It's wise to study the weather information below, as an ill-timed trip can mean pouring rain, debilitating humidity, or seas too rough for diving or beach activity. The high season for tourism throughout the kingdom is the North American/European winter period, mid-October through late February. Prices skyrocket and hotels fill up then, so be sure to make advance reservations. Off-season weather, however, is not intolerable, and some travelers report joyfully trading the crowded beaches and high prices of high season for a bit of off-peak discomfort. Low season is generally composed of the odd rainy afternoon, significant savings, and a lot more elbowroom. Because this coincides with school holidays in the U.S. and Europe, there is a mini high season in July/August when families head for the kingdom.
Thailand has two distinct climate zones: tropical in the south and tropical savanna in the north. The northern, northeastern, and central areas of the country (including Bangkok) experience three distinct seasons. The hot season lasts from March to May, with temperatures averaging in the upper 90s Fahrenheit (mid-30s Celsius), and with April being the hottest month. Normally, this period sees sporadic rain.
In recent years, however, the rainy season has begun in April and has lasted, on and off, until late November, or even December. The average temperature is 84°F (29°C) with 90% humidity. While the rainy season brings heavy downpours, it is rare to see an all-day episode. From June, daily showers will usually come in the late afternoon or evening for 3 to 4 hours, often bringing floods and forcing traffic to a standstill. Trekking in the north is not recommended during this time. In Bangkok, expect smog from April to August.
The cool season, from November to February, has temperatures from the high 70s°F to low 80s°F (26°C-29°C), with infrequent showers. Daily temperatures can drop as low as 60°F (16°C) in Chiang Mai and 41°F (5°C) in the hills; 1 or 2 nights may even see frost.
The Southern Thai Peninsula has intermittent showers year-round and daily downpours during the rainy season (temperatures average in the low 80s Fahrenheit/30s Celsius). If you're traveling to Phuket or Ko Samui, it would be helpful to note that the two islands alternate peak seasons. Optimal weather on Phuket occurs between November and April, when the island welcomes the highest numbers of travelers. Conversely, Ko Samui's great weather lasts from about February to October. Refer to each destination's section for more information about peak seasons and changing weather patterns.
Many holidays are based on the Thai lunar calendar, falling on the full moon of each month; check with the Tourism Authority of Thailand (TAT; www.tat.or.th) for the current year's schedule.
On National and Buddhist holidays and on polling days, government offices, banks, small shops, and offices -- as well as some restaurants and bars -- usually close. By law, bars cannot serve alcohol on HM Queen Sirikit's birthday in August, nor on HM King Bhumibol's birthday in December. Note: In most cases there will be little advance warning given to shop, restaurant, or bar customers. Public transport still runs on holidays, though.
January to March -- Thailand celebrates New Year's Day the same as the rest of the world. In late February or early March (depending on the lunar cycle) is Makha Bucha Day, when temples celebrate Buddha preaching to his disciples.
April -- Chakri Memorial Day (Apr 6) commemorates the founding of the current Chakri dynasty.
Songkran is the New Year according to the Thai calendar, and it's an event that begins officially on April 13 and lasts 3 days, though water splashing begins about a week before in the countryside. After honoring local monks and family elders, folks hit the streets for massive water fights. Be warned -- foreigners are the Thais' favorite target and such areas as Khao San Road become messy war zones where everyone gets soaked (police included) and then covered in flour or colored powder. Truck-mounted power hoses can cause damage, and cellphones, cameras, and valuables should be kept in Ziploc bags. Wear your oldest clothes -- anyone expecting to stay dry will be sorely disappointed!
May -- National Labor Day falls on the 1st, while Coronation Day, celebrating the coronation of HM King Bhumibol in 1946, is on the 5th. Visakha Bucha Day, marking the birth, enlightenment, and death of the Buddha, falls around mid- to late May, depending on the lunar calendar.
July -- Thais celebrate the Buddhist Lent immediately following Asarnha Bucha Day in mid-July (depending on the lunar calendar), signaling the beginning of the rains' retreat and the 3-month period of meditation for all Buddhist monks -- this was the day that the Buddha delivered his first sermon to his first five disciples.
August -- August 12 honors the birthday of HM Queen Sirikit and is also Mother's Day.
October -- On October 23, Chulalongkorn Day, the country's favorite king, Rama V, is remembered.
November -- Loy Krathong, in early November, is Thailand's most romantic festival, although it's not usually a public holiday. After dark, handmade banana-leaf vessels are launched down rivers, and lanterns are hoisted into the sky in order to symbolize the release of sins. The most spectacular celebrations are in Sukhothai and Chiang Mai.
December -- December 5 marks HM King Bhumibol's birthday and is also Father's Day. December 10 is Constitution Day and recognizes Thailand's first constitution in 1932.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.