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A geomagnetic storm is hitting Earth right now. NOAA's Space Weather Prediction Center confirmed G1 (minor) geomagnetic storm conditions through Wednesday after fast solar wind from a large coronal hole slammed into Earth's magnetic field — bringing the planet's Kp index to 5 by 00:30 ET today. Solar wind speeds are forecast to peak near 700 km/s (435 mph), more than twice the average baseline, as detailed in TechTimes' July 20 coronal hole forecast. For anyone living near the Rocky Mountains or Hudson Bay, that storm is not just a light show. According to the most comprehensive statistical study ever conducted on this question, it is also quietly cutting your rainfall.
What Decades of Storm Data Reveal About Rain Near the Rockies
The finding comes from Joachim Raeder, professor emeritus of physics at the University of New Hampshire, in a peer-reviewed study published in Geophysical Research Letters earlier this year. Raeder assembled two parallel datasets at hourly resolution across 67 years: the Disturbance Storm Time index, or Dst, which tracks geomagnetic storm intensity by measuring hourly fluctuations in Earth's magnetic field at four equatorial observatories, and ERA5, the European Centre for Medium-Range Weather Forecasts' fifth-generation atmospheric reanalysis. ERA5 covers 137 atmospheric levels from the surface to 80 km (50 miles) altitude and became available at full hourly resolution across the historical record only recently — a technical development that made Raeder's analysis possible for the first time.
The result was a set of statistical weather maps spanning the entire North American continent. When a geomagnetic storm arrived — measured as a significant dip in the Dst index — the atmosphere responded measurably in the hours and days that followed. The most consistent signal: rainfall and snowfall declined across the Hudson Bay region and the Rocky Mountains in the western United States. The stronger the storm, the steeper the drop.
"We've long understood that the Sun influences our atmosphere over its roughly 11-year cycle — it's subtle, but it's there," UNH's Raeder said. "What's exciting is that we're now seeing a much stronger, short-term impact — happening within a single day of a solar storm."
The finding is not uniform. Seasonality matters sharply: storms arriving in summer or winter suppress precipitation more forcefully than those arriving in spring or fall. The storm that hit North America on July 4 of this year — a G3 event that reached two levels above NOAA's original G1 forecast — struck in summer, placing it in the category Raeder found most likely to reduce rainfall over the affected regions.
How a Disturbance in Space Gets Into a Rain Cloud
The part Raeder's study cannot yet confirm is the specific physical pathway — how a disturbance in Earth's magnetic field translates into fewer raindrops over Wyoming or Manitoba. But the data point clearly toward one hypothesis over another.
The leading candidate runs from the top of the atmosphere down. When a geomagnetic storm intensifies, energetic particles precipitate into the polar mesosphere — the atmospheric layer between roughly 50 km (31 miles) and 90 km (56 miles) altitude. Those particles catalytically destroy ozone there, altering heating rates and perturbing the polar mesosphere's temperature profile. That perturbation propagates down into the stratospheric polar vortex: the large ring of cold air and powerful westerly winds that encircles the poles, strongest in winter. When the vortex is destabilized, the disruption can travel further downward into the troposphere — the lowest atmospheric layer, where weather forms and precipitation falls.
This is the same general pathway that governs sudden stratospheric warming events, which occur when planetary waves from the troposphere disrupt the polar vortex, triggering a dramatic stratospheric temperature rise that then propagates downward over weeks, altering jet stream behavior and surface weather patterns across North America and Eurasia. A 2025 study published in Nature Communications found independent evidence that energetic particle precipitation from solar events can rapidly deplete ozone in the polar mesosphere, initiating this type of downward dynamic coupling.
Here is where Raeder's finding opens an unresolved scientific puzzle. Classic stratospheric warming-triggered surface weather responses typically take two to six weeks to propagate from the stratosphere to the troposphere. Raeder's data show precipitation changes within 24 hours of a geomagnetic storm's arrival. If the polar vortex pathway is responsible, it is operating on a timescale significantly faster than what classical stratospheric-troposphere coupling would predict. That discrepancy is not a flaw in Raeder's analysis — it is a genuine unknown that current atmospheric models cannot explain, and it is precisely why the mechanism remains unproven.
The alternative hypothesis — that solar storms affect weather by modulating galactic cosmic ray flux, which in turn changes cloud condensation nuclei and cloud cover — fit Raeder's data less well. This is notable given the long history of the cosmic ray cloudiness hypothesis (proposed by Svensmark and Friis-Christensen in the 1990s) as a candidate explanation for solar-climate links. Raeder's result does not rule it out definitively, but it strengthens the case for the top-down polar vortex pathway.
"Like many other studies on the same topic, I cannot provide the ultimate answer," Raeder said, "but my results narrow down the list of possible physical processes, and in particular, challenge the atmosphere models to reproduce these solar effects on weather."
One Finding That Reframes 100 Years of Solar-Climate Research
Perhaps the most significant implication of Raeder's analysis is conceptual, not atmospheric. For more than a century, researchers have observed statistical correlations between the 11-year solar sunspot cycle and various climate indicators — rainfall patterns, surface temperature anomalies, atmospheric pressure — and have attributed them to slowly varying changes in the Sun's total energy output.
