Products
SentimenTrader Trading Tools
‍
Backtest Engine
My Trading Toolkit
Correlation Analysis
Seasonality
Market Prediction
Indicators & Data API
‍
Proprietary Indicators & Charts
Market Data API
Strategies & Scanner
‍
50+ Trading Strategies
Smart Stock Scanner
Smart Option Scanner
Research Reports
‍
Research Solutions
Reports Library
Free Resources
Simple Backtest Calculator
Simple Seasonality Calculator
The Kelly Criterion Calculator
Sentiment Geo Map
Public Research Reports
Education
Sentiment Indicators
Technical Indicators
Pricing
Company
About
In the News
Testimonials
Client Success Stories
Contact
Log inLoginSign up
< BACK TO ALL REPORTS

What history tells us about the month of September

Jay Kaeppel
2026-08-31
There tends to be a lot of "fear and loathing" regarding the stock market during September. But how much angst is really warranted? To answer that question, we analyzed 100+ years of history. The results are detailed herein.

Key points:

  • September is the only month that has a negative average and median return over the last 106 years
  • However, the complicating factor is that results can vary widely from year to year
  • September in mid-term election years has shown worse-than-average results
  • September tends to show early strength followed by significant weakness

September has historically been the weakest month for stocks

The old adage states that "In the long run, the stock market goes up." Overall, it's hard to argue with that statement. Still, the month of September has shown itself to be problematic at times. As September 2026 looms, should we be concerned? Let's consider the history.

The chart below shows the hypothetical growth of $1 invested in the S&P 500 Index during all months EXCEPT September, starting in January 1920. While the results are by no means a straight-line advance, the lower-left-upper-right nature of the equity curve buttresses the adage above.

What history tells us about the month of September

On the other hand, the chart below shows the hypothetical growth of $1 invested in the S&P 500 Index only during the month of September, also starting in 1920. Notice anything different versus the chart above?

Sorry, you don't have access to this report

Upgrade your subscription plan to get access
Go to Dasboard
PRODUCTS
SentimenTrader
Trading Tools
Indicators & Data API
‍
Strategies & Scanner
‍
Research Reports
FREE
RESOUrCES
Simple Backtest
Calculator
Simple Seasonality
Calculator
The Kelly Criterion
Calculator
Sentiment Geo Map
‍
Public Research Reports
‍
Education
Sentiment Indicators
‍
Technical Indicators
‍
Pricing
Bundle pricing
‍
FAQ
‍
Announcements
‍
COMPANY
‍
About
‍
In the News
‍
Testimonials
‍
Client Success Stories
CONTACT
‍
General Inquiries
‍
Media Inquiries
‍
Financial Professionals Inquiries
‍
© 2026 Sundial Capital Research Inc. All rights reserved.
Setsail Marketing
TermsPrivacyAffiliate Program
Risk Disclosure: The information and tools provided are for research and analytical purposes only and are not intended as investment advice. Market analysis involves uncertainty, and outcomes may differ from expectations. Users should conduct their own due diligence and consider their individual circumstances before making any financial decisions. Past performance is not necessarily indicative of future results.

Hypothetical Performance Disclosure: Hypothetical performance results have many inherent limitations, some of which are described below. No representation is being made that any account will or is likely to achieve profits or losses similar to those shown; in fact, there are frequently sharp differences between hypothetical performance results and the actual results subsequently achieved by any particular trading program. One of the limitations of hypothetical performance results is that they are generally prepared with the benefit of hindsight. In addition, hypothetical trading does not involve financial risk, and no hypothetical trading record can completely account for the impact of financial risk of actual trading. for example, the ability to withstand losses or to adhere to a particular trading program in spite of trading losses are material points which can also adversely affect actual trading results. There are numerous other factors related to the markets in general or to the implementation of any specific trading program which cannot be fully accounted for in the preparation of hypothetical performance results and all which can adversely affect trading results.

Testimonial Disclosure: Testimonials appearing on this website may not be representative of other clients or customers and is not a guarantee of future performance or success.