SINGAPORE - Singapore may experience occasional slight daytime haze on Tuesday, the National Environment Agency (NEA) said in its daily update.

Thundery showers are expected in the late morning and early afternoon, and the 24-hour Pollutant Standards Index (PSI) is expected to be between the high end of the moderate range and the low end of the unhealthy range.

Healthy people are advised to reduce prolonged or strenuous outdoor physical exertion, while the elderly, pregnant women and children should minimise such activity.

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

It said the total number of hot spots detected in Sumatra and Kalimantan in Indonesia on Monday was 48 and 171 respectively, but the low count for Sumatra was due to clouds obstructing satellites' view. "Smoke haze was visible in eastern Kalimantan and southern Sumatra," the agency added.

At 7pm on Monday, the 24-hour PSI was between 77 and 93 across the island, in the moderate air quality range. Air becomes unhealthy when the index crosses 100.