Kp5 and above intensity northern lights (aurora borealis) appear in the sky over autumn trees as it lit up the sky in shades of green in Anchorage, Alaska, United States on September 29, 2025. This natural phenomenon was observed by locals, photographers and tourists. (Photo by Hasan Akbas/Anadolu via Getty Images)
Anadolu via Getty Images
A strong display of the Northern Lights was suddenly visible last night across northern U.S. states despite not being predicted by the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center.
According to Spaceweather.com, the Kp index — which provides a rough guide to the intensity of aurora displays — reached Kp 7.33 after an unforecasted G3-rated geomagnetic storm on Sept. 29.
The cause is last weekend’s fall equinox, and it means that any forecasts of geomagnetic activity over the next few weeks should be taken seriously — and aurora-hunters should be on red alert at all times.
Last Night’s Spectacular Northern Lights Display
“I saw so many different colors! Reds, purples, greens, and even blue aurora! At times it felt like we were flying right inside of the Aurora. What an amazing site to see from my office,” wrote by Matt Melnyk, a pilot on a Dreamliner traveling from Calgary to Dublin Ireland, on Spaceweather.com. He was flying over Hudson Bay in Canada, where strong auroras were also seen last week (see images below).
If geomagnetic activity continues through darkness in North America, then up to 11 U.S. states may see aurora on the northern horizon. Much stronger showings are also possible, despite NOAA’s three-day forecast suggesting less intense conditions.
The Northern Lights occur when charged particles from the sun accelerate down Earth’s magnetic field lines and collide with molecules high in Earth’s atmosphere.
NOAA’s aurora viewline for Sept. 30, 2025.
NOAA
Where The Northern Lights May Be Visible
NOAA’s latest aurora viewlines indicate that aurora displays are a possibility in northern U.S. states and Canada, with 11 U.S. states having a chance after dark on Tuesday, Sept. 30.
U.S. states that may see aurora include Alaska and (northerly parts of) Washington, northern Idaho, Montana, North Dakota, South Dakota, Minnesota, Wisconsin, Michigan, New York and Maine. Areas far from light pollution are likely to offer the best views.
Check NOAA’s 30-minute forecast or use the Glendale Aurora and My Aurora Forecast apps.
The aurora borealis as photographed by the author, Jamie Carter, from Churchill, Manitoba, Canada on Sept. 30, 2025.
Jamie Carter
Why The Northern Lights Are Getting Stronger
The possibility of displays of the aurora borealis at more southerly latitudes than is typical is not only down to an increase in solar activity due to the current solar maximum period, but also the Sept. 22’s southward equinox.
Geomagnetic activity tends to be stronger twice a year, around the equinoxes in March and September. It’s explained by the Russell-McPherron Effect, first described in a paper in 1973. Twice a year, near the equinoxes, the south-pointing part of the sun’s magnetic field more easily connects with Earth’s magnetic field. When that happens, charged particles from the sun get through cracks in Earth’s magnetosphere more easily, sometimes causing sudden, intense geomagnetic storms and auroras.
Wishing you clear skies and wide eyes.
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