1991-2020 Degrees Fahrenheit 1 4.1 5.4 -1.3 58 37 1912 2006 1997 1998 normal 2 7.6 8.6 -1.0 61 30 1918 2006 1997 1998 top-third 1955 3 14.2 14.6 -0.4 61 28 1920 2002 1997 1998 top-third 2001 4 21.8 21.4 0.4 67 21 1920 2016 1997 1998 top-third 2001,2015 5 28.8 28.0 0.8 68 18 1920 2016 1997 1998 top-third 6 35.1 33.9 1.2 70 15 1920 2016 1997 1998 top-third 7 39.3 38.4 0.9 70 15 1920 2016 1997 1998 top-third 8 42.0 41.2 0.8 68 15 1951,1952 2002,2016 1997 1998 top-third 9 43.6 42.4 1.2 71 12 1951 2002 1998 1998 top-third 1998 10 43.6 42.0 1.6 73 10 1951 2002 1998 1995 top-third 11 42.1 40.4 1.7 71 10 1951 2002 1998 1995 top-third 1988,2013 12 40.9 37.9 3.0 80 1 1951 1999 1998 1999 highest 18 39.3 36.5 2.8 76 3 1951 2017 1998 1999 top-tenth 24 39.6 37.9 1.7 69 7 1952 2000 1998 1999 top-tenth 36 37.9 37.8 0.1 56 15 1952 2001 1998 1989 top-third 1923 48 37.2 37.8 -0.6 44 22 1952 2002 1998 1995 top-third 1985,1995,2010 60 37.6 37.7 -0.1 45 17 1953 2002 1998 1992 top-third 2012,2018