Ole Jorgen Liodden took his 7D,5dmk2 and 1dmk3 to one of the most extreme areas of the planet and put it against the elements. Wet snow these conditions might destroy cheaper cameras after a few hours but not a Canon, here his conclusion;
All three cameras performed very well for the whole Antarctica expedition. The 7D performed as I had hoped, surpassing 10,000 exposures without a problem. I must admit that the 5D Mark II surprised me as well with its build quality. The 1DS Mark III camera is the most rugged and best weather sealed, but the 7D and 5D Mark II (without battery grip) performed 100% in my opinion.
I have not tried to drop the 7D or 5D Mark II “by accident” into salt water, but I don´t expect them to survive as well as the Mark III / IV cameras. It will be interesting to hear your opinions regarding your use of these cameras (especially the 7D) in extreme weather. Have you had any different experiences, or mostly the same as mine?
check the full article: http://canonfieldreviews.com/7d-1-weather-sealing/