SINGAPORE — The 24-hr Pollutant Standards Index (PSI) is forecast to gradually improve to the high end of the “moderate range” overnight if prevailing wind conditions continue, the National Environment Agency said on Sunday (Sept 15).

The agency said that the haze situation in Singapore has gradually improved overnight “due to the prevailing winds shifting to blow from the southeast”.

For the rest of the day, slightly hazy conditions are expected to continue and the prevailing winds are forecast to blow from the southeast or south.

As at 8pm on Sunday, the 24-hr PSI was between 94 and 103, which is between the “moderate” and low end of the “unhealthy” range. The 1-hr PM2.5 was 50-71 µg/m3, between the “normal” and “elevated” bands. For the next 24 hours, the 1-hr PM2.5 readings are expected to be between these bands.

“A total of 439 hotspots were detected in Sumatra today, mostly in the central and southern provinces of Riau, Jambi, South Sumatra and Lampung,” the NEA said.

“Moderate to dense smoke haze continued to emanate from persistent hotspots in these provinces, and some smoke haze from Riau and Jambi has been blown by the prevailing winds to affect Singapore and parts of Peninsular Malaysia.”

For the next few days, the weather in Singapore is expected to be generally dry except for a few brief showers, the NEA said.

The haze situation in Sumatra is expected to persist and Singapore may still experience slightly hazy conditions, the agency added.