Phone is stuck in emergency/'temperature too hot' mode... how do I fix?

I left my phone in the car for about 45 minutes two mornings ago like I do every morning. (I'm in the army and have morning PT) Anyway, it was about 60 degrees outside and not humid or anything. I returned to my car and found that it wasnt responsive and would not turn on. After half a day, I got it to restart, but the main screen says "Iphone needs to cool down before you can use it." It has now been two days and several visits to my air conditioning... I dont know what else to do... It won't stay visible on my computer long enough to restore it.