G3 (Strong) Geomagnetic Storm of March 7, 1994

March 7 to 12, 1994 · 129 hours

A G3 (strong) geomagnetic storm began March 7, 1994, reached Kp 7 and lasted 129 hours, with a daily Ap as high as 65; at that Kp the aurora may be seen from about 50 degrees geomagnetic latitude.

The Kp through the storm

Began Mar 7, 00:00 UTC, peaked in the block from Mar 7, 21:00 UTC, ended Mar 12, 09:00 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: 129 hours
Highest daily Ap: 65
Highest 3-hour ap: 132
Rank since 1932: 397 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
March 7, 1994	65	7
March 8, 1994	53	6-
March 9, 1994	64	6+
March 10, 1994	45	6-
March 11, 1994	40	5+
March 12, 1994	36	5+

Flares before it

GOES recorded no M or X class flare from four days before this storm to its end. Storms without a large flare are commonly driven by fast solar wind from a coronal hole, or by an eruption no flare announced.

The storm before, Mar 2 The storm after, Mar 13 Every storm of 1994 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.