1991-2020 Degrees Fahrenheit 1 23.7 28.9 -5.2 17 81 1934 2017 1980 1981 bottom-third 2 21.6 28.6 -7.0 10 88 2015 2017 1979 1981 bottom-tenth 2014 3 25.0 30.4 -5.4 14 83 1936 1932 1979 1981 bottom-third 4 29.2 33.7 -4.5 17 80 1977 2002 1979 1981 bottom-third 5 33.4 37.8 -4.4 9 88 1977 2017 1979 1981 bottom-tenth 1970,2003 6 38.2 42.3 -4.1 8 89 1977 2017 1979 1981 bottom-tenth 1968 7 42.9 46.5 -3.6 9 88 1977 2017 1979 1981 bottom-tenth 1970 8 46.5 49.7 -3.2 9 88 1977 2017 1979 1981 bottom-tenth 1959,1970,2015 9 48.9 51.8 -2.9 12 85 1977 2017 1981 1981 bottom-third 1981 10 49.5 52.5 -3.0 11 86 1977 2017 1979 1981 bottom-third 1979 11 49.4 52.0 -2.6 17 80 1977 2017 1981 1981 bottom-third 1938,1940,1973,1981 12 48.2 50.7 -2.5 20 77 1927 2017 1981 1980 bottom-third 1948 18 45.0 47.8 -2.8 8 87 1941,1979 2017 1979 1981 bottom-tenth 1928,1945,1964,2015 24 48.1 50.6 -2.5 11 84 1928 2017 1979 1981 bottom-third 1952 36 48.4 50.6 -2.2 16 77 1929 2018,2023 1981 1978 bottom-third 1941,1943,1946 48 48.1 50.6 -2.5 4 87 1930 2023 1980 1981 bottom-tenth 60 48.2 50.5 -2.3 4 85 1931 2020,2023 1981 1980 bottom-tenth 1937,1944,1945