Historical data indicates that mid to late September is typically a weak period for the S&P 500. Analysts note that the optimal seasonal sell-point is around September 17, and the last couple of weeks of the month are often particularly brutal for stocks. Over the past two decades, the week following the 11th trading day of September has shown negative returns 68% of the time. This trend suggests that investors should be cautious during this period, especially in light of recent rate cut news.