1991-2020 Degrees Fahrenheit 1 27.6 24.2 3.4 80 13 1955 2012 1957 1918 top-third 2 16.7 17.2 -0.5 63 30 1913 2012 1957 1954 top-third 1952 3 14.5 13.3 1.2 74 19 1912 2012 1957 1921 top-third 1961 4 13.6 12.8 0.8 72 18 2014 2012 1957 1921 top-third 5 15.7 15.6 0.1 69 19 1979 2012 1957 1921 top-third 6 20.2 20.0 0.2 69 18 1920 2012 1957 1921 top-third 1915 7 24.5 25.0 -0.5 64 21 1920 2012 1957 1921 top-third 8 29.1 29.7 -0.6 60 24 1920 2012 1957 1954 top-third 1954 9 33.4 33.7 -0.3 62 22 1951 2012 1957 1921 top-third 10 35.7 36.4 -0.7 58 24 1951 2012 1957 1954 top-third 1954,1991,2011 11 37.1 37.8 -0.7 51 31 1951 2012 1957 1922 normal 1961 12 37.1 37.9 -0.8 51 31 1951 2012 1957 1953 normal 1973 18 30.1 31.8 -1.7 36 42 1951 1999 1957 1954 normal 1985 24 35.6 37.8 -2.2 20 57 1952 2017 1957 1955 bottom-third 1912,1953,1955,1969,2014 36 35.8 37.8 -2.0 18 54 1952 2000 1957 1956 bottom-third 1956,1981 48 35.5 37.8 -2.3 12 55 1952 2002 1957 1956 bottom-third 1962,1973 60 35.7 37.7 -2.0 13 50 1953 2002 1957 1957 bottom-third 1956,1957,1974