1991-2020 Degrees Fahrenheit 1 63.7 63.5 0.2 55 20 1950 2007 1981 1970 top-third 2 63.7 64.5 -0.8 40 35 1950 2011 1981 1980 normal 1988 3 61.3 63.3 -2.0 15 60 1950 2011 1979 1981 bottom-third 4 58.0 60.5 -2.5 10 65 1950 2012 1979 1981 bottom-third 1995 5 54.3 57.0 -2.7 10 65 1975 2012 1975 1981 bottom-third 1953,1967 6 50.7 53.3 -2.6 16 59 1950,1975 2012 1979 1981 bottom-third 1951 7 46.6 49.2 -2.6 17 58 1979 2020 1979 1981 bottom-third 1952 8 42.9 45.2 -2.3 20 55 1984 2018 1979 1981 bottom-third 9 40.4 42.2 -1.8 25 48 1979 2018 1979 1981 normal 1966 10 39.8 41.0 -1.2 32 41 1973 2018 1980 1981 normal 1966 11 40.1 41.3 -1.2 32 41 1973,1992 2018 1980 1981 normal 1997 12 41.4 42.5 -1.1 35 38 1973,1992 2018 1980 1981 normal 18 45.2 46.1 -0.9 44 29 1984 2018 1980 1981 normal 24 42.3 42.5 -0.2 52 19 1993 2018 1981 1982 top-third 1997 36 41.9 42.4 -0.5 49 20 1975 2018 1981 1982 top-third 1983,1999,2009,2010 48 40.9 42.3 -1.4 31 36 1976 2019,2020 1980 1981 normal 1984,1991 60 41.3 42.2 -0.9 44 21 1977 2020 1981 1959 top-third 1958,1959