1991-2020 Degrees Fahrenheit 1 53.9 51.7 2.2 68 17 1978 2017 1949 1950 top-third 2 54.3 49.8 4.5 80 5 1978 2017 1949 1950 top-tenth 3 52.9 49.6 3.3 80 5 1978 2017 1949 1950 top-tenth 1957 4 53.9 51.3 2.6 77 8 1978 2017 1949 1950 top-tenth 5 56.4 54.5 1.9 76 9 1977 2017 1949 1950 top-third 1957 6 59.5 58.5 1.0 72 13 1977 2017 1949 1950 top-third 2008 7 62.5 62.1 0.4 70 15 1977 2017 1949 1950 top-third 1972,2011 8 65.1 64.8 0.3 69 16 1977 2017 1949 1950 top-third 2011,2013 9 67.0 66.6 0.4 68 16 1977 2017 1949 1950 top-third 2008,2013 10 67.9 67.3 0.6 71 13 1977 2017 1949 1950 top-third 2000,2005 11 67.5 67.2 0.3 68 16 1977 2017 1949 1950 top-third 12 66.6 66.5 0.1 64 20 1977 2017 1949 1950 top-third 1986,2021 18 63.7 63.8 -0.1 63 21 1984 2017 1949 1950 top-third 1996 24 66.5 66.4 0.1 63 20 1978 2017 1949 1950 top-third 2014 36 65.8 66.4 -0.6 55 27 1979,1984 2018 1949 1950 top-third 1966,2004 48 65.7 66.4 -0.7 50 31 1980 2019 1949 1950 normal 60 65.6 66.3 -0.7 47 33 1980 2020 1949 1950 normal 1952