Localised flooding was reported in Cao Xanh, Ha Khanh, Bai Muoi, Cao Thang, Ha Lam and around Halong I Market, with several roads submerged.
The national weather agency forecast moderate to heavy rain, with some areas expected to receive more than 250 mm between Monday and Wednesday morning.
Halong, Mong Cai, Binh Lieu, Ba Che and Tien Yen are among the areas at greatest risk of flooding, flash floods and landslides, particularly in mountainous areas and along rivers and streams.
Authorities warned that prolonged rainfall could trigger landslides on steep slopes, especially near road construction sites, coal mines and tunnels, while low-lying residential areas and roads remain vulnerable to flooding.
Residents were advised to reinforce their homes, secure property, avoid unnecessary travel during heavy rain and stay away from flooded roads and fast-flowing streams.
