Thailand in the rainy season: where to go, month by month

Rainy season 2026-2027: where do we stand, month by month?

The usual calendar of the season, from October to September, with average rainfall and rain days by region.

The 2026-2027 rainy season follows the usual calendar: in Bangkok, the north and on the Andaman coast the rain returns in May 2027 and peaks in September; the Gulf of Thailand gets its rain from October to December, with 445 mm in Koh Samui in November. From November to April Bangkok and the north are dry, and the Andaman side dries out from December. The table starts in October and gives, for each region, the millimetres and rain days of an average year (1991–2020); it does not forecast the weather of a given year.

When is the rainy season in Thailand? The two monsoons explained simply

Forget the idea of one national rainy season: Thailand has two wind systems that hit its coasts at different times.

From roughly May to October the southwest monsoon blows moist air off the Indian Ocean onto the west-facing Andaman coast and inland over Bangkok, the centre and the north. Phuket, Khao Lak, Krabi, Koh Phi Phi and Koh Lanta sit directly in its path, which is why their seas turn rough and grey in these months. The Gulf of Thailand islands, sheltered behind the mountains of the peninsula, stay comparatively dry during the same period.

Around October the winds reverse. The northeast monsoon then brings its moisture across the Gulf of Thailand, so Koh Samui, Koh Phangan and Koh Tao get their heaviest rain from October to December, often peaking in November. At the same time the north and Bangkok dry out and the Andaman coast begins its high season. In short: west coast wet in the European summer, east-side islands wet in the European autumn.

In most places the rainy season does not mean constant rain. A typical day starts bright and humid, clouds build up by early afternoon and a heavy tropical shower falls for thirty minutes to two hours, often with thunder, before the sky clears again for the evening. Many days are completely dry. The real problem is the occasional low-pressure system that parks over a coast and brings two to four grey, windy days in a row, which happens most often at the peak of each monsoon.

On the Andaman coast the bigger issue is often the sea rather than the rain: strong swell, murky water and red flags on west-facing beaches such as Patong, Kata and Karon in Phuket. In Bangkok a downpour can flood streets for an hour and jam traffic, so allow extra time before a flight. In the north, rain makes mountain roads slippery and trekking paths muddy, but it also fills the waterfalls and turns the rice terraces bright green.

Where to go in Thailand in the rainy season: month by month and by region

The table gives the general picture; the notes below say where to go and where to avoid each month.

The table at the top of the page gives the rain that actually falls: millimetres and days with rain per month, for one station per region. The rainy season does not start and end in the same month everywhere.

Think of the year as a relay between the coasts. From May to October the Gulf islands hold the best beach weather while the Andaman side and the north take the rain; October is the handover month; from November the Andaman coast and the north are at their best while the Gulf gets its turn. Bangkok is visitable all year, with short, heavy showers from June to October. Always check the forecast a week out, as the monsoon can arrive or leave a few weeks early or late.

• May: a shoulder month. Go to the Gulf islands or Bangkok; the Andaman coast is still fine early in the month but seas build. Avoid planning Similan trips, as the park closes every year on 15 May.
• June: go to Koh Samui, Koh Phangan or Koh Tao and to Chiang Mai while it is still fairly dry. Avoid relying on Andaman speedboat day trips.
• July: go to the Gulf islands for beaches, combine with Bangkok and the north. Avoid swimming off west-facing Phuket beaches with red flags.
• August: same verdict as July, but busier and pricier on Koh Samui with European holidays. Avoid Koh Chang if you want sunshine.
• September: the hardest month overall. The Gulf islands are the safest bet; avoid remote Andaman islands, small resorts and trekking in the north.
• October: a transition month. The Gulf gets wetter, the Andaman and north improve in the second half. Go to Chiang Mai, Bangkok or Krabi late in the month.
• November: go to the Andaman coast (Krabi, Koh Lanta, Phuket, Khao Lak) and the north for Loy Krathong. Avoid Koh Samui, Koh Phangan and Koh Tao if beaches are the main goal.
• December: almost everywhere is good except the Gulf, which improves through the month. Book ahead, as this is peak season.

Rainy season in Bangkok 2026: when, how much, how to plan

In Bangkok the official averages rise from 93 mm in April to 217 mm in May and stay high until October. The wettest months are September (336 mm over 18 days) and October (289 mm over 14.4 days). In November only 45 mm falls and in December 12 mm: the dry season starts in November.

Even in the wettest month Bangkok is easy to visit. Rain usually comes as a heavy shower in the afternoon or evening, so plan temples, museums and markets for the morning. If you travel in the rainy season in 2026, check the forecast a week ahead, as the monsoon can shift by a few weeks. For temperatures and rain month by month, see our Bangkok weather page and the Bangkok travel guide.

Which Thai islands are best in the rainy season? Island-by-island verdict

For a beach holiday between June and September, the Gulf islands are the clear winners, and Koh Samui is the easiest because it has an airport, many sheltered bays and plenty of indoor options. From November to April the ranking flips and the Andaman islands shine. The table below gives a simple verdict for the most popular islands; note that the south of the Andaman coast (Koh Lipe) and the east (Koh Chang) have their own timings.

