https://www.cnet.com/news/how-long-can-your-phone-survive-in-a-polar-vortex/

iPhones don't do well in extreme temperatures -- anything colder than 32 degrees Fahrenheit (or anything hotter than 95 degrees Fahrenheit), according to Apple. The company suggests shutting the phone off if it's colder than four degrees.

The phone's lithium-ion battery can stop discharging electricity at extremely cold temperatures.