

The Thai Meteorological Department (TMD) has issued a weather forecast for Tuesday, August 18. It comes alongside a separate warning of heavy to very heavy rain running through August 21 across the upper North and upper Northeast.
A monsoon trough lies across upper Laos and into a low-pressure cell over upper Vietnam. A strong southwest monsoon continues to sweep the Andaman Sea, mainland Thailand and the Gulf of Thailand.
TMD has warned residents in the affected areas to watch for flash floods, forest runoff and overflowing riverbanks, particularly near foothills, waterways and low-lying land.
Wave heights in the upper Andaman Sea are forecast at 2 to 3 metres, rising above 3 metres in thundery areas. Vessels in the Andaman Sea and Gulf of Thailand are advised to navigate with caution and avoid thundery zones. Small boats in the upper Andaman have been told to stay ashore for now.

North
Thunderstorms will cover 60 to 70% of the region, with isolated heavy rain in Mae Hong Son, Chiang Rai and Tak. Temperatures will range from 22 to 28 degrees Celsius at the low end and 32 to 36 at the high end. Southwesterly winds will blow at 10 to 20 kilometres per hour.
Northeast
Storms will affect 60 to 70% of the region, with isolated heavy to very heavy rain in Nong Khai, Nakhon Phanom and Ubon Ratchathani. Lows will sit between 24 and 26 degrees Celsius, with highs of 33 to 36 degrees Celsius. Southwesterly winds will blow at 10 to 20 kilometres per hour.
Central
Storms are expected over 40 to 60% of the region, mainly in Kanchanaburi and Saraburi. Temperatures will range from 24 to 27 degrees Celsius overnight to 35 to 37 degrees Celsius during the day, with southwesterly winds of 10 to 25 kilometres per hour.
East
Heavy to very heavy rain is expected in Nakhon Nayok, Chanthaburi and Trat, with thunderstorms covering 60 to 70% of the region. Lows of 22 to 26 degrees Celsius and highs of 31 to 35 degrees Celsius are forecast, with southwesterly winds of 20 to 35 kilometres per hour. Waves will reach around 2 metres, rising higher in thundery areas.
South East Coast
Isolated thunderstorms will cover 40 to 60% of the region, mainly in Prachuap Khiri Khan, Chumphon and Narathiwat. Temperatures will range from 23 to 26 degrees Celsius at night to 33 to 36 degrees Celsius by day, with southwesterly winds of 15 to 35 kilometres per hour. Waves of 1 to 2 metres are expected, rising above 2 metres in thundery areas.
South West Coast
Scattered thunderstorms will affect 40 to 60% of the region, mainly in Ranong, Phang Nga and Trang. Lows of 23 to 25 degrees Celsius and highs of 31 to 34 degrees Celsius are expected. From Phang Nga northwards, southwesterly winds of 20 to 40 kilometres per hour will bring waves of 2 to 3 metres, rising above 3 metres in thundery areas. From Phuket southwards, winds of 15 to 35 kilometres per hour will bring waves of 1 to 2 metres, rising above 2 metres in thundery areas.

Bangkok and Vicinity
Thunderstorms will cover 60 to 70% of the capital and surrounding areas. Temperatures will range from 25 to 28 degrees Celsius overnight to 32 to 35 degrees Celsius during the day, with southwesterly winds of 10 to 25 kilometres per hour.
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Sources: Thai Meteorological Department · The Nation
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