Ishigaki Island Diving Temperatures — Can You Dive in a Wetsuit Year-Round?

Ishigaki Island is one of Japan's southernmost diving destinations, world-renowned for its high manta ray encounter rates. About one hour by plane from Naha — with direct flights from Tokyo — it offers accessible tropical diving.

Our database contains 1,473 water temperature records for Ishigaki. The common question "Can I dive in a wetsuit during winter?" is answered definitively by real data.

Monthly Temperature Trends

Compare Ishigaki with Kerama and Izu Oceanic Park (IOP), mainland Japan's most popular dive site.

The Verdict: Yes, Wetsuits Year-Round

Ishigaki's annual water temperature ranges from 21.3°C (February) to 28.3°C (August). Even in the coldest months of January and February, the water stays above 21°C, meaning a drysuit is never necessary. However, consider the air temperature for surface intervals: a boat coat is wise in winter.

Seasonal Diving Guide

Winter: Jan-Mar (21.3-22.0°C)

Ishigaki's winter water is warm by mainland standards, but spending an hour at 21°C can chill you. A 5mm wetsuit with a hooded vest is recommended. A boat coat for surface intervals is also helpful. Northerly winds can limit site options, but visibility is often at its annual best during winter.

Winter also offers excellent manta ray encounters. Ishigaki's famous "Manta Scramble" point offers year-round sightings, with reliable winter encounters as well.

Spring: Apr-May (23.4-25.1°C)

April reaches 23.4°C and May 25.1°C — comfortable in a 5mm wetsuit, with some divers switching to 3mm by late May. The period around Golden Week (late April) is excellent, with stable weather before the rainy season. May is a hidden gem: good visibility and pleasant temperatures without peak-season crowds.

Summer: Jun-Aug (27.1-28.3°C)

Peak season. Water exceeds 27°C, making 3mm wetsuits or rash guards ideal. After the rainy season, July and August bring stable weather and peak sea surface temperatures. Manta point access is frequent and dynamic terrain dives are at their best. Typhoon awareness is essential.

Autumn: Sep-Nov (24.2-27.5°C)

September averages 27.5°C, October 26.1°C, and November still 24.2°C. After typhoon season passes in September, weather stabilizes with fewer crowds. October-November offers the best value: lower airfares and hotel rates, yet water temperature remains comfortable in a 5mm wetsuit.

Early Winter: December (23.0°C)

At 23.0°C, December is still comfortable in a 5mm wetsuit. An excellent choice for year-end tropical diving holidays.

Comparison with Kerama

The chart shows Ishigaki and Kerama follow nearly identical temperature curves — summer peaks around 28°C and winter lows around 21°C. The choice between them comes down to what you want to see: Ishigaki for manta rays, Kerama for Kerama Blue visibility.

The contrast with IOP is striking. A winter gap of about 5°C (Ishigaki 21°C vs. IOP 16°C) quantifies the comfort advantage of tropical diving in Japan's cold months.

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