What is the weather in Chiang Mai, in one minute?
Three seasons, not two. The cool, dry season runs from November to February, the hot season is March and April, and the rainy season starts in May and runs to October. Here is the year:
Chiang Mai: Average high and low temperature, °C
Chiang Mai: Rainfall, mm
Averages 2015-2025 · Source: Open-Meteo, CHIRPS · How we measure
Read the temperature band first: it dips to its lowest in December and January and peaks in April. Then the rain line: almost nothing from December to March, then a hump from May that tops out in August and September. For one month at a glance, the Chiang Mai destination page is quicker.
Where to be next: your month-by-month route, $19
A route for your months with a leave-by date for each stop, a backup, and the seasonal traps on your path. Drafted from 11 years of weather data, every number checked against it, in your inbox within 48 hours. Not included: visas, insurance or bookings.
When is the cool season in Chiang Mai?
November to February. Highs are 29°, 27°, 27° and 30° across those months, and nights drop from 20° in November to 16° in January. Rain is minimal, 61 mm in November and under 20 mm after that, and humidity falls from 79 percent in November to 59 percent in February.
December and January are the coolest and driest. February is the warmest of the four and the first month the smoke builds. November is the gentle entry: the rains have mostly gone, with about 4 rainy days. Bring a light layer: nights of 16° feel cold after a day of 27°.
How hot is the hot season, and when does it break?
March and April: 34° and 35° highs, with nights of 21° and 23°. It is also the least humid stretch of the year, at 52 percent in March, so it is a dry, dusty heat. The first real rain comes in April (57 mm), and May is still hot, with highs of 34°, even as rain jumps to 220 mm. The heat only breaks in June, at 31°.
With air conditioning in a cafe or a coworking space the hot season is survivable. The real problem is not the temperature but the air.
What about the smoke?
February to April is burning season in the north, and it is the main reason long-stayers leave Chiang Mai in March. We keep the air figures on their own page so they are not repeated here: the Chiang Mai burning season guide has PM2.5 for the last four seasons, the worst weeks (on average 12 to 18 March and 2 to 8 April) and where to go instead.
For planning: smoke can already show up in January (in three of the four seasons we hold, a week of twice the WHO daily guideline appeared then), and by the start of May every season was back under that level. Each year is different, so treat the whole of February to April as at risk.
Where to go when Chiang Mai burns: most long-stayers head for the coast. Here is March on both coasts next to Chiang Mai; the burning season guide has the air figures.
March averages, side by side
| Place | High | Low | Rain | Rain days |
|---|---|---|---|---|
| Chiang Mai | 34° | 21° | 12 mm | 1 |
| Hua Hin | 33° | 24° | 19 mm | 2 |
| Phuket | 32° | 26° | 45 mm | 4 |
| Koh Samui | 30° | 26° | 47 mm | 2 |
Averages 2015-2025 · Source: Open-Meteo, CHIRPS · How we measure
When is the rainy season in Chiang Mai, and is it bad?
May to October. It builds in May (220 mm), then eases in June (123 mm) before the real rain of August and September, and fades through October (161 mm). Cloud is about nine tenths of the sky from June to August, humidity runs 80 to 87 percent and highs fall back to 29° to 31°.
It is not a washout: the hills turn green and the air is clean. But in August and September the rain is heavy, flooding on low roads is possible, and a month there means damp clothes and a lot of grey. If you like the quiet and the clean air, June is the easiest wet month. October is the transition: the rains are fading and the cool season is close.
Who should come when?
For a long stay, November to February. December and January are the best bet for comfort, February for warmth if you can accept the first smoke, and November for a gentle start.
Leave in March and April unless you have a plan for the air. A move to the coast or south is the practical answer; the burning season page lists where is clear. May and the rains suit those who want a green, cheap and quiet Chiang Mai. For comparisons with other Thai options, see the three coasts guide and where is warm in December.
What would we do?
Plan the year around the air as much as the rain. A circuit that keeps you in Chiang Mai from November to February and moves you to the south or the coast for March and April is the pattern that matches our numbers. Come back in May or June only if you like rain, green hills and fewer people; July to September is the wettest stretch and the part of the year to skip for a first long stay. This is a weather view only: it does not cover flights, the cost of living or internet quality, so check those before booking.
How sure are these numbers?
They are month-of-year averages for a single point near the city, from stored climate data (Open-Meteo archive and CHIRPS rain totals, 2015 to 2025), so any single year can be wetter, hotter or smokier. The hills around the city are cooler and wetter than the valley floor, and the numbers say nothing about smoke, which is modelled separately on the burning season page. A rainy day is a day with at least four millimetres of rain, which matches what rain gauges count.
Frequently asked questions
What is the best month to visit Chiang Mai?
December and January for the coolest, driest weather: highs of 27°C, nights of 16°C to 17°C and only 16 mm and 8 mm of rain. November and February are close behind.
When is the rainy season in Chiang Mai?
May to October. September is the wettest month in our data at 261 mm, with August close behind at 252 mm. October, at 161 mm, still has real rain.
How hot does Chiang Mai get?
April is the hottest month, with an average high of 35°C and nights of 23°C. March is nearly as hot at 34°C.
Is Chiang Mai cold in winter?
Not for most people. January highs are 27°C, but nights fall to 16°C, so you will want a light layer in the evening and early morning.
When is the smoky season in Chiang Mai?
February to April, with the worst weeks usually between mid-March and mid-April. It has its own page with the month-by-month air figures.
Not sure where yet? Pick your months and what to avoid, and get your 3 best places → Where should I go?
Weather data: Open-Meteo (CC BY 4.0), open-meteo.com; rain totals: CHIRPS (Climate Hazards Center, UC Santa Barbara). Processed by NomadWeather from stored copies of the data.