Koper Weather in September
Thinking of visiting Koper in September? Expect high temperatures reaching 24°C (75°F) during the day, dropping to 16°C (61°F) at night, and note that quite a bit of rainfall is likely.
Rainfall in Koper in September
Typically around 11 days of rainfall are expected, averaging 159 mm (6.3 in) for the month. The rain this month tends to fall in heavier spells rather than light drizzle. When it rains, showers can be significant.
Temperature in Koper in September
September in Koper sees highs of 24°C (75°F) and lows of 16°C (61°F) overnight. This gives the month a fairly typical daily rhythm, with warmer afternoons and more comfortable nights. At 16°C (61°F) overnight, it can feel quite a bit cooler after dark. Worth packing something warmer for evenings, but the cooler temperatures are ideal for sleeping.
Sunshine in Koper in September
The city usually sees around 223 hours of sunlight, indicating many sunny days — a great month for sightseeing.If you prefer enjoying temperate temperatures and rain-free days, June, July and August typically offer the best circumstances. If you're seeking pleasant, dry and sunny weather somewhere else in the world, our weather planner can help you explore other options.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit Slovenia, check out our Koper's climate page.
Koper Temperature in September
Min Temperature
16°C (61°F)
Max Temperature
24°C (75°F)
Chance of Rain
37%
Precipitation
159 mm (6.3 in)
Rainy days
11 days
Humidity
57% *
Sunshine
223 hours *
Percentage Sunshine
*
Daily Historical Temperatures
50-year average (1976-2025)
Based on our historical records, temperatures in Koper typically drop from around 26°C (79°F) at the start of September to approximately 22°C (72°F) by the end. Nights are pleasant, with lows typically ranging from 13°C (55°F) to 16°C (61°F).
Average temperatures in September
Daily Historical Precipitation
50-year average (1976-2025)
Average daily rainfall for each day of the month based on long-term records.
Average precipitation in September
Historical weather for Koper in September
Browse day-by-day weather records for Koper spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.
Koper historical weather extremes in September
Based on 49 years of weather observations (1976-2025), these are the most extreme conditions recorded in Koper.
- The warmest day in September was on September 23, 1985, with a maximum of 35°C (95°F).
- On September 18, 1977, Koper saw its coldest September day with temperatures maxing out at 11°C (52°F).
- The lowest overnight temperature recorded in September was 4°C (39°F) (September 29, 1977).
Best Places in Slovenia in September
Find out more about the weather in Slovenia and which places have the best travel conditions in this month. See all of Slovenia in September →
perfect weather
pleasant
tolerable
unpleasant
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What to Wear in Koper in September
Comfortable temperatures call for an easy wardrobe in September. Pack summer basics like t-shirts and shorts, but include a light jacket for cooler moments. A pair of comfortable walking shoes is essential. It's going to pour! Pack a good poncho and prepare for very wet conditions. You'll definitely want to pack sunglasses and sunscreen. There will be plenty of bright sunshine this month.What To Do in Koper in September
We rated the following activities from 1 (least suitable) to 10 (best) to do.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit Slovenia, check out our Koper's climate page.
Temperature Rainfall Sunshine Humidity
See the full Koper climate overview or explore weather in Slovenia.
