The Department of Meteorology has issued a seven-day forecast for June 21–27, 2029, warning of increasing rainfall across Thailand. From June 25–27, heavy rain is expected to cover 60–70% of the country, raising risks of flash floods, forest runoff, and overflowing riverbanks, particularly in low-lying areas and near mountain slopes.
Weather Outlook and Regional Impact
The transition in weather patterns is driven by the strengthening of the southwest monsoon over the Andaman Sea, Thailand, and the Gulf of Thailand, combined with a low-pressure cell moving over upper Vietnam. According to the department, the first half of the period (June 22–24) will see scattered thundershowers in upper Thailand and isolated heavy rain in the southern region. By June 25, the intensity of the monsoon will increase, resulting in more widespread precipitation across all regions.
Did You Know?
The weather intensity is expected to shift significantly between June 24 and June 25, with rainfall probability in regions like the North, Northeast, and Central Thailand jumping from 20–40% to 60–70% as the low-pressure system influences the country.
Marine Conditions and Safety Warnings
Rough seas are expected in the Andaman Sea and the Gulf of Thailand as monsoon winds gain strength. For the period of June 25–27, wave heights in the upper Andaman Sea are projected to reach approximately 2 meters, while the lower Andaman and upper Gulf will experience waves between 1–2 meters. The Department of Meteorology advises that in areas affected by thundershowers, waves may exceed 2 meters. Mariners are urged to exercise caution and avoid navigating through storm-affected zones throughout the week.
Expert Insight: Understanding the Risks
Expert Insight: The rapid escalation of rainfall percentages from 40% to 70% within a 48-hour window indicates a shift in atmospheric stability. For residents in mountainous or low-lying areas, the primary concern is not just the total volume of rain, but the “accumulated rainfall” mentioned in the report. When ground saturation occurs, the risk of flash flooding and forest runoff becomes localized and unpredictable, making early awareness of local water levels critical for safety.
Regional Forecast Summary
- Northern, Northeastern, and Central Regions: Rainfall will increase to 60–70% coverage with heavy rain expected starting June 25. Temperatures will range from 22°C to 37°C.
- Eastern Region: Similar to the interior, coverage will reach 60–70% by the end of the week, with wind speeds increasing up to 35 km/hr.
- Southern Region (East and West Coasts): The West Coast faces more severe conditions, with wave heights expected to reach 2 meters near Phuket from June 25 onward.
- Bangkok and Vicinity: Residents should prepare for a rise in rain to 60–70% coverage starting June 25, with temperatures peaking at 36°C.
Frequently Asked Questions
Which areas are most at risk for flash floods?
The Department of Meteorology identifies areas near mountain slopes, near natural waterways, and in low-lying regions as the primary zones of concern for flash floods and overflowing banks.
When will the weather be at its most intense?
The forecast indicates that conditions will worsen during the latter half of the week, specifically between June 25 and June 27, due to a strengthening monsoon and a low-pressure system.
What safety precautions should mariners take?
Vessels in the Andaman Sea and the Gulf of Thailand should proceed with caution and specifically avoid areas experiencing thundershowers where wave heights can exceed 2 meters.
How are you preparing your home or community for the expected increase in rainfall this week?