Dumbarton weather in September

In September, Dumbarton sees average daytime highs of 15°C and overnight lows near 9°C, with 101 mm of rain across 14.3 wet days and about 12.5 hours of daylight. It is the 4th-warmest and 9th-wettest month of the year here.

Highs ease over the month, from about 16°C in the first days to 14°C by the end. The sky is clear or mostly clear about 7% 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 18 min by month's end. Set against the rest of the year, September is Dumbarton's 6th-clearest and 9th-windiest month. For the whole year in context, see Dumbarton's year-round climate.

Daytime high
15°
4th warmest
Overnight low
9th coldest
Rainfall
101 mm
14.3 wet days
Daylight
12 h 30 min
5:59 AM – 6:26 PM
Cloud cover
78%
6th clearest
Wind
13 km/h
9th windiest
Solar energy
2.38 kWh/m²
Travel score
4.0
out of 10

Dumbarton is town and burgh in West Dunbartonshire, Scotland, UK.

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 16°C in the first days to 14°C by the end.

A typical September day in Dumbarton reaches about 15°C in the afternoon and slips back to 9°C overnight — a 6°C spread between the day's warmth and the night's chill. On most days the high lands between 13°C and 18°C. Set against its neighbours, September runs about 2°C cooler than August and about 3°C warmer than October.

10°15°20°151015202530
Avg high (°C)Avg low (°C)
11710
21610
31610
41610
51610
61610
71610
81610
91610
101610
111610
121610
13169
14159
15159
16159
17159
18159
19159
20159
21159
22159
23159
24159
25148
26148
27148
28148
29148
30148

How September really feels in Dumbarton

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.

Dumbarton weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / 14817.94.47.40.4
Feb / 11815.43.79.20.6
Mar / 10615.52.511.41.3
Apr11° / 8514.40.813.82.3
May14° / 8614.60.1163.5
Jun16° / 9114.7017.24.2
Jul18° / 11°10116016.74.7
Aug17° / 11°11316.9014.84.6
Sep15° / 10114.3012.54.0
Oct12° / 14216.3010.12.6
Nov / 132170.681.3
Dec / 14216.62.86.80.5

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 7% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 14% of September, with mostly cloudy or overcast conditions the remaining 79%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
12278
22080
32080
42080
52179
62179
72179
82179
92179
102278
112278
122278
132179
142278
152278
162278
172278
182278
192278
202377
212377
222278
232278
242278
252179
262179
271981
281981
292080
301981

Chance of precipitation in September

Any precipitation

Dumbarton gets around 101 mm of rain over 14.3 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 48% and peaks near 53% on the wettest days.

0%20%40%60%151015202530
Rain chance (%)
147
247
347
447
548
648
748
848
948
1048
1148
1248
1348
1447
1547
1647
1746
1846
1946
2046
2146
2247
2347
2448
2549
2650
2751
2852
2952
3053

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 89% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
183161
283161
384151
484151
584151
684151
785141
885141
986131
1086131
1187121
1289110
1389110
1490100
1590100
1690100
1790100
1890100
199190
209190
219190
229190
239190
249280
259280
269280
279370
289370
299370
309460

Wind in September

Winds average 13 km/h in September.

Across September, daily wind ranges from about 12 km/h on the calmest days to 13 km/h at its breeziest. It stays fairly steady from day to day.

05101520151015202530
Wind speed (km/h)Feels
112light breeze
212light breeze
312light breeze
412light breeze
513light breeze
613light breeze
713light breeze
813light breeze
913light breeze
1013light breeze
1113light breeze
1213light breeze
1313light breeze
1413light breeze
1513light breeze
1613light breeze
1713light breeze
1813light breeze
1913light breeze
2013light breeze
2113light breeze
2213light breeze
2313light breeze
2413light breeze
2513light breeze
2613light breeze
2713light breeze
2813light breeze
2913light breeze
3013light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 36 min at the start of September to 11 h 18 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 138 minutes over September. Sunrise moves from 5:29 AM to 6:27 AM, and sunset from 7:07 PM to 5:48 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.65:297:07
213.65:317:05
313.55:337:02
413.45:356:59
513.35:376:56
613.25:396:54
713.25:416:51
813.15:436:48
913.05:456:46
1012.95:476:43
1112.95:496:40
1212.85:516:37
1312.75:536:35
1412.65:556:32
1512.55:576:29
1612.55:596:26
1712.46:016:24
1812.36:036:21
1912.26:056:18
2012.16:076:15
2112.16:096:13
2212.06:116:10
2311.96:136:07
2411.86:156:04
2511.76:176:02
2611.76:195:59
2711.66:215:56
2811.56:235:53
2911.46:255:51
3011.36:275:48

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 2.38 kWh/m².

