Bangkok's PM2.5 season: a guide for families

Short answer: from about December to March, Bangkok's air can be bad enough to close schools, so plan the season the way you'd plan for bushfire smoke at home.

The short version

Smartraveller says Thailand's air pollution can reach hazardous levels, and names Bangkok as one of the worst-affected places [1].
The haze builds in the cool, dry months, when still weather traps dust from traffic, crop burning and rubbish fires over the city [3][4].
In January 2025, more than 350 Bangkok schools closed and residents were told to work from home [3].
Thailand's safe limit for PM2.5 is 37.5 micrograms per cubic metre averaged over 24 hours. Bangkok regularly goes well past it in the dry season [2].
A well-fitted P2 or N95 mask, a HEPA purifier sized for the room and a daily AQI check do most of the work [5][6].

Why the haze happens, and when

PM2.5 means particles smaller than 2.5 micrometres, small enough to get deep into your lungs. Bangkok has them all year from traffic, but the concentration jumps in the dry season.

In January 2025, Bangkok's governor, Chadchart Sittipunt, blamed the spike on seasonal crop burning, vehicle emissions and the burning of rubbish [3]. The weather does the rest. In January 2026, the Bangkok Metropolitan Administration (BMA) warned that "stagnant weather and poor air ventilation" would trap fine dust over the city, with the worst levels at night and in the early morning [4].

Roughly how the year plays out:

Months	What to expect in Bangkok
November to December	Cool season starts. Bad days begin to appear, usually after a run of still weather
January to February	Peak haze season. Multi-day episodes, district warnings and school closures are most likely [2][3][4]
March to April	Bangkok usually eases, but northern and north-eastern Thailand get their worst haze from burning [1]
May to October	Rainy season. Air is generally much cleaner, but mosquito-borne illnesses rise [1]

The timing has a sting for Australians. If you're thinking of escaping a bad week in Bangkok with a trip to Chiang Mai in March, you may be flying into worse air [1]. And if you go home for Christmas and come back mid-January, you may land right in the middle of the season.

Reading the numbers

There are two kinds of numbers on air quality apps, and it helps to know which is which.

PM2.5 concentration is measured in micrograms per cubic metre (µg/m³). Thailand's standard is 37.5 µg/m³ over 24 hours [2]. The World Health Organization's annual guideline is far stricter: on one bad morning in January 2025, Bangkok's reading of 108 µg/m³ was 21.6 times that guideline [3].
AQI (Air Quality Index) turns pollutant readings into a single score. Global apps such as IQAir use the US AQI, where 0 to 50 is good, 101 to 150 is unhealthy for sensitive groups, 151 to 200 is unhealthy for everyone, and above 200 is very unhealthy. When Bangkok's schools closed in January 2025, the AQI had reached 159 and then 185 [3].

Thailand's own index and the BMA's colour warnings use different cut-offs, so a "yellow" Thai reading and a US-style figure won't line up exactly. Pick one source and stick with it.

Where to check

AirBKK (airbkk.com and the app) is the BMA's service. It shows readings by district and gives seven-day advance alerts [2][4].
BMA's daily haze forecast uses colours from yellow (moderate risk) to orange and red (high risk) [4].
Line Alert and the BMA Environment Department's Facebook page also post warnings [2].
IQAir and the World Air Quality Index are handy for comparing with other cities, and Smartraveller points travellers to the World Air Quality Index [1].

Pollution varies a lot between districts. In January 2025, the worst readings were in western districts such as Nong Khaem, Bang Khun Thian and Phasi Charoen [2]. On 13 February 2026, the worst were eastern and northern districts such as Nong Chok, Lat Krabang and Khlong Sam Wa, along with central Bang Rak [8]. Check your own district, not the city average.

What actually protects you

Australia's health authorities wrote the playbook for this during the Black Summer bushfires, and it applies neatly to Bangkok haze.

Masks

P2 or N95 masks filter fine particles. Surgical and cloth masks don't protect against smoke [5].
Fit is everything. The mask must seal around your face. Even one or two days of stubble can stop a good seal [5].
Kids are different. The Department of Health says children under two shouldn't wear face coverings at all [6]. Older children need properly sized masks, and many won't keep them on, so indoor air matters more for them.

Indoors

Run a HEPA air purifier in bedrooms and the main living area. Size it for the room, and replace filters on schedule. Many Bangkok families run one per bedroom through the season.
Keep doors and windows shut on bad days. Condo air-conditioners recirculate air, which helps, but they don't filter much.
Seal the gaps. Older condos and shophouses can be draughty. A purifier can't keep up if outside air pours in.
Plan exercise indoors. Move runs in Lumphini Park or Benjakitti Park to the gym on red days.

Who needs extra care

The Department of Health lists the people most at risk from fine particles: people with heart or lung conditions such as asthma, adults over 65, children aged 14 and under, pregnant women, and people with diabetes [6]. If that's anyone in your family:

See your GP before you move, and again before your first dry season.
Update the asthma or health management plan and make sure it covers smoke events [6].
Bring enough prescription medicine and keep a spare reliever puffer at school.
Ask your doctor about P2 masks for anyone in the higher-risk groups [6].
Check air quality daily from November and follow your plan when levels climb [6].

School closures and the school run

When pollution spikes, the BMA can let schools close. On 21 January 2025, 53 schools closed on the first day [2]. By 24 January, the number had passed 350 [3]. Closed schools were expected to run online classes or make up lessons on weekends [2].

International schools set their own policies. Many have indoor air filtration and rules that move recess, sport and outdoor events inside above a set AQI. Ask these questions when you're choosing a school:

What AQI level triggers indoor play, and which index do you use?
Are classrooms, the gym and the canteen filtered?
Do you switch to online learning, and how much notice do parents get?

On bad days, the city also asks employers to let staff work from home and restricts some trucks from parts of the city [3][4]. In January 2026, the BMA asked agencies and companies to allow work from home on 12 and 13 January [4].

Dengue and heat: the other seasons

Air quality isn't the only health season in Bangkok.

Dengue. Smartraveller notes that insect-borne illnesses are common in the rainy season [1]. Dengue is spread by mosquitoes that bite in the daytime, mostly early morning and late afternoon [7]. There's no vaccine that prevents a first infection, though one vaccine can help some people who've already had dengue [7]. Use repellent with DEET or picaridin, empty pot-plant saucers on your balcony, and see a doctor if you get a high fever [7].

Heat. The hot season from about March to May is tough on kids, older people and pets. Plan outdoor time for the early morning, carry water, and take heat warnings seriously. It's a wetter, more humid heat than most of Australia, and it doesn't drop much at night.

The hospitals and health insurance guide covers where to go and how to pay if someone does get sick.

A simple plan for your first dry season

October: buy purifiers and spare filters, and a box of P2 masks in the right sizes.
November: install AirBKK and set your district. Book a GP check for anyone with asthma.
December to February: check the forecast each evening, and plan the next day around it.
Bad weeks: keep kids inside, shift exercise indoors, and work from home if you can.
Escape plan: if you want a break, look south to the beaches rather than north in March and April [1].

Want to know which schools handled the last closures well, or which purifier filters are easy to find? Ask in Cooee Thailand, our Facebook group for Australians in Thailand.

Bangkok's PM2.5 season: haze, school closures and keeping your family well