1991-2020 Degrees Fahrenheit 1 82.0 83.5 -1.5 16 51 1974 1977 2003 2002 bottom-third 2 84.6 86.7 -2.1 9 58 1971 2019 1990 2003 bottom-third 1966,1968 3 85.6 87.7 -2.1 13 54 1976 1951 2003 2002 bottom-third 1991 4 85.7 87.6 -1.9 11 56 1971 1951 2003 2002 bottom-third 1966 5 84.6 86.5 -1.9 13 54 1976 1998 1992 2003 bottom-third 6 82.5 84.6 -2.1 10 56 1976 2011 1992 2003 bottom-third 7 80.7 82.2 -1.5 16 50 1987 2011 1997 2003 bottom-third 1969 8 77.9 79.5 -1.6 16 49 1987 2000 1997 2003 bottom-third 9 75.6 76.8 -1.2 20 45 1987 2000 1997 2003 bottom-third 1977,2021 10 73.7 74.7 -1.0 24 41 1968 2000 2003 2003 normal 1969,1971,2003,2014 11 72.9 73.7 -0.8 29 36 1987 2000 2003 2002 normal 1993 12 73.0 73.8 -0.8 26 39 1968,1987 2000 2003 2002 normal 1978,1984 18 76.6 77.4 -0.8 22 42 1977 2000 1993 2003 normal 1967,1982,1983,1985,1991,2005,2007 24 72.8 73.8 -1.0 15 48 1971,1988 2000 1993 2003 bottom-third 1967,1975,1985,1993,2015 36 73.2 73.8 -0.6 29 32 1970 2000 2003 2002 normal 48 73.1 73.7 -0.6 24 35 1971 1955,2001,2019 1993 2003 normal 1992,2010 60 73.7 73.7 0.0 38 19 1979 1956,2002,2020 1998 2003 top-third 1998