June and September are the best months: warm enough to swim (sea temperature around 18–20°C), the beach not yet overwhelmed, and the town at its most pleasant. July and August are peak season — the town fills with French and Spanish families and prices rise sharply. The weather is reliably fine but the beach gets crowded.
The Fêtes de la Saint-Jean, held in late June, are among the best Basque festivals on the French side of the border: bonfires, dancing, traditional sports, and considerable quantities of txakoli (Basque sparkling wine). The tuna festival in July celebrates the fishing fleet's return from Atlantic grounds.
The off-season (October–April) is quiet but not unpleasant — the town shrinks back to something like its actual self, the sea is grey and dramatic, and the restaurants that stay open are often the better ones.