Climate and monthly weather forecast
Koper, Slovenia


The climate of Koper

In the coastal city of Koper, Slovenia, the prevalent climatic condition is of the 'Marine West Coast, Warm Summer' type, classified as 'Cfb' according to the Köppen climate classification system. Geographically, the town sits along the Adriatic Sea, which influences the relatively mild and damp weather experienced throughout the year.

Throughout the seasons, variations in temperature, daylight hours, and sea temperature are exhibited. The sea surrounding Koper exhibits an average temperature oscillation from 9.3°C (48.7°F) to 24.8°C (76.6°F). Notably, the warmest sea temperatures tend to occur in July and August, hitting highs of 24.8°C (76.6°F), while the chilliest occur in February, dropping to a low of 9.3°C (48.7°F).

Daylight hours, on the other hand, exhibit a yearly range from a low of 8.8 hours in December to a high of 15.6 hours in June. The longest days consequently occur in the summer period while the shortest days are experienced in the winter months, particularly December.

The best time to visit Koper

Based on weather patterns in Koper, the best time to visit Koper is between June and August. During these summer months, visitors can enjoy warm sea temperatures averaging 24.8°C (76.6°F), ideal for various water-related activities including swimming and paddleboarding. The daylight hours are long, averaging 15.3 hours, leaving plenty of sunshine for outdoor activities.

The worst time to visit Koper

The worst time to visit Koper, Slovenia, tend to be the colder months from December to February. Sea temperatures during this period average around 9.3°C (48.7°F) to 10.3°C (50.5°F), which could make dip a bit uncomfortable and discourage outdoor water activities. The daylight hours are significantly shorter, averaging around 8.8 to 9.2 hours, limiting the time for outdoor exploration and activities.

Spring weather in Koper

The spring weather in Koper, from March to May, marks a gradual transition from the cold winter season. Sea temperatures begin to warm up, from an average of 10.1°C (50.2°F) in March to 18°C (64.4°F) in May. Meanwhile, daylight hours also increase significantly, from an average of 11.9 hours in March to 14.9 hours in May, allowing for longer outdoor activities.

Summer weather in Koper

The summer in Koper, from June to August, offers the warmest and longest days of the year. Sea temperatures peak to high averages of 24.8°C (76.6°F), providing a perfect setting for water sports and beach leisure. Long daylight hours averaging 15.3 hours in June to 14.1 hours in August, facilitate plenty of time for sightseeing and exploration.

Autumn weather in Koper

Autumn weather in Koper, from September to November, illustrates a cooling trend as it transitions from summer to winter. Sea temperatures decrease from an average of 23.3°C (73.9°F) in September to a cooler 13.2°C (55.8°F) in November. Daylight hours also begin to shorten, ranging from 12.5 hours in September to 9.5 hours in November.

Winter weather in Koper

Winter weather in Koper, from December to February, is characterized by the coldest sea temperatures and the shortest daylight hours of the year. Sea temperatures drop to their lowest between 9.3°C (48.7°F) in February and 10.3°C (50.5°F) in December. Daylight hours decrease to their minimum value with an average of 8.8 hours in December to 9.5 hours in February. Despite these conditions, Koper's coastal location still tends to moderate the winter chill compared with many inland locations.

Weather in January

January in Koper, Slovenia, ushers in the new year with its distinct winter conditions. Chilly conditions prevail with the sea temperature sees its most prominent drop. The sea temperature plunges to a cooler 10.3°C (50.5°F), signaling a sharp contrast from the latter months. Weather in January »

Weather in February

February in Koper brings a slow transition from the chilly grasp of January. The sea gradually cools further to 9.3°C (48.7°F), marking the lowest sea temperature for the year. As winter reaches its climax, daylight increases slightly yet remains limited, urging dwellers to make the most of the sunlit hours. Weather in February »

Weather in March

The weather chart for Koper in March shows signs of resilience as the frosty period starts to recede. The sea temperature initiates its recovery, increasing slightly to 10.1°C (50.2°F). This minor increase signifies the imminent farewell to winter, as the natural world begins to awaken. Weather in March »

