The Thai Meteorological Department (TMD) has issued a warning for southern Thailand, including major tourist islands, forecasting a surge in thunderstorms from Wednesday through Saturday.

These weather patterns, driven by easterly winds, signal the official start of the rainy season, which is expected to arrive around mid-May.

The affected region, stretching south of Bangkok across the Malay Peninsula and including major islands like Phuket, Samui, and Krabi, is likely to see heavy rainfall in specific areas.

The TMD reported via its website and Facebook page on Monday that easterly winds impacting the lower southern region will be the primary driver for this sudden increase in precipitation.

While early May 2026 has already seen a rise in rainfall across Thailand, the distribution remains uneven. Daytime temperatures continue to be hot to very hot, with afternoon and evening periods frequently interrupted by thunderstorms and occasional summer storms.

On May 5 – 6, the upper region of the country will experience scattered thunderstorms and gusty winds. This is caused by weak high pressure over the South China Sea and the northeast, interacting with prevailing southwesterly and southeasterly winds.

From May 7 – 9, these conditions are expected to intensify as a stronger high-pressure system moves in from China. This system will bring more robust easterly and southeasterly winds, leading to more frequent thunderstorms and gusty winds even as the heat persists. In Thailand’s south, this period will likely see widespread rain and heavy showers.

A brief reprieve is expected on May 10 – 11 as easterly winds weaken, leading to more isolated thunderstorm activity.

However, officials are urging the public to stay alert for potential hazards. Mariners, in particular, are advised to take extra precautions and avoid sailing during storm conditions.

The final transition into the rainy season across the country is predicted to occur between May 15 – 17. As the season approaches, farmers and the general public are encouraged to begin planning for water storage and to monitor weather updates closely for further developments.