1991-2020 Degrees Fahrenheit 1 22.8 23.0 -0.2 42 31 2014 1998 1994 1992 normal 2 20.6 20.9 -0.3 46 26 1979 1998 1994 1992 normal 1989 3 23.3 22.1 1.2 52 20 1979 2002 1994 1992 top-third 4 27.4 25.7 1.7 56 16 2014 2002 1994 1992 top-third 5 32.4 30.5 1.9 59 13 1977 2002 1994 1983 top-third 2006 6 37.8 35.9 1.9 59 13 1977 2017 1994 1983 top-third 7 41.8 40.7 1.1 58 13 1977 2017 1994 1954 top-third 8 45.3 44.6 0.7 53 18 1977 2017 1994 1992 top-third 1964,1987,1989 9 48.0 47.2 0.8 54 17 1977 2017 1994 1992 top-third 1976,2020 10 49.1 48.4 0.7 55 16 1977 2017 1994 1992 top-third 11 49.0 48.3 0.7 56 15 1977 2002 1994 1992 top-third 1987,2005 12 47.9 47.2 0.7 55 16 2014 2017 1994 1992 top-third 1964,2011 18 42.6 43.4 -0.8 33 37 1979 2017 1994 1992 normal 1976,1998 24 46.2 47.2 -1.0 27 42 2015 2017 1994 1993 normal 1976 36 45.8 47.2 -1.4 17 50 1979 2018 1980 1994 bottom-third 1973,2016 48 46.6 47.2 -0.6 34 31 1980 2002 1994 1993 normal 2011,2015 60 46.7 47.2 -0.5 29 34 1963 2002,2020 1994 1993 normal 1958,1988