Thailand's rainy season officially runs from mid-May to mid-October, and on the Gulf side of the south the rain lasts until December. Even in the wettest months it does not rain every day: Bangkok averages about 18 rain days in September, its wettest month. With some planning, the rainy season can be a good time to travel.
Understanding Thailand's Rainy Season
Official dates and the 2026 season
The Thai Meteorological Department (TMD) defines three seasons: the rainy season from mid-May to mid-October (the south-west monsoon), the cool season from mid-October to mid-February, and the hot season from mid-February to mid-May.
TMD declared the 2026 rainy season officially started on 15 May 2026. Its 2026 forecast expected:
- total rainfall about 10% below normal, and less than in 2025;
- a dry spell from late June to early July;
- the heaviest rain and the highest flash-flood risk in August and September;
- one or two tropical storms affecting Thailand, most likely in August or September and mainly in the north and north-east;
- the rain in upper Thailand ending about mid-October 2026, while the Gulf-side south (Samui, Nakhon Si Thammarat, Songkhla) stays rainy until December.
Regional rain patterns
The figures below are 1991–2020 averages from TMD station data, not forecasts.
| Place | Wettest month | Average rain that month | Average rain per year |
|---|---|---|---|
| Bangkok | September | 335.9 mm | 1,702 mm |
| Chiang Mai | August | 223.3 mm | 1,139 mm |
| Phuket (Andaman coast) | September | 350.4 mm | 2,271 mm |
| Koh Samui (Gulf coast) | November | 444.6 mm | 1,994 mm |
| Pattaya (east of Bangkok) | October | 224.5 mm | 1,106 mm |
In Bangkok, October is almost as wet as September, with about 289 mm.
Andaman coast and Gulf coast
The two coasts of the south follow different calendars:
- Andaman coast (Phuket, Krabi, the Similan and Phi Phi islands): rain builds from May, and August to October is the wettest period. Phuket has about 19 rain days in both September and October.
- Gulf coast (Koh Samui and the Gulf-side south): February to September is the drier stretch. September on Samui gets about the same rain as June to August. The wet peak is October to December, with November the wettest month.
Best Places to Go in the Rainy Season
The Gulf coast from May to September
From May to September, when the Andaman coast is wet, Koh Samui gets far less rain than Phuket and is usually the better beach choice. In August, for example, Samui averages 102.2 mm and Phuket 308.7 mm. In October both islands are wet: about 295 mm on Samui and about 336 mm on Phuket. In November and December the Gulf-side south is at its wettest, and Phuket gets much less rain than Samui. For travel options, read our guide on how to get from Bangkok to Koh Samui.
Northern Thailand
In the rainy season the north is green, and the smoke season of March and April is over. Chiang Mai's wettest month is August, and September is almost as wet.
At Doi Inthanon National Park, Thailand's highest mountain, the summit, the chedis and the waterfalls stay open in the rainy season. Some trails and parks close in these months (see the list of seasonal closures below). For travel options to the north, read our guide on how to get from Bangkok to Chiang Mai.
Pattaya
Pattaya is drier than Bangkok, with about 1,106 mm of rain a year against 1,702 mm in Bangkok. Its wettest months are September and October.
Seasonal closures to check
Some famous sights close for the monsoon every year:
- Similan Islands: closed from 16 May to 14 October. The 2026–27 season opens on 15 October 2026.
- Maya Bay (Koh Phi Phi Le): closed from 1 August to 30 September for reef recovery. In 2026 it reopens on 1 October. Phi Phi boat tours keep running during the closure but do not enter the bay.
- Kew Mae Pan nature trail (Doi Inthanon): closed from June to October every year. It reopens on 1 November.
- Phu Kradueng National Park (Loei): closed from June to September every year.
If you plan to snorkel or dive in a marine national park, bring sunscreen without oxybenzone. Since August 2021, sunscreens with coral-harmful chemicals have been banned in all marine national parks, with fines of up to 100,000 THB.
Practical Rainy Season Tips
What to pack
- A light rain jacket or a compact umbrella
- Quick-dry clothes
- Sandals or shoes with a good grip for wet streets and temple floors
- A dry bag for your phone and passport, especially on boats
- A light layer for air-conditioned malls, buses and trains
Planning your day
Plan outdoor sightseeing for the morning and keep indoor options, such as museums, cooking classes, spas or shopping malls, for later in the day. Keep some free time in your plans, so that one heavy shower does not spoil a whole day.
