Singapore experiences slight haze as PSI reaches high of 71

SINGAPORE - Hazy skies could be seen once again as air quality gradually worsened throughout the day.

The National Environment Agency's (NEA) three-hour Pollutant Standards Index (PSI) reached a high of 71 at 8pm today, a sharp increase from 54 at 6pm. The PSI then dipped slightly to 61 as of 10pm, according to NEA.

The 24-hour PSI reading ranged from 42 to 50, with the highest PSI readings in the North and South.

The PSI reading of PM2.5 concentration, or very fine particulate matter, was between 29 and 33 micrograms per cubic metre.

A PSI reading of zero to 50 indicates good air quality, while anything above 100 indicates unhealthy air quality.

NEA noted that the PSI readings have been elevated since 5pm.

"The haze may be attributed to hotspots to the north of Singapore, blown in by the prevailing northeasterly winds. A total of 4 hotspots were detected in Peninsular Malaysia today, and 35 hotspots in Sumatra," NEA said in a latest update to Singapore's haze situation.

NEA said that hazy conditions are expected to persist overnight.

On Thursday, NEA said that with the expected transition from the Northeast Monsoon to the inter-monsoon period in the second half of March 2014, winds in the region will turn light and variable in direction.

This may pose some risk of transboundary haze affecting Singapore should the hotspots in Sumatra persist and the prevailing winds in the region temporarily turn westerly.

The inter-monsoon period typically lasts from late March to May. 

The agency added that although increased rainfall can be expected later in the month, the total amount of rainfall for March this year is expected to be below average for most parts of the region.

NEA said it will continue to monitor the situation and provide updates as necessary. 

For updates, members of the public can visit NEA's website at or the haze microsite at Updates will also be posted on NEA's Facebook at and NEA's twitter account @NEAsg.

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