The S&P 500 closed Q3 up 7.8%, which is notable considering that Q3 is historically the weakest quarter of the year — averaging just 0.8% since 1950. By comparison, the other three quarters average between 2.1% and 4.2%.
Since 1950, there have been 16 instances where the S&P 500 posted a Q3 gain of 7% or more. In 14 of those 16 cases, the index went on to rise in Q4 as well — with an average gain of 5.0% over the final three months of the year.
This adds to conviction for the remainder of 2025, as Q4 is already the strongest quarter of the year on average, and a strong Q3 has historically further improved the odds of a strong finish.
Of course, anything can happen in markets, but historical seasonality tilts the probabilities in favor of strength into year-end.
