| Jan | Feb | March | April | May | June | July | Aug | Sept | Oct | Nov | Dec |
| 1 | 31.8 | 26.8 | | | | | | | | | | |
| 2 | 29.9 | 37.3 | | | | | | | | | | |
| 3 | 21.4 | 35.3 | | | | | | | | | | |
| 4 | 21.3 | 21.6 | | | | | | | | | | |
| 5 | 26.4 | 23.9 | | | | | | | | | | |
| 6 | 30.8 | 28.2 | | | | | | | | | | |
| 7 | 32.1 | 32.2 | | | | | | | | | | |
| 8 | 26.8 | 30.2 | | | | | | | | | | |
| 9 | 35.3 | 29.6 | | | | | | | | | | |
| 10 | 34.5 | 31.3 | | | | | | | | | | |
| 11 | 38.5 | 27.5 | | | | | | | | | | |
| 12 | 29.7 | 29.1 | | | | | | | | | | |
| 13 | 31.2 | 34.9 | | | | | | | | | | |
| 14 | 31.3 | 25.7 | | | | | | | | | | |
| 15 | 27.8 | 18.9 | | | | | | | | | | |
| 16 | 33.6 | 25.8 | | | | | | | | | | |
| 17 | 20.0 | | | | | | | | | | | |
| 18 | 17.5 | | | | | | | | | | | |
| 19 | 21.1 | | | | | | | | | | | |
| 20 | 21.1 | | | | | | | | | | | |
| 21 | 19.3 | | | | | | | | | | | |
| 22 | 34.5 | | | | | | | | | | | |
| 23 | 31.0 | | | | | | | | | | | |
| 24 | 23.9 | | | | | | | | | | | |
| 25 | 26.3 | | | | | | | | | | | |
| 26 | 26.8 | | | | | | | | | | | |
| 27 | 27.0 | | | | | | | | | | | |
| 28 | 28.3 | | | | | | | | | | | |
| 29 | 33.7 | | | | | | | | | | | |
| 30 | 27.2 | | | | | | | | | | | |
| 31 | 34.3 | | | | | | | | | | | |
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