1991-2020 Degrees Fahrenheit 1 45.3 50.3 -5.0 18 77 1960 2012 2014 2017 bottom-third 1978 2 47.7 46.6 1.1 78 17 1960 2012 2015 2017 top-third 3 43.5 44.3 -0.8 56 38 1978 2012 2015 2017 normal 2011 4 42.9 43.8 -0.9 55 39 1978 2012 2015 2017 normal 5 44.2 45.0 -0.8 63 31 1940 2012 2015 2017 top-third 1973,2004 6 47.3 47.5 -0.2 65 28 1977 2017 2015 2017 top-third 7 50.6 50.9 -0.3 69 24 1977 2017 2015 2017 top-third 1957,1995 8 53.8 54.2 -0.4 68 25 1977 2017 2015 2017 top-third 9 56.7 56.9 -0.2 71 22 1977 2017 2015 2017 top-third 1950,1990,2011 10 58.5 58.8 -0.3 69 24 1977 2017 2015 2017 top-third 2003 11 59.3 59.6 -0.3 71 22 1977 2017 2015 2017 top-third 1939,2021 12 59.7 59.6 0.1 74 19 1977 2017 2015 2017 top-third 18 56.8 55.5 1.3 87 4 1978 2017 2016 2017 top-tenth 24 61.0 59.5 1.5 87 4 1978 2017 2016 2017 top-tenth 36 61.3 59.5 1.8 88 1 1970,1979 2018 2017 2018 highest 48 60.6 59.5 1.1 84 3 1970 2019,2020 2017 2018 top-tenth 60 60.0 59.5 0.5 79 6 1970 2020 2017 2012 top-tenth