I​​nvestors have a general idea of which times of the year are better or worse for investing. Adages such as “Santa Claus rally” and “Sell in May and go away” reflect some of these ingrained beliefs.

But is there anything to these well-worn Wall Street sayings? A closer look at the past 50 years in the equity markets may surprise you.

Sources: Dow Jones Indices LLC, AthenaInvest

The chart above ranks the months of the year by a score of the highest maximum, minimum, and average return combined with the lowest standard deviation. The bars show the absolute range of minimum to maximum monthly returns, while the line shows the average monthly return.

When ranked this way, April is the most attractive month to invest, while September is the worst. January, usually considered one of the best months to invest because of new-year inflows, is actually in the middle of the pack. November is usually viewed as wild due to election-based market fluctuations, but in reality, it is a great month for investing. September is the only month with a negative average return, at -0.7%.

The largest drawdowns have occurred in October (most notably during the 1987 Black Monday crash), August, and March, with February and September also experiencing losses greater than 10%. Six months, led by January, have maximum returns exceeding 10%. October is the wildest month of the year, with a historical return range of 33% from high to low and a standard deviation of 6%. Finally, June is the calmest month, with a return range of 15% and a standard deviation of 3.5%.

Based on this historical data, an investor would want to be in the market in January, out during February and March, back invested in April through the end of July, out during September and October, and then full throttle through the end of the year.

But, of course, every year is different, which is why investors shouldn’t rely on old Wall Street adages to guide their long-term investment decisions.

From the behavioral viewpoint

What is going on?

1. WYSIATI—“What you see is all there is”: Daniel Kahneman introduced this cognitive bias to describe the human tendency to make decisions or judgments based solely on the information readily available to them, without accounting for what they don’t know or haven’t considered.
2. Narrative fallacy: We use patterns, stories, and shortcuts to help understand what is going on around us, even if it means making up stories and adopting plausible theories. This tendency creates a natural overemphasis on story over data that often results in faulty analysis and poor investment decisions.
3. Fooled by randomness: Overconfidence and the fallacy of control lead us to believe that we can comprehend and predict random markets and make reliable short-term investment decisions. We have a hard time accepting randomness. We want to believe that there must be some way to forecast and navigate largely unpredictable markets.

What can investors do?

1. Develop a needs-based financial plan that separates short- and long-term investments, and stay fully invested over time. Build a strategy-diverse and risk-managed equity portfolio that can be resilient in a variety of market conditions and is designed for the long run.
2. Reframe your investment time horizon and learn to understand markets as a long-term return distribution. The more draws from the distribution, the better the outcome.
3. Work with an experienced financial advisor who has been through different market environments. They can provide perspective and coaching to help investors stay on track and remain focused on long-term goals. Financial advisors can add significant value through behavioral coaching, helping clients understand how the changing nature of risk and return can be managed through data-driven investment decisions.

This is an edited version of an article that was first published by AthenaInvest on Nov. 10, 2025.

The opinions expressed in this article are those of the author and the sources cited and do not necessarily represent the views of Proactive Advisor Magazine. This material is presented for educational purposes only.