Heavy rain and dangerous seas affecting parts of Thailand

Timeline

1. August 29, 2026

   Thailand's disaster agency (DDPM) warned 51 provinces (up from 27) of flash flood, forest runoff and inundation risk from 29 August to 2 September as monsoon rainfall increases nationwide, with the highest risk in the North (Mae Hong Son, Chiang Mai, Chiang Rai, Tak), Northeast (Bueng Kan, Nakhon Phanom, Sakon Nakhon) and East (Chanthaburi, Trat); Nan was not named among the acute-risk provinces, with floodwaters there remaining below the riverbank and recovery/cleanup nearly complete. The Andaman Sea and upper Gulf outlook was unchanged, with waves of 2-3 metres (above 3m in thunderstorm areas) continuing to affect the Ranong-Phang Nga-Phuket coast; small boats are advised to remain ashore.

   Source

2. August 27, 2026

   Thailand's Meteorological Department warned 27 provinces of heavy rain over the following 24 hours, concentrated in the eastern region, western North and Central Thailand, with isolated heavy falls in Ranong and Phang Nga; Andaman Sea waves were forecast at 2-3 metres, exceeding 3 metres in thunderstorm areas, with small boats told to remain ashore. Nan was not named in this alert, indicating the flood-hit province is no longer under an acute rain warning.

   Source

3. August 24, 2026

   The confirmed Nan flood death toll rose to four (three civilians and one relief official), up from two previously. Among the dead is Suphamon Ratanjit, 47, head of disaster operations for the Red Cross-affiliated Friend Support Foundation, who died suddenly of a suspected health-related collapse on the morning of 24 August after working continuously on flood relief in Pua district. Separately, Thailand's government publicly refuted social-media claims that the death toll had reached over 100, calling it fabricated content and confirming four as the verified figure.

   Source

4. August 23, 2026

   Prime Minister Anutin ordered agencies to accelerate Nan's flood recovery, issue early warnings to downstream areas including Sukhothai and communities along the Yom River, deploy pumps, and restore infrastructure. Damage surveys across the seven affected districts (23,827 households, roughly 67,129 people) were due by 26 August, with compensation payments to be completed by 1 September; initial assistance of 6,700 baht per household was authorized.

   Source

5. August 23, 2026

   Thailand's meteorological department extended heavy rain and flash-flood warnings through 23 August across the North (including Nan), Northeast, Central and Eastern regions. In the Andaman Sea north of Phang Nga, southwest winds of 20-40 km/h are producing 2-3 metre waves, rising above 3 metres in thunderstorms; small boats have been told to stay ashore. Tropical Storm Narra is expected to make landfall in southern China on 24-25 August without directly hitting Thailand. Travelers on the Andaman coast should avoid small-boat excursions and check forecasts before beach or island activities.

   Source

6. August 23, 2026

   Nan's floodwaters have receded, revealing heavy mud deposits in homes and roads. Over 700 soldiers and military engineers have been deployed to clear debris and assess damaged buildings, and Prime Minister Anutin Charnvirakul visited Nan Provincial Hall on 23 August to review recovery efforts and approve further central-government support. The confirmed death toll remains at two, with no new fatalities reported, and authorities have promised maximum compensation for victims' families. Recovery is underway but full damage/displacement totals have not yet been released.

   Source

7. August 22, 2026

   Nan's flood extent has surpassed 2,793 hectares across three districts per satellite radar data (GISTDA), with heavy rainfall directly affecting seven districts between 19-21 August; Nan recorded 277mm of rain in a single day. Two fatalities have now been confirmed: a bedridden patient swept away in Pua district and a man (around 45) in Tha Wang Pha. Roughly 66,000 people across the northern region have been severely affected and more than 21,000 households damaged; in Pua district alone, about 16,000 people (8,000 households across 60 villages in seven subdistricts) were affected. Seven rural roads and bridges remain impassable with water depths of 50-170cm. Nan Hospital was closed through 22 August, with emergencies handled at a field facility; clean-up in Pua district has begun, with an estimated 3,800 tonnes of waste generated. Floodwaters began stabilising and receding in several areas by 21-22 August as authorities closely monitor the Nan River basin, though more rain is forecast for Sunday (23 August).

   Source

8. August 21, 2026

   Nan province has been declared a disaster zone. Flash floods that swept through Pua district on 19 August, triggered by more than 110mm of overnight rain, killed one person, cut major roads and affected four districts, 21 subdistricts and 72 villages; more than 27,000 people lost power after high-voltage poles fell. Public, private and volunteer teams deployed boats, jet skis and a helicopter to evacuate at-risk residents, with a 24-hour watch maintained. Forecasters expect conditions to improve from 21-22 August as the Nan River drops below its banks, though similar flash-flood and landslide risk continues to be flagged across northern provinces including Chiang Rai, Chiang Mai and Phayao through at least 21 August.

