G3 (Strong) Geomagnetic Storm of May 10, 1981

Name: G3 (Strong) Geomagnetic Storm of May 10, 1981
Start: 1981-05-10T21:00:00.000Z
End: 1981-05-11T15:00:00.000Z
Location: Earth

May 10 to 11, 1981 · 18 hours

A G3 (strong) geomagnetic storm began May 10, 1981, reached Kp 7 and lasted 18 hours, with a daily Ap as high as 61; at that Kp the aurora may be seen from about 50 degrees geomagnetic latitude.

The Kp through the storm

Began May 10, 21:00 UTC, peaked in the block from May 10, 21:00 UTC, ended May 11, 15:00 UTC.

From 00 UT the day before to the end of the day after. Blocks in the storm are colored by level; the rest are gray.

The storm

Peak Kp: 7 (7.00)
NOAA level: G3 Strong
Duration: 18 hours
Highest daily Ap: 61
Highest 3-hour ap: 132
Rank since 1932: 465 of 4,139

How far south the aurora could have been seen

At Kp 7 NOAA’s scales put the aurora’s reach at about 50 degrees geomagnetic latitude: 42°N in the central US, 41°N in the eastern US, 44°N in the western US and 51°N in northern Europe.

NOAA says a G3 storm’s aurora has been seen as low as Illinois and Oregon.

US cities within reach, the southernmost first

Washington Heights, NY 50.0° geomag.
The Bronx, NY 50.0° geomag.
Fort Wayne, IN 50.1° geomag.
Des Moines, IA 50.1° geomag.
Yonkers, NY 50.1° geomag.
Akron, OH 50.2° geomag.
Salem, OR 50.3° geomag.
Aurora, IL 50.6° geomag.
Cleveland, OH 50.6° geomag.
Toledo, OH 50.7° geomag.

32 US cities of 150,000 people or more sit at or poleward of that line. Low on the northern horizon under a dark, clear sky; not a record of sightings.

Tonight’s aurora forecast

Day by day

The daily Ap is the mean of the day’s eight three-hour ap values.

UT day	Daily Ap	Highest Kp that day
May 10, 1981	32	7
May 11, 1981	61	7-

Flares before it

Peak (UTC)	Class	Region	Before the storm began
May 10, 12:56 UTC	M3.5	NOAA 3106	8 hours
May 11, 05:48 UTC	M2.9	NOAA 3099	during it
May 9, 02:48 UTC	M2.6	NOAA 3079	42 hours
May 9, 22:11 UTC	M1.9	NOAA 3099	23 hours
May 8, 22:51 UTC	M1.7	NOAA 3099	46 hours
May 10, 07:31 UTC	M1.3	NOAA 3079	13 hours

The strongest M and X class flares GOES recorded from four days before the storm began to its end, the window in which a coronal mass ejection launched with a flare usually arrives. A flare in this list is context, not proof of the cause: many storms come from coronal holes, and many flares launch nothing toward Earth.

The storm before, May 9 The storm after, May 15 Every storm of 1981 The strongest on record This day in weather history Tonight’s aurora forecast

Sources

Kp and ap from GFZ Helmholtz Centre for Geosciences, Geomagnetic Observatory Niemegk, licensed CC BY 4.0: Matzka, J., Stolle, C., Yamazaki, Y., Bronkalla, O. and Morschhauser, A., 2021, The geomagnetic Kp index and derived indices of geomagnetic activity, Space Weather, doi:10.1029/2020SW002641; data doi:10.5880/Kp.0001. Storms, levels and aurora reach worked out by WeatherOverTime from those values and NOAA’s space weather scales. Definitive through August 31, 2026; later values are preliminary. Rebuilt 2026-09-24. Flares from NOAA NCEI’s GOES X-ray flare reports (1975 to 2017) and SWPC’s edited solar event lists, public domain; classes as NOAA recorded them at the time.