The extreme heat in the Klang Valley, especially in the Kuala Lumpur city centre, which created 'heat islands' could have been a factor contributing to the hailstorm which occurred here yesterday afternoon, according to a climate expert.

Climatologist and oceanographer at Universiti Kebangsaan Malaysia, Professor Dr Fredolin Tangang said the rapid development in Kuala Lumpur and the climate changes had resulted in thunderstorms caused by heat trapped inside a moisture surrounding.

"The moist conditions and phenomenon of wind updraft produce water droplets which form ice lumps which can no longer be supported by the wind.

"When these lumps become big and the winds can no carry them, they drop as ice, together with the rain which was what happened yesterday," he told Bernama here today.

About 6pm yesterday, parts of Kuala Lumpur were hit by a rare hailstorm and flash flood, causing traffic congestion and damaging buildings and homes.

Kuala Lumpur City Hall received 35 reports involving fallen trees while the Express Rail Link service between Bandar Tasik Selatan and Putrajaya was disrupted.

Tangang said the freak thunderstorm could happen more frequently after this due to climatic changes and rising temperatures.

"Research done overseas have shown scientific evidence that as the earth becomes warmer due to climatic changes, there will be more thunderstorms such as these," he added.

However, he said scientific studies on local climatic change factors had not been carried out, making it difficult for experts to predict the phenomenon.

"We do not have specific studies on the phenomenon as it rarely occurs here as compared to other countries like the United States or Europe.

"However, the concept of this phenomenon is the same anywhere, which is when there is moisture in the air and a rise in temperature, hailstorms will occur more frequently," he said.

Tangang urged more detailed studies on local factors be carried out so that the relevant parties could predict the weather in the future.

Meanwhile, in a statement today, the Meteorological Department said thunderstorms, heavy rains and strong winds in Beaufort, Kota Belud, Tuaran, Kota Kinabalu, Penampang and Papar in Sabah as well as Miri in Sarawak were expected to continue until late Saturday afternoon.

The statement said that thunderstorms were also expected to occur in the waters off Johor, Pahang, Kudat in Sabah and the Labuan Federal Territory and continue until early Saturday afternoon.