SINGAPORE - There could be slight haze in Singapore if hot spots increase in Sumatra, the National Environment Agency (NEA) said on Thursday (Sept 29).

The prevailing winds for the next few days are forecast to blow from the west-southwest or west-northwest. Dry weather conditions are also expected over parts of Sumatra.

"There is a possibility that Singapore could experience slightly hazy conditions if hotspot activities increase in Sumatra," NEA said in an haze advisory on Thursday evening.

There were four hotspots detected in Sumatra on Thursday, and no visible smoke plumes or haze were observed, said NEA.

It will monitor closely and provide updates when necessary, NEA added.

For Friday, the 24-hour Pollutants Standard Index (PSI) was forecast to be moderate and the one-hour PM2.5 concentration normal.

Thundery showers are also expected over parts of Singapore in the afternoon.

Haze returned to Singapore during the last week of August, when the 24-PSI hit unhealthy levels. But it beat a hasty retreat after a few days.