1991-2020 Degrees Fahrenheit 1 21.3 20.3 1.0 61 22 2014 1998 1963 1961 top-third 2 20.8 18.5 2.3 67 15 1963 2002 1963 1944 top-third 3 17.9 19.7 -1.8 44 38 2014 2002 1963 1961 normal 1966 4 23.1 23.5 -0.4 55 25 1977 2002 1963 1961 top-third 1944 5 29.9 28.4 1.5 67 13 1977 2002 1963 1954 top-third 2005 6 34.8 33.9 0.9 66 14 1977 2002 1963 1954 top-third 2010 7 39.4 38.9 0.5 64 16 1977 2002 1963 1954 top-third 2004,2010 8 43.4 42.9 0.5 63 17 1977 2002 1963 1954 top-third 9 46.2 45.6 0.6 66 14 1977 2002 1963 1954 top-third 10 46.9 46.8 0.1 61 19 1977 2002 1963 1954 top-third 2020 11 46.9 46.7 0.2 62 18 1951 2002 1963 1954 top-third 1992,2008 12 45.5 45.4 0.1 58 22 1951 2002 1963 1954 top-third 18 40.0 41.6 -1.6 36 41 1952 2017 1963 1955 normal 1969 24 43.8 45.4 -1.6 30 47 1952 2017 1963 1961 normal 1981 36 43.5 45.4 -1.9 19 56 1953 2013,2018 1963 1962 bottom-third 1947,1965,1971,1978 48 43.5 45.4 -1.9 18 55 1968 2002 1963 1961 bottom-third 1958,1960,1996 60 43.8 45.4 -1.6 27 44 1955,1969,1970,1972 2002 1963 1958 normal 1956,1976