Raeder's study suggests that picture may be inverted. The storm-linked weather effects he measured ran up to 100 times larger than the solar cycle's documented influence on global average surface temperature — though that comparison is deliberately illustrative, since the two figures measure different kinds of solar influence across different timescales and geographies. The more precise argument is this: those long-observed multi-year climate correlations may not reflect a slowly varying solar output at all. Instead, they may be the statistical accumulation of exactly the kind of discrete, short-duration storm events Raeder analyzed — many sharp pulses adding up, over years and decades, to what looks like a smooth cycle.
If that interpretation holds, it is a significant shift. It would mean climate models that account for solar variability by adjusting for the 11-year Total Solar Irradiance cycle are not just incomplete — they may be misidentifying the mechanism entirely. The real driver of solar influence on weather and climate may not be a slow drift in irradiance but a sequence of short, sharp geomagnetic kicks.
Every Weather Model in Operation Today Is Missing This Signal
Operational weather and climate models worldwide — including those run by NOAA's National Centers for Environmental Prediction and the European Centre for Medium-Range Weather Forecasts — do not currently include geomagnetic storm activity as a variable driving precipitation. Raeder's analysis provides, for the first time, a quantified empirical target: specific regional patterns over Hudson Bay and the Rockies, specific storm-intensity thresholds from the Dst index, and specific seasonal dependencies that a correctly formulated model should be able to reproduce, as highlighted by the American Geophysical Union's Eos magazine.
That target will eventually have sharper geographic resolution. ERA6 — the next-generation ECMWF reanalysis under development at roughly 14 km (9 miles) horizontal resolution compared to ERA5's 31 km (19 miles), with first data releases now expected toward the end of 2027 — could allow future analyses to identify more precisely which parts of the Rockies and Hudson Bay basin are most affected, and by how much.
The practical consequences of closing this gap are clearest in water resource management and agriculture. Drought forecasts, reservoir management, irrigation planning, and snowpack projections in the western United States all depend on accurate precipitation models. If a G3 summer storm consistently suppresses rainfall across the Rockies for 24 to 48 hours, that signal belongs in the forecast — and right now it is not there.
The Sun is currently near the peak of Solar Cycle 25, a cycle that has consistently exceeded its original activity forecast. The coronal hole responsible for today's G1 storm is the same one that recently passed around the far side of the Sun and returned to an Earth-facing position. As it continues its rotation, it is expected to produce recurrent high-speed stream events — another predictable category of geomagnetic disturbance that Raeder's findings now give atmospheric scientists new reason to track.
Frequently Asked Questions
How do solar storms suppress precipitation in the Rockies and Hudson Bay?
The leading hypothesis — supported by Raeder's 67-year statistical analysis — runs through the polar vortex, the large ring of cold air and fast westerly winds that encircles Earth's poles. When a geomagnetic storm deposits energetic particles into the polar mesosphere, those particles destroy ozone there, altering heating rates and destabilizing the stratospheric polar vortex. That disruption propagates downward into the troposphere — the atmospheric layer where rain and snow form — over hours to days. The process is similar in structure to the stratospheric warming events already linked to surface weather disruption, but it appears to operate on a much faster timescale than classic stratospheric-troposphere coupling, which normally takes two to six weeks. Why it operates so quickly remains an open question in atmospheric physics.
Does today's G1 storm mean less rain over the Rockies today?
Not necessarily on any single day from a single G1 storm — Raeder's maps are statistical patterns averaged across hundreds of storm events over 67 years, not deterministic forecasts for individual events. A G1 (minor) storm is also at the lower end of the intensity scale Raeder studied; the strongest precipitation signals appeared during intense and super-storms. What the study does establish is that across many such events, precipitation over the Rockies and Hudson Bay is statistically lower in the hours and days following a geomagnetic storm than it would otherwise be — and the effect scales with storm strength.
Why does current weather forecasting ignore geomagnetic activity?
Geomagnetic storm data is not currently an input variable in any major operational weather or climate model worldwide — not in NOAA's models, not in ECMWF's. This is partly because no study had previously demonstrated the effect at the hourly resolution and 67-year data span that Raeder's analysis achieves, and partly because the physical mechanism connecting space weather to surface precipitation remained unproven. Raeder's study provides the first quantified empirical target — specific regional patterns, storm-intensity thresholds, and seasonal dependencies — that modelers can now attempt to reproduce and eventually incorporate into forecast systems.
Could long-term solar activity explain some droughts or wet periods that meteorologists attribute to other causes?
Raeder's analysis raises that question directly. He found that the multi-year climate correlations researchers have observed between the 11-year solar sunspot cycle and surface weather patterns may reflect accumulated short-burst storm effects rather than slowly varying solar irradiance. If correct, that would mean existing climate models are not just missing a signal — they may be misidentifying the mechanism that produces a signal they have already observed. This does not change the role of greenhouse gas emissions or ocean-driven climate variability, but it does suggest that solar influence on regional precipitation patterns may be both stronger and more sudden than long-cycle analyses imply.
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