1991-2020 Degrees Fahrenheit 1 42.0 44.0 -2.0 28 50 1976 2016 1955 1954 normal 2 52.2 50.5 1.7 63 15 1976 1963 1955 1954 top-third 2007 3 58.3 56.7 1.6 63 15 1976 2016 1955 1954 top-third 4 63.5 62.0 1.5 66 12 1976 1963,2016 1955 1954 top-third 1990 5 66.7 65.5 1.2 60 17 1967 1954 1955 1954 top-third 1999 6 68.4 67.2 1.2 62 15 1967 2016 1955 1954 top-third 7 68.4 66.9 1.5 66 11 1967 2016 1955 1954 top-third 8 66.3 65.5 0.8 63 14 1951 2012 1955 1954 top-third 2000,2005 9 63.7 63.3 0.4 58 19 1951 2012 1955 1954 top-third 10 60.6 60.4 0.2 54 23 1951 2012 1955 1954 top-third 1983,2018 11 57.4 57.7 -0.3 49 28 1979 2012 1955 1954 normal 12 55.1 55.7 -0.6 46 31 1979 2012 1955 1954 normal 18 58.9 59.5 -0.6 43 33 1951 2012 1952 1955 normal 2010 24 55.0 55.7 -0.7 44 32 1979 2017 1952 1955 normal 1989,1990 36 55.7 55.6 0.1 57 18 1979,1980 2017 1953 1955 top-third 2020 48 55.8 55.6 0.2 55 19 1951,1962 2018 1955 1956 top-third 60 55.5 55.6 -0.1 51 22 1962 2016 1955 1956 top-third 1991