Northern region to experience rare off-season cold spell on May 13-15.

Deputy Director of the National Centre for Hydro-Meteorological Forecasting Hoang Phuc Lam said the mercury will drop to 20-23 degree Celsius at the lowest, even 16 or lower in mountainous areas, and heavy rains may appear.

Experts also warned of whirlwinds, lightning, hails and strong winds.

People are advised to keep a close watch on the weather forecasts and stay cautious of high-risk areas against landslides and floods.

Communication work must be bolstered to urge vessels to take safety measures amid rough seas.

The centre forecasts that up to 10-12 typhoons and tropical depressions will enter the East Sea until the end of this year, 4-6 of which will directly affect Viet Nam.