The Thai Meteorological Department (TMD) has issued a weather warning for northern Thailand, and greater Bangkok, as a high-pressure system from China interacts with moisture-laden winds to create a risk of severe thunderstorms and isolated hail.
According to the forecast for May 9, 2026, a high-pressure system, or cool air mass from China, has moved in to cover the Northeast and the South China Sea. This system is interacting with southerly and southeasterly winds that are bringing moisture from the Gulf of Thailand into the northern parts of the country, where daytime temperatures remain high.
The northern and central regions are expected to be the most affected, with thunderstorms forecast for 70% of the area. Residents in provinces such as Chiang Mai, Chiang Rai, Mae Hong Son and Nakhon Sawan have been warned to prepare for heavy downpours and the possibility of hail.
In and around Bangkok, the weather will remain hot during the day, followed by a 60% chance of thunderstorms. The TMD warns that these storms may be accompanied by strong winds and heavy localised downpours, with maximum temperatures reaching up to 38°C.
The Southern region is also facing increased rainfall due to strengthening easterly winds across the Gulf of Thailand. Both the East and West coasts of the South are expected to see rain over 60% of their areas, with heavy falls in provinces like Phuket, Krabi and Surat Thani.
Mariners have been advised to exercise caution, as waves in the Gulf of Thailand and the Andaman Sea will average one metre, but can surge to over two metres in areas experiencing active thunderstorms.
Public safety remains a priority, with officials advising people to stay clear of large trees, unsecured billboards and flimsy structures during windstorms.
Those living in low-lying areas or near mountains are warned of potential flash floods and forest runoffs caused by accumulated rainfall.
Farmers are encouraged to take preventive measures to protect their crops and livestock from storm damage. Meanwhile, air quality in the north of the country is reported to be in the good to moderate range, as the rain continues to help wash away dust and smoke particles.
