1991-2020 Degrees Fahrenheit 1 7.4 16.8 -9.4 9 73 1977 2006 1994 2013 bottom-third 1972 2 10.3 19.6 -9.3 3 79 1977 2002 1977 2013 bottom-tenth 3 17.6 24.7 -7.1 3 77 1977 2002 1977 2013 bottom-tenth 1959 4 25.4 30.6 -5.2 4 76 1977 2002 1986 2013 bottom-tenth 5 32.9 36.8 -3.9 9 71 1977 2016 1996 2013 bottom-third 1959,1963 6 39.1 42.2 -3.1 12 68 1977 2002 1996 2013 bottom-third 1978,1996 7 43.8 46.3 -2.5 16 64 1977 2002 1996 2013 bottom-third 1996 8 46.6 49.0 -2.4 19 61 1977 2002 1994 2013 bottom-third 9 47.9 49.9 -2.0 20 60 1977 2002 2009 2013 bottom-third 1957,1969 10 47.1 49.5 -2.4 14 66 1951 2002 1997 2013 bottom-third 1943,1957,1986 11 45.2 47.9 -2.7 12 68 1951 2013 1997 2013 bottom-third 1963,1970 12 43.0 45.6 -2.6 17 63 1951 2013 2009 2013 bottom-third 18 43.1 44.4 -1.3 40 37 1952 2017 2010 2013 normal 2010 24 46.1 45.6 0.5 60 17 1952 2000,2013 2011 2013 top-third 36 46.3 45.6 0.7 64 11 1953 2013 2012 2013 top-third 48 46.5 45.6 0.9 66 7 1968,1973 2002 2012 2013 top-tenth 60 46.2 45.6 0.6 65 6 1970,1972 2002,2003 2013 2013 top-tenth 2008,2013,2017,2021