Thunder storms over Perlis, Kedah and West Johor waters are expected to persist until tonight.

The Meteorological Department said in a statement here that a similar situation would also occur in the waters of Phuket and the Straits of Melaka.

"The situation may cause strong winds of up to 50 kilometres per hour and choppy sea with waves of up to 3.5 metres high which would be dangerous for small boats," according to the statement.