All five regions enter unhealthy range as smoke from Indonesian fires reaches Singapore.

Singapore’s latest haze episode reached a significant threshold on September 15, with air quality deteriorating across every region before conditions began improving later in the day.

All Five Regions Enter Unhealthy Range
All five regions of Singapore recorded unhealthy air quality on the morning of September 15, the first time the entire island had simultaneously entered the unhealthy range since September 2019. At 6 a.m., the 24-hour Pollutant Standards Index stood at 104 in the north, 111 in the south, 128 in the east, 128 in the west and 154 in the central region. Singapore classifies PSI readings between 101 and 200 as unhealthy.

Central Singapore Records Highest PSI
The central region reached the day’s highest reported PSI of 154, while readings across all five regions remained unhealthy at 9 a.m. They stood at 103 in the north, 106 in the south, 122 in the east, 124 in the west and 148 in the central region. The northern region had been the last to enter the unhealthy range, rising from 99 at midnight to 102 at about 1 a.m.

Smoke From Kalimantan Drifts Toward Singapore
Singapore’s National Environment Agency (NEA) said moderate to dense smoke plumes from forest fires in Kalimantan had been observed drifting toward Singapore, while smoke plumes were also detected in southern Sumatra. NEA said prevailing winds from the southeast to east-southeast meant Singapore was likely to continue being affected by smoke haze.

PM2.5 Levels Improve During Morning
One-hour PM2.5 readings were elevated in parts of Singapore early on September 15, reaching 66 micrograms per cubic meter in the central region and 59 in the west at 6 a.m. Other regions recorded between 32 and 44. By 9 a.m., however, PM2.5 readings across the island had returned to the normal range of 28 to 36 micrograms per cubic meter.

Air Quality Improves Later in the Day
Conditions gradually improved as September 15 progressed. By 7 p.m., the north and south had returned to the moderate range with PSI readings of 92 and 91, while the central region remained unhealthy at 130, followed by the west at 112 and east at 111. NEA advised the public to reduce prolonged or strenuous outdoor physical activity when air quality entered the unhealthy range, with more stringent precautions recommended for vulnerable groups.

Singapore’s first islandwide unhealthy PSI episode since 2019 shows how smoke from fires in Indonesia can affect air quality across national borders. Singaporeans are being advised to adjust outdoor activities when pollution rises, while developments in Kalimantan and southern Sumatra remain directly relevant to Indonesians living near the fires and to neighboring countries affected by the resulting haze.

Sources: CNA (2026) , Malay Mail (2026)

Keywords: Singapore Haze 2026, Singapore PSI, Unhealthy Air Quality, Indonesia Forest Fires, Kalimantan Smoke, Sumatra Haze