Thailand's meteorological department has issued a heavy rain alert for 52 provinces through August 21, with very heavy downpours expected across the North, Northeast, Central, and Eastern regions that could trigger flash floods and overflow
On August 20, the Thai Meteorological Department forecast heavy rain in scattered areas across Thailand over the next 24 hours, with very heavy rainfall expected in parts of the North, Northeast, Central, and Eastern regions. A monsoon trough is passing through the upper North and upper Northeast, moving into a strong low-pressure system near Hainan Island in China, combined with a moderately strong southwest monsoon over the Andaman Sea and Gulf of Thailand.
Residents in affected areas are warned to watch for dangers from heavy to very heavy rainfall and accumulated precipitation, which may cause flash floods, overflowing streams, and riverbank overflow, particularly in foothill areas near water channels and low-lying zones. In the Andaman Sea's upper section and upper Gulf of Thailand, wave heights reach 2–3 meters, exceeding 3 meters during thunderstorms. In the lower Andaman Sea, waves are approximately 2 meters, exceeding 2 meters during thunderstorms. Boat operators are urged to navigate cautiously, avoid thunderstorm areas, and small boats in the upper Andaman should remain ashore.
The North will see thunderstorms in 80 percent of areas with heavy rain across Chiang Mai, Chiang Rai, Lampun, Lamphun, Phayao, Nan, Phrae, and Kamphaeng Phet, with very heavy rain in Mae Hong Son, Uttaradit, Sukhothai, Tak, Phichit, and Phetchabun. Temperatures range from 22–27 degrees Celsius minimum to 27–31 degrees maximum, with southwest winds at 10–20 kilometers per hour.
The Northeast will experience thunderstorms in 80 percent of areas with heavy rain across Nong Khai, Nong Bua Lamphu, Udon Thani, Chaiyaphum, Khon Kaen, Kalasin, Mukdahan, Maha Sarakham, Roi Et, Yasothon, Amnat Charoen, Nakhon Ratchasima, and Ubon Ratchathani, with very heavy rain in Loei, Bueng Kan, Sakon Nakhon, and Nakhon Phanom. Temperatures range from 22–25 degrees minimum to 26–32 degrees maximum, with southwest winds at 10–20 kilometers per hour.
The Central Region will see thunderstorms in 70 percent of areas with heavy to very heavy rainfall in Nakhon Sawan, Uthai Thani, Chai Nat, Lopburi, Saraburi, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Sakhon, and Samut Songkhram. Temperatures range from 23–26 degrees minimum to 29–33 degrees maximum, with southwest winds at 10–25 kilometers per hour.
The East will have thunderstorms in 70 percent of areas with heavy rainfall in Nakhon Nayok, Prachuap Khiri Khan, Sa Kaew, and Chanthaburi, and very heavy rain in Trat. Temperatures range from 23–28 degrees minimum to 30–33 degrees maximum, with southwest winds at 20–40 kilometers per hour. Sea waves are 2–3 meters high, exceeding 3 meters during thunderstorms.
The South's eastern coast will see thunderstorms in 40 percent of areas with heavy rain in Phetchaburi and Prachuap Khiri Khan. Temperatures range from 23–27 degrees minimum to 32–36 degrees maximum.