The slide in oil prices over the last month will probably bring $2 gasoline back to filling stations across the United States later this year, AAA said Friday.

U.S. crude prices have fallen 20 percent over the past month amid a glut of shale oil. Pump prices are already at the lowest seasonal level since 2009, averaging $2.66 a gallon, and they’re in store for another “dramatic” decline in September when refineries switch to making a cheaper winter gasoline blend, the nation’s biggest motoring club said in an emailed statement.