YEAR |
Summer |
Fall |
Winter |
Spring |
|
D-J-F |
M-A-M |
J-J-A |
S-O-N |
Avg |
|
| 1881 | 22.9 | 16.7 | 9.7 | 16.8 | 16.55 |
| 1882 | 22.9 | 14.7 | 9.8 | 16.5 | 15.97 |
| 1883 | 22.6 | 15.8 | 10.3 | 15.8 | 16.13 |
| 1884 | 23.2 | 15.9 | 9.6 | 16.3 | 16.27 |
| 1885 | 23.1 | 15.1 | 8.3 | 16.5 | 15.75 |
| 1886 | 22.5 | 15.8 | 9.3 | 15.1 | 15.69 |
| 1887 | 22.3 | 15.3 | 11.2 | 15.7 | 16.11 |
| 1888 | 22.9 | 16.3 | 10.2 | 15.6 | 16.28 |
| 1889 | 22.1 | 16.8 | 9.1 | 15 | 15.74 |
| 1890 | 22.3 | 16.2 | 9 | 15.2 | 15.66 |
| 1891 | 23.1 | 16 | 9.9 | 16.1 | 16.25 |
| 1892 | 22.7 | 15.5 | 9.3 | 15.4 | 15.72 |
| 1893 | 21.9 | 16.2 | 9.4 | 14.5 | 15.51 |
| 1894 | 24.3 | 16.3 | 8.7 | 14.8 | 16.02 |
| 1895 | 22.1 | 16.8 | 11.1 | 15.1 | 16.27 |
| 1896 | 21.9 | 16.9 | 11.5 | 17.7 | 16.99 |
| 1897 | 22.9 | 17.7 | 9.1 | 16.2 | 16.49 |
| 1898 | 23.3 | 15.8 | 8.9 | 14.1 | 15.53 |
| 1899 | 22.1 | 17.6 | 10.7 | 14.8 | 16.31 |
| 1900 | 23.8 | 16.6 | 11.3 | 16.7 | 17.08 |
| 1901 | 22 | 16.7 | 11 | 16.6 | 16.57 |
| 1902 | 22.9 | 18.1 | 9.9 | 15.5 | 16.59 |
| 1903 | 22.2 | 17.2 | 10.5 | 16.4 | 16.57 |
| 1904 | 21.6 | 17.3 | 10.6 | 16.2 | 16.43 |
| 1905 | 21.3 | 16.6 | 9.8 | 16 | 15.91 |
| 1906 | 22.7 | 18.2 | 9.9 | 15.8 | 16.65 |
| 1907 | 22.3 | 16.2 | 9.3 | 14.7 | 15.62 |
| 1908 | 22.2 | 16.6 | 10 | 15.6 | 16.1 |
| 1909 | 21.9 | 15.7 | 10.1 | 15 | 15.7 |
| 1910 | 21.5 | 15.2 | 10 | 15.6 | 15.56 |
| 1911 | 22.5 | 15.9 | 8.9 | 14.6 | 15.47 |
| 1912 | 22.4 | 16.6 | 9.4 | 15.8 | 16.04 |
| 1913 | 23.8 | 17.6 | 11.4 | 16.1 | 17.24 |
| 1914 | 22.6 | 17 | 12.3 | 15.3 | 16.78 |
| 1915 | 21.7 | 16.4 | 9.3 | 16 | 15.88 |
| 1916 | 22.8 | 16.9 | 7.7 | 16.6 | 16 |
| 1917 | 22.7 | 15.6 | 9.4 | 15.7 | 15.83 |
| 1918 | 23.2 | 16.7 | 9.7 | 15.7 | 16.32 |
| 1919 | 22.9 | 18.3 | 10.3 | 15.1 | 16.66 |
| 1920 | 22.8 | 18 | 9.2 | 16 | 16.51 |
| 1921 | 22 | 17 | 8.5 | 15.9 | 15.86 |
| 1922 | 22.3 | 16.5 | 11.3 | 15.8 | 16.48 |
| 1923 | 22.8 | 17 | 10.1 | 15.3 | 16.32 |
| 1924 | 21.6 | 15.8 | 9.2 | 14.8 | 15.36 |
| 1925 | 24.3 | 16.8 | 9.6 | 16 | 16.68 |
| 1926 | 24.2 | 16.8 | 10.7 | 16.1 | 16.95 |
| 1927 | 23.9 | 17.6 | 10.9 | 15.5 | 16.98 |
| 1928 | 21 | 17.2 | 10.1 | 16.7 | 16.23 |
| 1929 | 23.3 | 17.5 | 10.5 | 16.3 | 16.9 |
| 1930 | 23.3 | 17.8 | 10.5 | 15.8 | 16.86 |
| 1931 | 23.6 | 16 | 9.6 | 15.8 | 16.24 |
| 1932 | 22.9 | 17 | 11.8 | 17.9 | 17.41 |
| 1933 | 22.4 | 17.7 | 10.3 | 16.7 | 16.78 |
| 1934 | 22.8 | 16 | 11.1 | 15.7 | 16.39 |
| 1935 | 22.2 | 17.7 | 11 | 15.3 | 16.55 |
| 1936 | 22.5 | 17.5 | 11.2 | 15.8 | 16.73 |
| 1937 | 22.9 | 16.7 | 11.1 | 15 | 16.43 |
| 1938 | 22.1 | 16.8 | 10.6 | 16.2 | 16.43 |
| 1939 | 23.1 | 16.5 | 12.7 | 16 | 17.09 |
| 1940 | 22.3 | 17.2 | 11.7 | 15.5 | 16.68 |
| 1941 | 22 | 16 | 11.8 | 15.8 | 16.39 |
| 1942 | 23.5 | 16.1 | 9.7 | 16.8 | 16.52 |
