Sønderborg weather in September

In September, Sønderborg sees average daytime highs of 17°C and overnight lows near 11°C, with 55 mm of rain across 10.2 wet days and about 12.5 hours of daylight. It is the 4th-warmest and 7th-wettest month of the year here.

Highs ease over the month, from about 19°C in the first days to 15°C by the end. The sky is clear or mostly clear about 16% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 36 min at the start of September to 11 h 24 min by month's end. Set against the rest of the year, September is Sønderborg's 6th-clearest and 7th-windiest month. For the whole year in context, see Sønderborg's year-round climate.

Daytime high
17°
4th warmest
Overnight low
11°
9th coldest
Rainfall
55 mm
10.2 wet days
Daylight
12 h 24 min
6:02 AM – 6:28 PM
Cloud cover
69%
6th clearest
Wind
17 km/h
7th windiest
Solar energy
2.82 kWh/m²
Travel score
5.2
out of 10

Sønderborg is town in Denmark.

Density
2,072/km²
people per km²
Founded
1256

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 15°C by the end.

A typical September day in Sønderborg reaches about 17°C in the afternoon and slips back to 11°C overnight — a 6°C spread between the day's warmth and the night's chill. On most days the high lands between 14°C and 21°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)
11913
21913
31912
41912
51912
61812
71812
81812
91812
101812
111812
121812
131712
141711
151711
161711
171711
181711
191711
201611
211611
221611
231611
241610
251610
261610
271510
281510
291510
301510

How September really feels in Sønderborg

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.

Sønderborg weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 7th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / 5611.637.60.0
Feb / 439.53.29.30.0
Mar / 4610.11.811.40.7
Apr11° / 399.30.313.82.7
May15° / 5110.3015.84.7
Jun19° / 11°6111.40175.7
Jul21° / 14°6312.1016.56.1
Aug21° / 14°6711.8014.76.1
Sep17° / 11°5510.2012.55.2
Oct12° / 5811.9010.23.1
Nov / 5111.10.68.11.1
Dec / 5611.62.170.1

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 16% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 17% of September, with mostly cloudy or overcast conditions the remaining 67%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
13565
23565
33466
43565
53565
63466
73565
83466
93466
103466
113466
123466
133367
143367
153268
163268
173367
183268
193268
203268
213169
223169
233070
243070
253169
263169
273268
283268
293268
303268

Chance of precipitation in September

Any precipitation

Sønderborg gets around 55 mm of rain over 10.2 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 34% and peaks near 38% on the wettest days.

0%10%20%30%40%50%151015202530
Rain chance (%)
138
238
337
437
537
636
736
836
935
1035
1134
1234
1333
1433
1533
1632
1732
1832
1932
2032
2132
2232
2333
2433
2534
2634
2735
2836
2936
3037

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 76% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
1623161
2633151
3643150
4663040
5663040
6663040
7682930
8692830
9692830
10702730
11712630
12722530
13742330
14762220
15772120
16782020
17791920
18811810
19821710
20821710
21831610
22831610
23851500
24851500
25861400
26861400
27871300
28871300
29881200
30881200

Wind in September

Winds average 17 km/h in September.

Across September, daily wind ranges from about 16 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
116light breeze
216light breeze
316light breeze
416light breeze
516light breeze
616light breeze
717light breeze
817light breeze
917light breeze
1017light breeze
1117light breeze
1217light breeze
1317light breeze
1417light breeze
1517light breeze
1617light breeze
1717light breeze
1817light breeze
1917light breeze
2017light breeze
2117light breeze
2217light breeze
2317light breeze
2417light breeze
2517light breeze
2617light breeze
2717light breeze
2817light breeze
2917light breeze
3017light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 36 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 132 minutes over September. Sunrise moves from 5:33 AM to 6:29 AM, and sunset from 7:08 PM to 5:51 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.65:337:08
213.55:357:05
313.45:377:03
413.45:397:00
513.35:416:57
613.25:436:55
713.15:456:52
813.05:476:50
913.05:496:47
1012.95:506:44
1112.85:526:42
1212.75:546:39
1312.75:566:36
1412.65:586:34
1512.56:006:31
1612.46:026:28
1712.46:046:26
1812.36:066:23
1912.26:086:20
2012.16:106:18
2112.16:126:15
2212.06:146:12
2311.96:156:10
2411.86:176:07
2511.86:196:04
2611.76:216:02
2711.66:235:59
2811.56:255:56
2911.46:275:54
3011.46:295:51

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 2.82 kWh/m².