Ferries, speedboats and diving in the rainy season

The rainy season has a direct effect on boats. On the Andaman side, many speedboat routes linking Phuket, Krabi, Koh Phi Phi, Koh Lanta and Koh Lipe run a reduced low-season schedule, and some island-hopping connections stop altogether. Crossings can be rough and are occasionally cancelled when the marine department issues wind warnings. Large car ferries and big catamarans are more reliable than small speedboats, which are the first to be pulled.

In the Gulf, the Lomprayah and Seatran Discovery catamarans between Chumphon, Koh Tao, Koh Phangan and Koh Samui run year round, but the November crossing can be very choppy. For diving, the Similan and Surin national parks close every year from 15 May to 15 October, so Andaman liveaboards stop. Koh Tao is the natural alternative, with generally calmer water and decent visibility from about June to September. The Department of National Parks confirms the exact dates each year, so check before you book.

• Leave a buffer day between an island ferry and an international flight
• Prefer morning departures, when seas are usually calmer
• Book flexible tickets and keep the operator's contact details
• Take seasickness tablets before rough crossings, not during
• Pack electronics in a dry bag on speedboats

What to do in Thailand when it rains

Plenty of activities still work, and some are better in the green season. Waterfalls such as Erawan near Kanchanaburi or those around Chiang Mai are at their fullest, national parks like Khao Sok are lush and misty, and rice terraces in the north glow green in July and August. In cities, heavy showers are simply a cue to head indoors for an hour.

Low-season prices and crowds: how much can you save?

Outside the Gulf in July and August, the rainy season is Thailand's low season, and hotel prices on the Andaman coast often drop noticeably compared with December to March. Mid-range and upmarket resorts are where the discounts are most visible, and you can often book good rooms at short notice. Flights from Europe are driven more by school holidays than by Thai weather, so July and August fares stay high even when hotels are cheap.

Is it safe to travel to Thailand in the rainy season?

Yes, for most travellers, provided you respect the sea and the roads. The main risks are drowning in rip currents on Andaman beaches, scooter crashes on wet roads, local flooding in Bangkok and parts of the centre or north around September and October, and mosquito-borne diseases such as dengue, which increase in the wet months. Landslides can occasionally close mountain roads in the north.

• Swimming when a red flag is flying, especially at Patong, Kata, Karon or Khao Lak
• Riding a scooter in heavy rain or at night on wet roads
• Trekking or canyoning after days of heavy rain
• Booking a same-day ferry and international flight
• Skipping mosquito repellent at dawn and dusk

Last reviewed September 2026. Most trips are never affected, but it pays to know where and when water rises.

Flooding in Thailand follows the monsoons. It usually hits specific provinces for days or weeks rather than the whole country, and tourist areas often keep running normally while nearby rural districts are under water.

• 2011: the worst floods in decades covered large parts of the central plains and northern Bangkok for weeks.
• September 2024: rain linked to Typhoon Yagi caused severe floods in Chiang Rai province, including the border town of Mae Sai and Chiang Rai city.
• November 2025: severe floods hit the southern provinces, notably Hat Yai and Songkhla, while Bangkok, Chiang Mai and Phuket were reported unaffected by TAT.

• Follow the Thai Meteorological Department (tmd.go.th) warnings and the DDPM (Department of Disaster Prevention and Mitigation)
• Read the TAT newsroom (tatnews.org) for travel condition updates
• Register with and follow your embassy's travel advice
• Take travel insurance that covers weather disruption and cancellations
• Prefer flexible, refundable bookings from August to November
• Expect ferries to be cancelled when the TMD issues high-wave warnings

Travelling in the green season: pros and cons

Whether the rainy season suits you depends on flexibility. If you can move between coasts and accept a few showers, you gain lower prices, empty viewpoints and dramatic landscapes. If your trip is short and built around one Andaman beach or specific boat trips, the risk of disappointment is higher.

• Lower hotel prices and easy last-minute availability
• Lush green landscapes, full waterfalls and rice fields
• Fewer crowds at temples, viewpoints and beaches
• Slightly cooler temperatures than in the hot season

• Rough seas and red flags on Andaman beaches
• Reduced or cancelled ferries and speedboats on some routes
• The Similan and Surin national parks close every year from 15 May to 15 October
• Some small island resorts and restaurants close for the season
• More mosquitoes, so dengue precautions matter

What to pack for the rainy season in Thailand

Heavy waterproof gear is unnecessary in 28 to 33 degree heat. What helps is light, quick-drying clothes, protection for electronics and footwear that can get wet. Anything you forget is easy to buy in any 7-Eleven or local market, from ponchos to umbrellas. For a complete list, use our packing list generator for Thailand.

• A thin rain jacket or a cheap poncho rather than a heavy coat
• A compact umbrella, useful for both rain and sun
• Quick-dry clothing and a spare set in a plastic bag
• Sandals or water shoes that can get soaked
• A dry bag and a waterproof phone pouch for boats
• Strong mosquito repellent (DEET or icaridin)
• Seasickness tablets if you plan island hopping
• Travel insurance that covers weather disruptions

Sample rainy-season itineraries

The simplest strategy is to pair the region that is dry with cities or the north, which suffer less from rain than the sea does. Use these templates as starting points and adjust once you see the forecast.