Canister fuels don't vaporize as well when they are cold, warm it up a bit and it will blow torch again. Put the canister someplace it can warm up for a little bit, inside your jacket will do or heat a bit of water to warm and set the can in a puddle of it while you cook. Also insulating it from the cold helps a lot. set it on a pad, some tree bark, pine branches or what ever you can come up with to keep it off/out of the snow will help performance a bit.
Also some mixes do better in cold than others, snowpeak is one of the better options. Also normally a big no no with canisters but a windscreen...even just a partial one helps a bunch in cold, as it will box in a little bit of heat around the canister---you only need (and want) a little more warmth.