Skiing touring up a mountain in the Wind River Range, one can see the sun peeking out from the clouds and snow everywhere. The skis make a squeaky sound in the hard, cold snow.
It’s possible that snow could’ve come from cloud seeding. That’s where scientists inject winter clouds, either by plane or from the ground, with a salt-like mixture. When it works, it puts a little more snow on the ground during a storm, about 10%.
Wyoming has cloud seeded for about two decades in the Wind River Range and Sierra Madres, and more recently, the Medicine Bow Range. Water managers across the Colorado River Basin consider it a “tool in the toolbox” for drought mitigation.
Basin users especially look to Wyoming as a headwater state and pioneer in cloud seeding. It’s a practice used by nine states, including Colorado, Idaho and Utah. But after this year’s legislative session, the Wyoming program’s future is uncertain.
Legislation whiplash
Cloud seeding costs Wyoming about $320,000 annually. Lawmakers always debate the price tag, but especially this year.
“You know I’ve enjoyed about 19 of these debates on cloud seeding. It’s always a joy,” Sen. Bill Landen (R-Casper) said with a chuckle on the Senate floor in late February.
A few days earlier, the House of Representatives voted to end Wyoming’s cloud seeding program. Landen was supporting a Senate amendment to bring it back. But it failed.
Three days later, a similar amendment surfaced. Sen. Bob Ide (R-Casper), who called himself a member of the “cloud seeding skeptic’s club,” spoke against it.
“This one, I keep trying to beat down, but it keeps coming back,” Ide said on the Senate floor with a deep sigh, followed by a little laugh.
After hours and days and weeks, lawmakers almost successfully nixed Wyoming’s whole program. And Wyoming wasn’t alone. This year, 14 other states had similar legislation, according to Louisville Public Media reporting. Tennessee fully banned the practice in 2024.
Ultimately, Wyoming’s cloud seeding survived – kind of. The state stripped its funding and will only continue ground-based operations – no more seeding from planes, which included the Medicine Bow Range.
“I found it very frustrating,” said University of Wyoming (UW) atmospheric science associate professor Jeff French. He’s one of the lead researchers in cloud seeding. “I didn't necessarily feel that the decisions were being made based on the best science and the best information that we have at hand.”
Debates of fears and science
One concern that kept coming up this session: Is cloud seeding safe?
That’s what spurred a separate bill that would’ve outlawed atmospheric geoengineering in Wyoming, including cloud seeding. The bill eventually failed, but not before Shelta Ramber of Sheridan spoke to a House committee in support of the ban.
Ramber was worried about contrails, the white lines in the sky that trail behind planes. She referred to them as “chemtrails.”
“I, for one, get more migraines when the white lines become man-made clouds above me,” Ramber said.
“Chemtrail” conspiracy theorists generally believe the government is spraying chemicals in the sky to control people’s minds and hurt their health. It’s been debunked. However, the idea surfaced in much of the anti-cloud seeding legislation across the country this year.
UW professor French said he understands the confusion with contrails. Sometimes they stick around all day, sometimes they evaporate in 10 minutes. The science is actually quite complicated.
“I ask my PhD graduate students to be able to explain that, because it is not intuitively obvious by any stretch of the imagination,” French said.
On the most basic level, the white lines are the mixing of warm aircraft exhaust with cold atmosphere air. How long the lines stick around depends on the relative humidity.
“It truly is a natural atmospheric phenomenon,” he said.
As for health and environmental impacts? The main ingredient used for cloud seeding, and not found in your typical aircraft exhaust, is silver iodide. French said people sometimes confuse it with silver, which is toxic. But when bonded with iodide, research shows it’s pretty harmless, even more so in the small amounts used for cloud seeding – a few grams. In fact, silver iodide is used as an antiseptic in medicine and for sterilizing drinking water.
“I'm a pretty strong environmental proponent,” French said. “If I felt like there was any type of concern, I would certainly be one of the people pounding the drums.”
Instead, pounding the drums was Rep. Mike Schmid (R-La Barge). He led the charge to axe the cloud seeding program through an amendment to a water funding bill. He specifically homed in on two other concerns.
“Bighorn sheep and the once massive glaciers in the Wind River Range, and we’re losing them both,” Schmid said on the House floor.
However, French said no science connects cloud seeding with the decline of bighorn sheep or glaciers.
“Glaciers are receding all over the place and in a lot of places where there's no cloud seeding going on,” he said.
French added that cloud seeding is not completely changing weather, it’s maximizing on storms that are already brewing. Also, it’s not preventing the clouds from producing moisture elsewhere.
“Water cycling in the atmosphere occurs very fast,” he said. “What happened to occur upstream in the mountains really has little to no impact [elsewhere].”
Another talking point among lawmakers was there’s simply not enough proof that cloud seeding works. It’s true that researchers are still trying to nail down how effective it is, but whether it puts more snow on the landscape? There’s little debate in the science community.
Partner states
Andrew Rickert, who heads up Colorado’s cloud seeding program, said decades of research resoundingly shows it does work. In fact, much of it is Wyoming’s own research.
“They flew a plane through a cloud, and as the plane flew through, it zigzagged while it released the solution,” Rickert said. “And you could see the precipitation forming – the snowflakes forming – in that zigzag pattern.”
Rickert added it was “total evidence that cloud seeding does work.”
That kind of research helped justify Rickert’s program, especially in times of drought.
“It's one of the tools we have, and it's the only tool that actually adds water,” he said.
Which downstream Colorado River Basin users care a lot about, including the 2.3 million people in the greater Las Vegas, Nevada area.
“What really matters in terms of drought for my community is not the rain that’s falling here,” said Colby Pellegrino, deputy manager for the Southern Nevada Water Authority. “It’s how much snowpack we have occurring in the Rockies.”
Pellegrino said her group pitches in about $160,000 annually for cloud seeding in the Rockies.
“[It’s] one low-cost way to help deal with this exceptionally long drought that we’re in,” she said. “By most standards, it’s called a mega-drought at this point.”
Arizona and California help pay too. It’s actually part of the 2019 Colorado River Basin Drought Contingency Plan, which expires next year.
But whether those lower Basin states will help foot Wyoming’s portion of the bill, about $320,000? It’s too soon to say.
Those negotiations will happen over the coming months. If they opt out, Wyoming’s two-decade-long cloud seeding program likely won’t happen next winter.
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