There has been a buzz of a big ole blizzard moving through the Midwest this past weekend so I am going to give you some adverse weather photography tips to help protect your gear and to protect yourself. Protecting your gear:
The weather sealing on the prosumer models and canons L lenses are very good, even still I protect my gear. I know the cameras are well-built but I am still a nervous nelly when it comes to leaving my gear exposed to natures wrath. In rain, I recommend the OpTech rain Sleeve. Even without the rain sleeve, I have been in a tight situations and used those plastic grocery bags to help protect my gear from the rain. Photographing the Slot Canyons in Arizona I also used the plastic grocery bag to protect my gear from the falling sand. I have used a shower cap from the hotel when hiking in the hail in Yosemite. It's a good idea to keep a shower cap in your gear bag. They are small, lite, and have many uses. Pretty much anything will help to protect your gear and ultimately your hard earned money. While photographing the lighting in Yosemite (this posts picture), I used an extra jacket that I had brought along, and draped it over my camera which also protected my cable release from the rain. I also have a lowepro backpack that has a rain cover. This helps protect my bag full of gear from getting rained or snowed on.
Photographing in snow and cold, it's not so much how to protect your gear but how to warm it up after your adventure. When the camera warms up it builds up condensation, to avoid this put your gear in a plastic bag and let it come up to room temp. The condensation will accumulate on the bag and not on your camera and lenses. I use a tip I learned from Moose Peterson. Moose recommends putting your camera in your camera bag zipping it up and let it come up to room temperature that way. This is what I do and it seems to work well.
Always dress for the occasion. Get a good technical shell that will seal out the elements and wear the proper amount of layers! I recommend a gore-tex jacket from a good brand like marmot or arc'teryx. Get a good pair of gore-tex boots from Asolo or Zamberlan. It's no fun when you're frigid cold or soaking wet. Use common sense and be safe. Mother Nature is a force you don't want to mess with, but often the best times to photograph nature and landscapes is during or just after a storm.
Get out there and brave the elements. You are sure to come up with some compelling and powerful images.