1991-2020 Degrees Fahrenheit 1 26.5 35.3 -8.8 4 71 1964 2017 1952 1961 bottom-tenth 2 28.2 29.9 -1.7 35 40 1984 2017 1960 1961 normal 3 23.8 25.7 -1.9 30 45 1984 2015 1961 1958 normal 4 20.8 23.8 -3.0 18 55 1992 1999 1960 1961 bottom-third 5 22.3 25.1 -2.8 19 54 1992 2018 1960 1961 bottom-third 6 25.7 28.3 -2.6 18 55 1992 2018 1960 1961 bottom-third 7 29.5 32.3 -2.8 15 58 1992 2018 1960 1961 bottom-third 8 33.7 36.1 -2.4 14 59 1992 2018 1960 1961 bottom-third 2008 9 37.0 39.4 -2.4 12 61 1992 2018 1960 1961 bottom-third 1952 10 39.4 41.6 -2.2 13 60 1992 2018 1960 1961 bottom-third 1960 11 40.5 42.5 -2.0 16 57 1992 2018 1960 1961 bottom-third 1998 12 40.5 42.5 -2.0 17 56 1984 2018 1960 1961 bottom-third 1960 18 35.9 37.8 -1.9 18 53 1993 2018 1961 1961 bottom-third 1961,1979 24 40.9 42.5 -1.6 19 52 1993 2018 1961 1961 bottom-third 1961,1972 36 40.8 42.4 -1.6 18 51 1993,1994 2018 1954 1961 bottom-third 1954,1988 48 41.1 42.3 -1.2 37 30 1976 2019 1961 1961 normal 1953,1955,1961,1964,1970 60 41.0 42.2 -1.2 24 41 1977 2020,2021 1953 1961 normal 1953,1964,1981,1986