Thailand's weather can change quickly: a bright morning can turn into a heavy downpour by the afternoon. This guide explains what to expect in each season, what to do when a storm, a heatwave or a flood hits, how weather affects flights, boats and roads, and which official sources and phone numbers to use.
Why Thai Weather Feels Unpredictable
Three seasons, each with its own risks
The Thai Meteorological Department (TMD) divides the year into three seasons:
- Rainy season, mid-May to mid-October (the south-west monsoon): heavy showers, thunderstorms and, in the worst weeks, flash floods.
- Cool season, mid-October to mid-February (the north-east monsoon): the driest and most comfortable time in most of the country, with cold mornings in the northern mountains.
- Hot season, mid-February to mid-May: typical daytime highs of 35–39 C, and the hottest days go above 40 C. In the north, this is also the smoke season.
The south does not follow the same calendar. On the Andaman coast around Phuket, the wettest months are August to October. In the Gulf-side south (Koh Samui, Nakhon Si Thammarat, Songkhla), the wettest period is October to December.
Rain rarely lasts all day
Bangkok's wettest month is September, and it has on average about 18 days with 1 mm of rain or more, so many days stay dry or only partly wet. However, a clear morning does not mean a dry afternoon. Plan outdoor sightseeing for the morning and keep indoor options for later in the day.
What TMD expected for 2026
TMD declared the 2026 rainy season officially started on 15 May 2026. Its forecast for the year 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 stays rainy until December.
So if you travel in October 2026, expect the rain in Bangkok, the centre and the north to ease from about the middle of the month, but not yet on Koh Samui or in the rest of the Gulf-side south.
When a Sudden Storm Hits
What to do straight away
- Get under a roof: a shop, a café, a mall, a hotel lobby or the covered area of a temple. Do not shelter under trees in a thunderstorm.
- Put your phone, passport and cash in a dry bag or a sealed plastic bag.
- Stay out of the sea, rivers and pools while there is thunder.
- Wait, and check the rain radar on the TMD website or app to see when the rain is likely to move on.
After the rain
Streets can stay flooded for a while after a downpour. Do not wade or drive through floodwater: you cannot see how deep it is or what is under it. Pavements, temple floors and marble steps get slippery, so walk carefully.
When the Heat Is the Problem
How hot it gets
Bangkok's hottest month is April, with an average daily high of 35.7 C. In Chiang Mai, the average April high is 36.7 C. Thailand's national record is 45.4 C, measured at Tak on 15 April 2023.
Humidity makes the heat feel stronger. In Bangkok, average relative humidity is highest in September (79.3%) and lowest in December (65.6%).
How to cope
- Drink water often, not only when you feel thirsty.
- Do outdoor sightseeing early, and rest in the shade or in air conditioning at midday.
- Wear loose, light, quick-dry clothes, a hat and sunscreen.
Heat stroke
Confusion and hot, dry skin are warning signs of heat stroke, which is a medical emergency. Call 1669 for medical help and move the person into the shade or air conditioning.
Smoke and haze in the north
The hot season also brings smoke to the north. On 4 April 2026, Chiang Mai, Lamphun and Phayao provinces were declared emergency disaster zones because of air pollution, and on 7 April 2026 Chiang Mai ranked as the world's most polluted city. If you visit the north in March or April, check PM2.5 levels on the free Air4Thai app (from the Pollution Control Department) or IQAir AirVisual before you plan a day outdoors.
When It Turns Cold
Cold weather affects only the north and the mountains, mainly from about November to February. Chiang Mai averages 15.7 C at night in January, and its record low is 3.7 C. On high peaks it can freeze: on 27 November 2025 there was frost on Doi Inthanon, Thailand's highest mountain (2,565 m), with 2 C at the summit and -2.3 C at the coldest point, and the park warned that the summit road could be slippery. For a mountain trip in the cool season, bring a warm jacket, long trousers and closed shoes.
Planning Your Trip Around the Weather
- Keep your plans flexible. Have one or two indoor options, such as a museum, a cooking class, a spa or a mall, for a rainy afternoon.
- Check seasonal closures before you book. Some sights close every year because of the weather: the Similan Islands from 16 May to 14 October, Maya Bay (Koh Phi Phi Le) from 1 August to 30 September (it reopens on 1 October 2026), Phu Kradueng National Park from June to September, and the Kew Mae Pan trail on Doi Inthanon from June to October.
- Allow extra time in the Gulf-side south from October to December. It is the wettest season there. In late November 2025, Cyclone Senyar caused severe floods, and Songkhla (Hat Yai) was declared a disaster zone.
What to Pack
- A compact umbrella or a light rain jacket.
- Quick-dry clothes, and sandals or shoes with a good grip for wet floors.
- A light layer for air-conditioned malls, buses and trains.
- A dry bag or sealed plastic bags for your phone and passport, especially on boats and in the rainy months.
- The TMD weather app and, for a trip to the north in March or April, the Air4Thai app, installed before you travel.
When Weather Disrupts Your Transport
Flights
Storms can delay flights, so check with your airline before you leave for the airport. If you have booked a Smile Taxi Service airport pickup, a member of our team checks your flight, and the pickup includes 60 minutes of free waiting, counted from the actual landing time. At Suvarnabhumi and Don Mueang, message us on WhatsApp or LINE once you have your bags, and the car pulls up in about 5–10 minutes.
Boats and ferries
Rough seas can stop boats, so confirm your trip with the operator on the day. For boats and piers, call the Marine Department's 24-hour hotline, 1199.
Roads
Heavy rain can flood roads and, in the north, cause mudslides, as it did in Mae Sai (Chiang Rai) in September 2024. Allow extra time for road journeys, especially in August and September. For help on the highway, call the Highway Police on 1193.
A private transfer in bad weather
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 when you book, per vehicle (not per person), one way, with expressway tolls included, so a slow drive in heavy traffic does not cost more:
| Route | Sedan | SUV | Van |
|---|---|---|---|
| Suvarnabhumi Airport to Bangkok | 600 THB | 800 THB | 1,100 THB |
| Suvarnabhumi Airport to Pattaya | 1,200 THB | 1,500 THB | 1,800 THB |
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).
Book a sedan from Suvarnabhumi Airport to Bangkok, book a van from Suvarnabhumi Airport to Pattaya, or see all Smile Taxi routes and fares.
Official Warnings and Useful Numbers
TMD is the official source for forecasts and warnings. The TMD website in English has 7-day forecasts, rain radar, satellite images, PM2.5 readings and heavy-rain warnings, and its free apps, "Thai Weather" and "TMD พยากรณ์" (TMD Forecast), 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 8-second alarm. If you receive one, follow its instructions.
| Service | Number |
|---|---|
| Police and general emergency | 191 |
| Tourist Police | 1155 |
| Medical emergency | 1669 |
| TMD weather hotline | 1182 |
| DDPM disaster hotline | 1784 |
| Marine Department (boats and piers) | 1199 |
| Highway Police | 1193 |
| Fire | 199 |
FAQ
Who do I call about the weather or a disaster?
Call TMD on 1182 for the forecast and DDPM on 1784 for a disaster. For help, call the Tourist Police on 1155, or 1669 for a medical emergency.
Do ferries stop running in bad weather?
They can, when the sea is rough. Confirm with your operator on the day, or call the Marine Department hotline, 1199.
How hot does Thailand get?
The national record is 45.4 C, measured at Tak in April 2023. Bangkok's average high in April, its hottest month, is 35.7 C.
Whatever the weather, message us on WhatsApp or LINE, or book your transfer online.