When to Dive Okinawa, Ishigaki & Yonaguni: Month-by-Month Guide from Real Data

2026-03-11

"Okinawa always has great visibility" — half true, half misleading. Based on 7,800+ real observations, we break down the true best seasons for Yonaguni, Ishigaki, Kerama, and Amami Oshima. Best months differ by site, and the right timing depends on your priorities: maximum clarity, warmest water, or big animal encounters.

Key Takeaways

Yonaguni peaks in September (27.3m). Kerama peaks in July (21.3m) and is the most stable site (only 2.3m annual range)
Amami Oshima peaks in December (24.6m) — a unique pattern different from both Honshu and Okinawa
Rainy season (June) barely affects visibility: Yonaguni stays at 24.4m, Kerama at 19.7m

Best Time by Diving Goal

Best Visibilityup to 26.5m

Jul–Sep — Yonaguni (27.3m in Sep)

Yonaguni's peak clarity. Summer water temps hit 28–29°C. Typhoon season (especially September) carries cancellation risk.

Comfort Firstup to 22m

May–Jun — Kerama & Yonaguni (24–26°C)

Rainy season but visibility barely drops (Yonaguni 24m+). No typhoons, easier to plan. Comfortable water temps.

Best Value & Stabilityup to 21m

Mar–May — Ishigaki (21–22m + high manta probability)

Peak manta season. Visibility 21–22m. Water temp slightly cool for Okinawa (21–22°C at Ishigaki).

New Year / Winterup to 22.5m

Dec–Feb — Yonaguni & Amami (22–25m)

Even in winter, visibility stays 22–25m. Amami December: 24.6m (site's annual peak). Water temps: cool (Ishigaki 21°C, Yonaguni 24°C).

Month-by-Month Visibility Data (All Sites)

Month	Yonaguni		Ishigaki		Kerama		Amami
	Vis	Temp	Vis	Temp	Vis	Temp	Vis	Temp
Jan	22.4m	24°C	20.9m	—	18.1m	21.7°C	22.7m	20.2°C
Feb	22.6m	23.8°C	—	—	18.1m	21.2°C	20.8m	19.3°C
Mar	23.5m	24.2°C	21.9m	—	19m	21.7°C	16.7m	19.5°C
Apr	23.9m	25°C	21.2m	20.8°C	18.6m	22.3°C	15.9m	20.9°C
May	24.2m	26.3°C	20.1m	26°C	19.4m	23.8°C	16.9m	22.4°C
Jun	24.4m	27.6°C	20.1m	—	19.7m	25.6°C	17.8m	24.6°C
Jul	25.6m	28.6°C	20.9m	27°C	21.3m	27.6°C	17.3m	28.1°C
Aug	26.5m	28.7°C	21m	26°C	20.9m	27.9°C	19.7m	29°C
Sep	27.3m	28.6°C	21.4m	—	19.8m	28.1°C	18.6m	28.1°C
Oct	26.8m	27.8°C	19.4m	26.5°C	19.2m	27.4°C	19m	27.1°C
Nov	24.4m	26.4°C	19.1m	26°C	19m	25.5°C	19.5m	25°C
Dec	23.4m	25.2°C	19.4m	—	18.5m	23.2°C	24.6m	22.5°C

Ishigaki: some months have no data (—). Obs counts: Yonaguni 4,826 · Ishigaki 1,473 · Kerama 1,533 · Amami 861

Site Profiles

Yonaguni

4,826 observations | Best month: Sep

Avg 24.5m

Peak 27.3m

Highlights

Highest annual avg visibility (24.5m)
Hammerhead sharks (Jan–Mar)
Underwater monument site
High day-to-day variability

Wetsuit Guide

3–5mm (winter) / 3mm (summer)

Visibility Range

Min 22.4m — Max 27.3m

Ishigaki

1,473 observations | Best month: Mar

Avg 20.5m

Peak 21.9m

Highlights

Manta Scramble site (Oct–May)
Japan's most diverse coral reefs
Sekisei Lagoon (largest coral reef in Japan)
Very stable year-round (±2m)

Wetsuit Guide

5mm (winter) / 3mm (summer)

Visibility Range

Min 19.1m — Max 21.9m

Kerama Islands

1,533 observations | Best month: Jul

Avg 19.4m

Peak 21.3m

Highlights

Famous 'Kerama Blue' clarity
Humpback whales (Feb–Mar)
45 min ferry from Naha
Most stable year-round (2.3m range)

Wetsuit Guide

5mm (winter) / 3mm (summer)

Visibility Range

Min 18.1m — Max 21.3m

Amami Oshima

861 observations | Best month: Dec

Avg 19.1m

Peak 24.6m

Highlights

December is annual peak (24.6m)
UNESCO World Natural Heritage waters
Unusually high winter clarity
Spring bloom (Mar–May) reduces clarity

Wetsuit Guide

5mm (winter) / 3mm (summer)

Visibility Range

Min 15.9m — Max 24.6m

Testing Common Okinawa Diving Myths with Data

"June rainy season makes visibility poor" → Data disagrees

Yonaguni June: 24.4m (among the year's best). Kerama June: 19.7m (higher than May). No correlation between rainy season and reduced clarity in Okinawa.

"August is the clearest month" → Yonaguni peaks in September

Yonaguni peaks in September (27.3m), above August (26.5m). However, typhoon risk is also highest then.

"Yonaguni is the clearest in Okinawa" → True year-round

Yonaguni's worst month (Jan: 22.4m) beats Ishigaki's best month (Mar: 21.9m). But day-to-day variability is high (R²=0.046) — always check day-of conditions.

"Winter reduces visibility" → Does not apply to Okinawa

Yonaguni winter (Dec–Feb) stays stable at 22–24m. Amami Oshima's December (24.6m) is its annual peak. Opposite pattern from Honshu Pacific sites.

About the Data

Compiled from 2015–2026 dive shop daily logs. Yonaguni: 4,826 obs; Ishigaki: 1,473 obs (some months missing); Kerama: 1,533 obs; Amami: 861 obs. Visibility values are averages of real measurements (midpoint of reported min/max). Water temps are averages where recorded.

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