1991-2020 Degrees Fahrenheit 1 36.2 38.5 -2.3 25 63 1984 1946 1960 1964 bottom-third 2 32.5 35.2 -2.7 24 64 2015 2012 1963 1964 bottom-third 1936,1956 3 30.2 33.5 -3.3 12 76 2015 2012 1959 1964 bottom-third 1959,1970 4 31.0 34.1 -3.1 21 66 1948,1959 2012 1963 1964 bottom-third 5 33.8 36.3 -2.5 24 63 1940,1948 2012 1963 1964 bottom-third 6 37.0 39.4 -2.4 19 68 1940 2012 1963 1964 bottom-third 1938,1978,1993 7 40.6 43.1 -2.5 15 72 1940 2012 1963 1964 bottom-third 1961 8 44.0 46.9 -2.9 10 77 1941 2012 1963 1964 bottom-third 1994 9 47.2 49.9 -2.7 10 77 1941 2012 1963 1964 bottom-third 10 49.2 51.7 -2.5 8 79 1941 2012 1963 1964 bottom-tenth 11 50.3 52.3 -2.0 11 76 1941 2012 1963 1964 bottom-third 1975,1981 12 50.0 52.0 -2.0 9 78 1941 2012 1963 1964 bottom-tenth 1943,1987 18 46.1 47.8 -1.7 19 67 1941 2013 1964 1962 bottom-third 1945,1962,1971,1981,1987 24 50.5 52.0 -1.5 17 69 1941 2012 1964 1962 bottom-third 1948,1966,1970 36 50.1 52.0 -1.9 7 78 1941 2013 1943 1964 bottom-tenth 48 50.3 51.9 -1.6 10 74 1941 2013 1944 1964 bottom-third 1966 60 50.3 51.9 -1.6 8 75 1941,1944 2020 1945 1964 bottom-tenth 1968,1970