The National Oceanic and Atmospheric Administration’s Space Weather Prediction Center issued Watch serial number 285 at 16:36 UTC on Friday, Oct. 9, 2026 (12:36 p.m. Eastern), predicting a G2 (Moderate) geomagnetic storm for Oct. 11. The same message calls for G1 (Minor) storms on Oct. 9 and Oct. 10 and says aurora may be seen as low as New York, Wisconsin and Washington state.
Oct. 11 in the center’s UTC calendar begins at 8 p.m. Eastern on Saturday, Oct. 10, and runs until 8 p.m. Sunday.
Watch serial 285: G1, G1, then G2 on Oct. 11
The center’s alerts feed shows how the watch was rebuilt over a single day. Serial 284, issued at 08:12 UTC on Oct. 9, listed no storm for Oct. 10 and G2 for Oct. 11. Serial 285 superseded it eight and a half hours later with a comment that the G2 was “downgraded” to a G1 watch for Oct. 9 and a G1 watch added for Oct. 10, while leaving Oct. 11 at G2. A K-index warning (serial 5429) and an alert (serial 2690) had already recorded Kp reaching 4 at 10:01 UTC on Oct. 9.
The center followed the watch with a public notice, “Moderate (G2) Geomagnetic Storms Likely on 11 Oct 2026,” posted at 19:45 UTC on Oct. 9.
The watch text lists what a storm at that level can do. Power grid fluctuations can occur and high-latitude power systems may see voltage alarms. Satellite orientation irregularities and added drag on low-Earth-orbit satellites are possible, and HF radio propagation can fade at higher latitudes. The message ties the area of impact to latitudes poleward of 55 degrees geomagnetic, which is why the New York line, which sits near that boundary on the geomagnetic grid, is the southern edge of the story.
Two coronal mass ejections from Oct. 7 and Oct. 8
That notice names the cause: two coronal mass ejections, one that left the Sun on Oct. 7 and a faster one that left on Oct. 8, which forecasters expect to merge with the slower cloud on the way to Earth.
The Oct. 8 launch lines up with a solar flare logged the same day. The center’s feed carries an X-ray summary (serial 327) for an M6.7 flare at N12W20, rated R2 (Moderate) for radio blackouts, with Type II and Type IV radio emission alerts from the Sagamore Hill observatory. The flare region at N12W20 sits within 20 degrees of the center of the Sun’s Earth-facing disk. Space.com’s account of the sequence, which describes an Oct. 8 eruption from sunspot region AR4549 that may catch a slower cloud ahead of it, adds that the exact arrival time is hard to pin down because the solar wind changes how the clouds travel.
Kp 6 on the NOAA scale and the New York aurora line
On the center’s space weather scales, G2 is a Kp index of 6. The scale lists voltage alarms for high-latitude power systems, orientation corrections and changes in orbit drag for spacecraft, and fading HF radio at higher latitudes, and it says aurora “has been seen as low as New York and Idaho,” typically near 55 degrees geomagnetic latitude. Watch 285 narrows that general statement to a specific line for visible aurora, running from New York through Wisconsin to Washington state.
The scale puts G2 events at about 600 per 11-year solar cycle, or roughly 360 days, against about 1,700 G1 events per cycle. A G2 is routine for forecasters and still uncommon enough that its southern aurora edge draws attention each time.
Kp numbers behind the watch
The 3-day forecast available when this was written was issued at 00:30 UTC on Oct. 9, before the Oct. 11 G2 call, and it puts the peak for Oct. 11 at Kp 5.00 (G1) in the 03-06 UTC window, which is 11 p.m. to 2 a.m. Eastern on Saturday night. Its Oct. 9 table peaked at Kp 6.00 (G2) in the 18-21 UTC window. The center’s planetary K-index forecast file carries the same Oct. 11 profile, with Kp 5 predicted at 03:00 UTC and values falling through the day to 2.00 by 18:00 UTC, and shows an estimated Kp of 5.67 at 21:00 UTC on Oct. 9.
Because the watch is the later and higher product, the G2 call for Oct. 11 stands as the center’s position. The Kp 5 value the file predicts falls on Saturday night in the Eastern time zone, a dark-sky window; by 12:00 UTC, 8 a.m. Eastern on Sunday, the predicted value has dropped to 2.67.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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