First-hand data, observed automatically every morning
| Month | Days | Open days (○) | Avg waves | Typical |
|---|---|---|---|---|
| Jan | — | — | — | Strong north-east monsoon; many northerly days |
| Feb | — | — | — | Tail end of the winter monsoon |
| Mar | — | — | — | Seas gradually settle |
| Apr | — | — | — | Stable spring conditions |
| May | — | — | — | Rainy season begins |
| Jun | — | — | — | Late rainy season; changeable seas |
| Jul | 25 | 76% | 0.8 m | Typhoon season begins; excellent when no typhoon is around |
| Aug | 31 | 52% | 1.4 m | Midsummer; highest open rate outside typhoons |
| Sep | 30 | 43% | 1.0 m | Peak typhoon month; watch the forecast |
| Oct | 2 | 50% | 0.7 m | End of typhoon season |
| Nov | — | — | — | North-east monsoon starts; northerlies pick up |
| Dec | — | — | — | Winter monsoon; more closed days |
Source: this site's automatic 06:00 JST observation of sea conditions at Cape Maeda. Not official data.