For context, solar energy here swings from a low near 0.4 kWh/m² to a high of 5.62 kWh/m² in June across the year — September's 2.82 kWh/m² falls in the middle.

01234151015202530
Solar energy (kWh/m²)Level
13.5Moderate
23.5Moderate
33.4Moderate
43.4Moderate
53.3Moderate
63.3Moderate
73.2Moderate
83.2Moderate
93.1Moderate
103.1Moderate
113.0Moderate
123.0Moderate
132.9Moderate
142.9Moderate
152.8Moderate
162.8Moderate
172.8Moderate
182.7Moderate
192.6Moderate
202.6Moderate
212.6Moderate
222.5Moderate
232.5Moderate
242.4Moderate
252.4Moderate
262.3Moderate
272.3Moderate
282.2Moderate
292.2Moderate
302.1Moderate
Planning a trip in September

Is September a good time to visit Sønderborg?

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
1.3
Beach & pool
4th-best month of the year

September is a reasonable time to visit Sønderborg for sightseeing.

What to pack for Sønderborg in September

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

In September, Sønderborg sees daytime highs around 17°C and nights near 11°C. Worth packing: rain gear. About 10 days see rain.

rain gear

Sea temperature near Sønderborg 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 22 km away) is warmest in August at about 19°C and coldest in February near 2°C.

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

0°10°20°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshing
Sea temperature (°C)Comfort
Jan3Bracing
Feb2Bracing
Mar3Bracing
Apr5Bracing
May11Bracing
Jun15Cool
Jul18Cool
Aug19Cool
Sep16Cool
Oct12Bracing
Nov9Bracing
Dec4Bracing

UV index in Sønderborg 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 Sønderborg peaks around July 17 at about 5 (high) — a little sun protection helps at midday. It bottoms out near January 1 at about 0 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighModerateLowJul 17UV 5Jan 1UV 0
UV index (midday)Level
Jan0Low
Feb1Low
Mar2Moderate
Apr3Moderate
May5High
Jun5High
Jul5High
Aug5High
Sep4Moderate
Oct2Low
Nov1Low
Dec0Low
Location & terrain

Where is Sønderborg?

Sønderborg sits at 54.9°N, 9.8°E, 15 m above sea level, in Denmark. The nearest listed city is Flensburg, 26 km away.

FlensburgAabenraaHaderslevSchleswigEckernfördeSvendborgTønderOdense

Topography around Sønderborg

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

Within 3 km, the terrain around Sønderborg has only modest variations in elevation — a maximum elevation change of 66 m around an average of 13 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 92 m; within 80 km, only modest variations in elevation — a maximum elevation change of 147 m.

The land around Sønderborg is covered by water (31%), grassland (23%) and artificial surfaces (22%) within 3 km, water (39%) and cropland (34%) within 16 km, and cropland (35%) and water (33%) within 80 km.

3 km
66 m
16 km
92 m
80 km
147 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Flensburg 26 km · Aabenraa 28 km · Haderslev 42 km · Schleswig 46 km · Eckernförde 49 km · Svendborg 55 km · Tønder 59 km · Odense 66 km

Denmark travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type C / E / F / K
230 V · 50 Hz
Prices
≈ 92% of US
price level, 2025
GDP per capita
$76,970
2025
Happiness
7.5 / 10
World Happiness, 2025
Safe drinking water
100%
of population, 2024
Homicide rate
0.8
per 100k, 2023
Road deaths
3.7
per 100k/yr, 2019
Income group
High
World Bank
English
Very high
EF EPI 611
Religion
Evangelical Lutheran 71%other/none/unspecified 24%Muslim 4%

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 Sønderborg (54.909°, 9.7892°, elevation 15 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. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).