Bontang weather in September

In September, Bontang sees average daytime highs of 29°C and overnight lows near 25°C, with 130 mm of rain across 20.4 wet days and about 12 hours of daylight. It is the 5th-warmest and 11th-wettest month of the year here.

Day-to-day highs hold fairly steady near 29°C through the month. The sky is clear or mostly clear about 14% of the time in September, and the air most often feels oppressive.

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 Bontang's 2nd-clearest and 2nd-windiest month. For the whole year in context, see Bontang's year-round climate.

Daytime high
29°
5th warmest
Overnight low
25°
8th coldest
Rainfall
130 mm
20.4 wet days
Daylight
12 hours
6:04 AM – 6:04 PM
Cloud cover
71%
2nd clearest
Wind
9 km/h
2nd windiest
Solar energy
5.4 kWh/m²
Travel score
3.9
out of 10

Bontang is city in East Kalimantan Province, Indonesia.

Density
479/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 29°C through the month.

A typical September day in Bontang reaches about 29°C in the afternoon and slips back to 25°C overnight — a 4°C spread between the day's warmth and the night's chill. On most days the high lands between 28°C and 30°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)
12925
22925
32925
42925
52925
62925
72925
82925
92925
102925
112925
122925
132925
142925
152925
162925
172925
182925
192925
202925
212925
222925
232925
242925
252925
262925
272925
282925
292925
302925

How September really feels in Bontang

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
heat index over the day's high
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.

Bontang weather by month

How September compares with the rest of the year at a glance. September is the 5th-warmest and 11th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan29° / 25°20325.1123.4
Feb29° / 25°16321.9123.5
Mar29° / 25°20625.3123.4
Apr29° / 25°21426.5123.1
May29° / 25°19727123.2
Jun29° / 25°17724.8123.5
Jul29° / 25°15022.4123.9
Aug29° / 25°12420124.2
Sep29° / 25°13020.4123.9
Oct29° / 25°17625.3123.4
Nov29° / 25°22028.3122.9
Dec29° / 25°24828.9123.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 14% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 16% of September, with mostly cloudy or overcast conditions the remaining 69%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
13862
23664
33664
43664
53565
63565
73466
83367
93268
103268
113169
123169
133070
143070
152872
162971
172971
182971
192971
202971
212971
222971
232971
243070
252971
262872
272872
282773
292674
302674

Chance of precipitation in September

Any precipitation

Bontang gets around 130 mm of rain over 20.4 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 69% and peaks near 74% on the wettest days.

0%20%40%60%80%151015202530
Rain chance (%)
171
270
370
470
569
668
768
867
967
1066
1166
1265
1365
1465
1565
1665
1766
1866
1967
2067
2168
2269
2370
2470
2571
2672
2773
2873
2974
3074

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the oppressive band about 74% of days. Sticky, muggy-or-worse air turns up on roughly 100% of them.

0%25%50%75%100%151015202530
Oppressive (%)Miserable (%)
18119
28020
38020
48119
58119
68119
78119
88119
98119
108119
118020
128020
137921
147822
157723
167624
177525
187426
197228
207129
216931
226832
236733
246634
256535
266436
276337
286337
296238
306238

Wind in September

Winds average 9 km/h in September.

Across September, daily wind ranges from about 9 km/h on the calmest days to 10 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
19calm
29calm
39calm
49calm
59calm
69calm
79calm
810calm
910calm
1010calm
1110calm
1210calm
1310calm
1410calm
1510calm
1610calm
1710calm
1810calm
1910calm
2010calm
219calm
229calm
239calm
249calm
259calm
269calm
279calm
289calm
299calm
309calm

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 6:10 AM to 5:59 AM, and sunset from 6:10 PM to 5:59 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.06:106:10
212.06:096:10
312.06:096:09
412.06:096:09
512.06:086:08
612.06:086:08
712.06:086:08
812.06:076:07
912.06:076:07
1012.06:076:07
1112.06:066:06
1212.06:066:06
1312.06:056:06
1412.06:056:05
1512.06:056:05
1612.06:046:04
1712.06:046:04
1812.06:046:04
1912.06:036:03
2012.06:036:03
2112.06:036:03
2212.06:026:02
2312.06:026:02
2412.06:016:01
2512.06:016:01
2612.06:016:01
2712.06:006:00
2812.06:006:00
2912.06:006:00
3012.05:595:59

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.4 kWh/m² — the sunniest month for solar.

