| Jan | Feb | March | April | May | June | July | Aug | Sept | Oct | Nov | Dec |
| 1 | 18.9 | 27.9 | 28.4 | | | | | | | | | |
| 2 | 22.6 | 22.5 | 25.5 | | | | | | | | | |
| 3 | 26.3 | 23.6 | 29.3 | | | | | | | | | |
| 4 | 16.4 | 24.5 | 25.7 | | | | | | | | | |
| 5 | 16.8 | 22.9 | 18.2 | | | | | | | | | |
| 6 | 16.2 | 15.9 | 18.6 | | | | | | | | | |
| 7 | 19.8 | 25.8 | 20.9 | | | | | | | | | |
| 8 | 20.9 | 28.8 | 23.6 | | | | | | | | | |
| 9 | 18.5 | 29.6 | 20.5 | | | | | | | | | |
| 10 | 18.1 | 25.2 | 22.7 | | | | | | | | | |
| 11 | 19.8 | 20.0 | 24.9 | | | | | | | | | |
| 12 | 17.6 | 22.2 | 26.3 | | | | | | | | | |
| 13 | 18.7 | 22.8 | 19.9 | | | | | | | | | |
| 14 | 19.1 | 23.9 | | | | | | | | | | |
| 15 | 18.7 | 24.1 | | | | | | | | | | |
| 16 | 18.8 | 22.0 | | | | | | | | | | |
| 17 | 20.6 | 26.7 | | | | | | | | | | |
| 18 | 20.9 | 32.6 | | | | | | | | | | |
| 19 | 21.1 | 27.5 | | | | | | | | | | |
| 20 | 21.2 | 31.4 | | | | | | | | | | |
| 21 | 22.5 | 29.8 | | | | | | | | | | |
| 22 | 18.4 | 25.3 | | | | | | | | | | |
| 23 | 24.8 | 26.0 | | | | | | | | | | |
| 24 | 22.5 | 24.9 | | | | | | | | | | |
| 25 | 30.0 | 30.0 | | | | | | | | | | |
| 26 | 28.7 | 27.1 | | | | | | | | | | |
| 27 | 22.7 | 23.8 | | | | | | | | | | |
| 28 | 20.5 | 23.6 | | | | | | | | | | |
| 29 | 28.1 | | | | | | | | | | | |
| 30 | 26.2 | | | | | | | | | | | |
| 31 | 26.1 | | | | | | | | | | | |
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