Southern Thailand Braces for Torrential Rains Dec 4–6 as Northern Haze Looms

Racing clouds over the Gulf and a stubborn lid of still air in the North are setting up a week in which southern provinces brace for torrential rain while northern towns continue to inhale dusty haze. From stronger monsoon-fed downpours to a subtle cool snap in the Northeast, Thais are facing a weather cocktail that demands both umbrellas and N95 masks.

At a Glance

• Heavy rain likely across 10 southern provinces, especially along both coasts.

• 1–2 °C temperature dip and gusty winds sweeping into the Northeast.

• PM2.5 concentrations creeping upward in Chiang Mai, Lampang, and Nan as winds stall.

• Marine warning: waves rising 1–2 m, topping 2 m near storms, could disrupt ferry links and fishing fleets.

• Government agencies activate nine-point flood response plan; emergency cash relief set at ฿9,000 per affected household.

What Is Driving the Sudden Shift?

A moderate cold surge from southern China has slipped over the Mekong, colliding with the lingering easterly moisture stream that funnels straight into the Gulf of Thailand. The clash energises clouds, wringing out rain over Surat Thani and further south. At the same time, the weakened pressure gradient leaves the North under near-calm conditions, allowing smoke from field burning and forest fires to stagnate.

Climatologists at Kasetsart University add that this December spike is consistent with a prolonged La Niña phase, which typically pushes moisture toward the peninsula while lowering upper-atmosphere wind speeds in the North.

Provinces on Flood Watch

The forecast pinpoints Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla, Pattani, Yala, Narathiwat, Ranong, and Phang-nga for rainfall totals that could exceed 100 mm within 24 hours. Low-lying areas around the Tapi, Pak Phanang, and Sawi river basins remain vulnerable to flash floods and runoff surges. Coastal districts such as Lang Suan and Pak Phanang should also prepare for storm-driven tides that hamper drainage.

How Authorities Are Getting Ready

• The Royal Irrigation Department has cleared critical canals and positioned mobile pumps to speed up water release.• ThaiWater app notifications now ping communities three times daily, offering hyper-local rainfall estimates.• Provincial disaster offices have pre-staged sandbags and portable footbridges, prioritising schools scheduled to reopen next week.• A dedicated “Big Cleaning Day” will follow each flood crest so debris does not block secondary drains.

The National Water Command Centre reports that 108 heavy-duty pumps, 326 excavators, and 1,240 relief workers stand ready along the coast from Prachuap Khiri Khan to Satun.

Dust and Haze Loom Over the North

While the South readies for water, residents of Chiang Mai, Chiang Rai, and Mae Hong Son confront an uptick in PM2.5 that has already breached 80 µg/m³ in several districts—well above Thailand’s 37 µg/m³ guideline. With winds under 5 km/h, pollution is expected to linger until the next frontal system sweeps through.

Air-quality scientists warn that persistent haze may aggravate respiratory conditions. They urge mask use, indoor air purifiers, and avoiding early-morning exercise when inversion layers trap fine dust closest to the ground.

Looking Back: A Decade of Early-December Floods

Historical data show that 7 of the past 10 years have delivered significant floods to the South during the first week of December. The 2024 season alone caused roughly ฿140 B in losses, and analysts fear this year could nudge that figure higher if rain stalls over rubber- and palm-rich districts. Economic modelling from Kasikorn Research Center puts a potential ฿25 B dent in national GDP should infrastructure damage mirror 2024 levels.

Advice for Travellers and Mariners

• Inter-city buses heading south from Bangkok should anticipate road closures on Phetkasem Highway; real-time updates available through Highways Department social media.• Airlines serving Hat Yai, Nakhon Si Thammarat, and Trang may resort to holding patterns; passengers are advised to check flight alerts.• In the lower Gulf, small craft should remain in port when waves exceed 2 m. Fishermen venturing out are urged to wear life vests and monitor VHF channel 67 for coast-guard advisories.

The Week Ahead

Meteorologists expect the heaviest rainbands to ease once the Chinese high-pressure wedge retreats eastward and monsoon winds slacken. By mid-week, showers should taper, allowing floodwaters to recede—though residual ponds in urban areas may persist. Meanwhile, a fresh westerly wave could stir stronger breezes in the North, finally dispersing stagnant haze.

For now, the watchwords are vigilance and flexibility: keep emergency kits stocked, stay tuned to official channels, and adjust travel plans as the sky decides whether to clear or pour.