Haze and air quality in Southeast Asia — causes, timing and health advice
Southeast Asian haze from forest fires affects millions. When it happens, which countries are hit, health risks, and how to check real-time air quality.
What causes the haze?
The transboundary haze crisis in Southeast Asia is caused primarily by deliberate burning of forests and peatlands in Sumatra and Kalimantan (Indonesian Borneo) to clear land for palm oil, pulpwood and agriculture. When peat — a dense organic soil up to 10 metres deep — catches fire, it burns slowly for weeks and produces vast quantities of fine particulate matter (PM2.5) that is transported by prevailing winds across the region. During bad years, the smoke plume can be seen from space and affects air quality in Indonesia, Singapore, Malaysia, Brunei and southern Thailand.
When does haze season occur?
Haze season typically runs from August to October, coinciding with the dry season in Sumatra and Kalimantan when fire risk is highest. The worst years align with El Niño events, which bring extended drought to Indonesia and make fires harder to control. Notable haze crises occurred in 1997, 2006, 2013, 2015 and 2019 — all El Niño or dry years. The 2015 event was one of the worst environmental disasters in Southeast Asian history, affecting over 40 million people and causing an estimated $16 billion in economic losses.
Which countries are affected?
Singapore, Malaysia (especially Peninsular Malaysia and Sarawak) and Brunei are the most consistently affected by transboundary haze from Indonesia. Southern Thailand occasionally sees haze drift northward. Northern Thailand, Laos and Myanmar have their OWN haze problem from March to April caused by local agricultural burning (slash-and-burn farming and crop residue burning), which produces severe air quality episodes independent of the Indonesian fires.
Health risks
The main health concern is fine particulate matter (PM2.5) — microscopic particles that penetrate deep into the lungs and enter the bloodstream. Short-term exposure causes eye irritation, coughing, shortness of breath and aggravated asthma. Prolonged exposure during severe haze events has been linked to respiratory infections, cardiovascular events and, over years, increased cancer risk. Children, elderly people and those with pre-existing respiratory or cardiac conditions are most vulnerable. During the 2015 crisis, hospitals across the region reported surges in emergency respiratory cases.
How to check air quality
Real-time air quality monitoring is available from multiple sources. Singapore's National Environment Agency (NEA) publishes hourly PSI and PM2.5 readings. Malaysia's Department of Environment publishes the Air Pollutant Index (API). The global standard is IQAir (iqair.com) and the World Air Quality Index (waqi.info), which aggregate readings from government and independent monitoring stations across the region. Our city weather pages on Mausam Online include European AQI readings with PM2.5 and PM10 data, updated hourly.
Travel advice during haze
Check the AQI forecast before booking trips to Singapore, Malaysia or Indonesian cities from August to October. If haze is forecast, consider N95 respirator masks (standard surgical masks do NOT filter PM2.5). Limit outdoor exercise during PSI readings above 100. If you have respiratory conditions, consult your doctor about travelling during haze season. Airlines generally continue operating during haze events, but visibility can cause delays. Some outdoor attractions (rooftop bars, outdoor pools, nature walks) lose their appeal when haze is heavy.
Frequently Asked Questions
Is the haze getting better or worse? ▾
There has been some improvement since Indonesia strengthened anti-burning laws after 2015, and 2016–2022 saw fewer extreme events. However, the problem is far from solved — dry El Niño years still produce significant haze, and enforcement remains inconsistent in remote areas.
Can you see the haze from inside a hotel? ▾
During severe episodes, yes — views from high-rise hotels in Singapore or KL become completely obscured, and a acrid smell penetrates indoors. Modern hotels with good air conditioning and air filtration provide adequate indoor air quality.
When is air quality worst in northern Thailand? ▾
March and April — the burning season for agricultural waste in northern Thailand, Laos and Myanmar. Chiang Mai regularly records some of the worst air quality in the world during these months, often exceeding AQI 200 (very unhealthy).