JACKSON, Wyo. — At the end of August, the Wyoming Joint Agriculture, State and Public Lands & Water Resources Committee held a meeting that ended with a vote in favor of drafting legislation to place a 10-year moratorium on cloud seeding in the state. Wyoming’s closest ground-based generators are located on the west side of the Wind River Range, and Idaho Power owns two generators on private property in Star Valley that are at risk of being shut down if the legislation passes.
The potential legislation, put forth by Rep. Mike Schmid (R-La Barge), would ban the practice of weather modification in Wyoming for one decade starting July 1, 2026; prohibit unauthorized seeding and establish penalties of up to $50,000 per occurrence; and require a preliminary report to be due in Oct. 2036 and a final report due in Dec. 2037. Schmid named the proposal the “Wyoming Cloud Seeding Moratorium and Baseline Act.”
Cloud seeding is the process of infusing certain storm clouds with silver iodide — a nonorganic, nontoxic chemical compound with the same molecular structure as ice — either from the air or from ground-based generators, in order to promote the development of more precipitation than the cloud would otherwise drop.
Some of the nine stakeholders who testified at the Aug. 28 hearing brought up concerns about possible environmental and health effects of cloud seeding, though experts in the field routinely say that there are no significant impacts. Also discussed was the efficacy of the practice, which can have varying results in different conditions. Most scientists agree that it is challenging to quantify the effectiveness and benefits of cloud seeding, though it is widely believed to be worth the cost.
“In my mind, there can’t be any real answers unless we have a true established baseline to go from,” Schmid said at the hearing when introducing his draft bill. “And the only way we’re going to get a true established baseline is to stop the practice and let Mother Nature do this for 10 years.”
At the end of the hearing, which lasted four hours, the committee voted to have the Legislative Service Office draft a bill to introduce at the next joint committee meeting on Oct. 28 and 29. A few members of the committee voted against drafting a bill, with some arguing that it was simply happening too fast. The bill draft would still have to clear many hurdles before making it to the governor’s desk.
In February, during the 2025 Wyoming Legislative Session, all state funding for ground and airborne cloud seeding programs was eliminated. Ground-based operations are still authorized as of now, provided the funding comes from “other Colorado River users and interested parties,” according to House Bill 0117, which presumably means other state and municipality stakeholders in the Colorado River Basin. There has been no decision yet as to whether ground-based operations in Wyoming will continue this winter. The state has 10 ground-based generators spaced out around the the Wind River Range, with nine in the area from New Fork Lakes down to Farson, and one near Lander. There are also two generators near the Sierra Madre Mountains in south-central Wyoming.
A 2024 Government Accountability Office (GAO) report on cloud seeding technology stated that nine states have cloud seeding programs, including California, Colorado, Idaho, Nevada, New Mexico, North Dakota, Texas, Utah and Wyoming. The report highlighted the benefits of cloud seeding, such as bolstering water supply and increasing recreational opportunities like skiing and river rafting. A 2017 article in Jackson Hole Magazine tells the story of the 1976 drought, when Jackson Hole Ski Area owner Paul McCollister resorted to cloud seeding at the cost of $4,000 per week.
University of Wyoming (UW) Atmospheric Science Department Head Jeffrey French told Buckrail that he is “perplexed” at the committee’s decision to go in the direction of a moratorium. French worked in an advisory capacity to the state during the early years of Wyoming’s cloud seeding program. He was one of four experts to testify on the topic of weather modification before the joint committee last month. He thought the experts demonstrated very strongly that there are no negative environmental or health concerns related to cloud seeding.
“I’m a pretty strong environmental advocate and health advocate,” French said. “And if I was concerned that there were any type of significant environmental impacts, I certainly wouldn’t be involved in this type of research.”
According to the Wyoming Water Development Commission (WWDC) website, silver iodide is insoluble in water, which means it can be traced. Several studies, including some by the U.S. Environmental Protection Agency (EPA), have repeatedly demonstrated that cloud seeding contributes levels of silver iodide far below the levels considered safe by the EPA and environmental regulatory agencies in other countries.
French also believes that cloud seeding is a cost-effective tool for water and city managers to use, especially in the face of widespread drought across the western U.S.
“Based on our best estimates to date, the cost per additional acre-foot of water that would be produced through cloud seeding — especially for ground-based programs — is less than what the actual cost of water is in many of these communities,” French said. “From that standpoint, it makes financial sense to do this and to provide our water managers more flexibility.”
According to Idaho Power’s Atmospheric Scientist Derek Blestrud, the purpose of Idaho’s program is to increase electricity production from hydroelectric dams. Based on analyses that evaluate annual average benefits of cloud seeding, Idaho Power estimates that its operations across the state provide over 1 million acre-feet of additional water per year. An acre-foot is the amount of water it takes to cover 1 acre of land to a depth of 1 foot. In Idaho, 1 million acre-feet of water can generate enough hydropower to run roughly 74,000 homes.
Idaho Power operates airborne cloud seeding in the Upper Snake River Basin, northwest of the Teton Range. According to Blestrud, it takes about 20 to 30 minutes for snowflakes to grow as a result of the seeding, and the snow always falls downwind of where the seeding takes place. It’s likely that the Teton Range sees some of the snow from Idaho’s operations before it melts into the Snake River, gets used for irrigation purposes, then is transformed into hydropower.
The two ground-based generators that Idaho Power owns in Star Valley are on land leased from private landowners very close to the Idaho border. According to Blestrud, the runtime of each generator can vary widely depending on storm locations and weather variability. On average, the generators operate between 70 and 90 hours per season, which runs from Nov. 1 through April 30. Idaho Power reports to the Wyoming State Engineer’s Office regarding the generators, per Wyoming state law.
In 2004, Wyoming conducted a 10-year pilot study on the viability and efficiency of cloud seeding technology over Wyoming mountain ranges. As a result of the positive conclusions from Wyoming’s Weather Modification Pilot Study, the state began cloud seeding operations over the Wind River Range in 2014. UW’s Atmospheric Science Department has researched and experimented with cloud seeding dating back to the 1960s.
French said that the questions and uncertainty about the efficacy of cloud seeding will not get answered by banning the practice.
“The way to answer the questions is to invest in research and design good experiments so we can better understand what the capability and limitations of cloud seeding actually are.”
