Japan Dive Site Water Temperature Calendar — Monthly & Regional Guide

The first step in dive planning is knowing the water temperature at your destination. We've organized 46,000+ water temperature records from 30+ dive sites by month and region. Use this calendar for suit selection and trip timing.

National Temperature Heatmap

Monthly average water temperatures across all sites. Red indicates warm water, blue indicates cold.

Regional Temperature Profiles

Okinawa & Southwest Islands

Japan's warmest diving region at 21-28°C year-round. Comfortable wetsuit diving even in winter. The nearby Kuroshio Current provides exceptional temperature stability.

Izu Peninsula

Japan's most popular diving area, accessible as a day trip from Tokyo. Annual variation is about 10°C (15-25°C). Wetsuit season runs June-October; drysuits November-May. Site-specific differences of 1-3°C exist between sheltered bays and open ocean.

Kii Peninsula

Warmed by the Kuroshio, relatively mild even in winter. Kushimoto, at the southern tip of Honshu, maintains 16°C+ even in the coldest months. The warm waters support abundant coral communities, as documented by Japan's Ministry of Environment.

Shikoku

Kashiwajima receives a direct branch of the Kuroshio, creating a unique mix of temperate and subtropical marine life. Kannoura is one of the closest mainland points to the Kuroshio.

Sea of Japan

The widest annual temperature range. Echizen drops to 11°C in winter but exceeds 27°C in summer. The Tsushima Current brings surprisingly warm water in summer with excellent visibility. Diving season runs April-October.

Others (Izu Islands & Boso)

Hachijojima and Miyakejima receive direct Kuroshio influence and tend to be slightly warmer than the Izu Peninsula. Ito (Boso) sits at the confluence of the Oyashio and Kuroshio, creating unique temperature patterns.

How to Use This Calendar

1. Check the heatmap for your target month
2. Determine suit thickness needed (see our thickness guide)
3. Check our temperature forecast for the 7-day prediction before your trip