Traveling Thailand in summer (June, July, and August) requires accounting for periods of rain.
The Southwest Monsoon will be in full swing with rainy days increasing steadily until September and October. But there is some good news: Rain cleans the hazy air of dust and smoke, and tourist numbers in some places will be a little less than usual.
In fact, the number of backpackers increases a bit as many students take a break from school. Australian travelers escaping winter in the Southern Hemisphere often begin trips in Bali, but some grab cheap flights up to enjoy Thailand's islands.
The summer rain is usually welcome after scorching hot temperatures, humidity, and haze that build through Songkran, the traditional New Year celebration, in April.
Bangkok Summer Weather
Bangkok is hot and rainy during the summer months, especially August.
Although temperatures are slightly less oppressive than the scorching numbers 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 around the city as additional roads close.
Although the increase in rain between April and May is drastic, June is generally less rainy than May in Bangkok. Precipitation builds with stronger and stronger showers until September—the wettest month.
Bangkok’s Average Temperatures in Summer
Summer temperatures in Bangkok average around 84 F (29 C) with highs well above 90 F. On some afternoons, temperatures approach 100 F (37.8 C)!
You’ll obviously want breathable, loose-fitting clothing for those three-shower days while walking around the city. If the urban 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.
August is usually much rainier than July in Chiang Mai. If your travel dates are flexible, try to arrive early in July rather than August.
Much to the relief of everyone, the rain usually puts out the many fires burning in the region. The air finally gets cleaned of unhealthy particulate matter that causes respiratory issues.
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 F (23 C) and highs around 88 F (31 C).
Summers in Chiang Mai are usually pleasant. April is usually the hottest month in Chiang Mai, and December is the mildest.
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 farther south in Koh Samui and surrounding islands until around October. The wettest months on Koh Samui are often 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.
When choosing an island in Thailand to visit during summer, take into consideration that the weather in the Gulf of Thailand will be less rainy. Koh Samui, Koh Phangan, and Koh Tao experience less rain in summer than the islands on the west coast.
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.
Parties in the Summer
Summer is rainy and therefore the “low season” in Thailand, but popular party islands remain busy. University students from around the world take advantage of summer breaks to go backpacking and party hard on islands such as Koh Tao, Koh Phi Phi, and at Haad Rin on Koh Phangan. 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 more crowded in summer as travelers go to take advantage of the dry season in the southern part of Southeast Asia.
Summer Holidays and 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 aside from holidays to observe royal birthdays.
The most notable event for travelers is King Maha Vajiralongkorn's Birthday celebrated on July 28. This holiday is not to be confused with King Bhumibol's (the former King of Thailand) birthday on December 5.
The Queen’s Birthday on August 12 also serves as Mother’s Day in Thailand. Public stages are erected with cultural shows and a candlelight ceremony is held in the evening, sometimes followed by fireworks in honor of Queen Sirikit (born in 1932).
A few Buddhist public holidays such as Buddhist Lent (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 percent 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. In 2017, the event was renamed the Thailand Shopping & Dining Paradise to put food and dining more in the spotlight.
Seasonal Fires in Northern Thailand
Each year, fires (some are natural, but many are set illegally) 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 Chiang Mai's airport sometimes closes 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.