1991-2020 Degrees Fahrenheit 1 52.9 51.5 1.4 64 21 1978 2017 2015 2018 top-third 2 50.4 49.6 0.8 66 19 1978 2017 2018 2017 top-third 2013 3 50.1 49.5 0.6 65 20 1978 2017 2018 2017 top-third 2009 4 50.6 51.2 -0.6 49 36 1977 2017 2015 2018 normal 1956 5 54.1 54.4 -0.3 58 27 1977 2017 2015 2018 top-third 2007,2009 6 58.4 58.3 0.1 66 19 1977 2017 2015 2018 top-third 1952,1986 7 62.1 62.0 0.1 68 17 1977 2017 2018 2018 top-third 1955,1986,2018 8 65.2 64.7 0.5 72 13 1977 2017 2018 2017 top-third 9 67.2 66.4 0.8 74 10 1977 2017 2018 2017 top-third 2005,2008 10 68.4 67.2 1.2 77 7 1977 2017 2018 2017 top-tenth 11 67.8 67.0 0.8 74 10 1977 2017 2018 2017 top-third 2020 12 67.3 66.3 1.0 76 8 1977 2017 2018 2017 top-tenth 2005 18 64.5 63.6 0.9 72 12 1978,1984 2017 2015 2018 top-third 24 67.1 66.3 0.8 74 9 1978 2017 2016 2018 top-third 2008,2020 36 68.0 66.3 1.7 79 3 1979 2018 2017 2018 top-tenth 48 68.2 66.2 2.0 80 1 1980 2019 2018 2019 highest 60 67.5 66.2 1.3 77 3 1963 2020 2018 2019 top-tenth 2021