Best Time to Visit Thailand: Month by Month, Coast by Coast

The standard answer for Thailand is November to February, and for once the standard answer is mostly right. The cool season is dry in Bangkok, pleasant in the north and calm on the Andaman coast. It is also when everyone else goes, and it hides two exceptions that catch people out every single year.

The first is the Gulf of Thailand: Koh Samui, Koh Phangan and Koh Tao get their heaviest rain from October to December, just as Phuket dries out. The second is Chiang Mai, where the dry season ends in weeks of smoke from crop and forest fires. Below is the best time to visit Thailand month by month and coast by coast, with the festivals, and the rules that come with them.

Thailand weather by month, in one table

Average highs and rainfall are the Thai Meteorological Department’s 1991–2020 normals for Bangkok, Phuket and Koh Samui. Crowding is our own five-point rating. Highlighted rows are the months we would book first. Compare the Phuket and Koh Samui columns: they are the two coasts, and they move in opposite directions.

Month	Avg high · Bangkok	Rain · Bangkok	Rain · Phuket	Rain · Koh Samui	Crowds	The call
January	32.7 °C	24 mm	50 mm	127 mm		Dry, cool-ish · peak prices
February	33.7 °C	21 mm	24 mm	64 mm		Driest month on both coasts
March	34.7 °C	51 mm	81 mm	116 mm		Heating up · smoke in the north
April Songkran 13–15	35.7 °C	93 mm	135 mm	83 mm		Hottest · water festival
May	35.1 °C	217 mm	237 mm	132 mm		Rains arrive · prices fall
June	34.1 °C	199 mm	249 mm	134 mm		Green season · Samui fine
July	33.5 °C	190 mm	240 mm	117 mm		Andaman rough · Gulf good
August	33.3 °C	227 mm	309 mm	102 mm		Andaman rough · Gulf good
September	33.2 °C	336 mm	350 mm	118 mm		Wettest in Bangkok and Phuket
October	33.3 °C	289 mm	336 mm	295 mm		West clears late · Gulf turns wet
November Loy Krathong	33.1 °C	45 mm	178 mm	445 mm		Cool season begins · not Samui
December	32.3 °C	12 mm	82 mm	263 mm		Dry, busy · book early

Koh Samui’s column is the one that surprises people. Its wettest month, November, is Bangkok’s first dry one, and its driest stretch runs from February to August, straight through what the rest of the country calls the rainy season. If you are travelling in July or August and want a beach, go to the Gulf.

Two coasts, two monsoons

Thailand’s beaches sit on two different seas, and each one takes its rain from a different monsoon.

: Phuket, Krabi, Koh Lanta and Koh Phi Phi

The southwest monsoon hits this side from May to October. It is not constant rain, and Phuket still gets plenty of sunny hours in June. The problem is the sea. Swells build, red flags go up on the west-facing beaches, and rip currents drown swimmers on Phuket every monsoon season. Some boat trips stop running, and the Similan Islands national park closes to visitors altogether from mid-May to mid-October.

November to April is the reliable window, with the calmest water from December to March.

Gulf coast: Koh Samui, Koh Phangan and Koh Tao

The Gulf islands are sheltered from the southwest monsoon and catch the northeast one instead, which brings their heavy rain from October to December. November averages 445 mm on Koh Samui, more than any month in Phuket, and ferries between the islands can be cancelled in rough weather.

From February to August the Gulf is at its best: dry, calm and, in July and August, a safer beach bet than anywhere on the Andaman side.

Thailand’s rainy season, and why it is not a reason to stay home

Officially, the Thai rainy season runs from mid-May to mid-October across most of the country. In Bangkok that usually means one hard storm in the late afternoon, a flooded street for an hour, and a clear evening. September is the wettest month (336 mm) and the one we would skip. June, on balance, is a good month to visit at a discount.

In the north, the rain is heaviest in August and September. Trekking trails turn to mud and some close, but the countryside is at its greenest and the waterfalls are at full volume. Prices drop across the country in these months, most of all in the island resorts, many of which publish a separate low-season rate card from May to October.

Chiang Mai and the north: the smoke season

The north has the best weather in Thailand from November to January: warm days (29–31 °C highs in Chiang Mai), cool nights and dry skies. That is the time to go.

What comes next is less well advertised. From roughly February to April, crop burning and forest fires across northern Thailand and its neighbours push fine-particle pollution in Chiang Mai to levels that, on some days, are among the worst of any city in the world. March is usually the worst month. Visibility drops, the mountains around the city disappear, and anyone with asthma should think twice. The Pollution Control Department’s Air4Thai site publishes live PM2.5 readings; look at the same weeks last year before you book.

Festivals and the weeks that fill up

Period	Dates	What actually happens
Songkran	13 – 15 Apr	Thai New Year and a national holiday. Much of Bangkok’s workforce heads home to the provinces, so buses and trains are full in both directions, and the streets of Chiang Mai and parts of Bangkok become a three-day water fight. Road accident numbers spike every year.
Loy Krathong and Yi Peng	24 Nov 2026 · 13 Nov 2027	The full moon of the twelfth lunar month. Krathong float on rivers and canals everywhere; the lantern release in Chiang Mai fills hotels there months ahead.
Christmas and New Year	late Dec – early Jan	The international peak. Phuket and Koh Samui charge their highest rates of the year, often with minimum stays.
Chinese New Year	6 Feb 2027	Bangkok’s Chinatown (Yaowarat) is packed, and flights from China fill the resorts.

Best month to visit Thailand, by what you want

If you want	Go in	Why
Bangkok, the north and an Andaman beach in one trip	Late November to January	Dry and cool across all three at once.
Koh Samui, Koh Phangan or Koh Tao	February to August	The Gulf’s dry season, out of step with the rest of the country.
Phuket or Krabi	December to March	The calmest sea of the year.
Chiang Mai	November to January	Before the smoke, and around Yi Peng.
Diving the Similan Islands	November to April	The park only opens from mid-October to mid-May.
The lowest prices	May, June or October	Green season rates without September’s rain.

What the month does not decide

Since May 2025, every foreign visitor has had to file the Thailand Digital Arrival Card online in the three days before landing. It is free on the official immigration site; the look-alike sites that charge a fee are not required. Since 15 September 2026, most Western passports get 30 days visa-free instead of 60, so a long trip may need a visa. Our Thailand Digital Arrival Card guide covers the new rule and the online form every visitor files before landing.

If Thailand is part of a longer trip, southern Vietnam’s dry season lines up with Thailand’s, while Vietnam’s central coast does not; see the best time to visit Vietnam. Japan and South Korea are at their best in spring and autumn, when Thailand is either very hot or wet: compare the best time to visit Japan and the best time to visit South Korea.

Once the dates are set, check tipping in Thailand before you land: what to leave for a massage, a guide or a taxi, and when the 10% service charge means you’re done.

All our Thailand guides, from the TDAC to the baht, are sorted by topic in one place: the Thailand travel guide.

Sources

• Thai Meteorological Department — climate normals for Bangkok, Phuket and Koh Samui (1991–2020) and official season dates.
• Tourism Authority of Thailand — festival dates and regional travel seasons.
• Pollution Control Department (Air4Thai) — live PM2.5 readings for Chiang Mai and the north.
• Department of National Parks, Wildlife and Plant Conservation — annual closure of the Similan Islands national park.
• Immigration Bureau — Thailand Digital Arrival Card, official site.
• Alcoholic Beverage Control Act B.E. 2551 (2008) and its notifications — sales bans on Buddhist holidays.

Data checked: 2026-09-28