BANGKOK, THAILAND – Thailand’s weather agency warned that late-January warmth would coincide with worsening fine dust pollution and continued risks at sea.
Temperatures rose across Upper Thailand
The Meteorological Department forecast significantly milder weather for Upper Thailand and the upper South from 26 to 31 January 2026, with air temperatures expected to increase by 1 to 4 degrees Celsius. Despite the warming trend, early mornings in the upper North and upper Northeast remained cool to cold because a weakening high-pressure system over Upper Thailand and the South China Sea was still in effect. Isolated thunderstorms were reported in the South.
Morning haze and PM2.5 build-up expected
With rising temperatures, the weather service expected widespread light morning fog, especially in northern regions and the plains around Bangkok. The agency explicitly warned that PM2.5 fine dust could accumulate more strongly in Upper Thailand between 26 and 31 January due to weak winds and limited vertical air circulation, which hindered the mixing of air masses. Health agencies viewed such conditions as an increased burden on the respiratory system, particularly for high‑risk groups.
“People in Upper Thailand and the upper South should take care of their health because of the changeable weather conditions.”
said the meteorologists, in their statement.
Monsoon persisted as waves slowly eased
Over the Gulf of Thailand, the South and the Andaman Sea, a moderate northeast monsoon remained in place, although experts assessed that winds and waves should gradually subside. In the lower Gulf, wave heights were generally estimated at 1 to 2 metres, but could exceed 2 metres in thunderstorm areas. Similar sea conditions were reported for the Andaman Sea.
Maritime operators urged to use caution
The weather service advised maritime traffic in the Gulf of Thailand and the Andaman Sea to exercise particular caution and for captains to avoid thunderstorm zones. The key guidance from the agency included careful navigation in all exposed sea areas and avoiding travel through storm cells where waves could rise well above 2 metres. Mariners were also told to follow local weather and marine warnings issued by port authorities.
Cool mornings, warmer days in the North and Northeast
Refined regional forecasts indicated that the North, Northeast, Central Region and East would remain mostly cool with light morning fog, alongside a temperature rise of 1 to 2 degrees. In the North, daytime highs were put at 29 to 33 degrees Celsius, with nighttime lows between 13 and 18 degrees. On mountain tops, cold to very cold conditions prevailed, with possible frost formation and minimum temperatures ranging from 2 to 12 degrees.
In the Northeast, nighttime temperatures were forecast at 13 to 19 degrees and daytime highs at 29 to 33 degrees, with higher elevations between 8 and 14 degrees. Winds there were predominantly from the north to northeast at 10 to 15 km/h. The Central Region and the East reported similar temperature ranges, with daytime highs around 31 to 35 degrees and easterly winds, while waves off the eastern coast were around 1 metre near shore, increasing to 1 to 2 metres further out.
Thunderstorms in the South and slight warming in Bangkok
Along the eastern coast of the South, mornings remained cool, with temperatures in the upper South also rising by 1 to 2 degrees. Around 10 percent of the area, especially near Chumphon, Surat Thani, Nakhon Si Thammarat and Songkhla, was affected by thunderstorms. From Surat Thani northwards, northeast winds of 15 to 35 km/h were reported with waves of 1 to 2 metres, while from Nakhon Si Thammarat southwards, waves were around 2 metres, with higher waves in thunderstorm fields.
On the western coast of the South, mornings also stayed cool, with a 10 percent chance of thunderstorms, particularly in Krabi, Trang and Satun. Wave heights were mostly about 1 metre near the shore, increasing to 1 to 2 metres further offshore, and above 2 metres in storms.
Bangkok faced cool dawns and light fog
For Bangkok and surrounding areas, the forecast called for cool mornings with light fog and a temperature rise of 1 to 2 degrees. Minimum temperatures were expected at 21 to 23 degrees, with highs between 32 and 35 degrees and easterly winds of 10 to 15 km/h.