SINGAPORE - The Republic is set to get some relief from the haze, with air quality forecast to improve, as thundery showers are expected on Tuesday (Sept 24), the National Environment Agency (NEA) said in an update on Monday evening.
It added that the 24-hour Pollutant Standards Index (PSI) is likely to drop from the low end of the unhealthy range to the high end of the moderate range as the day progresses.
The one-hour PM2.5 concentration, which the NEA said is a better indicator of current air quality, should also remain in the normal band.
But PM2.5 readings may occasionally enter the elevated band under light wind conditions, the agency warned.
At 11pm on Monday, the PSI reading across Singapore was 89-106, between the moderate and unhealthy bands.
The one-hour PM2.5 concentration, which measures the concentration of tiny particles less than 2.5 micrometres in diameter, was 39-60 micrograms per cubic m, in the normal and elevated bands.
A PSI reading of zero to 50 indicates good air quality while a reading of 51 to 100 is in the moderate range. A reading of 101 to 200 is considered unhealthy. Air quality is considered very unhealthy when the PSI ranges from 201 to 300, and hazardous when the reading is more than 300.
There are four bands on the PM2.5 concentration scale: 0 to 55 for normal, 56 to 150 for elevated, 151 to 250 for high, and very high for any higher readings.
The NEA said there was a drop in the number of hot spots detected in Sumatra on Monday, falling from 246 on Sunday to 60. This was partly due to showers falling over northern and central Sumatra, as well as western Kalimantan, on Monday.
For the next few days, more showers are forecast over the region.
The NEA said that while there was slight haze over Singapore on Monday, the situation improved due to showers across Singapore and the surrounding sea.
But the increased moisture in the atmosphere, coupled with the slight haze on Monday morning, resulted in visibility in some areas of Singapore to be between 3km and 5km. Visibility eventually improved to 7km to 8km in most areas in the afternoon.