Q: What's the lowest operating temperature for iPhone 4S?

A Google search is your friend. This was the first hit with a search for "iPhone 4S specs".

http://www.apple.com/lae/iphone-4s/specs/

Operating temperature: 32° to 95° F (0° to 35° C)

Nonoperating temperature: -4° to 113° F (-20° to 45° C)

Relative humidity: 5% to 95% noncondensing

Maximum operating altitude: 10,000 feet (3000 m)

From Apple.com iPhone tech specs

Operating ambient temperature: 32° to 95° F (0° to 35° C)

Nonoperating temperature: -4° to 113° F (-20° to 45° C)

Relative humidity: 5% to 95% noncondensing

Operating altitude: tested up to 10,000 feet (3000 m)