Last updated: August 27, 2025
In Koper, Slovenia, September offers a delightful blend of warm days and cool evenings, with maximum temperatures peaking at an inviting 32°C (90°F) and an average of 20°C (68°F). As summer transitions to autumn, the temperature can dip to a brisk 9°C (49°F) during the night. Despite enjoying the warmth, the month is not without its share of rainfall, accumulating 164 mm (6.4 in) over approximately 10 days, bringing a humidity level of 64% that enhances the rich, fragrant atmosphere of this coastal gem. Visitors can expect a vibrant mix of sunny days and refreshing showers, perfect for exploring the stunning surroundings.
As September rolls in, Koper, Slovenia begins to experience a delightful transition into autumn. The temperatures offer a refreshing mix, with minimums around 9°C (49°F) and averages hovering at 20°C (68°F), welcoming cooler breezes after the hot summer months. By day, you might enjoy maximums reaching up to 32°C (90°F), making it ideal for exploring the picturesque coastal town. This month effectively bridges the warmth of summer and the crispness of fall, providing a perfect backdrop for leisurely strolls along the Adriatic Sea or savoring local cuisine in vibrant outdoor cafés. With each passing day, the warmth slowly gives way to the impending cooler months, making September a particularly charming time to visit Koper.
September brings a notable shift in Koper, Slovenia's precipitation patterns, with a substantial increase to 164 mm (6.4 in) over 10 days of rain. This month typically acts as a turning point in the weather, as the warm summer months give way to more consistent rainfall. In contrast to August's modest total of 70 mm (2.7 in), September's downpour signals the onset of the autumn season, laying the groundwork for even wetter months to come. As we move into October and November, the trend continues with increased precipitation, highlighting how September serves not only as a bridge between summer and autumn but also as a prelude to the region's wetter climate.
As summer gives way to autumn in Koper, Slovenia, September brings a noticeable shift in humidity levels. With an average humidity of 64%, the air becomes crisper and more comfortable compared to the sweltering heat of August, which saw a low of 51%. This transition signals the end of the dry summer months, where humidity steadily decreased from 70% in May to its lowest point in July. Although humidity begins to rise again in October, reaching 83%, September offers a pleasant reprieve and sets the stage for the wetter months ahead. The gradual uptick from summer's end hints at the impending arrival of the fall rains, making September a unique blend of lingering warmth and refreshing clarity.
As September arrives in Koper, Slovenia, residents can expect a high UV Index of 7, making sun protection essential. This marks a slight decline from the very high levels witnessed during the peak summer months of July and August, where the UV Index reached 9. However, with a burn time of just 25 minutes, caution is still advised, particularly for those spending extended periods outdoors. This trend illustrates the transition into autumn while still retaining significant sun exposure. Keep informed about UV levels to ensure safety and enjoy the remaining rays of summer. For more details, visit Koper UV Index.
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September in Koper, Slovenia, bathes the city in pleasant warmth, clocking in an impressive 326 hours of sunshine. As summer transitions into autumn, this month taps into the tail end of the bright, sun-drenched days experienced in July and June, which boast the highest hours at 430 and 417, respectively. While September's sunshine diminishes compared to the peak months, it still eclipses the earlier winter months, showcasing a steady trend of increasing light from January’s 182 hours to summer’s zenith. As the days gradually shorten, Koper’s September still offers plenty of golden moments, perfect for exploring the charming coastal views and historical sites before the cooler months set in. It's a delightful reminder of the vibrant energy summer leaves behind as the city gently shifts into fall.
As summer transitions into autumn, September in Koper, Slovenia, offers a delightful 59% chance of sunny weather, making it one of the most promising months for sunshine following the peak of summer. This statistic reflects a slight decline from August's 61%, but maintains a favorable outlook as the sunny days of summer linger. Notably, the likelihood of sun this month surpasses several earlier months, including the cooler months of April and May, indicating that families and travelers can still enjoy warm, sun-drenched days before the onset of fall. As September progresses, Koper's picturesque landscapes are illuminated by this late-summer sun, inviting outdoor enthusiasts to make the most of the season's final warmth.
