1991-2020 Degrees Fahrenheit 1 19.3 18.9 0.4 41 31 1977 2006 2014 2017 normal 2 20.9 21.6 -0.7 34 38 1977 2002 2014 2017 normal 1966 3 25.8 26.6 -0.8 33 39 1977 2002 2015 2017 normal 4 32.6 32.4 0.2 42 30 1977 2002 2015 2017 normal 1953,1966,2004 5 39.1 38.4 0.7 50 22 1977 2016 2015 2017 top-third 6 43.6 43.7 -0.1 39 32 1977 2002 2015 2017 normal 1957,1985,1992 7 47.6 47.7 -0.1 37 34 1977 2002 2015 2017 normal 1960,1975 8 50.3 50.3 0.0 41 30 1977 2002,2017 2015 2017 normal 1956,1958 9 51.1 51.2 -0.1 35 36 1977 2002 2015 2017 normal 1965,1966 10 51.0 50.8 0.2 44 27 1977 2002 2015 2017 normal 1960,1971,1974,2005 11 49.7 49.4 0.3 46 25 1977 2013 2015 2017 normal 12 48.4 47.2 1.2 61 10 1979 2013 2016 2017 top-third 18 47.9 46.0 1.9 66 3 1979 2017 2016 2017 top-tenth 24 49.1 47.2 1.9 67 2 2015 2013 2017 2013 top-tenth 2000 36 48.8 47.2 1.6 66 1 1979 2013,2018 2017 2013 highest 2013 48 47.7 47.2 0.5 54 11 1980 2002 2017 2014 top-third 2006,2014 60 47.1 47.2 -0.1 39 24 1980 2003 2016 2017 normal 1993,2010,2015,2016