| min Jan | max Jan | min Feb | max Feb | min Mar | max Mar | |
| 1948-58 | 48 | 55 | 50 | 60 | 55 | 62 |
| 1958-68 | 48 | 53 | 50 | 60 | 51 | 58 |
| 1968-78 | 48 | 52 | 50 | 60 | 52 | 62 |
| 1978-88 | 48 | 54 | 50 | 60 | 53 | 58 |
| 1988-98 | 48 | 55 | 52 | 60 | 50 | 60 |
| 1998-2008 | 50 | 58 | 50 | 60 | 52 | 59 |
| 2008-2014 | 50 | 56 | 52 | 55 | 50 | 60 |