| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year Total |
Seasonal Total July-June |
| 1946 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 0.0 | ||||||
| 1947 | 0.7 | 0.2 | 0.6 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 3.2 | 4.7 | 1.5 |
| 1948 | 3.0 | 4.5 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.1 | 7.6 | 10.7 |
| 1949 | 0.6 | 3.0 | 0.1 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 3.7 | 3.8 |
| 1950 | 0.0 | 1.0 | 1.5 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 2.5 | 2.5 |
| 1951 | 0.1 | 0.5 | 0.1 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.6 | 1.3 | 0.7 |
| 1952 | 1.1 | 3.0 | 3.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 1.5 | 0.3 | 8.9 | 7.7 |
| 1953 | 0.5 | 0.0 | 4.5 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 1.0 | 0.0 | 6.0 | 6.8 |
| 1954 | 6.0 | 0.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 2.5 | 8.5 | 7.0 |
| 1955 | 1.1 | 2.1 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.5 | 0.0 | 3.7 | 5.7 |
| 1956 | 2.6 | 0.0 | 1.0 | 0.5 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 4.1 | 4.6 |
| 1957 | 8.0 | 7.5 | 0.0 | 0.5 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 2.0 | 18.0 | 16.0 |
| 1958 | 8.0 | 1.5 | 3.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 10.0 | 22.5 | 14.5 |
| 1959 | 0.4 | 0.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 0.4 | 10.4 |
| 1960 | 0.4 | 4.0 | 11.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 6.0 | 21.4 | 15.4 |
| 1961 | 6.0 | 1.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.5 | 7.5 | 13.0 |
| 1962 | 9.0 | 5.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 6.5 | 20.5 | 14.5 |
| 1963 | 3.0 | 2.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 2.0 | 7.0 | 11.5 |
| 1964 | 3.0 | 10.5 | 3.0 | 1.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 17.5 | 19.5 |
| 1965 | 6.0 | 1.0 | 2.5 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 9.5 | 9.5 |
| 1966 | 26.0 | 2.5 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 8.0 | 36.5 | 28.5 |
| 1967 | 6.0 | 28.5 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 6.0 | 4.0 | 44.5 | 42.5 |
| 1968 | 0.0 | 0.0 | 1.5 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 3.0 | 4.5 | 11.5 |
| 1969 | 0.0 | 0.0 | 14.5 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 14.5 | 17.5 |
| 1970 | 0.0 | 1.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 4.0 | 5.0 | 1.0 |
| 1971 | 3.5 | 0.0 | 1.5 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 5.0 | 9.0 |
| 1972 | 0.4 | 7.5 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 7.9 | 7.9 |
| 1973 | 1.0 | 1.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 1.0 | 3.0 | 2.0 |
| 1974 | 0.0 | 3.1 | 2.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 5.1 | 6.1 |
| 1975 | 3.0 | 0.5 | 1.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 4.5 | 4.5 |
| 1976 | 1.4 | 1.0 | 2.5 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 1.0 | 6.0 | 11.9 | 4.9 |
| 1977 | 10.5 | 0.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 10.5 | 17.5 |
| 1978 | 3.0 | 15.3 | 10.8 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 1.7 | 0.0 | 30.8 | 29.1 |
| 1979 | 6.2 | 27.6 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 1.0 | 0.0 | 0.0 | 34.8 | 35.5 |
| 1980 | 4.0 | 4.2 | 5.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 13.2 | 14.2 |
| 1981 | 0.4 | 0.0 | 0.8 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.5 | 1.7 | 1.2 |
| 1982 | 10.3 | 7.1 | 1.0 | 0.2 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 7.0 | 25.6 | 19.1 |
| 1983 | 0.0 | 13.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 13.0 | 20.0 |
| 1984 | 6.1 | 0.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 6.1 | 6.1 |
| 1985 | 11.5 | 1.0 | 0.0 | 1.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 2.0 | 15.5 | 13.5 |
| 1986 | 4.4 | 6.5 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 10.9 | 12.9 |
| 1987 | 23.5 | 23.5 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 1.0 | 0.0 | 48.0 | 47.0 |
| 1988 | 5.7 | 0.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 5.7 | 6.7 |
| 1989 | 2.0 | 11.7 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 14.5 | 28.2 | 13.7 |
| 1990 | 0.0 | 0.0 | 0.3 | 0.5 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 0.8 | 15.3 |
| 1991 | 1.0 | 1.1 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 2.1 | 2.1 |
| 1992 | 0.0 | 0.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| 1993 | 0.0 | 2.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 6.8 | 8.8 | 2.0 |
| 1994 | 1.2 | 0.0 | 2.5 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 3.7 | 10.5 |
| 1995 | 0.0 | 0.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.7 | 0.7 | 0.0 |
| 1996 | 15.1 | 24.4 | 6.3 | 2.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 47.8 | 48.5 |
| 1997 | 0.3 | 3.3 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 1.0 | 4.6 | 3.6 |
| 1998 | 0.0 | 0.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 0.0 | 1.0 |
| 1999 | 0.0 | 3.0 | 4.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 7.0 | 7.0 |
| 2000 | 14.0 | 0.0 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 14.0 | 14.0 |
| 2001 | 0.0 | 6.0 | 2.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 0.0 | 8.0 | 8.0 |
| 2002 | 8.2 | 4.1 | 0.0 | 0.0 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.0 | 4.5 | 16.8 | 12.3 |
| 2003 | 2.4 | 23.9 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0.5 | 26.75 | 30.8 |
| 2004 | 5.5 | 2.0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0.5 | 8.0 | 8.0 |
| 2005 | 6.2 | 3.0 | 0.2 | 0 | 0 | 0 | 0 | 0 | 0 | 9.4 | 9.9 | |||
| Average | 4.0 | 4.7 | 1.5 | 0.1 | 0 | 0 | 0 | 0 | 0 | 0.0 | 0.2 | 1.7 | 12.1 | 12.3 |