1991-2020 Degrees Fahrenheit 1 42.4 46.0 -3.7 19 58 1960 2012 1975 1977 bottom-third 2 33.3 42.1 -8.8 3 74 1960 1976 1960 1977 bottom-tenth 3 30.2 39.8 -9.6 1 76 1978 1990 1978 1977 lowest 4 31.4 39.5 -8.1 1 76 1978 2012 1978 1977 lowest 5 34.9 40.9 -6.0 2 74 1977 2012 1977 1976 bottom-tenth 6 38.0 43.6 -5.6 2 74 1977 2012 1977 1976 bottom-tenth 7 42.7 47.1 -4.4 2 73 1977 2017 1977 1976 bottom-tenth 8 46.6 50.6 -4.0 2 73 1977 2017 1977 1976 bottom-tenth 9 50.1 53.3 -3.2 4 71 1977 2017 1977 1976 bottom-tenth 1970 10 52.0 55.2 -3.2 3 72 1977 2017 1977 1976 bottom-tenth 11 53.4 56.1 -2.7 4 71 1977 2017 1977 1976 bottom-tenth 12 53.9 56.2 -2.3 5 70 1977 2012,2017,2020 1977 1976 bottom-tenth 18 48.1 51.9 -3.8 1 74 1978 2017 1978 1977 lowest 24 52.6 56.1 -3.5 1 73 1978 2017 1978 1977 lowest 36 54.0 56.1 -2.1 4 69 1979 2018 1970 1977 bottom-tenth 48 54.1 56.1 -2.0 2 70 1980 2020 1970 1977 bottom-tenth 1964,1970 60 54.7 56.0 -1.3 15 56 1981 2020 1972 1977 bottom-third 1962,1972