| min Apr | max Apr | min May | max May | min Jun | max Jun | |
| 1948-58 | 53 | 60 | 44 | 47 | 45 | 57 |
| 1958-68 | 51 | 59 | 36 | 51 | 50 | 55 |
| 1968-78 | 54 | 60 | 46 | 49 | 40 | 58 |
| 1978-88 | 53 | 58 | 46 | 51 | 54 | 58 |
| 1988-98 | 53 | 57 | 44 | 51 | 55 | 63 |
| 1998-2008 | 51 | 59 | 45 | 48 | 49 | 53 |
| 2008-2014 | 50 | 62 | 45 | 47 | 49 | 55 |