As summer fades in Koper, Slovenia, September offers a gentle transition, featuring about 12 hours of daylight. This gradual decline in daylight is part of a larger seasonal pattern that sees long summer days with up to 15 hours in June and July, giving way to shorter days as autumn approaches. Following the vibrancy of late summer, where daylight lingers longer, September marks a shift where sunlight begins to wane, yet still provides ample opportunity for outdoor activities and enjoying the beautiful coastal scenery. The month sets the stage for the shorter daylight hours of October and November, reminding us of the cyclical nature of the seasons while still allowing for pleasantly bright early fall days.
In Koper, Slovenia, the September wind offers a gentle shift as summer wanes, with an average wind speed of 2.4 m/s (5 mph). This marks a subtle decline from the slightly breezier months of May and June, where winds reach up to 3.2 m/s (7 mph). As the season transitions, the winds begin to mellow, aligning with the overall trend of decreasing speeds from the summer peak. Notably, this month sets the stage for the more robust gusts of autumn, as seen in the upcoming months of October and November, where winds pick up again, reaching 3.6 m/s (8 mph) and 3.7 m/s (8 mph), respectively. Thus, September serves as a serene precursor, embodying the calm before the autumnal briskness unfolds in picturesque Koper.
Weather in Koper varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Koper, focusing on differences in temperature, rainfall, humidity, and UV levels.
In September, the weather is significantly warmer with average temperatures hovering around 20°C (68°F) and high peaks reaching up to 32°C (90°F). This month also experiences a decent amount of rainfall, totaling 164 mm (6.4 in) over approximately 10 days, while maintaining a moderate humidity level of 64%. In contrast, January brings much cooler conditions, with average temperatures dropping to just 5°C (41°F) and maximums of 13°C (56°F). Precipitation is lower, totaling 56 mm (2.2 in) over about 7 days, but the humidity rises to a notable 88%, giving the winter months a distinctly damp feel. For more specific details on weather patterns, you can check out Koper weather in January.
September and February exhibit stark contrasts in weather conditions. September enjoys warmer temperatures, with averages around 20°C (68°F) and highs reaching up to 32°C (90°F), making it an ideal time for outdoor activities. In contrast, February is much cooler, with average temperatures dipping to 7°C (44°F) and nighttime lows that can plunge to -6°C (22°F). While September experiences a significant amount of precipitation (164 mm or 6.4 in) over about 10 days, February sees less rain, totaling 118 mm (4.6 in) across the same number of days. Additionally, February's higher humidity level of 82% further adds to the chill in the air. For more specifics on the February weather in Koper, check Koper weather in February.
September and March present stark contrasts in weather conditions. In September, temperatures range from a minimum of 9°C (49°F) to a maximum of 32°C (90°F), with an average of 20°C (68°F). This month also experiences notable precipitation of 164 mm (6.4 in) over about 10 days, along with a humidity level of 64%. In contrast, March is cooler, with temperatures ranging from -7°C (20°F) to 21°C (70°F) and an average of 9°C (48°F). Precipitation is significantly lower at 71 mm (2.8 in) over roughly 8 days, and humidity is slightly higher at 73%. For more detailed information on weather specifics, you can check Koper weather in March.
When comparing the weather in September and April, notable differences emerge in temperature and humidity. September generally sees warmer conditions, with minimum temperatures around 9°C (49°F) and average highs reaching up to 32°C (90°F). In contrast, April is much cooler, with minimum temperatures dropping to 1°C (34°F) and average highs only reaching 25°C (77°F). Precipitation is more abundant in September, totaling 164 mm (6.4 in) compared to April's 103 mm (4.0 in), although both months experience rainfall on approximately 10 days. Interestingly, April tends to be more humid at 73%, compared to September's 64%. For more detailed insights into April weather, you can check Koper weather in April.
When comparing the weather in September and May, it becomes evident that September tends to be warmer. With average temperatures ranging from a low of 9°C (49°F) to a high of 32°C (90°F), September offers a more intense warmth, especially on the warmer end, with an average temperature of 20°C (68°F). In contrast, May sees a cooler climate, with temperatures averaging between 7°C (46°F) and 27°C (81°F) and a lower average of 17°C (63°F).
Precipitation levels are somewhat similar, with September receiving 164 mm (6.4 in) over approximately 10 days, while May sees 142 mm (5.6 in) spread across 17 days. Humidity is slightly higher in May at 70%, compared to September's 64%. For a more detailed look at the conditions in May, Koper weather in May provides additional insights.
