Cloud Seeding — What Is It and Should You Be Concerned?

Cloud seeding is a documented weather modification practice in which aircraft or ground-based generators disperse substances like silver iodide into clouds to trigger precipitation, and it has been used operationally by governments in over 50 countries since 1946.

What Is Cloud Seeding?

Cloud seeding is a form of weather modificationin which substances are dispersed into the atmosphere to alter the development of clouds and influence precipitation. The technique was discovered in 1946 by Vincent Schaefer, a chemist at General Electric's research laboratory in Schenectady, New York. Schaefer found that dropping dry ice (solid carbon dioxide) into a supercooled cloud chamber caused ice crystals to form almost instantly. Shortly after, his colleague Bernard Vonnegut discovered that silver iodide had a crystalline structure nearly identical to natural ice, making it an even more practical seeding agent.

Since those early experiments, cloud seeding has grown into a global industry. The World Meteorological Organization tracks active weather modification programs in over 50 countries, and private companies conduct seeding operations on behalf of governments, agricultural interests, water authorities, and even ski resorts seeking to boost snowfall. The technology has evolved from simple dry-ice drops to sophisticated delivery systems using specialized aircraft, ground-based generators, and rocket-launched canisters.

How Cloud Seeding Works

The basic principle of cloud seeding is straightforward: introduce particles into a cloud — typically using approximately 10 to 50 grams of silver iodide per hour of operation — that act as condensation or ice nuclei. Water vapour in the atmosphere needs something to condense onto — a dust particle, a salt crystal, or an artificial seeding agent. By introducing additional nuclei, cloud seeding aims to increase the number of ice crystals or water droplets that form, which can then grow heavy enough to fall as precipitation.

There are two primary approaches:

• Glaciogenic seeding — targets cold clouds (below 0°C) with agents like silver iodide or dry ice that promote ice crystal formation. This is the most common method, used to enhance snowfall or rainfall from winter storm systems and convective clouds.
• Hygroscopic seeding — targets warm clouds with salts (sodium chloride, calcium chloride, potassium chloride) or other hygroscopic materials that attract water vapour and promote the growth of larger droplets. This method is used in tropical and subtropical regions where cold cloud processes are less dominant.

Aircraft used for cloud seeding are typically twin-engine turboprops — models like the Beechcraft King Air and the Piper Cheyenne are common. These planes carry wing-mounted generators or underwing flare racks that release seeding agents directly into targeted cloud formations, typically operating between 2,000 and 6,000 metres — well below the 10,000–12,000 metre cruising altitude where commercial jets fly through air as cold as −55°C. Some operations use ground-based silver iodide generators positioned in mountain valleys, relying on natural updrafts to carry the particles into cloud systems above.

Cloud Seeding Chemicals

The substances dispersed during cloud seeding operations vary by program and method. The most widely used agents include:

• Silver iodide (AgI) — the most common seeding agent worldwide. Its crystal structure closely matches natural ice, making it highly effective at triggering ice nucleation. Silver iodide is typically burned in acetone solutions using airborne or ground-based generators.
• Potassium iodide (KI) — often used alongside silver iodide in composite seeding flares. It serves as an additional nucleation agent in complex cloud systems.
• Dry ice (solid CO₂) — the original seeding agent. When dropped into supercooled clouds, it lowers the local temperature below −40°C, causing rapid ice crystal formation. Less commonly used today due to logistical challenges, but still employed in some research programs.
• Hygroscopic salts — sodium chloride (table salt), calcium chloride, and potassium chloride are used in warm-cloud seeding operations. These salts attract water vapour and promote the coalescence of larger droplets.
• Liquid propane — used in some ground-based seeding systems. When released into cold air, propane expands and cools rapidly, creating ice nuclei.

What Does Cloud Seeding Look Like?

From the ground, cloud seeding activity can be difficult to distinguish from normal aviation unless you know what to look for. Here are the key visual indicators:

• Unusual flight patterns — seeding aircraft often fly in racetrack patterns, repeated passes, or tight circles through cloud formations. This differs from the straight-line routes of commercial aircraft.
• Lower altitude operations — cloud seeding aircraft typically operate between 2,000 and 6,000 metres, well below the 9,000–12,000 metre cruising altitude of commercial jets. If you see a smaller aircraft flying at a notably lower altitude than nearby airliners, it may be conducting seeding operations.
• Flare trails — some seeding aircraft release pyrotechnic flares from underwing racks. These can occasionally be visible as brief streaks or glowing points beneath the aircraft, particularly at dawn or dusk.
• Rapid cloud development — after seeding, clouds in the target area may visibly thicken, darken, or begin producing precipitation within 30–90 minutes. If you observe a sudden increase in cloud density following aircraft activity, seeding may have occurred.
• Contrails vs seeding trails — normal contrails form at high altitudes in cold, humid air and may persist for minutes to hours depending on conditions. Trails from seeding aircraft at lower altitudes may appear different in colour, density, or behaviour. A persistent trail from an aircraft at an altitude where contrails should not form is worth investigating.

Where Is Cloud Seeding Happening?

