1991-2020 Degrees Fahrenheit 1 43.0 42.9 0.1 53 23 1970 2002 1984 1985 top-third 2 39.7 39.1 0.6 65 11 1964 2017 1985 1986 top-third 3 36.2 34.2 2.0 69 7 1984 2017 1985 1986 top-tenth 4 33.3 30.0 3.3 72 4 1984 2015 1985 1986 top-tenth 2017 5 30.0 27.6 2.4 66 8 1984 2018 1985 1981 top-third 6 29.9 28.0 1.9 64 10 1973 2018 1985 1981 top-third 1995 7 31.9 30.3 1.6 65 9 1984 2018 1985 1981 top-third 1981 8 34.4 33.5 0.9 58 16 1984 2018 1985 1981 top-third 2012,2020 9 37.5 36.8 0.7 55 19 1973,1992 2018 1985 1981 top-third 10 40.2 39.7 0.5 54 20 1973 2018 1985 1981 top-third 2005 11 42.0 41.6 0.4 55 19 1984 2018 1985 1981 top-third 2005 12 42.8 42.5 0.3 55 19 1984 2018 1985 1981 top-third 2001,2002,2019,2020 18 37.7 37.6 0.1 51 21 1993 2018 1985 1982 top-third 2010 24 42.3 42.5 -0.2 51 21 1993 2018 1985 1982 top-third 2013 36 40.6 42.4 -1.8 19 51 1975 2018 1985 1983 bottom-third 1981 48 40.8 42.2 -1.4 28 40 1976 2019 1985 1984 normal 1962,1990 60 41.0 42.1 -1.1 36 30 1977 2020 1984 1985 normal 1981,1983