G4 (Severe) Geomagnetic Storm of April 3, 1988

April 3 to 5, 1988 · 45 hours

A G4 (severe) geomagnetic storm began April 3, 1988, reached Kp 8 and lasted 45 hours, with a daily Ap as high as 78; at that Kp the aurora may be seen from about 45 degrees geomagnetic latitude.

The Kp through the storm

Began Apr 3, 06:00 UTC, peaked in the block from Apr 3, 18:00 UTC, ended Apr 5, 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: 8 (8.00)
NOAA level: G4 Severe
Duration: 45 hours
Highest daily Ap: 78
Highest 3-hour ap: 207
Rank since 1932: 154 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
April 3, 1988	49	8
April 4, 1988	78	7+
April 5, 1988	24	6-

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 28 The storm after, Apr 5 Every storm of 1988 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.