National gasoline prices spiked amid the devastation caused by Hurricane Harvey, as the average price increased 4 cents to $2.37 per gallon for the week ending Aug. 28, according to AAA.

The weekly surge was the largest increase this summer amid increasing prices brought by increased demand.

About a quarter of the refining capacity in the Gulf Coast, or about 2.5 million barrels. was taken offline as a result of the storm, according to the Oil Price Information Service. Eight refineries in Texas were shut down, including ExxonMobil Baytown, Deer Park, Pasadena Refining, and Phillips 66 Sweeny in the Houston area. In Corpus Christi, four other refineries remain closed, including Flint Hills, Valero, CITGO, and Valero Three Rivers. Those four were shut down last week ahead of the storm.

"No doubt, Harvey has impacted operations and access to refineries in the Gulf Coast.  However a clear understanding of overall damage at the refineries is unknown," said Jeanette Casselano, AAA spokesperson. "Despite the country’s overall oil and gasoline inventories being at or above 5-year highs, until there is clear picture of damage and an idea when refineries can return to full operational status, gas prices will continue to increase."

At least one pipeline company also suspended operations. On Sunday, Magellan Midstream Partners stopped all inbound and outbound refined products and crude oil transportation services on its pipeline systems in the Houston area. The Colonial Pipeline, which delivers gasoline from Houston to the Mid-Atlantic, said its Gulf Coast pipeline and terminals are continuing to operate normally.

To help alleviate a shortage of supply, the Environmental Protection Agency (EPA) will waive environmental standards on gasoline for select counties in Texas.

“As in any national or local state of emergency, AAA expects gas prices to be held in check up and down the gasoline supply chain, including prices set by refiners, distributors and dealers unless there is a clearly justifiable reason for an increase," said Casselano.

Gasoline prices in the South and Southeast states now average 3 cents higher this week. The steepest increases came in Florida (7 cents), Georgia (5 cents), South Carolina (5 cents) and Texas (4 cents).

In Texas, retail gas station outages have been reported. In Houston, gasoline prices are about 4 cents higher than a week ago.

Meanwhile, the average price of diesel increased nine-tenths of a cent to $2.605, which is 19.6 cents higher than a week ago, according to the U.S. Energy Information Administration.