For context, solar energy here swings from a low near 4.42 kWh/m² to a high of 5.4 kWh/m² in September across the year — September's 5.4 kWh/m² sits near the top of that range.

0246151015202530
Solar energy (kWh/m²)Level
15.3Bright
25.3Bright
35.3Bright
45.3Bright
55.3Bright
65.3Bright
75.3Bright
85.3Bright
95.3Bright
105.3Bright
115.4Bright
125.4Bright
135.4Bright
145.4Bright
155.4Bright
165.4Bright
175.4Bright
185.4Bright
195.4Bright
205.4Bright
215.4Bright
225.4Bright
235.4Bright
245.4Bright
255.4Bright
265.4Bright
275.4Bright
285.4Bright
295.3Bright
305.3Bright
Planning a trip in September

Is September a good time to visit Bontang?

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

3.9
Sightseeing
2nd-best month of the year
5.1
Beach & pool
2nd-best month of the year

September is a weaker month for outdoor sightseeing in Bontang.

What to pack for Bontang in September

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

In September, Bontang sees daytime highs around 29°C and nights near 25°C. Pack light clothes and rain gear. Worth having: sun protection. About 20 days see rain.

light clothesrain gearsun protection

Sea temperature near Bontang in September

The nearest coast averages about 29°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 16 km away) is warmest in May at about 30°C and coldest in February near 29°C.

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

28°30°JanFebMarAprMayJunJulAugSepOctNovDecwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan29Tropical
Feb29Tropical
Mar29Tropical
Apr29Tropical
May30Tropical
Jun29Tropical
Jul29Tropical
Aug29Tropical
Sep29Tropical
Oct29Tropical
Nov29Tropical
Dec29Tropical

UV index in Bontang 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 Bontang peaks around March 12 at about 15 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near July 11 at about 11 (extreme).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeMar 12UV 15Jul 11UV 11
UV index (midday)Level
Jan14Extreme
Feb15Extreme
Mar16Extreme
Apr15Extreme
May13Extreme
Jun11Extreme
Jul11Extreme
Aug12Extreme
Sep13Extreme
Oct13Extreme
Nov13Extreme
Dec12Extreme

Air quality in Bontang 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 Bontang is worst in September — around 18 µg/m³ PM2.5 (moderate), about 2.0× the cleanest month (January, 9 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodSep 2218 µg/m³Jan 229 µg/m³
PM2.5 (µg/m³)Level
Jan9Good
Feb9Good
Mar9Good
Apr11Good
May10Good
Jun12Good
Jul12Good
Aug14Moderate
Sep18Moderate
Oct17Moderate
Nov12Good
Dec11Good
Location & terrain

Where is Bontang?

Bontang sits at 0.1°N, 117.5°E, 10 m above sea level, in Indonesia. The nearest listed city is Samarinda, 79 km away.

PaluTanjung SelorMuara TewehTanjungTarakan

Topography around Bontang

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

Within 3 km, the terrain around Bontang has only modest variations in elevation — a maximum elevation change of 61 m around an average of 10 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 323 m; within 80 km, large variations in elevation — a maximum elevation change of 613 m.

The land around Bontang is covered by artificial surfaces (35%), trees (25%) and mangroves (25%) within 3 km, trees (43%) and water (41%) within 16 km, and trees (57%) and water (34%) within 80 km.

3 km
61 m
16 km
323 m
80 km
613 m
treesgrasslandcroplandartificial surfacesbare terrainwatermangroves
September weather nearby: Samarinda 79 km · Loa Janan 91 km · Balikpapan 172 km · Palu 289 km · Tanjung Selor 301 km · Muara Teweh 312 km · Tanjung 345 km · Tarakan 354 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 Bontang (0.1324°, 117.4854°, elevation 10 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).