We’ve been building private trips to Thailand since 2009. In that time, we’ve had clients soak through their linen shirts at Songkran, watch a waterfall we recommended run bone-dry, and land in Koh Samui in glorious sunshine the same week Phuket was shuttered by storms. Thailand’s weather isn’t complicated — but the answers most travel guides give are dangerously oversimplified.

So here’s what we actually tell our clients when they ask. No “Thailand is tropical so expect rain” platitudes. Specific, regional, month-by-month honest.

Three Seasons — But That’s Not the Whole Story

Officially, Thailand has three seasons: a cool dry season (November–February), a hot season (March–May), and a rainy season (June–October). That framework works reasonably well for inland areas — Bangkok, Chiang Mai, the North, and Isan. But apply it to the coast and you’ll get it badly wrong, because Thailand has two separate coastlines that face different seas and experience opposite weather patterns.

The Coastline Problem Nobody Tells You About

This is the single most important piece of information for anyone planning a beach component to their trip. The Andaman coast (Phuket, Phang Nga, Krabi, Koh Lanta, Koh Phi Phi) faces the Indian Ocean. It gets the southwest monsoon directly, meaning it is at its absolute best from November through April — and genuinely rough from May through October, with heavy surf, potential boat cancellations, and some resorts closing entirely.

The Gulf coast (Koh Samui, Koh Phangan, Koh Tao, Surat Thani province) is on the other side of the peninsula, sheltered from the southwest monsoon. Its rainy season runs November–December, brought by the northeast monsoon. This means that while the Andaman is shutting down in May, Koh Samui is opening up — and when Phuket is at its peak in December, Samui can be grey and wet.

The practical implication: if you want to combine the North with a beach stop, November through February gives you the best of both worlds on the Andaman side. If you’re travelling in June or July, the Gulf islands are your beach option — and the North is actually quite beautiful with full waterfalls and no tourist crowds.

Month by Month: Inland Thailand, North, and Isan

For Bangkok, Chiang Mai, the Northern hills, and the Northeast (Isan), here is what each month actually looks like on the ground. We’ve been travelling these regions for 17 years and these descriptions reflect reality, not marketing brochures.

January — Peak Season

The best month overall. Cool (15–20°C in Chiang Mai), dry, clear skies. High season crowds and prices. Book early for anything in the North.

February — Excellent

Still cool and beautiful. Chiang Mai Flower Festival (first weekend) is worth timing your trip around — the moat is ringed with blooms. Warmer than January but not uncomfortably so.

March — Heating Up

Heat builds noticeably. In the North, burning season begins — farmers clear fields, visibility drops, and haze can obscure mountain views. Bangkok is hot but manageable. Fewer crowds.

April — Hottest Month

38–40°C in Bangkok, haze thick in Chiang Mai. Songkran water festival (13–15 April) is spectacular if you embrace getting drenched — and therapeutic if you don’t mind the heat. Avoid if you’re heat-sensitive.

May — Hot + Storms

Still very hot, thunderstorms begin in the North. The haze usually clears with the first rains. End of Andaman beach season. We generally advise clients to avoid this month unless the festival timing is the draw.

June — Rainy Season Begins

North and Isan turn dramatically green. Rain is typically afternoon thunderstorms, not all-day drizzle. Phi Ta Khon ghost festival in Loei (dates vary, usually June). Far fewer tourists — a genuine advantage.

July – August — Lush Green Season

Waterfalls at their fullest — Erawan, Nam Tok Mae Klong, Thi Lo Su are genuinely dramatic. Ubon Ratchathani Candle Festival (late July, Asalha Bucha) is one of Thailand’s most underrated events. Accommodation prices at their lowest.

September — Wettest Month

Peak of the rainy season. Some river crossings and back-road routes become difficult. Not a month we recommend for first-time visitors, though the rice harvest landscapes around Chiang Rai are extraordinary.

October — Transition

Rains ease in the North. Landscapes still beautifully green. OK Phansa (end of Buddhist Lent) sees boat racing festivals on rivers across Isan — an authentic, crowd-free experience.

November — Shoulder Season

One of our favourite months. The North is still lush but dry and cooling. Loy Krathong (full moon, usually mid-November) sees floating lanterns and krathong boats on rivers across the country — Chiang Mai’s Yi Peng sky lantern release is internationally famous.

December — Peak Season

Cool, dry, perfect — and fully priced. Andaman beaches at their best. Christmas and New Year bring the highest demand and prices of the year. Book three to four months ahead if you want anything near Chiang Mai or the Andaman coast.

Our Honest Recommendation by Traveller Type

First-time visitors: November through February

If you’ve never been to Thailand and want the most comfortable, reliable weather experience, this four-month window is your answer. Cool mornings in the North, clear skies for temple visits, calm Andaman seas for snorkelling — everything works in your favour. The tradeoff is that you’ll be sharing some sites with other travellers, and you’ll pay more for accommodation. It’s worth it.

Repeat visitors or budget-conscious travellers: June through September in the North

If you’ve already done the classic circuit and want to see a different Thailand — or if your schedule doesn’t allow a November to February visit — the North and Isan in the green season is genuinely rewarding. You need to accept that some afternoons will involve rain, and a handful of back roads may be impassable. In exchange, you get waterfalls in full force, rice terraces at their most cinematic, and almost no other foreign tourists.

Avoid: April and May everywhere

This is unusually blunt advice for a travel company to give, but we mean it. April is the hottest month of the year, the North is still hazy, and the Andaman monsoon has started. The only reason to be in Thailand in April is Songkran — which is genuinely worth experiencing once. Outside of that specific festival, April and May are the months we find it hardest to build itineraries around.

Festivals Worth Timing Your Trip Around

Feb — Chiang Mai Flower Festival: First weekend of February. The moat road and Nimmanhaemin gardens fill with elaborate floral floats.

Apr 13–15 — Songkran: Thai New Year water festival. Bangkok and Chiang Mai are the biggest celebrations.

Jun–Jul — Phi Ta Khon (Ghost Festival), Loei: One of Thailand’s most visually extraordinary festivals — masked processions, ancient ritual, very few foreign visitors.

Jul–Aug — Ubon Candle Festival: Asalha Bucha full moon, late July. Ubon Ratchathani carves enormous wax sculptures and parades them through the city.

Nov — Loy Krathong & Yi Peng, Chiang Mai: Full moon in November. Thousands of sky lanterns released simultaneously over the Ping River.

For detailed region-specific planning, get in touch and we’ll work with your timeline.