SINGAPORE – The haze situation here on Oct 9 may ease slightly, with the National Environment Agency (NEA) forecasting that the 24-hour Pollutant Standards Index (PSI) readings will be in the high moderate to mid-unhealthy range.
This is compared with the agency’s haze advisory a day earlier, when it forecast the PSI readings on Oct 8 to be entirely in the unhealthy band.
The 24-hour PSI readings – a 24-hour rolling average of six key air pollutants – was in the unhealthy band across Singapore from noon on Oct 7 to 5pm on Oct 8.
The reading for the northern part of Singapore dropped to 100 at 6pm the same day, before dipping further to 98 at 7pm. However, the PSI readings remained in the unhealthy band for the rest of Singapore, ranging from 105 in the south to 139 in the west at 7pm.
Air quality is considered unhealthy when the PSI reading ranges from 101 to 200, during which the NEA advises the public to at least reduce prolonged or strenuous outdoor activities. PSI readings of 51 to 100 are considered moderate, while values of zero to 50 are in the “good” range.
PM2.5 readings, meanwhile, were elevated across three regions as at 7pm – the south (97), west (97) and central (128) – while the northern and eastern parts of the island registered values of 53 and 49 respectively.
The hourly PM2.5 reading is used as a gauge for immediate air quality, with scores from 56 to 150 indicating elevated pollution levels.
Oct 7 was the first time, since the NEA started issuing daily haze advisories on Sept 4, that the forecast has fallen completely within the unhealthy band of 101 and 200. Previous forecasts in the same period were in the moderate, or moderate to unhealthy ranges.
In its Oct 8 advisory, NEA said moderate to dense smoke plumes from southern and central Sumatra and West Kalimantan were observed to be drifting towards Singapore, with dry conditions expected to continue in the neighbouring Indonesian territories.
“Under the prevailing south-easterly or southerly winds, smoke haze may continue to drift towards Singapore,” it added.
The PSI crossed into the unhealthy range four weeks ago, hitting 101 in central Singapore on the morning of Sept 4. In the days that followed, readings in the central, eastern and western parts of the island occasionally crossed into the unhealthy range.
The highest reading of the year – 167 in central Singapore – was recorded on Sept 29. That same day, the central region also saw the highest 1-hour PM2.5 reading of 2026 of 165 at midnight.
These developments over the past month marked the first time since October 2023 that the PSI in Singapore hit unhealthy levels because of haze, with the authorities earlier warning of the risk of haze between June and October as a result of warmer and drier conditions brought on by both El Nino and the Indian Ocean Dipole.
Some experts have predicted that the haze in Singapore in 2026 could last for a longer period due to the “Godzilla” El Nino event, which could reduce rainfall and result in higher temperatures over October and November, compared with non-El Nino years.
During non-El Nino years, the dry south-west monsoon season usually tapers off by September, and the start of the rainy north-east monsoon season tends to set in around late November.
The Meteorological Service Singapore (MSS) told The Straits Times that El Nino events, particularly strong ones, tend to delay the retreat of the dry season for much of the southern ASEAN region.
The Met service added that it is expecting a transition only during late October or early November for Singapore, later than in the previous two years.