Chiang Rai weather in September

In September, Chiang Rai sees average daytime highs of 30°C and overnight lows near 23°C, with 295 mm of rain across 25.1 wet days and about 12.1 hours of daylight. It is the 7th-warmest and 4th-wettest month of the year here.

Day-to-day highs hold fairly steady near 30°C through the month. The sky is clear or mostly clear about 9% of the time in September, and the air most often feels oppressive.

Daylight stretches from about 12 h 24 min at the start of September to 11 h 48 min by month's end. Set against the rest of the year, September is Chiang Rai's 9th-clearest and 12th-windiest month. For the whole year in context, see Chiang Rai's year-round climate.

Daytime high
30°
7th warmest
Overnight low
23°
9th coldest
Rainfall
295 mm
25.1 wet days
Daylight
12 h 06 min
6:12 AM – 6:18 PM
Cloud cover
80%
9th clearest
Wind
4 km/h
12th windiest
Solar energy
4.31 kWh/m²
Travel score
3.0
out of 10

Chiang Rai is city in Chiang Rai province, Thailand.

Air quality
Very high
PM2.5 37 µg/m³ · 2019
Density
1,294/km²
people per km²
Founded
1936

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 30°C through the month.

A typical September day in Chiang Rai reaches about 30°C in the afternoon and slips back to 23°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 28°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)
13024
23023
33023
43023
53023
63023
73023
83023
93023
103023
113023
123023
133023
143023
153023
163023
173023
183023
193023
203023
213023
223023
233023
243023
253023
263023
273023
283023
293023
303023

How September really feels in Chiang Rai

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.

Chiang Rai 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
Jan28° / 14°22310.97.7
Feb31° / 15°132.411.35.9
Mar33° / 18°425.111.94.1
Apr34° / 21°13211.812.43.1
May32° / 23°29222.812.92.8
Jun31° / 24°29726.213.22.5
Jul31° / 24°39828.413.12.6
Aug30° / 24°38328.812.72.6
Sep30° / 23°29525.112.13.0
Oct30° / 22°13917.811.54.4
Nov28° / 18°496.711.16.7
Dec26° / 15°273.710.88.0

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 11% of September, with mostly cloudy or overcast conditions the remaining 80%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
11090
21090
31090
41288
51288
61288
71486
81486
91486
101585
111585
121585
131684
141783
151783
161882
171981
182080
192278
202278
212476
222575
232674
242773
252971
263070
273268
283367
293565
303565

Chance of precipitation in September

Any precipitation

Chiang Rai gets around 295 mm of rain over 25.1 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 84% and peaks near 92% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%80%100%151015202530
Rain chance (%)
192
292
392
491
591
691
791
890
990
1089
1189
1288
1387
1487
1586
1685
1784
1882
1981
2080
2179
2278
2377
2476
2575
2675
2774
2874
2973
3073

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 82% of days. Sticky, muggy-or-worse air turns up on roughly 100% of them.

0%25%50%75%100%151015202530
Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1007921
2007921
3007921
4008020
5008020
6008020
7018019
8018019
9018118
10018118
11018217
12028216
13028315
14028414
15038314
16038413
17048313
18048313
19058312
20058312
21058312
22068311
23068311
24168310
2517839
2617839
2717848
2818838
2918847
3029827

Wind in September

Winds average 4 km/h in September, the calmest month.

Across September, daily wind ranges from about 4 km/h on the calmest days to 4 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (km/h)Feels
14calm
24calm
34calm
44calm
54calm
64calm
74calm
84calm
94calm
104calm
114calm
124calm
134calm
144calm
154calm
164calm
174calm
184calm
194calm
204calm
214calm
224calm
234calm
244calm
254calm
264calm
274calm
284calm
294calm
304calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 24 min at the start of September to 11 h 48 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 36 minutes over September. Sunrise moves from 6:08 AM to 6:15 AM, and sunset from 6:32 PM to 6:05 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.46:086:32
212.46:096:31
312.46:096:31
412.36:096:30
512.36:096:29
612.36:106:28
712.36:106:27
812.36:106:26
912.26:106:25
1012.26:106:24
1112.26:116:23
1212.26:116:22
1312.26:116:21
1412.26:116:20
1512.16:116:19
1612.16:126:18
1712.16:126:17
1812.16:126:16
1912.16:126:15
2012.06:126:15
2112.06:136:14
2212.06:136:13
2312.06:136:12
2412.06:136:11
2511.96:146:10
2611.96:146:09
2711.96:146:08
2811.96:146:07
2911.96:156:06
3011.86:156:05

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.31 kWh/m².

