I live in Georgia and I am having a similar problem. When it's hot (> 90) and sunny the car will not start in the afternoon. Everything works, lights, AC blower, radio,... except the engine does not turn over and I don't hear the solenoid noise. If I leave the door open for a few seconds it will start. The battery and alternator have been replaced by the dealership and they kept the car for several days and couldn't recreate the problem - that was during a cool spell and I didn't recognize the internal heat issue then.
Have you had any luck resolving your issue?