The average price of gasoline in the Cincinnati area has risen nearly 50 cents a gallon in the past month and shows little sign of topping out soon.

Area drivers paid an average $3.61 a gallon for a regular-grade gas, according to CincyGasPrices.com, a website that uses spotters to track area gas prices. That compares with a national average of $3.51 on Thursday and an area average of $3.14 a gallon a month ago.

Stations monitored by CincyGasPrices.com were charging between $3.34 and $3.69 a gallon late Thursday afternoon. Diesel fuel was selling for between $3.85 and $4.29 a gallon.

On Wednesday, the nationwide average price for a gallon of gas rose for the 20th straight day to $3.55, a level not seen since late October. It’s jumped 18 cents in just eight days. Gas now costs 7 cents more than it did a year ago.

A number of factors are at play: Higher crude oil prices, slowing output at refineries that are undergoing maintenance, and low supplies of gasoline.

AAA said last week gas prices are expected to rise steadily as many refineries temporarily close for scheduled turnaround maintenance and as the industry begins the complicated process of switching over to summer blends of gasoline.

The Midwest will see an earlier move to low vapor pressure gasoline this year when compared with last year, AAA said.

An explosion and fire at a Toledo refinery last week also could create short-term shortages, AAA said.

The Associated Press contributed to this report.