| Month | Mean, °C | Mean max, °C | Mean min, °C | Lowest recorded, °C | Rain, mm | Rain days | Humidity, % |
|---|---|---|---|---|---|---|---|
| January | 20.2 | 28.6 | 13.8 | 6.2 | 16.5 | 2.0 | 74 |
| February | 21.9 | 31.3 | 14.5 | 7.0 | 12.7 | 1.8 | 67 |
| March | 24.8 | 33.7 | 17.5 | 10.4 | 34.5 | 3.9 | 64 |
| April | 27.2 | 34.7 | 21.1 | 14.7 | 92.6 | 10.3 | 67 |
| May | 27.5 | 33.5 | 23.0 | 17.1 | 226.5 | 17.0 | 75 |
| June | 27.5 | 32.5 | 24.0 | 20.6 | 186.2 | 18.9 | 79 |
| July | 26.9 | 31.3 | 23.9 | 20.7 | 317.6 | 22.8 | 82 |
| August | 26.6 | 30.9 | 23.7 | 21.1 | 372.9 | 23.8 | 84 |
| September | 26.5 | 31.4 | 23.1 | 18.5 | 275.1 | 17.4 | 83 |
| October | 25.4 | 30.9 | 21.5 | 12.7 | 123.5 | 10.9 | 81 |
| November | 22.9 | 29.6 | 17.9 | 8.9 | 44.8 | 4.7 | 78 |
| December | 20.2 | 27.8 | 14.7 | 1.5 | 20.6 | 2.5 | 77 |
| Year | 24.8 | 31.4 | 19.9 | 1.5 | 1,723.5 | 136.0 | 76 |
The table above is a climate normal: averages over 30 years, not a forecast for any given year. A single year can be drier or wetter, warmer or cooler. For planning a trip, the normal is more useful than last year’s weather: it shows what to expect in a typical month.
What the numbers show
Chilly nights from December to February. The average low is 14.7 °C in December, 13.8 °C in January and 14.5 °C in February, while days reach 27.8-31.3 °C. The lowest temperatures recorded at the station in 1991-2020 were 1.5 °C in December, 6.2 °C in January and 7.0 °C in February.
Fog in the cool season. The station records fog on 28.4 days a year, most of them from October to January: 4.4 in October, 5.2 in November, 7.8 in December and 7.0 in January.
The hot season is short. Highs peak in April at 34.7 °C, after 33.7 °C in March. From May the nights get warmer and the rains begin.
The rains run from May to October. Each month gets 123.5-372.9 mm, with the most in July and August, when it rains on 23-24 days out of 31. TMD counts a rain day whenever at least 0.1 mm falls, so short showers count too. The station gets 1,723.5 mm a year, half as much again as Chiang Mai.
Sunshine: 2,412.6 hours a year, most in January (248.6 hours) and least in July (123.2).
Chiang Rai weather by season
Our grouping of the monthly TMD figures in the table above (Chiang Rai station, 1991-2020). Haze days are explained below.
| Period | Months | Mean min, °C | Mean max, °C | Rain a month, mm | Rain days a month | Days with haze a month |
|---|---|---|---|---|---|---|
| Cool and dry | November-February | 13.8-17.9 | 27.8-31.3 | 12.7-44.8 | 1.8-4.7 | 3.2-16.6 |
| Hot | March-April | 17.5-21.1 | 33.7-34.7 | 34.5-92.6 | 3.9-10.3 | 16.3-25.2 |
| Rainy | May-October | 21.5-24.0 | 30.9-33.5 | 123.5-372.9 | 10.9-23.8 | 0.1-4.2 |
The same months across the country: Thailand in November and Thailand in December.
Haze days in the TMD report
The report lists the number of days a month on which the station recorded haze. At Chiang Rai there are 82.2 such days a year, mostly from February to April, with a peak of 25.2 in March. Visibility at 07:00 is also lowest in March, 3.8 km on average.
These are weather observations, not measurements of PM2.5 or an air quality index: the TMD report has no air quality data. How to read PM2.5 and where to check it is in Chiang Mai smoke season, which also covers the PM2.5 period that the Pollution Control Department names for northern Thailand.
