History Says September Is a Terrible Month for the S&P 500 Index and for Other Stocks. Here's Why I'm Still Investing Anyway.

Key Points There's not much to do about the "September Effect," unless you sell out of stocks. That introduces other problems, which investors would do best to avoid. Staying the course is the best move for most investors. 10 stocks we like better than S&P 500 Index › Here we are in September. It's back-to-school month for millions of kids. Summer will give way to fall around Sept. 23. Some leaves in your region may have begun to change color. For many reasons, including cooler temperatures, we often look forward to or enjoy September. But many investors actually dread it. Statistically speaking, September tends to be a lousy month for the stock market. According to Dow Jones Market data (as of 2025): Missed Nvidia in 2009?