| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
| 1901 | 1.05 | 1.69 | 1.74 | 5.05 | 0.93 | 2.00 | 2.25 | 0.74 | 2.10 | 3.98 | 1.26 | 1.35 | 5.05 |
| 1902 | 1.20 | 2.10 | 1.88 | 0.92 | 2.80 | 14.22 | 1.37 | 0.42 | 4.21 | 4.42 | 1.60 | 0.63 | 14.22 |
| 1903 | 1.90 | 1.57 | 0.88 | 1.23 | 1.00 | 0.94 | 2.00 | 2.12 | 0.15 | 2.82 | 0.37 | 2.71 | 2.82 |
| 1904 | 0.63 | 0.99 | 0.82 | 1.55 | 1.20 | 1.10 | 1.21 | 2.32 | 1.78 | 0.27 | 0.60 | 4.35 | 4.35 |
| 1905 | 0.87 | 2.27 | 1.37 | 1.72 | 2.89 | 1.39 | 2.22 | 2.97 | 1.93 | 1.12 | 6.05 | 0.97 | 6.05 |
| 1906 | 3.30 | 1.51 | 0.67 | 2.92 | 0.74 | 1.19 | 6.02 | 0.42 | 0.70 | 2.32 | 0.77 | 1.53 | 6.02 |
| 1907 | 1.41 | 1.70 | 1.22 | 1.65 | 2.22 | 0.21 | 0.80 | 0.15 | 0.63 | 2.40 | 3.95 | 2.42 | 3.95 |
| 1908 | 1.03 | 2.19 | 1.68 | 1.60 | 0.80 | 0.38 | 0.80 | 1.80 | 2.50 | 0.12 | 0.84 | 0.74 | 2.19 |
| 1909 | 0.12 | 1.18 | 1.16 | 1.83 | 2.03 | 1.79 | 4.00 | 0.62 | 0.75 | 2.52 | 0.20 | 2.31 | 2.52 |
| 1910 | 0.68 | 3.80 | 0.42 | 1.90 | 1.93 | 1.90 | 0.97 | 0.70 | 0.38 | 1.44 | 2.30 | 3.80 | |
| 1911 | 0.00 | 1.68 | 1.50 | 2.07 | 0.42 | 0.26 | 2.75 | 1.12 | 0.53 | 0.77 | 2.90 | 2.46 | 2.90 |
| 1912 | 0.98 | 1.50 | 2.00 | 2.49 | 3.86 | 1.73 | 0.40 | 1.03 | 0.00 | 0.40 | 0.29 | 1.50 | 3.86 |
| 1913 | 1.58 | 1.40 | 1.54 | 1.75 | 1.70 | 0.72 | 0.93 | 0.80 | 2.78 | 1.15 | 1.40 | 1.59 | 2.78 |
| 1914 | 0.80 | 1.36 | 1.40 | 1.43 | 2.34 | 0.94 | 0.08 | 1.62 | 1.47 | 0.56 | 1.17 | 1.96 | 2.34 |
| 1915 | 1.91 | 0.78 | 1.50 | 1.36 | 2.48 | 0.52 | 1.64 | 2.90 | 0.91 | 0.62 | 1.21 | 0.60 | 2.90 |
| 1916 | 3.00 | 0.58 | 0.81 | 2.10 | 4.37 | 0.74 | 0.72 | 0.28 | 0.23 | 1.27 | 3.04 | 1.49 | 4.37 |
| 1917 | 1.02 | 1.18 | 1.18 | 0.92 | 1.86 | 0.77 | 1.39 | 0.06 | 1.65 | 1.38 | 0.40 | 0.11 | 1.65 |
| 1918 | 0.73 | 0.28 | 0.63 | 2.15 | 1.33 | 1.06 | 1.47 | 1.07 | 1.80 | 1.62 | 3.05 | 1.29 | 3.05 |
| 1919 | 1.95 | 1.05 | 0.68 | 0.95 | 1.41 | 1.91 | 0.81 | 1.93 | 1.03 | 2.75 | 1.76 | 0.60 | 2.75 |
| 1920 | 2.00 | 0.80 | 2.76 | 3.24 | 1.65 | 0.74 | 2.40 | 3.37 | 0.50 | 1.05 | 1.72 | 3.00 | 3.37 |
| 1921 | 1.04 | 0.90 | 2.56 | 1.38 | 1.35 | 1.90 | 2.61 | 2.26 | 1.13 | 0.60 | 0.42 | 1.36 | 2.61 |
| 1922 | 1.67 | 1.69 | 3.80 | 6.78 | 1.55 | 0.84 | 0.98 | 1.25 | 0.45 | 0.34 | 2.42 | 1.62 | 6.78 |
| 1923 | 2.33 | 2.40 | 2.25 | 3.05 | 1.85 | 1.30 | 0.38 | 0.98 | 2.04 | 1.80 | 2.13 | 2.25 | 2.40 |
| 1924 | 1.74 | 1.86 | 1.08 | 2.87 | 2.55 | 0.95 | 0.06 | 0.00 | 1.06 | 0.05 | 1.35 | 0.80 | 2.87 |
| 1925 | 1.40 | 0.54 | 0.39 | 0.60 | 0.60 | 0.20 | 1.15 | 0.30 | 1.30 | 3.10 | 3.70 | 0.26 | 3.70 |
| 1926 | 1.09 | 0.33 | 1.87 | 3.07 | 0.48 | 1.88 | 2.32 | 0.50 | 0.26 | 0.41 | 1.22 | 1.70 | 2.32 |
| 1927 | 0.97 | 0.99 | 1.92 | 3.80 | 1.82 | 1.88 | 0.27 | 0.34 | 1.78 | 1.40 | 0.87 | 1.71 | 3.80 |
| 1928 | 0.62 | 1.60 | 2.55 | 0.70 | 2.30 | 0.98 | 1.14 | 0.62 | 0.30 | 1.27 | 2.45 | 1.30 | 2.55 |
| 1929 | 1.26 | 0.52 | 1.09 | 1.96 | 2.02 | 1.55 | 1.96 | 0.67 | 1.20 | 1.07 | 2.36 | 3.90 | 3.90 |
| 1930 | 1.40 | 1.48 | 0.68 | 0.28 | 1.50 | 1.92 | 1.10 | 0.74 | 1.54 | 2.04 | 2.77 | 1.38 | 2.77 |