Most commercial aircraft require a mechanic to inspect the aircraft before Take off, at or below -40C (or -40F, same thing).
Most jetfuel freezes below -40 to -50 degrees C.
I bid (airline pilot) tropical routes in the winter for a lot of reasons...
Yes we were grounded until it got warmer than -40F and honestly when we took off the temp was bouncing all over the place. It’s crazy how unstable the temperature was.