1991-2020 Degrees Fahrenheit 1 26.4 34.4 -8.0 4 59 1977 2023 1982 1993 bottom-tenth 2 30.4 36.3 -5.9 7 56 1977 2002 1984 1993 bottom-third 3 35.5 39.6 -4.1 8 52 1977 2002 1984 1993 bottom-third 4 40.3 44.0 -3.7 5 55 1977 2002 1982 1993 bottom-tenth 1978 5 46.1 49.0 -2.9 8 52 1977 2017 1984 1993 bottom-third 1978 6 51.4 53.5 -2.1 13 47 1977 2017 1984 1993 bottom-third 1965 7 55.5 57.0 -1.5 18 42 1977 2017 1993 1992 bottom-third 1979,2014 8 57.6 59.0 -1.4 21 39 1977 2017 1993 1992 normal 1990 9 58.4 59.6 -1.2 23 37 1977 2017 1993 1992 normal 2004,2014 10 57.9 59.2 -1.3 23 37 1977 2012 1993 1992 normal 1996 11 56.2 57.9 -1.7 17 43 1977 2017 1993 1992 bottom-third 1976,1985,1990 12 54.2 56.1 -1.9 16 44 1968 2013 1993 1992 bottom-third 18 53.4 55.2 -1.8 14 44 1968,1978 2017 1983 1993 bottom-third 1966,1997 24 54.2 56.1 -1.9 12 46 1968 2013 1983 1993 bottom-third 1966,1983,2015 36 55.2 56.1 -0.9 29 27 1970 2013,2022 1990 1993 normal 1997 48 55.6 56.0 -0.4 32 22 1970 2023 1991 1993 normal 2016,2017 60 55.4 56.0 -0.6 28 24 1970,1971 2021,2023 1991 1993 normal