1991-2020 Degrees Fahrenheit 1 27.5 35.3 -7.8 6 70 1964 2017 1964 1968 bottom-tenth 2 25.3 29.9 -4.6 14 62 1984 2017 1966 1968 bottom-third 3 24.7 25.6 -0.9 43 33 1984 1995,1999,2015 1968 1967 normal 4 22.5 23.7 -1.2 30 44 1992 1999 1968 1967 normal 1963,2007 5 23.6 25.1 -1.5 30 44 1992 2018 1968 1967 normal 6 27.1 28.2 -1.1 32 42 1992 2018 1968 1967 normal 1980 7 30.6 32.2 -1.6 25 49 1992 2018 1968 1967 normal 8 34.3 36.1 -1.8 23 51 1992 2018 1968 1967 bottom-third 1974 9 37.5 39.4 -1.9 22 52 1992 2018 1968 1967 bottom-third 1974 10 39.7 41.5 -1.8 23 51 1992 2018 1968 1967 bottom-third 2008 11 40.5 42.4 -1.9 18 56 1992 2018 1968 1967 bottom-third 1953,1966,1974,1998 12 40.2 42.5 -2.3 17 57 1984 2018 1968 1967 bottom-third 1949 18 35.1 37.7 -2.6 12 60 1993 2018 1966 1968 bottom-third 1953,1975,1977 24 39.9 42.4 -2.5 13 59 1993 2018 1966 1968 bottom-third 1965 36 40.8 42.4 -1.6 24 46 1975 2018 1967 1968 normal 1963,1964,1971,1988 48 40.7 42.2 -1.5 26 42 1976 2019 1968 1967 normal 1967,1986 60 40.4 42.1 -1.7 11 55 1977 2020,2021 1966 1968 bottom-third 1965,1966,1978,1980