SINGAPORE – With more thundery showers expected in Singapore and showers in parts of Sumatra in the next few days, the likelihood of haze here in the next 24 hours continues to be low, according to latest government forecasts.

Even so, there could be occasional slightly hazy conditions if prevailing winds shift to blow smoke haze from Sumatra to Singapore, said the National Environment Agency (NEA) on Friday evening (Sept 27).

The agency said that for the next 24 hours, the one-hour PM2.5 reading, which it has said is a better measure of current air quality, is expected to remain in the normal band.

However, the reading may occasionally enter the elevated band.

The 24-hour Pollutant Standards Index (PSI) reading is forecast to be in the moderate range, slightly worse than the good to moderate range NEA had predicted for Friday on Thursday.

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, very unhealthy 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.

At 7pm on Friday, the 24-hour PSI reading was 68-75, in the moderate range. The PM2.5 reading was 25-34, in the normal band.