1991-2020 Degrees Fahrenheit 1 49.9 48.7 1.2 66 19 1940 2017 2003 2002 top-third 2 49.6 49.4 0.2 57 28 1984 2022 2003 2002 top-third 1975,1997,2021 3 53.3 52.0 1.3 68 17 1977 2017 2003 2002 top-third 1971,2021 4 57.2 56.0 1.2 73 12 1977 2017 2003 1999 top-third 1995 5 61.0 60.6 0.4 68 17 1977 2017 2003 1999 top-third 1950,1985 6 65.0 64.7 0.3 69 16 1977 2017 2003 2000 top-third 1957,2013 7 67.6 67.5 0.1 67 18 1977 2017 2003 2000 top-third 1952,1965 8 69.2 69.3 -0.1 64 20 1977 2017 2003 2000 top-third 1981,2021 9 70.0 69.9 0.1 68 16 1977 2017 2003 1999 top-third 1965 10 69.7 69.6 0.1 67 17 1977 2012,2017 2003 2002 top-third 2002 11 68.6 68.6 0.0 63 21 1977 2017 2003 2000 top-third 1986 12 66.9 67.3 -0.4 61 23 1984 2017 2003 2002 top-third 1964,1992 18 65.9 66.4 -0.5 59 25 1984 2017 2003 2001 top-third 1992 24 66.6 67.3 -0.7 54 29 1962 2017 1998 2003 normal 1958,1986,1987,2011 36 66.8 67.2 -0.4 59 23 1961 2018 2003 2003 top-third 1955,2003,2016 48 66.8 67.2 -0.4 56 25 1962 2019 1998 2003 top-third 1955,2010,2011 60 67.0 67.1 -0.1 58 22 1962,1963 2020 1999 2003 top-third 1999,2005