There’s an old market saying: “Sell in May and go away.” Most traders have heard it, smirked, and moved on. But the numbers tell a different story. Over the past 70 years, the S&P 500 returned about 4.8% on average from November to April, and only 1.2% from May to October.
This isn’t astrology or coincidence – there are real reasons behind it, and real ways to use it in CFD trading.
Why Seasonality Exists at All
Before looking at charts, it’s important to understand the mechanics. Seasonal patterns aren’t magic – they’re the result of real, repeatable processes.
- Physical production and consumption cycles.
Oil demand rises in winter (heating) and summer (travel). Grain harvests pressure prices during collection. India’s gold demand spikes during the wedding season. These are not psychological quirks – they’re agriculture, climate, and logistics.
- Institutional calendars.
Funds close fiscal years, rebalance portfolios, and lock in profits on predictable schedules.
- Behavioral cycles.
Summer vacations reduce trading volume. In September, everyone returns at once – creating structurally higher volatility.
- Corporate events.
Earnings seasons, dividends, buyback windows – all of these create predictable behavior in index CFDs.
Index CFDs: When Markets Tend to Rise – and When They Don’t
1. S&P 500: September, the Odd One Out
Looking at 50 years of monthly S&P 500 returns, almost every month is positive on average – except September. It’s the only month with a negative average return.
Why? Managers return from summer and take profits, quarterly tax payments drain liquidity, and funds begin year‑end tax planning. What this means for CFD traders:
September doesn’t forbid long positions – it just raises the bar for bullish setups.
Examples:
- September 2023: –4.9%
- September 2022: –9.3%
- September 2020: –3.9%
Different macro environments, same seasonal weakness.
The November Turnaround
After a weak September-October performance, November historically kicks off a strong period for US indices. Portfolio rebalancing, institutional buying, and renewed buybacks all support the market.
Examples:
- November 2023: +8.9%
- November 2022: +5.4%
- November 2020: +10.8%
2. DAX: A European Twist
DAX has a deeper summer slump than US indices because Europe literally goes on vacation. August is structurally weaker, while December often brings a stronger rally as European institutions reposition into year‑end.
3. Oil: Physics Beats Psychology
Seasonality in oil is one of the most grounded in real‑world fundamentals.
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April-May: Switching to Summer Blends
The US refineries shift from winter to summer gasoline blends, temporarily reducing crude processing. Inventories rise – but this isn’t bearish; it’s a technical transition before summer demand. Historically, WTI finds support in April.
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May-August: The US Driving Season
From Memorial Day to Labor Day, gasoline demand peaks. Americans drive 10-15% more in summer. Example: WTI rose from $63 to $73 in May-June 2021 – partly due to seasonal demand.
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September-October: The Off‑Season
Gasoline demand drops, heating demand hasn’t started – a structurally weak period for oil. But geopolitics can override it, as in 2026.
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December: OPEC Meetings
Not classic seasonality, but a predictable event that always brings volatility.
4. Gold: India, China, and Real Rates
Gold’s seasonality is shaped by several independent physical demand cycles.
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August-November: The Strongest Period
Because of:
– India’s wedding season and Diwali
– China’s Golden Week
– Western holiday demand.
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January-February: Lunar New Year
A second wave of physical buying.
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May-July: The Quiet Season
Minimal physical demand – unless real interest rates dominate the narrative, which they often do now. In 2025, rising real rates overpowered seasonal strength.
5. Forex: Liquidity and Institutional Flows
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December: Don’t Trade Against Liquidity
The last two weeks of December are dangerous: liquidity collapses, spreads widen, and even good signals behave unpredictably. After December 15, reduce size and activity.
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March-April: Yen Repatriation
Japan’s fiscal year ends March 31. Corporations repatriate profits, strengthening the yen. Example: March 2023 – USD/JPY fell from 137 to 130.
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September-October: Seasonal Dollar Strength
Institutions return from summer, volatility rises, and demand for safe assets supports the dollar.
How to Use Seasonality: A Simple Algorithm
Seasonality isn’t a trading system – it’s a context filter.
- Check the seasonal backdrop for your instrument.
- If it aligns with your signal, treat it as extra confirmation.
- If it contradicts, be more cautious or demand a stronger setup.
Always check macro factors – strong seasonality + strong macro trend = best setups.
- Seasonality against macro = seasonality loses.
The ideal setup: technical signal + macro confirmation + supportive seasonality.
Three Common Traps
- “It didn’t work last year.”
One year isn’t data. Seasonality is built on 20-50 years of averages. - “Everyone knows this, so it doesn’t work.”
Some patterns weaken, but physical cycles (oil, gold) cannot be arbitraged away. - “Seasonality is a signal.”
No – it’s context. November 2008: -7.5% despite being a “strong” month.
- Seasonax – detailed, paid.
- EquityClock.com – free, good starting point.
- MRCI – institutional‑grade commodity research.
- Or build your own stats using 15 years of daily data.
Bottom Line
The market “remembers” the calendar because people, corporations, and physical processes follow rhythms that repeat every year.
Use seasonality as what it truly is: a background factor that shifts probabilities slightly in your favor – not a signal, not a prognosis.
In trading, any statistical edge matters. Seasonality is one of the few edges rooted in real‑world behavior – and one most retail traders ignore.