Kushimoto Water Temp & Visibility — Monthly Data Guide

Kushimoto, located at the southernmost tip of Honshu in Wakayama Prefecture, is one of Japan's premier diving destinations. The Kuroshio Current flows directly past this cape, bringing subtropical corals and pelagic fish to waters that would otherwise be temperate. It is a unique place where you can observe tropical marine life without leaving Japan's main island.

Our database contains 3,168 days of water temperature and visibility records for Kushimoto. This article analyzes how water temperature changes throughout the year and identifies the best season for diving.

Monthly Temperature & Visibility

Kushimoto Temperature Calendar

Winter: Jan-Mar (16.5-17.8°C)

Kushimoto's winters are mild compared to other Honshu dive sites. Even in February, the coldest month, average temperature is 16.5°C — slightly warmer than Izu's 15-16°C during the same period. This is thanks to the Kuroshio warm current flowing year-round past Kushimoto's coast. A drysuit or thick 6.5mm wetsuit is recommended, though drysuits are the safer choice. Winter often brings excellent visibility, with 20m+ days not uncommon.

Spring: Apr-May (17.9-19.7°C)

April remains cool at 17.9°C, but May sees temperatures climb to 19.7°C. Spring plankton blooms can temporarily reduce visibility in March-April, but conditions typically recover by late May. This is the transition period from drysuit to wetsuit — those who feel the cold may prefer to stick with drysuits a bit longer.

Summer: Jun-Aug (22.0-26.3°C)

Once temperatures cross 22.0°C in June, the comfortable season begins in earnest. August averages 26.3°C, making a 5mm wetsuit more than sufficient — many divers opt for 3mm on warmer days. Summer brings the Kuroshio mainstream closer to shore, attracting schools of pelagic fish and occasionally manta rays or whale sharks. Be aware that when the Kuroshio shifts offshore, temporary temperature drops can occur.

Best Season: Sep-Nov (22.7-26.3°C)

September through November is Kushimoto's prime diving season. September matches August's peak at 26.3°C, October holds at a warm 25.2°C, and even November is a comfortable 22.7°C in a 5mm wetsuit. Beyond warm water, this period offers the most consistently high visibility of the year. While typhoon season overlaps, post-typhoon conditions often bring spectacular visibility exceeding 30m for those with good timing.

Early Winter: December (19.6°C)

December drops to 19.6°C, comparable to Izu at the same time. Wetsuits still work in early December, but drysuits become the safer choice later in the month. Visibility trends upward as winter approaches, rewarding cold-tolerant divers with clearer water.

Kushimoto Suit Guide