Southeast Asia by Season: Routing Around the Monsoon
The region has three different rainy seasons that do not align, so the cheapest months in one country are the wettest in the next.
Budget Routes Editorial
August 15, 2026 · 3 min read
Key takeaways
- Southeast Asia is treated as one climate in most planning, and it is at least four.
- Getting the sequence right means arriving in each country during its good months rather than following a fixed route into whatever the weather happens to be.
- Vietnam is 1,650 km long and its north, centre and south do not share a season.
- From roughly February to April, agricultural burning across northern Thailand, Laos and northern Vietnam pushes air quality to genuinely unhealthy levels.
- Thailand — Andaman coast: Nov–Apr — May–Oct (monsoon).
Southeast Asia is treated as one climate in most planning, and it is at least four. Getting the sequence right means arriving in each country during its good months rather than following a fixed route into whatever the weather happens to be.
The four cycles
| Area | Best | Avoid |
|---|---|---|
| Thailand — Andaman coast | Nov–Apr | May–Oct (monsoon) |
| Thailand — Gulf coast | Jan–Aug | Nov (wettest) |
| Northern Thailand / Laos | Nov–Feb | Feb–Apr (burning), May–Oct (rain) |
| Vietnam — north | Oct–Dec, Mar–Apr | Jun–Aug (hot, wet) |
| Vietnam — centre | Feb–Aug | Sep–Nov (typhoons) |
| Vietnam — south | Dec–Apr | May–Oct (wet) |
| Cambodia | Nov–Feb | Mar–May (heat) |
| Indonesia | Apr–Oct | Nov–Mar (wet) |
The two Thai coasts
This is the most useful single fact in regional planning and the most frequently missed.
The Andaman coast — Phuket, Krabi, Koh Lanta, Phi Phi — faces southwest and gets the monsoon from May to October.
The Gulf coast — Koh Samui, Koh Phangan, Koh Tao — is sheltered from that and instead has its wettest period in November, exactly when the Andaman side is drying out and entering its best months.
The practical rule: going in November, go to the Andaman side. Going in June or July, go to the Gulf. There is a good Thai island almost any month of the year, provided you pick the right coast.
Vietnam's three climates
Vietnam is 1,650 km long and its north, centre and south do not share a season.
December to February: the north is cold and drizzly, the south is warm and dry. Start in Hanoi and finish in the warmth.
May to August: the south is in its wet season, the north is pleasant. Run the other way.
September to November: the central coast — Hue, Da Nang, Hoi An — gets typhoons and serious flooding. Hoi An's old town floods most years. This is the window to be careful with.
Burning season, which rainfall charts miss
From roughly February to April, agricultural burning across northern Thailand, Laos and northern Vietnam pushes air quality to genuinely unhealthy levels. Chiang Mai regularly records among the worst AQI readings in the world during March.
It is dry, so season guides based on rainfall call it the best time to visit. For the north, it is not. Anyone with asthma or a respiratory condition should treat this as decisive.
Routing around it
November to February is the safest region-wide window: dry and cooler almost everywhere on the mainland. It is also peak, so prices are highest.
A November–January route might run: northern Thailand and Laos in November, down to Vietnam's south in December, Cambodia in January, Andaman islands in February.
A June–August route instead: Vietnam's north and centre, then Thailand's Gulf islands, then Indonesia — all of which are in good months while the Andaman coast and southern Vietnam are wet.
The green season case
Travelling in the wet months is more viable than it sounds. Rain typically arrives as an intense afternoon burst lasting an hour or two rather than persistent drizzle, mornings are frequently clear, and accommodation falls 30–50 percent with far fewer people around.
What you actually lose is boat reliability — Phi Phi, Similan and Komodo crossings get cancelled in rough seas — and occasional flooding.
So the rule for green-season travel: do not build the trip around a single ferry or a single island, and keep a spare day before any international flight home.
Frequently asked questions
When is the rainy season in Southeast Asia?
There is no single answer, which is the point. Mainland Southeast Asia has its southwest monsoon roughly May to October, but Vietnam's centre and north run on different cycles, Thailand's two coasts are on opposite schedules, and Indonesia's wet season is November to March. Routing around the rain means treating each country separately rather than the region as one.
Which Thai coast should I visit and when?
The Andaman side — Phuket, Krabi, Koh Lanta — is best November to April. The Gulf side — Koh Samui, Koh Phangan, Koh Tao — is best January to August and is wettest in November. They run on opposite cycles, so there is a good island somewhere in Thailand almost any month of the year.
What is burning season in Southeast Asia?
From roughly February to April, agricultural burning in northern Thailand, Laos and northern Vietnam pushes air quality to genuinely unhealthy levels, with Chiang Mai regularly among the worst readings globally. It is the single strongest reason to avoid the north in those months, and it is rarely mentioned in season guides that focus only on rainfall.
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