CHIANG RAI – The sky above Chiang Rai tells the story at a glance. On the final day of March 2026, a heavy gray haze hangs over the city. The smoke stings the eyes, irritates the throat, and carries one of the biggest health risks northern Thailand faces each year, PM2.5.
This is not a routine smoky day. Right now, the region is at the height of a serious air pollution emergency.
Air quality across Chiang Rai and Chiang Mai has remained deep in the “Unhealthy” and “Very Unhealthy” AQI ranges through most of the last week of March.
In Nang Lae Subdistrict, Mueang District, the AQI climbed to 313 on March 27. That level falls into the “Very Unhealthy” category, where even short periods outdoors can affect the general public. Then, between March 28 and 29, AQI readings in Chiang Rai’s Mueang district stayed around 158 to 176. At the same time, Chiang Mai recorded readings of roughly 152 to 164, with some southern and mountain areas seeing even higher spikes.
For comparison, the World Health Organization (WHO) sets the safe daily PM2.5 level at 15 micrograms per cubic meter (µg/m³). This week, parts of Chiang Rai measured 68 to 81 µg/m³, which is more than four times the guideline. In past years, Chiang Rai has seen March averages above 100 µg/m³, and 2026 appears to be following the same harsh trend.
Wildfires Are Pushing the Haze Higher
The cause of the smoke is clear. Large fires are burning across the mountains and valleys in both provinces, and they continue to feed the haze.
In Chiang Rai, wildfires have burned through land near Doi Pha Ngom and in several districts. Dry brush, high heat, and shifting winds have helped the flames spread. People living near the fire zones say the smell of smoke has barely lifted. In some affected areas, schools have told students to stay indoors during breaks and wear masks when they must go outside.
At the same time, March temperatures have reached 40 degrees Celsius. That mix of extreme heat and polluted air raises the danger for almost everyone, not only those with existing health problems.
Since January 1, 2026, Chiang Rai has recorded 967 fire hotspots. That total shows just how severe this burning season has become, even with current control measures in place.
Chiang Mai has hundreds of hotspots in one day.
Chiang Mai is dealing with a crisis that is just as bad, and in some places even worse. On one day in late March, officials reported 480 active fire hotspots across the province. Many of them were found in southern districts and around famous mountain areas. By comparison, nearby Mae Hong Son recorded 247 hotspots during the same period.
Thick smoke has drifted down from the surrounding hills and settled over Chiang Mai city. The basin geography only adds to the problem. The mountains trap the smoke overhead, holding it in place above the people below. Views of temples, markets, and the mountains themselves have disappeared behind a dense wall of haze.
In response, disaster teams have sent out a KA-32 helicopter for water-drop missions over active fire zones. Even so, crews still face major challenges because many fires are burning in steep and hard-to-reach mountain areas.
Why PM2.5 Is So Harmful
Most people know smoking is unhealthy. PM2.5, however, brings a more serious risk.
PM2.5 means tiny airborne particles that measure 2.5 micrometers or smaller. That is about 30 times thinner than a human hair. Because the particles are so small, your nose and throat cannot block them well. They move deep into the lungs, and the smallest particles can pass into the bloodstream.
Right now, PM2.5 in northern Thailand is coming from several sources:
- Forest fires and wildfires, which are the main source this season
- Slash-and-burn farming, often used before rainy-season planting
- Crop waste burning, where leftover plant matter is burned in fields
- Cross-border haze, with smoke drifting in from nearby countries
- Vehicle emissions, which add to pollution all year round
Once these particles enter the body, they can trigger both short-term and long-term health problems.
Health Effects: What This Air Can Do to You
Short-term symptoms that many people already notice
Across Chiang Rai and Chiang Mai, many residents have already reported symptoms like these this week:
- Burning, itchy, or watery eyes
- A sore throat and dry cough
- A blocked or runny nose
- Frequent sneezing
- Headaches and unusual tiredness
- Shortness of breath or chest tightness
- Dizziness or nausea after spending time outside
These signs matter. They are your body’s way of reacting to polluted air.
