1991-2020 Degrees Fahrenheit 1 39.4 38.3 1.1 60 25 1960 2012 1967 1961 top-third 2 31.8 33.4 -1.6 41 44 1978 2012 1967 1966 normal 3 28.2 30.7 -2.5 29 56 1978 2012 1965 1967 normal 1988 4 28.7 30.7 -2.0 31 54 1978 2012 1965 1967 normal 5 30.0 32.8 -2.8 25 59 1978 2012 1965 1967 bottom-third 6 33.6 36.2 -2.6 19 64 1978 2012 1965 1967 bottom-third 1948 7 37.6 40.3 -2.7 15 68 1977,1978 2012,2016 1965 1967 bottom-third 8 41.5 44.2 -2.7 11 72 1977 2012,2017 1965 1967 bottom-third 9 44.7 47.4 -2.7 9 73 1977 2012 1963 1967 bottom-third 10 47.3 49.7 -2.4 12 70 1977 2012 1963 1967 bottom-third 1980 11 48.0 50.8 -2.8 9 73 1977 2012 1963 1967 bottom-third 12 48.2 50.7 -2.5 11 71 1977 2012 1963 1967 bottom-third 1962,1980 18 43.7 45.9 -2.2 13 67 1978 2017 1964 1967 bottom-third 1971,1977,1994 24 48.3 50.7 -2.4 7 73 1978 2017 1963 1967 bottom-tenth 1980 36 48.9 50.7 -1.8 13 65 1979 2018 1965 1967 bottom-third 1959,1971 48 48.9 50.6 -1.7 11 65 1980 2019 1966 1967 bottom-third 1962,1966,1969 60 48.9 50.6 -1.7 12 62 1981 2020 1967 1964 bottom-third 1962,1964,1969