Apple has issued a support document that warns customers not to use their Apple iPhone in places where the temperature is below freezing or above 35º C (95º F). It says a built-in safety mechanism will cause a warning message to appear if the device becomes too hot. It also says the iPhone 3G and iPhone 3GS shouldn’t be kept in places where the temperature is between -20º and 45º C. Recent news reports have suggested that the iPhone can become discoloured due to an overheating battery. [Sources: Apple.com; wirelessandmobilenews.com]