SINGAPORE, Sept 6 — Air quality across Singapore improved to moderate levels this morning after haze pushed pollution into the unhealthy range in three regions a day earlier, although authorities warned that smoke from fires in Indonesia could continue to affect the city-state.

As of 7am today, all five regions were recording 24-hour Pollutant Standards Index (PSI) readings within the moderate range, according to the National Environment Agency (NEA), CNA reported.

The central region had fallen to a PSI of 91 by midnight, after peaking at 123 at 1am yesterday. The west and east also returned to moderate levels, recording readings of 86 and 77 respectively at midnight.

Earlier yesterday, both regions had crossed into the unhealthy range, with the west reaching 103 and the east 102 at 6am.

The north and south remained within the moderate range throughout yesterday, standing at 75 and 72 respectively at midnight.

The improvement followed Singapore’s first breach of the unhealthy PSI threshold since October 2023. The 24-hour PSI crossed above 100 at 7am on Friday, the first time it had done so since October 8 that year.

That prompted NEA to begin issuing daily haze advisories, including 24-hour PSI forecasts intended to help residents plan outdoor activities and events.

But the improvement may prove temporary.

In its Saturday advisory, NEA said Singapore could continue to experience transboundary haze if fires in Indonesia remained active, with the PSI forecast to range from the higher end of moderate to the lower end of unhealthy.

Most surrounding areas remained dry yesterday, while moderate to dense smoke plumes over southern and central Sumatra and parts of Kalimantan continued to drift towards Singapore, NEA said.

Dry weather is expected to persist across Singapore and the surrounding region in the coming days, with prevailing winds blowing from the southeast or south.

Agencies under Singapore’s Haze Task Force have also activated their respective action plans and public health advisories in response to the deteriorating air quality.

The 24-hour PSI, which forms the basis of NEA’s health advice, measures six pollutants including fine particulate matter, or PM2.5, which is typically the dominant pollutant during haze episodes.

A PSI reading of between 101 and 200 is classified as unhealthy, while levels between 201 and 300 are considered very unhealthy. Readings above 300 are deemed hazardous.