Forecast scorecard — Japan
We re-score our own weather forecasts against what actually happened next, every day. We don't cherry-pick the flattering numbers: sample sizes, the date the record starts, and days that are still awaiting evaluation are all shown as they are.
Market: US · Korea · Japan · Hong Kong · Crypto
Not enough forecast days have completed 21 trading days yet, so we can't compare. Sample still too small
Whole period
Baseline: across all days regardless of the forecast, the average return 21 trading days later was +2.60% (11 scored days).
| Weather | Forecast days | Avg after 5 days | Avg after 21 days | Share up (21d) | Awaiting | vs baseline |
|---|---|---|---|---|---|---|
| Sunny | 0 | – | – | – | 0 | – |
| Cloudy | 7 | +3.90% | +0.40% | 83% | 1 | -2.21%p |
| Rain | 25 | -0.26% | +5.25% | 100% | 20 | +2.65%p |
| Storm | 0 | – | – | – | 0 | – |
| All | 32 | +0.66% | +2.60% | 91% | 21 | – |
Month by month
| Month | Weather | Forecast days | Avg after 5 days | Avg after 21 days | Share up (21d) | Awaiting |
|---|---|---|---|---|---|---|
| 2026-09 | Cloudy | 1 | – | – | – | 1 |
| 2026-09 | Rain | 5 | -0.91% | – | – | 5 |
| 2026-08 | Cloudy | 5 | +4.75% | +0.09% | 80% | 0 |
| 2026-08 | Rain | 15 | -1.42% | – | – | 15 |
| 2026-07 | Cloudy | 1 | -0.39% | +1.93% | 100% | 0 |
| 2026-07 | Rain | 5 | +3.35% | +5.25% | 100% | 0 |
If you had followed the weather
Following the weather: +2.93% cumulative, max drawdown -4.24% Sample still too small
Just holding: +1.05% cumulative, max drawdown -7.23%
Limits
- The record only starts in July 2026, so the sample is very small. Any cell with fewer than 30 cases could easily be chance.
- Only index returns are measured. Real fills, taxes and FX are not included, and the 'followed the weather' cost is an assumed 0.1% per switch.
- The forecast rules have changed a few times (see the rule change history). Past results do not guarantee future ones.