1991-2020 Degrees Fahrenheit 1 21.1 28.5 -7.4 9 76 1978 2017 1980 1981 bottom-third 2 18.1 26.9 -8.8 6 79 1978 1998 1979 1981 bottom-tenth 3 20.8 28.1 -7.3 5 80 1978 2002 1979 1981 bottom-tenth 2014 4 25.8 31.5 -5.7 6 78 1977 2002 1979 1981 bottom-tenth 1970 5 30.5 35.8 -5.3 4 79 1977 2002 1978 1981 bottom-tenth 6 36.1 40.6 -4.5 4 79 1977 2017 1978 1981 bottom-tenth 7 41.1 45.0 -3.9 4 79 1977 2017 1978 1981 bottom-tenth 8 45.1 48.6 -3.5 5 77 1977 2017 1978 1981 bottom-tenth 9 47.8 51.0 -3.2 4 78 1977 2017 1978 1981 bottom-tenth 10 48.7 52.0 -3.3 2 80 1977 2017 1977 1981 bottom-tenth 1963 11 48.9 51.8 -2.9 4 78 1977 2017 1977 1981 bottom-tenth 12 48.0 50.7 -2.7 9 73 1977 2017 1979 1981 bottom-third 1968 18 44.9 47.3 -2.4 11 69 1979 2017 1980 1981 bottom-third 1970,1980 24 48.5 50.7 -2.2 11 69 1978 2017 1980 1981 bottom-third 1959,1962 36 48.6 50.7 -2.1 8 70 1979 2013 1981 1977 bottom-tenth 1968,1977 48 48.3 50.6 -2.3 3 73 1980 2013,2019 1980 1981 bottom-tenth 60 48.4 50.6 -2.2 3 71 1981 2020 1981 1979 bottom-tenth 1979