+1 sessions
Median return -2.28%Completed observations: 11
- Middle 50%
- -3.04% … -0.47%
- Positive returns
- 27%
Snowflake · Sigma Moves
Closed-period price moves, measured against their own history. One engine. Five markets. No forecasts.
Latest closed period
Snowflake's latest move against its own history.
SNOW Very rare
-7.70%
-3.56σ
About once every 73 trading sessions
15 comparable moves / 1,095 observations
What happened afterwards
All history-qualified moves of at least 2.5σ. Results after the event are descriptive statistics, not trading instructions.
+7 sessions
Median return -0.88%Completed observations: 11
- Middle 50%
- -7.35% … +1.57%
- Positive returns
- 45%
+30 sessions
Median return +0.49%Completed observations: 11
- Middle 50%
- -9.29% … +14.93%
- Positive returns
- 55%
Every rare move, in context
Instrument: SNOW (price return)
| Date | σ | Move | Observed rarity | +1 sessions | +7 sessions | +30 sessions |
|---|---|---|---|---|---|---|
| 29 Jan 2026 | -3.56σ | -7.70% | About once every 73 trading sessions15 comparable moves / 1,095 observations | -3.35% | -11.75% | -10.39% |
| 4 Dec 2025 | -5.00σ | -11.41% | About once every 151 trading sessions7 comparable moves / 1,058 observations | -2.55% | -8.30% | -12.17% |
| 28 Aug 2025 | +7.84σ | +20.27% | 1 times in 4 years1 comparable moves / 990 observations | -0.97% | -6.41% | +0.49% |
| 8 Aug 2025 | -2.93σ | -7.11% | About once every 57 trading sessions17 comparable moves / 976 observations | +0.04% | +0.47% | +19.72% |
| 1 Aug 2025 | -5.14σ | -8.27% | 4 times in 4 years4 comparable moves / 971 observations | +1.69% | -5.83% | +10.13% |
| 22 May 2025 | +4.62σ | +13.43% | About once every 132 trading sessions7 comparable moves / 923 observations | -1.54% | +2.94% | +10.00% |
| 9 Apr 2025 | +3.21σ | +13.21% | About once every 74 trading sessions12 comparable moves / 893 observations | -4.43% | -9.36% | +34.42% |
| 3 Apr 2025 | -3.05σ | -9.10% | About once every 74 trading sessions12 comparable moves / 889 observations | -6.70% | +3.32% | +30.86% |
| 6 Mar 2025 | -4.73σ | -11.89% | About once every 174 trading sessions5 comparable moves / 869 observations | +1.72% | +0.11% | -8.19% |
| 28 Jan 2025 | +2.60σ | +7.12% | About once every 50 trading sessions17 comparable moves / 843 observations | -2.73% | -0.88% | -18.96% |
| 21 Nov 2024 | +12.72σ | +32.71% | Not previously observed in 3 years0 comparable moves / 800 observations | -2.28% | +2.68% | -7.30% |
The number has a method behind it
Sigma measures the size of a log return relative to volatility estimated before the period. Rarity is counted from actual historical standardized moves, not inferred from a normal distribution.
σt = ln(Ct / Ct−1) / vtvt ← t−1, t−2, …
Volatility adapts to the market regime with EWMA (λ = 0.94 for daily and weekly observations). Current-period returns are excluded. Each historical σ uses its own prior volatility.
Both directions count toward rarity. Reference history spans up to five years. A period with no prior exceedances is labelled unprecedented in the observed sample; it is never given an invented recurrence interval.
Stock observations use split-adjusted price returns, without dividend reinvestment. Commodities are explicitly labelled ETF price proxies; they do not represent spot commodity prices.
Questions behind the sigma
What does a 3σ move mean?
The period log return is three times the volatility estimated from earlier periods. Sigma is signed: negative for declines and positive for rises.
Why not calculate rarity from a normal distribution?
Market returns have heavy tails and changing volatility. We count actual past absolute sigma exceedances for the same instrument and period.
Does “once every 200 days” predict the next event?
No. It is the number of historical observed periods divided by comparable moves. Events can cluster and the market regime can change.
How much history is required?
At least three years of valid standardized observations, after a one-year volatility warm-up. This normally requires approximately four years of source history.
Are all instruments directly comparable?
The engine is shared, but each instrument has its own prices, calendar, volatility and reference sample. Commodity cards use explicitly labelled ETF proxies.
What happens on quiet days?
The page shows the largest covered standardized move, the complete rarity scale and recent records. Missing data is reported separately from market calm.
For information only. Historical observations are not investment advice and do not predict future moves. A rare move can be followed by another rare move.