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Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Cloud seeding adds particles to suitable clouds that already contain the moisture and structure needed for precipitation. It may increase precipitation under specific conditions, but it cannot make rain clouds from clear skies, control weather at will, or steer hurricanes. The clearest evidence described by the World Meteorological Organization concerns wintertime seeding of certain mountain clouds—not every cloud type or location.
How cloud seeding works
Clouds contain tiny liquid droplets, ice crystals, or both. Cloud seeding disperses particles into a suitable cloud to influence how those droplets or crystals form and grow. The particles do not supply water: the cloud must already have the right moisture, temperature, and structure.
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Glaciogenic seeding: encouraging ice formation
Glaciogenic seeding uses agents such as silver iodide in clouds containing supercooled liquid water—water that remains liquid below freezing—or a mix of liquid water and ice. The aim is to increase ice-crystal formation and precipitation through ice-phase processes. In winter mountain clouds, moist air rises over terrain, and seeding may target clouds already containing supercooled water. Material can be released by ground generators into air flowing toward the cloud or dispersed from aircraft.
Hygroscopic seeding: affecting liquid droplets
Hygroscopic seeding targets liquid-phase clouds. It adds particles intended to affect the number and size of droplets, potentially promoting collision and coalescence—the process by which droplets merge and grow. Convective clouds vary naturally, which makes it particularly difficult to distinguish a seeding effect from what would have happened anyway.
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Neither method can create the necessary cloud system from clear sky or import missing water vapor. The World Meteorological Organization (WMO) explains that weather systems contain too much energy for weather-modification methods to create raining cloud systems, redirect winds to bring water vapor into a region, or eliminate severe weather. WMO’s statement on weather modification sets out this basic limit.
What the evidence says about added precipitation
The strongest evidence described by WMO is for wintertime glaciogenic seeding of orographic clouds—clouds formed as air rises over terrain—that contain supercooled liquid water or mixed phases. WMO reports progress in this specific area and evidence-based causal findings for the method. It also describes statistical and physical evidence of enhancement in some orographic clouds and in some frontal clouds containing supercooled water.
That finding is conditional, not a forecast of what any program will achieve. Results depend on natural cloud characteristics; a result in one trial or environment cannot simply be transferred to another. Some historical experiments also did not match their original hypothesis. WMO summarizes the distinction plainly: “Results from one trial cannot be directly applied to a different environment.”
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchA U.S. Government Accountability Office (GAO) review published in December 2024 found that estimates of additional precipitation in the studies it reviewed ranged from 0 to 20 percent. This is a range across reviewed studies, not a guaranteed operational yield or a universal estimate. GAO also noted that effectiveness is difficult to evaluate, evidence on effectiveness has limitations, and precipitation can be enhanced only when suitable clouds are present. See GAO-25-107328.
Why a claimed success can be hard to prove
Rain and snow vary naturally, so a wet period after seeding does not by itself establish that seeding caused the precipitation. A persuasive evaluation needs a design that can separate seeded from unseeded events, objective rules for choosing eligible events, statistical comparisons with uncertainty, and physical analyses that support the proposed mechanism. WMO identifies randomization as important for statistical evaluation and recommends connecting statistical results with physical evidence. A radar image or a single wet season alone is not proof of an effect.
What cloud seeding cannot do
It cannot create storms or control weather at will
Seeding cannot manufacture a rain-bearing cloud system from clear skies, redirect winds to bring moisture into a region, or make a storm behave as desired. It is an intervention in suitable existing clouds, not a general-purpose weather-control technology.
It cannot steer or stop hurricanes
There is no generally accepted evidence that cloud seeding can modify tropical cyclones. NOAA says no technology exists to create, destroy, modify, strengthen, or steer hurricanes. Its fact check also clarifies the agency’s role: “NOAA does not modify the weather, nor does it fund, participate in or oversee cloud seeding or any other weather modification activities.” Read NOAA’s fact check on weather-modification claims.
It is not a demonstrated way to prevent other severe weather
WMO reports no demonstrated cloud-seeding method for tornadoes, lightning danger, floods, or other severe-weather phenomena. Hail suppression is practiced in some regions, but WMO says experiments have not convincingly established its scientific basis because hailstorms are energetic, dynamic, and naturally variable. It also reports no demonstrable result from attempts to seed hailstorms with hygroscopic nuclei. These claims should not be treated as proof that seeding reliably prevents hail damage.
Local cloud seeding is also distinct from solar geoengineering, which concerns larger-scale climate effects over longer timescales; the two should not be conflated.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Is cloud seeding safe?
WMO says published studies have not found significant human-health or environmental effects from silver iodide and other commonly used agents in past operations. That is not proof of harmlessness at any quantity. WMO recommends evaluating proposals involving substantially greater amounts or a new agent, and says potential downwind, environmental, and ecological effects need more investigation. GAO likewise describes the evidence as limited and says the effects of much more widespread silver iodide use are unknown.
Who operates and oversees cloud seeding in the United States?
Programs are generally operational efforts run by state, local, or private entities—not NOAA weather-control programs. NOAA says it neither conducts nor funds cloud seeding and has no authority to regulate it. Under the Weather Modification Reporting Act of 1972, U.S. operators must report intended weather-modification activity.
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Those filings are useful for identifying reported activity, but they are not necessarily complete or error-free. In a February 2026 review, GAO said NOAA was not fully meeting responsibilities to maintain and share reports and estimated that over half of reports filed with the agency likely contained errors, including missing required information. GAO said its recommendations on review guidance, reporting instructions, and outreach remained open in the report summary. Details are in GAO-26-108013.
Counts also need dates attached. GAO’s December 2024 assessment said nine U.S. states were using cloud seeding and ten had banned or considered banning cloud seeding or weather modification at that time; these are not current counts. WMO’s statement dated June 2025, updated in July 2026, reports operational weather-modification programs in more than 50 countries. The presence of a program does not establish that it achieves its stated goals. WMO says it “neither promotes nor discourages the practice of weather modification.”
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