1991-2020 Degrees Fahrenheit 1 56.6 56.9 -0.3 45 31 1961 2017 1966 1968 normal 2 47.7 51.5 -3.8 11 65 1975 2012 1965 1968 bottom-third 3 43.6 47.1 -3.5 11 65 1958 2017 1965 1968 bottom-third 4 40.8 44.1 -3.3 14 62 1978 2017 1968 1967 bottom-third 1996 5 39.5 43.0 -3.5 10 66 1978 2017 1963 1968 bottom-third 6 40.7 43.6 -2.9 14 61 1977 2012 1968 1967 bottom-third 1964 7 42.9 45.5 -2.6 13 62 1977 2017 1968 1967 bottom-third 1956,1981 8 45.9 48.3 -2.4 11 63 1977 2017 1968 1967 bottom-third 9 49.2 51.3 -2.1 13 61 1977 2017 1968 1967 bottom-third 2014 10 51.8 53.7 -1.9 14 60 1977 2017 1968 1967 bottom-third 1961,1966,2014 11 53.6 55.4 -1.8 15 59 1977 2017 1968 1967 bottom-third 1959,1961,2014 12 54.3 56.2 -1.9 14 60 1977 2017 1968 1967 bottom-third 18 49.6 52.0 -2.4 6 68 1978 2017 1968 1968 bottom-tenth 1962,1968 24 53.6 56.1 -2.5 2 71 1978 2017 1969 1968 bottom-tenth 36 54.3 56.1 -1.8 10 62 1979 2018 1965 1968 bottom-third 48 54.4 56.1 -1.7 10 61 1980 2019,2020 1966 1968 bottom-third 1966 60 54.5 56.0 -1.5 11 59 1981 2020 1968 1967 bottom-third 1984