SINGAPORE - Air quality deteriorated slightly on Sunday (Aug 23) afternoon as the three-hour Pollutants Standard Index (PSI) hovered near the high end of the moderate range.

A familiar acrid smell could be detected in some parts of Singapore, while the skies remained greyish throughout the day.

The three-hour PSI peaked at 97 - just four points shy of hitting the unhealthy band - at 4pm, before dropping to 83 three hours later.

The 24-hour PSI was 72-79 as at 7pm.

According to the latest National Environment Agency (NEA) update on Sunday evening, the slight hazy conditions were due to the haze being blown in from Sumatra by the prevailing winds.

Showers are expected in the early morning and late afternoon on Monday, although there might still be the occasional slight haze if winds blow from the south or southwest.