Thailand has a predominantly tropical wet and dry climate (Köppen climate classification Aw) in the north and tropical monsoon type of climate (Köppen Am) in the south. A few sections in the western and southern regions harbor tropical rainforests (Köppen Af). The extreme north has few regions with a temperate climate (Köppen Cwa, Cwb), with warm to hot summers and dry winters. Thailand lies in Southeast Asia, entirely between the equator and the Tropic of Cancer. Laos and Cambodia are in the east, Malaysia and the Gulf of Thailand in the south, Myanmar and the Andaman Sea in the west, and Laos and Myanmar in the north. The tropical location and monsoon rains, along with proximity to large water bodies, chiefly influence the climate.
Thailand has several geographical regions with varied topography. Northern Thailand is mountainous and a source of several important rivers. The northeast region is mainly a plateau that sits on a high-level plain. Doi Inthanon in Chiang Mai is the highest mountain in the north, at 2595 meters. The Yom, Nan, Ping, and Wang rivers unite to form the Chao Phraya River in the broad, low-level plain of the central region. The eastern portion mostly consists of plains and valleys and kisses the Gulf of Thailand in its south. Southern Thailand is a peninsula between the Andaman Sea in the west and the South China Sea in the east. The long ridge of western mountains extends from the north and central regions, all the way to the south. The Phuket and Nakhon Si Thammarat ridges separate the southern portion into western and eastern coasts. The Mekong and Chao Phraya are famous rivers. The Bang Pakong, Mae Klong, Tapi, and Chao Phraya rivers drain into the Gulf of Thailand, whose clear shallow waters along the southern region are famous for tourism. The islands along the Andaman Sea coast, such as Phuket, Phang Nga, Trang, and Krabi are tourist hotspots.
Thailand has three distinct seasons, with a mainly tropical climate. Summers run from March to May and are generally hot and dry. The average high temperatures peak in April and register in the 32.2°C (90°F) to 36.1°C (97°F) in much of the country. The northern inland plains are hot throughout the year except for a brief period in the winter. Peninsular Thailand, overlooking the Gulf of Thailand in the east, has moderate summers than the rest of the country. The rainy season begins by the last week of May and lasts until October. The rainfall is heavy, and the conditions are humid and hot. Mountains receive abundant rainfall above altitudes of 1000 meters. November brings the pleasant winter season in Thailand that lasts up to late February. Bangkok and surrounding areas have average daily high temperatures in the 31.1°C (88°F) to 32.2°C (90°F) range, even in the winter. The northwest mountain ranges near Myanmar and Laos have comfortable temperatures throughout the year.
The southwest monsoon prevails over Thailand to bring abundant annual rainfall in the range of 1092.2mm (43") to 1701.8mm (67"). August to September is the usually wettest period of the year in much of the country. The northeast monsoon brings heavy rainfall to the east coast of Southern Thailand, where November is the wettest month. The Trat province in the east and Ranong province in the west receive more than 4572mm (180") of rainfall in the year. The annual sunshine ranges from 2100 hours on the rainy west coast to 2700 hours in Bangkok and Pattaya. The relative humidity is highest during the rainy season and the lowest during the summer. The cloud cover is usually less between November and March. El Nino and La Nina factors that arise from the Pacific Ocean affect the monsoon rains in Thailand.
The highest temperature on record for Thailand is 44.5°C (112.1°F), set on April 27, 1960, in Uttaradit. The coldest temperature is -1.4°C (29.5°F), set on January 2, 1974, in Sakon Nakhon.
The best time to visit Thailand
The best time to visit Thailand is post-monsoon, during the pleasant months from November to February. The skies are clear, and the temperatures are in the most comfortable range of the year. Cold and dry air masses from China keep northern Thailand in their grip. Bangkok and the western coast, including Phuket, Krabi, and the Phi Phi Islands have excellent weather until early summer. The east coast along the Gulf of Thailand is a great vacation destination until mid-summer. The greenery soothes the eyes after the rainy season. Budget travelers find the final phase of the wet season cheap on the wallet and the weather to be moderate.
