In the POH for the Cessna Caravan, the following is stated in the Weight & Balance section:
Information on the Weight and Moment Tables for different fuel grades is based on average fuel density at fuel temperatures of 60°F. However, fuel weight increases approximately 0.1 pounds per gallon for each 25°F decrease in fuel temperature. Therefore, when environmental conditions are such that the fuel temperature is different than shown in the chart heading, a new fuel weight calculation should be made using the 0.1 pounds per gallon increase in fuel weight for each 25°F decrease in fuel temperature.
The above corresponds quite well with the coefficient of thermal expansion explained by Enicalyth.