Koszalin weather in September

In September, Koszalin sees average daytime highs of 18°C and overnight lows near 11°C, with 68 mm of rain across 12.2 wet days and about 12.5 hours of daylight. It is the 4th-warmest and 4th-wettest month of the year here.

Highs ease over the month, from about 19°C in the first days to 16°C by the end. The sky is clear or mostly clear about 21% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 30 min at the start of September to 11 h 24 min by month's end. Set against the rest of the year, September is Koszalin's 6th-clearest and 7th-windiest month. For the whole year in context, see Koszalin's year-round climate.

Daytime high
18°
4th warmest
Overnight low
11°
9th coldest
Rainfall
68 mm
12.2 wet days
Daylight
12 h 24 min
5:37 AM – 6:02 PM
Cloud cover
64%
6th clearest
Wind
16 km/h
7th windiest
Solar energy
2.98 kWh/m²
Travel score
5.2
out of 10

Koszalin is city with powiat rights of Poland.

Air quality
Moderate
PM2.5 13.7 µg/m³ · 2019
Density
1,023/km²
people per km²
Founded
1266

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 19°C in the first days to 16°C by the end.

A typical September day in Koszalin reaches about 18°C in the afternoon and slips back to 11°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 14°C and 22°C. Set against its neighbours, September runs about 4°C cooler than August and about 5°C warmer than October.

10°15°20°25°151015202530
Avg high (°C)Avg low (°C)
12013
21913
31912
41912
51912
61912
71912
81912
91812
101812
111811
121811
131811
141811
151811
161811
171711
181710
191710
201710
211710
221710
231710
241610
251610
26169
27169
28169
29169
30159

How September really feels in Koszalin

Once humidity and wind are folded in, September averages 0 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
0
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

September sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Koszalin weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 4th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -1°5411.74.57.70.0
Feb / -1°4410.24.59.30.0
Mar / 4910.3311.50.6
Apr11° / 3890.513.73.0
May16° / 5610.80.115.75.0
Jun19° / 12°7112016.85.8
Jul21° / 14°9013.3016.46.1
Aug22° / 14°7813.4014.66.1
Sep18° / 11°6812.2012.55.2
Oct12° / 6612.50.110.23.1
Nov / 5311.81.38.20.8
Dec / 5812.447.20.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 21% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 18% of September, with mostly cloudy or overcast conditions the remaining 61%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
14456
24357
34357
44258
54159
64258
74258
84060
94060
104060
114060
124159
134060
144060
154060
163961
173961
183961
193961
203862
213862
223961
233961
243763
253763
263763
273664
283664
293664
303664

Chance of precipitation in September

Any precipitation

Koszalin gets around 68 mm of rain over 12.2 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 41% and peaks near 51% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%151015202530
Rain chance (%)
151
251
350
450
549
649
748
847
946
1045
1144
1243
1342
1440
1539
1638
1737
1836
1936
2035
2135
2234
2334
2435
2535
2635
2736
2836
2937
3038

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the dry band about 78% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
158348
259338
360328
461318
564297
665287
767276
869256
971245
1072235
1173225
1275214
1377194
1479183
1580173
1682162
1783152
1884142
1986131
2087121
2188111
2289110
2390100
2490100
2590100
269190
279190
289190
299190
309190

Wind in September

Winds average 16 km/h in September.

Across September, daily wind ranges from about 15 km/h on the calmest days to 17 km/h at its breeziest. It stays fairly steady from day to day.

05101520151015202530
Wind speed (km/h)Feels
115light breeze
215light breeze
315light breeze
415light breeze
515light breeze
615light breeze
716light breeze
816light breeze
916light breeze
1016light breeze
1116light breeze
1216light breeze
1316light breeze
1416light breeze
1516light breeze
1616light breeze
1716light breeze
1816light breeze
1916light breeze
2016light breeze
2116light breeze
2216light breeze
2316light breeze
2416light breeze
2516light breeze
2616light breeze
2716light breeze
2816light breeze
2917light breeze
3017light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 30 min at the start of September to 11 h 24 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 126 minutes over September. Sunrise moves from 5:09 AM to 6:03 AM, and sunset from 6:41 PM to 5:26 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.55:096:41
213.55:116:39
313.45:136:36
413.35:156:33
513.25:166:31
613.25:186:28
713.15:206:26
813.05:226:23
912.95:246:21
1012.95:266:18
1112.85:276:15
1212.75:296:13
1312.75:316:10
1412.65:336:08
1512.55:356:05
1612.45:376:02
1712.45:396:00
1812.35:415:57
1912.25:425:55
2012.15:445:52
2112.15:465:49
2212.05:485:47
2311.95:505:44
2411.85:525:42
2511.85:545:39
2611.75:555:36
2711.65:575:34
2811.55:595:31
2911.56:015:29
3011.46:035:26

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 2.98 kWh/m².

