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September

Koper Weather in September with Sea Temperature

September weather in Koper includes average daytime air +24°C, nighttime +16°C, average sea temperature +23°C. Daily water temperatures usually range from +21°C to +25°C, which is mild for beach planning. The tables below also show air temperature, wind, rain and humidity; for near-term water data, open the current 30-day water temperature forecast.

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Averaged values across several years

Daily air temperature for the month

Day Night

Daily sea water temperature for the month

Water

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September	Day	Night	Sea t°	Wind	Precip	Humidity
1Mon	+26°C	+18°C	+25°C	3 m/s	0.6 mm	67%
2Tue	+27°C	+18°C	+24°C	2 m/s	0.2 mm	65%
3Wed	+27°C	+18°C	+24°C	2 m/s	0 mm	68%
4Thu	+28°C	+17°C	+24°C	2 m/s	0 mm	66%
5Fri	+28°C	+18°C	+24°C	3 m/s	0 mm	64%
6Sat	+27°C	+18°C	+24°C	2 m/s	0.1 mm	66%
7Sun	+28°C	+18°C	+24°C	3 m/s	0.1 mm	63%
8Mon	+27°C	+18°C	+24°C	3 m/s	0.4 mm	64%
9Tue	+27°C	+17°C	+24°C	2 m/s	2 mm	67%
10Wed	+26°C	+17°C	+24°C	2 m/s	1.4 mm	69%
11Thu	+26°C	+17°C	+24°C	2 m/s	0.7 mm	68%
12Fri	+26°C	+16°C	+23°C	3 m/s	1.5 mm	68%
13Sat	+26°C	+16°C	+23°C	2 m/s	1.1 mm	65%
14Sun	+25°C	+17°C	+23°C	2 m/s	0.7 mm	69%
15Mon	+25°C	+17°C	+23°C	2 m/s	1 mm	70%
16Tue	+25°C	+16°C	+23°C	2 m/s	1.3 mm	73%
17Wed	+22°C	+16°C	+22°C	4 m/s	2.2 mm	77%
18Thu	+24°C	+15°C	+22°C	3 m/s	0 mm	73%
19Fri	+24°C	+16°C	+23°C	3 m/s	1 mm	72%
20Sat	+24°C	+15°C	+22°C	3 m/s	0.2 mm	70%
21Sun	+24°C	+15°C	+22°C	3 m/s	0.5 mm	69%
22Mon	+23°C	+15°C	+22°C	3 m/s	3.8 mm	71%
23Tue	+22°C	+14°C	+22°C	2 m/s	1.2 mm	76%
24Wed	+21°C	+14°C	+22°C	3 m/s	1.1 mm	81%
25Thu	+21°C	+13°C	+21°C	3 m/s	3.9 mm	83%
26Fri	+21°C	+14°C	+21°C	3 m/s	1.2 mm	81%
27Sat	+22°C	+14°C	+21°C	3 m/s	0.3 mm	74%
28Sun	+21°C	+13°C	+21°C	3 m/s	1.5 mm	78%
29Mon	+22°C	+13°C	+21°C	2 m/s	0.7 mm	71%
30Tue	+20°C	+13°C	+21°C	3 m/s	1.1 mm	72%

Sea water temperature by months

Water +23°C

Day and night air temperature

Day +24°C Night +16°C

Weather highs and lows in Koper for september

Warmest day: 5 september, +28°C
Coldest night: 28 september, +13°C
Max precipitation: 25 september, 3.9 mm
Warmest sea water: 1 september, +25°C
Coldest sea water: 25 september, +21°C

Climate in Koper in september

Average daytime temperature: +24°C
Average nighttime temperature: +16°C
Sea water temperature: —
Precipitation (monthly average): 29.7 mm
Days with precipitation: 6.7
Humidity: 71%
Wind: 3 m/s
Data: 6 years / coverage 100%

