Thailand weather guide · by region
When to Go, Region by Region
Thailand is warm all year, but the rain moves around the country with the seasons. Ten minutes here tells you which coast, city or hill town is at its best in the month you're travelling.
Hot season · south-west monsoon · cool season — and two coasts that take turns being perfect.
The big picture
Three seasons, one tropical climate
This guide is exactly that — a guide. Even in monsoon months there is a full calendar of festivals, tours and adventures across the country, and many travellers deliberately choose the green season for quieter beaches and better rates.
Hot season
March to mid-May. The hottest, driest stretch — great beach weather on both coasts, with April the peak of the heat and the odd pre-monsoon storm.
South-west monsoon
Mid-May to October. Rain arrives in showers and thunderstorms rather than all-day drizzle. Heaviest on the Andaman (west) coast; the Gulf coast stays comparatively dry.
Cool season
November to February. The north-east monsoon brings clear skies and lower humidity. Cool in the north and inland; still warm on the coasts and in the south.
Quick reference
The best time to visit, by region
Save this table. It's the single most useful thing on the page when you're choosing dates.
| Region | Best months | Also good | Watch out for |
|---|---|---|---|
| Andaman coast Phuket, Khao Lak, Krabi, Phi Phi, Lanta, Lipe, Similans | Late December – March | November and April (warm, mostly dry) | May – October monsoon; some island trips cancelled on rough-sea days |
| Gulf coast Koh Samui, Koh Phangan, Koh Tao | Late January – April | July – August (sheltered from the SW monsoon) | October – December heavy rain; March – April hot |
| Bangkok & central plains | December – mid-February | November, late February | March – May intense heat; September – October wettest |
| Northern Thailand Chiang Mai, Chiang Rai | December – January | November, February | March – April heat and haze; May – October monsoon |
| Eastern Gulf Pattaya, Koh Samet, Koh Chang | December – February | March – April (dry, hot) | June – August very wet the further east you go |
Andaman coast
Phuket & the west coast
From December to March, rainfall in Phuket drops below 100 mm a month, skies are clear and the sea is calm — this is the island's classic high season. Because winter winds blow offshore, temperatures on the west coast run slightly higher than on the east side of the peninsula.
Sunshine is generous from January to March and much more limited from May to October, when the south-west monsoon strikes the coast straight from the sea. April brings pre-monsoon thunderstorms, more often here than anywhere else in the country. The sweet spot is late December to March.
Monsoon and boat trips
During the summer monsoon the Andaman Sea can be choppy. When the government issues severe weather or sea-condition warnings, island tours are cancelled for safety — we rebook or refund rather than sail into it. Ask us about sheltered alternatives on those days.
Gulf of Thailand
Koh Samui & the Gulf islands
The Gulf coast runs on a different calendar. Summer rains are frequent but not particularly heavy, which is why Samui, Phangan and Tao are popular from July to August while Phuket is in full monsoon. The real wet season is October and November, when the retreating monsoon draws energy from a still-warm sea and rain can be torrential; showers sometimes linger into early or mid-January.
The best window, which also covers Pattani and Songkhla further south, is mid or late January to April — with February the pick, since March and April get hot. The sea around Samui is pleasant all year.
Northern Thailand
Chiang Mai & the north
The northern plains and valleys are hot for most of the year, with one exception: winter. In December and January the days are sunny but nights turn cool, dropping to around 16–17 °C in the centre and 14–15 °C further north. When cold air pushes down from China, Chiang Mai nights can fall to about 5 °C.
By February daytime highs are back at 33–34 °C, rising to 35–37 °C between March and May with peaks above 40 °C. The monsoon runs from mid-May to mid-October, with annual rainfall of 1,000–1,500 mm peaking in August and September. Skies are clearest from December to April. December and January are the months to come; by February the heat starts to build, especially in the south-central plain.
Central Thailand
Bangkok & its surroundings
Bangkok is hot all year. The most pleasant stretch is mid-November to January: clear skies, highs around 32 °C and lows near 22 °C. Temperatures climb from February, and between March and mid-May the heat becomes intense — highs of 37–38 °C and nights that stay near 28–29 °C. The city isn't as hot as the inland north-central plains, but proximity to the sea makes it more humid, and the urban heat-island effect traps the warmth. Air-conditioning is not optional.
The monsoon arrives in mid-May and temperatures ease, with frequent cloud, higher humidity and intense showers and thunderstorms that bring welcome relief. Annual rainfall is about 1,450 mm, peaking in September (345 mm) and October (240 mm). Sunshine is excellent from December to April. December to mid-February is the best time to visit.
Eastern Gulf
Pattaya & the eastern coast
Pattaya, south-east of Bangkok, shares the capital's climate but sits on a stretch of coast — running down to Sattahip — that is relatively sheltered from the downpours: roughly 100 mm a month from June to August. It's still a hot, humid, cloudy summer, and the wettest months are May, September and October at either end of the rainy season. December to February is best, with March and April dry and sunny but warmer. The coast south-west of Bangkok, towards Ao Noi, is similarly protected, with summer rainfall of only 1,000–1,200 mm.
