Avoid Extreme Temperatures
Extreme temperatures can damage your battery life permanently. The ideal ambient temperature for any Apple device is between 62° to 72° F (16° to 22° C).
If you’re charging your device at a very high temperature, higher than 95° F (35° C), your device will limit the charge to 80%. More than that will damage your battery permanently, so avoid charging it at all costs at such high temperatures.
Using your iPhone or any other Apple device at a low temperature can decrease your battery life faster than usual, but it should perform normally once the temperature goes up.