October keeps warmer water than May: 19.3°C at Split against 17.3°C, and 20.6°C at Hvar. The long Split Marjan record gives the whole month a single day above 25°C, against September’s seventeen. Off-season ferry fares come back on 28 September.
Warm water, no summer
October is the month that breaks the intuition that spring and autumn are equivalent. The sea is still holding August’s heat: 19.3°C at Split, 20.6°C at Hvar, 19.5°C at Dubrovnik. Every one of those is warmer than the same station in May. The land has already gone: one day above 25°C at Split on the 1948–2024 record, against September’s seventeen.
| Station | May sea °C | October sea °C | May days ≥25°C | October days ≥25°C | October rain days |
|---|---|---|---|---|---|
| Split (Marjan) | 17.3 | 19.3 | 9.1 | 1.3 | 7.6 |
| Hvar town | 17.2 | 20.6 | 6.5 | 3.6 | 7.2 |
| Dubrovnik | 17.2 | 19.5 | 4.2 | 1.9 | 8.2 |
Read the last two columns together. October returns only a fraction of May’s warm days and adds a rain day or two, and in exchange the water is two degrees warmer. Whether that is a good trade depends entirely on whether you intend to get in it. For a swimming holiday it clearly is; for a walking holiday May wins on every measure.
October · Split (Marjan)
Step it back to September on the slider and the difference is almost entirely in the warm-day row. The sea gives up 2.4°C at Split; the land gives up everything.
October is when it rains
Autumn rainfall on this coast is serious and unevenly distributed. Rijeka takes 203.9 mm in October across 9.7 rain days — the wettest station-month anywhere in the 1971–2000 set. Dubrovnik takes 120.1 mm, Mali Lošinj 109.1 mm, Split 82.1 mm. A trip to Kvarner in October is a materially different weather proposition from a trip to central Dalmatia in October, and no monthly average for “Croatia” will tell you so.
Choosing an October base by temperature rather than rainfall
Rijeka and Split differ by 2.6°C in mean October air temperature and by 121.8 mm of rainfall. Opatija and the Kvarner coast are lovely in October and wet; central and southern Dalmatia are drier and hold the sea longer.
If the October itinerary includes Plitvice or the Istrian interior, budget for it: Pazin takes 123.5 mm across 8.9 rain days. The parks are at their best after that rain, but the walking days around them are not guaranteed.
The cheapest month with a swimmable sea
The off-season tariff returns on 28 September, which puts the whole of October back on winter prices while the water is still at 19.3°C. A car under 5 m to Vis costs €40.60 instead of €52.00; Korčula to Orebić costs €10.40 instead of €16.20; a foot passenger to Hvar pays €6.40 instead of €10.00. There is no other month in the year that pairs off-season fares with a sea above 19°C.
What you give up is frequency and reach. Line 634 is back to 14 sailings a day. Line 9807 is cut to Sobra, Šipanska Luka and Dubrovnik, so Korčula, Polače and Ubli lose their southern catamaran entirely. A one-island trip works; a chain of them starts to need a car and the coast road.
What to decide before you book
- You want warm water cheaply. October is the only month that pairs a 19.3°C sea with off-season fares.
- You want reliable sun. One warm day in the month at Split, and 82.1 mm of rain. Choose September.
- You are going to Kvarner. Rijeka takes 203.9 mm in October. Weight the trip south.
- You are island hopping. Line 634 is back to 14 a day and line 9807 has lost three ports.
Find October flights and hotels
What do you need to work out next?
October is the cheap end of warm water. Two things decide whether it works.
Where to stay
North or south for an October week?
Rijeka takes 203.9 mm of rain in October; Split takes 82.1 mm.
Getting around
What does the network look like from 28 September?
Line 634 back to 14 sailings a day; line 9807 cut to three ports.
When to go
Is September worth the extra fare?
Seventeen warm days against one, for the same 2.4°C of sea.
Planning
How does the full year line up?
Eight stations, twelve months, and a sea temperature for only three of them.
Climate data: DHMZ (meteo.hr), climate normals 1971–2000. Climate data: DHMZ (meteo.hr), Split Marjan station, 1948–2024. Ferry data: Agencija za obalni linijski pomorski promet (ZOLPP), 2026 state coastal line register and per-line timetables.