1991-2020 Degrees Fahrenheit 1 33.3 29.9 3.4 60 16 1951 2012 1989 1986 top-third 2 27.9 24.5 3.4 60 16 2019 2016 1989 1987 top-third 1976 3 26.6 21.7 4.9 69 7 1950 1992 1989 1987 top-tenth 4 22.8 21.1 1.7 57 18 1950 1992 1989 1987 top-third 5 24.3 22.9 1.4 56 19 1979 2000 1989 1988 top-third 1976 6 27.8 26.4 1.4 58 17 1979 2012 1989 1988 top-third 7 32.0 30.9 1.1 54 21 1952 2012 1989 1988 top-third 1991 8 36.6 35.5 1.1 56 19 1952 2012,2016 1989 1987 top-third 1987 9 40.7 39.2 1.5 64 11 1952 2012,2016 1989 1981 top-third 1961 10 42.8 41.5 1.3 61 13 1952 2016 1989 1981 top-third 2008,2013 11 43.8 42.5 1.3 61 13 1952 2016 1989 1988 top-third 1964 12 43.6 42.4 1.2 61 13 1952 2016 1987 1989 top-third 2002,2006,2008 18 37.0 37.0 0.0 51 22 1952 2013 1987 1989 top-third 24 43.6 42.4 1.2 60 12 1952 2000 1987 1989 top-third 36 43.9 42.4 1.5 65 5 1952 2000 1989 1990 top-tenth 48 43.7 42.4 1.3 66 2 1953 1992 1989 1990 top-tenth 1991,2008 60 43.2 42.4 0.8 61 5 1954 1992 1989 1990 top-tenth