December is the annual maximum. Depressions form off Newfoundland, cross the whole Atlantic with nothing in the way, and arrive in the Bay of Biscay at full size: La Nord and La Gravière reach their yearly peak, and swells over two and a half metres run through December and January as a matter of course.
That size is not for the whole coast. The Landes is sand, and sand stops holding a wave's shape above a certain height, so most December days the choice is between one break working at its limit and a beach that has turned into a washing machine. Telling them apart from the car park is the skill this month asks for.
The day gives you about nine hours, the water is at 14°C, and the wind decides the rest. A December week with two good sessions in it is a good December week.
