The temperature underground in the lower 48 states stays around 54 degrees all the time. The gas tanks will be at about that temperature except right after the tanker has dumped gas in; at a large station with a big tank it still won't change that much. I suggest people that are really curious take a thermometer and stick it on the metal of the pump nozzle while pumping gas or just after. Don't do anything stupid like trying to stick it in the stream of gas or pull the nozzle partly out while pumping! I used to work in a gas station the summer before going to college. I can assure everyone that gas is always pretty much the same fairly chilly temperature. We did personally wait a few minutes for crud to settle after the tanker added gas, but nowadays, especially in California, the tanks are required to be pulled out and replaced so often in order to prevent leaks, that sediment is not so likely.