Daily air temperature for the month

Day Night

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September	Day	Night	Sea t°	Wind	Precip	Humidity
1Mon	+26°C	+16°C	—	2-3 m/s, WSW	0 mm	70%
2Tue	+25°C	+17°C	—	2-3 m/s, SSE	0.9 mm	84%
3Wed	+27°C	+17°C	—	1-2 m/s, NE	0 mm	78%
4Thu	+28°C	+17°C	—	1-2 m/s, WNW	0 mm	71%
5Fri	+27°C	+18°C	—	2 m/s, W	0 mm	71%
6Sat	+26°C	+17°C	—	2-3 m/s, NNE	0 mm	77%
7Sun	+26°C	+16°C	—	2 m/s, NNW	0 mm	70%
8Mon	+26°C	+16°C	—	2 m/s, WNW	0 mm	69%
9Tue	+25°C	+17°C	—	1 m/s, ESE	0 mm	69%
10Wed	+20°C	+17°C	—	2 m/s, ENE	7 mm	94%
11Thu	+22°C	+16°C	—	2 m/s, S	3.9 mm	90%
12Fri	+25°C	+15°C	—	2 m/s, SSW	0.7 mm	80%
13Sat	+25°C	+16°C	—	1-2 m/s, SW	0 mm	71%
14Sun	+23°C	+15°C	—	2 m/s, SW	2.1 mm	88%
15Mon	+25°C	+15°C	—	1-2 m/s, WNW	0 mm	79%
16Tue	+24°C	+14°C	—	2 m/s, SSW	1.3 mm	83%
17Wed	+24°C	+13°C	—	3-4 m/s, NE	0.1 mm	74%
18Thu	+26°C	+14°C	—	1-2 m/s, NNW	0 mm	67%
19Fri	+28°C	+16°C	—	1-2 m/s, WNW	0 mm	68%
20Sat	+27°C	+18°C	—	1-2 m/s, W	0 mm	70%
21Sun	+27°C	+17°C	—	1-2 m/s, WSW	0 mm	72%
22Mon	+26°C	+17°C	—	3-4 m/s, SW	1 mm	74%
23Tue	+21°C	+17°C	—	2 m/s, ENE	1.7 mm	90%
24Wed	+21°C	+13°C	—	2-3 m/s, ESE	3 mm	88%
25Thu	+21°C	+11°C	—	2-3 m/s, SW	0.6 mm	84%
26Fri	+19°C	+11°C	—	2 m/s, NW	0.2 mm	85%
27Sat	+22°C	+12°C	—	2 m/s, NE	0 mm	75%
28Sun	+22°C	+11°C	—	2-3 m/s, NE	0 mm	74%
29Mon	+21°C	+12°C	—	2 m/s, NNE	0 mm	66%
30Tue	+16°C	+10°C	—	3-4 m/s, ENE	0 mm	75%

Weather highs and lows in Koper for september

Warmest day: 4 september, +28°C
Coldest night: 30 september, +10°C
Max precipitation: 10 september, 7 mm
Warmest water: —
Coldest water: —

Climate in Koper in september

Year: 2025
Average daytime temperature: +24°C
Average nighttime temperature: +15°C
Water temperature: —
Precipitation (month): 22.5 mm
Days with precipitation: 7
Humidity: 77%
Wind: 2 m/s