Long-term risks from repeated exposure
Public health research, including data referenced by IQAir for Chiang Rai, shows that long-term exposure to PM2.5 at current levels can lead to serious illness, such as:
- A higher risk of asthma attacks and worse COPD (Chronic Obstructive Pulmonary Disease)
- Lower lung function, especially in children
- Greater risk of heart disease and heart attacks
- A higher cancer risk linked to black carbon, a dangerous form of PM2.5 from biomass burning
- A shorter life expectancy, with one study estimating that PM2.5 pollution in Chiang Rai cuts average lifespan by 3.7 years
People at highest risk
Some groups face a much greater threat from PM2.5 and should take extra care right away:
- Children, because their lungs are still growing, and they breathe faster
- Older adults, because the heart and lungs may already be weaker
- Pregnant women, because exposure can affect both the mother and the baby
- People with asthma or COPD, because symptoms can worsen fast
- People with heart disease, because PM2.5 puts extra strain on the heart
- Anyone with a chronic illness, because the body has less room to cope with added stress
What To Do Now To Stay Safe
The Chiang Rai Provincial Disaster Prevention and Mitigation Office (PDPMO) has already warned residents. Health agencies across the north are giving similar advice.
At home
- Keep doors and windows shut, especially in the morning and evening when smoke often sits lower.r
- Use a HEPA air purifier in the rooms where you spend the most time, especially bedrooms.
- Don’t use fans that pull air in from outside
- Drink water often, because it helps your body handle exposure better
When you need to go outside
- Wear an N95 or KN95 mask every time you go outdoors, because regular surgical masks do not block PM2.5 well
- Keep outdoor time as short as possible.le
- Avoid outdoor exercise, since running, cycling, and sports make you breathe in much more polluted air.
- Check live AQI updates before leaving home with tools like AirVisual (IQAir) or Thailand’s Pollution Control Department website.e
For higher-risk groups
- Children should stay out of outdoor play while pollution remains this high
- Older adults and people with chronic illnesses should stay indoors as much as they can and keep medicines close by
- Pregnant women should avoid unnecessary trips outside
If symptoms get worse
- Get medical care quickly if you have ongoing coughing, chest pain, heart palpitations, severe breathing trouble, dizziness, or vision issues.
- Don’t wait for symptoms to fade on their own, because PM2.5-related problems can worsen fast
Officials Are Responding, But This Goes Beyond One Province
Authorities have stepped up efforts to control fires and cut down on burning. Teams are using satellite tracking to monitor hotspots in real time. Police and forestry staff have also increased patrols. Under Thai law, anyone who starts a fire in a protected state forest can face fines from 400,000 to 2 million baht and prison terms of 4 to 20 years.
Still, enforcement remains difficult in remote mountain areas. Many experts say northern Thailand needs deeper, long-term fixes. That includes stronger support for farmers who still rely on slash-and-burn methods, more investment in cleaner land-clearing tools, reforestation programs, and closer cooperation with neighboring countries whose fires add to the haze.
Meanwhile, local communities are trying to help. Some residents are sharing air purifiers with neighbors. Volunteer groups are helping watch fire zones, including with drones. At the same time, outdoor businesses are seeing fewer visitors, while demand for N95 masks and air purifiers keeps rising across the province.
When Conditions in Chiang Rai Might Improve
Health officials and weather experts expect one main turning point, the arrival of seasonal rain. In most years, that comes in April or May. In drier years, real relief may not arrive until later in May or even June.
Until then, air quality is likely to stay dangerous on many days, although conditions may shift depending on wind and temperature. The Pollution Control Department is urging people across northern Thailand to watch daily updates and change their plans when needed.
This problem won’t fade without action. Authorities need to keep pressure on fire control, farmers need better options, and residents need to avoid adding new smoke to an already dangerous sky.
Stay informed with these resources
- Thailand Pollution Control Department: air4thai.com
- IQAir Real-Time AQI: iqair.com/thailand/chiang-rai
- AirVisual App: Available on iOS and Android
- Chiang Rai Times Air Quality Updates: chiangraitimes.com
The Chiang Rai Times will continue sharing daily air quality reports throughout the burning season. If you see wildfire activity, report it right away to local officials or the national fire hotline.