   Source

9. August 20, 2026

   Authorities ordered Nan, Phayao and Lamphun provinces to urgently prepare for flooding and flash floods, including activating 24-hour Cell Broadcast alerts and placing a KA-32 rescue helicopter on standby. The flash-flood warning covering 39 provinces (issued 18 August) remains in effect through 21 August, with orange-alert areas expecting over 90mm of rain and Tak's Tha Song Yang/Umphang districts under a red alert (over 200mm over three days). Wave heights in the upper Andaman Sea are forecast at 2-3m, rising above 3m in thundery areas; small boats there are told to remain ashore for now.

   Source

10. August 18, 2026

    A flash-flood warning now covers 39 provinces across the North, Northeast and Central regions from 18-21 August, up from 27 provinces on 14 August, driven by a monsoon trough and a strong southwest monsoon bringing heavy to very heavy rainfall. Orange-alert areas are forecast to receive more than 90mm of rain, while yellow-alert areas could see 35-90mm; Tak's Tha Song Yang and Umphang districts have been placed under a red alert with more than 200mm forecast over three days. Thunderstorms are forecast across 70% of the northern region, with heavy rain in Mae Hong Son, Chiang Mai, Chiang Rai, Lampang, Phayao, Nan, Uttaradit, Tak and Phetchabun. For the first time this cycle, three southern tourist provinces - Ranong, Phang Nga and Phuket - are on alert for rough seas with waves potentially exceeding 3 metres. Authorities are preparing response teams, monitoring water levels, and are ready to close natural attractions such as caves and waterfalls if conditions become dangerous.

    Source

11. August 14, 2026

    TMD's heavy-rain warning remains in effect through 18 August across the North, upper Northeast, Central, East and western South, driven by a monsoon trough over upper Laos/Vietnam and a strong southwest monsoon. A four-day flood warning now covers 27 provinces nationwide. In Nakhon Phanom, the Mekong River continued rising toward its 10-14 August peak, raising overflow risk in low-lying areas; some regional media additionally flagged flood risk for northern provinces including Chiang Rai. No disruption has been confirmed at major tourist hubs (Phuket, Bangkok, Chiang Mai Old City); land travel is not generally affected, but flash-flood and landslide risk continues near waterways and foothills.

    Source

12. August 13, 2026

    TMD forecast isolated to locally heavy rain continuing in the North, upper Northeast, Central and East over the following 24 hours, driven by the monsoon trough and a rather strong southwest monsoon covering the Andaman Sea, Thailand and the Gulf of Thailand. In Lampang, four consecutive days of heavy rain triggered flash floods in eight villages, damaging homes, farmland and pig sheds. Rivers could also overflow their banks in the Northeast; check ferry and boat operators before travelling on the Andaman coast.

    Source

13. August 12, 2026

    No new TMD strong-wind/wave bulletin has been issued since No.12 (9 August) - three days without an update - reinforcing that maritime conditions in the upper Andaman Sea and upper Gulf have eased. Isolated heavy rain and flash-flood risk continue nationwide, especially in the North, Northeast and East, under the ongoing southwest monsoon; land travel is not generally affected.

    Source

14. August 11, 2026

    TMD's most recent strong-wind and wave bulletin (No.12, issued 9 August) covered impacts only through 9 August, and no newer Andaman Sea/upper Gulf wave warning has been issued as of 11 August, suggesting maritime conditions have eased. Isolated heavy rain and flash-flood risk continue in parts of the North, Northeast, Central and East under the ongoing southwest monsoon; check ferry and boat operators before travelling.

    Source

15. August 10, 2026

    Isolated heavy rain remains possible, with 2-3 m waves in the upper Andaman Sea and upper Gulf and higher waves in thunderstorms. Small boats should remain ashore; ferry and excursion services may be affected. Check operators before travelling.

    Source

16. August 8, 2026

    Strong southwest monsoon conditions continue, with 2-3 m waves and higher waves in thunderstorms. Small boats in the upper Andaman Sea and upper Gulf should remain ashore; ferry and excursion schedules may be affected.

    Source

17. August 7, 2026

    Thailand's Meteorological Department warns of heavy to very heavy rain, flash floods and landslides on 7 August. Strong waves are expected in the upper Andaman Sea and upper Gulf, so ferry, diving and boat services may be disrupted; check operators before travelling.

    Source