01 March 2025

You may have already heard about it—the city of Chiang Mai is considered, at certain times of the year, one of the most polluted zones in the world. While pollution is a global scourge, the burning season plays a significant role. What exactly is it? What causes it? How can you avoid it and protect yourself? When does it occur and where should you go to escape the fire season during a trip to Thailand? Read on for the full guide.

What Is Thailand's Burning Season?

Also known as the smoke season, fire season, burning season, or smog in English, the burning season corresponds to the most polluted period of the year in northern Thailand. During this time, the sky turns gray, the air becomes heavy and difficult to breathe. A thick haze transforms landscapes and reduces visibility...

But what causes it? Here are the main causes of Thailand's burning season:

Slash-and-Burn Agriculture

Slash-and-burn agriculture is an ancient farming technique that involves burning land to clear an area and fertilize the soil using the ash generated by fire.

While this practice is banned and illegal in many countries worldwide due to the damage it causes (pollution and health hazards, environmental and wildlife damage), it remains widely practiced in tropical countries like Thailand. Why? Because it's highly effective at eliminating agricultural waste and preparing land for rapid replanting at minimal cost.

As you've gathered, slash-and-burn agriculture is the primary cause of the smoke season in Thailand. It's practiced by numerous farmers who take advantage of the dry season to burn their sugarcane, rice, or corn fields. The smoke generated by agricultural burning extends across rural areas, but also urban zones, creating atmospheric pollution for several weeks.

Involuntary Fires

With rainfall absent in northern Thailand for several weeks after the monsoon ends, soils are dry, which facilitates slash-and-burn farming. The problem? Fires can spread quickly, and other involuntary blazes occur, amplifying the pollution and smoke phenomenon.

Other Pollution Sources

While fires constitute the main causes of the smoke season in Thailand, other elements add to the list of pollution sources:

• road traffic and vehicle emissions,
• industrial activity, and
• human activities in general.

Good to Know:

Thailand isn't the only Asian country using slash-and-burn agriculture. This practice is also used in neighboring countries, such as Laos, Cambodia, Vietnam, Malaysia, and Indonesia.

Which Areas Are Most Affected by Thailand's Smoke Season?

Slash-and-burn agriculture is predominantly used by farmers in northern Thailand. Therefore, the north of the country is most affected by the fire season. The city of Chiang Mai is often considered the epicenter of the phenomenon and even one of the most polluted cities in the world!

Among the zones most affected by the smoke season in Thailand, you'll find:

• Chiang Mai Province,
• Chiang Rai Province,
• Lampang Province,
• Lamphun Province,
• Mae Hong Son Province,
• Phayao Province.

Smog: What Health Risks?

The burning season significantly impairs air quality and causes pollution levels that reach record levels.

To give you an idea, the fine particulate level in Chiang Mai often exceeds 290 µg/m³, over 60 times the maximum threshold set by the World Health Organization (WHO). For this reason, the city was classified as the world's most polluted city during the last smoke season in 2024.

The catch? As the WHO explains, fine particles (PM2.5) caused by air pollution can cross the lung barrier and enter the bloodstream, which can lead to "strokes, heart disease, lung cancer, and acute and chronic respiratory diseases."

Children, elderly individuals, and those suffering from respiratory issues (such as asthma and allergies) are most affected by the phenomenon, but everyone is at risk from fine particle inhalation.

Among the main symptoms observed during the fire season in northern Thailand are:

• Eye, nose, and throat irritation,
• Eye itching,
• Cough,
• Congestion and chest pain,
• Breathing difficulties...

According to a study conducted by Chiang Mai University's School of Medicine, pollution in the Northern region has worsened over the last decade, leading to an increase in patients suffering from lung diseases (including lung cancer).

When Does Thailand's Smoke Season Occur?

The burning season occurs each year during the dry season in northern Thailand. There are no official dates (everything depends on the seasons and farmers), but it generally begins in January and ends in April. A peak is often observed in March, during which the highest fine particulate rates are recorded. The end of the fire season coincides with Songkran, the Thai New Year.

What Can You Do to Avoid Thailand's Burning Season?

Not only is the smoke season extremely harmful to health, but it can also disrupt any trip to northern Thailand. Because the pollution creates a thick fog that impairs visibility. Result? Landscapes are less attractive and treks can even prove dangerous (difficult breathing while hiking).

So if you've planned a trip to Thailand during the burning season, here are our tips:

Steps to Take to Protect Your Lungs

Are you in Chiang Mai or any other must-see destination in the northern part of the country? Then, it's wise to take precautions:

Wear an Appropriate Mask

To avoid inhaling fine particles and protect your airways, we recommend wearing a mask. There's no point in opting for a standard surgical mask, which will be of little effectiveness. Instead, choose an N95 mask capable of filtering 95% of particles in the air.

Avoid Physical Activities and Treks

During the smoke season, it's advisable to avoid outdoor physical activities. If possible, skip treks and return during another period to discover the most beautiful hiking trails around Chiang Mai or in the region.

Stay Indoors

Limit your outdoor outings as much as possible and stay inside to minimize exposure to fine particles. Ideally, choose accommodation equipped with an air filtration system.

Monitor Air Quality in Real Time

To plan your stay, visits, and activities, we recommend tracking Air Quality Index (AQI) levels on a website or app like iqair.com or aqicn.org.

Where to Go in Thailand During the Smoke Season?

If you can, the best option is to avoid any stay in northern Thailand between January and April (especially in March). You're wondering where to go during Thailand's burning season? Know that central Thailand may be slightly affected depending on weather conditions (winds...) and that Bangkok remains polluted year-round regardless.

The ideal solution? Head to the southern part of the country, which is much less affected by the burning season. You'll notice, in fact, that many Thais and expatriates living in Northern Thailand come to spend a few months in the South to escape the pollution.

Among the destinations to explore in Southern Thailand in January, February, March, and April, we recommend:

• Phuket,
• Krabi,
• Khao Sok National Park,
• Khao Lak,
• Koh Lanta,
• Koh Phi Phi,
• The Similan Islands,
• Koh Lipe,
• Koh Chang,
• Koh Kood (Koh Kut),
• Koh Samui,
• Koh Tao,
• Koh Phangan.

Also discover our itineraries exploring southern Thailand:

• Splendors of Southern Thailand at Budget Prices
• Southern Islands for Couples
• The Grand Discovery of Southern Thailand

Florine Dergelet

Florine Dergelet

A web writer for over 10 years, Florine Dergelet is a traveler driven by the desire to discover the world with an open heart. Each of her articles is an invitation to slow down, to listen, to understand. Because for her, traveling isn't about checking countries off a map, but weaving bonds (often invisible but always powerful) with places, peoples, and all manner of creatures in the animal kingdom. Her motto? Advise travelers with ethics, raise awareness about animal welfare, respect for cultures, and the importance of humble and sustainable tourism. Because the most beautiful memories are often born far from the spotlight, in the shadow of a trail, at the edge of a conversation, or in the quiet whisper of a world we finally take the time to listen to…