Singapore forecasts unhealthy air quality for Thursday
Singapore’s environment agency forecast that the 24-hour Pollutant Standards Index (PSI) would be between 101 and 160 on Thursday, 22 October, placing the expected range in the unhealthy category. Its advisory, dated Wednesday, 21 October, urged people to plan outdoor activity around that outlook while checking a separate hourly pollution measure before going outside immediately.
For healthy people, the agency advised reducing prolonged or strenuous outdoor physical exertion on Thursday. Older people, pregnant women and children were advised to minimise such exertion, while people with chronic lung or heart disease were told to avoid it. The advice reflects the forecast category and does not mean that every person or neighbourhood will experience the same air quality.
The distinction between the forecast and the live reading matters. The 24-hour PSI is used to plan ahead for activities lasting many hours, including outdoor work or events. The one-hour PM2.5 reading is intended to guide immediate choices, such as whether to exercise outdoors at that time. PM2.5 refers to fine particles measuring 2.5 micrometres or smaller. Hourly concentrations can change with weather and may vary around the island.
The agency’s specific instructions for Thursday pair the forecast with hourly checks. Healthy people should reduce strenuous outdoor activity if the immediate PM2.5 reading is elevated. For older people, pregnant women and children, elevated hourly PM2.5 means avoiding strenuous outdoor activity for the next hour. The same instruction applies to people with chronic lung or heart conditions. Those in the latter group should avoid prolonged or strenuous outdoor exertion under the unhealthy 24-hour forecast even before applying the hourly guidance.
At the time of the advisory, the forecast was not a report that a single island-wide reading had already reached a particular level. The agency presented a range for the following day. Its broader explanation says the PSI combines sub-index values for six pollutants, including PM2.5, and uses the highest sub-index. A PSI of 101 or above is classified as unhealthy. This makes the index a planning signal, not a substitute for checking current conditions.
Winds and smoke remain uncertain
The agency said smoke haze from fires in the region might continue moving towards Singapore on Friday under forecast southeasterly or south-south-easterly winds. It also expected winds to shift towards the southwest on Saturday. With dry conditions forecast over southern and central Sumatra, smoke from Sumatra might drift towards Singapore. These are conditional outlooks rather than confirmation that haze will reach any particular location.
There are limits to what can be inferred from satellite views. The agency said lighter smoke haze may not be discernible in imagery and that cloud cover prevented it from determining the full extent of hotspots and smoke haze. That caveat leaves room for incomplete detection; it does not establish how much smoke was missed or where it travelled.
An independent regional report described a mixed picture on Wednesday evening: hourly PM2.5 readings were in the normal band in northern, eastern and southern areas, while western and central readings were elevated. It also reported that the 24-hour PSI was unhealthy in the west and centre, while the other three regions were in the good-to-moderate range. Those readings were time-specific and do not replace Thursday’s forecast or establish Thursday’s eventual conditions.
The practical message is to use each measure for its intended time horizon: consult the PSI forecast when arranging the next day, then check the latest hourly PM2.5 reading for an immediate decision. The agency makes these readings and advisories available through its air-quality services. If people feel unwell, especially children, older people or those with chronic heart or lung conditions, its general haze guidance says to seek medical attention.
