Have an expensive smartphone? Here's how to protect it in the cold weather.

Some smartphones list the optimum range of temperatures in their technical specs. For example, when it's turned off, the iPhone 5S can withstand temperatures between -4° and 113° Fahrenheit. When it's turned on, the range is much more narrow. Apple suggests 32° Fahrenheit as the lowest operating ambient temperature. Other phones are rated for much lower temperatures, and some can go as low as -4° Fahrenheit while in operation.

When lithium-ion batteries are exposed to cold temperatures, their performance suffers. When cold, a phone battery can drain faster than normal or it might say it has ample power remaining and then suddenly go dead. The problems are only temporary and the battery should behave normally when the device is brought back up to warmer temperatures.

In the event that your phone does shut down, do not restart it until you're inside and give time for your phone to warm up. Restarting your phone immediately could actually cause more harm to your phone and actually shorten your battery life.

It's not just the battery, smartphones are made up of other delicate electronic parts, like their LCD screens, that can malfunction in extreme temperatures.

Freezing temperatures can also make a phone's glass surfaces more sensitive to cracks and breaks, especially if there's already a flaw or nick in any of the glass. There have been reports of the glass on the back of the iPhone shattering in extreme cold temperatures. In Finland, where the average high temperature in the winter is 1°C, the government Consumer Agency has warned citizens that the phones might suffer performance issues in the cold weather.

To keep phones from getting too chilly, don't leave them alone in the elements, like in a parked car. Stashing them inside pockets closest to your person, where they can absorb some of your body heat, is best. If you do need to leave it behind, turn the phone off instead of just putting it to sleep.

Cases also help to keep phones warm. There are even cases especially built to regulate a phone's temperature in extreme situations.

If you're depending on the phone to make outgoing calls in case of an emergency, say while driving on icy roads, keep a back-up power source with you.