For context, solar energy here swings from a low near 0.44 kWh/m² to a high of 5.76 kWh/m² in June across the year — September's 2.98 kWh/m² falls in the middle.

01234151015202530
Solar energy (kWh/m²)Level
13.7Moderate
23.6Moderate
33.6Moderate
43.5Moderate
53.5Moderate
63.4Moderate
73.4Moderate
83.3Moderate
93.3Moderate
103.2Moderate
113.2Moderate
123.1Moderate
133.1Moderate
143.0Moderate
153.0Moderate
163.0Moderate
172.9Moderate
182.9Moderate
192.8Moderate
202.8Moderate
212.7Moderate
222.7Moderate
232.6Moderate
242.6Moderate
252.5Moderate
262.5Moderate
272.5Moderate
282.4Moderate
292.4Moderate
302.3Moderate
Planning a trip in September

Is September a good time to visit Koszalin?

Our two travel scores rate September for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

5.2
Sightseeing
4th-best month of the year
1.5
Beach & pool
4th-best month of the year

September is a reasonable time to visit Koszalin for sightseeing.

What to pack for Koszalin in September

From September's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In September, Koszalin sees daytime highs around 18°C and nights near 11°C. Worth packing: rain gear. About 12 days see rain.

rain gear

Sea temperature near Koszalin in September

The nearest coast averages about 16°C in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 20 km away) is warmest in August at about 19°C and coldest in February near 3°C.

The water stays below 20°C all year — cool enough that most swimmers want a wetsuit.

0°5°10°15°20°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshing
Sea temperature (°C)Comfort
Jan4Bracing
Feb3Bracing
Mar3Bracing
Apr5Bracing
May9Bracing
Jun14Bracing
Jul17Cool
Aug19Cool
Sep16Cool
Oct13Bracing
Nov9Bracing
Dec6Bracing

UV index in Koszalin in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 4 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Koszalin peaks around June 17 at about 6 (high) — sunscreen and a hat are worth it in the middle of the day. It bottoms out near December 20 at about 0 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 6 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighModerateLowJun 17UV 6Dec 20UV 0
UV index (midday)Level
Jan1Low
Feb1Low
Mar3Moderate
Apr4Moderate
May5High
Jun6High
Jul5High
Aug5High
Sep4Moderate
Oct2Low
Nov1Low
Dec0Low

Air quality in Koszalin in September

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where September falls, not just the annual average.

Air quality in Koszalin is worst in April — around 18 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (December, 8 µg/m³).

Seasonal pattern from CAMS reanalysis, scaled to Koszalin's WHO annual average of 13.7 µg/m³.

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodApr 1318 µg/m³Dec 149 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb13Moderate
Mar17Moderate
Apr18Moderate
May16Moderate
Jun16Moderate
Jul16Moderate
Aug15Moderate
Sep14Moderate
Oct11Good
Nov9Good
Dec8Good
Location & terrain

Where is Koszalin?

Koszalin sits at 54.2°N, 16.2°E, 30 m above sea level, in Poland. The nearest listed city is Białogard, 24 km away.

KołobrzegŚwidwinUstkaSłupskSzczecinekGryficeBytów

Topography around Koszalin

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Koszalin.

Within 3 km, the terrain around Koszalin has only modest variations in elevation — a maximum elevation change of 106 m around an average of 39 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 153 m; within 80 km, significant variations in elevation — a maximum elevation change of 264 m.

The land around Koszalin is covered by artificial surfaces (38%) and trees (35%) within 3 km, trees (38%), cropland (23%) and grassland (20%) within 16 km, and trees (38%), water (27%) and cropland (22%) within 80 km.

3 km
106 m
16 km
153 m
80 km
264 m
treesgrasslandcroplandartificial surfaceswaterwetland
September weather nearby: Białogard 24 km · Kołobrzeg 38 km · Świdwin 53 km · Ustka 62 km · Słupsk 63 km · Szczecinek 64 km · Gryfice 71 km · Bytów 86 km

Poland travel facts

Travel advisory
Level 1
Exercise Normal Precautions
Power plugs
Type C / E
230 V · 50 Hz
Prices
≈ 52% of US
price level, 2025
GDP per capita
$28,420
2025
Happiness
6.8 / 10
World Happiness, 2025
Safe drinking water
89%
of population, 2024
Homicide rate
0.8
per 100k, 2023
Road deaths
9.4
per 100k/yr, 2019
Income group
High
World Bank
English
Very high
EF EPI 600
Religion
Roman Catholic 71%refused to answer 21%no religion 7%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Koszalin (54.1944°, 16.1722°, elevation 30 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).