1991-2020 Degrees Fahrenheit 1 77.5 80.0 -2.5 21 48 1977 1997 1965 1966 bottom-third 2 70.3 76.1 -5.8 2 66 1975 2000 1967 1966 bottom-tenth 3 68.5 72.9 -4.4 3 65 1975 2004 1967 1966 bottom-tenth 1998 4 66.4 69.7 -3.3 7 61 1975 2014 1964 1966 bottom-tenth 1971 5 63.8 67.2 -3.4 6 60 1975 2014 1955 1966 bottom-tenth 1998 6 62.4 65.3 -2.9 6 56 1975 2014,2015 1967 1966 bottom-tenth 7 62.7 65.1 -2.4 9 53 1975 1996 1965 1966 bottom-third 8 64.1 66.6 -2.5 8 53 1973 1996 1962 1966 bottom-third 1972,1985 9 66.7 69.1 -2.4 8 53 1973 1996 1965 1966 bottom-third 1965,1974,1987 10 69.3 71.6 -2.3 11 50 1973 1996 1965 1966 bottom-third 1976 11 71.5 73.6 -2.1 13 48 1973 1996 1965 1966 bottom-third 1985 12 72.8 74.9 -2.1 14 47 1973 1996 1966 1963 bottom-third 1956,1998 18 69.6 71.7 -2.1 10 47 1976 2015 1966 1963 bottom-third 1962 24 72.7 74.9 -2.2 8 48 1973,1974 2018 1966 1963 bottom-third 1971 36 72.6 74.9 -2.3 6 45 1975 2017,2018 1967 1963 bottom-third 1972 48 -99 74.9 -99 -99 -99 1975,1976 2018 normal 60 -99 74.8 -99 -99 -99 1977 2018 normal