Chiang Rai and Chiang Mai compared
Chiang Rai is about 162 km north-east of Chiang Mai in a straight line (our calculation from the station coordinates).
| Figure | Chiang Rai (48 303) | Chiang Mai (48 327) |
|---|---|---|
| Station elevation | 388 m | 305 m |
| Mean annual temperature | 24.8 °C | 26.2 °C |
| Average low in January | 13.8 °C | 15.7 °C |
| Lowest recorded, 1991-2020 | 1.5 °C, December | 3.8 °C, December |
| Annual rainfall | 1,723.5 mm | 1,139.2 mm |
| Wettest month | August, 372.9 mm | August, 223.3 mm |
| Days with haze a year | 82.2 | 115.7 |
| Days with fog a year | 28.4 | 3.8 |
Month by month for Chiang Mai: Chiang Mai weather. Buses between the two cities: Chiang Mai to Chiang Rai and Pai.
Today’s forecast and warnings from TMD
The normals show a typical month, not the coming week. For the next seven days use the TMD 7-day forecast, which is given by region. Heavy rain and storm warnings are on the TMD warnings page.
Method and limits
- Source: Thai Meteorological Department report Climatological Data of Thailand for 30 Year Period (1991-2020), 2023 edition, printed page 3 (Chiang Rai, WMO 48 303); Chiang Mai on page 5. The report is published on a TMD subdomain
- Station: 19°57’ N, 99°52’ E, 388 m above sea level
- Period: 30 years, 1991-2020, the latest 30-year period for which TMD has published normals
- How we compiled it: figures copied from the report without recalculation. We checked monthly rainfall, rain days, haze days and sunshine against the annual values and found no discrepancies
- Lowest recorded: the report’s extreme minimum for each month over 1991-2020, a single coldest reading, not a typical night
- Rain day: at least 0.1 mm in 24 hours, counted from 07:00 to 07:00
- What is missing: air quality and PM2.5. The haze days in the report are weather observations at the station, and we do not treat them as a smoke measurement
- Next update: when TMD publishes new normals or at our April 2027 review
Getting there from Chiang Mai: Chiang Mai to Chiang Rai and Pai. Where to stay in the north: Chiang Mai travel guide.
FAQ
What is the best month for weather in Chiang Rai?
For dry, mild weather, November to February: 12.7-44.8 mm of rain a month, highs of 27.8-31.3 °C and nights of 13.8-17.9 °C. January is the sunniest month, with 248.6 hours of sunshine. Haze days rise from February (16.6) to March (25.2), so check air quality before a late-season trip.
Is it cold in Chiang Rai in winter?
Days are warm, nights are cool. In January the average low is 13.8 °C against a high of 28.6 °C. The lowest temperature recorded at the station over 1991-2020 was 1.5 °C, in December. Bring a warm layer for evenings and early mornings from December to February.
When is the rainy season in Chiang Rai?
On the 1991-2020 normals, May to October: 123.5-372.9 mm a month and 10.9-23.8 rain days. July and August are the wettest (317.6 and 372.9 mm). April is already wetter than the dry season, with 92.6 mm and 10.3 rain days.
When is the dry season in Chiang Rai?
November to March: 12.7-44.8 mm a month and 1.8-4.7 rain days on average. February is the driest with 12.7 mm, January and December follow with 16.5 and 20.6 mm.
What is the hottest month in Chiang Rai?
April has the hottest days, with an average high of 34.7 °C. By the monthly mean, May and June are the warmest, both 27.5 °C, because nights are warmer then. The highest temperature recorded at the station over 1991-2020, 42.0 °C, was in May.
What is the coolest month in Chiang Rai?
January and December share the lowest mean, 20.2 °C. January has the coolest nights, an average low of 13.8 °C; December has the lowest highs, 27.8 °C, and the record low for 1991-2020, 1.5 °C.
What is the weather like in Chiang Rai in November?
November is when the rains end: 44.8 mm and 4.7 rain days on average, about a third of October's 123.5 mm. Highs are 29.6 °C, lows 17.9 °C, humidity 78%. The station records fog on 5.2 days in November on average.
What is the weather like in Chiang Rai in December?
December is dry and cool: 20.6 mm and 2.5 rain days, a mean of 20.2 °C, highs of 27.8 °C and lows of 14.7 °C. It has the most fog days of the year at the station, 7.8, and 222.0 hours of sunshine.
When is the haze season in Chiang Rai?
In the TMD normals, days with haze cluster from February to April: 16.6 in February, 25.2 in March and 16.3 in April, against 0.1-1.5 from May to September. This is a weather observation, not a PM2.5 measurement. How to check particle levels in northern Thailand is in our page on the Chiang Mai smoke season.
Sources
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