1991-2020 Degrees Fahrenheit 1 49.4 51.2 -1.8 18 42 1988 1971 1972 1973 bottom-third 2 54.0 57.1 -3.1 7 53 1993 1971 1964 1973 bottom-third 1964 3 59.4 61.7 -2.3 8 52 1992 2007,2021 1967 1973 bottom-third 4 62.9 64.4 -1.5 12 48 1992 2021 1972 1973 bottom-third 1987,2014 5 63.5 65.2 -1.7 9 51 1992 2021 1972 1973 bottom-third 1985,1997,2003 6 62.0 64.2 -2.2 4 56 1992 2007 1967 1973 bottom-tenth 7 60.1 61.7 -1.6 11 49 1992 2010 1972 1973 bottom-third 1981 8 56.8 58.4 -1.6 12 48 1992 2012 1972 1973 bottom-third 1966,1980,2014 9 53.0 54.9 -1.9 12 48 1978 2012 1972 1973 bottom-third 1980,1997 10 50.3 51.8 -1.5 20 40 1978 2012 1972 1973 bottom-third 11 48.2 49.9 -1.7 15 45 1978 2012 1972 1973 bottom-third 1981,1992,1993 12 47.4 49.0 -1.6 18 41 1978,2014 2012 1972 1973 bottom-third 1993 18 53.4 54.0 -0.6 29 30 1993 2012 1972 1973 normal 2004 24 48.6 49.0 -0.4 33 25 1979 2017 1973 1974 normal 1987,2019 36 48.1 49.0 -0.9 21 36 1979 2012 1972 1973 normal 1984,2003 48 48.1 48.9 -0.8 19 37 1980,1981 2013 1973 1974 normal 60 47.9 48.9 -1.0 14 41 1982 2002,2013,2020 1973 1974 bottom-third 1984