YEAR |
Summer |
Fall |
Winter |
Spring |
|
D-J-F |
M-A-M |
J-J-A |
S-O-N |
Avg |
|
| 1881 | 20.8 | 16.8 | 12.9 | 17 | 16.86 |
| 1882 | 21.3 | 17.6 | 13.3 | 16.4 | 17.14 |
| 1883 | 21.8 | 17.8 | 12.3 | 16.4 | 17.08 |
| 1884 | 21 | 17.5 | 12.3 | 15.6 | 16.58 |
| 1885 | 21.9 | 16.7 | 13.2 | 17.6 | 17.34 |
| 1886 | 21.6 | 17.9 | 13 | 16.2 | 17.18 |
| 1887 | 20.9 | 17.6 | 12.9 | 17.2 | 17.15 |
| 1888 | 21.5 | 17.1 | 12.6 | 15.9 | 16.75 |
| 1889 | 20.5 | 17.2 | 12.7 | 16.1 | 16.62 |
| 1890 | 20 | 16.9 | 12.5 | 16.1 | 16.37 |
| 1891 | 20.5 | 17.6 | 13.2 | 16 | 16.83 |
| 1892 | 19.9 | 16.6 | 12.5 | 15.1 | 16 |
| 1893 | 19.7 | 17.8 | 12.6 | 15.9 | 16.53 |
| 1894 | 21 | 17.9 | 12.2 | 16 | 16.8 |
| 1895 | 20.9 | 17.2 | 12.1 | 15.6 | 16.44 |
| 1896 | 20.3 | 17.5 | 13.2 | 16.9 | 16.97 |
| 1897 | 21.1 | 17.8 | 13.3 | 15.3 | 16.89 |
| 1898 | 20.5 | 16.4 | 13.4 | 15.9 | 16.54 |
| 1899 | 19.7 | 17.6 | 13.4 | 16 | 16.64 |
| 1900 | 20.8 | 18 | 13.4 | 15.8 | 17 |
| 1901 | 20.2 | 17.4 | 13.6 | 16.6 | 16.98 |
| 1902 | 20.2 | 18.5 | 12.9 | 16 | 16.91 |
| 1903 | 20.1 | 16.5 | 12.2 | 15.1 | 15.98 |
| 1904 | 20.5 | 16.9 | 13.1 | 15.4 | 16.49 |
| 1905 | 20.2 | 17.8 | 13.1 | 15.9 | 16.74 |
| 1906 | 20.3 | 17.6 | 11.8 | 15.9 | 16.41 |
| 1907 | 20.2 | 17.1 | 12.9 | 15.8 | 16.51 |
| 1908 | 19.7 | 16.9 | 12.7 | 15.8 | 16.3 |
| 1909 | 21.2 | 17.7 | 14 | 16.7 | 17.43 |
| 1910 | 20.4 | 17.9 | 13.2 | 16.3 | 16.96 |
| 1911 | 21.6 | 18.3 | 12.9 | 16.7 | 17.38 |
| 1912 | 20.1 | 18.2 | 14 | 16.1 | 17.09 |
| 1913 | 22 | 18 | 13.3 | 16.3 | 17.4 |
| 1914 | 20.1 | 17.7 | 12.9 | 16.7 | 16.84 |
| 1915 | 21.5 | 17.7 | 12.7 | 16.4 | 17.07 |
| 1916 | 21.3 | 17.4 | 12.5 | 16.6 | 16.97 |
| 1917 | 21.8 | 17.6 | 13 | 16.4 | 17.2 |
| 1918 | 21.5 | 17.8 | 14.1 | 16.7 | 17.53 |
| 1919 | 20.9 | 19.1 | 13 | 16.1 | 17.28 |
| 1920 | 21.6 | 18.3 | 13.2 | 16.4 | 17.37 |
| 1921 | 20.9 | 18.6 | 12.3 | 16.2 | 17 |
| 1922 | 20.6 | 18 | 12.6 | 16.5 | 16.91 |
