S&P 500 in September: seasonality and history
Since 1957, the S&P 500 has risen in September in 43% of years (30 of 70), with an average return of −0.81% and a median of −0.47%. That makes September its #12 month of 12.
Average−0.81%
Years up43%
Best year2010 · +8.76%
Worst year1974 · −11.93%
The seasonal path through September
Cumulative sum of each day's average return through September, all years since 1957.
| Strongest days | Avg | Up |
|---|---|---|
| Sep 16 | +0.26% | 57% |
| Sep 28 | +0.23% | 61% |
| Sep 2 | +0.19% | 57% |
| Weakest days | Avg | Up |
|---|---|---|
| Sep 29 | −0.35% | 44% |
| Sep 21 | −0.30% | 33% |
| Sep 23 | −0.25% | 33% |
Seasonal trend windows touching September
- ▼ Bearish Sep 3 – Sep 10 · 8 days · seasonal Σ −0.51%
- ▼ Bearish Sep 17 – Sep 30 · 14 days · seasonal Σ −1.43%
September in recent years
| Year | S&P 500 in September |
|---|---|
| 2026 | −0.45% |
| 2025 | +3.53% |
| 2024 | +2.02% |
| 2023 | −4.87% |
| 2022 | −9.34% |
| 2021 | −4.76% |
| 2020 | −3.92% |
| 2019 | +1.72% |
| 2018 | +0.43% |
| 2017 | +1.93% |
Questions
Is September a bad month for the S&P 500?
On average, yes: −0.81% since 1957, rising in 43% of years. But the range is wide, from −11.93% in 1974 to +8.76% in 2010, so an average is a tendency, not a forecast.
What are the strongest days in September?
Sep 16 (+0.26%, up 57% of years), Sep 28 (+0.23%, up 61% of years), Sep 2 (+0.19%, up 57% of years).