Gas prices in Arizona have been steadily growing since last March, with a 62.5-cent increase on average for a gallon of regular over the last month, according to AAA. And, as motorists head into summer, prices are likely to keep creeping up.

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The average price for a gallon of regular gas in Arizona reached $4.29 on Monday. That’s lower than it was about this same time last year, according to the auto and travel company, but still 79 cents higher than the national average this week of nearly $3.51.

AAA spokesperson John Treanor said there are a number of reasons prices have increased over the past few weeks in Arizona – oil refineries are conducting maintenance and inspections, which leads to less fuel production. But motorists still demand fuel.

“Arizona gets their gas from two different places,” Treanor said. “One is from California through a pipeline, and the second are Texas and New Mexico. And right now, Texas and New Mexico are where we’re seeing refineries undergoing maintenance, so the counties that get their gas from Texas and New Mexico are seeing prices increase,” Treanor said.

Some Arizona counties have higher gas prices than others. Maricopa County averages at $4.61 per gallon while Navajo County averages $3.74 per gallon, according to AAA’s gas prices website.

Gas prices are trending upwards across the U.S.

Maria Reyes, a stay-at-home mom, said high prices are leading her husband, an electrician, to reassess where he travels to help clients. Reyes’ husband has traveled to Tucson and Prescott for work but now is considering if such trips are even “worth it.”

“I’ve been noticing little by little and it’s been sneaking up on us. It’s high enough for me to notice,” said Reyes, as she pumped gas at a Phoenix station Monday.

Reyes hopes to see a decrease in gas prices soon.

But Treanor said that although price predictions aren’t exact, they are likely to increase even further as drivers head into a “busy time with summer driving season.”