1991-2020 Degrees Fahrenheit 1 61.4 59.7 1.7 74 18 1978 2017 1989 1986 top-third 2 -99 57.7 -99 -99 -99 1978 2017 normal 3 -99 57.7 -99 -99 -99 1978 2017 normal 4 -99 59.3 -99 -99 -99 1977 2017 normal 5 -99 62.2 -99 -99 -99 1977 2017 normal 6 -99 65.5 -99 -99 -99 1977 2017 normal 7 -99 68.4 -99 -99 -99 1977 2017 normal 8 -99 70.5 -99 -99 -99 1977 2017 normal 9 -99 72.0 -99 -99 -99 1977 2017 normal 10 -99 72.7 -99 -99 -99 1977 2017 normal 11 -99 72.6 -99 -99 -99 1977 2017 normal 12 -99 71.9 -99 -99 -99 1977 2017 normal 18 -99 69.8 -99 -99 -99 1978 2017 normal 24 -99 71.9 -99 -99 -99 1978 2017 normal 36 -99 71.9 -99 -99 -99 1979 2018 normal 48 -99 71.9 -99 -99 -99 1980 2019 normal 60 -99 71.9 -99 -99 -99 1981 2020,2021 normal