SINGAPORE -Singaporeans may breathe better when they wake up on Monday morning, with improvements to the air quality expected.

The National Environment Agency (NEA) said on Sunday (Sept 15) that the Pollutant Standards Index (PSI) reading is expected to gradually improve over the next 24 hours to the high end of the “moderate” range overnight – if prevailing wind conditions continue.

Normal activities can largely continue, given the forecast, the NEA said.

“However, caution should still be exercised, and persons who are not feeling well, especially the elderly and children, and those with chronic heart or lung conditions, should seek medical attention,” it said.

As at 7pm on Sunday, the 24-hour PSI was 97-105, within the “moderate” to the low end of the “unhealthy” range.

This was already an improvement from the morning, which saw readings climb to 124. The PSI crossed the “unhealthy” level on Saturday for the first time since 2016 when western Singapore showed a reading of 103 at 4pm.

A PSI reading of zero to 50 indicates that the air quality is good, while a reading of 51 to 100 is in the “moderate” range. The air quality is considered to be “very unhealthy” when the PSI ranges from 201 to 300, and it is “hazardous” when the reading goes above 300.

The NEA added that the one-hour PM2.5 concentration readings over the next 24 hours are expected to be between the “normal” and the low end of the “elevated” bands.

The one-hour PM2.5 reading at 7pm on Sunday was between the same bands, at 45 to 64 micrograms per cubic metre.

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 readings above 250.

The weather for the next few days is expected to be dry with some brief showers. Slightly hazy conditions are still expected, with prevailing winds forecast to blow from the south or south-east.

“NEA is monitoring the situation closely and will provide further updates when necessary,” the agency said.