1991-2020 Degrees Fahrenheit 1 45.4 38.2 7.2 74 3 1978 1976 2016 2017 top-tenth 2 38.4 36.6 1.8 56 21 1978 2017 2016 2017 top-third 1991 3 37.6 37.4 0.2 48 29 1977 2017 2015 2017 normal 4 39.9 39.6 0.3 48 28 1977 2017 2015 2017 normal 1952,2008 5 43.9 43.1 0.8 55 21 1977 2017 2015 2017 top-third 2000 6 47.9 47.3 0.6 54 21 1977 2017 2015 2017 top-third 7 51.5 51.2 0.3 53 22 1977 2017 2015 2017 top-third 1960 8 54.5 54.3 0.2 51 24 1977 2017 2015 2017 top-third 1953,1957 9 56.4 56.3 0.1 50 25 1977 2017 2015 2017 top-third 10 57.2 57.1 0.1 49 26 1977 2017 2015 2017 normal 1952,1957 11 57.6 57.1 0.5 58 17 1977 2017 2015 2017 top-third 1954,2006 12 56.6 56.2 0.4 58 17 1977 2017 2015 2017 top-third 2011 18 54.9 53.2 1.7 70 4 1978 2017 2016 2017 top-tenth 24 57.9 56.1 1.8 72 2 1978 2017 2016 2017 top-tenth 36 57.8 56.1 1.7 72 1 1979 2018 2017 2018 highest 48 56.9 56.1 0.8 66 6 1980 2020 2017 2018 top-tenth 60 56.4 56.0 0.4 64 7 1981 2020 2016 2017 top-tenth 2012