1991-2020 Degrees Fahrenheit 1 27.8 24.4 3.4 59 17 1979 1995 2004 2000 top-third 1958 2 26.1 20.8 5.3 68 8 1984 1995 2004 2003 top-tenth 3 24.2 20.0 4.2 67 7 1992 1995 2004 2000 top-tenth 4 25.8 22.6 3.2 66 8 1992 2018 2004 2000 top-third 5 29.3 26.8 2.5 65 9 1992 2018 2004 2000 top-third 2016 6 33.5 31.7 1.8 61 13 1992 2018 2004 2000 top-third 7 37.6 36.2 1.4 62 12 1992 2018 2004 2003 top-third 2003,2009 8 40.8 39.9 0.9 57 17 1992 2018 2004 2003 top-third 9 42.9 42.2 0.7 56 18 1992 2018 2004 2003 top-third 10 43.9 43.2 0.7 60 14 1992 2018 2004 2003 top-third 1981 11 43.9 43.1 0.8 61 13 1992 2018 2004 2003 top-third 12 43.5 42.5 1.0 64 10 1992 2018 2004 2003 top-third 18 39.5 38.9 0.6 59 13 1993 2018 2004 2004 top-third 1996,2004 24 43.0 42.5 0.5 60 12 1993 2018 2002 2004 top-third 2001,2007 36 43.2 42.4 0.8 64 6 1994 2018 2004 2001 top-tenth 2001,2006 48 43.1 42.2 0.9 61 7 1976 2019 2004 2003 top-tenth 2002,2003 60 43.0 42.1 0.9 58 8 1977 2020 2004 2004 top-third 2004