I love big falling snow especially for photography. When it’s snowing hard, the falling snow really gives some great atmosphere. If you use fast shutter speeds e.g. 1/125 or higher you can suspend each snowflake in air like I did for the photo below:

©Darwin Wiggett - 1/250 at F8 - Canon Rebel T2i, Sigma 70-200mm lens
To show you just how hard it was snowing here is a little movie clip of the same scene:
So if you want to stop the falling snow use a fast shutter speed. In the dim light of a snow storm you’ll often need a fast lens and a higher ISO to get the shutter speeds you need. In the shot above I used my Rebel T2i at 800 ISO and my Sigma 70-200mm lens wide open at f2.8.
If you want long streaks of falling snow use a lower ISO (like 100) and extend your shutter speed to at least 1/15th of a second or longer. In the photo of the Weeping Wall taken just after I made the image of the tree in the snowstorm, I used a shutter speed of 1/4th of a second to blur the snow into long diagonal streaks. You can see the streaking snow in the dark canyon wall.

- ©Darwin Wiggett – Canon Rebel T2i, Sigma 70-200mm lens, 1/8s at f11
If the temperature is below freezing I don’t worry about exposing my camera or lens to the falling snow, it will just wipe off as long as the camera and lens are not warm. If the snow is melting when it hits the camera, I will place a plastic bag over the camera and lens to prevent moisture from seeping into the gear. Here are a couple of more images from the same stop at the Weeping Wall in Banff National Park.

©Darwin Wiggett - Canon Rebel T2i, Sigma 70-200 lens, 1/640 at f2.8

©Darwin Wiggett - Canon Rebel T2i, Sigma 70-200mm lens, 1/125 at f2.8
Don’t let a little foul weather trick you into putting your camera away, keep shooting and use shutter speeds to control the look of the falling snow. To learn more about how to always pick the right shutter speed check out this link.