The storm hit at about 1.30 am and lasted around 30 minutes, bringing hailstones as large as half a fist, according to local officials.
Strong gusts caused a stilt house to collapse while eight people were inside. Four escaped unharmed, while the others were injured and taken to hospital.
The worst damage was reported in Trung Tam Village, near the former Bac Ha Town.
Local authorities have visited the injured and are assessing the extent of losses.
The National Centre for Hydro-Meteorological Forecasting said a weak cold air mass moving south had compressed a low-pressure trough, triggering unstable weather conditions.
Northern areas, excluding Lai Chau and Dien Bien, along with Thanh Hoa, are forecast to experience moderate to heavy rain and thunderstorms from the night of April 16 to April 17, with rainfall of 20 to 40 mm and isolated areas exceeding 100 mm.
The agency warned of possible tornadoes, lightning, hail and strong winds during storms, as well as flash floods and landslides in mountainous areas and localised flooding in low-lying regions.
