Heavy rain across Thailand as southwest monsoon remains rather strong

The Thai Meteorological Department (TMD) forecast thunderstorms across up to 70% of several regions on Thursday (July 30, 2026), as a monsoon trough lay across the North and Northeast.

In its 24-hour outlook, isolated very heavy rain was expected in the North, East and along the southern west coast.

Isolated heavy rain was forecast in the Northeast, Central region, Bangkok and its vicinity, and along the southern east coast.

A rather strong southwest monsoon was also prevailing over the Andaman Sea, Thailand and the Gulf of Thailand.

The public was advised to remain alert to heavy to very heavy rain and accumulated rainfall, which could cause flash floods and run-off, particularly on foothill slopes near waterways and in low-lying areas.

Marine conditions in the upper Andaman Sea were rather strong, with waves of 2–3 metres and more than 3 metres during thunderstorms.

Waves in the lower Andaman Sea and upper Gulf of Thailand were around 2 metres, rising above 2 metres during thunderstorms.

Mariners were advised to proceed with caution and avoid areas affected by thunderstorms, while small boats in the upper Andaman Sea should remain ashore during this period.

Weather forecast for Thailand from 6am on Thursday (July 30) to 6am on Friday (July 31)

Bangkok and its vicinity

• Thunderstorms are forecast across 70% of the area, with isolated heavy rain.
• Minimum temperatures: 25–27°C.
• Maximum temperatures: 33–34°C.
• Southwesterly winds: 10–25 km/h.

North

• Thunderstorms are forecast across 70% of the region, with heavy rain in Mae Hong Son, Chiang Mai, Nan, Uttaradit, Tak, Kamphaeng Phet, Sukhothai, Phitsanulok and Phichit, and isolated very heavy rain in Phetchabun.
• Minimum temperatures: 22–26°C.
• Maximum temperatures: 30–35°C.
• Southwesterly winds: 10–20 km/h.

Northeast

• Thunderstorms are forecast across 60% of the region, with isolated heavy rain in Loei, Nong Khai, Bueng Kan, Nong Bua Lamphu, Udon Thani, Chaiyaphum, Khon Kaen, Nakhon Ratchasima, Buri Ram and Surin.
• Minimum temperatures: 23–25°C.
• Maximum temperatures: 30–33°C.
• Southwesterly winds: 10–20 km/h.

Central region

• Thunderstorms are forecast across 70% of the region, with isolated heavy rain in Nakhon Sawan, Uthai Thani, Saraburi, Phra Nakhon Si Ayutthaya, Kanchanaburi, Ratchaburi, Nakhon Pathom and Samut Sakhon.
• Minimum temperatures: 25–26°C.
• Maximum temperatures: 33–34°C.
• Southwesterly winds: 10–25 km/h.

East

• Thunderstorms are forecast across 70% of the region, with heavy rain in Prachin Buri, Sa Kaeo, Chachoengsao and Chon Buri, and isolated very heavy rain in Nakhon Nayok, Rayong, Chanthaburi and Trat.
• Minimum temperatures: 23–26°C.
• Maximum temperatures: 29–33°C.
• Southwesterly winds: 20–35 km/h.
• Waves: About 2 metres, rising above 2 metres during thunderstorms.

South (east coast)

• Thunderstorms are forecast across 60% of the region, with isolated heavy rain in Phetchaburi, Prachuap Khiri Khan, Chumphon and Surat Thani.
• Minimum temperatures: 22–26°C.
• Maximum temperatures: 29–33°C.
• Southwesterly winds: 15–35 km/h.
• Waves: About 1 metre, reaching 1–2 metres offshore and rising above 2 metres during thunderstorms.

South (west coast)

• Thunderstorms are forecast across 70% of the region, with heavy rain in Phang Nga, Phuket and Krabi, and isolated very heavy rain in Ranong.
• Minimum temperatures: 23–24°C.
• Maximum temperatures: 29–32°C.
• From Phang Nga northwards, southwesterly winds will reach 20–40 km/h, with waves of 2–3 metres, rising above 3 metres during thunderstorms.
• From Phuket southwards, southwesterly winds will reach 20–35 km/h, with waves of about 2 metres, rising above 2 metres during thunderstorms.