Siberian Chill Brings Fog to Bangkok, Frost Alerts in North

A fresh wave of winter air is sliding down from China this week, primed to shave a couple of degrees off the thermometer across much of Thailand and deliver the chilliest mornings of 2026 so far. Commuters in Bangkok may barely notice a 22 °C dawn, yet farmers on northern mountaintops are rushing to guard their crops from a potential frost surprise.

Quick Weather Snapshot

• Tuesday–Saturday: new high-pressure wedge pushes south.

• Upper North: another 1–3 °C drop, breezy, foggy dawns.

• Central Plains & Bangkok: cooler mornings, patchy fog, lows 22–24 °C.

• Mountain peaks: sub-10 °C readings, chance of nam khang khaeng (ice crystals).

Cold Air Surges South Again

Every January, an arm of Siberian high pressure typically noses into Indochina. This week’s inflow is rated “moderately strong” by the Thai Meteorological Department (TMD), enough to nudge daytime warmth downward without producing a full-blown cold snap. The system should blanket the South China Sea by mid-week, tightening northeast winds and keeping skies largely clear—a recipe for heat to radiate away at night.

What to Expect Region by Region

Upper North

Residents in Chiang Mai, Chiang Rai, Nan and the ridges of Doi Inthanon should prepare for a 2–4 °C slide between Wednesday and Friday. TMD warns that gusts may make real-feel temperatures even lower. Peaks could flirt with single-digit lows, reviving the annual hunt for frost selfies.

Northeast

Khon Kaen and Udon Thani will feel a milder pinch—about 1–3 °C cooler—but the bigger issue is morning fog along highways 2 and 12. Drivers are urged to slow down before sunrise.

Central Plains and Bangkok

Bangkokians will wake to sweater-worthy mornings of 22–24 °C. Though the change sounds minor, high humidity means body heat escapes faster. Fog may briefly lower visibility on elevated expressways between 05:00 and 08:00.

South

The cold surge weakens south of Chumphon, yet northeast monsoon winds could still stir 2–3 m waves in the Gulf by Thursday. Small craft should remain in port.

Historical Chill: How Does 2026 Compare?

Ten-year data from TMD show Chiang Mai’s mean January low has swung between 15–19 °C. Last year’s 15.9 °C ranked among the coldest of the decade; forecasters say this week could challenge that mark on isolated ridges. Lampang’s bowl-shaped valley often amplifies nocturnal cooling—its record 14.4 °C January average remains the benchmark. In Tak’s Umphang district, extreme minima have dived to 6–7 °C almost every other year, underscoring how sharp the chill can be in the Dawna Range.

Farm Fields on Alert

Northern growers are bracing for two threats: direct frost scorch on tender vegetables and, paradoxically, pest outbreaks favored by drier air. The Agriculture Department recommends:

• Covering seedbeds with clear plastic tunnels after 17:00.

• Moving newborn livestock into wind-sheltered sheds and providing lukewarm water.

• Monitoring longan and lychee orchards for black mold once humidity rebounds.Lessons from an infamous 2007 cold spell—when Suphan Buri 3 rice yields collapsed 54 %—suggest that preventive measures now can save entire harvests later.

Health Watch: Ministry Advice

The Public Health Ministry is urging Thais to practice four habits during the cool stretch:

Layer clean clothing, drink warm fluids, and moisturise skin to avoid cracking.

Wear masks in crowds; influenza and COVID-19 spread faster in cold air.

Skip the late-night campfire in closed tents—carbon-monoxide poisoning claims lives every winter.

Keep an eye on elderly relatives, small children, and people with chronic illnesses; they lose body heat fastest.

Travel & Daily Life Tips

Motorists on mountain roads between 05:00–09:00 should expect visibility under 200 m. Domestic airlines occasionally delay northern flights when runway RVR falls. Urban workers can beat the chill with a light windbreaker rather than a heavy coat; daytime highs will still touch 30 °C in many valleys.

Outlook Beyond the Weekend

Meteorologists hint at another, slightly stronger high-pressure pulse around the final days of January. If models hold, Thailand could log its coldest morning of the year during that window before the mercury climbs steadily into the hot season. For now, keep those blankets handy and check the hourly updates on TMD’s mobile app before planning dawn treks or farm chores.