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Koper weather in December

Weather in Koper: December

Average day temperature: 48.0°F
Average night temperature: 39.2°F
Sea water temperature: 55.2°F
Number of sunny days: 14 days
Day length: 8.7 - 9.0 hours
Number of rainy days: 4 days
Precipitation totals: 3.8 in.

Air temperature in December, °F

Show year:
2025
2024
2023

The highest day temperature during December of 2025 was 54°F. At the same time the lowest night temperature was 27°F. Daily and nightly averages during December were 50.8°F and 40.7°F.

Sea water temperature in Koper in December, °F

Show year:
2025
2024
2023

The average sea water temperature in December of 2025 was 55.5°F. The highest and lowest sea temperatures during the month were 56.8°F and 53.4°F.

Sunny, partly cloudy and cloudy days

Mostly all days in December are sunny but cloudy days are also possible.

Precipitation total in December, in.

Precipitation total value in Koper in December is 4.4 in. Other months of the year show relatively similar values.

Wind speed in December, mph

The average wind speed value in December is 4.9 mph It makes December lest windy month of the year.

Average sunny hours

This chart shows average number of hours during the day when sunlight can reach the ground. It depends on day length and cloudiness during the day. The average number of sunny hours in December is: 4.3.

Best time for vacation in Koper

Sunniest months:
August 23 days
July 22 days
June 20 days
Warmest months:
August 85.0 °F
July 84.8 °F
June 80.2 °F
Warmest sea temp:
August 78.4 °F
July 78.1 °F
September 73.8 °F
Coldest months:
January 45.6 °F
December 48.0 °F
February 48.1 °F
Rainiest months:
May 7 days
November 6 days
September 6 days
Windiest months:
March 6.6 mph
February 6.5 mph
November 6.2 mph

Koper on a weather map

Koper
+28°F
NW 2 mph
Feels like: +25°F
Precip.: 0%
Places in Slovenia:
Name
°F
+21°F
+28°F
+28°F
+21°F
+27°F
+19°F
+28°F
+28°F
+25°F
+28°F
+25°F
+27°F
24 Hours Forecast
Koper
Local time: 22:51
January 01, thursday
0000
28°F
NW
2 mph
0300
28°F
NW
2 mph
0600
28°F
NW
2 mph
0900
32°F
NW
2 mph
1200
39°F
NE
1 mph
1500
39°F
S
1 mph
1800
34°F
NW
1 mph
2100
30°F
NW
2 mph
Units of measurement: °C / °F