G3 (Strong) Geomagnetic Storm of June 16, 2003

Name: G3 (Strong) Geomagnetic Storm of June 16, 2003
Start: 2003-06-16T09:00:00.000Z
End: 2003-06-18T18:00:00.000Z
Location: Earth

June 16 to 18, 2003 · 57 hours

A G3 (strong) geomagnetic storm began June 16, 2003, reached Kp 7- and lasted 57 hours, with a daily Ap as high as 60; at that Kp the aurora may be seen from about 52 degrees geomagnetic latitude.

The Kp through the storm

Began Jun 16, 09:00 UTC, peaked in the block from Jun 18, 06:00 UTC, ended Jun 18, 18:00 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: 57 hours
Highest daily Ap: 60
Highest 3-hour ap: 111
Rank since 1932: 576 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
June 16, 2003	40	6
June 17, 2003	49	6
June 18, 2003	60	7-

Flares before it

Peak (UTC)	Class	Region	Before the storm began
Jun 15, 23:56 UTC	X1.3	NOAA 10386	9 hours
Jun 17, 22:55 UTC	M6.8	NOAA 10386	during it
Jun 13, 02:04 UTC	M3.1		79 hours
Jun 12, 21:27 UTC	M2.6	NOAA 10375	84 hours
Jun 13, 06:45 UTC	M1.8	NOAA 10375	74 hours
Jun 13, 04:37 UTC	M1.7	NOAA 10375	76 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, Jun 14 The storm after, Jun 27 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.