Chiang Mai was ranked the most polluted major city in the world on Monday 30 March, as forest and man-made fires pushed air quality to hazardous levels across the northern province. Swiss air monitoring firm IQAir reported an Air Quality Index (AQI) of 263 at 10am, classified as “very unhealthy”, with PM2.5 levels measured at 188.0 microgrammes per cubic metre. The pollution level far exceeded that of Delhi, the second most polluted city, which recorded an AQI of 198 and PM2.5 at 122.0.

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The severe smog was forecast to persist until around 4pm on Monday before gradually improving through the rest of the day and continuing to ease until at least Wednesday. Authorities linked the pollution to a surge in fire hotspots, driven by seasonal bushfires, agricultural burning, and deliberate fire-setting. On Sunday, Chiang Mai recorded 480 hotspots, nearly double the 247 detected in neighbouring Mae Hong Son, according to the Department of National Parks, Wildlife and Plant Conservation.

Despite repeated legal warnings, the number of hotspots has remained high. Department director-general Atthaphon Charoenchansa said on Sunday that the situation was worrying and reiterated strict penalties for offenders. Starting a fire in a state-protected area can result in fines ranging from 400,000 to 2 million baht and prison sentences of four to 20 years.

The Environmental and Pollution Control Office in Chiang Mai warned residents in at least 12 areas of the province and three neighbouring provinces about dangerous accumulations of fine particulate matter. The warning highlighted the health risks posed by prolonged exposure to PM2.5 pollution, particularly for vulnerable groups. Officials have urged the public to take precautions while enforcement efforts continue against illegal burning.

The Bangkokpost reported that authorities expect air quality to improve in the short term as weather conditions change, but the persistence of hotspots suggests the broader problem may continue. Efforts to control fires and enforce regulations are likely to intensify as officials attempt to reduce pollution levels and limit further environmental damage.

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Adapted by ASEAN Now Bangkokpost 31 Mar 2026

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Same as every year

But I have a filter in my room.

I don't know how y'all handle that every year. I get frustrated when it's in the 50-100 moderate range like it is now, AQI 66 & 17 µg/m³ , along the western Gulf coast.

I thought Udon Thani was bad enough, hitting 100 a wee bit too much, and major reason why I left for PKK.

1 hour ago, blaze master said:

But I have a filter in my room.

Just the one room?

That hillside is less than 5 kms away, and you can't even see it.

Fa Ham Webcams · Chiang Mai · 310 m Coordinates DD 18.811100, 98.995160

https://www.outdooractive.com/en/webcam/fa-ham/810532873/

1 hour ago, KhunLA said:

That hillside is less than 5 kms away, and you can't even see it.

That hillside is Doi Suthep and it’s always socketed in with smoke this time of year. It’s easily forgotten about until it clears up.

2 minutes ago, novacova said:

That hillside is Doi Suthep and it’s always socketed in with smoke this time of year. It’s easily forgotten about until it clears up.

We have the 2 headlands to the N & S of the bay, Ao Prachuap, then the Wat atop one outcropping center of the bay front, ~5 kms away. If I couldn't see them every morning from the veranda, that would be depressing. Then the hills to the west, < 10 kms away

To see a wall of grey would bum me out, not to mention, thinking about what it's doing to my lungs when out walking the dog, or wife in the Greenhouse & garden for hours.

And photo bug that I am, the pollution kills any landscape snaps, even operating my done, unless close up or looking downward.

The Wat & headlands are my AQI meter when I wake up, as just seeing them, or if blurred, I can tell what the AQI is. PM2.5 meter indoors, tells me the air purifiers are working great, as always in low single digits.

9 minutes ago, KhunLA said:

We have the 2 headlands to the N & S of the bay, Ao Prachuap, then the Wat atop one outcropping center of the bay front, ~5 kms away. If I couldn't see them every morning from the veranda, that would be depressing. Then the hills to the west, < 10 kms away

To see a wall of grey would bum me out, not to mention, thinking about what it's doing to my lungs when out walking the dog, or wife in the Greenhouse & garden for hours.

And photo bug that I am, the pollution kills any landscape snaps, even operating my done, unless close up or looking downward.

The Wat & headlands are my AQI meter when I wake up, as just seeing them, or if blurred, I can tell what the AQI is. PM2.5 meter indoors, tells me the air purifiers are working great, as always in low single digits.

That’s a really nice setting you have there, looks pleasant.

👏👏👏👏finally no1 in something. It’s been a while since Thailand was no1 in something.

3 minutes ago, novacova said:

That’s a really nice setting you have there, looks pleasant.

