1925-2000 Degrees Fahrenheit 1 15.0 2.2 12.8 92 8 2012 1981 1925 1926 top-tenth 2 9.0 3.0 6.0 80 19 1934 2001 1926 1926 top-third 1940 3 11.0 5.9 5.1 81 18 1943 2001 1926 1926 top-third 4 16.5 10.8 5.7 90 9 1934 2003 1926 1926 top-tenth 5 21.8 16.7 5.1 91 8 1934 2003 1926 1926 top-tenth 6 26.6 22.2 4.4 91 8 1934 2003 1926 1926 top-tenth 7 30.2 26.6 3.6 89 10 1934 2003 1926 1926 top-tenth 1994 8 32.5 29.4 3.1 86 13 1934 2003 1926 1926 top-third 9 33.2 30.3 2.9 86 13 1934 2003 1926 1926 top-third 10 32.2 29.6 2.6 83 16 1956 2018 1926 1926 top-third 2001 11 30.3 27.9 2.4 83 16 1956 2016 1926 1926 top-third 12 27.4 26.0 1.4 68 31 1956 2020 1926 1926 top-third 1930,1935,1982 18 -99 24.7 -99 -99 -99 1957,1972 2020 normal 24 -99 26.0 -99 -99 -99 1957 2017 normal 36 -99 25.9 -99 -99 -99 1957 2017,2018 normal 48 -99 25.9 -99 -99 -99 1975 2020 normal 60 -99 25.9 -99 -99 -99 1976 2020 normal