The ministry said the ENSO system is shifting from La Nina to neutral, with an 80-90 per cent chance of El Niño developing between June and August. It could strengthen to moderate or strong by late 2026, with a 20-25 per cent chance of becoming very strong and lasting into 2027.
Dry, hot conditions have emerged early in 2026, with rainfall from the start of the year to mid-April down 10-40 per cent from the long-term average nationwide. River flows and water levels in several basins have fallen to record lows for the period.
“These are early warning signs of potential water shortages from the start of the dry season,” the ministry said, adding that temperatures are likely to rise above normal, with more frequent and intense heatwaves than in 2025 if El Niño develops as forecast.
Rainfall during the 2026 dry season is expected to decline further, particularly from late 2026 to early 2027, with reductions of 25-50 per cent. The rainy season may also end earlier than usual, while water resources across river basins are likely to continue decreasing.
Major reservoirs, especially on the Da River system, could see inflows from May to July fall by 10-25 per cent below average, heightening risks to downstream water supply and energy security due to reduced cross-border flows and domestic rainfall.
The ministry warned of a high risk of drought and saltwater intrusion, particularly in the south-central region, Central Highlands and the Mekong Delta, with widespread water shortages possible in early 2027.
Despite lower overall rainfall, short bursts of extreme rain may still trigger flash floods, landslides and urban flooding. Storm activity in the East Sea is expected to be below average, though strong, erratic systems may still cause significant impacts.
Authorities said they would continue closely monitoring weather patterns, water resources and hazardous conditions to provide timely forecasts and warnings for government response.