The worst time to visit Thailand
The worst time to visit Thailand is during April and May when the summer is at its peak. Temperatures frequently cross 40°C (104°F) in the hinterland, and the conditions are dry. June provides relief in the form of the southwest monsoon, but the heat and humidity are often high. The heat index in Bangkok and many other cities is high due to the urban heat island effect. July and August bring heavy rainfall along the western coast of Thailand. The rain, heat, and humidity are occasionally unbearable for visitors from the temperate weather zones. Additionally, tropical cyclones are active in the rainy season, and it is prudent to skip the wet period for a vacation.
Thailand is prone to thunderstorms, floods, and tropical cyclones during the rainy season. May has the highest frequency of thunderstorms in the country. Tropical cyclones usually arrive from the Pacific Ocean or the South China Sea to Thailand's shores. The southern part has a high incidence of typhoons with wind speeds above 120.7km/h (75mph). May to November is the season of tropical storms, with an annual average of three to four cyclones. Typhoon Linda hit the Prachuap Khiri Khan province in November 1997 with devastating effect. Heavy rainfall causes seasonal floods in Thailand.
Weather in January
January is beautiful and sunny, even though it is usually the coldest month of the year in Thailand. The northern plains and valleys have a rosy cold, with average low temperatures in the mild 11.1°C (52°F) to 15.6°C (60.1°F) range. The mountains above altitudes of 1000 meters are the only places where the conditions are cold enough for wearing layered clothing. Much of the country sees lovely sunshine that lasts 7 to 8 hours. Follow the strict dress code during a visit to the Grand Palace in the heart of Bangkok, the capital, where temperatures are comfortable in January compared to the summer. Enjoy the hospitality and relax at luxurious spas, with warm oils for a massage that rejuvenates the body in the cold season. The New Year is a festive time with plenty of tourist footfalls. Expect the southeastern beaches to be rainy in the winter due to the effect of the northeast monsoon. The dry atmosphere, comfortable temperatures, and low humidity make January a pleasant time to explore Thailand.
Weather in February
February is moderately cold and dry in Thailand, with mostly clear skies amid beautiful sunshine. The days have 9 hours of lovely sunshine in the northern plains, but the evenings are cold after sunset. The average temperatures in the Chiang Mai region are in the 16.1°C (61°F) to 32.2°C (90°F) range, with negligible rain. Check the blooming forecast in the north. Wild Himalayan cherry blossoms turn the landscape into a combination of pink and green in the mountains of Doi Inthanon and many parks in Chiang Mai. Mountain adventurers enjoy hiking in the winter months in a blanket of mist and frost feathers. The beaches of Krabi and Phang Nga have fewer crowds and offer great sunset views in the mild waters in the winter. Expect temperatures to rise gradually with the end of the winter season insight. February has charming weather in much of Thailand.
Weather in March
March is dry and hot at the beginning of the summer in Thailand. Temperatures rise steadily every day, and the sunshine lasts for more than 9 hours. Phuket is an excellent destination in early summer, with average temperatures in the 23.9°C (75°F) to 32.8°C (91°F) range. The southwestern coast receives a few showers, but the precipitation is light at most. The waterways are busy with cruises and ferries full of tourists. Sea breezes mostly occur in the evenings, which is a pleasant time on the beaches. The parks and reserves are full of visitors who try to find solace in the warm weather. Feed elephants and bathe them with cool waters to escape from the rising heat. The Khlong Lat Mayom Floating Market near Bangkok offers delicious food and fun activities under the clear skies of March. Lightweight clothing such as sweatshirts, along with comfortable shoes is suitable during the day. Thailand begins to heat considerably by the second half of March.
