1991-2020 Degrees Fahrenheit 1 22.3 18.9 3.4 57 15 1977 2006 2005 2006 top-third 2 26.6 21.6 5.0 67 5 1977 2002 2006 2002 top-tenth 3 31.1 26.6 4.5 68 4 1977 2002 2006 2002 top-tenth 4 34.9 32.4 2.5 65 7 1977 2002 2006 2002 top-tenth 5 39.6 38.4 1.2 57 15 1977 2016 2004 2006 top-third 1980,1989,2000 6 44.8 43.7 1.1 58 13 1977 2002 2005 2006 top-third 1972 7 49.0 47.7 1.3 60 11 1977 2002 2005 2006 top-third 1964 8 51.3 50.3 1.0 56 15 1977 2002,2017 2005 2006 top-third 1972 9 52.1 51.2 0.9 55 16 1977 2002 2005 2006 top-third 2000 10 52.1 50.8 1.3 61 10 1977 2002 2005 2006 top-third 1964,1992,2023 11 50.6 49.4 1.2 59 12 1977 2013 2005 2006 top-third 2023 12 48.3 47.2 1.1 60 11 1979 2013 2005 2006 top-third 1955,2022 18 47.6 46.0 1.6 63 6 1979 2017 2005 2006 top-tenth 1999 24 48.8 47.2 1.6 64 5 2015 2013 2006 2000 top-tenth 36 48.5 47.2 1.3 64 3 1979 2013,2018 2006 2001 top-tenth 2001 48 47.9 47.2 0.7 57 8 1980 2002 2006 2003 top-third 1956 60 47.8 47.2 0.6 57 6 1980 2003 2005 2006 top-tenth 2008