1991-2020 Degrees Fahrenheit 1 75.0 71.6 3.4 70 6 1974 2003 1990 1983 top-tenth 2 73.5 72.4 1.1 57 19 1993 2003 1990 1988 top-third 3 70.3 69.8 0.5 57 19 1993 1988,2021 1990 1988 top-third 4 66.3 66.2 0.1 53 23 1950 1988 1990 1988 top-third 1956 5 61.7 62.1 -0.4 44 32 1950 1988 1990 1988 normal 1971 6 57.8 58.1 -0.3 49 27 1951 2012 1990 1988 normal 2005 7 55.3 54.0 1.3 64 12 1975 2016 1990 1988 top-third 8 50.9 50.6 0.3 53 23 1950 2016 1990 1988 top-third 9 47.4 48.0 -0.6 41 34 1950 2012 1989 1990 normal 10 46.6 46.8 -0.2 47 28 1979 2012 1989 1990 normal 11 46.8 46.9 -0.1 48 27 1979 2012,2016 1990 1990 normal 1990 12 48.4 48.1 0.3 52 23 1979 2016 1990 1988 top-third 18 51.4 51.4 0.0 54 21 1951 2016 1990 1988 top-third 2002 24 48.1 48.1 0.0 54 20 1979 2016 1990 1988 top-third 2003 36 47.4 48.1 -0.7 43 30 1952 2017 1987 1990 normal 1955,1994 48 48.0 48.2 -0.2 53 19 1952 2016 1989 1990 top-third 2010,2012,2019 60 48.1 48.2 -0.1 55 16 1953 2016 1990 1991 top-third 2005,2012,2014