I live in Arizona, walking out in the sun going from class to class, my phone will literally burn my hands. But the reason for that is the screen, I could be using facebook and that's it and it burns up. Reason being is because there are numorous heat sorces (battery,screen,radios,charging) and with no heat sink. The product is compact the, Motorola made the thinnest smartphone, I don't care about the heat because its going to happen we use it all the time. When I used rooted android tethering I got it up to 137F.!( says battery widget).
And just a rule of thumb. Put it in your hands curl it up with them, your hands will be the fastest"heat sink " around besides a fridge. If your going to be outside all day trying to watch a movie dim the screen, find cover. And don't complain you have one of the fastest phones on the market to date, with the best brand for android out there. We are all faster than iPhones hands down!! Be proud! Ha