1991-2020 Degrees Fahrenheit 1 25.5 35.3 -9.8 2 73 1964 2017 1948 1948 bottom-tenth 2 20.5 29.9 -9.4 4 71 1984 2017 1948 1948 bottom-tenth 3 17.7 25.7 -8.0 6 69 1984 2015 1948 1948 bottom-tenth 4 -99 23.8 -99 -99 -99 1992 1999 normal 5 -99 25.1 -99 -99 -99 1992 2018 normal 6 -99 28.3 -99 -99 -99 1992 2018 normal 7 -99 32.3 -99 -99 -99 1992 2018 normal 8 -99 36.1 -99 -99 -99 1992 2018 normal 9 -99 39.4 -99 -99 -99 1992 2018 normal 10 -99 41.6 -99 -99 -99 1992 2018 normal 11 -99 42.5 -99 -99 -99 1992 2018 normal 12 -99 42.5 -99 -99 -99 1984 2018 normal 18 -99 37.8 -99 -99 -99 1993 2018 normal 24 -99 42.5 -99 -99 -99 1993 2018 normal 36 -99 42.4 -99 -99 -99 1993,1994 2018 normal 48 -99 42.3 -99 -99 -99 1976 2019 normal 60 -99 42.2 -99 -99 -99 1977 2020,2021 normal