1991-2020 Degrees Fahrenheit 1 32.4 35.1 -2.7 24 53 2015 2017 1948 1949 bottom-third 2 36.3 33.9 2.4 67 10 1978 2023 1948 1949 top-third 3 36.2 35.1 1.1 63 13 1963 2002 1948 1949 top-third 4 38.1 37.9 0.2 59 17 1977 2002 1948 1949 top-third 1954,2022 5 42.6 41.8 0.8 62 14 1977 2002 1949 1950 top-third 6 46.0 46.5 -0.5 51 24 1977 2017 1948 1949 top-third 7 50.2 50.8 -0.6 52 23 1977 2017 1948 1949 top-third 1971,2018 8 53.9 54.1 -0.2 59 16 1977 2017 1949 1950 top-third 1974 9 56.1 56.3 -0.2 59 16 1977 2017 1949 1950 top-third 10 56.9 57.1 -0.2 59 16 1977 2017 1949 1950 top-third 11 56.4 56.9 -0.5 56 19 1977 2017 1949 1950 top-third 12 55.3 55.8 -0.5 55 20 1941 2017 1949 1950 top-third 18 52.3 52.6 -0.3 56 17 1941 2017 1949 1950 top-third 2009 24 55.1 55.7 -0.6 55 18 1941,1968 2017 1949 1950 top-third 36 54.3 55.7 -1.4 44 27 1963 2013,2023 1949 1950 normal 1974,1988,1989 48 54.4 55.7 -1.3 47 22 1964 2023 1949 1950 top-third 1955,1974,1989 60 54.4 55.7 -1.3 46 21 1965 2020,2023 1949 1950 top-third 1990