PORTLAND — Gas prices in Maine are back on the rise after sharp decreases in the global price of crude oil caused the price of regular gas to drop to less than $2 per gallon in some parts of the state.

The average price of a gallon of regular gasoline in Maine ended last week at about $2.20, according to the tracking site GasBuddy.com and AAA. That’s 10.5 cents higher than the average price reported the previous week. The national average for a gallon of regular gas rose 12.6 cents during the same period, to $2.17.

The rise that began in Maine on Feb. 3 comes after gas prices in the state and the country have apparently hit bottom and are expected to continue rising in advance of summer months, when consumption emissions standards for refineries are higher.

“While the pace of increases will slow in the week ahead, we’re looking at continued gas price increases over the next few weeks,” Patrick DeHaan, a senior petroleum analyst with GasBuddy, said in a news release. “Oil prices have risen, contributing to the higher prices, but also worrisome are the refinery strikes initiated over the last week that have oil companies scrambling to keep refineries online.”

Reuters reported last week that about 4,000 union workers are on strike at nine plants in California, Kentucky and Texas, including seven refineries that account for 10 percent of U.S. refining capacity. The strike is the biggest in the U.S. refinery sector since 1980.

Prices in Maine are still about $1.26 lower than a year ago after dipping to the lowest levels since 2009. The cheapest gallon in the state was at $2.01 as of Sunday night.

Nationally, GasBuddy said the percentage of stations selling a gallon of regular gas for less than $2 has dropped dramatically, from about half to about 27 percent.

By Maine county, the site found the southern and western counties of Oxford, Androscoggin, Cumberland and Sagadahoc had the lowest average prices while northern and Down East counties of Aroostook, Piscataquis and Washington had the highest average gas prices in the state.