| 1923 | 20.9 | 17.6 | 13.1 | 16.8 | 17.12 |
| 1924 | 21.7 | 17 | 12.9 | 15.9 | 16.89 |
| 1925 | 21.9 | 18.7 | 13.2 | 16.7 | 17.63 |
| 1926 | 20.5 | 18.1 | 12.7 | 15.9 | 16.81 |
| 1927 | 21.5 | 18.3 | 14.2 | 17.5 | 17.88 |
| 1928 | 21.2 | 18.3 | 13.5 | 16 | 17.23 |
| 1929 | 21.1 | 17.5 | 13.6 | 16.7 | 17.23 |
| 1930 | 21.1 | 18.6 | 13.9 | 16.9 | 17.63 |
| 1931 | 22.1 | 17.8 | 13 | 17.1 | 17.52 |
| 1932 | 21.1 | 19.3 | 13.3 | 17.3 | 17.74 |
| 1933 | 21 | 17.7 | 12.4 | 17.3 | 17.08 |
| 1934 | 22.5 | 18.6 | 13.8 | 17.6 | 18.12 |
| 1935 | 22 | 17.7 | 13.5 | 16.6 | 17.46 |
| 1936 | 19.8 | 17.8 | 14.3 | 17.2 | 17.29 |
| 1937 | 21.3 | 17.8 | 13.5 | 17.1 | 17.46 |
| 1938 | 21.1 | 17.9 | 14.1 | 16.2 | 17.31 |
| 1939 | 21 | 18.1 | 14.5 | 17.7 | 17.82 |
| 1940 | 21.9 | 17.1 | 14.1 | 16.6 | 17.44 |
| 1941 | 21.3 | 17.2 | 13.7 | 16.1 | 17.05 |
| 1942 | 21.2 | 18.6 | 13.1 | 17 | 17.46 |
| 1943 | 20.2 | 17.6 | 12.5 | 16.2 | 16.61 |
| 1944 | 22 | 18.1 | 13 | 16.4 | 17.37 |
| 1945 | 20.9 | 18.8 | 12.8 | 17.5 | 17.5 |
| 1946 | 20.4 | 17.6 | 13.1 | 16.4 | 16.91 |
| 1947 | 21.4 | 17.9 | 12.7 | 17.2 | 17.31 |
| 1948 | 21.6 | 18.1 | 12.6 | 16.5 | 17.22 |
| 1949 | 21.4 | 18.3 | 14 | 16.8 | 17.63 |
| 1950 | 20.7 | 17.5 | 13.3 | 16.6 | 17.04 |
| 1951 | 19.9 | 17.7 | 13.5 | 15.2 | 16.58 |
| 1952 | 21.1 | 17.3 | 12.9 | 16.9 | 17.05 |
| 1953 | 21.2 | 17.5 | 13 | 16.9 | 17.14 |
| 1954 | 20.6 | 17.4 | 12.7 | 16.1 | 16.71 |
| 1955 | 20.5 | 17.5 | 12.6 | 15.3 | 16.46 |
| 1956 | 19.8 | 16.5 | 12.5 | 16.6 | 16.35 |
| 1957 | 20.7 | 16.9 | 12.8 | 15.2 | 16.42 |
| 1958 | 20.8 | 17 | 12.8 | 16.1 | 16.64 |
| 1959 | 21.2 | 16.6 | 13 | 16.4 | 16.78 |
| 1960 | 20.9 | 16.9 | 13.1 | 17.7 | 17.13 |
| 1961 | 20.7 | 17.1 | 13.1 | 15.4 | 16.55 |
| 1962 | 19.9 | 16.7 | 12.6 | 15.4 | 16.15 |
| 1963 | 20.8 | 16.6 | 12.4 | 17 | 16.71 |
| 1964 | 20.6 | 17.1 | 11.9 | 15.4 | 16.26 |
| 1965 | 20.4 | 16.7 | 11.7 | 15.5 | 16.07 |
| 1966 | 19 | 16.8 | 12.2 | 16.1 | 16.03 |
