Remove the iPhone from direct sunlight
Stop using power-intensive apps
Close background apps
Turn off the camera, games, and navigation apps
Lower screen brightness
Turn on Airplane Mode if you do not need connectivity
Turn off Bluetooth, Wi-Fi, and cellular data if not needed
Remove the case
Move the iPhone to a cooler, shaded place
Let it rest without charging
Use a fan or cool airflow nearby
Wait until it returns to a normal temperature before using it again