WHEN TO GO
The Best Time to Visit the Blue Cave
Why the season is short, when the sea behaves, and the months that balance the light, the crowds and the queues.
See Blue Cave day trips on GetYourGuide ↗A short, sea-dependent season
The Blue Cave is effectively a warm-season attraction, roughly April to early November. Outside that, the open crossing to Biševo is too exposed, the cave is closed more often than not, and the swim stops lose their point in a cold sea. Within the season, the deciding factor isn't temperature but the sea: calm water is what lets you into the cave and makes the crossing comfortable, so you're really choosing for calm as much as for sunshine.
Late spring: quiet and calm
May and June are a sweet spot. The sea has warmed enough to swim, the weather is usually settled enough for reliable cave access, and the summer crowds haven't arrived — so the queue at Biševo is short and the islands feel spacious. Mornings on the crossing can still be cool, so bring a layer, but for the balance of good conditions and few people, late spring is hard to beat.
High summer: reliable but busy
July and August give you the warmest, calmest sea and the surest swimming weather — but also the longest Blue Cave queues, as every boat in Dalmatia funnels through the same small entrance, and the busiest stops. If summer is when you travel, book a well-reviewed boat that leaves early, expect company, and take the trade: guaranteed swim weather in exchange for sharing the islands.
Early autumn: the connoisseur's pick
September is many regulars' favourite month: the sea is still summer-warm, the light is still high enough for the cave, and the crowds thin noticeably week by week. Into October the season fades — seas grow less predictable and the cave closes more often — but a calm, clear day in early autumn, with the islands half-empty and the water still warm, is about as good as the five-island trip ever gets.