1991-2020 Degrees Fahrenheit 1 72.3 66.4 5.9 66 2 1973 2004 2014 2004 top-tenth 2 69.4 63.3 6.1 67 1 1964 2015 2014 2015 highest 3 65.7 61.2 4.5 65 1 1955 2015 2014 2015 highest 4 63.7 59.8 3.9 61 1 1973 2015 2014 2015 highest 5 64.0 60.6 3.4 61 1 1973 2015 2014 2015 highest 6 66.7 63.3 3.4 60 1 1973 2015 2014 2015 highest 7 70.0 66.9 3.1 60 1 1973 2015 2014 2015 highest 8 72.7 70.3 2.4 60 1 1973 1996,2015 2014 1996 highest 1996 9 75.2 73.0 2.2 60 1 1973 2015 2014 2015 highest 10 76.8 74.6 2.2 60 1 1973 2015 2014 2015 highest 11 77.2 75.0 2.2 60 1 1973 2015 2014 2015 highest 12 76.9 74.8 2.1 60 1 1966,1973 2015 2014 2015 highest 18 72.7 71.1 1.6 55 1 1973 2015,2016,2018 2014 2015 highest 2016,2018 24 76.3 74.9 1.4 55 1 1973 2015,2016 2014 2015 highest 2016 36 76.0 74.9 1.1 48 3 1973 2017 2014 2015 top-tenth 2018 48 75.7 74.9 0.8 42 4 1974,1975 2018 2014 2015 top-tenth 2019 60 75.3 74.8 0.5 33 8 1973,1976 2018 2007 2015 top-third