The weather for Thailand in summer, especially August, is typically wet as monsoon rains move in to clean the air and cool temperatures a little until fall.
Although the summer rainy season is also the “low season,” Thailand is such a popular destination that many places will hardly see a difference in tourist arrivals. The rain is usually welcome after scorching hot temperatures and humidity that build through Songkran, the traditional New Year celebration, in April.
Bangkok in Summer
Bangkok is hot and rainy during the summer months. Although temperatures are a few degrees cooler than the scorching temps in April and May, you’ll never feel “cold” in Bangkok. Temperatures don’t dip down much after sunset. Instead, nights become steamy and sticky as pollution traps humidity and creates an urban greenhouse.
As the southwest monsoon moves through, low-lying areas around the Chao Praya River are subject to annual flooding. The floods have gotten worse year after year, exasperating traffic as additional roads close.
June is considerably less rainy than May in Bangkok, but precipitation builds with strong showers until September -- the wettest month.
Bangkok’s Average Temperatures in Summer
Summer temperatures in Bangkok average 84 degrees Fahrenheit (29 degrees Celsius) with highs well above 90 degrees Fahrenheit.
On some afternoons, temperatures climb over 100 degrees Fahrenheit (37.8 degrees Celsius)!
You’ll obviously want breathable, loose-fitting clothing for those three-shower days while walking around the city. If the heat becomes unbearable, there are some nearby escapes for getting out of the city.
Chiang Mai in Summer
Like Bangkok, Chiang Mai usually receives more rainfall in May than June, but wet days increase until the monsoon peaks in August or September.
The night air can feel cool sometimes in Chiang Mai during summer, especially after hot, summer afternoons. Temperatures remain fairly consistent with lows around 73 degrees Fahrenheit (23 degrees Celsius) and highs around 88 degrees Fahrenheit (31 degrees Celsius).
The Thai Islands in Summer
The climate differs for the Thai islands in summer, depending upon which side of Thailand.
Koh Chang in the Gulf of Thailand receives the most rainfall in June, July, and August, but rain isn’t too bad in Koh Samui and surrounding islands until around October. The wettest months on Koh Samui are October, November, and December.
Meanwhile, on the other side of Thailand, the monsoon hits Phuket and the islands in the Andaman Sea around May. Rainfall drops off sharply by December.
Summer is rainy and therefore the “low season” in Thailand, but you may never notice on some islands. University students from around the world take advantage of summer breaks to go backpacking and party hard on islands such as Koh Tao, Koh Phangan, and Koh Phi Phi.
Traveling families also seize the opportunity to travel while children are out of school.
Thailand isn’t the only place to party for backpackers in summer. The weather in Malaysia’s Perhentian Islands and Indonesia’s Gili Islands is actually better in the summer. Even perpetually busy Bali gets a little busier in summer as Australians grab cheap flights to escape their winter months.
Some islands, such as Koh Lanta on the west coast of Thailand, mostly shut down after June as storms move through. A few businesses will remain open, but there won’t be as many choices for eating and sleeping. With a little luck, you can have perfect beaches nearly all to yourself in early summer.
Seasonal Fires in Northern Thailand
Each year, slash-and-burn fires get out of control in Northern Thailand causing terrible smoke and haze to choke Chiang Mai.
Particulate levels consistently reach dangerous thresholds, prompting locals to wear masks and the airport to close due to low visibility.
Despite the government’s promises and efforts to get the problem under control each year, the fires rage on during the dry months. March and April are two of the worst months for smoke from fires; the problem continues until rainfall increases enough to clean the air and get fires under control.
The fires usually aren’t bad in June, but if the monsoon is delayed, air quality could still be an issue. Travelers with respiratory conditions should check the situation before booking a trip to Chiang Mai or Pai.
Summer Festivals in Thailand
After Songkran in April and Coronation Day on May 5 (a public holiday commemorating the coronation of King Bhumibol Adulyadej), there aren’t many large festivals in Thailand until fall.
The most notable event for travelers is the Queen’s Birthday on August 12, which also serves as Mother’s Day in Thailand. Public stages are erected with cultural shows and a candlelight ceremony is held in the evening, followed by fireworks in honor of Queen Sirikit (born in 1932).
A few Buddhist public holidays (dates change according to the lunar calendar) take place in June and July, however, travelers hardly notice beyond the ban on alcohol sales that day.
The Amazing Thailand Grand Sale
Each summer, the Tourism Authority of Thailand hosts the Amazing Thailand Grand Sale from mid June to mid August in an effort to promote tourism -- and especially spending -- during the low-season months. Shops that are part of the summer sale display a special logo and offer discounts purportedly up to 80% off regular prices.
Although the focus of the sale is primarily retailers in shopping malls around Bangkok, Chiang Mai, and Phuket, some hotels and airlines offer special rates as well.