Daily air temperature for the month

Day Night

Daily sea water temperature for the month

Water

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September	Day	Night	Sea t°	Wind	Precip	Humidity
1Sun	+34°C	+23°C	+25°C	2-3 m/s, WNW	0 mm	42%
2Mon	+33°C	+23°C	+24°C	2-3 m/s, WNW	0 mm	45%
3Tue	+30°C	+21°C	+24°C	2-3 m/s, W	0 mm	67%
4Wed	+30°C	+20°C	+24°C	2 m/s, WNW	0 mm	63%
5Thu	+30°C	+19°C	+24°C	2-3 m/s, WSW	0 mm	67%
6Fri	+25°C	+18°C	+24°C	1-2 m/s, SSW	0.3 mm	84%
7Sat	+27°C	+18°C	+24°C	2 m/s, W	0 mm	76%
8Sun	+28°C	+18°C	+24°C	2-3 m/s, W	0.3 mm	79%
9Mon	+23°C	+16°C	+24°C	3-4 m/s, WSW	6 mm	90%
10Tue	+26°C	+15°C	+24°C	2 m/s, NW	0 mm	69%
11Wed	+25°C	+16°C	+24°C	2 m/s, WNW	0 mm	66%
12Thu	+19°C	+11°C	+23°C	4-7 m/s, S	8.2 mm	88%
13Fri	+16°C	+10°C	+23°C	5-8 m/s, NE	6.4 mm	78%
14Sat	+17°C	+10°C	+23°C	2 m/s, NW	1 mm	74%
15Sun	+19°C	+12°C	+23°C	1-2 m/s, S	0.1 mm	64%
16Mon	+21°C	+10°C	+23°C	2 m/s, NW	0.1 mm	62%
17Tue	+17°C	+12°C	+22°C	6-8 m/s, ENE	0 mm	70%
18Wed	+23°C	+14°C	+22°C	7-8 m/s, ENE	0 mm	62%
19Thu	+23°C	+17°C	+23°C	6-7 m/s, ENE	0 mm	58%
20Fri	+22°C	+15°C	+22°C	5-6 m/s, ENE	0 mm	61%
21Sat	+25°C	+13°C	+22°C	3 m/s, NE	0 mm	66%
22Sun	+24°C	+12°C	+22°C	2 m/s, W	0 mm	62%
23Mon	+23°C	+14°C	+22°C	1-2 m/s, W	0 mm	70%
24Tue	+20°C	+14°C	+22°C	3-4 m/s, SSW	3.1 mm	90%
25Wed	+20°C	+13°C	+21°C	3-4 m/s, S	0.8 mm	90%
26Thu	+20°C	+15°C	+21°C	4 m/s, SW	1 mm	88%
27Fri	+22°C	+16°C	+21°C	6 m/s, S	0.1 mm	81%
28Sat	+21°C	+12°C	+21°C	4-6 m/s, S	0 mm	83%
29Sun	+19°C	+10°C	+21°C	2-4 m/s, NE	0 mm	70%
30Mon	+18°C	+8°C	+21°C	2-3 m/s, NNW	0 mm	64%

Weather highs and lows in Koper for september

Warmest day: 1 september, +34°C
Coldest night: 30 september, +8°C
Max precipitation: 12 september, 8.2 mm
Warmest water: 1 september, +25°C
Coldest water: 25 september, +21°C

Climate in Koper in september

Year: 2024
Average daytime temperature: +23°C
Average nighttime temperature: +15°C
Water temperature: —
Precipitation (month): 27.4 mm
Days with precipitation: 6
Humidity: 71%
Wind: 3 m/s

Daily air temperature for the month

Day Night

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September	Day	Night	Sea t°	Wind	Precip	Humidity
1Fri	+25°C	+16°C	—	1-2 m/s, W	0.5 mm	74%
2Sat	+26°C	+16°C	—	1-2 m/s, WNW	0 mm	76%
3Sun	+26°C	+18°C	—	1-2 m/s, NW	0 mm	74%
4Mon	+27°C	+17°C	—	4 m/s, ENE	0 mm	65%
5Tue	+26°C	+16°C	—	5-8 m/s, NE	0 mm	56%
6Wed	+29°C	+16°C	—	3-4 m/s, NE	0 mm	58%
7Thu	+29°C	+17°C	—	4-5 m/s, ENE	0 mm	56%
8Fri	+31°C	+17°C	—	3-4 m/s, NE	0 mm	50%
9Sat	+31°C	+17°C	—	3 m/s, NE	0 mm	54%
10Sun	+31°C	+17°C	—	2-3 m/s, N	0 mm	54%
11Mon	+29°C	+17°C	—	2 m/s, WNW	0 mm	57%
12Tue	+28°C	+18°C	—	2 m/s, W	0 mm	62%
13Wed	+28°C	+19°C	—	1-2 m/s, SW	0 mm	64%
14Thu	+28°C	+18°C	—	2 m/s, NW	0.8 mm	70%
15Fri	+26°C	+16°C	—	2 m/s, NE	0.1 mm	80%
16Sat	+27°C	+17°C	—	2 m/s, W	0 mm	70%
17Sun	+25°C	+17°C	—	1-2 m/s, WNW	0 mm	78%
18Mon	+26°C	+18°C	—	2 m/s, W	0 mm	78%
19Tue	+24°C	+17°C	—	3-4 m/s, SE	3 mm	84%
20Wed	+26°C	+16°C	—	2 m/s, SW	0 mm	78%
21Thu	+24°C	+16°C	—	3 m/s, S	1.4 mm	76%
22Fri	+23°C	+17°C	—	4 m/s, SSW	8.9 mm	89%
23Sat	+22°C	+14°C	—	3-5 m/s, SSE	3 mm	85%
24Sun	+21°C	+14°C	—	4-5 m/s, NE	0 mm	73%
25Mon	+23°C	+12°C	—	5-6 m/s, NE	0 mm	65%
26Tue	+27°C	+15°C	—	4-5 m/s, ENE	0 mm	70%
27Wed	+27°C	+16°C	—	4-6 m/s, NE	0 mm	57%
28Thu	+27°C	+14°C	—	3 m/s, NE	0 mm	56%
29Fri	+27°C	+15°C	—	2-3 m/s, NE	0 mm	60%
30Sat	+28°C	+15°C	—	2 m/s, NNE	0 mm	57%

