August holds Croatia’s warmest sea: 23.6°C at Split, 23.5°C at Hvar and 23.3°C at Dubrovnik. The air is slightly cooler than July’s and rainfall at Split nearly doubles, from 25.5 mm to 44.8 mm. The peak ferry timetable ends on 30 August.
The sea peaks a month after the air
Every land measurement at Split falls back in August: mean air from 25.7°C to 25.4°C, days above 30°C from 16.5 to 15.7, sunshine from 11.2 hours a day to 10.3. Only the water goes up. It takes the sea a month of accumulated summer to reach its own maximum, and August is where it lands.
| Station | Warmest air month | Warmest sea month | July sea °C | August sea °C |
|---|---|---|---|---|
| Split (Marjan) | July | August | 23.2 | 23.6 |
| Hvar town | July | August | 22.9 | 23.5 |
| Dubrovnik | August | August | 22.9 | 23.3 |
Dubrovnik is the clean case: its warmest air month is August (24.8°C against July’s 24.6°C) and its warmest sea month is August too. Split and Hvar peak on land in July and in the water in August. Whichever way round, the water never peaks first. That single ordering is what makes September a serious swimming month and May a poor one.
23.6°C
Sea at Split in August, the warmest monthly figure in the 1971–2000 normals.
The month it rains again
August rainfall at Split is 44.8 mm across 3.8 rain days, against July’s 25.5 mm across 3.3. At Dubrovnik the jump is sharper: 28.3 mm to 72.5 mm. The rain days barely move, so this is not drizzle spread through the month — it is the same small number of days carrying considerably more water. August rain in Dalmatia is a thunderstorm, not a grey afternoon.
Monthly rainfall at Split, mm. July is the driest month at 25.5 mm; August is already at 44.8 mm. Source: DHMZ (meteo.hr), climate normals 1971–2000.
The boats thin out before the crowds do
Line 634 between Korčula and Orebić runs 22 sailings a day only to 30 August; from 31 August it is back to 20. Line 9807’s full route from Ubli through Korčula and Polače to Dubrovnik ends on the same date — it runs from 3 July to 30 August and not a day longer. Line 602 to Vis is the exception, holding three sailings a day to 20 September.
Assuming late August is the same trip as early August
The last day of August is already on the shoulder timetable while still carrying the season tariff, which does not revert until 27 September. A southern island chain booked for 29 August to 5 September loses the Korčula and Polače calls on line 9807 halfway through and pays high-season fares for the whole of it.
If the itinerary depends on a specific catamaran leg rather than a mainland-to-island hop, check the line’s own season dates rather than the month. The route network has four different season boundaries on it and none of them is 1 September.
What to do about August
If August is fixed, buy the thing August is uniquely good at, which is the water, and stop trying to do anything else. Base on an island or a beach town rather than in a city with a cruise berth. Hvar at 23.5°C sea and 14.0 days above 30°C is a better August proposition than Split at 15.7. Leave the walls, the parks and the hills for a month when they are not 30°C.
What to decide before you book
- Swimming is the priority. August is the correct month. Nothing else in the year beats 23.6°C.
- Heat is a problem. Dubrovnik takes 9.8 days above 30°C; Split takes 15.7. Go south or offshore.
- You need a specific catamaran leg. Check its own dates: line 9807’s full route ends on 30 August.
- You want the peak timetable. It runs 3 July to 30 August on line 634, not the whole month.
Find August flights and hotels
What do you need to work out next?
August is the water month. Base yourself accordingly.
Where to stay
Island or mainland in August?
Hvar takes 14.0 days above 30°C in August; Split takes 15.7.
Getting around
Where is the swimming actually best?
The sea holds 23.5°C at Hvar and 23.3°C at Dubrovnik all month.
When to go
Is September a real alternative?
September’s sea is 21.7°C at Split, warmer than June’s 21.1°C.
Planning
What ends on 30 August?
Line 9807’s full route to Korčula and Polače, and line 634’s 22 sailings a day.
Climate data: DHMZ (meteo.hr), climate normals 1971–2000. Ferry data: Agencija za obalni linijski pomorski promet (ZOLPP), 2026 state coastal line register and per-line timetables.