Sumatra wildfire smoke blankets Hat Yai in southern Thailand

Smoke from forest fires on Indonesia’s Sumatra island blanketed Hat Yai and other parts of Thailand’s lower South on Wednesday (September 16, 2026), pushing air pollution into the red warning category and prompting calls for residents to stay indoors.

The south-westerly monsoon has continued to carry smoke into the region, reducing air quality to levels harmful to health.

Prince of Songkla University’s Air Pollution and Health Effects Research Centre reported that concentrations of fine particulate matter (PM2.5) had risen to between 75.0 and 89.0 micrograms per cubic metre (µg/m³), levels associated with adverse health effects.

The centre urged residents to avoid leaving home and to wear a face mask for protection if going out was unavoidable.

Eight southern provinces require close monitoring

The provinces requiring close monitoring are Songkhla, Yala, Pattani, Narathiwat, Satun, Phatthalung, Trang and Nakhon Si Thammarat, as PM2.5 concentrations remain persistently high in many parts of the lower South.

In Hat Yai district, the hourly PM2.5 reading stood at 85.5 µg/m³, described in the report as having a serious impact on health, while the daily average was 77.9 µg/m³.

With winds still blowing from the south-west, smoke from burning areas in southern Sumatra continues to reach southern Thailand.

Poor air circulation allows pollution to accumulate

Very low ventilation rates are expected across southern Thailand during September 14–23, 2026, owing to light winds and a low atmospheric mixing height.

These conditions restrict the upward dispersal of smoke and prevent pollutants arriving from outside the region from clearing. Fine particles consequently accumulate in the atmosphere close to the ground, reaching levels harmful to health.

People with pre-existing conditions, including allergies, have already begun experiencing symptoms such as burning sensations in the nose and throat.