These cars are not tinted so even when it is 70 degrees and sunny it can get hot in there. They do give you a sports bottle and plenty of filtered water so bring it in the car and use the door drink holder so its not in the way of your shifts. That said you are mostly only in the car for 20-30 mins at a time for exercises and if not on track just waiting for your turn so its really not that bad. As stated you do have access to AC and my car had the seat coolers. I'd say if July is best then do it but unless you are the coolest cat around who is already comfortable with high speed turns and catapulting through the esses, expect to be sweating a fair bit on the runs. Its the challenge that make it memorable and I just got home yesterday and already want to make a trip back.