Go to Bovec in Slovenia
With mountains that linger in the blue sky, an emerald-green river Bovec offers picturesque scenes that are a must see for your bucket list.
Postojna Weather in September
September in Postojna brings pleasant temperatures, with highs of 21°C (70°F) and nights dropping to 11°C (52°F). It's the rainiest month of the year, so come prepared with waterproof gear.
Rainfall in Postojna in September
Postojna is in the rainy season in September, with rain on around 13 days and an average of 181 mm (7.1 in). Rainfall this month is frequent and tends to be fairly heavy when it does fall. Packing waterproofs is a good idea.
Temperature in Postojna in September
If you're visiting Postojna in September, expect highs of 21°C (70°F) and overnight lows around 11°C (52°F). Even when the weather is stable, mornings and evenings can still feel distinctly cool. At 11°C (52°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 Postojna in September
Enjoy a sunny month with about 211 hours of sunshine, even though this month falls in the wet season. There is still enough sun to enjoy the outdoors.If you prefer dry days with pleasant temperatures, May, 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.
Postojna Temperature in September
Min Temperature
11°C (52°F)
Max Temperature
21°C (70°F)
Chance of Rain
43%
Precipitation
181 mm (7.1 in)
Rainy days
13 days
Humidity
67% *
Sunshine
211 hours *
Percentage Sunshine
54% *
* Data from: Triest, Italy (38 KM, 23 Miles).
Postojna Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Postojna - and find the best time to visit.
Daily Historical Temperatures
50-year average (1976-2025)
Based on our historical records, temperatures in Postojna typically drop from around 25°C (77°F) at the start of September to approximately 21°C (70°F) by the end. Nights are cool, with lows typically ranging from 10°C (50°F) to 14°C (57°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 records for Postojna in September
Browse day-by-day weather records for Postojna spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.
Postojna historical weather extremes in September
Based on 50 years of weather observations in Postojna between 1976 and 2026, these are the recorded extremes.
- Postojna recorded its highest September temperature of 34°C (93°F) on September 23, 1985.
- On September 27, 2020, Postojna saw its coldest September day with temperatures maxing out at 10°C (50°F).
- Nighttime temperatures dropped to 0°C (32°F) on September 23, 2022, marking the coldest September night on record.
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
poor
Perfect weather is subjective. On this map perfect weather has been defined with temperatures between 20°C (68°F) and 29°C (84°F) and not too much precipitation (less than 90 mm (3.5 in) a month).
What to Wear in Postojna in September
For Postojna in September, you'll want flexible clothing. It's wise to pack cotton shirts, comfortable shorts, and a pair of jeans for cooler evenings. A light sweater or jacket is useful for air-conditioned spaces (like buses) or unexpected cool moments. Also bring a poncho, it will rain a lot! Waterproof everything you can. Don't forget sun protection, sunglasses, sunscreen, and a hat. These are all good ideas with this much sunshine.
What To Do in Postojna in September
We rated the following activities from 1 (least suitable) to 10 (best) to do.
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Swimming7/10 -
Camping6/10
Postojna 3-Day Forecast
More climate data for Postojna
Temperature Rainfall Sunshine Humidity
See the full Postojna climate overview or explore weather in Slovenia.
Popular in September
Where to go in September - average daytime high across popular destinations.
Piran
24°C (75°F) Portorož24°C (75°F) Maribor
21°C (70°F) Ljubljana21°C (70°F) Bled19°C (66°F) Bovec19°C (66°F) Bohinj19°C (66°F) Kranjska Gora18°C (64°F) Bucket list
Need travel inspiration? Check out our bucket list articles and be inspired.
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