Singapore’s air quality deteriorated sharply on Saturday, Sept. 26, as the 24-hour Pollutant Standards Index (PSI) in the central region climbed to 108, pushing back into the unhealthy range. According to the National Environment Agency (NEA), the central region reading hit 104 at 8 p.m. before inching up to 108 at 9 p.m., crossing the 101 threshold that demarcates clean air from unhealthy conditions.
Regional Breakdown and PM2.5 Concentrations
While the central region breached healthy limits, other parts of the island remained in the moderate band late Saturday evening. Readings recorded at 10 p.m. stood at 78 in the north, 83 in the south, 96 in the east, and 94 in the west. Hourly PM2.5 readings—which measure immediate concentrations of fine particulate matter—spiked more dramatically, reaching an elevated band of 131 in the central area at 9 p.m.
Other parts of the island also saw surges in fine particulate matter. At 9 p.m., hourly PM2.5 concentrations registered across the east, west, and south, while the northern reading climbed to 69. Under NEA classifications, an hourly PM2.5 reading between 56 and 150 indicates an elevated concentration of fine particles.
Weather Patterns and Transboundary Haze
The latest deterioration stems from smoke plumes drifting from fires in parts of Indonesia. In its daily haze advisory issued at 6 p.m. on Sept. 26, the NEA noted that moderate to dense smoke continued to emanate from fires in southern and central Sumatra as well as southern and eastern Kalimantan.
While overnight showers were forecast for parts of the region, dry conditions are expected to persist across southern Sumatra and parts of Kalimantan. Prevailing winds blowing from the south-east or south-west remain capable of pushing additional smoke haze toward Singapore.
Official Health Advisories and Previous Spikes
The NEA advises healthy individuals to reduce prolonged or strenuous outdoor activities when air quality enters the unhealthy range. Vulnerable groups—including the elderly, pregnant women, children, and individuals with chronic heart or lung disease—are urged to minimize or avoid outdoor exertion entirely.
This episode follows earlier haze events in September. Singapore’s air quality first returned to the unhealthy range on Sept. 4, marking the first time since October 2023. Readings peaked earlier in the month, with the central region hitting 154 on Sept. 15 before briefly dipping into moderate levels ahead of Saturday’s resurgence.
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