For context, solar energy here swings from a low near 4.1 kWh/m² to a high of 6.3 kWh/m² in April across the year — September's 4.31 kWh/m² falls in the middle.

012345151015202530
Solar energy (kWh/m²)Level
14.2Bright
24.2Bright
34.2Bright
44.2Bright
54.2Bright
64.2Bright
74.2Bright
84.2Bright
94.2Bright
104.3Bright
114.3Bright
124.3Bright
134.3Bright
144.3Bright
154.3Bright
164.3Bright
174.3Bright
184.3Bright
194.3Bright
204.3Bright
214.3Bright
224.4Bright
234.4Bright
244.4Bright
254.4Bright
264.4Bright
274.4Bright
284.4Bright
294.4Bright
304.4Bright
Planning a trip in September

Hazard calendar for Chiang Rai

In seasonPeak

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

Chiang Rai's monsoon runs May–September, when most of the year's rain falls.

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

Is September a good time to visit Chiang Rai?

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

3.0
Sightseeing
8th-best month of the year
4.2
Beach & pool
9th-best month of the year

September is a weaker month for outdoor sightseeing in Chiang Rai.

What to pack for Chiang Rai in September

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

In September, Chiang Rai sees daytime highs around 30°C and nights near 23°C. Pack light clothes and rain gear. About 25 days see rain.

light clothesrain gear

UV index in Chiang Rai in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 11 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Chiang Rai peaks around July 17 at about 13 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 at about 7 (high).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecVery highExtremeVery highJul 17UV 13Dec 21UV 7
UV index (midday)Level
Jan7Very high
Feb9Very high
Mar9Very high
Apr10Very high
May11Extreme
Jun13Extreme
Jul13Extreme
Aug13Extreme
Sep11Extreme
Oct10Very high
Nov8Very high
Dec7High

Air quality in Chiang Rai 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 Chiang Rai is worst in April — around 142 µg/m³ PM2.5 (unhealthy), about 12.0× the cleanest month (July, 12 µg/m³).

Seasonal pattern from CAMS reanalysis, scaled to Chiang Rai's WHO annual average of 37 µg/m³.

0306090120150JanFebMarAprMayJunJulAugSepOctNovDecModerateUnhealthyModerateGoodModerateApr 11137 µg/m³Jul 2312 µg/m³
PM2.5 (µg/m³)Level
Jan21Moderate
Feb36Poor
Mar117Unhealthy
Apr142Unhealthy
May34Moderate
Jun14Moderate
Jul12Good
Aug12Good
Sep12Moderate
Oct13Moderate
Nov14Moderate
Dec17Moderate
Location & terrain

Where is Chiang Rai?

Chiang Rai sits at 19.9°N, 99.8°E, 401 m above sea level, in Thailand. The nearest listed city is Mae Chan, 27 km away.

San Kamphaeng

Topography around Chiang Rai

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

Within 3 km, the terrain around Chiang Rai has only modest variations in elevation — a maximum elevation change of 66 m around an average of 398 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 815 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,937 m.

The land around Chiang Rai is covered by artificial surfaces (43%) and trees (36%) within 3 km, trees (52%) and cropland (33%) within 16 km, and trees (70%) and cropland (21%) within 80 km.

3 km
66 m
16 km
815 m
80 km
1,937 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Mae Chan 27 km · Ban Khoan 56 km · Mae Sai 59 km · Tachilek 60 km · Ban Houakhoua 75 km · Phayao 80 km · Dok Kham Tai 85 km · San Kamphaeng 149 km

Thailand travel facts

Travel advisory
Level 1
Exercise Normal Precautions
Power plugs
Type A / B / C
230 V · 50 Hz
Prices
≈ 31% of US
price level, 2025
GDP per capita
$8,057
2025
Happiness
6.3 / 10
World Happiness, 2025
Homicide rate
4.8
per 100k, 2011
Road deaths
32.2
per 100k/yr, 2019
Income group
Upper middle
World Bank
English
Very low
EF EPI 402
Religion
Buddhist 93%Muslim 5%Christian 1%other 1%

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 Chiang Rai (19.9086°, 99.8325°, elevation 401 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. 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).