Well, that'll work, BUT you could also blow yourself sky high. Maybe not too much chance in really cold weather, but you have to be really cautious with that technique. Supply enough heat to the canister, and you're in fat city. Too much and KABOOM!

Water on the other hand is pretty safe. You can feel how hot or cold the water is before the canister ever touches it, and the water generally won't get hotter as you cook in cold weather.

I'll do a post at some point in the future on various canister warming techniques (water, windscreen, copper wire, and body heat being the standard techniques). Body heat and water are pretty safe. The windscreen and wire techniques can be down right dangerous if you don't know what you're doing or are not careful.

HJ