Geomagnetic Storms of 1940
55 geomagnetic storms of G1 or more began in 1940: 27 G1, 15 G2, 4 G3, 7 G4, 2 G5. The strongest began March 23, 1940 and reached Kp 9, rank 3 of every storm since 1932.
By month
Every storm of 1940
Times are UT, when the first block at Kp 5 or more began.
| Began (UTC) | Level | Peak Kp | Hours | Highest daily Ap |
|---|---|---|---|---|
| Jan 3, 12:00 | G4 Severe | 8- | 9 | 47 |
| Jan 4, 15:00 | G1 Minor | 5 | 15 | 24 |
| Jan 7, 21:00 | G1 Minor | 5 | 3 | 19 |
| Jan 10, 12:00 | G2 Moderate | 6- | 6 | 27 |
| Jan 12, 06:00 | G1 Minor | 5 | 3 | 27 |
| Jan 17, 12:00 | G1 Minor | 5 | 3 | 21 |
| Jan 18, 15:00 | G3 Strong | 7- | 6 | 38 |
| Jan 31, 18:00 | G1 Minor | 5 | 3 | 29 |
| Feb 1, 15:00 | G1 Minor | 5 | 6 | 39 |
| Feb 20, 00:00 | G1 Minor | 5 | 3 | 21 |
| Feb 25, 12:00 | G1 Minor | 5 | 6 | 36 |
| Mar 9, 00:00 | G2 Moderate | 6+ | 6 | 27 |
| Mar 12, 21:00 | G1 Minor | 5 | 3 | 13 |
| Mar 23, 06:00 | G5 Extreme | 9 | 72 | 187 |
| Mar 26, 18:00 | G2 Moderate | 6+ | 12 | 53 |
| Mar 28, 00:00 | G1 Minor | 5+ | 3 | 21 |
| Mar 29, 09:00 | G5 Extreme | 9- | 81 | 189 |
| Apr 2, 18:00 | G4 Severe | 8 | 27 | 99 |
| Apr 25, 03:00 | G4 Severe | 8 | 27 | 70 |
| May 18, 06:00 | G2 Moderate | 6- | 9 | 34 |
| May 22, 03:00 | G2 Moderate | 6- | 6 | 31 |
| May 23, 15:00 | G4 Severe | 8- | 30 | 78 |
| May 26, 21:00 | G2 Moderate | 6- | 6 | 24 |
| Jun 6, 03:00 | G1 Minor | 5+ | 6 | 35 |
| Jun 7, 00:00 | G1 Minor | 5+ | 6 | 32 |
| Jun 14, 15:00 | G2 Moderate | 6+ | 15 | 40 |
| Jun 18, 06:00 | G1 Minor | 5 | 3 | 16 |
| Jun 25, 03:00 | G4 Severe | 8+ | 21 | 126 |
| Jun 26, 15:00 | G2 Moderate | 6- | 3 | 25 |
| Jul 3, 21:00 | G1 Minor | 5 | 3 | 15 |
| Jul 4, 21:00 | G1 Minor | 5 | 3 | 23 |
| Jul 10, 06:00 | G1 Minor | 5 | 3 | 28 |
| Jul 13, 09:00 | G4 Severe | 8- | 9 | 58 |
| Aug 2, 18:00 | G1 Minor | 5+ | 3 | 12 |
| Aug 3, 12:00 | G2 Moderate | 6+ | 6 | 35 |
| Aug 9, 09:00 | G2 Moderate | 6+ | 12 | 38 |
| Aug 26, 21:00 | G2 Moderate | 6- | 3 | 19 |
| Sep 1, 12:00 | G1 Minor | 5 | 3 | 22 |
| Sep 7, 03:00 | G1 Minor | 5+ | 3 | 30 |
| Sep 14, 18:00 | G1 Minor | 5+ | 3 | 15 |
| Sep 26, 15:00 | G4 Severe | 8- | 15 | 45 |
| Sep 27, 18:00 | G2 Moderate | 6- | 27 | 45 |
| Oct 1, 15:00 | G3 Strong | 7 | 6 | 41 |
| Oct 7, 06:00 | G3 Strong | 7 | 27 | 61 |
| Oct 8, 21:00 | G1 Minor | 5 | 3 | 49 |
| Oct 26, 15:00 | G1 Minor | 5+ | 3 | 28 |
| Nov 12, 21:00 | G3 Strong | 7- | 12 | 49 |
| Nov 22, 03:00 | G1 Minor | 5+ | 9 | 35 |
| Nov 23, 06:00 | G1 Minor | 5+ | 6 | 25 |
| Nov 25, 09:00 | G2 Moderate | 6+ | 24 | 36 |
| Nov 29, 03:00 | G1 Minor | 5+ | 21 | 39 |
| Dec 2, 09:00 | G1 Minor | 5 | 3 | 25 |
| Dec 20, 09:00 | G2 Moderate | 6 | 21 | 44 |
| Dec 22, 12:00 | G1 Minor | 5 | 3 | 22 |
| Dec 30, 06:00 | G2 Moderate | 6+ | 3 | 34 |
More
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.