Based on official figures, the 24-hour Pollutant Standards Index (PSI) at 8am on Oct 8 showed that air pollution levels across Singapore stayed within the unhealthy category, registering 113 in the north, 118 in the south, 126 in the east, 161 in the west and 146 in the central region. The PSI functions as a 24-hour rolling average incorporating six primary air pollutants to help individuals schedule outdoor tasks for the following day, and readings from 101 to 200 designate the air quality as unhealthy.
Regional PSI and PM2.5 Readings Across Singapore
While the 24-hour PSI readings spanned the unhealthy band across all five regions, current air quality indicators showed a different pattern. PM2.5 readings, which measure immediate air quality for current activities, were elevated only in the west with a reading of 79 at 8am. Readings remained in the normal band for the north at 40, the south at 10, and the east at 46. Meanwhile, the central region re-entered the elevated band with a reading of 56 after briefly dipping to 53 at 7am.
According to the National Environment Agency (NEA), the 24-hour PSI readings entered the unhealthy range across Singapore at noon on Wednesday and stayed there overnight. Local news outlets indicated that haze conditions prompted about 200 schools, kindergartens and nurseries within the Bahu Pahat district of Johor, a Malaysian state situated approximately 140km northwest of Singapore, to shut down on Wednesday.
Did You Know? The highest PSI reading of the year reached 167 in central Singapore on Sept 29, accompanied by a peak 1-hour PM2.5 reading of 165 at midnight, marking the first time since October 2023 that the PSI hit unhealthy levels due to haze.
Smoke Plumes From Sumatra and Kalimantan Drive Haze
The National Environment Agency (NEA) reported that moderate to dense smoke plumes from southern Sumatra in neighboring Indonesia were observed drifting toward Singapore, alongside moderate to dense smoke haze from hotspots in Kalimantan. Dry conditions are expected to persist across central and southern Sumatra and many parts of Kalimantan. Under prevailing southeasterly to southerly winds, smoke haze from these regions may continue to drift toward Singapore.
In its daily haze advisory issued on Oct 7, the NEA forecast that the haze situation would worsen, pushing the PSI entirely into the unhealthy range. This marked the first time since the agency began issuing daily advisories on Sept 4 that the forecast fell completely within the 101 to 200 band. Previous forecasts during the period were moderate or mixed.
Protecting vulnerable groups during haze conditions
The NEA advises that when 24-hour PSI readings sit in the unhealthy band, healthy individuals should reduce prolonged or strenuous outdoor physical activities. Vulnerable groups, including the elderly, pregnant women, children, and those with chronic lung or heart disease, should minimize or avoid such activities entirely. For immediate activities, residents are advised to consult 1-hour PM2.5 readings.
Looking at broader climate factors, authorities previously warned of a heightened haze risk between June and October driven by warmer and drier conditions from both El Niño and the Indian Ocean Dipole. The Meteorological Service Singapore stated that strong El Niño events tend to delay the retreat of the dry season across the southern ASEAN region, expecting a weather transition only in late October or early November.
Frequently Asked Questions
What constitutes an unhealthy PSI level in Singapore?
Air quality is categorized as unhealthy when the 24-hour Pollutant Standards Index (PSI), a rolling average of six key air pollutants, falls within the range of 101 to 200.
How do 1-hour PM2.5 readings differ from the 24-hour PSI?
The 24-hour PSI is used to plan outdoor activities for the following day, whereas 1-hour PM2.5 readings point to current air quality and serve as a gauge for immediate activities.
When is the weather transition expected to arrive?
The Meteorological Service Singapore expects a transition away from the dry season during late October or early November, later than in the previous two years.
How have the recent haze conditions affected your daily outdoor routines and travel plans this week?