Sea temperature in Slovenia
Live water temperatures and swimming conditions across 2 beaches on the Slovenia coast.
Best time to swim in Slovenia
The sea in Slovenia peaks in August, when the water averages around 26°C.
The main swimming season runs from June – October, when surface temperatures stay comfortable for extended sessions.
On average, 5 months a year sit above 20°C — the threshold most swimmers describe as pleasant without a wetsuit.
Shoulder months like May and November are noticeably cooler but often quieter, with fewer crowds and steadier weather.
Outside peak season the water drops toward 15°C, so a 3/2mm shorty or full wetsuit makes long swims much more comfortable.
The coldest month is typically February at around 12°C, when cold-water swimmers dominate the coast.
Slovenia sea temperature history
Long-term climatology for Slovenia shows an annual mean sea temperature of 18°C, ranging from 12°C in winter to 26°C at the summer peak.
The seasonal swing is roughly 14°C between the coldest and warmest month — a useful yardstick when comparing years or checking whether the current sea is running above or below average.
Recent decades have trended slightly warmer at Slovenia, in line with regional sea-surface temperature records for the wider basin.
Monthly averages below are drawn from multi-decadal climatology and are updated as new observations arrive.
Values are area averages; individual beaches vary by exposure and depth.
Slovenia sea temperature: frequently asked questions
What is the warmest month to swim in Slovenia?
August is the warmest month in Slovenia, when the sea averages about 26°C. Late-season warmth often persists a few weeks after peak.
When is the sea coldest in Slovenia?
The coldest month in Slovenia is typically February, when the water averages around 12°C. Cold-water swimmers and surfers dominate this period.
When can you swim in Slovenia without a wetsuit?
The main swimming season in Slovenia runs from June – October — about 5 months a year when the sea sits above 20°C, the level most swimmers describe as pleasant without a wetsuit.
Do I need a wetsuit in Slovenia?
Outside peak summer the water in Slovenia drops toward 15°C, so a 3/2mm shorty or full wetsuit makes long swims much more comfortable. In peak months most swimmers go without.
What is the average sea temperature in Slovenia?
The long-term annual mean sea temperature in Slovenia is about 18°C, based on multi-decadal climatology of the surrounding waters.
How do I check the current sea temperature in Slovenia?
The live reading at the top of this page shows the current sea temperature in Slovenia, updated hourly from marine buoy and satellite data. The 7-day forecast covers water, air, waves, wind and UV for the week ahead.
Slovenia sea temperature by month
Average sea temperatures around Slovenia for every month of the year, based on long-term Open-Meteo marine climatology.
| Month | Average sea | Swimming comfort |
|---|---|---|
| January | 13.0°C | Too cold for most |
| February | 12.0°C | Too cold for most |
| March | 13.0°C | Too cold for most |
| April | 15.0°C | Bracing — wetsuit advised |
| May | 19.0°C | Swimmable, refreshing |
| June | 23.0°C | Pleasant swimming |
| July | 25.0°C | Warm swimming |
| August ⭐ | 26.0°C | Warm swimming |
| September | 23.0°C | Pleasant swimming |
| October | 20.0°C | Swimmable, refreshing |
| November | 17.0°C | Bracing — wetsuit advised |
| December | 14.0°C | Bracing — wetsuit advised |
Monthly figures are modelled climatology averages, not live readings. How accurate is our data?
Warmest beaches in Slovenia right now
Sea temperature in Slovenia — FAQ
How warm is the sea in Slovenia in September?
The sea off Slovenia averages about 23.0°C in September, based on long-term monthly averages for this coast.
When is the best time to swim in Slovenia?
Slovenia is warmest in August (around 26.0°C) and coldest in February (around 12.0°C). There are typically 4 months a year when the water sits above 22°C.
What is the average yearly sea temperature in Slovenia?
Across all twelve months, the sea in Slovenia averages about 18.3°C.
Do you need a wetsuit to swim in Slovenia?
In peak season (around August, ~26.0°C) most swimmers are comfortable without a wetsuit. Outside summer, when the water drops toward 12.0°C, a 3/2mm to 5/4mm wetsuit is recommended.