Singapore's air quality improves to moderate levels after peak haze season

By late evening on September 30, Singapore's air had cleared enough to breathe easier. The Pollutant Standards Index readings that had spiked into dangerous territory just hours earlier had retreated across all five regions of the island, settling into the moderate range between 81 and 99. It was a visible exhale after weeks of watching the sky thicken and the numbers climb.

The crisis had peaked the day before. On the morning of September 29, the central region's PSI hit 164—the worst reading of the entire haze season, surpassing a previous high of 154 set two weeks earlier on September 15. For the first time in fourteen days, air quality across all five regions of Singapore had breached into the unhealthy band, where the National Environment Agency recommends residents reduce time outdoors. That synchronized spike across the island hadn't happened since mid-September either.

By 1 a.m. on September 30, the central and western regions had already begun to improve, dropping to a peak of 134. The fine particulate matter—PM2.5—that had been accumulating in the air started to clear as showers moved across Singapore and the surrounding region. The hourly PM2.5 readings, which measure current concentrations of the finest particles, fell back into normal bands, ranging between 18 and 37 across all regions by late evening. These readings matter because they tell you what to expect in the next few hours, while the 24-hour PSI average is what residents should use to plan their day.

This September marks a significant threshold. It is the first time since October 2023 that Singapore has experienced unhealthy air quality from haze. The authorities had warned earlier in the year that the period from June through October carried elevated risk, driven by warmer and drier conditions created by two overlapping climate patterns: El Niño and the Indian Ocean Dipole. The PSI first crossed into unhealthy territory on the morning of September 4, when central Singapore registered 101. In the weeks that followed, readings in various parts of the island occasionally dipped into that range, but nothing sustained until late September.

The source of the smoke is not mysterious. Dry conditions persist over southern Sumatra and south-western Kalimantan—regions where fires burn during the dry season, sending smoke across the Strait of Malacca toward Singapore. The National Environment Agency's forecast for October 1 predicted showers would continue over Singapore and its surroundings, which should help suppress the haze further. But the agency also flagged a persistent risk: the prevailing winds are expected to continue blowing from the south-east or south, which means smoke from those burning regions will keep drifting toward the island.

The improvement by September 30 evening offered relief, but it was conditional. Dry conditions are forecast to continue in parts of southern Sumatra and south-western Kalimantan. As long as those fires burn and the winds blow from the right direction, Singapore remains downwind of the problem. The haze season is not over, and neither is the risk.