Why is gas so expensive in the summer? You may sometimes wonder why the price of gasoline fluctuates as seasons change. It is primarily due to the Reid Vapor Pressure (RVP). The higher the RVP of the gas, the more likely it is to evaporate. Refineries produce gas with a lower or higher RVP depending on the season.
During the summer, refineries produce gas with a lower RVP, which requires costly oxygenates. During the winter season, gas evaporates at a much slower rate than it does during summer so it needs less oxygenates added to it. Also, before the summer season starts, refineries usually perform maintenance to ensure their facilities will continue to function properly.
Refineries reduce their output at this time, which reduces the supply of, and demand for gas. This is why gas prices rise during the summer season.