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Thailand's Department of Disaster Prevention and Mitigation (DDPM) issued a warning on August 29, alerting 51 provinces nationwide to closely monitor the risk of flash floods, forest run-off and inundation from August 29 to September 2, as rainfall across the country was expected to increase significantly over the coming days. At the same time, the Thai Meteorological Department (TMD) issued a warning for the same period, stating that upper Thailand — mainly the North and Northeast — would see heavy to very heavy rain, with a heightened risk of flash floods and sudden run-off from forested areas. The five-day warning comes at a critical juncture of Thailand's rainy season, prompting government agencies at every level and the public to raise their alertness and prepare accordingly.

According to Thailand's National Disaster Warning Center, the 51-province warning places particular emphasis on the North, Northeast and East. In the North, the high-risk provinces are Mae Hong Son, Chiang Mai, Chiang Rai and Tak; in the Northeast they are Bueng Kan, Nakhon Phanom and Sakon Nakhon; while in the East, Chanthaburi and Trat are flagged as priority areas. Authorities have instructed local disaster-prevention offices to disseminate warnings through all available channels, including warning towers and the Cell Broadcast mobile alert system, so that residents living near waterways, foothills and low-lying areas can learn of the risk in time and prepare to evacuate or take protective measures.

According to reporting by The Nation Thailand on August 29, within this nationwide warning, 17 provinces in upper Thailand have been specifically identified as facing the highest risk of flash floods, mudslides and landslides — forming the most severe-risk subset within the broader 51-province list. Most of these provinces are concentrated in the mountainous North and in Northeastern areas bordering Laos along the Mekong River, where steep terrain, dense forest cover and fast-draining watersheds mean that sustained heavy rain can rapidly trigger flash floods and landslides, posing a significant threat to communities living near the foothills. Disaster-prevention authorities have ordered local offices in these 17 provinces to increase the frequency of monitoring patrols and to pre-position personnel and equipment.

The TMD explained that the cause of this round of heavy rain is a monsoon trough continuing to shift southward, crossing upper Thailand's North and Northeast before extending into a low-pressure area off the coast of upper Vietnam and the Gulf of Tonkin, while a relatively strong southwest monsoon continues to prevail over the Andaman Sea, Thailand and the Gulf of Thailand — the combination of the two driving up rainfall intensity. The TMD forecasts that from August 29 to September 2, the upper North, upper Northeast and East of Thailand will experience heavy to very heavy rain, with isolated areas possibly seeing extremely heavy downpours; accumulated rainfall could be sufficient to trigger flash floods, overflowing waterways and landslides, particularly along waterways near foothills and low-lying land. The TMD also issued a parallel maritime warning, noting that waves in parts of the Andaman Sea and Gulf of Thailand could reach 2-3 metres, and advised vessels and fishermen to exercise caution.

In response to this warning, Thailand's Center for Disaster Prevention and Mitigation Coordination (CDPMC) has instructed DDPM offices in high-risk areas to strengthen coordination, prepare in advance for possible flooding and landslides, and maintain round-the-clock monitoring throughout the warning period. Local agencies have been directed to closely track real-time changes in rainfall, river levels and reservoir storage, and to activate warning-response mechanisms immediately upon detecting any abnormal signs, while sharing information with related agencies such as the TMD and the Royal Irrigation Department to ensure warning instructions reach the grassroots level and affected communities as quickly as possible.

Thai authorities have also called on the public — particularly those living near foothills, low-lying areas and along waterways — to remain alert, closely follow the latest official weather bulletins, and follow the guidance of local disaster-prevention agencies, whether that means taking protective measures or evacuating if necessary. The TMD has advised the public to plan travel and outdoor activities carefully during the warning period, avoid flooded roads or mountainous routes, and check the latest forecasts via the TMD website tmd.go.th or by calling the hotlines 0-2399-4012-13 and 1182, both available 24 hours a day.

Since August, Thailand has issued several similar warnings for heavy rain and flash floods. From August 18 to 21, the DDPM warned 39 provinces of flash-flood risk, and before that it issued a single warning covering as many as 61 provinces for flash floods, landslides and rough seas, spanning most of the country. Earlier, in early June, the DDPM also warned six southern provinces of floods and landslides. The frequency of these warnings reflects how, throughout this year's rainy season, Thailand has been repeatedly affected by the monsoon trough shifting back and forth and by fluctuations in the strength of the southwest monsoon, producing uneven and highly variable rainfall distribution — underscoring the need for disaster-prevention agencies to maintain a heightened state of readiness through the middle and later stages of the rainy season.

As of this report on August 30, no official reports of casualties or property damage tied specifically to this August 29-September 2 warning period had been recorded. The advisory therefore remains, in essence, a precautionary weather warning rather than a report of a disaster that has already occurred. Even so, given the complex terrain of upper Thailand and the fact that some of the flagged provinces have repeatedly experienced flash floods in the past, authorities continue to stress that vigilance should not be relaxed until the entire warning window has passed, and that the public should keep following the latest updates from the TMD and the DDPM.

Notably, several northern provinces on this warning list are no strangers to such risks — mountainous northern provinces such as Chiang Rai and Mae Hong Son have repeatedly experienced flash floods and road closures during past rainy seasons. As a result, local disaster-prevention offices have been pressing subordinate districts and sub-districts to inspect drainage systems, dredge waterways and test early-warning broadcast equipment both before and during this warning period, in an effort to minimize the potential impact of heavy rain. Analysts note that Thailand's rainfall patterns in recent years have shown greater within-season volatility, with short bursts of intense rain alternating with periods of dryness, meaning disaster-prevention agencies can no longer rely solely on historical experience to assess risk and must instead continuously adjust their response plans based on the TMD's rolling forecasts and real-time monitoring data.