Yea, works for us. House is rural, but 5-10 minutes from everything we need. Why I describe it as semi rural. Prefer no immediate neighbors, peacefully quiet.

Same when living at Udon Thani, but pollution was very noticeable up there. If the headlands are blurring, then I know I'm hanging indoors & trolling AN more than usual. Good day to bake bread. Thankfully air is only iffy a couple months a year.

Fortunately this AQI condition is measured in weeks, not months. Every year the purifier comes out for a few weeks and is then put away.

It is horrible, no argument there. But if you are not a tourist and you don't work outdoors, the situation will pass in a short bit of time and you are not likely to be harmed by this air if you stay indoors most of the time and use a basic purifier -- 15-30 minutes of this high AQI will not cause any harm.

I'm certainly not trying to justify or make excuses, but forest fires are not easy to control -- whether in Thailand, Canada or the US. Intentional burning MUST STOP, but no government has shown the will to enforce the laws that are passed.

And it is not only Thailand, in Chiang Mai the condition is worsened by Myanmar, Laos, China and mountain hill-tribe burning -- and even the local Thai farmers will burn if they think they can get away with it.

I've seen this "smog" in Los Angeles, Denver, Mexico City and elsewhere. It can be fixed, but it will take time, and the will-power and conviction of weak politicians who would rather pay cash for votes than actually make social improvements.

4 hours ago, K2938 said:

Same as every year

How many have been fined or imprisoned, if they dont enforce the law where is the point in making them?.

Grab your elephant pants and Bob Marley shirt and let's go tubing in Pai!

Last week they lit a number of forest fires in Samoeng all around the same time and they probably did the same in other regions across northern Thailand. That's why the smoke suddenly exploded.

This is 100% coordinated and targeted, happens every year in predictable locations yet no serious efforts are ever made to stop it. It would be hard and involve serious detective work then handing down life altering sentences.

And the band played on.....

Well, that's deeply embarrassing. Too bad the bigwigs who have the power ro do something aren't easily embarrassed.

Not difficult to fix, just remove any benefit to starting a fire.

No crop permitted to be grown on any satellite identified fire area that year.

Make the mushrooms they seek illegal to be sold and offer a big reward to anyone snitching on someone selling them.

2 hours ago, KhunLA said:

That hillside is less than 5 kms away, and you can't even see it.

Fa Ham Webcams · Chiang Mai · 310 m Coordinates DD 18.811100, 98.995160

https://www.outdooractive.com/en/webcam/fa-ham/810532873/

That photo says it all!

Up until a week ago, Chiang Mai air quality was better than most cities in Thailand. The city of Phimai has consistently been far worse at least 12 hours a day, without forest fires. No mention it it from the government, as there are few tourists. Then the forest fiees started near Chaing Mai. Only then is it in the calulations. Too bad the gov only cares about the high

tourist areas.

7 hours ago, Georgealbert said:

Department director-general Atthaphon Charoenchansa said on Sunday that the situation was worrying and reiterated strict penalties for offenders. Starting a fire in a state-protected area can result in fines ranging from 400,000 to 2 million baht and prison sentences of four to 20 years.

April's fools day is tomorrow

Number One - yay! Way to go Chiang Mai!

2 hours ago, NorthernRyland said:

Grab your elephant pants and Bob Marley shirt and let's go tubing in Pai!

I wonder what a lot of the newly arrived DTVs who headed to Chiang Mai are thinking about their choice now. And the accompanying really hot weather hasn't even hit yet.

I recall a few months ago, the friendly politicians promised that the annual toxic pollution would be dealt with before it started....

Is there one with integrity ever?

If you want to see where all the current fires exist:

https://firms.modaps.eosdis.nasa.gov/map/

8 hours ago, JBChiangRai said:

Not difficult to fix, just remove any benefit to starting a fire.

No crop permitted to be grown on any satellite identified fire area that year.

Make the mushrooms they seek illegal to be sold and offer a big reward to anyone snitching on someone selling them.

They can easily claim they did not start it... "Must have been a cigarette thrown from a car"....etc etc.

57 minutes ago, joedee said:

They can easily claim they did not start it... "Must have been a cigarette thrown from a car"....etc etc.

No excuses accepted

I cannot understand the non action of the Government regarding this pollution problem. It’s not only in the very north in fact it affects most of the country as far south as Chumphon. Is it any wonder this news is making its way into the foreign media,

I can imagine that these stories will soon start to effect the willingness of tourist to visit the LOS, then MAYBE the government will take action.

I know an American guy that raised two kids there, both kids have serious asthma conditions.

13 hours ago, joedee said:

They can easily claim they did not start it... "Must have been a cigarette thrown from a car"....etc etc.

By a foreigner