Weather in April

The month of April in Koper speaks volumes about the inspirational transition seasons offer. A comforting warmth diffuses into the sea, with the temperature rising to 13.1°C (55.6°F). April presents longer daylight hours, complementing the rebirth of flora dispelled by the winter frost. Weather in April »

Weather in May

May ushers in the advent of summer in Koper. The thermal transition deepens as the sea water warms up to a pleasant 18°C (64.4°F). The illuminating sunshine permeates the days for longer durations, creating a harmonious blend of warmth and light. Weather in May »

Weather in June

June introduces the full swing of summer to Koper, turning the city into a lively haven. With the sea temperature reaching 22.8°C (73°F), residents revel in the aquatic amenities on offer. The longest daylight hours of the year further add to the joys of summer. Weather in June »

Weather in July

July in Koper witnesses the peak of the summertime temperatures where the sea surface reaches a warm 24.8°C (76.6°F). This is the warmest month of the year, encouraging bathers to indulge in beachside activities. Despite the intense heat, the city thrives, basking in the ample daylight and welcoming the high season of tourism. Weather in July »

Weather in August

August, despite being the culmination of summer, holds onto the warmth with the sea temperature remaining at an inviting 24.8°C (76.6°F). The city continues to flourish under the sun's beneficent gaze allowing outdoor activities to persist. Weather in August »

Weather in September

Koper's weather in September heralds the arrival of autumn, with a slight diminution in sea temperature to 23.3°C (73.9°F). The receding heat signals the end of the hot summer days, adding a hint of freshness in the air. Yet, the lingering warmth and extended daylight hours make September an appealing month for late summer visitors. Weather in September »

Weather in October

Koper in October feels the sturdy grip of autumn as the temperature continues to fall. The sea temperature drops to a cooler 19°C (66.2°F), indicating a shift from the summer's warmth. As daylight hours reduce further, the city shows its readiness to welcome the colder months. Weather in October »

Weather in November

November in Koper announces the onset of winter months. The sea temperature plunges to the lower side of 16.1°C (61°F). As the daylight hours become shorter, the city begins to retreat into its wintry slumber. The landscapes transition from autumnal colors to winter whites, preparing for the chilly months ahead. Weather in November »

Weather in December

The weather in Koper during December fully embraces winter, marking a full circle in the annual weather cycle. The sea temperature sinks further to 13.2°C (55.8°F). The reduced daylight hours accompany the shortest day of the year towards the end of the month. Weather in December »

Frequently asked questions

When is the sea coldest in Koper?

February is the month with the coldest seawater in Koper, Slovenia, with an average sea temperature of 9.3°C (48.7°F).

When are the longest days in Koper?

June has the longest days of the year in Koper, with an average of 15h and 36min of daylight.

What months are the sea warmest in Koper?

July and August, with an average sea temperature of 24.8°C (76.6°F), are months with the warmest seawater in Koper, Slovenia.

When is Daylight Saving Time (DST) in Koper?

On Sunday, 27. October 2024, at 03:00, Daylight Saving Time ends in Koper, Slovenia, and the time zone changes from CEST to CET. The next Daylight Saving Time starts on Sunday, 30. March 2025, at 02:00, and the time zone reverts from CET to CEST.

What is the month with the shortest days in Koper?

With an average of 8h and 48min of daylight, December has the shortest days of the year in Koper, Slovenia.

Average sea temperature
Koper, Slovenia

Average sea temperature - Koper, Slovenia

The best months for swimming (with the highest average sea temperature) are July and August (24.8°C).
The coldest month (with the lowest average sea temperature) is February (9.3°C).


Average daylight
Koper, Slovenia

Average daylight - Koper, Slovenia

The month with the longest days is June (Average daylight: 15h and 36min).
The month with the shortest days is December (Average daylight: 8h and 48min).


Koper, Slovenia

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