1991-2020 Degrees Fahrenheit 1 63.4 59.7 3.7 76 2 1964 1997 1991 1992 top-tenth 2 62.1 58.4 3.7 77 1 1948 1992 1991 1992 highest 3 60.6 57.4 3.2 77 1 1948 1992 1991 1992 highest 4 59.5 56.4 3.1 76 1 1948 1992 1991 1992 highest 5 57.4 55.4 2.0 73 4 1949 2016 1991 1992 top-tenth 6 56.3 54.7 1.6 73 4 1949 2015 1991 1992 top-tenth 1997,2014 7 56.4 54.9 1.5 74 3 1949 2015 1991 1992 top-tenth 1997,2014 8 57.2 55.8 1.4 73 4 1949 2015 1991 1992 top-tenth 9 57.9 56.9 1.0 72 5 1949 2015 1991 1992 top-tenth 2014,2020 10 58.5 57.6 0.9 70 7 1949 2015 1991 1992 top-tenth 2014 11 59.0 58.2 0.8 69 7 1949 2015 1991 1984 top-tenth 1984 12 59.0 58.5 0.5 60 15 1949 2015 1991 1984 top-third 1959 18 57.0 57.2 -0.2 53 21 1949,1950 2016 1991 1989 top-third 1989 24 58.5 58.4 0.1 59 14 1950 2016 1991 1988 top-third 1988,2006,2014 36 58.1 58.4 -0.3 51 20 1950 2016,2017 1991 1990 top-third 1990,2014 48 58.1 58.4 -0.3 50 19 1951,1952 2018 1991 1991 top-third 1990,1991 60 58.3 58.3 0.0 53 15 1952,1953 2018 1991 1988 top-third 1993,2004,2008