Despite record-breaking warmth in December, some of Maine’s larger ski resorts have been able to remain open because of recent advances in snowmaking technology.

Among those benefiting from the new technology are Mount Abram in Greenwood, Sugarloaf in Carrabassett Valley and Sunday River in Newry.

Lost Valley in Auburn reported on its Facebook page that snowmaking will allow the Bobcat trail to open Tuesday, and Shawnee Peak in Bridgton plans to reopen Saturday. Night skiing at Shawnee Peak will begin Monday.

Upgrades in recent years have allowed ski areas to make snow when it’s 32 degrees, as opposed to older equipment that required temperatures of 28 degrees or lower.

More-powerful water pumps and low-energy snow guns allow them to make up to twice as much snow while using less energy.

The resorts also credit the improved snowmaking with allowing them to attract skiers to the slopes despite the unseasonably warm start to the season.

The average temperature in Portland this month was 38.9 degrees as of Wednesday evening, according to the National Weather Service in Gray. That was as 8.4 degrees above normal, and higher than the all-time record of 34.8 degrees set in December 2001.

Up in the mountains, it’s been colder, but not by much. The mean average temperature in December in Eustis, a weather service station just north of Sugarloaf, was 30.3 degrees on Tuesday – about 12 degrees higher than normal, according to the weather service.

Yet Sugarloaf reported 6-12 inches of snow on its slopes Friday, with 19 of its 162 trails open. Sunday River reported 3-12 inches of snow Friday, with 33 of 135 trails open.

And Mount Abram, which opened earlier than ever this season, reported 6-18 inches of snow Thursday. Mount Abram was closed on Christmas but will reopen at 9 a.m. Saturday.

“With the water pumps and the new guns working in tandem we are covering terrain four times as fast. It is a dramatic improvement,” Mount Abram general manager Dave Scanlan said.

“With the weather we’ve been having this has been critical, because we’ve been able to maximize on the cold temperatures we have had. If we hadn’t made these upgrades, we would not be open yet with the weather we’ve had. Now we will have both sides of the mountain open by Saturday. We are sitting pretty good.”

Mount Abram invested more than $475,000 last year on 25 new airless snow guns and a high-pressure water pump. As a result, it was able to open for the season at the start of December for the first time in its 55-year history.

“Now we cover a trail so much faster than we used to. We can lay down a thick base (of snow) quickly that’s enough to carry us through the warm, rainy weather,” Scanlan said.

Mount Abram is the only ski area in Maine to invest in airless snow guns, said Rob Donovan, the North American representative for Nivis, the Italian-based company producing the new technology.

Traditional snow guns use compressed air and high-pressure water that are pumped up the mountain in separate hoses. The two are mixed when they the meet in the gun to create man-made snow.

The new snow guns at Mount Abram don’t require compressed-air hoses. Instead, they pump the water up the mountain under high pressure, using that energy to create compressed air at the head of the gun and eliminate the need for an air compressor and a diesel engine to push air up the mountain.

Mount Abram’s new water pump and can move 1,200 gallons of water up the mountain every minute, as opposed to 350 gallons previously.

“The gun uses the ambient air in the atmosphere and combines it with the high-pressure water,” Donovan said. “You harness the energy from the water pressure. When it’s spraying 290 (pounds per square inch), that’s pretty powerful. You harness that and as it comes through the tower into the snow-gun head, it separates the air and water. It ejects them from the gun head, creating its own compressed air.”

Donovan said other ski areas are testing the new technology. He said Nivis started testing the airless guns at Mount Abram last year because the resort has made a commitment to environmentally friendly equipment, as demonstrated in its fleet of solar panels and the wood stove that heats its lodge.

Today more than ever in the ski industry, the buzzword often heard is “efficient.”

“Those windows of time when we can make snow are getting smaller. There are fewer windows where the temperatures are low enough,” said Landon Fake, the general manager at Camden Snow Bowl.

“For us, typically, those windows are at night. … Having the capacity to blow a lot of snow is important.”

The Camden Snow Bowl just spent $1 million on a new snowmaking system that includes 40 new snow guns, 4 miles of new water pipes, and a 400-horsepower water pump. Fake said the more-efficient snow guns can cover twice the terrain using only a 35 percent increase in compressed air, from 20,000 cubic feet per minute to 27,000 cfm.

“We kind of went from a system that was just cobbled together to basically hiring an engineer and designing a complete system that was balanced, used the right mount of air and the right amount of snow guns to make us more efficient,” Fake said.

At Sugarloaf, snowmaking capacity has doubled since 2010 while the energy output has decreased by 40 percent, spokeswoman Noelle Tuttle said. Sugarloaf invested $2.5 million in 2 miles of water pipes and 620 new low-energy guns, she said.

The warm weather and the lack of snow have been making some skiers hesitant to make advance reservations, Tuttle said.

So Sugarloaf responded by softening its room reservation cancellation policy. Guests can now cancel as late as seven days before they arrive, and if they still decide to cancel, they will only have to forfeit their $100 deposit instead of 50 percent of their total bill, Tuttle said.

The new policy seems to have worked and has attracted more skiers despite the warm weather.

“We’ve seen a lot less hesitancy to make a reservation,” Tuttle added.

Sunday River spent $15 million in a revamped snowmaking system over the past six years, including $5 million in 500 energy-efficient snow guns. With more-efficient guns, Sunday River can make twice as much snow in about a third of the time, spokeswoman Sarah Devlin said.

This year, it meant opening day coming as early as Oct. 19. The upgrades also resulted in Sunday River’s snowmaking team being recognized as one of the six best in North America by the Ski Area Management association.

“We’ve hung onto and maintained the terrain we had, and in fact increased it by eight trails this week,” Devlin said in an email Thursday night. “We still have the most open terrain in New England so while there may seem to be an overall decline in skier traffic because of the warmer temperatures, people do tend to choose Sunday River when the weather is more marginal.”

Devlin said Sunday River is hosting ski camps that were scheduled to be held at other resorts because Sunday River has snow and they don’t.

“We do everything we can to make sure skiers can get on snow,” Devlin said.