1991-2020 Degrees Fahrenheit 1 59.9 57.8 2.1 60 22 1967 1977 1997 1998 top-third 2 54.4 51.5 2.9 71 11 1947 1977 1997 1998 top-third 3 47.6 45.0 2.6 71 11 1950 2012 1997 1998 top-third 4 42.5 38.9 3.6 74 8 1950 2012 1997 1998 top-tenth 5 36.7 34.4 2.3 73 8 2014 2012 1997 1998 top-tenth 6 35.0 32.5 2.5 73 8 2014 2012 1997 1998 top-tenth 7 35.5 32.8 2.7 71 8 2014 2012 1997 1998 top-tenth 8 37.4 34.7 2.7 73 6 2014 2012 1997 1998 top-tenth 2006,2010,2017 9 40.5 37.7 2.8 75 4 1943 2016 1997 1998 top-tenth 10 43.6 40.9 2.7 75 4 1943 2012 1997 1998 top-tenth 11 46.2 43.6 2.6 76 3 1943 2012 1998 1999 top-tenth 2006 12 47.8 45.6 2.2 73 6 1943 2012 1997 1998 top-tenth 2002 18 44.7 41.2 3.5 77 1 1951 1999 1998 1999 highest 24 47.9 45.6 2.3 74 2 1952,1979 2017 1998 1999 top-tenth 36 46.5 45.6 0.9 64 10 1979 2000 1998 1999 top-third 2008 48 45.6 45.6 0.0 54 18 1968 2001,2002 1998 1999 top-third 2014 60 45.7 45.6 0.1 51 19 1969 2002 1998 1999 top-third 2005