The national average retail price for a gallon of regular unleaded gasoline in the United States has increased for 15 consecutive days, AAA data show Tuesday.

Oil prices in the United States were in a free fall last year and in early 2015, with the national average price flirting with the $2 per gallon mark. A national average price for Tuesday of $2.18 per gallon is about a penny more than Monday and 12 cents more than one week ago.

AAA notes gasoline prices usually turn the corner at the beginning of February as refineries enter a period of seasonal maintenance.

"Refineries usually schedule maintenance during the first several months of the year when demand is relatively low, which can lead to decreased production and supplies," the motor club explained in a Monday report.

Refineries are also preparing to make a summer blend of gasoline, which requires additional preparations to prevent vaporization during warmer months. That gasoline is more expensive to produce than the winter blend.

On the strike at U.S. refineries, led by the United Steelworkers union, AAA said not to expect any actual reductions in output because of the labor stoppage.

A brief from Patrick DeHaan, a market analyst with the price watchers at GasBuddy.com, said the national average price for gasoline saw its largest weekly advance since mid 2013. Last year's seasonal rally resulted in a 30 cent increase in the price at the pump from Feb. 8 through May 1.

"Gas prices are likely to rise across much of the U.S. this week as well, although the pace should be far more subdued than what we saw this week," he wrote Monday.

Gasoline prices are still relatively low. Tuesday's national average is about 3 cents less than one month ago and $1.11 less than this date in 2014.