I've noticed that every time the weather gets hot my bedroom light stops working and I'd like to figure out why that happens.
It sounds like a bad / loose electrical connection. Heat causes copper and aluminum to expand (copper and aluminum are two common conductors). Get an electrician to make sure the wiring connections to the fixture are tight.
Along the same line, it is a bad practice to mix copper and aluminum wire and terminations. These two metals expand at different rates when heated and this could cause a loose connection. I prefer using only copper.
Could it be possible that you are using an air conditioner during hot weather and that draws power away from your lighting? I had a friend once who could either run his air conditioner in his room or watch TV... but not both.