Ryan Detrick, Chief Market Strategist at Carson Group LLC, warned Monday that August’s strong performance could spell trouble for September markets.
Historical Pattern Shows Perfect Negative Track Record
“Could a really good August mean trouble in Sept?” Detrick wrote on X. “When S&P 500 in Aug up >1% and at least 5 ATHs [All-time high] (like ’25), the following month of September has never been higher.”
According to Carson Investment Research data spanning 1950-2025, when August posts gains exceeding 1% with five or more all-time highs, September has delivered negative returns 100% of the time.
August 2025 Meets Danger Criteria
The S&P 500 gained 1.9% in August to a peak at 6,508 points on Thursday while recording five new all-time highs, matching the historical pattern that has preceded every September decline.
The SPDR S&P 500 ETF Trust (NYSE:SPY) closed Monday at $644.95, down 0.61%.
September Statistics Paint Grim Picture
Historical data shows that concerning metrics, when August meets these criteria:
- Average September return: -2.3%
- Median September return: -1.9%
- Success rate: 0.0%
The pattern has held through eight previous instances from 1961-2021, including notable declines like September 2008’s -8.9% drop and 2021’s -4.8% fall.
Market Context Supports Caution
September has historically been Wall Street’s worst month. Bank of America data shows the S&P 500 has declined 56% of September months since 1928, averaging a 1.17% loss.
“September is reliably bad for the broader U.S. stock market,” said Paul Ciana, technical strategist at Bank of America.
The warning comes as markets navigate potential Federal Reserve rate cuts, with CME FedWatch showing 89.7% odds of a 25-basis-point reduction this month.
Previous August hot streaks that led to September selloffs include 1987 (+3.5% followed by -2.4%), 2020 (+7.0% followed by -3.9%), and 2014 (+3.8% followed by -1.6%).
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Disclaimer: This content was partially produced with the help of AI tools and was reviewed and published by Benzinga editors.
Photo courtesy: Andrew Angelov/Shutterstock
