1991-2020 Degrees Fahrenheit 1 60.2 60.6 -0.4 40 27 1978 2000 1983 1976 normal 2 55.4 58.1 -2.7 18 49 1978,1979 2000 1982 1983 bottom-third 3 52.8 57.3 -4.5 3 64 1964 2000 1979 1983 bottom-tenth 2010 4 56.0 58.9 -2.9 7 60 1977 2017 1979 1983 bottom-tenth 2001 5 60.1 62.0 -1.9 10 57 1977 2017 1979 1983 bottom-third 2003 6 64.1 65.6 -1.5 14 53 1977 2017 1979 1983 bottom-third 1997 7 67.7 69.1 -1.4 10 57 1977 1952 1979 1983 bottom-third 1967,1988,2001,2003 8 70.4 71.6 -1.2 13 54 1977 1952 1979 1983 bottom-third 9 72.1 73.4 -1.3 8 59 1977 1952 1979 1983 bottom-third 1970,2003 10 73.0 74.2 -1.2 10 57 1977 1999 1979 1983 bottom-third 1966,2014 11 72.9 74.3 -1.4 7 59 1977 1999 1979 1983 bottom-tenth 1970,1979 12 72.3 73.8 -1.5 7 59 1977 2012 1977 1983 bottom-tenth 1966,1971 18 69.9 71.0 -1.1 14 51 1977 2023 1980 1983 bottom-third 2015 24 72.8 73.8 -1.0 16 48 1977 2013 1980 1983 bottom-third 1976,2015 36 72.7 73.7 -1.0 15 47 1979 2001,2013 1979 1983 bottom-third 1988 48 73.0 73.7 -0.7 20 40 1979 1957 1982 1983 bottom-third 1981,1982,1994 60 73.0 73.7 -0.7 20 38 1977 1957,2003,2013,2020,2023 1983 1983 normal 1983,1985,1986,1990