Geomagnetic Storms Since 1932

Name: Geomagnetic storms since 1932, from the Kp index
Creator: GFZ Helmholtz Centre for Geosciences
License: https://creativecommons.org/licenses/by/4.0/

4,139 storms of G1 or more, 1932 to 2026

Every geomagnetic storm in the planetary K index record, from January 1932 to September 23, 2026: 70 G5, 216 G4, 483 G3, 1,375 G2 and 1,995 G1. The busiest year was 1951, with 94. Each storm has a page with its Kp through the storm, how far south the aurora could have reached, and the flares before it since 1975.

Storms every year

Storms of G1 or more that began each year. Tap a year for every storm in it. The peaks follow the roughly eleven-year solar cycle.

By level

Every storm is counted once, at the level of its highest Kp.

Minor: G1 1,995
Moderate: G2 1,375
Strong: G3 483
Severe: G4 216
Extreme: G5 70

Storms known by name

The strongest on record

Ranked by peak Kp, then by the ap summed over the storm. 70 of the top 100 are G5.

Rank	Storm	Peak Kp	Hours	Highest daily Ap
1	November 12, 1960	9 G5	99	280
2	October 29, 2003 the Halloween storms	9 G5	69	204
3	March 23, 1940 the Easter storm of 1940	9 G5	72	187
4	September 18, 1941	9 G5	60	232
5	March 13, 1989 the storm that blacked out Quebec	9 G5	60	246
6	October 5, 1960	9 G5	63	203
7	August 4, 1972	9 G5	69	182
8	May 10, 2024 the Gannon storm	9 G5	39	271
9	February 7, 1986	9 G5	60	202
10	September 21, 1946	9 G5	60	198
11	July 12, 1982	9 G5	75	153
12	July 8, 1958	9 G5	45	200
13	February 10, 1958	9 G5	54	199
14	May 25, 1967	9 G5	30	146
15	July 15, 1959	9 G5	27	236
16	September 4, 1957	9 G5	36	145
17	July 4, 1941	9 G5	30	222
18	March 1, 1941	9 G5	24	207
19	July 26, 1946	9 G5	21	153
20	April 30, 1960	9 G5	33	174
21	March 7, 1970	9 G5	48	149
22	July 15, 2000	9 G5	18	164
23	April 16, 1938	9 G5	21	136
24	March 31, 1960	9- G5	78	241
25	March 29, 1940	9- G5	81	189
26	November 7, 2004	9- G5	84	161
27	March 24, 1991	9- G5	66	161
28	March 23, 1946	9- G5	78	195
29	September 21, 1957	9- G5	78	164
30	September 5, 1982	9- G5	48	199
31	June 4, 1991	9- G5	45	197
32	January 24, 1949	9- G5	48	156
33	May 9, 1992	9- G5	54	179
34	January 19, 2026	9- G5	42	144
35	March 27, 1946	9- G5	39	213
36	September 3, 1958	9- G5	45	131
37	February 7, 1946	9- G5	33	127
38	September 2, 1957	9- G5	42	135
39	April 26, 1956	9- G5	33	172
40	September 21, 1963	9- G5	42	126
41	July 17, 1959	9- G5	36	119
42	May 2, 1998	9- G5	60	101
43	July 4, 1974	9- G5	54	130
44	March 31, 2001	9- G5	33	192
45	May 12, 1949	9- G5	33	153
46	July 26, 2004	9- G5	27	186
47	April 23, 1946	9- G5	36	117
48	November 8, 1991	9- G5	33	119
49	July 13, 1991	9- G5	42	134
50	October 10, 2024	9- G5	24	116

By month

Storms cluster around the equinoxes, in March and April and in September and October, when the Earth’s field is best placed to couple with the solar wind.

What this record is

The planetary K index, Kp, measures how disturbed the Earth’s magnetic field is, every three hours, on a scale from 0 to 9 in thirds. It is worked out from magnetometers at observatories between about 44 and 60 degrees geomagnetic latitude, and GFZ Potsdam keeps the record back to 1932. The ap index is the same disturbance on a linear scale, and the daily Ap is the mean of a day’s eight ap values.

A storm here is a run of three-hour blocks at Kp 5 or more, NOAA’s G1, with runs joined when no more than nine quiet hours separate them. Its level is NOAA’s for its highest Kp, read as SWPC reads its thirds: Kp 9- counts as G5. Its date is the UT day its first storm block began.

How far south the aurora could have been seen follows NOAA’s scales, the same line the aurora forecast uses: about 60 degrees geomagnetic latitude at G1, five degrees nearer the equator for each level, 40 degrees at G5. It is where the aurora could be seen low on the northern horizon under a dark, clear sky, not a record of where anyone saw it.

Every year

Tonight’s aurora forecast Space weather now

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.