setting the fuel on a piece of foam will insulate it from the 32 degree snow, but the cannister will still get cold as the warm gas evaporates off and carries with it the heat of evaporation. The cannister MUST cool off proportionately to the amount of gas that comes out, which is to say that its a loosing battle unless you can supply more heat - it has to cool. Butane stops being a gas at around 32 F, and isobutane around 15 F, but Propane will go to -40 F or C, so isobutane or isobutane with propane would be better.

You do not need a pan of warm water, only a pan lid.
BUT
When you are sitting in a blizzard melting snow and you have to keep pouring precious hot water into the inverted pan lid that the flue sits on, you'll wish you had white gas instead.
Jim