Unless you are using a battery that was made for cold weather usage you are going to have issues with all batteries in the cold. In cold weather the battery is not able to keep up with the current required as well as it would at a normal operating temperature. The chemical reaction which creates the electrons when in use cannot make as much power so more of the metallic lithium (for lithium-ion batteries like the ones in our phones) moves towards the cathode from the anode to make the same current during usage in the cold. This is one of the reasons car batteries usually have listed "Cold Cranking Amps" on them to insure you have enough juice when its cold outside to get an ignition. The only good thing about cold when it comes to batteries is that they deplete a lot less energy when they are cold and unused as compared to when they are warm and unplugged which is why it is always better to keep your unused batteries in the freezer "in a waterproof bag" then in a random desk drawer. On the other end of the spectrum,.. well getting your batteries too hot is just um bad. Don't do it! To ensure good battery time while in the cold, you may want to find a creative way of keeping it warm, like keeping it in the innermost layer of your snowboarding suit as long as you can manage not busting your a$$ and cracking your phone. But beware of tripping the phone's water damage sensor from sweat/humidity!