For context, solar energy here swings from a low near 0.34 kWh/m² to a high of 4.66 kWh/m² in May across the year — September's 2.38 kWh/m² falls in the middle.

0123151015202530
Solar energy (kWh/m²)Level
12.9Moderate
22.9Moderate
32.9Moderate
42.8Moderate
52.8Moderate
62.8Moderate
72.7Moderate
82.7Moderate
92.6Moderate
102.6Moderate
112.6Moderate
122.5Moderate
132.5Moderate
142.5Moderate
152.4Moderate
162.4Moderate
172.4Moderate
182.3Moderate
192.3Moderate
202.2Moderate
212.2Moderate
222.2Moderate
232.1Moderate
242.1Moderate
252.0Moderate
262.0Dim
271.9Dim
281.9Dim
291.9Dim
301.8Dim
Planning a trip in September

Is September a good time to visit Dumbarton?

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

4.0
Sightseeing
4th-best month of the year
0.3
Beach & pool
4th-best month of the year

September is a reasonable time to visit Dumbarton for sightseeing.

What to pack for Dumbarton in September

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

In September, Dumbarton sees daytime highs around 15°C and nights near 9°C. Pack rain gear. Worth having: a warm layer. About 14 days see rain.

rain geara warm layer

Sea temperature near Dumbarton in September

The nearest coast averages about 14°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 35 km away) is warmest in August at about 15°C and coldest in February near 7°C.

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

5°10°15°JanFebMarAprMayJunJulAugSepOctNovDecbracingcool
Sea temperature (°C)Comfort
Jan8Bracing
Feb7Bracing
Mar7Bracing
Apr8Bracing
May10Bracing
Jun13Bracing
Jul15Bracing
Aug15Cool
Sep14Bracing
Oct12Bracing
Nov11Bracing
Dec9Bracing

UV index in Dumbarton in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 3 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Dumbarton peaks around June 18 at about 5 (high) — a little sun protection helps at midday. 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 5 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighModerateLowJun 18UV 5Dec 20UV 0
UV index (midday)Level
Jan0Low
Feb1Low
Mar2Moderate
Apr3Moderate
May5Moderate
Jun5High
Jul5Moderate
Aug5Moderate
Sep3Moderate
Oct2Low
Nov1Low
Dec0Low
Location & terrain

Where is Dumbarton?

Dumbarton sits at 55.9°N, 4.6°W, 4 m above sea level, in United Kingdom. The nearest listed city is Vale of Leven, 3.0 km away.

Topography around Dumbarton

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

Within 3 km, the terrain around Dumbarton has only modest variations in elevation — a maximum elevation change of 172 m around an average of 31 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 533 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,210 m.

The land around Dumbarton is covered by grassland (30%), water (28%) and trees (25%) within 3 km, grassland (53%) and trees (23%) within 16 km, and grassland (56%) within 80 km.

3 km
172 m
16 km
533 m
80 km
1,210 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Vale of Leven 3.0 km · Erskine 9.0 km · Clydebank 11 km · Greenock 12 km · Johnstone 13 km · Renfrew 14 km · Bearsden 15 km · Paisley 15 km

United Kingdom travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type D / G / M
230 V · 50 Hz
Prices
≈ 89% of US
price level, 2025
GDP per capita
$57,602
2025
Happiness
6.7 / 10
World Happiness, 2025
Safe drinking water
100%
of population, 2024
Homicide rate
1.1
per 100k, 2021
Road deaths
3.2
per 100k/yr, 2019
Income group
High
World Bank
Religion
Christian 60%none 26%Muslim 4%other 2%

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 Dumbarton (55.9443°, -4.5706°, elevation 4 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).