Occasional hazy conditions are expected today, said the National Environment Agency (NEA) yesterday evening.
The 24-hour Pollutant Standards Index (PSI) - a measure of air quality here - is expected to fluctuate between the high end of the moderate range (51 to 100) and low end of the unhealthy range (101 to 200).
The prevailing winds are forecast to blow from the south or south-west.
The 24-hour PSI may further deteriorate if the winds are unfavourable, the NEA warned.
It said thundery showers are also expected in the late morning and early afternoon.
A slight shift in prevailing winds yesterday afternoon brought the haze here from Sumatra, Indonesia. As at 7pm yesterday, the 24-hour PSI was between 77 and 89, which put the air quality at the high end of the moderate range.
The elderly, pregnant women and children are advised to minimise prolonged or strenuous outdoor activity, while those suffering from chronic lung or heart disease should avoid these activities when the 24-hour PSI exceeds 100.