September is the payoff. The first autumn lows reach the Bay of Biscay and land on sand that August has just put back into shape, so the coast produces the waves it is known for, in air that still belongs to summer.
The change on the beach is as sharp as the change in the water. French schools go back at the start of the month, the car parks empty over one weekend, and a peak that held forty people in mid-August holds eight.
The size stays civil for most of the month, chest to head high with the occasional bigger day, which is the window somebody improving actually wants: real waves with real shape, before October brings the ones that hurt.