| 1943 | 24.5 | 17.6 | 11.3 | 17.1 | 17.6 |
| 1944 | 23 | 16.9 | 12.1 | 17.6 | 17.41 |
| 1945 | 23.4 | 18.3 | 10.8 | 17.5 | 17.5 |
| 1946 | 22.7 | 17 | 10.3 | 17.4 | 16.88 |
| 1947 | 22.8 | 16.7 | 10.9 | 17.1 | 16.86 |
| 1948 | 22.1 | 16.4 | 10.7 | 16.5 | 16.46 |
| 1949 | 23.8 | 17.3 | 10.9 | 16.2 | 17.05 |
| 1950 | 22.9 | 18.1 | 11.2 | 15.4 | 16.9 |
| 1951 | 22.2 | 16.7 | 12.7 | 16.3 | 16.95 |
| 1952 | 23.9 | 17.8 | 10.2 | 16.1 | 17 |
| 1953 | 22.8 | 17.2 | 10.4 | 16.4 | 16.7 |
| 1954 | 23 | 16.9 | 10.8 | 16.3 | 16.75 |
| 1955 | 23 | 15.9 | 10.3 | 16.4 | 16.43 |
| 1956 | 22.1 | 15.3 | 11.2 | 16.9 | 16.34 |
| 1957 | 22.8 | 18.3 | 10.3 | 16.7 | 17.02 |
| 1958 | 22.5 | 17.2 | 12.8 | 18.1 | 17.62 |
| 1959 | 22.7 | 15.4 | 10.9 | 16.9 | 16.49 |
| 1960 | 24.6 | 17.4 | 11.3 | 17.6 | 17.72 |
| 1961 | 22.9 | 17.7 | 11.6 | 17.9 | 17.56 |
| 1962 | 22.8 | 17.5 | 10.5 | 17.5 | 17.07 |
| 1963 | 23.8 | 18.1 | 12.1 | 15.8 | 17.44 |
| 1964 | 23.2 | 17.2 | 10.1 | 16.7 | 16.81 |
| 1965 | 24.2 | 16.4 | 12.6 | 17.6 | 17.68 |
| 1966 | 22.5 | 17.9 | 11.9 | 16.4 | 17.18 |
| 1967 | 23.3 | 18.4 | 9.8 | 18.2 | 17.41 |
| 1968 | 24.3 | 16.7 | 12.7 | 18 | 17.93 |
| 1969 | 23.5 | 18.4 | 11.9 | 17.3 | 17.8 |
| 1970 | 24.7 | 19 | 11.4 | 17.2 | 18.06 |
| 1971 | 22.4 | 16.4 | 11.6 | 18.1 | 17.12 |
| 1972 | 24.4 | 18.2 | 11.5 | 16.9 | 17.75 |
| 1973 | 22.9 | 17.6 | 11.4 | 16.9 | 17.21 |
| 1974 | 22.8 | 18.7 | 11.6 | 16.5 | 17.4 |
| 1975 | 23.1 | 18.3 | 11.4 | 17.6 | 17.58 |
| 1976 | 24.1 | 16.9 | 11 | 16.9 | 17.19 |
| 1977 | 23.3 | 17.2 | 11.9 | 18.7 | 17.8 |
| 1978 | 23.2 | 17.5 | 11.6 | 17.7 | 17.5 |
| 1979 | 24.4 | 17.7 | 12.6 | 16.5 | 17.78 |
| 1980 | 23.6 | 20.2 | 11.4 | 17.1 | 18.07 |
| 1981 | 23.9 | 18.6 | 11.7 | 17.1 | 17.82 |
| 1982 | 23.5 | 19.1 | 11.8 | 17.5 | 17.96 |
| 1983 | 24.6 | 17.8 | 10.3 | 17.6 | 17.6 |
| 1984 | 24.3 | 17.4 | 10 | 17.8 | 17.36 |
| 1985 | 23.1 | 18 | 12.3 | 17.7 | 17.77 |
| 1986 | 24.2 | 17.7 | 12.6 | 17.7 | 18.04 |
| 1987 | 24.5 | 17.5 | 12.3 | 17.2 | 17.89 |
| 1988 | 23.2 | 16.8 | 11 | 17.2 | 17.05 |
| 1989 | 25.3 | 18.3 | 12.3 | 17 | 18.23 |
| 1990 | 24.3 | 16.9 | - | 18.9 | 18 |
| 1991 | 22.7 | 19.2 | - | 17.9 | 17.92 |
| 1992 | 23.6 | - | 13.2 | 17 | 18.03 |
| 1993 | 24.1 | 19.2 | 12.4 | 17.4 | 18.28 |
| 1994 | 23.4 | - | 12.5 | 17.2 | 17.77 |
| 1995 | 24.2 | 18 | 10.8 | 18.2 | 17.8 |
| 1996 | 24.3 | 19.1 | 11.6 | 18.2 | 18.28 |
| 1997 | 24.7 | 19.6 | 13 | 17.4 | 18.67 |
| 1998 | 22.2 | 18 | 12.9 | 17.8 | 17.71 |
| 1999 | 23.1 | 17.8 | 11.9 | 17.9 | 17.68 |
| 2000 | 24.5 | 18 | 11.3 | 17.1 | 17.73 |
| 2001 | 24.8 | 18.2 | 13 | 17.6 | 18.4 |
| 2002 | 23.4 | 18.3 | 11.7 | 18.4 | 17.98 |
| 2003 | 23.6 | 18.1 | 11.6 | 17.7 | 17.75 |
| 2004 | 23.2 | 18.5 | 12.6 | 17.5 | 17.93 |
| 2005 | 24.1 | 17.5 | 12.8 | 17.8 | 18.03 |
| 2006 | 23.3 | 17.3 | - | - | - |