(doesnt have the best of discounts if i remember past years)
I guess both Halloween and Black Friday / Cyber Monday sales are similar in that most deals are the same or worse than the Winter Sale but a few games will have the best prices then. But the Friday/Monday sale will almost certainly be within 30 days of the Winter Sale so it is possible to buy earlier and get the better price if it ends up being lower.
2016 Thanksgiving in the US was on the same date as this year and the sale was Nov 22-29. However, the last two sales started on Black Friday and 2016 was the last year where the Winter Sale was at the very beginning of December. Since then, the Winter Sale has started on the 12 (Tues), 13 (Thu), 11 (Wed), 16 (Wed), and 13 (Mon) (usually lasting 3 weeks and ending between the 2nd and 5th of January). Not that I've had much luck so far but I'll guess Dec 13 - Jan 3 for the Winiter Sale and Nov 25 - 29 for the Friday/Monday sale.