SINGAPORE - Air quality is expected to improve further on Monday, according to the National Environment Agency (NEA).

The Pollutant Standards Index (PSI) was in the moderate to unhealthy range on Sunday morning, but dipped to the moderate range from 10am.

"Slightly hazy conditions can still be expected for the rest of today," the NEA said at 6pm on Sunday. "For tomorrow, the prevailing winds are forecast to strengthen and blow from the south or southeast, and a further improvement in the air quality can be expected."

At 5am, the 24-hour PSI reading was 69 to 105. But this dipped to 67 to 89 at 6pm.

The PSI for the next 24 hours is forecast to be in the moderate range. Given the air quality forecast, everyone can continue with normal activities, the NEA said.

People who are not feeling well, especially the elderly and children, and those with chronic heart or lung conditions, should seek medical attention.

The newly introduced 1-hour PM2.5 concentration was in the normal range on Sunday at 6pm for most regions, except the north, where readings were 61. For other regions, readings were 27 in the south, 25 in the west, 37 in the east and 25 in the central region.

The 1-hour PM2.5 concentration is expected to stay in the "normal" band over the next 24 hours, said NEA.

The agency added: "During the haze season, the main air pollutant is PM2.5. 1-hour PM2.5 concentration readings are a good indicator of the current air quality. Use this for immediate activities like going for a jog."

Thundery showers are also forecast in the late morning and early afternoon on Monday.

The PSI crept into the unhealthy range for the first time this year on Friday (Aug 26), as westerly winds brought smoke from forest fires in Sumatra to Singapore.

Air quality is considered unhealthy when the 24-hour PSI is within the 100-200 range.