1991-2020 Degrees Fahrenheit 1 54.4 53.4 1.0 53 22 1967 2015 2005 1999 top-third 2 48.5 47.2 1.3 59 16 1967 2010 2005 1999 top-third 3 42.0 40.7 1.3 64 11 1956 2012 2005 2004 top-third 1980,2004 4 36.5 35.3 1.2 63 11 1967 2012 2004 1999 top-third 1999,2009,2020 5 34.3 31.6 2.7 68 5 1971 2012 2004 1998 top-tenth 6 32.0 30.3 1.7 63 9 1971 2012 2004 2002 top-third 1999 7 32.6 30.9 1.7 63 9 1971 2012 2004 2002 top-third 8 34.5 32.7 1.8 66 6 1971 2012 2004 2002 top-tenth 1991 9 37.3 35.5 1.8 66 6 1956 2012 2004 2002 top-tenth 10 40.2 38.5 1.7 66 6 1971 2012 2004 2002 top-tenth 11 42.8 41.0 1.8 66 5 1963 2012 2004 2006 top-tenth 12 44.7 42.8 1.9 67 3 1959,1963 2012 2004 2006 top-tenth 18 -99 38.8 -99 -99 -99 1971 2017 normal 24 -99 42.9 -99 -99 -99 1966,1967,1971 2013 normal 36 -99 43.1 -99 -99 -99 1967 2012 normal 48 -99 43.0 -99 -99 -99 1966,1968 2013 normal 60 -99 43.1 -99 -99 -99 1967 2013 normal