BANGKOK, THAILAND – Specialised aircraft continued flying weather-modification missions over Bangkok and several regions to reduce hazardous PM2.5 dust levels.
Weather modification to ease PM2.5 burden
The Royal Rainmaking and Agricultural Aviation Department, led by director-general Rachen Silparaya, carried out operations aimed at dispersing fine dust clouds before weak winds and poor air circulation could further deteriorate air quality. The agency said cloud-seeding flights would continue over Bangkok, surrounding provinces, and parts of the North and Northeast to reduce particulate pollution.
Measurements indicated that PM2.5 concentrations between 12 and 16 February were expected to range from moderate to levels already affecting health, classified in the yellow to orange bands.
Smog challenges in North and Northeast
Air-quality monitoring showed that fine-dust levels in Bangkok, neighbouring provinces, and parts of the North and Northeast fluctuated from medium to health-relevant levels, also graded yellow to orange. According to the authorities, northern regions faced additional problems because their basin-like topography favoured the build-up of air pollutants, while heat hotspots in western neighbouring countries and northwesterly winds could bring in extra pollution.
New bases and aircraft deployed
To tackle the situation, the department set up four weather-modification units in the districts of Hua Hin in Prachuap Khiri Khan, Rayong, Tak and Khon Kaen, with the operational plan to be adjusted from 16 February. The Hua Hin unit deployed one Super King Air aircraft and three Caravan planes, while in Rayong one CN aircraft and another Caravan were in use, and in Khon Kaen one Casa aircraft was operating.
A new unit in Phitsanulok was also opened, equipped with two Casa aircraft.
Techniques based on royal rainmaking handbook
The agency stressed that its weather-modification procedures were based on the royal rainmaking handbook handed down by King Bhumibol Adulyadej. Methods included the targeted formation of clouds to absorb and distribute fine dust particles, further cloud development to strengthen this uptake, and the use of dry ice to break down temperature inversion layers in the atmosphere.
Bangkok missions and success rate
Operational data showed that between 1 December 2025 and 9 February 2026 a total of 398 flights were conducted over Bangkok and nearby provinces on 66 days. After the missions, PM2.5 and Air Quality Index (AQI) readings decreased on 53 days, corresponding to a reported success rate of 80 percent.
Results in Northeast and North
In the Northeast, the department said it flew 15 missions over eight days between 15 January and 9 February. On all eight of those days, PM2.5 and AQI levels fell after operations, with a success rate of 100 percent.
In the North, 13 missions were carried out over six days between 1 and 9 February, and dust and AQI values also declined on all six days, again yielding a reported 100 percent success rate.
Local campaigns against forest fires
In parallel, authorities in Mae Hong Son province launched a joint campaign at the beginning of the month to prevent forest fires and reduce air pollution. Several key leaders took part in an opening event in front of the provincial city hall to underline the importance of the measures in public.