Due to fine particles in the air, Sunday's haze forecast is expected to be unhealthy.

The 24-hour PM2.5 level on Sunday is expected to be slightly elevated, the National Environment Agency said on Saturday in its daily haze forecast.

Based on this, Sunday's health advisory is more cautious, even though the 24-hour PSI is expected to be in the 51-100 band from 6pm on Saturday till 6pm on Sunday.

Healthy people are advised to minimise prolonged or strenuous outdoor physical exertion, while the elderly, pregnant women and children should minimise prolonged outdoor activity and those with chronic illnesses should avoid all outdoor activity and wear N95 masks if they cannot avoid it.

At 5pm on Saturday, the 24-hr PSI was 59-68 (moderate) and the 24-hr PM2.5 was 52-61 micrograms per cubic metre.

Low-level winds are forecast to blow from the southeast or southwest for the next few days, and slightly hazy conditions can be expected on Sunday, with thundery showers in the late morning and early afternoon.