Dumai weather in September

In September, Dumai sees average daytime highs of 32°C and overnight lows near 24°C, with 253 mm of rain across 26.1 wet days and about 12 hours of daylight. It is the 7th-warmest and 4th-wettest month of the year here.

Day-to-day highs hold fairly steady near 32°C through the month. The sky is clear or mostly clear about 2% of the time in September, and the air most often feels miserable.

Daylight stretches from about 12 hours at the start of September to 12 hours by month's end. Set against the rest of the year, September is Dumai's 7th-clearest and 10th-windiest month. For the whole year in context, see Dumai's year-round climate.

Daytime high
32°
7th warmest
Overnight low
24°
1st coldest
Rainfall
253 mm
26.1 wet days
Daylight
12 hours
6:08 AM – 6:09 PM
Cloud cover
85%
7th clearest
Wind
5 km/h
10th windiest
Solar energy
5.18 kWh/m²
Travel score
2.5
out of 10

Dumai is city in Riau Province, Indonesia.

Density
202/km²
people per km²
Founded
1999

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

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 32°C through the month.

A typical September day in Dumai reaches about 32°C in the afternoon and slips back to 24°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 30°C and 33°C. Set against its neighbours, September runs on par with August and on par with October.

20°25°30°35°151015202530
Avg high (°C)Avg low (°C)
13224
23224
33224
43224
53224
63224
73224
83224
93224
103224
113224
123224
133224
143224
153224
163224
173224
183224
193224
203224
213224
223224
233224
243224
253224
263224
273224
283224
293224
303224

How September really feels in Dumai

Once humidity and wind are folded in, September averages 30 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
30
30 feel dangerously hot (≥ 39°C)
Days feeling ≤ C
0
wind chill below the day's low

The story in September is heat — humidity pushes the afternoon "feels like" well above the raw temperature.

Dumai weather by month

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

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan31° / 24°20121.311.93.3
Feb32° / 25°12316.811.93.2
Mar32° / 25°21725.1122.5
Apr32° / 25°24927.6122.2
May32° / 25°22426.312.12.3
Jun32° / 25°15621.312.12.7
Jul32° / 24°16220.412.13.0
Aug32° / 24°1952412.12.7
Sep32° / 24°25326.1122.5
Oct31° / 24°30828.2122.4
Nov31° / 24°38728.511.92.4
Dec31° / 24°34327.711.92.7

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 2% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 9% of September, with mostly cloudy or overcast conditions the remaining 90%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
11090
21090
31090
41189
51189
61189
71189
81288
91288
101288
111288
121288
131288
141288
151288
161189
171189
181189
191090
201090
211090
22991
23991
24991
25991
26892
27892
28892
29892
30793

Chance of precipitation in September

Any precipitation

Dumai gets around 253 mm of rain over 26.1 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 87% and peaks near 91% on the wettest days. The odds climb toward the end of the month.

0%20%40%60%80%100%151015202530
Rain chance (%)
183
283
383
484
584
684
784
885
985
1085
1185
1286
1386
1486
1586
1687
1787
1887
1988
2088
2189
2289
2389
2490
2590
2690
2790
2890
2990
3091

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the miserable band about 92% of days. Sticky, muggy-or-worse air turns up on roughly 100% of them.

0%25%50%75%100%151015202530
Oppressive (%)Miserable (%)
11189
21288
31288
41288
51189
61189
71189
81189
91189
101090
111090
121090
13991
14991
15892
16892
17793
18793
19694
20694
21694
22595
23595
24595
25595
26496
27496
28496
29496
30595

Wind in September

Winds average 5 km/h in September.

Across September, daily wind ranges from about 5 km/h on the calmest days to 5 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (km/h)Feels
15calm
25calm
35calm
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
305calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 hours at the start of September to 12 hours by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 0 minutes over September. Sunrise moves from 6:13 AM to 6:04 AM, and sunset from 6:15 PM to 6:03 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.06:136:15
212.06:136:15
312.06:126:14
412.06:126:14
512.06:126:13
612.06:116:13
712.06:116:13
812.06:116:12
912.06:116:12
1012.06:106:11
1112.06:106:11
1212.06:106:10
1312.06:096:10
1412.06:096:10
1512.06:096:09
1612.06:086:09
1712.06:086:08
1812.06:086:08
1912.06:076:08
2012.06:076:07
2112.06:076:07
2212.06:066:06
2312.06:066:06
2412.06:066:06
2512.06:056:05
2612.06:056:05
2712.06:056:04
2812.06:056:04
2912.06:046:04
3012.06:046:03

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.18 kWh/m².

