Thailand Weather in September 2025: Travel Tips for First Visitors

This article is about the weather and travel in September in Thailand. Learn more about average temperatures, rainfall, and tips on what to wear and places to go in September.

Thailand Weather in September: Overview

• Average temperature range: 26–32°C (79–89°F)
• Average rainfall: 137 mm (5.4 inches)
• Rainy days: 17–22
• Sunny days: 5

September is the wettest month in Thailand, especially in the southwest (Phuket etc.), with an average rainfall of about 330 mm (13 in) across the country's popular travel destinations. Heavy downpours are expected most days in the afternoon and evening.

The weather remains hot. However, temperatures continue to decline gradually throughout the month, with an average temperature of 28°C (82°F).

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>>> Best (and Worst) Time to Visit Thailand

Thailand's Regional Weather in September

Bangkok and central Thailand: In September, the weather in Bangkok is quite warm, with daytime temperatures of around 30°C (86°F) and nighttime temperatures of about 25°C (77°F). Rainfall usually occurs in the afternoon and evening in short stormy bursts of one to two hours. When planning your tour, you could schedule outdoor sight-seeing for the morning, to avoid getting drenched.

Chiang Mai and Northern Thailand: Although September falls in its rainy season, northern Thailand experiences less rainfall this month than the southern and central regions. Chiang Mai and Chaing Rai in the north experience average temperatures of about 27°C (82°F) in September.

Southern Islands of Thailand: In September, the southern islands experience varying weather conditions. The islands on the west coast (Phuket, Krabi, Khao Lak) encounter heavy downpours, but those on the east coast Koh Samui etc. are sunnier and brighter with only moderate rainfall.

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The Best Places to Visit in Thailand in September

September is a good time to visit some (eastern) islands. Here we have selected the five best places to visit in Thailand in September so that you can plan a more pleasantly-memorable and hassle-free vacation.

1. Koh Samui

Different from other places in Thailand, the high season to visit Koh Samui is from January to September. Sudden rainfall may occur now and then, but these showers are most likely to occur in the evenings. After dinner, you can take a walk on the beach, appreciate the sunset, and let the cool and fresh breeze blow your cares away.

September is also the perfect time for scuba diving and snorkeling around Koh Samui. There are several lovely, small islands for diving, such as Koh Tao. Alternatively, you can kayak to Ang Thong Marine Park, which boasts 42 islands with pristine white sandy beaches and sheer limestone cliffs.

Suggested read: Best (and Worst) Times to Visit Koh Samui

2. Chiang Mai

The weather in Chiang Mai is mostly sunny in the morning in September. And in the afternoon the rain creates a deep sense of peace and tranquility to this quiet city.

You can take a volunteer program in an elephant sanctuary, or take a Thai cooking class with a local chef, even if it rains, and then get a traditional Thai massage after a full day's activity.

Check the sample itineraries for Thailand tours: 10 days, 14 days, and 21 days >>>

3. Khao Yai National Park

September is the best time to observe the wildlife and admire the waterfalls in Khao Yai National Park, which is one of the most popular national parks, located in northern Thailand. The rain in September allows the forests to be at their lushest, the waterfalls at their fullest, as well as the elephants are at their most active.

Do not miss Haew Suwat Waterfall, which is renowned as the shooting location for Leonardo DiCaprio's waterfall dive in the movie The Beach.

4. Kanchanaburi

September is the best time to see thundering waterfalls as the rivers are then swollen with rain.

Located in Kanchanaburi, Erawan Falls is one of the most splendid waterfalls in Thailand and is the biggest draw in Erawan National Park. During the rainy season, mighty waters rush down into the green pond, which makes for a spectacular sight.

5. Bangkok

Being the capital city and a cosmopolis, Bangkok offers a variety of activities to keep you enthralled in September. The city has many cultural centers, museums, and shopping malls where you can spend a whole day, despite the rain.

Further, on a clear (part of a) day, you can visit Grand Palace, Wat Phra Kaew, Wat Arun, Wat Pho, and China Town.

Suggested read: How to Plan Your First Trip to Thailand — 7 Easy Steps. 

Crowding and Costs in September

September is the wettest month in Thailand, so major tourist attractions and beaches are less crowded. Hotel rates are much cheaper than at the height of the tourist season. Activities rates are also discounted in this month including diving, surfing, snorkeling, and so on.

The exception is the east peninsula coast (the Koh Samui area), which still enjoys only moderate rainfall and relatively high visitor numbers before its torrential rains come in October/November.

Clothes to Wear in September

September is still hot in most parts of Thailand. Light and cool clothes are recommended: shorts, skirts, T-shirts, light trousers, and caps are common wear in September. Remember to bring a raincoat/umbrella and comfortable-when-wet or quick-drying shoes (e.g. Crocs/sandals: wellies would probably be overkill) as it often rains in September.

In the northern cities, like Chiang Mai and Chiang Rai, the temperature can be lower than in the central/southern cities. So, bring some long-sleeved clothes, and long skirts or light trousers to wear when it turns cool in the evenings.

Monthly Weather and Travel Information for Thailand

Learn about the weather in Thailand for 12 months and find out the best places to visit each month.

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