NOAA's weather modification database is riddled with errors

Since the early 1970s, anyone conducting weather modification in the U.S. -- most commonly cloud seeding, which adds tiny particles to clouds to increase precipitation or suppress hail -- has been legally required to report it to NOAA, which is required to keep a public record.▸ Two GAO reports examine this system from different angles. A December 2024 report⧉ found that scientific estimates of how much extra precipitation cloud seeding actually produces range from 0% to 20%, partly because federal reporting requirements don't capture enough information to narrow that range. A February 2026 report⧉, which explicitly built on the first, examined NOAA's reporting database directly and found 78% of initial reports had at least one error -- and that NOAA has no written guidance for reviewing any of it.

Cloud seeding has been practiced in the U.S. since the 1940s, and recent advances in radar and sensor technology have made it precise enough to show effects under certain conditions.▸ As of July 2024, nine states -- California, Colorado, Idaho, Nevada, New Mexico, North Dakota, Texas, Utah, and Wyoming -- were actively running cloud seeding programs, almost entirely funded at the state level or below. Utah spends the most: $12 million in one-time funding approved in 2023, plus a $5 million annual budget. Ten other states have banned or considered banning cloud seeding or weather modification generally.

GAO reviewed the scientific literature on cloud seeding's effectiveness and found estimates of the additional precipitation it produces ranging from 0% to 20% -- a spread wide enough that GAO called it "difficult to evaluate the effects of cloud seeding due to limitations of effectiveness research."▸ Existing studies suggest silver iodide, the chemical most commonly used, doesn't pose an environmental or health concern at current levels of use, but nobody knows whether that holds at a larger scale. GAO identified federal reporting gaps as one specific driver of the uncertainty: the data collected isn't structured to support the kind of independent evaluation that could narrow those estimates.

Fourteen months after that first report, GAO went looking at NOAA's actual database to see how well it was doing its one legally required job: collecting and sharing complete, accurate weather modification reports.▸ NOAA's online database held 1,084 files as of February 2025. GAO sampled 111 of them and found the database to be incomplete, inconsistent, and unreliable -- 78% of initial reports had at least one error, and even interim and final reports, which have fewer requirements, had errors 21% of the time.

The maps were often just as bad.▸ Every initial report is required to include a map showing the target and control areas of the operation -- information operators and researchers could use to estimate costs, effectiveness, and whether an area had already been seeded. GAO found 32% of initial reports were missing a map entirely, and another 36% had maps with at least one missing component. That leaves roughly a third of reports with a complete, accurate map.

Some activity never made it into the database at all.▸ GAO reviewed state agency websites describing weather modification activity from 2021 through 2025 and found that 4 of 10 states had publicly reported activity that never appeared in NOAA's records. Two operators GAO interviewed even produced emails and other evidence of reports they said they'd submitted, which GAO couldn't locate in the database. The earliest complete report NOAA could find on file dated to 1999 -- even though, per GAO, the reporting requirement itself took effect in 1971; NOAA officials said records from before the database went digital in 2019 may simply have been lost.

NOAA told GAO it interprets its job as maintaining a public database for transparency, not conducting broader oversight of the activities themselves.▸ In practice, GAO found NOAA doesn't check reports for scientific accuracy, doesn't proactively search for operators who never file, and has never once imposed the fine the law allows for willful non-reporting. The office that reviews reports doesn't even host the database -- it hands reports off to the NOAA Library each quarter, with no written agreement covering how the process should work or how long records need to stay available.

The gaps extend to an emerging technology the 1972 law never anticipated: solar geoengineering, which aims to cool the planet at a regional or global scale rather than boost local rainfall.▸ NOAA's reporting forms, unchanged since 1974, require a map of a ground-based target and control area -- a requirement that made sense for a cloud-seeding operation over a specific mountain range, but that solar-geoengineering operators told GAO is nearly impossible to complete for activities like marine cloud brightening or stratospheric aerosol injection, which may have no fixed location or comparison area at all.

GAO made three recommendations: that NOAA write actual guidance for reviewing reports, improve its instructions for completing the forms (including for solar geoengineering), and start proactively telling operators and state and local agencies about its reporting requirements.▸ NOAA agreed with all three, while asking GAO to clarify that its authority covers the reporting itself, not oversight of the underlying weather modification activities.