SINGAPORE - Haze conditions worsened on Sunday (Oct 18), but Singaporeans may get some relief towards the end of October, with the south-west monsoon season coming to an end.

The inter-monsoon period that follows typically brings more rain, and light, variable winds to Singapore and the region, the Meteorological Service Singapore (MSS) said in response to queries from The Straits Times.

"The expected onset of inter-monsoon conditions towards the end of this month will help to gradually ease the haze situation in Singapore in the coming weeks," said the MSS.

But it added that Singapore can still experience hazy conditions due to several factors, including the location and extent of the fires in Sumatra and Kalimantan, direction of the prevailing winds and frequency of rain.

The south-west monsoon season typically lasts from June to September or early October. The inter-monsoon period will usually last till November, before the north-east monsoon starts in December until early March.

In an advisory on Friday (Oct 16), MSS said that wetter weather conditions can be expected in the last two weeks of October.

The weather will remain warm, with maximum daily temperatures of 34 to 35 deg C, but afternoon thundery showers are expected on four to six days.

Experts have said earlier that the haze is set to remain until November, due in part to the dry spell caused by the El Nino effect said to be among the strongest since records were kept in 1950.

The 24-hour Pollutant Standards Index (PSI) was between 74 and 140 on Sunday. As of 11pm, the 24-hour PSI was 113 to 140, while the three-hour PSI was 147.

In an update on Sunday evening, the National Environment Agency (NEA) forecast that the 24-hr PSI for the next 24 hours would be in the low to mid sections of the unhealthy range, and may enter the high section of the unhealthy range if denser haze is blown in.