Every fall, the same headlines return: October is dangerous for stocks, and election years make markets nervous. In 2026 both stories arrive at once, with the US midterm elections scheduled for November 3. Before you let a calendar change your portfolio, it is worth looking at what the historical record actually says, and how much weight it deserves.
Where the October reputation comes from
October owns the most famous crashes in US market history. The 1929 crash unfolded over several days in late October. On October 19, 1987, known as Black Monday, the Dow Jones Industrial Average fell 22.6% in a single session, still its largest one-day percentage drop. In October 2008, during the global financial crisis, the S&P 500 suffered one of its worst months in decades.
Those events are memorable, and memory is what gives a month its reputation. But a handful of dramatic days is not the same thing as a reliable pattern.
What the averages say
Across long stretches of market history, September, not October, has been the weakest month for the S&P 500 on average and has finished lower more often than any other month. October’s average return has been closer to middling, because its crashes are offset by strong rebounds in other years.
In fact, October has a second, less famous reputation as a “bear market killer.” Several major declines ended in October:
- October 11, 1990: the low of the bear market around the Gulf War and that year’s recession.
- October 9, 2002: the closing low after the dot-com bust.
- October 12, 2022: the closing low of the 2022 bear market driven by inflation and rapid Fed rate hikes.
So the honest summary is that October has been volatile, not reliably negative. Volatility cuts both ways.
Why seasonal patterns might exist at all
Analysts have offered several explanations for calendar effects, none of them conclusive:
- Fund flows and tax timing: many mutual funds end their fiscal year on October 31, and some selling to harvest tax losses has historically clustered in the fall.
- Quarter-end positioning: portfolio rebalancing around the end of September can add pressure late in the third quarter.
- Behavior: when enough investors expect a weak season, their caution can briefly make it come true, until prices adjust.
The more widely a pattern is known, the more traders try to front-run it, which tends to weaken it over time.
The midterm-year pattern
The four-year presidential cycle is another popular idea. The second year of a presidential term, the midterm year, has historically been the weakest and choppiest of the four, with notable declines in years such as 1962, 1966, 1974, 2002, and 2022. A common explanation is policy uncertainty: markets dislike not knowing which party will control Congress and what that means for taxes, spending, and regulation.
The flip side is the part that gets quoted most often. By the commonly cited count, the S&P 500 has been higher 12 months after every midterm election since World War II, including the period after the 2022 vote. Once the result is known, uncertainty fades, whichever party wins.
Why you should not trade the calendar
These patterns come with serious caveats:
- Tiny samples: there have been only about twenty midterm elections since World War II. A streak built on twenty observations can end at any time.
- Other forces dominate: interest rates, inflation, and corporate earnings move markets far more than the calendar. Our guide to how interest rates move the stock market explains why rates matter so much, and the earnings season guide covers the reports that arrive every October.
- Averages hide the spread: an “average” September includes both sharp losses and solid gains. Any single year can look nothing like the average.
- Costs and taxes: moving in and out of the market to dodge a seasonal dip adds trading costs and possible taxes, and missing even a few of the market’s best days has historically hurt long-term returns.
What to watch this fall instead
Rather than the date on the calendar, the data that tends to move markets in October and November is concrete:
- Third-quarter earnings: results and guidance from the largest companies, which carry heavy weight in the index.
- Inflation reports: the monthly CPI and PCE releases, explained in our CPI vs. PCE guide.
- The Fed: rate decisions and the tone of the post-meeting press conference. See how the Fed sets interest rates.
- The jobs report: covered in our guide to the jobs report and the stock market.
- Treasury yields: especially the 10-year yield, a benchmark for stock valuations.
You can follow upcoming releases on the economic calendar.
The bottom line
October’s reputation rests on a few unforgettable crashes, while September has quietly been the weaker month on average, and October has ended as many bear markets as it started. Midterm years have been bumpy, and the year after has been kind to investors so far. All of it is interesting context, and none of it is a strategy. A plan built around your time horizon and risk tolerance will outlast any calendar pattern. This article is for education only and is not investment advice.
