the methamphetamines. He wanted to manufacture some and got ahold of something like a pound of Red Phosphorus (a chemical used in the manufacture of meth). For some reason or other he decided the place to store this was in the rafters of his garage.
Well. This poor dope-cook-to-be had a really bad day one hot week in summer.
As it turns out Red Phosphorus will change into White Phosphorus spontaneously when exposed to air and heat. White phosphorus is kinda neat because it combusts upon being exposed to air. Red phosphorus burns very hot and bright when exposed to flame.
So! Of course... some of his RP converts into WP, lights itself on fire.. which then lights the uncoverted RP on fire.. which is kinda like lighting a pound of gunpowder in the sense that it doesnt so much explode as it burns very very well.
So. His house burnt down. Then he was arrested on conspiracy to manufacture charges. Talk about your bad days.
So.. this post was random and off topic.. but it went well with the whole explsoves in the garage thing. Keep your chemicals in cool dark places generally. That's really your safest bet.