Apple states: Operating temperature: 32° to 95° F (0° to 35° C) >> http://www.apple.com/iphone/specs.html Users report that the screen stops working pretty much below 10° F Good luck with a winter snow emergency and calling for a tow out of a snow drift or something. There ain't no app for that. But here is a fun fact. At 7° F, your tongue will stick to the iPhones glass screen. If that should occur, experts recommend using an N900 to call the local Fire Department.