1991-2020 Degrees Fahrenheit 1 59.2 65.3 -6.1 4 90 1973 2011 1931 1931 bottom-tenth 1987 2 54.6 61.1 -6.5 3 91 1958 2011 1931 1931 bottom-tenth 3 52.8 57.2 -4.4 6 88 1958 2017 1931 1931 bottom-tenth 1960,1965 4 50.5 54.0 -3.5 13 79 1958 2017 1931 1931 bottom-third 1960 5 48.6 52.3 -3.7 8 84 1973 2017 1931 1931 bottom-tenth 6 49.0 52.4 -3.4 8 84 1973 2017 1931 1931 bottom-tenth 1947,1960 7 51.1 54.3 -3.2 8 84 1977 2017 1931 1931 bottom-tenth 8 54.5 56.9 -2.4 18 74 1977 2017 1931 1931 bottom-third 9 57.5 59.7 -2.2 17 75 1977 2017 1931 1931 bottom-third 1942,2010 10 59.9 62.1 -2.2 17 75 1977 2017 1931 1931 bottom-third 1939,1959,1961,1964,1969,1976,1988 11 61.6 63.8 -2.2 20 72 1977 2017 1931 1931 bottom-third 1941 12 -99 64.7 -99 -99 -99 1977 2017 normal 18 -99 60.6 -99 -99 -99 1977 2017 normal 24 -99 64.7 -99 -99 -99 1977 2000 normal 36 -99 64.6 -99 -99 -99 1977 2018 normal 48 -99 64.6 -99 -99 -99 1977 2019,2020 normal 60 -99 64.5 -99 -99 -99 1977 2020 normal