I'm not sure about the CO2 cartridges used for tire air, but as the former Aviation Life Support Officer I can tell you that with our CO2 cartridges for our May West Vests and Survival Rafts we did not experience any issues from really hot - desert climates to -65 degrees F. (that is without wind chill).

I can tell you that the darn things will loose pressure / gas over time and you can weigh a new one, if you can find it, and then weigh yours and determine if it will even work any longer. I wouldn't suggest subjecting it to a hair dryer, clothes dryer or flame. I have seen them make really neat rockets, especially the big ones. Of course we were using a nail to puncture the seal to officially test viability of a given group (yea right - it was fun and the tether ball pole was a great launcher). Don't do this at home!