Weather highs and lows in Koper for september

Warmest day: 8 september, +31°C
Coldest night: 25 september, +12°C
Max precipitation: 22 september, 8.9 mm
Warmest water: —
Coldest water: —

Climate in Koper in september

Year: 2023
Average daytime temperature: +27°C
Average nighttime temperature: +16°C
Water temperature: —
Precipitation (month): 17.7 mm
Days with precipitation: 4
Humidity: 68%
Wind: 3 m/s

Daily air temperature for the month

Day Night

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September	Day	Night	Sea t°	Wind	Precip	Humidity
1Thu	+23°C	+19°C	—	5-6 m/s, ENE	0 mm	70%
2Fri	+27°C	+17°C	—	3-4 m/s, SSW	0 mm	60%
3Sat	+25°C	+17°C	—	2 m/s, SSE	0 mm	67%
4Sun	+27°C	+17°C	—	2 m/s, WSW	0 mm	74%
5Mon	+29°C	+18°C	—	2-3 m/s, SE	0 mm	70%
6Tue	+29°C	+18°C	—	1-2 m/s, WNW	0 mm	63%
7Wed	+28°C	+19°C	—	1-2 m/s, W	0.4 mm	61%
8Thu	+24°C	+20°C	—	3-4 m/s, SSE	2 mm	78%
9Fri	+25°C	+18°C	—	2-4 m/s, SE	5.9 mm	85%
10Sat	+25°C	+17°C	—	2-3 m/s, SSE	1.5 mm	82%
11Sun	+26°C	+16°C	—	2 m/s, S	0.3 mm	72%
12Mon	+26°C	+16°C	—	2 m/s, S	0 mm	66%
13Tue	+25°C	+15°C	—	2 m/s, NW	0 mm	67%
14Wed	+25°C	+18°C	—	3-4 m/s, SSW	0 mm	75%
15Thu	+25°C	+19°C	—	4 m/s, SSW	6 mm	88%
16Fri	+24°C	+16°C	—	3 m/s, SSE	1 mm	91%
17Sat	+16°C	+13°C	—	6-7 m/s, ENE	9.2 mm	90%
18Sun	+19°C	+12°C	—	2-3 m/s, SW	0 mm	83%
19Mon	+21°C	+13°C	—	2-3 m/s, ENE	0 mm	74%
20Tue	+22°C	+12°C	—	2-3 m/s, SSW	0 mm	69%
21Wed	+19°C	+12°C	—	4-5 m/s, ENE	0 mm	62%
22Thu	+21°C	+11°C	—	3-4 m/s, ENE	0 mm	59%
23Fri	+20°C	+11°C	—	2-3 m/s, SSW	0 mm	61%
24Sat	+19°C	+12°C	—	3-5 m/s, S	0 mm	76%
25Sun	+17°C	+14°C	—	3-5 m/s, E	2.4 mm	95%
26Mon	+19°C	+14°C	—	1-2 m/s, SW	0.2 mm	92%
27Tue	+18°C	+13°C	—	2-3 m/s, E	0.2 mm	87%
28Wed	+18°C	+12°C	—	3-4 m/s, SE	2.4 mm	91%
29Thu	+19°C	+14°C	—	4 m/s, S	4.2 mm	92%
30Fri	+20°C	+15°C	—	3-4 m/s, S	6.4 mm	91%