When comparing the weather in September to that of June, we observe a slight shift in temperatures and precipitation patterns. In September, the minimum temperature drops to 9°C (49°F), with an average of 20°C (68°F) and a maximum of 32°C (90°F), while June features a higher minimum of 11°C (53°F), an average of 22°C (72°F), and a maximum of 33°C (92°F). Additionally, September experiences significantly more rainfall with 164 mm (6.4 in) over 10 days compared to June's 87 mm (3.4 in) over just 8 days. Humidity levels are relatively similar, with September at 64% and June slightly higher at 69%. For more detailed information on June weather, check out Koper weather in June.
In comparing the weather patterns of September and July, September generally presents more variability with a wider temperature range; it experiences a minimum of 9°C (49°F) and a maximum of 32°C (90°F), while averaging around 20°C (68°F). In contrast, July maintains a milder temperature profile, with a minimum of 16°C (61°F) and a maximum of 33°C (91°F), averaging 24°C (75°F). Additionally, September is characterized by higher precipitation levels, with 164 mm (6.4 in) falling over 10 days compared to July's 65 mm (2.6 in) over just 8 days. Despite the slightly higher humidity of 64% in September compared to 63% in July, the latter is typically the drier month. For more details on July's climate, feel free to check Koper weather in July.
In comparing the weather between September and August, September tends to be cooler with a minimum temperature of 9°C (49°F) and an average of 20°C (68°F), while August features a warmer minimum of 15°C (59°F) and an average of 25°C (77°F). The maximum temperatures also reflect this trend, reaching up to 32°C (90°F) in September compared to 34°C (94°F) in August. Additionally, September is notably wetter, experiencing 164 mm (6.4 in) of precipitation over 10 days, in contrast to August's 70 mm (2.7 in) spread across 7 days. Humidity levels are higher in September at 64%, compared to August’s 51%. For more detailed information, you can check Koper weather in August.
September and October showcase a noticeable shift in weather patterns. September sees warmer temperatures, with a minimum of 9°C (49°F) and an average of 20°C (68°F), peaking at a high of 32°C (90°F). In contrast, October cools down significantly, with temperatures ranging from a minimum of 6°C (44°F) to an average of 15°C (59°F), and a maximum of 23°C (74°F). Additionally, September experiences higher precipitation levels at 164 mm (6.4 in) across 10 days, while October sees less rain, totaling 107 mm (4.2 in) over the same number of days. The humidity also rises in October to 83%, compared to 64% in September, highlighting the transition to a cooler and more humid climate. For more detailed information, check out Koper weather in October.
September and November present quite a contrast in weather. September experiences milder temperatures, with averages around 20°C (68°F) and a maximum reaching 32°C (90°F), while November cools down significantly, averaging just 11°C (52°F) and peaking at 20°C (68°F). Both months see a fair amount of rainfall; however, November has slightly more precipitation at 176 mm (6.9 in) over 12 days compared to September's 164 mm (6.4 in) over 10 days. Furthermore, humidity levels rise in November to 89%, compared to September's 64%, contributing to a much chillier and damp feel during the later month. For a more detailed look at November conditions, check out Koper weather in November.
September and December present stark contrasts in weather. In September, temperatures range from a comfortable minimum of 9°C (49°F) to a warm maximum of 32°C (90°F), with an average of 20°C (68°F). The month sees a total precipitation of 164 mm (6.4 in) over about 10 days, accompanied by a moderate humidity level of 64%. In contrast, December experiences much colder temperatures, with a minimum of -1°C (30°F) and a maximum of 15°C (60°F), averaging 7°C (44°F). Precipitation is slightly lower at 150 mm (5.9 in), but it occurs over more days, totaling 12, and the humidity rises significantly to 88%. For more details on December conditions, check out Koper weather in December.
As summer gracefully transitions into fall, September in Koper offers a delightful blend of warmth and mild temperatures. While the month experiences a noticeable drop from the intense summer heat, with average highs around a comfortable 20°C, the lingering warmth still allows for enjoyable outdoor activities. With precipitation making its presence felt on about a third of the days, the humidity remains at a moderate level, creating a refreshing atmosphere. This blend of factors distinguishes September from the hotter summer months and sets the stage for a beautiful autumn. For more insights into the yearly weather patterns, explore the full details at Koper Climate.