There has been an increase in the number of hotspots over Sumatra, with 241 detected on Sep. 27 and 145 detected on Sep. 28, according to the National Environment Agency (NEA).

NEA stated on its haze website that moderate to dense smoke plumes emanating from persistent hotspot clusters in South Sumatra have been observed, and the smoke plumes have been blown towards the northwest by prevailing winds.

In addition, with dry weather forecast to prolong over southern and central Sumatra in the coming days, elevated hotspot activity and moderate to dense haze conditions can be expected to persist there.

The prevailing winds are also forecast to blow mainly from the southeast or southwest.

Under these conditions, there is an increased risk of transboundary haze occurrence, NEA added.

Wind keeping dense haze away from S'pore but PSI may worsen if direction changes

In a separate press release on Sep. 29, NEA said the 24-hour Pollutants Standards Index (PSI) entered the moderate range in the east of Singapore, when it hit 81.

The 28 public agencies that make up the government’s Haze Task Force (HTF) are ready to roll out their respective haze action plans should the air quality deteriorate into the Unhealthy range, with the PSI reaching above 100, NEA stated.

NEA added that while Singapore is not expected to experience severe haze in the coming days, the PSI may deteriorate if there is a shift in wind direction.

Currently, nearby winds are expected to continue blowing from the southeast and keep the dense haze away from Singapore.

How to check air quality

Members of the public can check the air quality in different parts of Singapore on the NEA website.

As of 6pm on Oct. 1, the PSI value across Singapore was 57 to 78.

This is in the moderate range.

You may also refer to the website for health advisories on outdoor activities during haze.

For healthy persons, strenuous outdoor activities should be reduced if the 24-hour PSI level is higher than 100, or if the 1-hour PM2.5 level is higher than 55µg/m3.

Here's the 1-hour PM2.5 level as of 6pm on Oct. 1:

Earlier this year in May 2023, the Meteorological Service Singapore (MSS) reported that El Niño conditions are forecast to develop in the second half of 2023.

From June to October 2023, warmer and drier conditions are expected in Singapore and the surrounding region.

This will increase the risk of transboundary haze affecting Singapore and the region.

Top collage via Wikimedia Commons/Wolcott for illustrative purposes and haze.gov.sg.