Phones turn energy into heat. Charging, streaming video, navigation, gaming and restoring from a backup all make an iPhone work hard, and it is normal for the back to feel warm. Heat becomes a concern when it is constant, happens with the phone idle, or comes with other symptoms.
Common, harmless causes
- Fast charging, especially with a thick case on
- Setting up a new phone or restoring a large backup
- Weak mobile signal, which makes the phone search harder
- Leaving the phone in direct sun or in a car
How to cool it down safely
Take the case off, move the phone out of the sun and stop charging for a while. Do not put it in a fridge or freezer: sudden cold can cause condensation inside. If the phone shows a temperature warning, let it cool before using it again.
When heat points to a fault
- The phone is hot while sitting idle with the screen off
- Battery percentage drops quickly at the same time
- The screen or back looks raised, which can mean a swelling battery
- Heat is concentrated in one spot near the charging port
Any of these is worth a free diagnostic. A worn or swelling battery should be replaced promptly, and a short on the logic board needs specialist attention before it causes more damage.
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