1991-2020 Degrees Fahrenheit 1 50.9 56.9 -6.0 3 73 1961 2017 1975 1981 bottom-tenth 2 48.8 51.5 -2.7 18 58 1975 2012 1980 1981 bottom-third 3 44.4 47.1 -2.7 15 61 1958 2017 1980 1981 bottom-third 2013 4 40.6 44.1 -3.5 11 65 1978 2017 1980 1981 bottom-third 1960,2014 5 39.4 43.0 -3.6 9 67 1978 2017 1978 1981 bottom-third 6 40.4 43.6 -3.2 11 64 1977 2012 1978 1981 bottom-third 7 42.4 45.5 -3.1 7 68 1977 2017 1978 1981 bottom-tenth 1968,2015 8 45.5 48.3 -2.8 9 65 1977 2017 1978 1981 bottom-third 9 48.5 51.3 -2.8 7 67 1977 2017 1978 1981 bottom-tenth 10 51.3 53.7 -2.4 10 64 1977 2017 1978 1981 bottom-third 11 53.3 55.4 -2.1 11 63 1977 2017 1980 1981 bottom-third 12 53.9 56.2 -2.3 5 69 1977 2017 1978 1981 bottom-tenth 1975 18 49.7 52.0 -2.3 9 65 1978 2017 1980 1981 bottom-third 1970,1980,2015 24 54.3 56.1 -1.8 7 66 1978 2017 1980 1981 bottom-tenth 1959,1962,1965,1968,1980 36 54.2 56.1 -1.9 6 66 1979 2018 1980 1981 bottom-tenth 1963,1965,1977 48 54.3 56.1 -1.8 8 63 1980 2019,2020 1981 1977 bottom-third 1965 60 54.1 56.0 -1.9 2 68 1981 2020 1981 1980 bottom-tenth 1979