There has been a deterioration in the haze condition in Singapore since Tuesday, with the pollutant standard index (PSI) remaining at an unhealthy range.

This was due to haze from Sumatra being blown in by the prevailing south-southeasterly winds.

The National Environment Agency (NEA) warned the haze may enter the high end of the unhealthy range today if denser haze from Sumatra was blown in.

It said the current hazy conditions are expected to persist for the rest of today.

As at 3pm today, the 24-hour PSI was 84-120, high end of the moderate range and the low end of the unhealthy range, and the three-hour PSI was 146.

A 24-hour PSI reading of above 100 indicates unhealthy air quality.