Weather highs and lows in Koper for september

Warmest day: 5 september, +29°C
Coldest night: 22 september, +11°C
Max precipitation: 17 september, 9.2 mm
Warmest water: —
Coldest water: —

Climate in Koper in september

Year: 2022
Average daytime temperature: +23°C
Average nighttime temperature: +15°C
Water temperature: —
Precipitation (month): 42.1 mm
Days with precipitation: 10
Humidity: 76%
Wind: 3 m/s

Daily air temperature for the month

Day Night

Tap a date to open detailed weather for that day

September	Day	Night	Sea t°	Wind	Precip	Humidity
1Wed	+28°C	+16°C	—	2 m/s, S	0 mm	67%
2Thu	+27°C	+16°C	—	2-3 m/s, SSW	0 mm	56%
3Fri	+27°C	+16°C	—	2-3 m/s, SSE	0 mm	56%
4Sat	+28°C	+16°C	—	2-3 m/s, SE	0.1 mm	60%
5Sun	+29°C	+18°C	—	3-4 m/s, ENE	0 mm	54%
6Mon	+29°C	+17°C	—	3 m/s, NE	0 mm	47%
7Tue	+29°C	+17°C	—	3 m/s, ENE	0 mm	46%
8Wed	+29°C	+17°C	—	2-4 m/s, E	0 mm	44%
9Thu	+28°C	+15°C	—	2 m/s, SSE	0 mm	40%
10Fri	+27°C	+16°C	—	2 m/s, WSW	0 mm	48%
11Sat	+27°C	+15°C	—	1-2 m/s, WNW	0 mm	60%
12Sun	+29°C	+18°C	—	2 m/s, SSE	0 mm	50%
13Mon	+29°C	+17°C	—	2-3 m/s, SSE	0 mm	47%
14Tue	+29°C	+18°C	—	1-2 m/s, S	0 mm	48%
15Wed	+27°C	+20°C	—	2 m/s, WSW	0 mm	52%
16Thu	+25°C	+19°C	—	3-4 m/s, SSW	5.6 mm	71%
17Fri	+21°C	+18°C	—	2 m/s, SE	4.1 mm	93%
18Sat	+23°C	+16°C	—	2 m/s, E	0 mm	90%
19Sun	+20°C	+16°C	—	2 m/s, ESE	3.2 mm	92%
20Mon	+20°C	+14°C	—	4 m/s, E	1.3 mm	89%
21Tue	+22°C	+13°C	—	4-5 m/s, NE	0 mm	68%
22Wed	+21°C	+13°C	—	3 m/s, ENE	0 mm	63%
23Thu	+22°C	+13°C	—	2-3 m/s, SSE	0 mm	65%
24Fri	+24°C	+13°C	—	1-2 m/s, WSW	0 mm	77%
25Sat	+23°C	+14°C	—	1-2 m/s, NW	0 mm	80%
26Sun	+24°C	+16°C	—	2 m/s, WSW	1.7 mm	81%
27Mon	+23°C	+17°C	—	2-3 m/s, SW	0.1 mm	81%
28Tue	+26°C	+16°C	—	2-3 m/s, ENE	0 mm	72%
29Wed	+25°C	+18°C	—	2 m/s, SSW	0 mm	63%
30Thu	+19°C	+15°C	—	6 m/s, ENE	0 mm	76%

Weather highs and lows in Koper for september

Warmest day: 5 september, +29°C
Coldest night: 21 september, +13°C
Max precipitation: 16 september, 5.6 mm
Warmest water: —
Coldest water: —

Climate in Koper in september

Year: 2021
Average daytime temperature: +25°C
Average nighttime temperature: +16°C
Water temperature: —
Precipitation (month): 16.1 mm
Days with precipitation: 5
Humidity: 65%
Wind: 2 m/s

