Depends if the gas is from a canister in your house or if you're relying on the gas grid which can also fail during a prolonged widespread power outage.
most city natural gas systems are powered by gas powered generators spread around. Multi week outages due to ice storms in the north east have rarely (if ever) caused outages of the gas system.
So long as you have some lighters, matches, or a mechanical sparker because the built-in ignitors won't work without power.