Cloud seeding is far more widespread than most people realize. Here are some of the most significant active programs:

• United States — Texas has operated cloud seeding programs since the 1970s, with multiple operational areas across the state. Wyoming's Pilot Project ran from 2005 to 2014, showing a 5–15% increase in snowpack. Colorado, Idaho, Utah, North Dakota, and California all fund active seeding programs. Companies like Weather Modification International (Fargo, ND) conduct operations across the country.
• China— China operates the world's largest weather modification program, with a stated goal of influencing weather across 5.5 million square kilometres by 2025. The program employs over 35,000 personnel, uses dedicated aircraft fleets, and deploys thousands of ground-based rocket launchers and generators across the country.
• United Arab Emirates — the UAE Rain Enhancement Program has invested over $20 million in research and conducts regular seeding flights. The UAE has also funded research into advanced seeding technologies, including electric-charge-based methods developed in collaboration with the University of Reading.
• Russia— Russia has used cloud seeding operationally for decades. The Russian military and civilian agencies conduct seeding to ensure clear weather for national events, reduce hail damage to crops, and influence precipitation patterns.
• India, Thailand, Indonesia — these countries operate cloud seeding programs to address droughts, manage monsoon patterns, and combat air pollution. Thailand's Royal Rainmaking Project has been active since the 1950s.

Negative Effects of Cloud Seeding

While proponents present cloud seeding as a safe and beneficial technology, significant concerns have been raised by researchers, environmentalists, and affected communities:

Environmental and Health Concerns

• Silver iodide accumulation — studies have detected elevated levels of silver in soil, water, and snow in areas with long-running seeding programs. A 2016 study in the Journal of Environmental Monitoring found measurable silver iodide residues in snowpack downwind of seeding sites. While individual operations release small quantities, the cumulative effect of decades of continuous seeding is not well understood.
• Ecosystem disruption — altering precipitation patterns in one area can have downstream effects on water tables, river flows, and ecosystems that depend on natural rainfall cycles. Fish populations, soil microbiomes, and plant communities can all be affected by changes in when, where, and how much rain falls.
• Unknown long-term health effects — the long-term health effects of inhaling trace amounts of silver iodide and other seeding agents have not been comprehensively studied. While silver iodide is classified as having low acute toxicity, there is limited research on chronic exposure through drinking water and respiration in communities near seeding operations.

Weather and Climate Concerns

• Robbing rain from neighbours — one of the most persistent criticisms of cloud seeding is the "rain stealing" problem. If you seed clouds upwind of your region and cause them to precipitate, communities downwind may receive less rainfall. This has led to legal disputes, particularly in the western United States, and raises serious ethical questions about who has the right to modify shared weather systems.
• Flash flooding risk — poorly timed or excessive seeding can contribute to unexpectedly heavy rainfall. In 2024, Dubai experienced severe flooding following heavy rain, with cloud seeding operations reported in the region. While the UAE government stated that no seeding flights took place on the day of the flooding, the incident intensified public debate about the risks of weather modification.
• Unpredictable outcomes — weather systems are complex and nonlinear. Even with modern modelling, the exact effects of introducing seeding agents into a cloud system cannot be predicted with certainty. The atmosphere does not respect political boundaries, and interventions in one area can trigger cascading effects across wider regions.

Transparency and Accountability Concerns

• Many cloud seeding programs operate with limited public disclosure. In the US, reporting requirements vary by state, and there is no federal mandate requiring real-time public notification of seeding operations.
• Citizens living in areas where seeding takes place often have no say in whether operations are conducted over their communities. The question of informed consent for weather modification remains largely unaddressed.
• Environmental impact assessments for cloud seeding programs are inconsistent. Some programs operate for years without comprehensive independent review of their ecological effects.

“According to ChemTracker's atmospheric analysis engine, cloud seeding aircraft operate at altitudes and in flight patterns that are clearly distinguishable from commercial aviation — making real-time ADS-B tracking one of the most effective tools for identifying seeding operations in your area.”

Is Cloud Seeding the Same as Chemtrails?

Cloud seeding and chemtrails are related but distinct concepts in public discussion. Cloud seeding is an acknowledged, documented practice with known agents, identified aircraft, and (in many cases) publicly available operational records. The term chemtrails is typically used to describe a broader concern: that aircraft are releasing undisclosed substances into the atmosphere beyond what official weather modification programs account for. For a detailed breakdown of the specific substances claimed by chemtrail researchers, see our Dutch-language investigation “Wat Sproeien Ze?”.

What makes this distinction complicated is that the line between the two is not always clear. When a government operates cloud seeding flights without real-time public notification, and citizens observe aircraft leaving unusual trails, the practical difference between "cloud seeding" and "chemtrails" becomes a matter of transparency, not technology.

ChemTracker does not make claims about what is or is not in the trails you see. Instead, it provides the datayou need to investigate for yourself: aircraft identifiers, real-time positions, flight altitudes, atmospheric conditions, and trail formation predictions. Whether you are interested in documented cloud seeding operations or investigating trails that do not match official explanations, the starting point is the same — knowing exactly what is flying overhead and under what conditions. Learn more about geoengineering and weather modification.

Track Aerial Activity in Your Area

If you want to know what aircraft are operating above your community, you no longer have to guess. ChemTrackeruses real-time ADS-B transponder data to show you every aircraft in your area — commercial jets, private planes, military transports, and yes, aircraft that match the profiles used in cloud seeding operations.

The app overlays live atmospheric data so you can see temperature, humidity, and pressure at the altitude each aircraft is flying. This lets you determine whether the conditions support normal contrail formation — or whether the trails you see require a different explanation.

You can point your phone at the sky and see overlaid flight information in real time. Set up alerts to be notified when aircraft activity in your area matches patterns of interest. Build your own observations with real data, not speculation.

Frequently Asked Questions