In a ritual as indicative of spring as the blooming of flowers and return of songbirds, gas prices are on the rise again.

New Hampshire’s average gas price hit $2.46 per gallon this week. That’s 8 cents more than last week, 18 cents more than last month, but 1 cent less than this time last year, according to Daniel Goodman, manager of public affairs for AAA Northern New England.

“Historically, we see gas prices increase about this time of year every year and it’s primarily due to the switch over to summer blend (gasoline),” he said.

Beginning in the fall, refineries produce gasoline with a higher rapid vapor pressure (RVP) because the fluid has to evaporate at lower temperatures. But during the summer, the gasoline needs to have a lower RVP to prevent excess evaporation, Goodman said.

That means twice a year refineries go temporarily offline to adjust their process, reducing the supply of gasoline. Meanwhile, drivers are taking to the road more as the weather warms increasing the demand.

The result? Higher prices at the pump.

The national average this week is $2.59 per gallon, according to AAA. California, as usual, posted the highest price, $3.39 per gallon, while Utah’s was the lowest at $2.32 per gallon.

The average in Vermont is $2.55, Maine’s is $2.54 and Massachusetts is $2.53.

“AAA expects gas prices to increase probably another 10 to 15 cents, with the highest prices probably happening in May,” Goodman said.

“We don’t think the average in northern New England will hit that $3 mark.”