S&P 500 · Monthly Heatmap — Monthly Return Seasonality: Historical Heatmap
Monthly Seasonality — Century-spanning heat map of monthly returns, identifying statistical seasonal tilts and calendar anomalies.
Comprehensive heatmap of monthly returns since 2000. Historically, November and April record the highest win rates, while September exhibits the most pronounced tendency toward negative performance.
What this page answers
Across a 27-year historical window, the highest-conviction month for the S&P 500 is November (advancing in +77% of historical observations), while the most vulnerable is February (+48%). Calendar seasonality reflects empirical probabilities rather than mechanical arbitrage — individual calendar years can and do diverge substantially.
Comprehensive heatmap of monthly returns since 2000. Historically, November and April record the highest win rates, while September exhibits the most pronounced tendency toward negative performance. The data is refreshed by the History of Market pipeline and published as a stable JSON endpoint for research, citation, and AI-agent use.
The plate
Latest Snapshot
- Updated
- 2026-09-08
S&P 500 — monthly historical win rates and seasonal tendencies
| Month | Positive months share |
|---|---|
| January | +52% |
| February | +48% |
| March | +59% |
| April | +70% |
| May | +74% |
| June | +59% |
| July | +67% |
| August | +63% |
| September | +52% |
| October | +62% |
| November | +77% |
| December | +65% |
Complete record (12 rows). Raw dataset: https://historyofmarket.com/api/sp500/monthly.json
Data & Source
GET /api/sp500/monthly.json — Canonical dataset endpoint.
Exchange closing prices · Company filings · Robert Shiller · FRED · NBER.
FAQ
Which calendar month has historically demonstrated the strongest win rate for the S&P 500?
November, advancing in +77% of sampled years; the weakest calendar period is February (+48%).
Where does this data come from?
History of Market combines public market and macro datasets — exchange closing prices, company filings, Robert Shiller, FRED, NBER, and the UBS Global Investment Returns Yearbook (Dimson–Marsh–Staunton). The exact endpoint for this panel is linked below.
How often is it updated?
Daily-tier datasets refresh after the U.S. market close, with a broader weekly refresh on Sunday. The timestamp shown on this page comes from the JSON payload.
Can I use the data?
Yes, for research and education with attribution to History of Market. Upstream data sources retain their own terms.