TMD puts northern Thailand on alert as monsoon brings heavy rain

The Thai Meteorological Department (TMD) forecast a new round of rain in its weather update for Tuesday (July 21, 2026), with the North expected to have the country’s highest rainfall coverage at 60%.

Bangkok and its vicinity were expected to see thunderstorms mainly from the afternoon into the evening.

Over the next 24 hours, thunderstorms were forecast in some areas of Thailand, with isolated heavy rain in the North as the southwest monsoon over the Andaman Sea, Thailand and the Gulf of Thailand began to strengthen.

People in the North were advised to beware of hazards from heavy and accumulated rainfall.

Wind and wave conditions in the upper Andaman Sea and the upper Gulf of Thailand were forecast to be moderate, with wave heights of 1–2 metres.

Waves in the lower Andaman Sea were expected to be about 1 metre, rising above 2 metres in thundery areas.

Mariners were advised to proceed with caution and avoid sailing in areas with thunderstorms.

Weather forecast for Thailand from 6am Tuesday (July 21) to 6am Wednesday (July 22)

Bangkok and vicinity

• Thunderstorms in 30% of the area, mainly from the afternoon into the evening.
• Minimum temperatures of 27–28°C and maximum temperatures of 34–37°C.
• Southwesterly winds at 10–20 km/h.

North

• Thunderstorms in 60% of the area, with isolated heavy rain in Mae Hong Son, Chiang Mai, Chiang Rai, Phayao, Nan, Lamphun, Lampang and Tak.
• Minimum temperatures of 21–27°C and maximum temperatures of 28–34°C.
• Southwesterly winds at 10–20 km/h.

Northeast

• Thunderstorms in 30% of the area, mainly in Loei, Nong Khai, Bueng Kan, Sakon Nakhon, Nakhon Phanom, Chaiyaphum and Nakhon Ratchasima.
• Minimum temperatures of 23–25°C and maximum temperatures of 32–37°C.
• Southwesterly winds at 10–20 km/h.

Central region

• Thunderstorms in 30% of the area, mainly in Kanchanaburi, Uthai Thani, Nakhon Sawan, Lop Buri and Saraburi.
• Minimum temperatures of 23–26°C and maximum temperatures of 33–37°C.
• Southwesterly winds at 10–20 km/h.

East

• Thunderstorms in 30% of the area, mainly in Nakhon Nayok, Prachinburi, Rayong, Chanthaburi and Trat.
• Minimum temperatures of 23–28°C and maximum temperatures of 33–37°C.
• Southwesterly winds at 15–35 km/h.
• Wave heights of 1–2 metres, rising above 2 metres in thundery areas.

South (east coast)

• Thunderstorms in 30% of the area, mainly in Nakhon Si Thammarat, Phatthalung, Songkhla, Pattani, Yala and Narathiwat.
• Minimum temperatures of 23–26°C and maximum temperatures of 33–36°C. Southwesterly winds at 15–30 km/h.
• Wave heights of about 1 metre, exceeding 1 metre offshore and rising above 2 metres in thundery areas.

South (west coast)

• Thunderstorms in 40% of the area, mainly in Phuket, Krabi, Trang and Satun.
• Minimum temperatures of 23–25°C and maximum temperatures of 32–34°C.
• From Phang Nga northwards, southwesterly winds at 15–35 km/h, with wave heights of 1–2 metres and above 2 metres in thundery areas.
• From Phuket southwards, southwesterly winds at 15–30 km/h, with wave heights of about 1 metre and above 2 metres in thundery areas.