Options and futures have expiration dates. Most of the time those dates pass quietly. But four times a year — the third Friday of March, June, September and December — three big instruments expire on the same day: stock options, index options (like SPX and NDX), and index futures (ES, NQ). The old name for the day is "triple witching." It's a catalyst of a different kind: no new information about any company, but a massive, mechanical reshuffling of positioning.
Why volume explodes
As expiration approaches, options market makers who sold calls and puts must keep their books hedged by trading the underlying stock or futures. Near expiry, those hedges get twitchy: a small move in the underlying forces large re-hedges, which is why gamma — the rate of change of an option's delta — becomes the whole story. On witching Friday, open interest in expiring SPX options alone routinely exceeds a trillion dollars of notional, and the hedging flow around it shows up as the year's biggest volume days, often 1.5–2x a normal Friday.
The signature pattern is the last hour: futures and the cash index pin to the strike prices where the most options open interest sits, volume surges into the 4pm close, and the futures market keeps trading the settlement shuffle until 9am the next morning (quarterly futures settle at a special opening print).
The 2026 dates
Triple witching falls on the third Friday of the quarterly month: March 20, June 19, September 18, December 18, 2026. (When the third Friday is a market holiday the expiry shifts to Thursday — none of the 2026 dates are affected.) Single-stock and ETF options also expire that day, so the re-hedging reaches individual names, especially heavily traded mega-caps where weekly and monthly open interest stack up.
What it does — and doesn't — mean for your stocks
The honest answer: witching is a flow event, not an information event. Studies of witching weeks show no reliable directional drift in the index; what you get instead is elevated volume, wider intraday ranges, and a tendency for stocks to "pin" at round strikes into the close. Where it matters practically:
Technical levels lie more. Support and resistance get run over by hedging flow; breakout signals on witching afternoon carry less information than usual.
End-of-day moves are noisy. A stock ramping into 3:50pm may simply be dealer hedging, not accumulation. It often unwinds Monday.
It sets up the next catalyst. Post-expiry, the options market rebuilds from clean books — the new positioning that forms in the following week is a better read on sentiment than anything on the day itself.
So treat witching like weather, not news: expect heavy chop in the final hour, don't read conviction into it, and let the following week's cleaner tape tell you what the market actually thinks.