1991-2020 Degrees Fahrenheit 1 45.0 45.9 -0.9 40 38 1960 2012 1958 1953 normal 2 38.5 40.5 -2.0 35 43 1960 2012 1958 1957 normal 1956 3 33.7 37.2 -3.5 24 54 1979 2012 1958 1957 bottom-third 4 32.9 36.4 -3.5 19 59 1979 2012 1949 1958 bottom-third 1977,2011 5 35.6 38.0 -2.4 29 49 1979 2012 1958 1957 normal 1952,1997 6 39.5 41.2 -1.7 33 45 1979 2012 1958 1957 normal 7 43.8 45.3 -1.5 33 45 1979 2016 1958 1957 normal 2011 8 47.9 49.4 -1.5 33 45 1979 2012 1958 1957 normal 9 50.9 52.8 -1.9 25 52 1979 2012 1958 1957 bottom-third 10 53.0 55.1 -2.1 24 53 1962,1979 2012 1958 1957 bottom-third 1994 11 54.2 56.1 -1.9 24 53 1962 2012 1958 1957 bottom-third 1971,1985 12 54.1 56.1 -2.0 20 57 1962 2012 1958 1957 bottom-third 1971,1985,1997 18 48.7 51.1 -2.4 13 64 1979 2017 1952 1958 bottom-third 1971 24 53.8 56.0 -2.2 12 64 1979 2013,2017 1952 1958 bottom-third 36 54.5 56.0 -1.5 24 51 1979 2013 1953 1958 bottom-third 1972,1974,1996 48 54.8 56.0 -1.2 30 44 1980 2002 1954 1958 normal 1954 60 55.3 56.0 -0.7 39 34 1962 2003 1955 1958 normal 1955,1999