Best time to visit the Basque Country
The short answer: late spring through early autumn. The long answer: it depends on whether you'd rather have warm Atlantic mist or a properly atmospheric storm rolling in over the chapel.
The best time to visit Basque Country for Gaztelugatxe day trips is May to early October. Skies behave, daylight stretches past 9pm, and the cliffs are dressed in unreasonable amounts of green.
Winter? Possible. But storms can close the bridge to the islet, and you'd be cheating yourself out of the long golden evenings the Basque coast is famous for.
Best seasons: April–June and September–October for mild weather, green scenery, and manageable crowds.
Best departure time: Book a morning departure before 9am. The first wave of climbers hits Gaztelugatxe by 11am.
Avoid if possible: July and August weekends are crowded, opt for a weekday or shoulder season.
Special timing: Catch the Basque Coast in late September during the traditional Aste Nagusia festival season.