Northeast monsoon winds that have so far kept the haze in Sumatra, Indonesia, at arm's length from Singapore may begin to weaken in the second half of March, posing "some risk" of the haze affecting Singapore, the National Environment Agency (NEA) has warned. This may happen if winds begin to blow from the west, it said in an advisory on Thursday.

The coming inter-monsoon period that typically lasts from late March to May brings light winds in more variable directions.

An NEA spokesman noted that the prolonged dry weather in the region has caused an escalation of hotspots in central and northern Sumatra since early February, with smoke plumes and dense haze visible in Riau province. Hotspots were also detected in parts of Peninsular Malaysia, he added.

On Monday, Indonesia's Terra and Aqua satellite detected 337 hotspots of forest and plantation fires in Riau province. The haze there has caused respiratory problems and forced some schools to temporarily close. Low visibility has also caused flight delays.

An unusual dry spell there since late December has seen farmers taking the opportunity to clear land by starting fires, which are causing the haze. The dry season there is typically from April to June.

The NEA said that it will continue to monitor the situation and provide updates when necessary.

Last June, Singapore suffered its worst ever bout of haze, which saw pollutant levels reach record highs.