1991-2020 Degrees Fahrenheit 1 5.5 17.3 -11.8 6 70 1992 2003 1973 1978 bottom-tenth 2 6.5 17.8 -11.3 2 72 1992 1981 1979 1978 bottom-tenth 3 15.1 22.0 -6.9 6 68 1992 2018 1973 1978 bottom-tenth 4 22.3 27.5 -5.2 5 69 1992 2018 1973 1978 bottom-tenth 5 28.8 33.2 -4.4 6 68 1992 2018 1973 1978 bottom-tenth 6 34.0 38.2 -4.2 4 70 1992 2018 1973 1978 bottom-tenth 1988 7 38.4 42.1 -3.7 6 68 1992 2018 1975 1978 bottom-tenth 8 41.2 44.5 -3.3 8 66 1992 2018 1977 1978 bottom-third 1968 9 41.9 45.3 -3.4 5 69 1992 2018 1973 1978 bottom-tenth 10 42.0 45.0 -3.0 7 67 1992 2018 1976 1978 bottom-tenth 1988 11 41.4 44.1 -2.7 10 64 1992 2018 1977 1978 bottom-third 1949,1962,1972 12 40.0 42.5 -2.5 18 56 1965 2018 1976 1978 bottom-third 18 40.2 41.1 -0.9 37 35 1993 2018 1978 1967 normal 2008 24 41.4 42.5 -1.1 35 37 1993 2018 1977 1978 normal 1959,1960,1998 36 41.0 42.4 -1.4 34 36 1976,1994 2018 1978 1964 normal 1955,1988 48 40.5 42.2 -1.7 13 55 1976 2019 1978 1972 bottom-third 1986 60 40.3 42.1 -1.8 8 58 1976 2020,2021,2022 1978 1974 bottom-third 1953,1974,1980