1991-2020 Degrees Fahrenheit 1 74.8 80.0 -5.2 5 64 1977 1997 1980 1997 bottom-tenth 2 71.2 76.1 -4.9 4 64 1975 2000 1975 1997 bottom-tenth 3 68.5 72.9 -4.4 3 65 1975 2004 1977 1997 bottom-tenth 1967 4 65.6 69.7 -4.1 4 64 1975 2014 1975 1997 bottom-tenth 5 63.8 67.2 -3.4 6 60 1975 2014 1979 1997 bottom-tenth 1967 6 62.0 65.3 -3.3 4 58 1975 2014,2015 1977 1997 bottom-tenth 7 62.4 65.1 -2.7 5 57 1975 1996 1977 1997 bottom-tenth 1971 8 63.9 66.6 -2.7 7 54 1973 1996 1983 1997 bottom-third 9 66.8 69.1 -2.3 12 49 1973 1996 1987 1997 bottom-third 1976 10 69.6 71.6 -2.0 15 46 1973 1996 1987 1997 bottom-third 11 71.7 73.6 -1.9 15 46 1973 1996 1988 1997 bottom-third 1956,1957,1988 12 72.8 74.9 -2.1 14 47 1973 1996 1985 1997 bottom-third 1956,1967 18 70.8 71.7 -0.9 26 31 1976 2015 1994 1997 normal 1960,1992,1994 24 74.2 74.9 -0.7 33 23 1973,1974 2018 1995 1997 normal 36 75.0 74.9 0.1 40 11 1975 2017,2018 1996 1997 top-third 48 74.7 74.9 -0.2 33 13 1975,1976 2018 1996 1997 top-third 2005,2007 60 74.5 74.8 -0.3 27 14 1977 2018 1995 1997 normal 2005