Thailand's rainy season begins, expected to last until mid-October

The department also forecasts intermittent dry spells and one to two tropical storms during this period.

Rainy season timeline

• Early season (May–July): Northern Thailand is expected to receive 5–10% more rainfall than average.
• Late June to early July: Dry spells may occur in the North, Northeast and upper Central regions.
• Late season (August–October): Rainfall will generally be close to average, except for the eastern coast of the South, which may see around 10% less rainfall than usual.

From August to October, heavy rainfall and tropical storms are likely, with one or two storms expected to impact the North and Northeast.

The El Niño–La Niña phenomenon has now reached a neutral phase and is expected to remain stable through September to November. As a result, rainfall is likely to be better distributed and slightly above average overall this year.

15-day forecast (May 15–29)

May 15:

The rainy season officially begins. Southern winds are still mixing in, bringing scattered showers and ongoing rainfall.

May 15–17:

Widespread rain is expected across the country, with heavy rainfall in some areas. This is due to the strengthening southwest monsoon and a low-pressure cell over the Andaman Sea.

Residents in the western parts of the North (Tak and Mae Hong Son), Central, Eastern and Andaman coastal Southern regions are advised to be cautious of accumulated rainfall, which could cause flash floods and runoff.

May 18–22:

The monsoon may weaken slightly, but afternoon to evening showers will continue in line with prevailing winds.

May 23–28:

The monsoon is expected to strengthen again, leading to increased rainfall and heavy showers in the upper part of the country. Ongoing monitoring is advised.

The TMD noted that during the early phase of the rainy season, wind patterns may fluctuate. Thunderstorms, gusty winds, and moderate rainfall can occur at various times of the day. Once the season progresses, rain will mostly fall in the afternoon and evening.

People are advised to carry umbrellas or raincoats when going outdoors and to drive carefully, showing consideration for other road users.

Additionally, during the expected dry spell in late June to early July, areas with low rainfall should prepare water reserves for domestic use, agriculture and consumption. Meanwhile, regions experiencing repeated rainfall should be alert to potential flooding, the department added.