Chilaw weather in September

In September, Chilaw sees average daytime highs of 28°C and overnight lows near 26°C, with 180 mm of rain across 24.4 wet days and about 12 hours of daylight. It is the 10th-warmest and 5th-wettest month of the year here.

Day-to-day highs hold fairly steady near 28°C through the month. The sky is clear or mostly clear about 9% of the time in September, and the air most often feels miserable.

Daylight stretches from about 12 h 06 min at the start of September to 11 h 54 min by month's end. Set against the rest of the year, September is Chilaw's 6th-clearest and 4th-windiest month. For the whole year in context, see Chilaw's year-round climate.

Daytime high
28°
10th warmest
Overnight low
26°
7th coldest
Rainfall
180 mm
24.4 wet days
Daylight
12 hours
6:04 AM – 6:06 PM
Cloud cover
76%
6th clearest
Wind
20 km/h
4th windiest
Solar energy
5.4 kWh/m²
Travel score
3.7
out of 10

Chilaw is large town in Puttalam district, Sri Lanka.

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 28°C through the month.

A typical September day in Chilaw reaches about 28°C in the afternoon and slips back to 26°C overnight — a 3°C spread between the day's warmth and the night's chill. On most days the high lands between 27°C and 29°C. Set against its neighbours, September runs on par with August and on par with October.

20°23°25°28°30°151015202530
Avg high (°C)Avg low (°C)
12826
22826
32826
42826
52826
62826
72826
82826
92826
102826
112826
122826
132826
142826
152826
162826
172826
182826
192826
202826
212826
222826
232826
242826
252826
262826
272826
282826
292826
302826

How September really feels in Chilaw

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.

Chilaw weather by month

How September compares with the rest of the year at a glance. September is the 10th-warmest and 5th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan30° / 24°376.111.65.7
Feb31° / 25°33611.85.2
Mar31° / 26°6913.711.94.4
Apr30° / 26°15224.912.23.2
May30° / 27°22128.112.33.0
Jun29° / 27°18525.812.43.4
Jul28° / 26°13322.112.44.0
Aug28° / 26°12921.912.24.1
Sep28° / 26°18024.4123.7
Oct29° / 26°29826.111.83.5
Nov29° / 25°26122.211.73.8
Dec29° / 25°13113.511.65.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 9% 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 77%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
11981
21981
31981
41981
52080
62080
72179
82278
92278
102377
112476
122476
132575
142575
152575
162575
172674
182674
192674
202575
212575
222476
232476
242476
252476
262476
272377
282476
292476
302476

Chance of precipitation in September

Any precipitation

Chilaw gets around 180 mm of rain over 24.4 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 81% and peaks near 83% on the wettest days.

0%20%40%60%80%151015202530
Rain chance (%)
177
278
378
478
579
679
779
880
980
1080
1180
1281
1381
1482
1582
1683
1783
1883
1983
2083
2183
2283
2383
2483
2582
2682
2782
2881
2981
3081

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 86% of days. Sticky, muggy-or-worse air turns up on roughly 100% of them.

0%25%50%75%100%151015202530
Oppressive (%)Miserable (%)
11486
21486
31486
41486
51486
61486
71387
81387
91387
101387
111288
121288
131288
141189
151189
161189
171189
181189
191189
201189
211288
221387
231486
241585
251684
261783
271783
281882
291981
301981

Wind in September

Winds average 20 km/h in September.

Across September, daily wind ranges from about 18 km/h on the calmest days to 21 km/h at its breeziest. It stays fairly steady from day to day.

0510152025151015202530
Wind speed (km/h)Feels
121breezy
221breezy
321breezy
421breezy
521breezy
620breezy
720breezy
820breezy
920breezy
1020breezy
1120breezy
1220breezy
1320breezy
1420breezy
1520breezy
1620breezy
1720light breeze
1820light breeze
1920light breeze
2020light breeze
2119light breeze
2219light breeze
2319light breeze
2419light breeze
2519light breeze
2618light breeze
2718light breeze
2818light breeze
2918light breeze
3018light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 06 min at the start of September to 11 h 54 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 12 minutes over September. Sunrise moves from 6:06 AM to 6:02 AM, and sunset from 6:15 PM to 5:58 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.16:066:15
212.16:066:14
312.16:066:14
412.16:066:13
512.16:066:13
612.16:056:12
712.16:056:12
812.16:056:11
912.16:056:10
1012.16:056:10
1112.16:056:09
1212.16:056:09
1312.16:046:08
1412.16:046:08
1512.06:046:07
1612.06:046:06
1712.06:046:06
1812.06:046:05
1912.06:036:05
2012.06:036:04
2112.06:036:03
2212.06:036:03
2312.06:036:02
2412.06:036:02
2512.06:036:01
2612.06:026:01
2712.06:026:00
2812.06:025:59
2911.96:025:59
3011.96:025:58

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.

