1991-2020 Degrees Fahrenheit 1 47.2 51.2 -4.0 16 60 1968 2018 1988 1992 bottom-third 2 48.8 49.4 -0.6 39 36 1977,1978 1950 1988 1992 normal 1976,1995 3 48.4 49.6 -1.2 32 43 1977 2017 1988 1992 normal 4 50.1 51.1 -1.0 30 44 1977 2017 1988 1992 normal 1956,1998 5 52.6 54.1 -1.5 25 49 1977 2017 1988 1992 normal 6 56.4 57.8 -1.4 23 51 1977 2017 1988 1992 bottom-third 1967 7 59.5 61.2 -1.7 16 58 1977 2017 1988 1992 bottom-third 2004 8 62.4 63.8 -1.4 18 56 1977 2017 1988 1992 bottom-third 1967 9 64.0 65.6 -1.6 18 56 1977 2017 1982 1992 bottom-third 10 64.6 66.3 -1.7 11 63 1977 2017 1982 1992 bottom-third 1963,1967,1998 11 64.3 66.1 -1.8 6 68 1977 2017 1977 1992 bottom-tenth 1969,1998,2010 12 63.6 65.4 -1.8 6 68 1977 2017 1977 1992 bottom-tenth 1969 18 61.6 62.8 -1.2 17 55 1977 2017 1989 1992 bottom-third 1985,1989,1997,2010,2011,2014 24 64.7 65.4 -0.7 32 40 1977 2017 1990 1992 normal 1990,2004 36 65.2 65.3 -0.1 48 22 1970 2018 1991 1992 top-third 1974,1991,1999,2005,2012 48 65.1 65.3 -0.2 46 22 1970 2019,2020 1991 1992 top-third 1974,1975,1988,1999,2005,2006,2007,2015 60 65.0 65.3 -0.3 38 28 1970 2020 1989 1992 normal 1960,1987,1989,1995,2006