1991-2020 Degrees Fahrenheit 1 29.6 35.4 -5.8 6 55 1965 2012 1965 1969 bottom-tenth 2 26.4 30.9 -4.5 7 54 1978 2012 1965 1969 bottom-third 3 23.5 28.7 -5.2 6 55 2014 2012 1970 1969 bottom-tenth 4 24.1 29.1 -5.0 4 57 2014 2012 1970 1969 bottom-tenth 5 26.1 31.2 -5.1 4 56 2014 2012 1970 1969 bottom-tenth 6 29.9 34.5 -4.6 4 56 1977 2012 1970 1969 bottom-tenth 7 34.7 38.6 -3.9 5 55 1977 2012 1970 1969 bottom-tenth 8 39.4 42.6 -3.2 6 54 1977 2012 1965 1969 bottom-tenth 1979 9 43.1 45.9 -2.8 8 52 1977 2012 1965 1969 bottom-third 10 45.0 48.2 -3.2 3 57 1977 2012 1970 1969 bottom-tenth 1994 11 46.1 49.1 -3.0 2 58 1977 2012 1970 1969 bottom-tenth 12 46.2 49.0 -2.8 3 57 1977 2012 1970 1969 bottom-tenth 18 41.5 44.1 -2.6 4 55 1979 2017 1970 1969 bottom-tenth 24 46.9 49.0 -2.1 4 55 1994 2013,2017 1970 1969 bottom-tenth 1979 36 46.9 48.9 -2.0 2 56 1979 2013 1970 1969 bottom-tenth 48 47.0 48.9 -1.9 2 55 1980 2013 1970 1969 bottom-tenth 60 47.2 48.9 -1.7 3 53 1981 2020 1970 1969 bottom-tenth 1971