Best Time to Dive Japan
Across 50 Japan dive sites with multi-year conditions history, August historically shows the most favorable days — 72% of sampled days in the good band. The next-highest months are September (69%), June (63%) and May (56%). December historically shows the fewest favorable days (22% of sampled days). Average water temperature in the sample runs from about 20°C in February to 29°C in August. Typical seas range from 1.2 m to 1.9 m of significant wave height through the year. These figures are historical climatology computed from measured conditions — patterns, not a forecast or a guarantee.
Computed from our own conditions climatology — measured history, not brochure copy.
Which months are historically most favorable in Japan?
| Month | Historically favorable days | Water temp | Typical seas |
|---|---|---|---|
| Jan | 29% | 21°C | 1.8 m |
| Feb | 28% | 20°C | 1.8 m |
| Mar | 43% | 20°C | 1.6 m |
| Apr | 53% | 22°C | 1.4 m |
| May | 56% | 24°C | 1.4 m |
| Jun | 63% | 26°C | 1.2 m |
| Jul | 51% | 28°C | 1.5 m |
| Aug | 72% | 29°C | 1.4 m |
| Sep | 69% | 29°C | 1.3 m |
| Oct | 46% | 27°C | 1.7 m |
| Nov | 24% | 25°C | 1.8 m |
| Dec | 22% | 23°C | 1.9 m |
% = share of sampled days scoring in the favorable band, median across 50 dive sites with at least two years of history. Ringed = historical peak.
How does this compare worldwide? The Most Reliable Diving Months on Earth ranks 61 countries by the same measure.
Marine life seasons
Sighting patterns across the wider Japan & East Asia region — not site-specific promises.
- Green sea turtleApr–Jun
Bars are Jan–Dec — months when sightings historically concentrate (GBIF occurrence records). Wildlife is never guaranteed.
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