Mae Sai weather in September

In September, Mae Sai sees average daytime highs of 31°C and overnight lows near 23°C, with 287 mm of rain across 24.2 wet days and about 12.1 hours of daylight. It is the 5th-warmest and 4th-wettest month of the year here.

Day-to-day highs hold fairly steady near 31°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 Mae Sai's 9th-clearest and 12th-windiest month. For the whole year in context, see Mae Sai's year-round climate.

Daytime high
31°
5th warmest
Overnight low
23°
9th coldest
Rainfall
287 mm
24.2 wet days
Daylight
12 h 06 min
6:11 AM – 6:18 PM
Cloud cover
79%
9th clearest
Wind
3 km/h
12th windiest
Solar energy
4.22 kWh/m²
Travel score
3.0
out of 10

Mae Sai is subdistrict municipality in Chiang Rai province, Thailand.

Density
5,365/km²
people per km²

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 31°C through the month.

A typical September day in Mae Sai reaches about 31°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)
13124
23124
33124
43124
53124
63124
73124
83124
93124
103124
113124
123124
133124
143123
153123
163123
173123
183123
193123
203123
213123
223123
233123
243123
253123
263123
273123
283123
293123
303123

How September really feels in Mae Sai

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.

Mae Sai weather by month

How September compares with the rest of the year at a glance. September is the 5th-warmest and 4th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan27° / 14°253.410.97.9
Feb30° / 14°152.411.36.1
Mar33° / 17°395.111.94.2
Apr34° / 21°11210.712.53.2
May33° / 23°27721.3132.8
Jun32° / 24°34926.713.22.4
Jul31° / 24°45528.513.12.5
Aug31° / 24°42428.712.72.6
Sep31° / 23°28724.212.13.0
Oct30° / 22°13416.711.54.3
Nov29° / 18°476.5116.5
Dec26° / 15°314.410.87.9

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 13% of September, with mostly cloudy or overcast conditions the remaining 77%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
11189
21387
31486
41486
51585
61684
71684
81684
91882
101882
111882
121981
131981
142080
152179
162278
172278
182377
192476
202575
212674
222872
232872
243070
253169
263367
273466
283565
293763
303862

Chance of precipitation in September

Any precipitation

Mae Sai gets around 287 mm of rain over 24.2 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 90% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%80%100%151015202530
Rain chance (%)
190
290
389
489
588
688
787
886
986
1085
1185
1284
1384
1483
1583
1682
1781
1880
1979
2078
2177
2276
2375
2474
2573
2672
2771
2870
2969
3068

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
Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1006832
2006832
3006832
4006832
5006931
6006931
7007030
8007129
9017128
10017128
11017227
12017425
13027424
14027523
15027622
16037621
17037621
18047620
19047719
20047719
21057718
22057718
23057817
24067816
25067915
26068014
27177913
28177913
29178012
30188011

Wind in September

Winds average 3 km/h in September, the calmest month.

Across September, daily wind ranges from about 3 km/h on the calmest days to 3 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (km/h)Feels
13calm
23calm
33calm
43calm
53calm
63calm
73calm
83calm
93calm
103calm
113calm
123calm
133calm
143calm
153calm
163calm
173calm
183calm
193calm
203calm
213calm
223calm
233calm
243calm
253calm
263calm
273calm
283calm
293calm
303calm

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 6:33 PM to 6:05 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.46:086:33
212.46:086:32
312.46:086:31
412.46:096:30
512.36:096:29
612.36:096:28
712.36:096:27
812.36:106:26
912.36:106:25
1012.26:106:24
1112.26:106:23
1212.26:106:22
1312.26:116:21
1412.26:116:20
1512.16:116:19
1612.16:116:18
1712.16:126:17
1812.16:126:16
1912.16:126:15
2012.06:126:14
2112.06:136:13
2212.06:136:12
2312.06:136:11
2412.06:136:11
2511.96:136:10
2611.96:146:09
2711.96:146:08
2811.96:146:07
2911.96:146:06
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 4.22 kWh/m².

For context, solar energy here swings from a low near 3.91 kWh/m² to a high of 6.25 kWh/m² in April across the year — September's 4.22 kWh/m² falls in the middle.

012345151015202530
Solar energy (kWh/m²)Level
14.1Bright
24.1Bright
34.1Bright
44.1Bright
54.1Bright
64.1Bright
74.1Bright
84.1Bright
94.1Bright
104.2Bright
114.2Bright
124.2Bright
134.2Bright
144.2Bright
154.2Bright
164.2Bright
174.2Bright
184.2Bright
194.3Bright
204.3Bright
214.3Bright
224.3Bright
234.3Bright
244.3Bright
254.3Bright
264.3Bright
274.4Bright
284.4Bright
294.4Bright
304.4Bright
Planning a trip in September

Hazard calendar for Mae Sai

In seasonPeak

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

Mae Sai'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 Mae Sai?

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
4.3
Beach & pool
9th-best month of the year

September is a weaker month for outdoor sightseeing in Mae Sai.

What to pack for Mae Sai in September

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

In September, Mae Sai sees daytime highs around 31°C and nights near 23°C. Pack light clothes and rain gear. About 24 days see rain.

light clothesrain gear

UV index in Mae Sai 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 Mae Sai peaks around July 19 at about 13 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 20 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 highHighJul 19UV 13Dec 20UV 7
UV index (midday)Level
Jan7High
Feb9Very high
Mar9Very high
Apr10Very high
May11Extreme
Jun13Extreme
Jul13Extreme
Aug13Extreme
Sep11Extreme
Oct10Extreme
Nov8Very high
Dec7High

Air quality in Mae Sai 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 Mae Sai is worst in April — around 156 µg/m³ PM2.5 (very unhealthy), about 12.0× the cleanest month (July, 13 µg/m³).

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

0306090120150180JanFebMarAprMayJunJulAugSepOctNovDecModerateUnhealthyModerateApr 11150 µg/m³Jul 2313 µg/m³
PM2.5 (µg/m³)Level
Jan23Moderate
Feb40Poor
Mar128Unhealthy
Apr156Very unhealthy
May37Poor
Jun15Moderate
Jul13Moderate
Aug13Moderate
Sep13Moderate
Oct14Moderate
Nov15Moderate
Dec19Moderate
Location & terrain

Where is Mae Sai?

Mae Sai sits at 20.4°N, 99.9°E, 437 m above sea level, in Thailand. The nearest listed city is Tachilek, 2.0 km away.

Möng YawngPhayao

Topography around Mae Sai

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

Within 3 km, the terrain around Mae Sai has significant variations in elevation — a maximum elevation change of 398 m around an average of 464 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,235 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,977 m.

The land around Mae Sai is covered by trees (54%) and artificial surfaces (33%) within 3 km, trees (61%) and cropland (27%) within 16 km, and trees (81%) within 80 km.

3 km
398 m
16 km
1,235 m
80 km
1,977 m
treesgrasslandcroplandartificial surfaces
September weather nearby: Tachilek 2.0 km · Ban Khoan 24 km · Mae Chan 32 km · Chiang Rai 59 km · Ban Houakhoua 64 km · Möng Yawng 97 km · Kengtung 133 km · Phayao 138 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 Mae Sai (20.4335°, 99.8762°, elevation 437 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).