Since I came to southwestern Ohio in the late 1970s, I have recorded the dates for many of the earliest snows. There is no scientific method here, but rather a shaping of personal context.
The earliest flurries fell on October 5 of 2014. The first snow of almost half a foot came on October 30 of 1993. On November 11, 1984, I made the first snowball of the winter. This year the first snow, about four inches, arrived on December 13. The latest first snow came on December 31, 1998.