TMD warns of downpours and flash floods during October 21–25

The Thai Meteorological Department (TMD) warned on Tuesday (October 20, 2026) that heavy and accumulated rainfall could trigger flash floods, sudden runoff and landslides during October 21–25. Persistent rain is forecast in the South, while Bangkok and several other regions are expected to see increasing rainfall.

Weather Advisory No. 8 (267/2026), issued at 5pm Thai time, identifies particular risks on foothill slopes near waterways and in low-lying areas. Strong wind gusts could also affect some locations.

South faces persistent rain as Bangkok rainfall increases

The TMD forecasts continuous rain in southern Thailand during October 21–25, with heavy to very heavy downpours in isolated areas.

Rainfall is also expected to increase in the lower Northeast, lower Central region including Bangkok and surrounding provinces, the East and upper South, with gusty winds in some places, according to the TMD.

The TMD warned that heavy and prolonged rainfall could cause flash floods, fast-moving runoff, overflowing waterways and landslides. Residents should avoid routes prone to repeated flooding, particularly low-lying stretches where water could accumulate, and plan daily activities and journeys carefully.

A monsoon trough across the middle South and the southwest monsoon over the lower Andaman Sea are contributing to the wet conditions, the TMD said.

A high-pressure system, or cold air mass, from China is also expected to extend over the upper North, upper Northeast and South China Sea, bringing easterly winds over Thailand and the Gulf of Thailand, according to the department.

Thunderstorms could bring waves above three metres

Waves in thunderstorm areas of the Andaman Sea and Gulf of Thailand are forecast to exceed three metres during the warning period, the TMD said.

The TMD advised all vessels operating in both seas to proceed cautiously and avoid sailing through thunderstorms.

Daily forecast identifies heavy-rain areas for October 20–21

The TMD’s separate 24-hour forecast, valid from 6pm on October 20 to 6pm on October 21, identifies isolated heavy rain in the East and both southern coastal regions. The following provincial details apply to that period, rather than the entire October 21–25 warning.

• North: Thunderstorms are forecast over 10% of the region, mainly in Phitsanulok, Phetchabun and Phichit. Minimum temperatures will range from 21–25°C and maximum temperatures from 34–36°C, with easterly winds of 10–20km/h.
• Northeast: Thunderstorms are expected over 20% of the region, mainly in Nakhon Ratchasima, Buri Ram, Surin, Si Sa Ket and Ubon Ratchathani. Minimum temperatures will range from 23–24°C and maximum temperatures from 33–35°C, with northeasterly winds of 10–20km/h.
• Central region: Thunderstorms are forecast over 40% of the area, mainly in Phra Nakhon Si Ayutthaya, Suphan Buri, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Sakhon and Samut Songkhram. Minimum temperatures will range from 23–26°C and maximum temperatures from 33–36°C, with easterly winds of 10–20km/h.
• East: Thunderstorms are expected over 60% of the region, with isolated heavy rain in Chon Buri, Rayong, Chanthaburi and Trat. Minimum temperatures will range from 23–26°C and maximum temperatures from 33–35°C, with southeasterly winds of 10–30km/h. Waves will generally remain below one metre but exceed two metres in thunderstorms.
• South, east coast: Thunderstorms are forecast over 70% of the area, with isolated heavy rain in Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla, Pattani and Narathiwat. Minimum temperatures will range from 22–25°C and maximum temperatures from 30–34°C. Winds will be easterly at 15–30km/h from Surat Thani northwards and southeasterly at the same speeds from Nakhon Si Thammarat southwards. Waves will be about one metre, exceeding two metres in thunderstorms.
• South, west coast: Thunderstorms are expected over 70% of the area, with isolated heavy rain in Ranong, Phang Nga, Phuket, Krabi, Trang and Satun. Minimum temperatures will range from 24–25°C and maximum temperatures from 31–34°C. Winds will be easterly at 15–30km/h from Ranong northwards and southwesterly at the same speeds from Phang Nga southwards. Waves will be about one metre, exceeding two metres in thunderstorms.
• Bangkok and surrounding provinces: Thunderstorms are forecast over 60% of the area. Minimum temperatures will range from 26–27°C and maximum temperatures from 33–34°C, with southeasterly winds of 10–20km/h.

TMD schedules next advisory for 5am on October 21

The TMD said its next advisory would be issued at 5am on October 21. The October 20 evening bulletin was signed by Nattawut Dandee, deputy director-general acting as director-general.

Weather updates are available around the clock through the TMD’s website or by calling 02-399-4012, 02-399-4013 or 1182.