Futo Diving Water Temperature — When Can You Dive Without a Drysuit?

Futo is a dive site in Ito City on the Izu Peninsula, right next to the famous Izu Oceanic Park (IOP). Its sheltered cove offers calmer waves than nearby open-ocean sites, making it popular for everything from beginner courses to advanced macro photography.

Our database contains 3,493 days of water temperature data for Futo. The key question "When can I ditch the drysuit?" is answered here with real data.

Monthly Temperature Trends

Compare Futo with neighboring IOP. Even a short distance can reveal meaningful temperature differences.

When Can You Dive Without a Drysuit?

The short answer: June through November. June averages 19.8°C, which is borderline but the point at which most divers switch to wetsuits. November is still 21.0°C, comfortable in a wetsuit. But December drops to 18.1°C, making a drysuit necessary again.

Seasonal Guide

Winter: Dec-Feb (15.1-18.1°C)

Futo's coldest month is February at 15.1°C, among the cooler readings for major Izu dive sites. A drysuit with proper thermal undergarments is essential. The upside: winter visibility is outstanding, frequently reaching 15-20m+. Winter-exclusive creatures like nudibranchs and lumpfish make cold-water diving rewarding for macro enthusiasts.

Spring: Mar-May (15.4-17.7°C)

March at 15.4°C is barely above February. April reaches 16.2°C and May 17.7°C. Drysuits remain the right choice throughout. A phytoplankton bloom in March-April temporarily reduces visibility. Golden Week (late April to early May) still calls for a drysuit.

Early Summer: June (19.8°C)

June averages 19.8°C, the wetsuit transition point. A 5mm wetsuit with a hooded vest provides adequate warmth. If you run cold, consider bringing a drysuit as backup for early June when temperatures can be unstable. Rain is frequent during the rainy season, but clear days between showers offer good conditions.

Summer: Jul-Aug (21.9-24.2°C)

July reaches 21.9°C and August 24.2°C. A 5mm wetsuit is comfortable. When a branch of the Kuroshio Current swings close, temperatures spike and visibility improves dramatically. Weekdays and early-morning entries help avoid summer crowds.

Autumn: Sep-Nov (21.0-24.9°C)

Futo's best season. September peaks at 24.9°C — the annual high — October holds at 23.5°C, and November is still 21.0°C. The optimal balance of warm water and good visibility. Subtropical fish sometimes appear, carried north by the Kuroshio. A 5mm wetsuit is ideal, and dive sites are less crowded than summer.

Early Winter: December (18.1°C)

December drops to 18.1°C, time to switch back to a drysuit. Hardy divers can manage with a 5mm wetsuit and hooded vest, but DAN Japan cautions against hypothermia risk at these temperatures.

Futo vs. IOP

The chart reveals Futo runs 0.5-1°C cooler than IOP year-round. The February gap is about 1°C (Futo 15.1°C vs. IOP 16.0°C). Futo's cove location means it receives slightly less direct influence from offshore warm currents. However, that same cove provides calmer wave conditions, making entries and exits easier — a significant advantage for beginners.

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