1991-2020 Degrees Fahrenheit 1 78.0 73.3 4.7 70 6 1993 2021 2005 2003 top-tenth 2 73.3 68.9 4.4 72 4 1993 2021 2005 1988 top-tenth 3 68.2 64.4 3.8 73 3 1950 1988 2005 1988 top-tenth 4 63.6 59.7 3.9 74 2 1950 1988 2005 1988 top-tenth 1980 5 57.8 55.4 2.4 68 8 1951 2012 2005 1988 top-tenth 6 53.2 51.0 2.2 67 9 1975 2016 2005 1992 top-third 1992 7 51.0 47.6 3.4 73 3 1950 2016 2005 2006 top-tenth 8 47.9 45.0 2.9 69 6 1950 2016 2005 1992 top-tenth 9 47.0 44.0 3.0 71 4 1979 2016 2005 2000 top-tenth 10 47.2 44.4 2.8 71 4 1979 2016 2005 2000 top-tenth 11 48.6 46.0 2.6 72 3 1979 2016 2005 2006 top-tenth 12 50.3 48.1 2.2 72 3 1979 2016 2005 2006 top-tenth 18 50.8 49.1 1.7 70 5 1979 2016 2005 1988 top-tenth 24 49.5 48.1 1.4 69 5 1979 2016 2005 2000 top-tenth 2007 36 49.4 48.1 1.3 70 3 1952 2017 2005 2006 top-tenth 48 49.1 48.2 0.9 67 5 1952 2015,2016 2005 2006 top-tenth 2018 60 48.8 48.2 0.6 66 5 1953 2016 2005 2006 top-tenth