G4 (Severe) Geomagnetic Storm of November 17, 1989

Name: G4 (Severe) Geomagnetic Storm of November 17, 1989
Start: 1989-11-17T09:00:00.000Z
End: 1989-11-18T09:00:00.000Z
Location: Earth

November 17 to 18, 1989 · 24 hours

A G4 (severe) geomagnetic storm began November 17, 1989, reached Kp 8 and lasted 24 hours, with a daily Ap as high as 109; at that Kp the aurora may be seen from about 45 degrees geomagnetic latitude.

The Kp through the storm

Began Nov 17, 09:00 UTC, peaked in the block from Nov 17, 18:00 UTC, ended Nov 18, 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: 8 (8.00)
NOAA level: G4 Severe
Duration: 24 hours
Highest daily Ap: 109
Highest 3-hour ap: 207
Rank since 1932: 151 of 4,139

How far south the aurora could have been seen

At Kp 8 NOAA’s scales put the aurora’s reach at about 45 degrees geomagnetic latitude: 37°N in the central US, 36°N in the eastern US, 39°N in the western US and 45°N in northern Europe.

NOAA says a G4 storm’s aurora has been seen as low as Alabama and northern California.

US cities within reach, the southernmost first

Nashville, TN 45.1° geomag.
Durham, NC 45.1° geomag.
Greensboro, NC 45.2° geomag.
Winston-Salem, NC 45.2° geomag.
Clarksville, TN 45.4° geomag.
Reno, NV 45.4° geomag.
Springfield, MO 45.7° geomag.
Wichita, KS 45.9° geomag.
Chesapeake, VA 46.0° geomag.
Norfolk, VA 46.0° geomag.

84 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
November 17, 1989	109	8
November 18, 1989	45	7

Flares before it

Peak (UTC)	Class	Region	Before the storm began
Nov 15, 07:05 UTC	X3.2	NOAA 5786	50 hours
Nov 15, 19:35 UTC	X1.8	NOAA 5786	37 hours
Nov 16, 13:23 UTC	X1.1	NOAA 5786	20 hours
Nov 15, 05:37 UTC	M1.7	NOAA 5783	51 hours
Nov 17, 08:00 UTC	M1.6	NOAA 5793	1 hour
Nov 17, 12:45 UTC	M1.5	NOAA 5793	during it

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, Nov 13 The storm after, Nov 27 Every storm of 1989 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 2026-09-25. 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.