Nguyen Van Huong, head of weather forecasting at the National Centre for Hydro-Meteorological Forecasting, said El Nino was the most significant large-scale weather pattern expected to affect Vietnam in the months ahead.
According to current forecasts, the probability of El Nino developing between June and August exceeds 90 per cent, while the likelihood of a strong El Nino event has risen to about 40 per cent, up from previous estimates of around 25 per cent.
"This is a signal that requires close attention because strong El Nino events are often associated with more extreme weather conditions," Huong said.
Meteorologists forecast that average temperatures across the country will remain above normal, with more frequent and intense heatwaves than those recorded in 2025.
Rainfall is forecast to be 25-50 per cent below average nationwide, particularly in northern Vietnam, though short bursts of extreme rainfall remain possible.
"Rainfall may be lower than average overall, but extreme rainfall events can still occur," Huong said.
Experts say this pattern reflects a growing trend linked to climate change, in which weather events become more localised, intense and difficult to predict.
Fewer storms, but stronger impacts
Although the number of storms and tropical depressions in the East Sea is forecast to remain below average, weather authorities warned that powerful storms with unusual tracks could still develop and cause significant damage.
Vietnam's peak storm season is expected to run from July to November, bringing an increased risk of widespread heavy rain, flash floods, landslides in mountainous areas and severe urban flooding.
Thunderstorms, tornadoes, lightning, hail and strong winds are also forecast to occur more frequently than average.
"There may be fewer disasters in number, but they are likely to be more extreme and more localised," Huong said.
Growing drought and water shortage risks
El Nino is also expected to increase the risk of water shortages across the country.
River flows and reservoir levels during the 2026 flood season are forecast to remain below average, raising concerns about drought, saltwater intrusion and water scarcity in the early months of 2027.
Officials pointed to severe drought and salinity intrusion events in 2015-16, 2019-20 and 2023-24 as examples of the potential impacts of strong El Nino conditions.
Despite expectations of lower overall rainfall, meteorologists warned that localised extreme rainfall events remain highly likely during this year's rainy season.
Huong cited recent examples in northern Vietnam, where exceptionally heavy rainfall was recorded over short periods in mid-May.
On May 16, Minh Long Commune in Cao Bang Province recorded 117.4mm of rainfall in just one hour, while Halong area in Quang Ninh received about 82mm within an hour on May 17, causing localised flooding in urban and low-lying areas.
Meteorologists said similar extreme rainfall events could occur elsewhere in Vietnam during the coming months, increasing the risks of flash floods, landslides and urban inundation.