The 24-hour forecast is for heavy isolated downpours across the lower North, Central Region including Greater Bangkok, East, and South.
The department warned people to beware of flash floods, especially along foothills, near waterways and in low-lying areas.
Waves in the upper Gulf of Thailand and Andaman Sea will be 1-2 metres, rising higher in thunderstorms. Ships have been advised to proceed with caution and keep off thundershowers.
The severe weather is being produced by a low-pressure cell in the upper Andaman and a monsoon trough across the upper South.
The department issued separate forecasts for each region.
North:
- Cool morning with scattered thundershowers in upper North.
- Isolated heavy rain in Tak, Sukhothai, Kamphaeng Phet, Phichit and Phetchabun.
- Minimum temperature of 21-24C, maximum of 29-32C. Falling to 9-16C on mountaintops.
- Easterly winds 10-15kph.
Northeast:
- Scattered thundershowers in Loei, Nong Khai, Bueng Kan, Nong Bua Lamphu, Udon Thani, Kalasin, Khon Kaen, Maha Sarakham, Chaiyaphum, Nakhon Ratchasima, Buri Ram and Surin
- Minimum temperature 21-23C, maximum 30-34 °C. Falling to 14-18C on mountaintops
- Southeasterly wind 10-20kph
Central:
- Widespread thundershowers and isolated heavy rain in Nakhon Sawan, Uthai Thani, Chai Nat, Ayutthaya, Suphanburi, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Songkhram and Samut Sakhon
- Minimum temperature 23-25C, maximum 30-33C
- Southeasterly wind 10-25 km/hr
East:
- Scattered thundershowers and isolated heavy rain in Chachoengsao, Chonburi, Rayong, Chanthaburi and Trat.
- Minimum temperature 23-25C, maximum 30-33C.
- Southeasterly wind 15-35kph.
- Waves 1-2 metres, rising in thundershowers.
South (east coast):
- Scattered thundershowers and isolated heavy rain in Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani, Nakhon Si Thammarat and Narathiwat.
- Minimum temp 23-25C, maximum 30-33C.
- Surat Thani upwards: Variable winds 15-35kph.
- Wave height 1-2 metres and above 2 metres in thundershowers.
- Nakhon Si Thammarat downwards: Southwesterly wind 15-30kph.
- Waves 1 metre, rising in thundershowers.
South (west coast):
- Scattered thundershowers and isolated heavy rain in Ranong, Phangnga, Phuket, Krabi and Satun.
- Minimum temp 22-25C, maximum 30-33C.
- Southwesterly wind 15-35kph.
- Waves 1-2 metres, rising in thundershowers.
Greater Bangkok:
- Widespread thundershowers and isolated heavy rain.
- Minimum temperature 24-25C, maximum 30-32C.
- Southeasterly wind 10-20kph.
