By Kevin Murphy

KANSAS CITY, Missouri (Reuters) - Motorists hit the road in large numbers this Labor Day weekend, undeterred by gas prices that are the highest ever heading into the holiday in part due to Hurricane Isaac, which forced the closure of oil refineries on the Gulf Coast.

The average price of regular gas nationally was $3.83 per gallon on Friday, 21 cents higher than a year ago, according to AAA. And the price on Monday will likely easily beat the Labor Day record of $3.68 set in 2008, the non-profit automobile association said.

The weekend is one of the busiest on American roads.

In Overland Park, Kansas, Shelly Faught and a group of relatives packed up several vehicles for a drive to a lake home in Arkansas despite having to pay $3.79 per gallon at the pump.

"We needed the escape," Faught said as she gassed up a pickup truck hooked to a pop-up camper. "We were a little nervous about the gas prices rising but we had this planned."

Juan Mendez of Liberty, Missouri, and his wife Ashlee traveled 215 miles on Friday to Wichita, Kansas, because they wanted their infant to meet Mendez's parents. Mendez was not happy to see gas prices go up before the trip.

"It's one of those things you just have to deal with, there is nothing you can do about it," he said.

Terry Goode, a travel counselor at the AAA office in Kansas City, Missouri, said customers seem to be traveling as much as ever and have been streaming in for travel books and route advice.

"I've not heard people mention high gas prices," Goode said. "They just make it part of their budget and go."

Average gas prices jumped by nearly 31 cents a gallon in August and have risen 11 cents since August 22, when forecasters first predicted that Isaac would reach the Gulf Coast and threaten to close oil refineries, AAA said in a report.

The group nonetheless projected that 33 million Americans would travel 50 or more miles (81 or more km) on Labor Day weekend, including 28.2 million by car. The projected number of car travelers would be 500,000 more than last year, AAA said.

Rental car agencies were bustling with business ahead of the weekend. At the Budget Rental Car outlet in Overland Park, 25 cars were reserved on Friday, said rental agent Ryan Mikel. That compared to only three reservations on Wednesday.

Mikel said the hassle of flying likely was spurring customers to bite the bullet and drive.

But the high gas prices gave others reason to pause.

Sarah Allison said at an AAA office in suburban Kansas City that she and her husband decided to fly rather than make a 1,100-mile (1,770-km) round trip to Dallas.

In Leawood, Kansas, Diana Weeks-Radke paid $3.86 a gallon on Thursday to fill up her car. She said a sudden price increase at the station was unfair.

"It's shameful," Weeks-Radke said. "The fuel is already there, bought and paid for and delivered."

AAA spokesman Michael Green said consumers often criticize gas price spikes but failed to realize that gas stations that held prices at lower levels would run out of gas quickly and be forced to buy more at higher wholesale prices to replace it.

"We don't really see gas stations taking advantage of drivers," Green said.

Green said the closure of refineries due to Isaac reduced fuel supply and raised demand, forcing up prices. Other factors for the higher prices included a refinery fire in Venezuela and a jump in world oil prices.

(Editing by Paul Thomasch and Paul Simao)