Boat Tours from Trogir in September and October: Is the Sea Still Warm?

23 August 2026 · 7 min read

The water off Trogir is at its warmest in September, not July. Here is what the shoulder season actually looks like from the deck: sea temperature, crowds, wind, daylight and which tour suits which month.

Short answer: yes. The sea off Trogir is around 24 to 25°C through September and stays swimmable well into October. The water is slower to warm and slower to cool than the air, so September is warmer in the sea than June is, even though June feels hotter on land. What changes after August is not really the temperature. It is everything around it.

How warm is the sea off Trogir in September and October?

The Adriatic here peaks in late August and holds that heat for weeks. Rough figures for the water around Trogir, Čiovo and the Blue Lagoon:

• Early September — 25°C, indistinguishable from August. Nobody gets out early because they are cold.
• Late September — 23 to 24°C. Still a long swim without thinking about it.
• Early October — 21 to 22°C. Warm enough to swim properly, cool enough that you notice the first few seconds.
• Late October — 19 to 20°C. A proper swim for most people, a quick dip for some, and a towel matters now.

For comparison, the sea in June is around 22 to 23°C. So a swim at the Blue Lagoon on the 20th of September is warmer than the same swim on the 10th of June, which surprises almost everyone who plans a Croatian holiday around the calendar rather than the water.

What actually changes in September

The first week of September is the sharpest change of the year on this coast, and it has nothing to do with weather. Italian and Croatian school holidays end, the charter fleet thins out, and the Blue Lagoon goes from a car park of boats to somewhere you can anchor where you like. The same bay that needs patience in August is close to empty by mid-month.

The light changes too. August light at midday is flat and white and difficult to photograph in. September sun sits lower, the water reads more turquoise, and the hour before we turn for home is the best light of the day. If the photographs matter to you, this is the month.

Restaurants ashore are calmer as well. Free time in Maslinica on Šolta in August means queueing for a table. In September you sit down.

What changes in October

October is a genuinely different month, not just a cooler September. The water is still fine. The difference is the wind and the light.

Daylight is the practical one. Sunset moves from about 19:00 at the start of the month to around 18:00 at the end, and clocks go back in the last weekend of October. That is why an afternoon departure in October is a different trip from an afternoon departure in July: you finish in dusk, not sunshine. For most of October the morning departure is the better half of the day.

The other difference is the ride. Twenty degrees of water is warm; twenty degrees of air at speed on an open boat is not. Nobody regrets a windbreaker in October and plenty of people wish they had one.

Will the tour be cancelled? Wind, not cold, ends the season

What stops us sailing is never the temperature. It is the bura, the cold, dry north-easterly that comes down off the mountains and turns the channel to whitecaps in an hour. Bura days are rare in September and become steadily more common through October and November.

A bura day is a cancelled day, and that is not a judgement call we agonise over. We tell you before you board, and you move to another day or take a full refund. The one thing worth doing differently in the shoulder season is leaving yourself a spare day: book the tour for the middle of your stay rather than the morning of your flight home.

Which tour suits which month

• September, any tour. Everything runs, the water is at its best, and the Three Island Tour with lunch on board is the pick if you want a full slow day rather than a dash.
• Early October, half day or Krka. The Blue Lagoon half-day is five hours and gets you back before the light goes. The Krka Waterfalls day trip is arguably better in October than in August: no queue, no heat, and the falls are fuller after the first autumn rain.
• Late October, morning departures. Take the 09:00 rather than the afternoon. Same tour, better light, and you are not cruising home in the dark.
• Any month, the Blue Cave. It is the most weather-dependent trip we run, because the cave itself closes in swell. In the shoulder season, have a second day in reserve.

What to pack differently after summer

Everything from our packing guide still applies. Three things change:

• A windbreaker or a fleece. Not for the swimming, for the cruising. A speedboat at 25 knots makes its own weather.
• A proper towel rather than a sarong. In August you dry in four minutes. In October you do not.
• Sunscreen anyway. The autumn sun off the water still burns, and people forget it because they are not hot.

Is it worth coming in the shoulder season at all?

For a boat holiday, September is the best month of the year on this coast and it is not close. Summer sea, autumn crowds, better light, easier restaurants, and the same islands. October is quieter still and rewards flexibility: build in a spare day, take the morning departure, bring a layer, and you get the Adriatic with nobody on it.

Availability for both months is live on each tour page, so you can see exactly which departures still have space before you plan anything around them.

Frequently asked questions

Related tours

• Blue Lagoon Half Day — from €60
• Three Island Tour — from €55
• Krka Waterfalls — from €75

Related guides

• Sea Urchins and Jellyfish near Trogir: What You Will Actually Meet
• Split to Trogir: Is There a Ferry? (And What to Take Instead)
• Copacabana Beach in Okrug Gornji: Trogir’s Big Beach (2026)

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