Weather in April
April is typically the hottest month of the year in Thailand. The average high temperatures are in the range of 31.1°C (88°F) to 33.3°C (91.9°F), with 9 to 10 hours of bright sunshine. The northern interior lands are hotter than the peninsular south due to the proximity of large water bodies in the south. The beaches and islands beckon travelers with their moderate temperatures, clear blue skies, and shallow waters. Phi Phi Island and Koh Lanta are fantastic destinations with plenty of water activities to beat the heat. The heat is oppressive in the north unless people opt for a vacation in the mountains. Bring sweaters for evenings on mountain tops above 2000 meters if the plan is to camp in the open. Pre-monsoon showers mostly occur on the southwestern coast for 4 to 5 days in April. Air-conditioners run in indoor places everywhere, from offices to hotels and restaurants to malls. Expect long and warm evenings that are fun to spend outdoors in April in Thailand.
Weather in May
May is hot and dry in Thailand, with mostly clear skies and sticky heat. The southern region is especially humid with its closeness to the sea. However, temperatures are moderate in the south and never reach highs like 40°C (104°F) in the north. Seasonal fires also burn in northern Thailand and cause terrible smoke and haze. Storms batter the southwestern coast overlooking the Andaman Sea. Koh Lanta begins to bear the brunt towards May-end with storms, and slowdown in tourist footfalls. Temperatures are between 25°C (77°F) to 32.8°C (91°F) in the south, with 76.2mm (3") to 101.6mm (4") of pre-monsoon rainfall. Bangkok is uncomfortably hot with the urban heat island effect in full force in the city. Lightweight clothing, such as sweatshirts, t-shirts, and shorts, are desirable. Expect humidity in addition to the heat. There is a chance to grab discounts in the hot season, but many tourists who escape from the southern hemisphere winter land on the shores of Thailand in May.
Weather in June
June is the beginning of the rainy season in Thailand, with cloudy skies and high humidity levels. The southwest monsoon strikes the country with its full intensity and is particularly harsh on the southern coasts. The average temperatures in Pattaya hover in the 27.2°C (81°F) to 32.2°C (90°F), with 127mm (5") of precipitation. Phuket is cloudy with less than 6 hours of sunshine. Thunderstorms frequently occur in the northern mountains, but trekkers do not find the weather dangerous for hiking. The heat and humidity are unbearable in June at times, and the best way to beat the heat is to spend time on the beaches such as Koh Phi Phi. The Namtok Phlio National Park in Chanthaburi is another cool place to escape from the heat and heavy rainfall. The start of the monsoon season offers moderate weather conditions with the rainfall yet to peak. Budget travelers find cheap flights and accommodations during June, which is the period of relatively fewer tourist footfalls in Thailand.
Weather in July
July brings heavy rainfall and high humidity levels in Thailand. Winds push the heavy moisture-laden clouds from the Indian Ocean towards the sub-continent. The days mostly receive at least 6 hours of sunshine, particularly in the northern region. The average high temperatures are below 31.1°C (88°F) in much of Thailand, but the humidity raises the heat quotient. Evenings are uncomfortably humid when the skies are cloudy due to lack of breezes. Air-conditioners make the nights comfortable in the luxurious hotels. The seawater temperatures in Koh Samui average below 28.9°C (84°F) and attract the tourist population. Expect rain any time and wear a rain jacket or carry an umbrella during outdoor visits. Keep electronic gadgets dry and out of reach of the wet weather. Keep an eye on the weather forecast for cyclones from the Andaman Sea and typhoons from the South China Sea. The islands in the Gulf of Thailand are a safe bet for a vacation as they remain out of reach of tropical storms in July in Thailand.
Weather in August
August has regularly cloudy skies in Thailand that bring heavy rainfall to the various parts of the country. The eastern shores receive comparatively less rainfall than the western shores. Chiang Mai and Chiang Rai in the north receive up to 4 hours of daily sunshine and less than 228.6mm (9") of rainfall. Bangkok and Pattaya, with 152.4mm (6") to 203.2mm (8") of rain, are prudent choices in the rainy season than the south. Streets flood in water during heavy rains in most places, including Bangkok. Temples, historic sites, and museums have plenty of space for visitors during the wet season. The southwest is particularly out of bounds, with torrential rainfall along the coast and the cyclone season in full swing. If it is mandatory to visit the south at least stay in the interior and avoid the islands Light summer clothing is best as daily high temperatures usually reach above 32.2°C (90°F), and humidity levels touch 90%. Umbrellas and raincoats are mandatory for protection from the rain. Avoid a vacation in Thailand in August as far as possible.
