1991-2020 Degrees Fahrenheit 1 13.7 17.0 -3.3 32 50 1977 2006 1996 1998 normal 2 20.0 19.8 0.2 54 28 1977 2002 1997 1998 normal 2003 3 26.3 24.9 1.4 65 15 1977 2002 1997 1998 top-third 2020 4 32.5 30.8 1.7 69 11 1977 2002 1997 1998 top-third 2021 5 39.1 36.9 2.2 73 7 1977 2016 1998 1995 top-tenth 6 44.4 42.4 2.0 73 7 1977 2002 1998 1995 top-tenth 7 48.4 46.5 1.9 74 6 1977 2002 1998 1999 top-tenth 8 50.6 49.2 1.4 71 9 1977 2002 1998 1995 top-third 9 52.1 50.1 2.0 74 6 1977 2002 1998 1999 top-tenth 2012 10 52.0 49.7 2.3 76 4 1951 2002 1998 1999 top-tenth 2017 11 50.2 48.1 2.1 74 6 1951 2013 1998 1999 top-tenth 12 48.8 45.8 3.0 78 2 1951 2013 1998 1999 top-tenth 2017 18 46.9 44.6 2.3 74 3 1952 2017 1998 1999 top-tenth 24 47.2 45.8 1.4 70 7 1952 2000,2013 1998 1999 top-tenth 36 45.8 45.8 0.0 56 19 1953 2013 1998 1989 top-third 48 45.5 45.8 -0.3 49 24 1968,1973 2002 1998 1991 top-third 2012,2015,2017 60 45.7 45.8 -0.1 48 23 1970,1972 2002 1998 1989 top-third 2011