With the summer travel season winding down, gas prices are starting to slip.

GasBuddy head of petroleum analysis Patrick De Haan expects the national average gas price to fall below $3, driven primarily by seasonal factors, saying "Americans just don't drive as much in fall." He also notes that the switch to cheaper winter gasoline and the decline in oil prices (CL=F) will help send prices lower too.

What could change that trajectory? Tropical storm Francine and other potential storms or hurricanes could pose a risk, De Haan says, adding geopolitical risk as another potential upward catalyst.

Watch the video above to find out where De Haan says prices in the US are highest and lowest.

For more expert insight and the latest market action, click here to watch this full episode of Asking for a Trend.

This post was written by Stephanie Mikulich.