How Cold War-era dreams of weather modification are coming true in Colorado’s ski country

Jack Queen
Eric Hjermstad of Western Weather Consultants with cloud seeding equipment. Eric's father, Larry, pioneered cloud seeding in the 1970s.
Hugh Carey / |

Larry Hjermstad is a pioneer of cloud seeding, so naturally he has some frontier tales.

Back in the 1970s, farmers in the San Luis Valley stalled his efforts to set up the area’s first seeding operation, which aimed to increase precipitation by spraying dust into the skies.

Wary of what he was up to, they blew up his radar dishes and shot at airplanes, Hjermstad recalled.

“They said, ‘We’re not sure you know what you’re doing,'” he said. “So I set up a committee, and told them, ‘Before each seeding, I’ll tell you exactly what I’m going to do.’ After the third one they said, ‘You don’t have to call us anymore.'”

Hjermstad and his company, Western Weather Consultants, now run cloud seeding programs across the state, including in Summit County.

For decades, local ski areas have paid him to send plumes of silver iodide up to their slopes when opportune storms approach, squeezing out a couple of extra inches of snow each time.

In recent years, however, water managers on the Front Range and even states further down the Colorado River have started to pitch in some of the $250,000 to $300,000 it costs to run the program in the Summit County area, hoping the extra snow will flow into their water system when it melts.

Here, in the Central Colorado Mountains River Basin, the company operates about 36 cloud seeding generators. They’re small, almost homebrew-looking devices that burn a solution of inert silver iodide and send it into the atmosphere.


Some of the generators are on private land, and when Western Weather Consultants detects an optimal storm coming, it sends instructions to the landowners to fire them up. It varies, but Hjermstad says the process can boost snowfall by as much as 25 percent.

“If we were able to do this over the entire state with all of the mountain ranges, we could add the (water) equivalent of one entire river,” he said.

So why aren’t they?

“Because there are still people that are skeptical.”

Snake oil or science?

The concept of cloud seeding has been around since the 1940s, when Bernard Vonnegut (brother of author Kurt) discovered that silver iodide could produce ice crystals when introduced into cloud chambers.

In those heady days, cloud seeding was heralded as a way to produce rain where there was none, boosting crop yields and filling reservoirs to the brim.

That was a wild overstatement, and cloud seeding’s reputation suffered for it.

“Back in the early days there were a lot of snake oil people who were claiming like 100 percent increases in snowfall, so I think the problem is that it was oversold for a long time,” said Frank McDonough, an atmospheric scientist at the Desert Research Institute in Nevada.

Studies in Australia and Israel have debunked the idea that airplanes spewing silver iodide willy-nilly will do much of anything. But a targeted approach that hits the right clouds at the right time high in the mountains has gained scientific currency in recent years.

“Most of the research programs have estimated that you can get around 10 percent (increases),” McDonough said. “Some storms you can get 25 percent and other storms you get zero.”

The increases can be modest — an extra inch during a ten-inch storm — but over the course of a season that adds up to several extra feet.

One cloud seeding operation in the Tahoe area provides the annual water needs of about 10,000 homes, a several million-dollar value produced for pennies on the dollar, McDonough said.

Resorts to reservoirs

Not every cloud can be seeded, and the process is as much art as science. The ideal targets are warm clouds where there’s plenty of liquid water floating around at freezing temperatures that doesn’t have any particles to latch onto.

On a cold day on the ski slopes when a cloud is hovering on the mountain, you can see evidence of this in the ice that forms on objects.

“If you go up to the top of A-Basin after a storm, you should see white ice that has grown on the lift towers and in the trees,” McDonough explained. “What’s happening there is the water drops are floating around in the cloud and as soon as they hit a structure, that structure serves as a spot for a freezing event. With cloud seeding, what you’re doing is throwing some dust up in the cloud and creating the freezing in the cloud.”

In other words, if you see ice forming on towers while skiing this season, it means there could’ve been a missed opportunity to turn that into some extra powder.

Vail Mountain, which has contracted with Hjermstad for more than 40 years, hasn’t missed any of those chances for extra snow, he said.

“Some storms they would get 18 inches and everybody else would get 12,” he said.

Breckenridge Ski Resort, Keystone Resort and Winter Park Resort are all sponsors of the Summit-area program. But snow that’s good for skiing is good for drinking later down the line, and Front Range water managers have taken notice.

“Over time, there has been a lot more interest in weather modification programs in the state of Colorado,” said Maria Pastore of the Colorado River District. “We’re really excited to get into the sixth season (of cloud seeding) … the primary objective for the sponsors is to increase the water supply in the Upper Colorado River Basin.”

Western Weather Consultants claims that its two seeding operations in the High Country generate between 180,00 and 300,000 added acre-feet of water per year, and that has been backed up by independent studies.

An outside evaluation of the Vail operation from 1977 to 2005 found statistically significant snowfall increases ranging from 6.3 to nearly 29 percent.

“With time, people have become more comfortable that the process is actually doing what it says it does,” Hjermstad said. “Why would Vail keep us on for 45 years straight unless they didn’t see something?”

Support Local Journalism

Support Local Journalism

As a Summit Daily News reader, you make our work possible.

Summit Daily is embarking on a multiyear project to digitize its archives going back to 1989 and make them available to the public in partnership with the Colorado Historic Newspapers Collection. The full project is expected to cost about $165,000. All donations made in 2023 will go directly toward this project.

Every contribution, no matter the size, will make a difference.