Tommy has it right - however problem is with the pump which doesn't like handling fuel that's too hot - answer is to have your tank as full as possible in really hot weather to act as a decent heat sink and also a fuel cooler (similar to
oil cooler) on the fuel drain-back side well away from the engine compartment and possibly a new fuel pump if the other two don't cure the problem. Insulating the fuel lines in the engine compartment will help as well.