Choshi seasonal overview
Best Surf Season (November - February)
The winter half of the year is when Choshi truly comes alive. As the Siberian High strengthens over Asia, the pressure gradient across Japan tightens and the northwest-to-north airflow that follows is pure offshore for the south-facing beach. Average swell heights sit in the 5-6ft (1.5-1.8m) range and average periods climb to 9.5-9.9s, giving the waves a powerful, lining-up feel. Locally generated NE/E windswell is plentiful, but the real gems are the less frequent SE/S groundswells from passing North Pacific lows, especially when they arrive at 10s+. The ideal-wind window peaks between 39% and 47% from November through February, making this the most consistent window for clean, rippable surf.
Fair Surf Season (March - April and September - October)
The shoulder seasons bring a mix of conditions. March and April still see solid average heights around 5-6ft (1.6-1.8m), but the offshore wind frequency drops to 26-32% as the winter monsoon breaks down, and the swell period eases to 9.2-9.6s. On the flip side, September and October mark the peak of the Western Pacific typhoon season, and passing tropical systems can inject long-period SE/S swell into the beach. The catch is that the warm, humid flow around these systems also brings more onshore S/SSW winds, so a lot of the energy stays mushy. When the wind does swing offshore, these months can deliver excellent waves.
Low Surf Season (May - August)
From May through August, Choshi settles into its lowest-quality surf window. The average swell height drops to 4-5ft (1.2-1.4m) and periods fall to 8.6-9.5s, dominated by short-period ESE/E/SE windswell. This is also the season when the Pacific High builds in, feeding persistent S/SSW winds straight onshore into the south-facing beach. Ideal-wind days bottom out around 25-28%, keeping the lineup frequently bumpy and disorganized. The one silver lining is the warm water and occasional late-summer typhoon pulses, but without a strong offshore wind, Choshi's summer surf is mostly fat and grovelly.