| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 10.8 | 6.6 | 10.6 | |||||||||
| 2 | 2.4 | 7.1 | 10.3 | |||||||||
| 3 | 5.1 | 10.3 | 11.5 | |||||||||
| 4 | 2.9 | 10.2 | 12.6 | |||||||||
| 5 | 3.7 | 7.9 | 14.8 | |||||||||
| 6 | 4.3 | 8.8 | 16.8 | |||||||||
| 7 | 1.2 | 5.4 | 15.7 | |||||||||
| 8 | 0.1 | 4.6 | 18.3 | |||||||||
| 9 | 0.4 | 6.8 | 18.4 | |||||||||
| 10 | 0.6 | 4.9 | 13.8 | |||||||||
| 11 | 1.8 | 4.9 | 8.3 | |||||||||
| 12 | 3.8 | 5.7 | 8.4 | |||||||||
| 13 | 6.7 | 3.8 | ||||||||||
| 14 | 9.8 | 5.2 | ||||||||||
| 15 | 11.9 | 4.6 | ||||||||||
| 16 | 11.4 | 4.9 | ||||||||||
| 17 | 8.1 | 4.9 | ||||||||||
| 18 | 6.2 | 6.3 | ||||||||||
| 19 | 2.3 | 8.3 | ||||||||||
| 20 | 5.1 | 14.4 | ||||||||||
| 21 | 5.8 | 15.2 | ||||||||||
| 22 | 6.1 | 13.7 | ||||||||||
| 23 | 6.4 | 11.0 | ||||||||||
| 24 | 10.2 | 12.7 | ||||||||||
| 25 | 7.5 | 10.5 | ||||||||||
| 26 | 7.2 | 9.2 | ||||||||||
| 27 | 8.3 | 9.8 | ||||||||||
| 28 | 8.1 | 10.0 | ||||||||||
| 29 | 8.2 | |||||||||||
| 30 | 6.3 | |||||||||||
| 31 | 7.4 | |||||||||||
| Avg: | 5.8 | 8.1 | *13.3 | |||||||||
| Hi: | 11.9 | 15.2 | *18.4 | |||||||||
| Lo: | 0.1 | 3.8 | *8.3 | |||||||||
| Note: | *Incomplete dataset. | |||||||||||
| Avg | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
| 2025 | 5.8 | 8.1 | *13.3 | |||||||||
| 2024 | 7.6 | 10.4 | 11.7 | 13.6 | 19.4 | 19.1 | 21.1 | 21.1 | 17.4 | 14.8 | 9.7 | 9.0 |
| 2023 | 7.8 | 10.1 | 10.3 | 13.4 | 18.7 | 23.7 | 20.0 | 20.6 | 21.4 | 15.1 | 9.4 | 8.9 |
| 2022 | 7.7 | 9.5 | 13.3 | 14.6 | 17.9 | 21.0 | 23.2 | 24.2 | 18.8 | 16.0 | 11.5 | 6.1 |
| 2021 | 5.3 | 8.4 | 11.5 | 13.2 | 15.1 | 21.9 | 23.8 | 20.0 | 20.6 | 15.2 | 10.2 | 8.1 |
| 2020 | 9.2 | 9.3 | 11.5 | 16.8 | 19.5 | 20.8 | 19.7 | 22.0 | 18.9 | 13.3 | 11.6 | 7.0 |
| 2019 | 5.9 | 11.6 | 11.4 | 15.1 | 16.8 | 19.0 | 22.6 | 21.7 | 18.3 | 13.0 | 8.7 | 8.2 |
| 2018 | 7.6 | 5.8 | 8.4 | 13.8 | 20.2 | 23.1 | 25.7 | 21.1 | 17.8 | 14.4 | 10.9 | 9.0 |
| 2017 | 6.9 | 8.8 | 12.5 | 13.9 | 19.0 | 20.6 | 21.8 | 20.2 | 17.3 | 15.2 | 9.6 | 7.1 |
| 2016 | 8.1 | 8.0 | 10.2 | 12.4 | 18.6 | 20.9 | 21.5 | 21.6 | 20.5 | 14.7 | 8.3 | 9.1 |
| 2015 | 7.6 | 7.3 | 10.4 | 15.7 | 15.3 | 20.3 | 20.9 | 21.2 | 17.9 | 15.0 | 11.8 | 12.0 |
| 2014 | 8.3 | 9.2 | 12.2 | 15.7 | 17.7 | 21.3 | 23.9 | 20.0 | 20.3 | 15.6 | 11.3 | 7.9 |
| 2013 | 5.8 | 6.4 | 7.2 | 12.8 | 15.7 | 19.6 | 24.7 | 21.9 | 17.5 | 15.5 | 9.0 | 9.4 |
| 2012 | 7.8 | 7.1 | 14.1 | 11.6 | 18.5 | 19.0 | 20.9 | 22.2 | 17.5 | 13.3 | 9.3 | 6.6 |
| 2011 | 5.8 | 9.6 | 12.3 | 18.5 | 17.7 | 20.5 | 21.8 | 20.8 | 20.2 | 15.9 | 12.3 | 7.7 |
| 2010 | *5.8 | 6.7 | 12.1 | 16.1 | 17.5 | 23.1 | 22.4 | 20.4 | 18.7 | 13.9 | 7.7 | 2.3 |
| Avg | *7.1 | 8.5 | *11.4 | 14.5 | 17.8 | 20.9 | 22.3 | 21.3 | 18.9 | 14.7 | 10.1 | 7.9 |