Sumatra squalls are lines of thunderstorms which usually occur between March and November each year.

They move from Sumatra towards Singapore, usually during the pre-dawn or early morning hours.

The thunderstorms are often characterised by sudden onset of strong. gusty winds and heavy rain.

Yesterday, south-western Singapore recorded the highest wind speed of the night with 103.7kmh. This happened at 2.50am.

But this was lower than the highest wind speed on record - 144.4kmh recorded on April 25, 1984.

The south-west monsoon season, from June to early October, sees favourable winds for these storms. They can last for up to two hours as they move across the island.

Information from Meteorological Service Singapore and National Environment Agency