The combination of cooler air and intense rainfall caused temperatures in Trung Khanh District of Cao Bang Province to fall dramatically by around 10 degrees, dropping from 33°C to approximately 23°C within a short period.
The cold air mass is currently generating heavy rain across Thai Nguyen, Tuyen Quang and parts of Quang Ninh Province.
Meteorologists forecast that from the evening of June 8 through the night of June 9, widespread heavy rainfall will continue across northern Vietnam before gradually expanding into north-central provinces, including Thanh Hoa and Nghe An.
The heaviest rainfall is expected in the northwestern region, northern Phu Tho Province and Tuyen Quang Province, where accumulated rainfall could reach 80-160mm, with isolated locations receiving more than 250mm.
Elsewhere in northern Vietnam, rainfall totals are forecast at 20-50mm, with some areas exceeding 100mm.
In Thanh Hoa and Nghe An provinces, rainfall is expected to range between 50-100mm, with some locations likely to receive more than 150mm.
The widespread rain event is forecast to weaken from June 10.
Cooler weather but growing risk of severe storms
Meteorologists said the late-season cold air mass will bring unusually cool and comfortable overnight temperatures to northern Vietnam on June 8 and 9, with lows ranging from 21°C to 25°C.
However, weather experts have warned that the arrival of cooler air immediately following an extended period of intense heat could trigger powerful convective storms.
Residents are advised to remain alert for dangerous weather conditions, including severe thunderstorms, tornado-like whirlwinds, hail and strong wind gusts.
Heavy rainfall over a short period could also cause localised flooding in low-lying areas, urban centres and industrial zones. Flash floods on small rivers and streams, as well as landslides in mountainous northern provinces, are also considered significant risks.
Strong winds may damage rooftops, uproot trees and affect vulnerable structures.
Authorities urged residents who need to travel outdoors during this period to closely monitor weather conditions and take appropriate precautions.
Flood warnings issued for northern rivers
Hydrological experts forecast a new flood event on major rivers in northern Vietnam between the evening of June 8 and June 10.
Water levels on upstream sections of major river systems are expected to rise by between two and four metres.
Peak water levels on smaller rivers could reach Alert Level 1 or Alert Level 2 thresholds.
Meteorological agencies have also issued warnings of a high risk of flash floods and landslides in mountainous and midland provinces across northern Vietnam.
Bao Anh