For context, solar energy here swings from a low near 4.7 kWh/m² to a high of 6.51 kWh/m² in March across the year — September's 5.4 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.5Bright
25.5Bright
35.5Bright
45.5Bright
55.5Bright
65.5Bright
75.5Bright
85.5Bright
95.5Bright
105.5Bright
115.5Bright
125.5Bright
135.5Bright
145.5Bright
155.5Bright
165.4Bright
175.4Bright
185.4Bright
195.4Bright
205.4Bright
215.4Bright
225.3Bright
235.3Bright
245.3Bright
255.3Bright
265.3Bright
275.3Bright
285.3Bright
295.3Bright
305.2Bright
Planning a trip in September

Hazard calendar for Chilaw

In seasonPeak

In September, Chilaw sits inside its cyclone season. The full year is below, with each hazard's peak months called out.

Chilaw sits in the North Indian Ocean cyclone zone; the season peaks May and October–November.

Cyclone
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Chilaw?

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

3.7
Sightseeing
8th-best month of the year
4.4
Beach & pool
9th-best month of the year

September is a weaker month for outdoor sightseeing in Chilaw.

What to pack for Chilaw in September

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

In September, Chilaw sees daytime highs around 28°C and nights near 26°C. Pack light clothes and rain gear. Worth having: sun protection. About 24 days see rain.

light clothesrain gearsun protection

Sea temperature near Chilaw in September

The nearest coast averages about 28°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 April at about 30°C and coldest in August near 27°C.

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

26°28°30°32°JanFebMarAprMayJunJulAugSepOctNovDecwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan28Warm
Feb28Warm
Mar29Tropical
Apr30Tropical
May29Tropical
Jun28Tropical
Jul27Warm
Aug27Warm
Sep28Warm
Oct28Tropical
Nov29Tropical
Dec28Tropical

UV index in Chilaw 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 Chilaw peaks around April 18 at about 13 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 9 (very high).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeVery highApr 18UV 13Dec 19UV 9
UV index (midday)Level
Jan10Very high
Feb13Extreme
Mar13Extreme
Apr13Extreme
May13Extreme
Jun11Extreme
Jul12Extreme
Aug13Extreme
Sep13Extreme
Oct12Extreme
Nov10Extreme
Dec9Very high

Air quality in Chilaw 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 Chilaw is worst in March — around 30 µg/m³ PM2.5 (moderate), about 1.8× the cleanest month (August, 17 µg/m³).

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

010203040JanFebMarAprMayJunJulAugSepOctNovDecModerateMar 2030 µg/m³Aug 2417 µg/m³
PM2.5 (µg/m³)Level
Jan23Moderate
Feb23Moderate
Mar30Moderate
Apr28Moderate
May24Moderate
Jun18Moderate
Jul17Moderate
Aug17Moderate
Sep17Moderate
Oct19Moderate
Nov24Moderate
Dec23Moderate
Location & terrain

Where is Chilaw?

Chilaw sits at 7.6°N, 79.8°E, 8 m above sea level, in Sri Lanka. The nearest listed city is Negombo, 41 km away.

NegomboKatunayakaPuttalamJa ElaKandanaWelisaraKurunegalaHendala

Topography around Chilaw

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

Within 3 km, the terrain around Chilaw has only modest variations in elevation — a maximum elevation change of 15 m around an average of 3 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 67 m; within 80 km, large variations in elevation — a maximum elevation change of 977 m.

The land around Chilaw is covered by water (38%) and trees (33%) within 3 km, water (52%) and trees (39%) within 16 km, and trees (53%) and water (37%) within 80 km.

3 km
15 m
16 km
67 m
80 km
977 m
treesgrasslandcroplandartificial surfacesbare terrainwaterwetlandmangroves
September weather nearby: Negombo 41 km · Katunayaka 46 km · Puttalam 51 km · Ja Ela 57 km · Kandana 60 km · Welisara 62 km · Kurunegala 64 km · Hendala 66 km

Sri Lanka travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type D / G / M
230 V · 50 Hz
Prices
≈ 27% of US
price level, 2025
GDP per capita
$5,002
2025
Happiness
4.0 / 10
World Happiness, 2025
Safe drinking water
47%
of population, 2024
Homicide rate
3.3
per 100k, 2019
Road deaths
19.7
per 100k/yr, 2019
Income group
Upper middle
World Bank
English
Low
EF EPI 486
Religion
Buddhist 70%Hindu 13%Muslim 10%Roman Catholic 6%

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 Chilaw (7.5758°, 79.7953°, elevation 8 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. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). 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).