Meteorologists described the event as the strongest heatwave since the beginning of this summer, arriving earlier and with greater intensity than the multi-year average.

According to the National Centre for Hydro-Meteorological Forecasting, the primary cause is the strong development and eastward expansion of a western low-pressure hot zone, which has pushed temperatures sharply higher across a large area. Foehn wind effects in the north-central region have further intensified the dry and oppressive heat conditions.

On May 15, temperatures in the northern delta region, including Hanoi, were forecast to reach 37-38°C. Actual outdoor temperatures in densely populated urban areas could be 2°C to 4°C higher due to concrete surfaces and heavy traffic density.

In north-central and central Vietnam, many areas are experiencing severe heat with temperatures ranging from 38°C to 39°C, while some locations may exceed 39°C.

Meteorologists said the peak of the heatwave is expected from midday through early afternoon on May 15 and continuing into May 16. Humidity levels are forecast to drop to around 45%–55%, significantly increasing the risks of fires, heatstroke and dehydration. Outdoor workers, elderly people and children are considered the most vulnerable groups.

When will the heatwave end?

According to the latest forecasts, Northern Vietnam is expected to remain under extreme heat conditions through May 16. From the night of May 16 onward, widespread thunderstorms are likely to develop as a weak cold air mass pushes a low-pressure trough deeper into the northern region.

From May 17, temperatures in northern Vietnam are forecast to decrease by around 4°C to 6°C, with many areas shifting to showers and thunderstorms, including the possibility of locally heavy rain.

Meanwhile, central Vietnam is expected to experience a slower cooldown, with heat conditions gradually easing around May 17.

Weather authorities also warned that the sudden transition from intense heat to thunderstorms could trigger dangerous weather events such as tornadoes, lightning, hail and strong winds.

Meteorologists said the summer of 2026 is being shaped by multiple extreme weather patterns simultaneously. One major factor is the potential development of El Niño during the second half of the year.

Some forecasts estimate the probability of El Niño emerging between June and August at 80% to 90%.

In addition, rainfall levels during May are expected to remain 15%-30% below the multi-year average in several regions, allowing the ground to absorb and retain more heat, which could prolong heatwaves beyond normal patterns.

Meteorologists also observed strong “heat dome” activity across Southeast Asia in recent weeks. This phenomenon occurs when a mass of hot air becomes trapped in the lower atmosphere, leading to persistently high temperatures across multiple countries, including Vietnam.

Summer 2026 forecast to be hotter than average

Climate trend assessments indicate that the number of heatwave days in northern and north-central Vietnam this summer could exceed the long-term average. Heatwaves are anticipated to arrive earlier, last longer and alternate with severe thunderstorms caused by clashes between weak cold air masses and extreme surface heat.

Weather agencies also forecast that the peak heat period of summer 2026 will likely occur during June and July. Average nationwide temperatures are set to remain approximately 0.5°C to 1°C higher than historical averages, especially across northern and central regions.

Although the current heatwave is forecast to ease after May 16-17, experts warned that more severe heat events could still occur later this summer.

Residents are advised to closely monitor weather updates, avoid outdoor activities during peak heat hours between 11am and 4pm, and proactively take measures against heatstroke, dehydration and fire risks during the hottest months of the year.

Extreme heat disrupts daily life in Hue, locals adapt to hot weather

VOV.VN - A severe heatwave sweeping across central Vietnam is significantly disrupting daily life in Hue city, where outdoor temperatures have at times exceeded 40°C, leaving streets unusually quiet as residents seek shelter from the scorching sun.