Thailand’s Chill Lingers: Foggy Roads, Rising Dust, and Rough Seas

A late-season chill is refusing to loosen its grip on much of Thailand, keeping dawn temperatures low, cloaking valleys in fog and nudging air-quality readings upward, even as the northeast monsoon loses strength and rain clouds scatter over the South.

At a glance

• Cool mornings persist across the North, Northeast and Central Plain despite a weakening high-pressure ridge.

• Fog banks are disrupting early-hour travel on key intercity highways and around Bangkok.

• Dust concentration creeps toward the unhealthy range in several northern provinces.

• Southern rainfall tapers off, but the Gulf remains rough enough to warrant caution for small boats.

Cold air clings to the highlands

The cool air mass that swept down from China in late December still blankets the upper North and Northeast, holding back daytime warmth. Provincial weather stations logged minimum temperatures between 14-18°C, while night-time mercury on mountain tops dipped to 5-15°C – enough for thin frost on Doi Inthanon and Phuhinrongkla. Forecasters expect the chill to ease only slightly over the weekend as the weakened monsoon relinquishes control.

Morning fog complicates holiday travel

Pre-dawn drivers woke to stretches of dense fog that pushed visibility below 100 m along Highways 1, 11 and 21. Bangkok commuters also reported hazy conditions on outer-ring expressways. With New Year traffic still heavy, the Highway Police urge motorists to slow down on highways, keep a safe distance and use low-beam headlights. Travellers can check live conditions via the 1193 official hotline or the Traffy Fondue app.

Dust levels on the rise

Weak winds mean the notorious PM2.5 season has arrived early. A broad haze belt from Lampang to Phitsanulok saw readings climb above 50 µg/m³, driven by air stagnation and sporadic open burning. Public schools weighing school sport days have been advised to move activities indoors when the index spikes. Health authorities remind parents, the elderly and outdoor workers to wear certified N95 masks and limit strenuous exercise during peak hours.

South sees a lull in rain but seas still choppy

With the northeast monsoon retreating, the lower Gulf is enjoying lighter showers – only isolated thunderstorms remain around Nakhon Si Thammarat and Songkhla. Offshore, however, mariners still face 1–2 m waves, higher near storm cells. Small craft in the Andaman Sea and ferry operators on the Phuket-Krabi ferry route have been told by harbour masters to monitor updates and avoid deep-sea runs when lightning is detected.

Health officials issue winter wellness checklist

The Public Health Ministry warns that surging cases of influenza and pneumonia often follow cold snaps. Their advice: layer warm clothing, sip hot drinks, keep up with annual vaccination, and use electric or charcoal space heaters safely to prevent carbon monoxide buildup. Families are urged to pay close attention to vulnerable groups – young children, seniors and those with chronic illnesses – who face higher risks from both cold air and poor visibility.

Looking ahead: another Chinese cold surge on the horizon

Meteorologists are tracking a new cold surge expected between January 3-7. If the mass pushes through, most regions could see the mercury drop 1-3°C, reviving frost pockets on high peaks and drawing campers to popular parks. Authorities in Chiang Mai and Kalasin fields are expanding camping reservations but caution visitors to prepare for near-freezing nights and to monitor forecast bulletins issued each evening at 18:00.