1925-2000 Degrees Fahrenheit 1 -2.0 4.8 -6.8 15 85 1990 2016 1965 1971 bottom-third 2 -3.3 3.5 -6.8 9 91 1925 2016 1971 1970 bottom-tenth 1933 3 -0.8 3.6 -4.4 15 84 1965 2001 1971 1970 bottom-third 4 1.7 5.6 -3.9 13 86 1956 2003 1971 1970 bottom-third 5 6.1 9.6 -3.5 13 86 1956 2003 1971 1970 bottom-third 6 11.7 14.8 -3.1 14 85 1956 2003 1971 1970 bottom-third 7 17.0 19.7 -2.7 11 88 1956 2003 1971 1970 bottom-third 8 21.4 23.9 -2.5 11 88 1956 2003 1971 1970 bottom-third 9 24.5 26.7 -2.2 12 87 1956 2003 1971 1970 bottom-third 10 25.4 27.8 -2.4 9 90 1956 2003 1971 1970 bottom-tenth 1957 11 24.8 27.4 -2.6 6 93 1956 2016 1971 1970 bottom-tenth 12 22.8 26.0 -3.2 3 96 1956 2016 1965 1971 bottom-tenth 18 18.5 22.2 -3.7 1 97 1972 2016 1972 1971 lowest 24 23.2 26.0 -2.8 2 96 1957 2016,2017 1957 1971 bottom-tenth 36 24.7 25.9 -1.2 12 85 1973,1974 2017,2018 1967 1971 bottom-third 1951 48 24.7 25.9 -1.2 9 87 1974 2019 1968 1971 bottom-tenth 1934,1956,1968 60 25.2 25.9 -0.7 20 75 1976 2019,2020 1969 1971 bottom-third 1935,1952,1960,1978