On the morning of April 1, the Northern region turned cooler as a weak cold air mass moved in from the night of March 31, bringing widespread showers and thunderstorms, with hail reported in some areas.
According to the Vrain automatic rainfall monitoring system, many locations recorded rainfall of 20–50mm by early morning. Notably, Lien Mac Station in Hanoi measured 54mm, Tan Tien in Lao Cai 39mm, Hung My in Tuyen Quang 32mm, while several areas in Cao Bang recorded over 20mm. In Tuyen Quang Province, cumulative rainfall from 7 p.m. on March 31 to 3 a.m. on April 1 reached 106.6mm.
Hanoi experienced rain and thunderstorms overnight into the early morning, particularly from midnight onward. Some western parts of the capital also saw light hail. Meteorological authorities attributed the conditions to weak cold air compressing a low-pressure trough, resulting in widespread storms across the Northern region.
At the same time, hailstorms struck several northern mountainous provinces. In Cao Bang Province, strong winds and hail damaged 743 houses and 38 hectares of crops, according to preliminary local reports. In Tuyen Quang, hail lasting 20–30 minutes affected agricultural production, while localized hail was also recorded in Lang Son on March 31. In Viet Tri City, Phu Tho Province, hail occurred overnight and into the early hours of April 1 during heavy thunderstorms.
The National Center for Hydro-Meteorological Forecasting said that the cold spell is relatively weak, mainly bringing rain and cooler temperatures without causing severe cold conditions. Temperatures in the North dropped by around 4–5 degrees Celsius on April 1, making the weather milder.
The National Steering Committee for Civil Defense warned that thunderstorms may bring whirlwinds, lightning, hail and strong gusts. Residents in mountainous and midland areas are advised to take proactive measures to minimize damage.
Meanwhile, data from the Vrain system showed little to no rainfall from Quang Tri southward to the Central Highlands and Southern regions on the morning of April 1.
The meteorological agency forecasts that hot temperatures of 35–36 degrees Celsius will persist in the Southern region for several more days, while the Central region is expected to see an end to the recent heatwave starting April 1.
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