1991-2020 Degrees Fahrenheit 1 21.0 24.0 -3.0 26 50 1979 1995 1974 1972 normal 2 13.4 20.4 -7.0 11 65 1984 1995 1974 1972 bottom-third 3 13.0 19.5 -6.5 10 64 1992 1995 1973 1974 bottom-third 1968 4 16.8 22.1 -5.3 9 65 1992 2018 1973 1974 bottom-third 5 22.3 26.4 -4.1 10 64 1992 2018 1973 1974 bottom-third 6 27.4 31.2 -3.8 8 66 1992 2018 1973 1974 bottom-third 7 31.8 35.7 -3.9 7 67 1992 2018 1973 1974 bottom-tenth 1965 8 35.7 39.4 -3.7 7 67 1992 2018 1973 1974 bottom-tenth 9 38.3 41.7 -3.4 7 67 1992 2018 1973 1974 bottom-tenth 10 39.7 42.7 -3.0 9 65 1992 2018 1973 1974 bottom-third 1965 11 39.5 42.6 -3.1 7 67 1992 2018 1973 1974 bottom-tenth 12 39.3 42.0 -2.7 10 64 1992 2018 1974 1972 bottom-third 1968,1976 18 35.7 38.4 -2.7 12 60 1993 2018 1974 1972 bottom-third 1989 24 39.2 42.0 -2.8 8 64 1993 2018 1974 1972 bottom-third 1977 36 38.9 41.9 -3.0 3 67 1993,1994 2018 1975 1974 bottom-tenth 48 39.1 41.7 -2.6 2 66 1976 2019 1975 1974 bottom-tenth 60 39.3 41.6 -2.3 3 63 1977 2022 1975 1974 bottom-tenth