1991-2020 Degrees Fahrenheit 1 18.7 35.0 -16.3 4 121 1933 1995 1903 1902 bottom-tenth 2 19.2 31.2 -12.0 8 117 1933 2005 1903 1902 bottom-tenth 3 19.6 30.1 -10.5 9 115 1933 1981 1903 1902 bottom-tenth 4 23.7 32.4 -8.7 9 115 1933 2017 1903 1902 bottom-tenth 5 29.2 36.5 -7.3 9 115 1933 2017 1903 1902 bottom-tenth 6 34.6 41.5 -6.9 7 117 1917,1933 2017 1903 1902 bottom-tenth 1929,1979 7 40.0 46.5 -6.5 8 116 1917 2017 1903 1902 bottom-tenth 8 44.0 50.5 -6.5 7 117 1917 2017 1903 1902 bottom-tenth 9 46.9 53.0 -6.1 8 116 1913 2017 1903 1902 bottom-tenth 10 48.2 53.8 -5.6 9 115 1913,1917 2017 1903 1902 bottom-tenth 1909 11 48.4 53.6 -5.2 10 114 1913 2017 1903 1902 bottom-tenth 1909 12 47.2 52.9 -5.7 7 117 1913 2018 1903 1902 bottom-tenth 1929 18 44.7 49.1 -4.4 20 103 1913 2018 1903 1902 bottom-third 1909 24 48.8 52.9 -4.1 24 99 1913,1914 2018 1903 1902 bottom-third 1924 36 49.3 52.9 -3.6 35 87 1914,1915,1918 2019 1903 1903 bottom-third 1908,1923,1975 48 -99 52.8 -99 -99 -99 1920 2019,2020 normal 60 -99 52.7 -99 -99 -99 1917 2021 normal