Is October the Hidden Sweet Spot? Autumn Visibility × Water Temperature
2026-03-16
October: typhoon season winding down, water still warm at 23–28°C, visibility recovering from summer lows. No GW or summer crowds. The last comfortable wetsuit month. We ranked October's visibility × water temperature sweet spots.
October Visibility × Temperature Ranking
Three Reasons October Shines
1. Water Is Still Warm
IOP Oct: 23.9°C, Kushimoto 25.2°C, Okinawa 27–28°C. 5mm wetsuit is perfectly comfortable. By November, Izu drops to 22°C and drysuit season begins. October is your last comfortable wetsuit month.
2. Visibility Enters Recovery
IOP Oct 13.7m recovers +1.2m from Sep 12.5m. Autumn cooling starts reducing phytoplankton. Koganezaki Oct 15.4m is particularly strong, rebounding from Sep 11.6m.
3. Fewer Crowds
After GW, summer holidays, and Silver Week, October is quiet everywhere. Weekdays can be practically private. For the total package of visibility × temperature × crowds, October may be the year's best.
Warning: Sea of Japan Is Worst in October
Echizen 8.7m, Omijima 7.4m, Tajiri 6.4m — Sea of Japan sites hit their annual low in October. Autumn cooling weakens the Tsushima Current's clearing effect. Avoid the Sea of Japan coast in October.
About the Data
October observations with water temp records, 20+ obs per site (22 sites). Sweet spot score = visibility + water temp.
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