The wet coast further east
South of Pattaya the summer rains build quickly. Rayong receives about 1,700 mm a year and Koh Samet 1,340 mm, while Chanthaburi reaches 2,800 mm and Trat — the province for Koh Chang — up to 3,500 mm, so summer is generally not recommended out east. Winter here is dry and beautiful; December to February is the time, with March and April warmer but still sunny apart from short pre-monsoon showers.
Deeper detail
Two coasts, the mountains and the storm season
Peninsular Thailand: why the two coasts differ
The peninsula is hot all year, and the March–May rise is gentler than on the mainland — highs of 33–34 °C rather than 31–32 °C. What changes is when the rain falls. On the east coast facing the Gulf, from Chumphon to the Malaysian border, the summer monsoon is light enough that summer is high season; the heavy rain comes with the retreating monsoon from October to December. On the west coast facing the Andaman Sea — the Similans, Phuket, Krabi, Phi Phi, Lanta and Lipe — the summer monsoon hits head-on and summer is very wet, while December to March is dry. The cloudiest months on the east coast are still June to October, though there isn't a great deal more sun from November to January.
Mountains
Ranges above 2,000 m run along the Myanmar border in the west and the Lao border in the north. Above about 1,000 m the climate is cool in winter — mild days, cold nights — and pleasantly warm the rest of the year. Storms are more torrential in the hills and can build in the afternoons even before the monsoon, which is why the region is wrapped in rainforest. Major rivers including the Mekong and the Salween thread the basins between the ranges before reaching the plains.
Cyclones and typhoons
Pacific typhoons travel east to west and usually spend most of their energy over Vietnam, Laos and Cambodia before reaching mainland Thailand, though they can still deliver torrential rain; on a more southerly track they affect the peninsula more directly. They strike from June to December and most often from September to November. Indian Ocean cyclones are less common, form mainly from April to December in two phases (April–June and October–December), and can affect the Andaman Sea early in their development or reach the mainland via Myanmar.
Thailand has historically been spared the worst compared with the Philippines or Vietnam. The peninsula sits in a relatively safe zone and in recent decades has been hit directly only between mid-October and around 20 December — though Tropical Storm Pabuk arrived in early January 2019, and Typhoon Gay (November 1989) and Forrest (November 1992) both struck the Gulf. Without the cyclone risk, November would be a pleasant month across much of the country.
Packing
What to bring
Thailand rewards packing light. Almost anything you forget can be bought on arrival — and usually cheaply.
North & mountains in winter
Light clothes for the day, a jacket and a hoodie or jumper for the evenings in Chiang Mai and Chiang Rai. Add spring/autumn layers and a warm pullover for the hills.
Bangkok
Light clothing with a light jacket for the evening, a scarf for the cool wind in winter, and a sweater for aggressively air-conditioned malls and taxis.
Beaches & islands
A light jumper for evenings and a scarf for the breeze; in the Gulf, a light raincoat or umbrella. Rubber-soled shoes protect feet in the water — but never stand on coral; it's protected and alive.
Summer anywhere
Lightweight tropical clothing, a raincoat or umbrella, comfortable shoes, and a light sweatshirt for air-con. Hiking shoes and a sweater for evenings if you're heading into the mountains.
Snorkelling
Mask and snorkel are provided on nearly every island tour. Fins usually aren't — bring your own or ask us to arrange a rental for your particular trip.
Temples & cultural sites
Shoulders and knees covered, shoes off at the door, and dress neatly and respectfully. A light scarf or sarong in your day bag solves most situations.
Planning
Weather questions we're asked most
Is it worth visiting Phuket in the rainy season?
Often, yes. Rain usually arrives as an afternoon storm rather than a washed-out day, hotels are cheaper and the island is quieter. What changes is the sea: some island boat trips are cancelled on rough days, so we build itineraries around sheltered bays, culture, food and spa in those months and keep the big island days flexible.
Which coast should I choose for a July or August trip?
The Gulf side — Koh Samui, Phangan and Tao — which is sheltered from the south-west monsoon. Phuket and Krabi are at their wettest then. We can combine both coasts in one itinerary if you want the Andaman islands too.
When is the sea calmest for island hopping from Phuket?
Late December to March, with November and April as good shoulder months. Similan Islands trips only run in this season; the national park closes for the monsoon.
Does Songkran affect travel?
Thai New Year, 13–15 April, is a nationwide water festival — fun, wet and busy. Transport and hotels book out early and some businesses close, so plan and book ahead if your dates fall over it.
Not sure which month or coast?
Tell us when you can travel and what you want from the trip, and we'll point you to the coast that'll be at its best.
Ask our team