I've read on here that trying to cool your wort in the snow really isn't a good idea (assuming you mean put the kettle IN snow.) Snow is a great insulator and it will take forever to chill. If you meant putting snow in the actual kettle, then disregard this post!
Set it on the back porch with a lid on at 10 degrees F and it will cool in a few hours. I've done it.
If you set it on a snowabnk though it would probably melt the snow and tip over.
Having chilled in the snow, as long as you keep stirring, and moving snow against the sides of the pot, you can be down to temps in 20 minutes. Its a bit of work, you can't just 'set it and forget it' but it works if you do.
Winter brewing is one of my favorites. I brewed a batch today and the temp was 1°C 34°f. The groundwater temp was 50.3°f. It probably took a little longer to get to mash temp but the chill went very fast. Hoses are harder to rewind though.
I think winter is the best time to brew. I brew in my garage and in the summer it gets too damn hot in there. Not to mention I LOVE having water temps in the 40's. Makes chilling my wort a breeze. This summer my average water temperature was 80 and so I had to buy a $3.00 bag of ice every time I wanted to brew. It was such a pain in the @ss.
I brewed 10 gallons today and i dont think it got above 35°. Nothing real bad. My regular outside hose that i would use for chilling was frozen 2 weeks ago. I just use my RV hose in the winter. Well water is fantastic in the winter for chilling lagers to 50°
I just started brewing a few months ago and realized I had to ferment down in the parkade storage lockers because of the temps. They were in the high 20's Celsius back in September in the apartment. I was disappointed at the time because the parkade is heated in the winter and I didn't think I would ever be able to lager. However.... I checked the temperature the other day and it sits perfectly at the lower end of the lagering temperature range! Woohoo!
I think what a lot of brewers do is brew what the season allows for. When cold lager!