Hurricane Harvey, now Tropical Storm Harvey, has unleashed unprecedented amounts of rain in and around the Texas Gulf Coast, affecting homes, businesses and oil refineries.

About one quarter of the refining capacity in the region has been knocked offline, leading to more expensive gas prices across the country.

The national average could climb to $2.50 as a result of Harvey. The last time the average reached $2.50 was Aug. 28, 2015. Some Texas refineries could be back online as early as the end of this week, while refineries near the Texas/Louisiana coast are operating at reduced rates.

The immediate impact is not as dramatic at gas pumps in Delaware so far, but this could change ahead of the Labor Day holiday weekend.

At $2.25 per gallon, the Delaware gas price average as of Aug. 30 is up five cents overnight and up three cents over last week. At $2.22 per gallon, the Dover gas price average as of Aug. 30 is up four cents overnight and up two cents over last week. At $2.33 per gallon, the Maryland gas price average as of Aug. 30 is up two cents overnight and up three cents over last week.

“Despite the country’s overall oil and gasoline inventories being at or above five-year highs, until there is clear picture of damage and an idea when all refineries can return to full operational status, gas prices will continue to increase,” said Ken Grant, manager of public and government affairs for AAA Mid-Atlantic. “Pump prices are expected to climb at least through the Labor Day weekend, when drivers could pay the highest gas prices for the holiday in two years.”