SINGAPORE - Occasional hazy conditions are expected on Tuesday (Sept 8), with the 24-hour Pollutant Standards Index (PSI) for the next 24 hours to fluctuate between the high end of the moderate range and low end of the unhealthy range, said the National Environment Agency (NEA) on Monday evening.

The 24-hour PSI, a measure of air quality here, may further deteriorate if the winds are unfavourable.

The NEA said the prevailing winds are forecast to blow from the south or south-west on Tuesday, and thundery showers are to be expected in the late morning and early afternoon.

Hazy conditions were experienced on Monday afternoon, after a slight shift in the prevailing winds brought back the haze from Sumatra.

As at 6pm, the 24-hour PSI was between 76 and 87, in the high end of the Moderate range. Hazy conditions are expected to persist for the rest of the day.

When 24-hour PSI readings are below 100, normal activities can be carried out. But when they start to inch above 100, the authorities advise healthy people to reduce prolonged or strenuous outdoor activity.

The elderly, pregnant women and children should do as little of such activity as possible, while those suffering from chronic lung or heart disease should not engage in these activities.

For updates, the public can go to the haze microsite at www.haze.gov.sg, follow NEA's Facebook and Twitter page, or download the myENV app.