For context, solar energy here swings from a low near 4.21 kWh/m² to a high of 5.49 kWh/m² in February across the year — September's 5.18 kWh/m² sits near the top of that range.

0246151015202530
Solar energy (kWh/m²)Level
15.1Bright
25.1Bright
35.1Bright
45.1Bright
55.1Bright
65.2Bright
75.2Bright
85.2Bright
95.2Bright
105.2Bright
115.2Bright
125.2Bright
135.2Bright
145.2Bright
155.2Bright
165.2Bright
175.2Bright
185.2Bright
195.2Bright
205.2Bright
215.2Bright
225.2Bright
235.2Bright
245.2Bright
255.2Bright
265.2Bright
275.1Bright
285.1Bright
295.1Bright
305.1Bright
Planning a trip in September

Is September a good time to visit Dumai?

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

2.5
Sightseeing
7th-best month of the year
3.8
Beach & pool
9th-best month of the year

September is a weaker month for outdoor sightseeing in Dumai.

What to pack for Dumai in September

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

In September, Dumai sees daytime highs around 32°C and nights near 24°C. Pack light clothes and rain gear. Worth having: sun protection. About 26 days see rain.

light clothesrain gearsun protection

Sea temperature near Dumai in September

The nearest coast averages about 30°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 48 km away) is warmest in May at about 30°C and coldest in January near 29°C.

The water stays above 20°C all year — warm enough for a swim any month.

28°30°32°JanFebMarAprMayJunJulAugSepOctNovDecwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan29Tropical
Feb29Tropical
Mar29Tropical
Apr30Tropical
May30Tropical
Jun30Tropical
Jul30Tropical
Aug30Tropical
Sep30Tropical
Oct30Tropical
Nov29Tropical
Dec29Tropical

UV index in Dumai in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 13 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Dumai peaks around February 17 at about 14 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near June 20 at about 10 (very high).

The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeVery highExtremeFeb 17UV 14Jun 20UV 10
UV index (midday)Level
Jan13Extreme
Feb14Extreme
Mar13Extreme
Apr13Extreme
May12Extreme
Jun10Very high
Jul10Extreme
Aug12Extreme
Sep13Extreme
Oct14Extreme
Nov11Extreme
Dec11Extreme

Air quality in Dumai 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 Dumai is worst in September — around 43 µg/m³ PM2.5 (poor), about 2.9× the cleanest month (December, 15 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

0204060JanFebMarAprMayJunJulAugSepOctNovDecModeratePoorModerateSep 943 µg/m³Dec 1015 µg/m³
PM2.5 (µg/m³)Level
Jan18Moderate
Feb31Moderate
Mar36Poor
Apr26Moderate
May20Moderate
Jun21Moderate
Jul37Poor
Aug42Poor
Sep43Poor
Oct30Moderate
Nov15Moderate
Dec15Moderate
Location & terrain

Where is Dumai?

Dumai sits at 1.7°N, 101.4°E, 7 m above sea level, in Indonesia. The nearest listed city is Balai Pungut, 70 km away.

Topography around Dumai

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

Within 3 km, the terrain around Dumai has only modest variations in elevation — a maximum elevation change of 27 m around an average of 5 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 53 m; within 80 km, only modest variations in elevation — a maximum elevation change of 77 m.

The land around Dumai is covered by artificial surfaces (51%) and trees (31%) within 3 km, trees (66%) and water (20%) within 16 km, and trees (64%) and water (29%) within 80 km.

3 km
27 m
16 km
53 m
80 km
77 m
treesshrubsgrasslandartificial surfacesbare terrainwatermangroves
September weather nearby: Balai Pungut 70 km · Kampung Teluk Kemang 100 km · Sungai Udang 103 km · Port Dickson 103 km · Klebang Besar 104 km · Bukit Rambai 105 km · Malacca 106 km · Kampong Masjid Tanah 107 km

Indonesia travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type C / F
230 V · 50 Hz
Prices
≈ 29% of US
price level, 2025
GDP per capita
$5,060
2025
Happiness
5.6 / 10
World Happiness, 2025
Safe drinking water
30%
of population, 2024
Homicide rate
0.3
per 100k, 2022
Road deaths
11.3
per 100k/yr, 2019
Income group
Upper middle
World Bank
English
Low
EF EPI 471
Religion
Muslim 87%Protestant 8%Roman Catholic 3%Hindu 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 Dumai (1.6671°, 101.4432°, elevation 7 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).