Shonan - surf spot statistics

Best Surf Season (October, November, December, March, September)

The surf clock ticks loudest during the transition months, when the North Pacific stirs with early season cold fronts and departing typhoons. From October through December, and again in March and September, Shonan sees its highest probability of clean, rideable waves. This is when the Aleutian Low and Siberian High begin to flex, sending pulses of north to northeast wind that groom the swell. The dominant swell directions shift from the south-southwest to southwest, offering punchy, waist-to-head-high sets on the better days. Offshore flow (N, NNE, NW) becomes more frequent, often keeping the surface glassy. While average swell heights hover around 0.7-0.8m, the combination of decent period (8-9s) and favourable wind makes these months the prime window for consistent surf.

Fair Surf Season (January, February, April, May, June)

These months see a mixed bag. January and February still carry winter swell, but the percentage of ideal wind drops slightly, and the southwest swell trains become more dominant, often accompanied by stronger onshore flow from the same direction. April through June marks the transition from winter to summer patterns. The wind regime becomes more variable: occasional northerly clears the lineup, but southerly winds increase as the summer monsoon builds. Swell heights hold steady around 0.7-0.8m with periods averaging 7.8-8.0s, providing fun, rippable waves when the wind plays ball. Expect more days of groveling conditions, but still plenty of sessions to be had with a keen eye on the forecast.

Low Surf Season (July, August)

The heart of summer brings the least consistent surf. The dominant high pressure over the Pacific sets up a persistent southerly flow, with wind from the S and SSW blowing onshore over 85% of the time. Swell energy from the south quadrant is plentiful, but the accompanying chop and crumble make quality waves rare. The average wave period climbs to 8.3-9.3s, hinting at longer-period groundswell from distant typhoons, yet the onshore wind often wrecks the surface. When a strong typhoon passes at the right angle and a northerly breeze kicks in, Shonan can suddenly light up, but those windows are fleeting. Most days are small (0.7-0.8m) and messy, best left for longboards or a beach day.

September: Sweet Spot

September is a prime month for Shonan. The average swell height is 0.8m with a solid 9.0s period. Swell is spread among SSE (20.3%), S (21.0%), SE (17.0%), and SSW (12.7%), offering a variety of angles. The wind improves to 18% ideal, with NNE (25.0%) and N (9.8%) providing regular offshore flow. This combination produces clean, fun-sized waves on a frequent basis. The transition from summer to autumn means fewer strong typhoons but more consistent mid-latitude lows, blending long-period groundswell with cooler air. September often delivers waist-to-chest-high waves with good shape, making it a favourite month for local surfers. The water is still warm, and the crowds are manageable. Highly recommended.