In 1951 the planetary Kp peaked at 8.7 (G4) on 26 September 1951: 164 storm nights over the year, and 17.1% of its three-hour intervals at storm level.
| Month | Max Kp | Peak day | Storm nights | By class | At storm level | Avg Kp |
|---|---|---|---|---|---|---|
| January | 6.7 | 31 | 8 | G1×6G2×1G3×1 | 6.9% | 2.7 |
| February | 7.0 | 27 | 13 | G1×9G2×2G3×2 | 18.3% | 3.1 |
| March | 6.7 | 13 | 17 | G1×9G2×7G3×1 | 16.9% | 3.1 |
| April | 7.7 | 18 | 20 | G1×8G2×11G4×1 | 28.3% | 3.5 |
| May | 7.3 | 1 | 14 | G1×8G2×1G3×5 | 14.5% | 2.9 |
| June | 8.0 | 17 | 7 | G1×1G2×4G3×1G4×1 | 7.1% | 2.8 |
| July | 7.7 | 2 | 13 | G1×8G2×3G3×1G4×1 | 13.3% | 3.0 |
| August | 6.3 | 16 | 14 | G1×5G2×9 | 17.3% | 3.2 |
| September | 8.7 | 26 | 21 | G1×6G2×7G3×5G4×3 | 38.8% | 3.9 |
| October | 8.7 | 28 | 14 | G1×5G2×6G3×2G4×1 | 19.0% | 3.0 |
| November | 6.0 | 13 | 11 | G1×7G2×4 | 10.8% | 2.9 |
| December | 7.0 | 28 | 12 | G1×7G2×4G3×1 | 14.9% | 2.9 |
All-time record: Kp 9.0 — reached on 27 days, most recently 2024-05-11.
Ranked from the data: peak Kp, then intervals spent at 9.0. Nicknames and reach notes only where documented.
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