One of the things that hot weather can have a toll on is the battery under your cars hood.
During the summer heat the battery gets much hotter in addition to the heat coming off the engine.
The hot temperatures can corrode a battery on the inside which could lead to a dead battery.
Hot summer temperatures also make it harder for your vehicle coolant system to cool the engine properly so it's possible that your cars engine could overheat during the hot weather so be sure to keep the coolant system checked out and be sure your engines coolant is topped off and not low.
Also check your vehicles radiator hoses and heater hoses to be sure they're in good shape.