Geomagnetic Storms of 1939
54 geomagnetic storms of G1 or more began in 1939: 23 G1, 11 G2, 13 G3, 6 G4, 1 G5. The strongest began April 24, 1939 and reached Kp 9-, rank 66 of every storm since 1932.
By month
Every storm of 1939
Times are UT, when the first block at Kp 5 or more began.
| Began (UTC) | Level | Peak Kp | Hours | Highest daily Ap |
|---|---|---|---|---|
| Feb 6, 09:00 | G1 Minor | 5+ | 15 | 43 |
| Feb 24, 15:00 | G3 Strong | 7+ | 27 | 73 |
| Mar 1, 21:00 | G2 Moderate | 6- | 9 | 26 |
| Mar 4, 00:00 | G1 Minor | 5 | 6 | 28 |
| Mar 9, 06:00 | G1 Minor | 5 | 3 | 19 |
| Mar 21, 09:00 | G1 Minor | 5 | 3 | 22 |
| Mar 27, 18:00 | G1 Minor | 5+ | 6 | 26 |
| Mar 28, 12:00 | G3 Strong | 7- | 36 | 71 |
| Mar 30, 18:00 | G1 Minor | 5+ | 6 | 32 |
| Apr 4, 18:00 | G1 Minor | 5 | 3 | 18 |
| Apr 10, 00:00 | G1 Minor | 5+ | 27 | 42 |
| Apr 17, 00:00 | G4 Severe | 8 | 45 | 135 |
| Apr 19, 12:00 | G3 Strong | 7- | 21 | 45 |
| Apr 23, 03:00 | G4 Severe | 8- | 18 | 92 |
| Apr 24, 15:00 | G5 Extreme | 9- | 27 | 79 |
| Apr 27, 21:00 | G2 Moderate | 6 | 3 | 14 |
| May 1, 09:00 | G3 Strong | 7- | 24 | 56 |
| May 5, 18:00 | G2 Moderate | 6 | 6 | 27 |
| May 6, 12:00 | G3 Strong | 7- | 24 | 51 |
| May 8, 00:00 | G2 Moderate | 6- | 9 | 34 |
| May 9, 03:00 | G2 Moderate | 6- | 3 | 26 |
| May 16, 06:00 | G1 Minor | 5 | 3 | 20 |
| May 22, 21:00 | G1 Minor | 5+ | 3 | 30 |
| May 23, 21:00 | G1 Minor | 5+ | 9 | 30 |
| May 25, 15:00 | G1 Minor | 5 | 3 | 28 |
| May 28, 00:00 | G1 Minor | 5+ | 3 | 22 |
| May 29, 06:00 | G1 Minor | 5+ | 3 | 34 |
| Jun 14, 00:00 | G3 Strong | 7 | 12 | 61 |
| Jun 16, 06:00 | G3 Strong | 7- | 6 | 35 |
| Jun 29, 03:00 | G1 Minor | 5 | 3 | 23 |
| Jul 3, 09:00 | G3 Strong | 7- | 12 | 45 |
| Jul 4, 15:00 | G3 Strong | 7+ | 30 | 94 |
| Jul 14, 06:00 | G1 Minor | 5+ | 9 | 31 |
| Jul 16, 18:00 | G1 Minor | 5+ | 3 | 26 |
| Jul 19, 21:00 | G2 Moderate | 6 | 21 | 47 |
| Jul 21, 09:00 | G3 Strong | 7+ | 6 | 36 |
| Jul 26, 03:00 | G2 Moderate | 6- | 6 | 35 |
| Aug 11, 21:00 | G4 Severe | 8- | 33 | 88 |
| Aug 16, 12:00 | G4 Severe | 8- | 15 | 62 |
| Aug 22, 00:00 | G4 Severe | 8- | 39 | 133 |
| Sep 3, 00:00 | G2 Moderate | 6 | 6 | 40 |
| Sep 9, 06:00 | G1 Minor | 5+ | 3 | 26 |
| Sep 17, 03:00 | G3 Strong | 7 | 21 | 55 |
| Sep 19, 15:00 | G1 Minor | 5+ | 18 | 33 |
| Sep 26, 03:00 | G1 Minor | 5+ | 3 | 24 |
| Oct 3, 12:00 | G3 Strong | 7+ | 18 | 51 |
| Oct 6, 03:00 | G2 Moderate | 6+ | 6 | 33 |
| Oct 9, 06:00 | G3 Strong | 7- | 9 | 32 |
| Oct 13, 00:00 | G4 Severe | 8 | 57 | 89 |
| Oct 16, 15:00 | G2 Moderate | 6- | 30 | 36 |
| Nov 13, 03:00 | G1 Minor | 5+ | 12 | 43 |
| Nov 25, 21:00 | G1 Minor | 5 | 3 | 25 |
| Dec 6, 18:00 | G2 Moderate | 6 | 21 | 46 |
| Dec 8, 15:00 | G1 Minor | 5+ | 3 | 30 |
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.