In 1959 the planetary Kp peaked at 9.0 (G5) on 15 July 1959: 133 storm nights over the year, and 14.5% of its three-hour intervals at storm level.
| Month | Max Kp | Peak day | Storm nights | By class | At storm level | Avg Kp |
|---|---|---|---|---|---|---|
| January | 6.3 | 9 | 6 | G1×2G2×4 | 6.0% | 2.4 |
| February | 7.3 | 25 | 14 | G1×5G2×8G3×1 | 21.4% | 3.2 |
| March | 8.3 | 27 | 10 | G1×5G2×1G3×2G4×2 | 15.7% | 2.7 |
| April | 7.7 | 10 | 8 | G1×5G2×1G3×1G4×1 | 9.6% | 2.5 |
| May | 8.3 | 12 | 11 | G1×5G2×4G3×1G4×1 | 12.9% | 2.7 |
| June | 6.3 | 29 | 8 | G1×2G2×6 | 8.8% | 2.6 |
| July | 9.0 | 15 | 11 | G1×5G2×1G3×2G4×2G5×1 | 15.3% | 3.3 |
| August | 8.3 | 16 | 14 | G1×10G2×2G4×2 | 14.5% | 3.0 |
| September | 7.7 | 3 | 19 | G1×10G2×5G3×3G4×1 | 23.8% | 3.5 |
| October | 7.0 | 4 | 11 | G1×3G2×6G3×2 | 14.5% | 2.7 |
| November | 8.0 | 28 | 11 | G1×4G2×6G4×1 | 18.3% | 3.0 |
| December | 7.7 | 5 | 10 | G1×6G2×3G4×1 | 14.1% | 2.9 |
In the hall of storms: 15 July 1959 · Kp 9.0 →
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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