1991-2020 Degrees Fahrenheit 1 25.3 19.2 6.1 61 15 2019 1954 1997 1999 top-third 2 21.8 17.6 4.2 64 12 1950,1979 1992 1999 1998 top-third 3 23.8 18.2 5.6 69 6 1950,1979 1992 1999 1998 top-tenth 4 27.8 21.1 6.7 74 1 1979 2000 1999 2000 highest 5 31.0 25.6 5.4 74 1 1979 2000 1999 2000 highest 6 34.5 31.0 3.5 70 5 1979 2016 1999 1998 top-tenth 7 39.3 36.3 3.0 68 7 1952,1978 2016 1997 1999 top-tenth 8 43.0 40.4 2.6 67 8 1952,1979 2016 1997 1999 top-third 9 45.0 42.8 2.2 66 8 1952 2016 1999 1999 top-third 1999 10 45.7 43.7 2.0 65 9 1952 2016,2022 1997 1999 top-third 1981,2021 11 45.4 43.5 1.9 65 9 1952 2016 1998 1999 top-third 12 44.6 42.4 2.2 68 6 1952 2016 1999 1992 top-tenth 18 41.1 38.6 2.5 70 3 1952 2013 1999 2000 top-tenth 2016 24 44.2 42.4 1.8 68 4 1952 2022 1999 1992 top-tenth 1989,1992 36 44.2 42.4 1.8 69 1 1952 2000 1999 2000 highest 48 42.8 42.4 0.4 53 15 1953 1992 1999 1993 top-third 60 42.2 42.4 -0.2 45 21 1954 1992 1999 1993 top-third 1988