1991-2020 Degrees Fahrenheit 1 78.2 80.2 -2.0 22 79 1989 2011 1997 1999 bottom-third 2 77.3 76.1 1.2 81 20 1907 2011 1999 1998 top-third 1974 3 72.3 71.6 0.7 69 32 1973 2011 1999 1998 top-third 1952,2010 4 68.1 67.4 0.7 82 19 1931 2011 1999 1991 top-third 1933,1959,1972,1986,2020 5 65.0 63.2 1.8 94 6 1958,1983 2012 1999 1991 top-tenth 1991,2006 6 61.5 59.8 1.7 94 6 1979 2012 1999 1953 top-tenth 7 59.4 57.4 2.0 95 5 1979 2012 1999 2000 top-tenth 2017 8 59.2 56.8 2.4 96 3 1973 2012 1999 2000 top-tenth 9 59.9 57.7 2.2 95 4 1973 2017 1999 2000 top-tenth 10 61.4 59.6 1.8 93 6 1973 2017 1999 2000 top-tenth 2011 11 63.9 61.8 2.1 96 3 1973 2012 1999 2000 top-tenth 12 65.7 63.7 2.0 96 3 1973 2012 1999 2000 top-tenth 18 63.8 62.4 1.4 95 4 1979 2012 1999 2000 top-tenth 24 65.4 63.7 1.7 94 4 1978 2012 1999 2000 top-tenth 36 64.6 63.7 0.9 92 5 1979 2013 1999 1955 top-tenth 1955,2001 48 64.0 63.7 0.3 82 14 1980 2014 1999 1957 top-third 1935,1957,2008 60 63.8 63.6 0.2 77 18 1979 2012,2020 1999 1957 top-third 2001,2004