The major tourist capitals including Bangkok, Chiang Mai, Ko Samui, and Phuket all average 17 to 19 rainy days during the month of September, ranking it among the wettest months of the year. The monsoons create heavy downpours which are often characterized by powerful thunder and lightning. Some years, the storms even flood roads or cause certain areas to be evacuated.
However, most of the time the showers are very short. In fact, when it's not actively raining, it can be hard to tell it's the rainy season—the weather is hot and it's frequently sunny. Temperatures average 90 degrees Fahrenheit everywhere except the western Andaman coast which is slightly cooler (at around 86 degrees). Lows at night average 73 to 77 degrees, depending on where you are in the country.
Crowds and Costs
Being one of the wettest months of the year, there aren't heavy crowds in September. On the contrary, it's a time when the beaches empty out and even the northern and central towns get less crowded. You'll still see lines at the major tourist sites such as Bangkok's Grand Palace, and it's unlikely you'll spend the whole trip without spotting a fair share of giant-sized tour buses rolling by. Still, the number drops dramatically compared to the high season.
In addition to fewer people, visiting Thailand in September has the added benefit of costing much less. Hotels offer rates cheaper than any other time of year—sometimes half the high season price—and select activities are discounted, too. As a bonus, the rains make the countryside green and beautiful.
Where to Go
Bangkok is one of the best places to visit in September. It's an urban metropolis with top-rate restaurants, chic art galleries, and swanky cocktail bars. Many of its biggest draws are activities that occur indoor anyway, as opposed to outdoor activities like the beaches and mountains. They are attractions that won't be spoiled by the rain. Even the famous temples and palaces are largely indoors, though some sites are in gardens and open-air pavilions. Nevertheless, Bangkok makes a great September destination. Just keep in mind that it's hot and muggy, so dress appropriately.
Chiang Mai can be an enjoyable destination this time of year, too. The afternoons get rainy but the mornings are often sunny and clear, making it perfect for wandering the city, checking out the shopping districts, or visiting the temple on the hill. Chiang Rai, about three hours north, is similar this time of year with morning sunshine and afternoon showers. There are plenty of indoor activities there as well, in addition to a number of elephant sanctuaries in the surrounding areas. In the nearby mountains, the scenery is exploding with green foliage this time of year.
The beaches can be hit and miss during September but given the sheer lack of crowds, it's often a worthy gamble. Even at the higher-end resorts, the prices are often half the high-season rates, and if you do get rain, there are plenty of indoor things to do such as getting a massage, visiting a temple, or taking a cooking class. It rains 18 to 19 days a month during September but, like destinations farther north, it doesn't last all day. When you do get periods of sunshine, there's beautiful swimming and snorkeling, and you can enjoy the beaches with half the crowds.
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What to Do
If you head to the capital city, take advantage of the wide variety of food and dining options. Stroll through trendy districts like Ekamai, Thonglor, or Sathorn. In the evening, catch a movie at the historic Scala Cinema or check out an art show at the Queen Sirikit Gallery. If you're into history and religion, try visiting Wat Pho (the "Temple of the Reclining Buddha"), which houses the 150-foot-long reclining Buddha, or stop by the Grand Palace complex where Thai royalty lived for centuries.
In Chiang Rai, walk through the impressive Wat Rong Khun (also known as the "White Temple") or have an ethical elephant experience with rescued animals at the Elephant Valley Thailand sanctuary. If it's raining, try the Oub Kham Museum or the Hilltribe Museum. In Chiang Mai, hike up to the Doi Suthep temple, or go shopping on Nimmanhaemin Road.
On the beaches of the Kra Isthmus, the western coast offers excellent snorkeling and scuba diving opportunities near Phuket when it's sunny, as well as things like Wat Chalong temple or the Phuket FantaSea variety show when it's raining. On the Gulf of Thailand side, head to Ko Samui for surfing, kiteboarding, or other adrenaline activities.
There are also lots of indoor attractions such as spa treatments or cooking classes. If you'd rather have someone else do the planning and logistics, this 5-day "A Taste Of Southern Thailand" offers a variety of coastal excursions including a visit to the pristine beaches of Khao Lak and a fishing village called Ban Samchong.
Events in September
Phuket Vegetarian Festival: The Phuket Vegetarian Festival, which is also referred to as the Nine Emperor Gods Festival or the Kin Jay Festival, is a wild, chaotic event that occurs for roughly a week every September. Celebrated primarily by the Chinese Thai community, it involves participants walking on nails and hot coals, climbing knife-laden ladders, and piercing their cheeks with swords.
Traveling to Thailand in September? Check out this great itinerary
Ultimate Highlights of Thailand – 10 Days. This unique 10-day tour offers participants the chance to experience many parts of the Thai culture and landscape. With destinations including Bangkok, Chiang Mai, and Koh Samui, you'll get to visit the pristine Angthong Marine Park, take a food tour in Bang Rak, and spend time with rescued elephants at the Patara Elephant Farm.