Large Monthly Sunspot Numbers
The following table ranks, in order, the 20 single months from solar cycle 18 to present for which the sunspot number was at its highest monthly-averaged value.
| Ranking | Month | Solar Cycle | Sunspot Number |
|---|---|---|---|
| 1 | October 1957 | 19 | 253.8 |
| 2 | December 1957 | 19 | 239.4 |
| 3 | September 1957 | 19 | 235.8 |
| 4 | January 1959 | 19 | 217.4 |
| 5 | November 1957 | 19 | 210.9 |
| 6 | January 1958 | 19 | 202.5 |
| 7 | November 1956 | 19 | 201.3 |
| 7 | May 1947 | 18 | 201.3 |
| 9 | September 1958 | 19 | 201.2 |
| 10 | June 1957 | 19 | 200.7 |
| 12 | August 1990 | 22 | 200.3 |
| 11 | August 1958 | 19 | 200.2 |
| 13 | August 1959 | 19 | 199.6 |
| 14 | June 1989 | 22 | 196.2 |
| 14 | April 1958 | 19 | 196.0 |
| 16 | December 1956 | 19 | 192.1 |
| 17 | July 1958 | 19 | 191.4 |
| 18 | March 1958 | 19 | 190.7 |
| 19 | April 1948 | 18 | 189.7 |
| 20 | August 1947 | 18 | 188.8 |
Notes
- The strength of the record Solar Cycle 19 (April 1954 to October 1964) is indicated by the fact that it provides a total of 15 entries out of the list of 20. Also, that cycle contributes all of the top seven months in the list.
- Even though Cycle 18 (February 1944 to April 1954) was relatively weaker than Cycle 21 (June 1976 to September 1986) and Cycle 22 (September 1986 to May 1996), it contributes three entries to the list.
- Cycle 22 contributes two entries to the list.
- Cycles 20 (October 1964 to June 1976), 21, 23 (May 1996 to December 2008) and 24 (December 2008 to present) do not contribute to the list.
Material prepared by Richard Thompson
