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Wet Weather Set to Continue Across Thailand, Including Krabi and Koh Lanta
Thailand is in for another soggy day on September 4, 2026, according to the Thai Meteorological Department. A monsoon trough is sitting across the North and upper Northeast, feeding into a low-pressure cell over the Gulf of Tonkin, while a moderate southwest monsoon is active over the Andaman Sea, the mainland, and the Gulf of Thailand. The result is scattered to fairly widespread rain in most regions, with isolated heavy and even very heavy falls in some provinces. For Koh Lanta specifically, the west coast of the South (Krabi's zone) can expect scattered thundershowers and isolated heavy rain, along with building seas, so it's worth keeping an eye on conditions if you've got a ferry or boat trip planned.
What's Driving the Rain
The main players are the monsoon trough over the North and upper Northeast, and the moderate southwest monsoon pushing across the Andaman Sea, mainland, and Gulf of Thailand. There's also Tropical Depression Saudel in the mix, previously sitting over Guangdong province in China, but it has since weakened into an active low-pressure cell. Isolated heavy rain is expected countrywide, with the heaviest concentrated in the upper North and western Northeast.
Region by Region
<table> <tr><th>Region</th><th>Conditions</th><th>Temps</th><th>Winds / Seas</th></tr> <tr><td>North</td><td>Scattered thundershowers, isolated heavy rain (Mae Hong Son, Chiang Mai, Lamphun, Lampang, Phrae, Uttaradit, Tak, Phitsanulok, Phetchabun); isolated very heavy rain (Chiang Rai, Phayao, Nan)</td><td>22-35°C</td><td>SW winds 10-20 km/h</td></tr> <tr><td>Northeast</td><td>Fairly widespread rain, isolated heavy falls (Loei, Nong Bua Lamphu, Udon Thani, Nong Khai, Sakon Nakhon, Kalasin, Khon Kaen, Maha Sarakham, Roi Et, Si Sa Ket); isolated very heavy rain (Bueng Kan, Nakhon Phanom, Mukdahan, Yasothon, Amnat Charoen, Ubon Ratchathani)</td><td>23-34°C</td><td>SW winds 10-20 km/h</td></tr> <tr><td>Central</td><td>Scattered thundershowers, isolated heavy rain (Lop Buri, Saraburi)</td><td>25-36°C</td><td>SW winds 10-20 km/h</td></tr> <tr><td>East</td><td>Scattered thundershowers, isolated heavy rain (Nakhon Nayok, Chanthaburi, Trat)</td><td>23-35°C</td><td>SW winds 15-35 km/h, waves 1-2m, above 2m in storms</td></tr> <tr><td>South (East Coast)</td><td>Scattered thundershowers (Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla, Pattani, Yala, Narathiwat)</td><td>23-35°C</td><td>SW winds 15-35 km/h, waves ~1m near coast, 1-2m offshore, above 2m in storms</td></tr> <tr><td>South (West Coast)</td><td>Scattered thundershowers, isolated heavy rain (Phang Nga, Phuket, Krabi, Trang, Satun)</td><td>23-33°C</td><td>North of Phuket: SW winds 20-35 km/h, waves ~2m, above 2m in storms. South of Krabi: SW winds 15-35 km/h, waves 1-2m, above 2m in storms</td></tr> <tr><td>Bangkok</td><td>Scattered thundershowers</td><td>26-35°C</td><td>SW winds 10-25 km/h</td></tr> </table>
Andaman Sea Conditions
Waves on the Andaman Sea are running around 2 metres, rising above 2 metres during thundershowers, and ships are advised to exercise caution.
What This Means If You're Heading to Koh Lanta
This isn't a single-region event, it's a nationwide wet-weather day stretching from Bangkok through the North, Northeast, and both southern coasts. Krabi (which covers Koh Lanta) and Trang are named directly for scattered thundershowers and isolated heavy rain, with southwest winds of 15-35 km/h and seas building to 1-2 metres, above 2 metres during storms. That's worth factoring in if you're booked on a boat transfer or ferry to or from the island. TMD is flagging general caution for vessels during thunderstorm activity rather than issuing a storm warning, so this reads as fairly typical monsoon-season weather rather than anything extreme.
Information sourced from The Thaiger.