1991-2020 Degrees Fahrenheit 1 48.0 41.5 6.5 77 3 1977 1950 2005 1974 top-tenth 2 44.4 42.9 1.5 59 21 1977 2016 2005 2002 top-third 3 47.3 45.6 1.7 66 14 1977 2016 2005 2002 top-third 4 51.2 49.6 1.6 67 13 1977 2016 2005 2002 top-third 2021 5 56.2 54.1 2.1 75 5 1977 2020 2005 2006 top-tenth 6 60.2 58.1 2.1 76 4 1977 2008 2005 2006 top-tenth 2016 7 63.4 61.3 2.1 77 3 1977 2017 2005 2006 top-tenth 2008 8 65.0 63.1 1.9 76 4 1977 2012,2017 2005 2006 top-tenth 2008,2016 9 65.0 63.7 1.3 72 7 1977 2020 2005 1999 top-tenth 1999 10 64.4 63.4 1.0 73 6 1977 2012,2020 2005 1999 top-tenth 1999,2023 11 62.9 62.3 0.6 66 13 1961,1968 2017 2004 2005 top-third 1991,1992 12 61.4 60.8 0.6 64 15 1948 2012 2005 1999 top-third 18 60.4 59.9 0.5 66 13 1964 2017 2005 1992 top-third 24 61.3 60.8 0.5 65 13 1969 2013 2005 1992 top-third 2007 36 60.8 60.7 0.1 60 17 1970 2021 2005 1993 top-third 1993 48 60.7 60.7 0.0 60 16 1970 2020 2005 2005 top-third 2005 60 60.8 60.6 0.2 58 17 1970 2021 2005 2006 top-third 2007