G3 (Strong) Geomagnetic Storm of October 24, 2003

Name: G3 (Strong) Geomagnetic Storm of October 24, 2003
Start: 2003-10-24T15:00:00.000Z
End: 2003-10-25T00:00:00.000Z
Location: Earth

October 24, 2003 · 9 hours

A G3 (strong) geomagnetic storm began October 24, 2003, reached Kp 7- and lasted 9 hours, with a daily Ap as high as 38; at that Kp the aurora may be seen from about 52 degrees geomagnetic latitude.

The Kp through the storm

Began Oct 24, 15:00 UTC, peaked in the block from Oct 24, 15:00 UTC, ended Oct 25, 00:00 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- (6.67)
NOAA level: G3 Strong
Duration: 9 hours
Highest daily Ap: 38
Highest 3-hour ap: 111
Rank since 1932: 726 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 52 degrees geomagnetic latitude: 43°N in the central US, 42°N in the eastern US, 46°N in the western US and 52°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

Sioux Falls, SD 51.8° geomag.
Madison, WI 51.8° geomag.
Milwaukee, WI 51.9° geomag.
Grand Rapids, MI 51.9° geomag.
Buffalo, NY 52.0° geomag.
Tri-Cities, WA 52.1° geomag.
Rochester, NY 52.3° geomag.
Tacoma, WA 52.7° geomag.
Seattle, WA 53.0° geomag.
Saint Paul, MN 53.5° geomag.

13 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
October 24, 2003	38	7-

Flares before it

Peak (UTC)	Class	Region	Before the storm began
Oct 23, 08:35 UTC	X5.4	NOAA 10486	30 hours
Oct 23, 20:04 UTC	X1.1	NOAA 10486	19 hours
Oct 22, 20:07 UTC	M9.9	NOAA 10486	43 hours
Oct 24, 02:54 UTC	M7.6	NOAA 10486	12 hours
Oct 24, 05:10 UTC	M4.2	NOAA 10486	10 hours
Oct 22, 03:51 UTC	M3.7	NOAA 10486	59 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, Oct 21 The storm after, Oct 29 Every storm of 2003 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.