Koper weather in December
Temperature, sea and sunshine in December: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in December
Poor
Best time to visit: June – August
What is the weather like in Koper in December?
In December, Koper is cold: daytime highs average 9 °C, and nights cool down to about 5 °C. The sea averages 13.2 °C – swimming is only for the hardy. Expect around 5 hours of sunshine a day. Rain is frequent, with about 10 rainy days and 110 mm in total. All in all, December is not an ideal month for a holiday in Koper.
December compared
How the weather changes from November to January. Tap a month to open it.
| NovemberNov | DecemberDec | JanuaryJan | |
|---|---|---|---|
| Score | 12 | 17 | 18 |
| Day | 13° | 9° | 8° |
| Night | 9° | 5° | 4° |
| Sea | 16° | 13° | 11° |
| Sun | 4 h | 5 h | 5 h |
| Rain days | 13 | 10 | 10 |
More details for December
- Daylight
- 8 h 44 min07:38 – 16:22
- UV index
- 1 · lowclear sky, noon (estimate)All months
- Muggy days
- 0 daysdew point 18 °C or moreAll months
- Wind
- 15 km/haverage daily peakAll months
- Cloud cover
- 59 %on averageAll months
- Hot days
- 0 days30 °C or moreAll months
- Snow days
- 1 day1 cm or more of fresh snow
- Time zone
- UTC+1Europe/Ljubljana
How the score comes together
- Temperatureweight 35 %0 %
- Seaweight 25 %0 %
- Sunshineweight 20 %27 %
- Few rainy daysweight 20 %58 %
Each factor is rated from 0 to 100 % and weighted for the travel style “Sun, sea & sand”.
What to pack in December
- Warm jacket
- Rain jacket or umbrella
Koper in December: quick answers
Is Koper hot in December?
No. In December, Koper is cold: daytime highs average 9 °C and nights drop to about 5 °C.
Can you swim in Koper in December?
Only if you don't mind cold water: in December the sea averages just 13.2 °C. Comfortable swimming is possible from June to September.
Does it rain much in Koper in December?
Rain is frequent, with about 10 rainy days and 110 mm in total.
Koper month by month
The whole year in KoperAll destinations: SloveniaWhere to go in DecemberSea temperature in December
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0). Sources & licences