I know that the battery stops working when it gets too cold and I'd need to warm it up again, but other than that, is there anything else that I'd need to know if I want to shoot in -10C or -20C or even -30C? Do I need some sort of protection for the camera? And how can I protect it against condensation when walking inside, the temperature difference apparently can be 40C! I suppose I'd need to buy some kinda backpack or something and put it inside, but I doubt that that would help.
As for rain, is there some sort of protection? I've seen people mostly shooting with bare cameras in the rain, and I think once or twice I've seen people with a plastic bag wrapped around the camera (including the lens). It looked goofy and extremely uncomfortable to use from the looks of it, so I presume that's the protection from rain... But is there some sort of a different protection? Maybe I could seal up the camera with some plaster or something like that?
And what about snow? Would I still need the protection when it's snowing? After all, snow would only be 'wet' if it melted.
Any other tips would be useful... This is my first DSLR.
Note: I'm talking about walk-and-shoot kind of photography, where you stop for a few seconds to set the right settings and take the shot, then keep walking, not a tripod. The tips I've found so far seemed for a tripod and such, offering a hood-like cover.