| 1967 | 20 | 16.3 | 11.6 | 16.1 | 15.99 |
| 1968 | 19.6 | 17.1 | 11.5 | 15.5 | 15.9 |
| 1969 | 20 | 16.6 | 12.2 | 15.4 | 16.05 |
| 1970 | 20.5 | 17 | 11.5 | 15.4 | 16.1 |
| 1971 | 19.6 | 16.7 | 11.7 | 15.3 | 15.82 |
| 1972 | 20.8 | 17.2 | 12.7 | 17 | 16.93 |
| 1973 | 20.7 | 17.4 | 12.8 | 16.2 | 16.75 |
| 1974 | 20.8 | 17.1 | 12.6 | 14.1 | 16.14 |
| 1975 | 20.8 | 17.1 | 12.7 | 16 | 16.63 |
| 1976 | 20.5 | 17.3 | 12.7 | 15.5 | 16.5 |
| 1977 | 20.1 | 17.2 | 13.1 | 16.3 | 16.67 |
| 1978 | 20.8 | 17.1 | 13 | 15.7 | 16.64 |
| 1979 | 20.6 | 18 | 13.7 | 16 | 17.08 |
| 1980 | 20.8 | 17.2 | 13.5 | 15.9 | 16.84 |
| 1981 | 20.2 | 17.3 | 11.7 | 16 | 16.29 |
| 1982 | 20.1 | 16.6 | 12.1 | 16.2 | 16.25 |
| 1983 | 18.9 | 17.1 | 12.4 | 15.9 | 16.08 |
| 1984 | 20.6 | 17.2 | 13.4 | 16.3 | 16.86 |
| 1985 | 20.2 | 17.2 | 12.8 | 17 | 16.81 |
| 1986 | 20.5 | 17.2 | 13.6 | 16.6 | 16.97 |
| 1987 | 20.4 | 17.6 | 13.1 | 15.9 | 16.75 |
| 1988 | 20.4 | 17.2 | 12.6 | 16 | 16.53 |
| 1989 | 21 | 16.8 | 12.4 | 15.7 | 16.48 |
| 1990 | 20.4 | 17 | 12 | 15.8 | 16.3 |
| 1991 | 19.9 | 17.4 | 12.1 | 16.1 | 16.4 |
| 1992 | 20.5 | 16.7 | 11.9 | 15.6 | 16.18 |
| 1993 | 20.2 | 16.8 | 13 | 16.5 | 16.64 |
| 1994 | 20.2 | 17 | 12.1 | 16.3 | 16.41 |
| 1995 | 20.6 | 16.7 | 11.9 | 15.8 | 16.25 |
| 1996 | 20.7 | 16.7 | 11.8 | 14.7 | 15.96 |
| 1997 | 19.9 | 16.5 | 12.5 | 17 | 16.48 |
| 1998 | 20.6 | 17.2 | 12.7 | 15.7 | 16.57 |
| 1999 | 20.8 | 17.8 | 13.5 | 16.5 | 17.15 |
| 2000 | 21.6 | 17.3 | 13.6 | 16.4 | 17.23 |
| 2001 | 20.2 | 16.8 | 12.8 | 17 | 16.72 |
| 2002 | 20.7 | 17.2 | 12.2 | 16 | 16.52 |
| 2003 | 21.1 | 17.8 | 12.3 | 16.6 | 16.94 |
| 2004 | 19.9 | 17.5 | 13.1 | 17.1 | 16.91 |
| 2005 | 21.9 | 17.7 | 12.5 | 16.4 | 17.13 |
| 2006 | 21.4 | 17.3 | 13.2 | 17.3 | 17.29 |
| 2007 | 21.5 | 18.1 | 12.8 | 16.6 | 17.22 |
| 2008 | 21.5 | 18.6 | 13 | 16 | 17.28 |
| 2009 | 21.6 | 18.4 | 13.9 | 17.1 | 17.76 |
| 2010 | 21.4 | 18 | - | - | - |