Don’t Expose Your iPhone to High Heat
Extreme temperatures or prolonged exposure to heat can have lasting effects on your Apple handset — so it’s smart to be cautious.
Apple itself notes that low or high-temperature conditions could cause your iPhone to “change its behavior.” Its recommended ambient temperature for iOS device usage is between 0º and 35º C (32º to 95º F). Of course, it can become much hotter than that upper range in many parts of the world, or in enclosed spaces like the interior of a vehicle.
In the long term, this could result in damaged batteries. Apple says in a support document that “using an iOS device in very hot conditions can permanently shorten battery life.”
Heat can wreak havoc on lithium-ion batteries, causing a variety of issues like internal fluid evaporation, voltage component damage, or chemical reactions with the internal structure of the battery.
And that might be a best-case scenario. While lithium-ion batteries are generally safe, they can quickly become dangerous if damaged or significantly overheated.
Related: How to Avoid Heat-Related Problems with Your iPhone