Checking the forecast
TMD's website, tmd.go.th, has 7-day forecasts, rain radar, satellite images and heavy-rain warnings, and its weather hotline is 1182. TMD's free apps, "Thai Weather" and the newer "TMD พยากรณ์" (TMD Forecast), show forecasts, radar and satellite images, and both are available in English.
Thailand also has T-Alert, a national warning system run by the Department of Disaster Prevention and Mitigation (DDPM). Warnings pop up on phones in the affected area with an alarm, as they did for Chao Phraya flood warnings in November 2025. If you receive one, follow its instructions.
Getting Around in the Rain
In town
Tuk-tuks and songthaews (the pick-up trucks with benches) are open at the sides, so you may get wet in a downpour.
Between cities
Allow extra time for road journeys. For 2026, TMD expected the heaviest rain and the highest flash-flood risk in August and September. In the north, heavy rain can cause floods and mudslides, as it did in Mae Sai (Chiang Rai) in September 2024. For help on a highway, call the Highway Police on 1193.
Private transfers
A private transfer takes you from door to door, so you do not wait at a bus stop or a pier in the rain. Smile Taxi Service fares are fixed per vehicle (not per person), one way, with expressway tolls included. The fare is the same for 1 passenger or a full car:
- Suvarnabhumi Airport to Pattaya: 1,200 THB by sedan, 1,500 THB by SUV, 1,800 THB by van. Book a sedan from Suvarnabhumi Airport to Pattaya.
- Bangkok to Pattaya: 1,500 THB by sedan, 1,700 THB by SUV, 2,000 THB by van. Book a sedan from Bangkok to Pattaya.
- Chiang Mai to Chiang Rai: 2,500 THB by sedan, 3,000 THB by SUV, 3,800 THB by van. Book a sedan from Chiang Mai to Chiang Rai.
If a storm delays your flight, a member of our team checks the new arrival time, and airport pickups include 60 minutes of free waiting, counted from the actual landing time. You pay the driver in cash (THB) at the end of the trip. If you can only pay by card, message the team for a PayPal payment link (a 5% fee is added). Cancellation is free up to 24 hours before pickup. After that, a cancellation or change costs 25% (less than 24 h), 35% (less than 12 h) or 50% (less than 2 h) of the price, and a no-show 100%, also when you pay the driver in cash (details). See all Smile Taxi routes and fares.
Boats and islands
Rough seas can stop boats. Confirm your ferry or boat trip with the operator on the day, and for questions about boats and piers call the Marine Department's 24-hour hotline, 1199.
Health and Safety
- Do not wade or drive through floodwater.
- Do not shelter under trees in a thunderstorm.
- On the Gulf-side south from October to December, leave extra time in your plans. In late November 2025, Cyclone Senyar caused severe floods there, and Songkhla (Hat Yai) was hit hardest.
Useful numbers: 191 police and general emergency, 1155 Tourist Police, 1669 medical emergency, 1784 DDPM disaster hotline, 1182 TMD weather hotline.
Festivals and Holidays in the 2026 Rainy Season
| Date (2026) | Event |
|---|---|
| 29 July | Asalha Bucha (public holiday) |
| 30 July | Start of Buddhist Lent (Khao Phansa) |
| 12 August | Queen Mother's Birthday and Mother's Day (public holiday) |
| About 10–18 October | Phuket Vegetarian Festival, Phuket Old Town |
| 12–16 October | IMF / World Bank Group Annual Meetings in Bangkok; 16 October is a Bangkok-only holiday |
| 13 October | King Bhumibol Memorial Day (public holiday) |
| 23 October | Chulalongkorn Day (public holiday) |
| 26 October | End of Buddhist Lent (Ok Phansa) |
During the meetings week in Bangkok, allow extra time for travel and security checks.
FAQ
Does it rain all day in the rainy season?
Not usually. Bangkok has about 18 rain days in September, its wettest month, so many days stay partly dry.
Where is the weather better in August?
On the Gulf coast. Koh Samui averages 102.2 mm of rain in August, against 308.7 mm in Phuket.
Can I visit Maya Bay or the Similan Islands in the rainy season?
Maya Bay is open except from 1 August to 30 September. The Similan Islands are closed from 16 May to 14 October and open again on 15 October, near the end of the rainy season.
Does a private transfer wait if my flight is delayed by a storm?
Yes. A member of the Smile Taxi team checks your new arrival time, and airport pickups include 60 minutes of free waiting, counted from the actual landing time.
Travelling in the rainy season? Message us on WhatsApp or LINE, or book your transfer on our booking page.