Ski resorts rely on snowmaking to get through winter. Climate change is making that harder.

A few days before Thanksgiving, Mark Nelson had hoped to be making snow at Bolton Valley Resort in northern Vermont. But instead, hoses hooked up to air compressors were just blowing air out over the icy ground to keep the system in working order in case temperatures dropped later in the day.

“We call it marginal when the conditions are like this,” Nelson, the independent ski area’s snowmaking supervisor said. “Marginal snow making.”

At 30 degrees Fahrenheit with high humidity, the afternoon was a bit too warm. Nelson wanted to see the temperature drop to at least 26 degrees. In some spots, his team had already covered trails with at least two feet of snow over the previous few weeks.

“That’s a pretty good amount to start with, but we need some more,” he said. In order to open by the holiday weekend though, they’d need “a couple of feet spread across the whole width of the trail, and top to bottom.”

For small, independent resorts like Bolton, making enough snow is crucial for a good season. Larger conglomerates like Vail Resorts — which owns ski areas in the U.S., Canada, Europe and Australia — can balance out a bad winter in one part of the globe with a good winter somewhere else. Small resorts don’t have that luxury. Hedging the ups and downs of winter weather means making snow at every possible moment. But as the climate warms, that’s getting more challenging.

Whenever it does get cold enough, Bolton is ready to fire up the snow guns, said resort president Lindsay DesLauriers. Since her family bought the resort in 2017, she said they’ve spent about $1 million on their snowmaking system.

“[We’ve] bought a lot of guns, more hoses, updated pumps, added compressors,” she said, “which has been totally transformational, to be honest.”

Now, DesLauriers said the system can get up and running faster and pump out about twice as much snow as it used to. And that’s becoming essential. At least anecdotally, the periods when temperatures are cold enough to make snow are getting shorter. 

“We’re getting these really short windows, and we really have to capitalize on it,” she said.

According to a state climate report, Vermont’s winters have warmed more than 3 degrees Fahrenheit over the past century, and the state has lost several weeks when temperatures fall below freezing. 

Across much of the U.S., winter is warming faster than other seasons. But until recently, ski resorts could counteract that with snowmaking, according to Daniel Scott, who’s studied the effects of climate change on the ski industry at the University of Waterloo.

“From the 1980s to the ‘90s, and the ‘90s to the 2000s, average ski season length across the U.S., all the different regional markets, was actually getting longer,” he said.

But in the 2010s, that started to change. “We’ve seen that shift so that the ski season lengths have stabilized or declined in most regional markets over the last few years,” Scott said.

Those declines could get worse, especially for certain resorts.

“The truth is, the biggest fight you’re fighting is probably altitude,” said Shaun Kelley, who analyzes the ski industry for Bank of America. If more urgent action isn’t taken to cut climate warming emissions, he warned that lower-lying ski areas will face the biggest challenges.

“Lower elevation ski resorts, those are going to be more prone to either melting events or to rain events,” he said. “And at some point, it’s just not going to be worth the sort of incremental investment.”

Those resorts could close, which could lead higher elevation resorts to gain market share, he noted. Bolton Valley — with a base elevation above 2,000 feet — could be among the beneficiaries.

“We have a very high base elevation, and we’re in the northern part of the state,” noted president Lindsay DesLauriers. 

So, she said, they plan to invest more in their snowmaking system in the years ahead. But they’re spreading out their risk by spending on summer attractions too: Mountain bike trails and a wedding venue.

Still, the real moneymaker, she said, is winter. Which means, they have to ride the season’s inevitable roller coaster.

“We know that we’re going to have some thaws. We know it’s going to probably rain at some point in December, January, and make us all cry,” DesLauriers said. “You just got to weather through it, and it’ll turn around, it’ll be all right. Usually it is.”

Despite its efforts, Bolton wasn’t able to make enough snow to open for Thanksgiving weekend.

But then, the weather started to cooperate. Temperatures dropped, and they got some real snowfall too, enough to open the first weekend of December.