You can protect your camera from falling snow by slipping it under your parka or into a plastic bag between shots. Your body loses heat faster than it can produce it, and you lose control before you know it. The best advice is to stay warm and dry and call it a day before fatigue sets in. Check with your physician or an outdoor store for more information. Although thickened lubricants may cause a cold camera to malfunction, most problems in the cold arise from insufficient battery power.
Batteries supply power to the exposure meter, winder motor, flash, and so on.
The cold saps power from the batteries, which sometimes causes the camera to malfunction. So keep the batteries warm by keeping the camera warm inside your coat. Incidentally, if you carry your camera under your coat, you may not need a case, which can be an annoyance when you are trying to get a hurried picture. Keeping the camera warm is especially important with automatic cameras and video cameras that depend heavily on battery power. For example, if the batteries in a video camera are cold, the videotape may not advance at the proper speed.