Daily air temperature for the month

Day Night

Tap a date to open detailed weather for that day

September	Day	Night	Sea t°	Wind	Precip	Humidity
1Tue	+22°C	+16°C	—	3-4 m/s, WSW	3 mm	78%
2Wed	+25°C	+17°C	—	2 m/s, S	0.1 mm	68%
3Thu	+26°C	+17°C	—	2-4 m/s, S	0 mm	67%
4Fri	+27°C	+17°C	—	2 m/s, S	0 mm	63%
5Sat	+27°C	+18°C	—	1-2 m/s, WSW	0 mm	67%
6Sun	+26°C	+19°C	—	1-2 m/s, WSW	0.1 mm	69%
7Mon	+26°C	+19°C	—	3-4 m/s, ENE	0 mm	66%
8Tue	+26°C	+18°C	—	4-5 m/s, NE	0 mm	62%
9Wed	+27°C	+16°C	—	2-3 m/s, SSE	0 mm	64%
10Thu	+28°C	+19°C	—	2 m/s, S	0 mm	64%
11Fri	+28°C	+19°C	—	3-4 m/s, ENE	0 mm	64%
12Sat	+29°C	+20°C	—	3-4 m/s, SSW	0 mm	63%
13Sun	+31°C	+20°C	—	3-4 m/s, ENE	0 mm	60%
14Mon	+30°C	+21°C	—	4 m/s, ENE	0 mm	58%
15Tue	+30°C	+20°C	—	3-4 m/s, ENE	0 mm	55%
16Wed	+29°C	+20°C	—	2-3 m/s, S	0 mm	60%
17Thu	+29°C	+20°C	—	4-5 m/s, ENE	0 mm	58%
18Fri	+25°C	+18°C	—	6-7 m/s, ENE	0 mm	57%
19Sat	+26°C	+15°C	—	3-6 m/s, NE	0 mm	56%
20Sun	+26°C	+16°C	—	2-3 m/s, SSE	0 mm	50%
21Mon	+25°C	+17°C	—	1 m/s, SW	1.7 mm	67%
22Tue	+23°C	+17°C	—	2 m/s, SSE	13.1 mm	76%
23Wed	+21°C	+17°C	—	2-3 m/s, S	2.3 mm	86%
24Thu	+22°C	+17°C	—	2-3 m/s, S	0.4 mm	84%
25Fri	+21°C	+14°C	—	5-6 m/s, SSW	19.7 mm	84%
26Sat	+15°C	+10°C	—	3-6 m/s, W	3.9 mm	71%
27Sun	+18°C	+10°C	—	2-3 m/s, SW	1.1 mm	65%
28Mon	+13°C	+11°C	—	4-8 m/s, SSW	6.7 mm	90%
29Tue	+18°C	+10°C	—	2 m/s, W	0 mm	75%
30Wed	+19°C	+13°C	—	1 m/s, WSW	0 mm	70%

Weather highs and lows in Koper for september

Warmest day: 13 september, +31°C
Coldest night: 26 september, +10°C
Max precipitation: 25 september, 19.7 mm
Warmest water: —
Coldest water: —

Climate in Koper in september

Year: 2020
Average daytime temperature: +25°C
Average nighttime temperature: +17°C
Water temperature: —
Precipitation (month): 52.1 mm
Days with precipitation: 8
Humidity: 67%
Wind: 3 m/s

Weather in Koper in september by year

Year	Day	Night	Precipitation	Days with precipitation	Water
2025	+24°C	+15°C	22.5 mm	7	—
2024	+23°C	+15°C	27.4 mm	6	—
2023	+27°C	+16°C	17.7 mm	4	—
2022	+23°C	+15°C	42.1 mm	10	—
2021	+25°C	+16°C	16.1 mm	5	—
2020	+25°C	+17°C	52.1 mm	8	—

Comparison september in Koper with other months

Month	Day	Night	Days with precipitation	Sunny days
January	+9°C	+2°C	5	12
February	+11°C	+3°C	4	9
March	+13°C	+5°C	5	14
April	+16°C	+8°C	5	11
May	+21°C	+12°C	6	9
June	+27°C	+18°C	4	15
July	+30°C	+20°C	4	18
August	+30°C	+20°C	4	18
September	+24°C	+16°C	7	15
October	+19°C	+11°C	6	13
November	+13°C	+6°C	6	11
December	+10°C	+4°C	5	11