Singapore's 24-hour PSI hits 181 in the centre, the highest of this haze season

Singapore's air crossed into the worst reading of this haze season on Friday. At noon the 24-hour Pollutant Standards Index in the central region stood at 181. The west was at 170, the south at 160, the east at 155 and the north at 123. Every region was in the unhealthy band. The National Environment Agency's 5 p.m. update put the 24-hour PSI between 134 and 192, and the one-hour PM2.5 between 91 and 134 micrograms per cubic metre, which NEA classes as Band 2, elevated.

A 24-hour PSI of 101 to 200 is unhealthy. Above 200 is very unhealthy. The central reading of 181 sits close to that line. NEA's forecast for the next day was unhealthy to low very unhealthy, which means the index can move through 200 if the wind holds.

Where the smoke is coming from

NEA said moderate to dense smoke haze from southern and central Sumatra was drifting toward Singapore. Smoke was also visible over parts of Kalimantan. Isolated to scattered hotspots were detected in Kalimantan and in southern and central Sumatra. Few hotspots showed up elsewhere in the southern ASEAN region. Many air-quality stations in Peninsular Malaysia, Singapore, Kalimantan and Sumatra were reporting unhealthy to hazardous levels.

The wind is the mechanism. Under southeasterly or southwesterly flow, smoke from Sumatra's east coast has a short path across the Strait of Malacca and the Singapore Strait. A shift to a northerly wind would clear the island faster than any local measure. NEA said some showers are forecast over Singapore and parts of the surrounding region over the weekend. Dry weather is still expected over parts of southern Sumatra and Kalimantan, so the source is not forecast to die out with the first rain over the city.

How the index is meant to be used

NEA separates the one-hour PM2.5 reading from the 24-hour PSI. The one-hour figure is for a decision about going outside now. The 24-hour figure is for planning the next day. At 11 a.m. the one-hour PM2.5 in the centre re-entered the high band at 152 micrograms per cubic metre, then eased to 151 at noon. Other regions stayed elevated, between 104 and 147. By 5 p.m. the one-hour range had fallen to 91 to 134, even as the 24-hour index remained unhealthy. That split is normal. The 24-hour number carries the morning peak for hours after the air has started to improve.

Health advice on the NEA haze page scales with the index and with the person. Healthy adults are told to reduce prolonged outdoor exertion once the 24-hour PSI is unhealthy. Children, older people, and anyone with heart or lung disease are told to avoid it. The agency points readers to haze.gov.sg, the myENV app, and its Facebook page for the next update.

What Friday's number changes

This season already has a legal track in Indonesia. A class action over Borneo fire haze had its first hearing in Pontianak on 7 October, with plaintiffs asking for a national disaster declaration. Friday's Singapore reading does not decide that case. It does fix a public number that schools, contractors and sports clubs can use. Outdoor training, construction dust rules and school dismissal times in Singapore are written against PSI bands, not against a general description of haze.

The comparison that matters inside the city is with earlier days this season, not with 2015. NEA and Channel NewsAsia both treated 181 as the highest 24-hour reading so far in 2026. If the weekend forecast holds, Saturday could print a higher one. The number to watch is whether the central 24-hour PSI crosses 200, the threshold at which NEA's advisory moves from reduce outdoor activity to avoid it for the general population.

Until that update, the verified picture is a city inside an unhealthy band, a smoke plume traced to Sumatra and Kalimantan, and a weekend in which local rain may not reach the fires that are feeding the plume.