Best time to visit Thailand: a month-by-month guide

For most of Thailand the best time to visit is November to February, when the northeast monsoon brings cooler, drier weather to Bangkok, the north and the Andaman coast around Phuket and Krabi. The Gulf islands such as Koh Samui are the exception: their wettest spell usually runs from about October to January, so they are often better from February to September. March to May is hot everywhere, and mid-May to mid-October is the main rainy season.

That simple rule hides a lot of useful nuance. Rain in the wet season tends to come in heavy bursts rather than all-day drizzle, the north cools down noticeably in December and January, and some marine parks close completely for part of the year. The sections below explain the seasons, the regional differences and the festivals worth planning around, so you can decide whether to aim for peak season or a quieter shoulder month on a trip through Thailand.

Thailand's three seasons at a glance

Thailand's government portal divides the year into three seasons. Summer, the hot season, runs from roughly mid-February to mid-May and peaks in mid-April, when daytime highs of 35–39°C are typical and some days pass 40°C. The rainy season follows from about mid-May to mid-October as the southwest monsoon arrives; there is often a short lull around late June before persistent rain returns in July. The cool season, which Thais call winter, lasts from mid-October to mid-February, when the northeast monsoon brings cooler, drier air, especially in the north and northeast.

• Cool season (mid-October to mid-February): the most comfortable weather for sightseeing in Bangkok, Ayutthaya and Chiang Mai, and calm seas on the Andaman coast.
• Hot season (mid-February to mid-May): long sunny days, very high temperatures inland, and good conditions on the Gulf coast.
• Rainy season (mid-May to mid-October): greener landscapes, short heavy downpours, rougher Andaman seas and fewer visitors.

Month-by-month guide

Regional differences: Andaman coast vs Gulf of Thailand

The two coasts sit on opposite sides of the peninsula and are hit by different monsoons. According to the UK Met Office, the Andaman side, including Phuket, Krabi and the Phi Phi Islands, has its wet season from about May to October under the southwest monsoon and is calmest from November to February. The Gulf side, including Koh Samui, Koh Tao and Koh Chang, gets its most consistent rain from October to January, peaking in November, so April to September is often the better time there.

Thailand's own seasonal guidance adds that heavy rain can continue in the south until December, sometimes causing flooding, and that the eastern region holds onto rain and thunderstorms longer into the autumn than the north. If your heart is set on a winter-sun trip in December, the Andaman coast is usually the safer bet; if you can travel in July or August, the Gulf islands are worth a look.

Bangkok and the central plains

Bangkok is a year-round city, but November to February is far more comfortable for walking between the Grand Palace, Wat Pho and the riverside. In April the heat is intense, and from June to October expect afternoon storms that pass quickly. Day trips to Ayutthaya work in any month if you start early.

Chiang Mai and the north

The north and northeast are the first regions to cool down from mid-October, and nights can feel genuinely chilly in December and January, particularly at altitude in Doi Inthanon National Park. The UK government notes that Chiang Mai and Bangkok can suffer high air pollution and seasonal smoke haze from crop and forest burning, which is typically worst in the hot, dry months; travellers with asthma or other respiratory conditions should check air-quality forecasts before travelling between February and April.

Festivals and events worth planning around

• Songkran (mid-April): the Thai New Year, inscribed by UNESCO on its Intangible Cultural Heritage list in 2023. Expect water-throwing street celebrations, temple ceremonies and heavy domestic travel; book transport well ahead.
• Loy Krathong (usually November): on the full moon of the twelfth lunar month, people float small decorated baskets on rivers and lakes. The date moves each year with the lunar calendar.
• Yi Peng (Chiang Mai, same period as Loy Krathong): the northern lantern festival, best experienced on a short stay among the temples of Chiang Mai.
• Christmas and New Year: not traditional Thai festivals, but the busiest weeks at beach resorts, with the highest hotel rates.

Marine park seasons and wildlife

Some national marine parks close for part of the monsoon. Thai authorities closed the Similan Islands to tourism and overnight stays from 15 May to 15 October in 2026, giving reefs and beaches time to recover, and a similar closure is normal each year. Diving and snorkelling on the Andaman side is therefore best planned between late October and April. On the Gulf side, Koh Tao and Ang Thong National Marine Park are usually more reliable in the middle of the year.

Inland, the rainy season turns forests and rice fields a vivid green and waterfalls are at their fullest, but the UK government warns that rivers and waterfalls can have dangerous currents and that flash floods and landslides are possible in mountainous areas. Jungle stays in Khao Sok National Park are possible all year, though trails are muddier from June to October.

Crowds and prices through the year

The cool season from November to February is high season: hotels, flights and island boats fill up, and the weeks around Christmas, New Year and Chinese New Year are the most expensive. March and April are busy with domestic travellers around Songkran. The rainy months from June to September are usually the best value, with lower hotel rates at many resorts, especially on the Andaman coast. For a full breakdown of what drives price, see our guide to what a Thailand trip costs.

If this is your first visit, our Thailand travel guide for first-timers covers entry rules, money and getting around. When you know your dates, a specialist can match the right coast to your month: tailor a Thailand itinerary or browse ready-made ideas such as Bangkok, Chiang Mai & Phuket.

Frequently asked questions

Sources

1. Thailand.go.th — The Seasons of Thailand
2. Met Office — Thailand holiday weather
3. UNESCO — Songkran in Thailand, traditional Thai New Year festival
4. The Nation Thailand — Similan Islands closure for 2026 monsoon season
5. GOV.UK — Thailand travel advice: safety and security
6. GOV.UK — Thailand travel advice: health