Koper enjoys a Mediterranean climate with hot, sunny summers and mild, relatively wet winters. Summer highs reach 28–30°C, while winter lows rarely fall below 1°C. Rain falls year-round, peaking in autumn, but sunshine is abundant from May to September. The city’s coastal location brings refreshing breezes, making Koper a pleasant destination in all seasons.
The best times to travel section shows how the months compare for a visit, so you can find the time of year that fits what you want to do.
Background colours of the months:
The colour shows the typical temperature: yellow (hot), green (mild) and blue (cold). How strong the colour is shows the travel season: full colour means high season, soft colour means shoulder season and soft-striped means off season.
Weather symbols:
Each month has one symbol showing what the weather is typically like, such as hot and sunny, freezing or a rainy or snowy season. Use them to quickly spot months that match the weather you want, or to avoid the ones that don't.
Crowdedness:
The people icon shows how busy the place usually is. The more people, the more crowded it gets.
Additional notes:
The grey info boxes point out special things worth knowing, like recurring weather issues or seasonal events.
Koper, the largest city on Slovenia’s Adriatic coast, features a Mediterranean climate with four distinct seasons. Summers (June–August) are hot and sunny, with average highs of 28–30°C in July and August and pleasant evenings around 17°C. There are about 10–11 hours of sunshine daily at the height of summer, and sea breezes help temper the heat. Occasional thunderstorms or brief showers can interrupt the sunshine, but overall, summer is ideal for swimming and outdoor activities. The sea temperature peaks at 24°C in August, making the beaches especially inviting.
Winters (December–February) are mild compared to inland Slovenia, with average highs of 8–9°C and lows near 1–3°C. Frost and snow are rare, though the cold bora wind can bring blustery, chilly weather. Rain is more frequent in winter, and cloudy days are common, particularly in December and January. Spring (March–May) and autumn (September–November) are transitional, featuring mild to warm temperatures (15–25°C), blooming or colourful landscapes, and moderate rainfall. Rain peaks in September and November, with up to 120–180 mm per month, while July is typically the driest. Koper receives about 1,300–1,400 mm of precipitation annually and enjoys 2,000+ hours of sunshine. Winds are generally light to moderate, but the bora and jugo winds can bring sudden weather changes, especially in winter and spring.
| Average climate data for Koper, Slovenia | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average water temperature (°C) | 10 | 9 | 10 | 13 | 18 | 23 | 25 | 25 | 23 | 19 | 16 | 13 | 17 |
| Average daily daylight hours (h) | 9 | 10 | 11 | 13 | 14 | 15 | 15 | 14 | 12 | 10 | 9 | 8 | 12 |
The best time to visit Koper is from late May to September, when temperatures are warm to hot (22–30°C), sunshine is abundant, and the Adriatic Sea is perfect for swimming. These months are ideal for beach activities, festivals, and exploring the Old Town. Late spring and early autumn offer pleasant weather and fewer crowds, making them great for sightseeing and outdoor adventures.
The least favourable time to visit is from November to February, when rain is most frequent, days are shortest, and temperatures are coolest (highs of 8–10°C, lows near 1–3°C). While winters are mild, frequent rain, cloudy skies, and occasional strong winds can limit outdoor activities, though the city remains charming and tranquil.
Koper has hot, sunny summers (highs 28–30°C) and mild, wet winters (highs 8–9°C). Rain falls year-round, peaking in autumn, while summer is the driest and sunniest season. The city enjoys over 2,000 hours of sunshine annually.
Snow is rare in Koper due to its mild coastal climate. Winters are generally rainy and mild, with lows near 1°C, but occasional cold spells can bring a dusting of snow, which melts quickly.
July and August are the sunniest months, with up to 11 hours of sunshine daily and long daylight hours. Even in spring and autumn, Koper enjoys several hours of sun per day.
The Adriatic Sea in Koper warms to 24°C in August, making it ideal for swimming from June to September. In May and October, the sea is cooler but still pleasant for many visitors.
Pack light, breathable clothes and sun protection for summer, layers and a rain jacket for spring and autumn, and a warm coat for winter evenings. Comfortable shoes are useful year-round, especially for exploring the Old Town.
Koper experiences light to moderate winds year-round, with the bora bringing cold gusts in winter and the jugo bringing rain from the south. Winds are usually strongest from November to March.
Koper is least crowded in winter (November–February) and early spring. These periods offer quieter streets and attractions, but weather may be wetter and less suitable for outdoor sightseeing.
The month with the highest average water temperature is August (24.9 °C). The month with the lowest average water temperature is February (9.2 °C). Overall, the average water temperature over the whole year is 17.1 °C.
The month with the longest days, so the most daylight, is June (Average daylight: 15.1 h). The month with the shortest days, so the least daylight, is December (Average daylight: 8.1 h). Over the whole year there are 11.7 h of daylight per day on average.
