The S&P 500 is heading into what is historically its strongest season, but a specific set of market conditions is flashing a warning sign for investors in the immediate short-term.

While the fourth quarter has delivered the best average returns for the index since 1950, historical data shows that a strong year-to-date performance through September often leads to a flat or negative October, creating a conflicting picture for Wall Street.

A Strong Fourth Quarter Is On The Cards

Data compiled by Carson Research’s Chief Market Strategist, Ryan Detrick, highlights this divergence. The fourth quarter has been a boon for investors, boasting an average return of 4.2%, significantly outperforming all other quarters.

“Q4 is the best quarter of the year historically, and it isn’t even really close,” Detrick notes, pointing to data showing the S&P 500 finishes higher 80% of the time in the final three months of the year.

Q4 is the best quarter of the year historically and it isn't even really close. pic.twitter.com/IhZDmsHegu

— Ryan Detrick, CMT (@RyanDetrick) September 28, 2025

October Can Be Somber After Strong 9 Months

However, the path through the fourth quarter may not be smooth. ...