Air pollution, floods and the hot season in Bangkok: living with the city's three weathers

Forget "it's a bit grey out". Bangkok gives you smoky haze, tropical downpours and 40°C heat, often in the same year. None of it is a reason not to move, but it pays to plan round it.

The short version

• Bangkok has high levels of air pollution and is hit by seasonal smoke haze from burning crops, which the FCDO says can reach dangerous levels [1].
• Thailand's official air quality site, Air4Thai, runs a five-band index; above 100 (PM2.5 over 37.5 micrograms per cubic metre over 24 hours) air starts to affect health [3].
• The rainy season runs from about mid-May to mid-October, with flash floods and transport disruption [2][4].
• The hot season runs from about mid-February to mid-May, and 35–39°C counts as "hot" in Thai weather terms [4].
• Many Brits time their trip home for the worst of the haze or the April heat, and keep a HEPA purifier running in the bedroom.

Thailand's seasons at a glance

Thailand has three official seasons, and none of them is anything like an English spring [4].

That "cool" season is cool only by Thai standards: Thai winter categories are based on daily minimum temperatures, and anything from 16°C to 22.9°C counts as "cool" [4]. Bring a light jumper for the air-conditioning, not for the weather.

PM2.5 and the haze season

What the FCDO says

When we checked on 8 November 2026, the FCDO's health page for Thailand (updated 12 October 2026, with the travel advice still current at 7 November 2026) said there can be high levels of air pollution in large cities, including Bangkok and Chiang Mai, which are also affected by seasonal regional smoke haze caused by farmers burning trees and crops [1][2]. It warns that pollution can sometimes reach dangerous levels and may worsen bronchial, sinus or asthma conditions [1].

The worst of it usually lands in the dry months at the start of the year, when there's little rain to clear the air and burning is at its height. Some years are much worse than others, so watch the numbers rather than the calendar.

Reading the Thai air quality index

The Pollution Control Department's Air4Thai site and app is the official source. It reports a single air quality index from six pollutants, and PM2.5, the fine dust that gets deep into your lungs, is usually the one that matters in Bangkok [3]. An index of 100 equals Thailand's air quality standard; above 100, it starts to affect health [3].

Source: Air4Thai [3].

One catch: the Thai index isn't the same as the US-style index many international apps show, so the same air can give two different numbers. Stick to one source and learn its colours. The FCDO also points to the World Air Quality Index website for checking cities [1].

What Brits in Bangkok actually do

1. Buy a HEPA air purifier for the bedroom, and a second for the living room if you have children. Run it with windows shut on bad days.
2. Keep proper masks in the flat. Air4Thai's advice is a PM2.5 mask, not a cloth one [3]. N95 or KN95 types are easy to buy in pharmacies.
3. Move exercise indoors when the index tips into orange. Your 5 km (3 mile) run in Lumphini Park can wait.
4. Ask your landlord about the seals on windows and doors. Older condos leak air like a sieve.
5. Check your health insurance. Thailand has no reciprocal healthcare agreement with the UK [5], so asthma flare-ups are paid for by you or your insurer. Our healthcare in Bangkok guide covers cover.

If you have young children, asthma or a heart or lung condition, take the haze season seriously and talk to your doctor before you move.

Rainy season and floods

The FCDO says the rainy season is generally from May to October, but weather patterns have become increasingly unpredictable and intense rain can hit at any time [2]. Heavy rainfall can cause flash flooding and disruption to transport, and conditions can change quickly, closing roads [2]. Its advice is to follow local authority instructions and watch the Thai Meteorological Department's warnings [2].

What that looks like day to day in Bangkok:

• Short, violent storms, often in the late afternoon. An hour of rain can leave sois ankle- or knee-deep, then it drains away by bedtime.
• Taxis disappear and ride-hailing prices jump. The BTS and MRT keep running and are the way home; see our guide to driving and getting around Bangkok.
• Ground-floor living is a gamble. If you're renting, ask neighbours how high the water came last year, and look at whether the car park floods. Our renting in Bangkok guide has more.
• Dengue season too. The FCDO lists dengue among Thailand's health risks [1], and standing water after rain is where mosquitoes breed. Repellent and screens are your friends.

Bangkok sits low on the Chao Phraya delta, and older readers will remember the great flood of 2011, when water reached parts of the city for weeks. Big floods like that are rare, but flash flooding in the rainy season is normal. Keep important documents up off the floor and photographed, and check your contents insurance covers flood.

The hot season

Thai weather terms class daily highs of 35–39°C as hot and 40°C and above as the hottest [4]. In late April 2024, for example, Bangkok and nearby provinces saw highs of about 35–42°C, with the heat expected to ease only once the rains came [6]. Humidity makes it feel worse.

For Brits used to a "heatwave" meaning 30°C and a hosepipe ban, this takes adjusting to:

• Drink more than you think. Water, electrolytes, and go easy on the afternoon pints.
• Plan outdoor jobs for early morning. The streets are busy at 7am for a reason.
• Budget for air-conditioning. Your electricity bill in April can be eye-watering compared with the cool season.
• Watch older relatives and pets. Heat hits the very young and old hardest.

April is also Songkran, Thai New Year, when the whole city has a water fight. It's great fun and, frankly, the best way to cool down.

When to be away

If you have the flexibility, here's how many British families plan the year:

A Christmas back home dodges nothing much, sadly. If you can only manage one trip, a haze-season break early in the year or a long UK summer are the popular choices. Keep an eye on the Statutory Residence Test if your UK days start to pile up.

Swapping tips on the best purifiers or which sois flood? Ask in our community group for Brits in Thailand.

Sources

1. GOV.UK (FCDO): Thailand travel advice, health (updated 12 October 2026)
2. GOV.UK (FCDO): Thailand travel advice, safety and security (updated 12 October 2026; still current at 7 November 2026)
3. Pollution Control Department, Air4Thai: air quality index information (in Thai, checked November 2026)
4. Thailand.go.th: The seasons of Thailand
5. GOV.UK (FCDO): Living in Thailand (last updated 11 December 2025)
6. Bangkok Post: High temperatures to linger until end of April (April 2024)

Keep reading

• Healthcare and health insurance in Bangkok
• Renting in Bangkok
• Cost of living in Bangkok vs London and the UK average
• The emotional move