The national average for a gallon of gasoline continues to surge higher in the U.S. as oil prices keep rising.

The national average rose to $3.88 per gallon on Monday, according to data from AAA. That’s up from last week’s $3.87. A year ago, a gallon of gas cost $3.68, twenty cents lower.

The culprit is rapidly rising oil prices. The price of Brent crude nearly hit $98 a barrel on Monday before moderating to around $94.83, an increase of around 0.9 percent. The price of West Texas Intermediate crude rose 1.5 percent to around $92.16.

Demand for gasoline and oil typically falls after Labor Day as school resumes and families spend less time on the road. Last week, demand fell to 8.31 million barrels per day from 9.32 million barrels per day. Gasoline stockpiles jumped to 220.3 million barrels from 217.7 million barrels, according to AAA.

“Oil costs are putting upward pressure on pump prices, but the rise is tempered by much lower demand,” Andrew Gross, AAA spokesperson, said in a statement. “The slide in people fueling up is typical, with schools back in session, the days getting shorter, and the weather less pleasant. But the usual decline in pump prices is being stymied for now by these high oil costs.”