1991-2020 Degrees Fahrenheit 1 45.9 41.1 4.8 64 12 1950 1987 1997 1988 top-third 2 33.4 35.5 -2.1 31 45 1950 2012 1997 1994 normal 1966 3 32.7 30.1 2.6 62 14 1950 2012 1997 1992 top-third 4 28.5 26.5 2.0 57 19 1950 2012 1997 1992 top-third 5 28.3 25.2 3.1 64 11 1950 1992,2012 1997 1992 top-third 1999 6 28.4 25.9 2.5 63 12 1979 2012 1997 1992 top-third 7 30.9 28.5 2.4 64 11 1979 2012 1997 1992 top-third 8 34.6 32.2 2.4 67 8 1950 2012 1997 1992 top-third 1987,2005,2021 9 38.2 36.1 2.1 66 9 1979 2012 1997 1992 top-third 10 41.1 39.4 1.7 65 10 1979 2012 1997 1992 top-third 11 43.4 41.5 1.9 65 9 1952 2012 1997 1992 top-third 12 44.2 42.4 1.8 64 10 1951,1952 2016 1997 1992 top-third 18 36.2 36.9 -0.7 46 27 1951 2016 1997 1993 normal 1954,1976,2018 24 41.7 42.4 -0.7 39 33 1952 2000 1997 1993 normal 1985,2020 36 41.0 42.3 -1.3 26 44 1952 2000 1997 1994 normal 48 41.4 42.4 -1.0 34 34 1953 1992 1997 1995 normal 1976 60 40.8 42.4 -1.6 20 46 1954 1992 1997 1996 bottom-third 1957,1958,1976