1991-2020 Degrees Fahrenheit 1 23.1 28.4 -5.3 22 78 1977 1932 2009 2010 bottom-third 2 25.8 30.9 -5.1 20 80 1977 1932 2001 2010 bottom-third 3 31.1 34.7 -3.6 21 77 1977 1932 2003 2010 bottom-third 1934,1943,1946 4 36.4 39.3 -2.9 29 68 1977 1932 2009 2010 bottom-third 1931,1938,2009 5 42.4 44.4 -2.0 40 57 1977 1932 2009 2010 normal 1939,1957 6 47.4 48.9 -1.5 48 49 1977 1932 2009 2010 normal 1939,1975,1997 7 51.5 52.5 -1.0 60 37 1977 1932 2010 2010 normal 1942,1954,1969,2010 8 54.0 54.6 -0.6 70 27 1977 2016 2010 2008 top-third 1949 9 55.0 55.2 -0.2 74 23 1977 2016 2010 2008 top-third 1974 10 54.8 54.7 0.1 77 20 1925 2016 2010 2008 top-third 2000 11 53.9 53.3 0.6 84 13 1925 2012,2013,2017 2010 2008 top-third 2008 12 51.8 51.4 0.4 80 17 1925 2013 2010 2007 top-third 18 50.7 50.5 0.2 74 19 1941 2017 2010 2008 top-third 24 51.3 51.3 0.0 75 18 1926 2013 2010 2008 top-third 36 51.0 51.3 -0.3 70 19 1941,1942,1970 2022,2023 2010 2009 top-third 1993,2002,2004,2016 48 51.0 51.3 -0.3 64 22 1971 2023 2004 2010 top-third 2003 60 51.4 51.2 0.2 66 17 1944,1945 2021,2023 2006 2010 top-third 2003