Toxic smoke from widespread wildfires on Indonesia's Borneo and Sumatra islands has left millions of people struggling to breathe, forcing school closures, overwhelming health services and spreading haze across borders into Malaysia and Singapore. Indonesia's health ministry warned that some 3.4 million people across seven provinces are at risk of respiratory infections, as fires driven by the El Niño weather pattern — which disrupts global wind patterns, atmospheric pressure and rainfall — rage through forests and vast tracts of carbon-rich peatland.

Residents in affected cities describe near-unbearable conditions. In Pekanbaru, the capital of Sumatra's Riau province, one resident said the smog thickened so severely at night that the city felt nearly abandoned. "My eyes sting so badly. When I go outside, it really feels like breathing in the smoke from freshly burned trash," he said. In Jambi, also on Sumatra, a mother reported that both she and her four-year-old child had begun coughing persistently and that she was having trouble breathing. Dozens of schools in Pekanbaru have been shuttered, with authorities urging residents to stay indoors, while kindergartens and elementary schools in Jambi switched to home learning. Indonesia's health ministry has distributed more than 260,000 face masks to those in the worst-affected areas.

The scale of destruction is already surpassing recent precedents. Between January and July, more than 200,000 hectares burned — an area three times the size of the capital Jakarta, and larger than the damage recorded during previous El Niño seasons in 2019 and 2023. South Sumatra recorded the highest number of active fire hotspots nationwide, at 1,429, followed by West Kalimantan and Central Kalimantan, the Indonesian portions of Borneo island. Nearly 940 square kilometres were burned in July alone.

Authorities have responded on multiple fronts. President Prabowo Subianto announced the deployment of dozens of helicopters, water-bombing aircraft and thousands of personnel, expressing cautious optimism that the fires could be brought under control within one to two weeks. Thirty aircraft are conducting cloud-seeding operations over Kalimantan, while a further 22 cover Sumatra. Police have arrested 72 people on suspicion of deliberately starting fires, and four companies are under investigation for allegedly using burning to clear land cheaply — a practice known as slash-and-burn that is widely blamed for the annual crisis. In South Sumatra, authorities also turned to faith, organising a mass Islamic rain prayer known as salat istisqa, in which around 3,000 residents gathered in Palembang's governor's courtyard as smoke reduced daytime visibility to near-darkness.

The haze has become a regional emergency. In Malaysia's Sarawak state — which shares Borneo island with Indonesia and Brunei — nearly 600 schools closed last week due to poor air quality, and Kuala Lumpur briefly ranked as the second most polluted city in the world on air quality tracker IQAir. Malaysia has said it stands ready to assist in firefighting efforts. The crisis underscores a recurring pattern in Southeast Asia, where Indonesia's dry season fires generate diplomatic strain with neighbours and severe public health consequences at home — consequences that scientists warn will intensify as El Niño events become more frequent.