Weather in September
September is the wettest month of the year in Thailand except for the southeastern region. Many places receive rainfall above 304.8mm (12") to 381mm (15") that floods the rivers, lakes, and streams. The average temperatures are in the range of 21.1°C (70°F) to 32.2°C (90°F), but the cloudy skies raise the heat index. A burst of rain cools down the atmosphere for a few hours before humidity builds up again. The daily sunshine of fewer than 5 hours offers little opportunity for outdoor activities. Scrumptious Thai food comes to the rescue of visitors who spend time indoors in malls, shopping centers, museums, and the like. Ayutthaya has plenty of historical relics of interest to history buffs during the few hours of sunshine in September. For those who dare to spend time outdoors, the peak monsoon is the time of roaring waterfalls down the mountain slopes, misty mornings, and lush greenery everywhere. Picturesque streams and waterfalls unleash their natural beauty only in the rainy season. Do not forget to wear raincoats and rubber-soled shoes during outdoor explorations in September in Thailand.
Weather in October
October sees a gradual retreat of the southwest monsoon from Thailand. The average temperatures are in the zone of 23.9°C (75°F) to 32.2°C (90°F) in much of Thailand. Rainfall reduces to register below 254mm (10"), even in the wettest places of the southwest coast. However, it is prudent to avoid the coasts and beaches and head towards the central and northern regions. The mountains are green, with wildflowers blossoming on their slopes. Trekkers take advantage of the decrease in precipitation to climb the peaks and enjoy the scenery on the valley floors from vintage points. Tropical storms occasionally rage along the coast and make a mess on the white, sandy beaches. October heat is oppressive at times, and it is prudent to avoid the mid-day sun with dangerous levels of ultra-violet radiation. Expect frequent cycles of rain and shine and carry an umbrella for protection. The tourist footfalls begin to increase in Thailand by the end of October and the rainy season.
Weather in November
November is the wettest month along the southeast coast of Thailand, but dry in the rest of the country. The retreating monsoon brings heavy rainfall up to 464.8mm (18.3") in Ko Samui in the Gulf of Island, and it is a prudent idea to avoid the region. Pattani and Songkhla are generally cloudy and rainy, with average temperatures in the zone of 23.9°C (75°F) to 30°C (86°F). The weather is comfortable in much of Thailand, with the harvest season in full swing. Lush green paddy fields in the small villages along the beautiful countryside are a lovely sight for tourists exploring the roadways. Pattaya receives less rainfall in November, and the weather is perfect for exploring the many cultural and historical places in the city. The days have at least 6 hours of beautiful sunshine, and the nights are cozy. Sweaters are not necessary for the peninsular part of the country. November brings a breath of freshness and new hope to Thailand.
Weather in December
December is the beginning of the mild winter season in Thailand, with plenty of sunshine. The conditions are pleasant, with moderate daily temperatures and mild to cool nights. The clear skies and sunny days are perfect for exploring the country and experiencing the famous Thai hospitality. The absence of rain in much of the country is the reason for increased tourist footfalls. Visitors who prefer cold temperatures have the option to explore the mountain resorts that are past the peak tourist season. Temperatures in Chiang Mai in the north drop up to 4.4°C (39.9°F) during the night, yet the daily sunshine lasts for 8 hours. The northeast monsoon is active along the southeast coast overlooking the Gulf of Thailand. It is better to postpone a trip to the island of Ko Samui in the Gulf, with the 190.5mm (7.5") of December rainfall. Phuket is a lovely destination in the southwest, with little rain and average temperatures in the 23.9°C (75°F) to 31.1°C (88°F) range. December is one of the best times to visit Thailand.