1991-2020 Degrees Fahrenheit 1 57.2 60.4 -3.2 12 67 1964 1997 1977 1997 bottom-third 2 56.7 59.2 -2.5 22 57 1964 1992 1977 1997 bottom-third 1956 3 56.2 58.1 -1.9 31 48 1948 1992 1991 1997 normal 4 55.4 57.1 -1.7 29 49 1948 1992 1982 1997 normal 1960 5 54.9 56.0 -1.1 38 40 1949 1992,2014 1985 1997 normal 1958 6 54.4 55.4 -1.0 42 36 1949 2015 1991 1997 normal 2011 7 55.1 55.6 -0.5 50 28 1949 2015 1995 1997 normal 1989,1994,2002,2009 8 56.0 56.6 -0.6 46 32 1949 2015 1995 1997 normal 9 57.3 57.6 -0.3 55 23 1949 2015 1995 1997 top-third 2009,2019 10 58.3 58.4 -0.1 59 19 1949 2015 1995 1997 top-third 1970 11 58.8 58.9 -0.1 57 20 1949 2015 1995 1997 top-third 1970,2022 12 59.2 59.3 -0.1 57 19 1949 2015 1995 1997 top-third 18 58.4 57.9 0.5 64 11 1950 2015 1995 1997 top-third 1984,1988,2014,2017 24 59.6 59.2 0.4 62 12 1950 2016 1996 1997 top-third 36 59.9 59.2 0.7 66 6 1950 2016 1997 1994 top-tenth 1994 48 59.4 59.2 0.2 59 11 1952 2017,2018 1995 1997 top-third 1995 60 59.4 59.1 0.3 62 6 1952,1953,1956 2018 1995 1997 top-tenth 1988,1994