AraiWa · Know · Weather & seasons
Burning season and air quality in Thailand
What this means
For a few months a year, air quality is the single biggest factor most visitors and new residents fail to plan around. Agricultural burning and forest fires push fine-particle (PM2.5) levels in northern Thailand to some of the worst readings in the world, and Bangkok has its own haze episodes in the cool season. If you are choosing when to visit Chiang Mai, booking a long stay, or travelling with kids, asthma or a heart condition, the calendar below matters more than the temperature forecast.
Last reviewed · AraiWa editorial
Decision helper
Quick decision
Planning the north (Chiang Mai, Chiang Rai, Pai) between February and April? Check recent PM2.5 data before booking — that window is peak burning season in most years.
What changes your plan
A sensitive traveller in the group — young children, asthma, pregnancy, heart or lung conditions — turns a hazy week from an annoyance into a reason to change region or dates.
Common mistake
Assuming the season is identical every year and either cancelling months in advance or ignoring it entirely — intensity varies a lot by year, so decide on recent data, not on last year's headlines.
Local-style move
Check an air-quality app each morning during the season the way you would check rain radar in the wet season, and shift outdoor plans to the better days.
When it happens and where it is worst
The burning season is driven by agricultural burning and forest fires across the region. It typically builds from around mid-January, peaks between February and April in the north, and eases with the first sustained rains. Northern Thailand — Chiang Mai, Chiang Rai, Mae Hong Son, Pai — sees the worst of it; during bad episodes northern cities have ranked among the most polluted in the world.
Bangkok is a different pattern: the capital's haze episodes cluster in the cool season, roughly December to February, when still air traps traffic and industrial emissions plus regional smoke. Bangkok's bad days are usually less extreme than the north's peak, but they are frequent enough to matter if you are sensitive.
How to check the actual air today
- Air4Thai is the Pollution Control Department's official monitoring network — stations across the country with PM2.5 readings.
- IQAir's app and site aggregate official and community sensors and rank cities in near real time; useful for comparing your options at a glance.
- Look at PM2.5 specifically, not the generic 'AQI weather icon' in a phone app — PM2.5 is the fine-particle measure that drives the health guidance.
- During the season, readings swing within a single day — early morning is often worse, and an afternoon breeze can halve the numbers.
What to actually do about it
- If you are flexible, the simplest fix is timing: the north outside roughly February–April is a different world.
- During hazy periods, do what locals do: N95-class masks outdoors on bad days, air purifiers indoors, and outdoor exercise moved to cleaner mornings or skipped.
- Malls, modern cafes and hotels with filtration are the practical daytime refuges during a bad stretch.
- If someone in your group is in a sensitive category, ask your accommodation whether rooms have purifiers before booking a long stay in the north during the season.
Long stays: what this means for choosing a base
If you are considering a multi-month stay, the burning season is a genuine seasonal cost of basing in the north, the same way flooding risk shapes the rainy season elsewhere. Plenty of long-stayers love Chiang Mai and simply leave for the worst weeks — building that escape window into your plan up front is easier than improvising it in March.
Season planning in Thailand has two halves — this guide and the rainy season guide cover both. If air quality intersects with a health condition, healthcare in Thailand explains how clinics and hospitals work here.
Sources & further reading
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