SINGAPORE - The National Day weekend is expected to be haze-free - but wet.

Prevailing southerly winds, as well as rain in the surrounding regions, mean Singapore is not likely to be affected by the transboundary smoke, the Meteorological Services Singapore (MSS) said on Friday.

Brief thundery showers are expected in the late morning and early afternoon over both days, with air quality hovering in the moderate range.

The MSS also said the El Nino weather phenomenon, which scientists predict will take effect later this year, has "gradually eased" in recent weeks.

El Nino refers to the abnormal warming of the tropical Pacific Ocean which can disrupt normal weather patterns and is linked to hotter and drier weather.

The MSS added: "A weak to moderate El Nino is still likely to develop in the last quarter of 2014."

This could worsen dry weather conditions and increase the risk of smoke from land and forest fires in the region. Singapore could be affected by transboundary haze if prevailing winds blow haze from Sumatra or Kalimantan toward the Republic.