Malaysian Meteorological Department (MetMalaysia) director-general Jailan Simon said they had forecast thunderstorms and rain would sweep across the coastal areas of Perak, Selangor, Melaka, Negri Sembilan, west of Johor and the east of Sabah in the morning.
In the evening, states and territories in the west coast, especially in Perak, Selangor, Putrajaya, Kuala Lumpur and Melaka, would experience thunderstorms.
“We expect the current wet conditions with on and off thunderstorms will continue until middle of next month,” he said.
Asked if this meant the monsoon season was arriving early, Jailan said Malaysia was still experiencing the usual southwest monsoon season which began on May 18.
“However, the southwest monsoon season is a bit weak this year, causing the situation to be a bit more wet compared to previous years,” he said.
Several areas in the Klang Valley were hit by flash floods this week following heavy rain.
The department had issued a severe thunderstorm warning for Peninsular Malaysia and parts of Sabah yesterday.
The advisory said heavy rain and strong winds were expected to last until 1pm.
The affected states were Perak (Manjung, Bagan Datuk, Hilir Perak, Batang Padang and Mulim), Pahang (Rompin) and Selangor (Sabak Bernam and Hulu Selangor).
In Sabah, severe thunderstorms hit Tawau (Lahad Datu) and Sandakan (Kinabatangan).
In the morning, Perak experienced rain over parts of its coastal areas, rain in one and two places in Penang, Negri Sembilan and Melaka as well as rain in one or two places in coastal areas in Kedah, Selangor and Johor.
MetMalaysia issued another advisory forecasting thunderstorm later in the day to other states including Perlis, Kedah, Kelantan, Terengganu and Johor as well as Sarawak.
Several parts of Pahang were also hit by thunderstorms, including Cameron Highlands, Raub, Lipis, Jerantut and Maran.
Asked of a possibility of haze during this period, he said it could occur if there was out of control open burning.
“However, the possibility of a bad haze is quite low,” he said.
For next month, MetMalaysia forecast that many states in the peninsula would experience an average rainfall of between 100mm and 300mm except for Johor Baru, Iskandar Puteri, Pontian, Kulai, Kota Tinggi, Kluang and Batu Pahat, which would have an above average rainfall between 200mm and 300mm.
Many parts of Sarawak are expected to receive an average rainfall of between 150mm and 350mm except for areas in Kuching, Samarahan, Sri Aman, Betong, Sarikei and Sibu, which are expected to experience an above average rainfall of between 250mm and 350mm.
Sabah and Labuan are expected to receive an average rainfall of between 100mm and 350mm.
Universiti Malaya (UM) meteorological expert Dr Sheeba Chenoli said with Malaysia being an equatorial maritime country, there would be tremendous heating and availability of vast amounts of moisture.
“This contributes to the vertical development of the cumulonimbus clouds. They are associated with thunder, lightning, heavy rainfall and cold winds (during this period),” she said.
The authorities have advised the public to be cautious of the dangers posed by water columns in waterfall areas and to avoid parking vehicles in flood-prone areas.
The public can access the latest weather information on the website www.met.gov.my, via the myCuaca app, Malaysiamet Facebook page and @malaysianmet on Twitter.