G3 (Strong) Geomagnetic Storm of October 14, 2003

October 14 to 16, 2003 · 45 hours

A G3 (strong) geomagnetic storm began October 14, 2003, reached Kp 7+ and lasted 45 hours, with a daily Ap as high as 67; at that Kp the aurora may be seen from about 48 degrees geomagnetic latitude.

The Kp through the storm

Began Oct 14, 06:00 UTC, peaked in the block from Oct 14, 18:00 UTC, ended Oct 16, 03:00 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+ (7.33)
NOAA level: G3 Strong
Duration: 45 hours
Highest daily Ap: 67
Highest 3-hour ap: 154
Rank since 1932: 309 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 48 degrees geomagnetic latitude: 40°N in the central US, 39°N in the eastern US, 43°N in the western US and 49°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

Baltimore, MD 48.5° geomag.
Indianapolis, IN 48.7° geomag.
Columbus, OH 49.0° geomag.
Lincoln, NE 49.1° geomag.
Philadelphia, PA 49.1° geomag.
Eugene, OR 49.4° geomag.
Pittsburgh, PA 49.6° geomag.
Omaha, NE 49.6° geomag.
Staten Island, NY 49.8° geomag.
Brooklyn, NY 49.8° geomag.

53 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 14, 2003	67	7+
October 15, 2003	44	6
October 16, 2003	29	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, Sep 24 The storm after, Oct 17 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.