A dark gap in the Sun’s outer atmosphere is pointed directly at Earth right now, and the stream of charged particles pouring through it has already triggered geomagnetic storms strong enough to push the northern lights unusually far south. If conditions hold through Sunday night, May 17, 2026, aurora displays could become visible from parts of Iowa, Pennsylvania, and other locations that rarely see them.
Solar wind speeds measured by spacecraft stationed roughly a million miles sunward of Earth have climbed to between 630 and 725 kilometers per second, well above the typical background of 300 to 400 km/s. NOAA’s Space Weather Prediction Center has been tracking G1 (minor) to G2 (moderate) geomagnetic storm conditions since the fast stream arrived, and its three-day forecast keeps G2-level activity in the probability window through Sunday night, with residual effects possible into May 19.
Where the storm is coming from
The source is a large coronal hole, a region where the Sun’s magnetic field lines open outward into space instead of looping back to the surface. Without that magnetic lid, solar plasma escapes freely and accelerates into a high-speed stream that can race past Earth days later. This particular hole is a recurrent feature: it was observed during the Sun’s previous 27-day rotation and was expected to return. The 27-day space weather outlook from the National Weather Service noted its influence on geomagnetic activity from May 15 through 17 and flagged elevated high-energy electron flux tied to the stream.
As the fast-moving plasma overtook slower solar wind already in its path, it formed what forecasters call a co-rotating interaction region, a compressed boundary that acts like a wave front. That boundary delivered the initial geomagnetic punch. Behind it, the sustained high-speed flow continues to buffet Earth’s magnetic field.
Two independent models support the timing. The Wang-Sheeley-Arge (WSA) model, which predicts solar wind conditions from coronal-hole geometry, matches the negative magnetic polarity now being measured near Earth. NASA’s SIML-HSS model, which uses extreme-ultraviolet images of the Sun captured by the Solar Dynamics Observatory at 193 angstroms, also pointed to elevated wind speeds arriving during this window. Both are peer-reviewed tools hosted at NASA’s Community Coordinated Modeling Center.
Why Iowa and Pennsylvania are in play
During a G2 storm, the Kp index, a global measure of geomagnetic disturbance, can reach 6 on a scale that tops out at 9. At Kp 6, the auroral oval typically expands far enough south that observers at geomagnetic latitudes near 55 degrees north can see aurora overhead, while those farther south may spot a glow along the northern horizon. Iowa and Pennsylvania sit at roughly 50 to 53 degrees geomagnetic latitude, which means they fall into the fringe zone: visible aurora is possible but not guaranteed, and it depends heavily on one critical variable.
That variable is the orientation of the interplanetary magnetic field, specifically its north-south component, known as Bz. When Bz tilts strongly southward, it opposes Earth’s own magnetic field and allows solar wind energy to pour into the magnetosphere, dramatically amplifying the storm. A sustained southward Bz during Sunday night’s peak could push aurora visibility well into the northern tier of U.S. states. A predominantly northward Bz, on the other hand, would act as a shield, keeping the display confined to Canada and the northern border states even at high wind speeds.
NOAA’s forecast discussion references the negative-polarity magnetic regime but does not publish continuous Bz readings in its text products. That measurement updates in near-real time from the DSCOVR and ACE spacecraft, giving ground-based observers roughly 15 to 60 minutes of warning before conditions at Earth’s magnetosphere change.
What could change
Coronal-hole streams behave differently from the explosive coronal mass ejections that produced the dramatic G5 superstorm in May 2024. Instead of a single powerful shock, high-speed streams deliver a prolonged but fluctuating disturbance. The geomagnetic response can oscillate between quieter and more active intervals over hours, meaning the storm may reach G2 at some points Sunday night and drop back to G1 or below in between.
Whether this pass of the coronal hole will be stronger or weaker than its appearance 27 days ago is also uncertain. Coronal holes can grow, shrink, or shift shape between rotations, and even small changes in the hole’s boundaries alter the speed, density, and duration of the resulting stream. SWPC’s published products do not include a direct comparison between the two passes.
Solar Cycle 25, the current 11-year activity cycle, is near its expected peak, which means large coronal holes and frequent geomagnetic storms are part of a broader pattern that will continue into late 2026. Observers who miss this event will likely get more chances in the months ahead.
How to actually see the aurora Sunday night
Forecasts issued days in advance can set expectations, but the real decision-making tool is NOAA’s OVATION aurora model, which updates every 30 minutes and maps where aurora is likely visible based on current solar wind conditions. Here is how to use it:
- After sunset Sunday, check the OVATION 30-minute aurora forecast repeatedly. If the green shading on the map extends over or near your location, conditions are favorable.
- Find dark skies. City light pollution is the biggest obstacle. Even a 20- to 30-minute drive away from urban centers can make a significant difference.
- Look north. At mid-latitudes, aurora typically appears as a greenish or reddish glow low on the northern horizon. It may not look like the vivid curtains seen in photographs from Alaska or Scandinavia, but smartphone cameras with night mode often capture colors the eye struggles to detect.
- Give your eyes time. Spend at least 15 to 20 minutes outside without looking at bright screens to let your eyes adjust to the dark.
- Watch for timing. The strongest geomagnetic activity often occurs around local midnight, but surges can happen at any point during the night.
If the OVATION map shows the auroral oval staying well north of your area, the odds drop sharply no matter what earlier forecasts suggested. The storm’s peak intensity depends on magnetic field conditions that simply cannot be predicted more than an hour in advance.
What to watch through Monday
SWPC’s three-day forecast extends the elevated geomagnetic activity window through May 19, though storm levels are expected to taper as the high-speed stream rotates past Earth. Residual G1 conditions are possible Monday night for observers at higher latitudes. For anyone south of the Canadian border, Sunday night represents the best window. The SWPC forecast discussion, three-day outlook, and OVATION model are all freely accessible online and updated on fixed schedules by duty forecasters working with real-time satellite data. They remain the most reliable tools for tracking this event as it unfolds.
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*This article was researched with the help of AI, with human editors creating the final content.
