Some things to remember about the iPhone:
Operate it a place where the temperature is between 0º and 35º C (32º to 95º F). Low- or high-temperature conditions might temporarily shorten battery life or cause the device to temporarily stop working properly.
Store the device in a place where the temperature is between -20º and 45º C (-4º to 113º F). Don’t leave the device in your car, because temperatures in parked cars can exceed this range.
When using the device or charging the battery, it is normal for it to get warm. The exterior of the device functions as a cooling surface that transfers heat from inside the device to the cooler air outside.
Some conditions and activities that may activate the Temperature warning message:
1. Leaving the device in a car on a hot day.
2. Leaving it in direct sunlight for extended amounts of time.
3. Using certain features in hot conditions or direct sunlight for long periods of time, such as GPS tracking in a car on a sunny day or listening to music while in direct sunlight.
If you are in compliance with everything I've said... and your phone still has issues, it will need to be examined first hand by Apple.
I hope I have been of assistance. Please let me know if there's anything else I can do for you... and thanks again for using JustAnswer!There is no need to reply unless you have additional questions. Doing so will only generate a request for me to reply to your post.Regards,Dan