TMD warns of rain across 60-70% of Thailand as Bangkok hits 37°C

The Thai Meteorological Department (TMD) forecast on Thursday (May 21, 2026) that Thailand would continue to see rainfall over the next 24 hours, with heavy rain in some areas and very heavy rain in parts of the South’s west coast.

The conditions were caused by a fairly strong southwest monsoon covering the upper Andaman Sea and Thailand, together with a low-pressure cell over the lower North and upper Northeast.

People were advised to beware of heavy to very heavy rain and accumulated rainfall, which could trigger flash floods and run-off, especially on foothills near waterways and in low-lying areas, and to take care of their health during changing weather conditions.

Waves in the upper Andaman Sea were fairly strong, reaching 2–3 metres and rising above 3 metres in thundershowers.

In the lower Andaman Sea and the upper Gulf of Thailand, waves were about 2 metres high and above 2 metres in thundershowers.

Mariners in these areas were advised to navigate with caution and avoid sailing in thundershowers, while small boats in the upper Andaman Sea should stay ashore.

Forecast for Thailand from 6am on Thursday (May 21), to 6am on Friday (May 22)

North

• Thunderstorms are forecast in 60% of the region, with isolated heavy rain in Nan, Uttaradit, Sukhothai, Tak, Kamphaeng Phet, Phichit, Phitsanulok and Phetchabun.
• Minimum temperature: 23–26°C
• Maximum temperature: 32–37°C
• Southwesterly winds: 10–20km/h

Northeast

• Thunderstorms are forecast in 60% of the region, with isolated heavy rain in Loei, Nong Khai, Bueng Kan, Nong Bua Lamphu, Udon Thani, Sakon Nakhon and Nakhon Phanom.
• Minimum temperature: 23–25°C
• Maximum temperature: 31–35°C
• Southwesterly winds: 10–20km/h

Central region

• Thunderstorms are forecast in 60% of the region, with isolated heavy rain in Nakhon Sawan, Uthai Thani, Chai Nat, Suphan Buri, Kanchanaburi and Ratchaburi.
• Minimum temperature: 24–27°C
• Maximum temperature: 33–36°C
• Southwesterly winds: 10–20km/h

East

• Thunderstorms are forecast in 60% of the region, with isolated heavy rain in Rayong, Chanthaburi and Trat.
• Minimum temperature: 24–29°C
• Maximum temperature: 32–36°C
• Southwesterly winds: 20–35km/h
• Waves are forecast to be about 2 metres high and above 2 metres in thundershowers.

South (east coast)

• Thunderstorms are forecast in 60% of the region, with isolated heavy rain in Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung and Songkhla.
• Minimum temperature: 24–26°C
• Maximum temperature: 31–36°C
• From Surat Thani northwards: Southwesterly winds of 20–35km/h. Waves are forecast to be about 2 metres high, rising above 2 metres offshore and in thundershowers.
• From Nakhon Si Thammarat southwards: Southwesterly winds of 15–35km/h. Waves are forecast at 1–2 metres, about 2 metres offshore, and above 2 metres in thundershowers.

South (west coast)

• Thunderstorms are forecast in 70% of the region, with heavy rain in many areas of Phuket, Krabi, Trang and Satun, and very heavy rain in some areas of Ranong and Phang Nga.
• Minimum temperature: 23–26°C
• Maximum temperature: 27–30°C
• From Phuket northwards: Southwesterly winds of 20–40km/h. Waves are forecast at 2–3 metres and above 3 metres in thundershowers.
• From Krabi southwards: Southwesterly winds of 20–35km/h. Waves are forecast to be about 2 metres high and above 2 metres in thundershowers.

Bangkok and the surrounding provinces

• Thunderstorms are forecast in 40% of the area.
• Minimum temperature: 26–28°C
• Maximum temperature: 35–37°C
• Southwesterly winds: 10–20km/h