1991-2020 Degrees Fahrenheit 1 60.2 60.0 0.2 56 22 1964 1997 2021 2020 top-third 2 58.8 58.8 0.0 56 22 1964 1992 2015 2021 top-third 3 57.8 57.8 0.0 57 21 1948 1992 2021 2020 top-third 1959,2019 4 56.9 56.8 0.1 58 19 1948 1992 2019 2021 top-third 5 56.2 55.7 0.5 61 16 1949 2014,2015,2016 2019 2021 top-third 1984,2000 6 55.3 55.0 0.3 58 19 1949 2015 2019 2021 top-third 1993,2019 7 55.7 55.2 0.5 63 14 1949 2015 2021 2021 top-third 1988,2000,2021 8 56.5 56.2 0.3 60 17 1949 2015 2013 2021 top-third 1970,2005 9 57.5 57.2 0.3 61 16 1949 2015 2019 2021 top-third 2000 10 58.3 58.0 0.3 62 15 1949 2015 2019 2021 top-third 1959,2017 11 58.8 58.6 0.2 61 15 1949 2015 2017 2021 top-third 2017 12 59.1 58.9 0.2 59 16 1949 2015 2013 2021 top-third 1959 18 58.0 57.6 0.4 61 13 1949,1950 2015,2016 2014 2021 top-third 24 59.7 58.8 0.9 67 6 1950 2016 2018 2021 top-tenth 36 60.0 58.8 1.2 68 3 1950 2016 2018 2017 top-tenth 48 -99 58.8 -99 -99 -99 1951,1952,1955,1956 2018 normal 60 -99 58.7 -99 -99 -99 1952,1953,1956 2018 normal