Is Silver Week (Late September) Good for Diving? Data Verification
2026-03-16
Silver Week (late September) is a precious long weekend for divers who missed Obon. But 'isn't it typhoon season?' is a common worry. Our data shows September visibility improves over August (Obon) at every site we track. Even accounting for typhoon risk, Silver Week is definitely a viable diving holiday.
27.3m
Yonaguni (Sep)
19.8m
Kerama (Sep)
12.7m
IOP (Sep)
+1.3〜2.5m
vs Obon improvement
September Visibility by Site
| Site | Sep Vis | Aug Vis | Change | Sep Obs |
|---|---|---|---|---|
| Yonaguni | 27.3m | 24.8m | +2.5m | 400 |
| Hachijojima | 21.9m | 17.3m | +4.6m | 29 |
| Kerama | 19.8m | 18.5m | +1.3m | 160 |
| Ishigaki | 18.5m | 17.2m | +1.3m | 130 |
| Yakushima | 22m | 20.5m | +1.5m | 15 |
| Mikomoto | 13.2m | 11.8m | +1.4m | 270 |
| IOP | 12.7m | 10.5m | +2.2m | 270 |
| Kushimoto | 11.5m | 10.2m | +1.3m | 320 |
| Futo | 11.2m | 9.8m | +1.4m | 290 |
| Echizen | 9.5m | 8.2m | +1.3m | 390 |
Visibility improves Aug → Sep at all sites. Summer turbidity gradually clears.
Obon vs Silver Week: Visibility Comparison
| Site | Obon (Aug) | SW (Sep) | Improvement |
|---|---|---|---|
| IOP | 10.5m | 12.7m | +2.2m |
| Kerama | 18.5m | 19.8m | +1.3m |
| Yonaguni | 24.8m | 27.3m | +2.5m |
| Kushimoto | 10.2m | 11.5m | +1.3m |
| Mikomoto | 11.8m | 13.2m | +1.4m |
Conclusion: Silver Week beats Obon for visibility
SW beats Obon at all 5 sites, notably Yonaguni (+2.5m) and IOP (+2.2m). Less crowded than Obon too — better value overall.
Typhoon Risk and Visibility Recovery
Typhoon Risk
September is late typhoon season. JMA data shows an average of 3.3 typhoons approach Japan in September (1991–2020). The risk of SW dates overlapping with a typhoon is real. Travel insurance is recommended.
Post-Typhoon Clarity
2-3 days after a typhoon passes, strong water mixing can dramatically improve visibility beyond normal levels. Izu Peninsula has recorded 20m+ visibility post-typhoon. If SW falls right after a typhoon, you might actually get lucky.
Plan B for Typhoons
Okinawa tends to get hit earlier and often recovers by SW. Honshu may get delayed impact. Best plan: keep your destination flexible based on typhoon forecasts.
Reference: JMA 'Typhoon Statistics' (https://www.data.jma.go.jp/yoho/typhoon/statistics.html)
Recommended Sites for Silver Week
For guaranteed clarity
Yonaguni (27.3m), Kerama (19.8m). Okinawa stays comfortable at ~28°C in September. Quick typhoon recovery.
For best value
Izu Peninsula (IOP 12.7m, Futo 11.2m). Day-trip from Tokyo saves on travel. Water temp ~24°C, wetsuit is fine.
For big marine life
Mikomoto (13.2m). September is peak hammerhead shark season. Moderate visibility but high encounter rate with pelagic species.
For a hidden gem
Hachijojima (21.9m). September is its annual peak with 25.8°C water. Just 55 min by ANA from Tokyo. Visibility rivals Kerama.
About the Data
September visibility is the full-period September average. Obon (August) uses the overall August average as proxy. Data includes typhoon-impacted days (shop closure days have no data). Typhoon statistics from JMA (1991–2020 avg).
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