1991-2020 Degrees Fahrenheit 1 68.6 66.9 1.7 58 18 1967 2018 2013 2012 top-third 1987,1998 2 63.1 62.8 0.3 55 21 1961 2019 2013 2012 top-third 3 57.0 58.2 -1.2 33 43 1960 2012 2013 2012 normal 4 52.5 54.1 -1.6 30 46 1958 2012 2013 2012 normal 1962,1984,1988 5 48.3 51.0 -2.7 10 66 1958,1978 2012 1979 2013 bottom-third 1971 6 47.5 49.5 -2.0 22 53 1978 2012 2003 2013 bottom-third 1987,1988,1993 7 47.1 49.4 -2.3 16 59 1978 2012 1996 2013 bottom-third 1984 8 48.8 50.7 -1.9 22 53 1978 2012 1996 2013 bottom-third 1989 9 51.0 52.9 -1.9 19 56 1958,1977,1978 2017 1997 2013 bottom-third 1988,1993,1994,1997 10 53.4 55.3 -1.9 17 58 1958,1977 2017 1997 2013 bottom-third 1997 11 55.7 57.4 -1.7 19 56 1977 2012,2017 2001 2013 bottom-third 1956,1975,1980 12 57.3 58.8 -1.5 22 53 1977 2012 2001 2013 bottom-third 1984,1989,2015 18 54.7 55.7 -1.0 38 36 1970 2017 1998 2013 normal 1998 24 57.9 58.8 -0.9 34 40 1978 2017 1998 2013 normal 1988 36 59.1 58.8 0.3 61 12 1970,1979 2018,2019 2011 2013 top-third 2000 48 59.1 58.7 0.4 62 10 1980 2019,2020 2011 2013 top-third 60 58.9 58.7 0.2 60 11 1970 2020 2007 2013 top-third 2016,2017,2018