According to meteorological experts, the change was mainly caused by a weak cold air mass combined with upper-level wind convergence, leading to a significant drop in temperatures and relief from the prolonged hot spell.

In Hanoi and many provinces across Northern Vietnam, thunderstorms accompanied by lightning and strong winds helped temperatures fall sharply compared to previous days. Some areas recorded a decrease of 4-6°C overnight, bringing cooler and more comfortable conditions after days of extreme heat with temperatures ranging from 37-39°C.

Prior to the weather shift, Northern and Central Vietnam had experienced one of the first widespread heatwaves of the summer season. Many localities reported extremely high outdoor temperatures combined with low humidity, making conditions particularly uncomfortable in major urban areas.

The surge in electricity demand for cooling systems also caused localised power overloads in some places.

However, from the evening of May 16, weather patterns changed rapidly as strong convective cloud systems developed across the region, triggering widespread showers and thunderstorms. Rain was not limited to Northern Vietnam but also expanded into the North-central region, Central Highlands and southern provinces.

According to the National Centre for Hydro-Meteorological Forecasting, the weak cold air intrusion combined with an upper-air convergence zone was the main driver behind the rainfall event. Although much weaker than winter cold fronts, the system was still sufficient to disrupt atmospheric conditions and trigger widespread cooling.

Meteorologists forecast that thunderstorms in Northern Vietnam may continue over the next few days, particularly during the late afternoon and nighttime hours. Mountainous and midland areas could experience moderate to heavy rainfall, with isolated locations facing very heavy downpours.

Meanwhile, Central Vietnam is also expected to gradually cool as thunderstorms become more widespread in the evenings.

In the Central Highlands and Southern Vietnam, weather conditions are forecast to remain sunny during the day with scattered showers and thunderstorms developing later in the afternoon and evening. Some urban areas may face localised flooding due to short periods of heavy rainfall.

Despite bringing relief from the heat, meteorologists continue to warn about dangerous weather phenomena associated with thunderstorms, including whirlwinds, lightning, hail and strong gusts. Northern mountainous provinces are also being warned about the risks of flashfloods and landslides if prolonged heavy rain occurs.

Mid-May is typically a seasonal transition period in Vietnam, when alternating heatwaves and strong thunderstorms frequently occur. The arrival of weak cold air during this period is not considered unusual, but it can still create significant weather fluctuations across northern and north-central Vietnam.

Current forecasts suggest that cooler conditions in the north may continue for several more days before hot weather potentially returns toward the end of May.

Northern Vietnam heatwave eases as heavy rain forecast from May 16

VOV.VN - After several days of intense heat with temperatures exceeding 39°C in some areas, weather conditions across many parts of Vietnam are beginning to cool as thunderstorms are expected to return from the evening of May 16.