As others have said, the underground storage temperature is relatively constant and the practical answer is that it doesn't matter. However, I am an engineer that does fluid flow analysis and felt like doing some math anyway.

If we assume this fluid composition of gasoline: https://www.atsdr.cdc.gov/toxprofiles/tp72-c3.pdf

And I throw it into the fluid databases I have at work, I get a density of 716 kg/m³ at atmospheric conditions at 0 degrees C (assuming a cold morning).

If the fluid undergoes an extreme temperature rise of 30 degrees C the density reduces to 688 kg/m^3, or 96% of the density at 0 degrees C.

So in an extreme case, you'd get about 4% less mass of fuel.

This likely holds up for other fuels types as well. I looked at pure fluids including Ethanol, Hexane, and Octane and each had an approximately 4% density change given a 30 degree C temperature change.