Smartskins was a post I recently posted how you can change the look of your HTC One.
Well in the UK we have had 30℃ temperatures. Consequently, your phone is going to get hotter. Playing music and using the GPS will increase the temperature too.
Unfortunately, the black carbon skin doesn’t allow the HTC One to dissipate the heat and will therefore prevent charging until the phone is cooler.
So my advice, is don’t use this type of skin, unless you live in an igloo.