BANGKOK — 18 June 2026, Thailand’s Office of the National Water Resources (ONWR) has warned that a seasonal dry spell expected from late June to mid-July could become more severe and prolonged due to the influence of El Niño, prompting authorities to accelerate nationwide water management plans.
ONWR Secretary-General Chayan Muangsong said on 18 June that although Thailand is currently in the rainy season, weather monitoring conducted jointly with the Thai Meteorological Department and the Hydro-Informatics Institute indicates that the country will enter a period of reduced rainfall from late June through mid-July 2026.
The dry spell is considered a normal seasonal phenomenon, occurring when the monsoon trough shifts northward across southern China, temporarily reducing rainfall and its distribution across Thailand.
However, Chayan said the situation could intensify because the El Niño–Southern Oscillation (ENSO) has now transitioned into an El Niño phase. Climate models project that El Niño conditions will persist throughout the year, a relatively uncommon occurrence that can trigger widespread weather extremes.
Such conditions could bring heatwaves, drought and, in some areas, episodes of heavy rainfall and flooding, he said.
Deputy Prime Minister Songsak Thongsri has expressed concern over the situation and instructed ONWR to work closely with relevant agencies to closely monitor weather developments and prepare response measures aimed at minimizing impacts on the public.
According to ONWR, cumulative rainfall since the beginning of the year remains around 10% below the seasonal average. Despite lower overall rainfall, localized heavy downpours could still trigger flooding, flash floods and landslides in some areas.
Authorities have therefore been ordered to strictly implement the government’s nine measures for the 2026 rainy season, while ensuring that equipment, machinery and personnel are ready to provide assistance when needed.
As of 17 June 2026, Thailand’s 35 major reservoirs held a combined 45.054 billion cubic meters of water, equivalent to 56% of total storage capacity. Usable water stood at 20.943 billion cubic meters, or 37% of capacity, which is 490 million cubic meters lower than the same period last year.
To manage water resources during the rainy season, ONWR has coordinated with the Royal Irrigation Department and the Electricity Generating Authority of Thailand (EGAT) to adjust reservoir discharge plans in line with actual conditions while maintaining targets under the national water management framework.
The agency is also encouraging all sectors to use water efficiently and conserve supplies, while maximizing water storage after the rainy season ends.
ONWR currently monitors and assesses weather and water conditions twice daily, in the morning and evening, to support water management planning and disaster warnings.
The agency is also evaluating the accuracy of warning systems with partner organizations and is developing a new rainfall forecasting model. The model will be proposed to the Subcommittee on Water Resources Management and is expected to improve runoff analysis and forecasts of flood- and landslide-prone areas.
