Shonan - surf spot statistics

Shonan, Japan, offers varying surf conditions throughout the year, with the best windows for consistent waves and favorable winds typically occurring in late summer and autumn. The swell data shows that ground swells, which provide cleaner and more powerful waves, are most frequent from August to October, peaking in August at 16%. Wind swells dominate the rest of the year, particularly from March to May and again in October, with percentages above 60%. However, wind conditions are generally poor across all months, with good wind days rarely exceeding 15% (best in October and November). The mean swell size remains modest, averaging 0.6m to 0.8m, with slightly larger waves in March, September, and October. For surfers seeking the most reliable conditions, September and October stand out as the prime months. These months combine a higher percentage of ground swells (15% and 14%, respectively) with slightly improved wind chances (13% and 15% good wind days) and a mean swell size of 0.8m. Late summer (August) also sees a spike in ground swells, though wind quality remains poor. Winter months (December-February) and early spring (March-May) offer more wind swells but suffer from consistently bad onshore winds. Summer (June-July) tends to be the least favorable, with smaller swells and persistent poor winds. Overall, autumn provides the best balance of swell energy and marginally better wind opportunities for surfers willing to wait for clean sessions.

August in Shonan offers small to occasionally mid-range surf with an average swell height of 0.7m and a decent period of 8.9s, suggesting generally clean but weak waves. The swell is predominantly from the ESE to SSE (45% of waves under 1.5m, with 1.5-2m+ waves appearing 2-3% of the time), which aligns moderately well with the coastline. However, the most common wind directions (SSW, SW, and S) are often onshore or cross-shore, with only 9% ideal conditions—typically light easterlies or variable winds under 10kph. Expect smaller, softer waves early in the morning with potential for slightly better shape if winds cooperate, but afternoon sessions often suffer from choppier conditions due to prevailing SSW/SW winds (15-30kph in 15-25% of cases). Overall, August is inconsistent for quality surf, favoring smaller boards and patience for rare clean windows.