Recent years have seen a rise in unusually heavy rainfall, with climate change making weather patterns more erratic and harder to forecast.
Forecasters say shifts in El Nino Southern Oscillation phases in 2026 could increase volatility, raising the likelihood of localised heavy rain, thunderstorms, whirlwinds and lightning.
Nguyen Van Huong of the National Centre for Hydro Meteorological Forecasting said total rainfall nationwide is expected to remain close to the long term average.
The rainy season in the Central Highlands is forecast to begin from late April to early May, in southern Vietnam from mid May, in northern Vietnam around May, and in central Vietnam from about September.
Historic flooding in central Vietnam in 2025 (Photo: Dantri).
However, rainfall distribution is expected to become more uneven, with short bursts of intense local rain occurring more frequently even if the number of widespread heavy rain events does not increase.
Widespread heavy rainfall is likely to begin in northern Vietnam from June, gradually moving south and ending around November in central regions.
Experts warn that flash floods and landslides could become more frequent in mountainous areas of northern and central Vietnam, particularly during peak rainy months and seasonal transition periods.
As ENSO shifts towards a warmer phase, potentially developing into El Nino by the end of the year, temperatures are expected to rise, bringing a higher risk of extreme weather including thunderstorms, hail and localised downpours.
“2026 is expected to be a year of more extreme and less predictable weather,” Huong said, highlighting the periods from March to May and September to October as requiring particular vigilance.
In coastal areas, high tides are forecast along the south eastern coastline in the final months of the year. Water levels at Vung Tau station could exceed 4.3 metres in November and December, increasing flood risks in low lying areas.
Meanwhile, saltwater intrusion in the Mekong Delta during the early 2026 dry season is expected to remain near average levels and lower than the previous year.
Between May and July, localised drought and water shortages may affect areas beyond irrigation coverage, particularly in Gia Lai, Dak Lak and Lam Dong.
