1991-2020 Degrees Fahrenheit 1 33.4 38.3 -4.9 16 69 1960 2012 1969 1968 bottom-third 2 30.0 33.4 -3.4 23 62 1978 2012 1969 1968 bottom-third 1996 3 24.6 30.7 -6.1 8 77 1978 2012 1963 1969 bottom-tenth 4 25.1 30.7 -5.6 7 78 1978 2012 1963 1969 bottom-tenth 5 27.3 32.8 -5.5 5 79 1978 2012 1963 1969 bottom-tenth 6 31.4 36.2 -4.8 6 77 1978 2012 1963 1969 bottom-tenth 7 36.2 40.3 -4.1 6 77 1977,1978 2012,2016 1963 1969 bottom-tenth 2015 8 40.8 44.2 -3.4 7 76 1977 2012,2017 1963 1969 bottom-tenth 9 44.5 47.4 -2.9 7 75 1977 2012 1963 1969 bottom-tenth 1951 10 46.5 49.7 -3.2 5 77 1977 2012 1963 1969 bottom-tenth 1982 11 47.7 50.8 -3.1 4 78 1977 2012 1970 1969 bottom-tenth 12 47.9 50.7 -2.8 6 76 1977 2012 1963 1969 bottom-tenth 2014 18 43.2 45.9 -2.7 7 73 1978 2017 1964 1969 bottom-tenth 1982 24 48.4 50.7 -2.3 9 71 1978 2017 1968 1969 bottom-third 1959,1964 36 48.4 50.7 -2.3 5 73 1979 2018 1964 1969 bottom-tenth 1982 48 48.4 50.6 -2.2 3 73 1980 2019 1970 1969 bottom-tenth 1981,1982 60 48.7 50.6 -1.9 5 69 1981 2020 1965 1969 bottom-tenth 1963,1965,1971