SINGAPORE - Air quality across Singapore may have improved on Friday (Oct 2), but hazy conditions are expected to persist and could even deteriorate on Saturday (Oct 3).

The 24-hour Pollutant Standards Index (PSI) for the next 24 hours is expected to be between the middle and high sections of the unhealthy range, and could enter the low end of the very unhealthy range if denser haze is blown in.

Visibility on Saturday is likely to get worse, especially in the morning when humidity is high. This is because moisture has a swelling effect on the haze particles, the National Environment Agency said in an update on Friday evening.

It added that widespread haze is still persisting in parts of central and southern Sumatra.

Heavy showers over most parts of Singapore early on Friday had provided a welcome respite.

As of 4am, the 24-hour PSI was between 109 and 138, in the unhealthy range. The three-hour PSI - not tied to a health advisory - stood at 158, up from a low of 87 at 8am.

The Primary School Leaving Examinations (PSLE) had gone ahead as usual on Thursday despite earlier concerns that it could be postponed, as haze levels hovered in the high end of the unhealthy range.

Precautionary measures such as conducting all examinations in enclosed spaces were taken.

The Pedestrian Night at Orchard Road, which had been scheduled to take place on Saturday (Oct 3), was cancelled due to the haze.

For updates, visit the NEA website and the haze microsite, and follow NEA's Facebook page or Twitter account, or download the myEnv app.