Do you need to know, when is the best time to go to Thailand? Then you should take a look here, what weather you can expect there during the year.
The climate of Thailand is tropical. There is rainy, but warm southwest monsoon from May to September, and dry, but cooler northeast monsoon from November to February. It is usually colder in mountains in the north, and you can expect warmer and wetter weather in the south.
When speaking about the usual weather in this state, the information is relevant for example for these popular places: Amnat Charoen, Amphawa, Ang Thong, Ang Thong National Marine Park, Ao Nang, Ao Phang Nga National Park, Aranyaprathet, Ayutthaya, Baan Ao Leuk, Ban Krut, Ban Phe, Ban Rak Thai, Bang Pa In, Bang Rak, Bang Saen, Bang Thao, Bangkok, Betong, Bophut, Buriram, Cape Panwa, Central Gulf Coast, Central Isaan, Central Thailand, Cha am, Chachoengsao, Chai Nat, Chaiya, Chaiyaphum, Chalong Bay, Chanthaburi, Chao Phraya Basin, Chaweng, Chiang Dao, Chiang Khan, Chiang Khong, Chiang Mai, Chiang Mai Province, Chiang Rai, Chiang Rai Province, Chiang Saen, Choeng Mon, Chonburi, Chong Mek, Chumphon, Damnoen Saduak, Dan Chang, Diving in Thailand, Doi Ang Khang, Doi Inthanon National Park, Doi Tung, Eastern Gulf Coast, Eastern Thailand, Fang, Golden Triangle, Had Yao, Hang Chat, Hat Lek, Hat Yai, Hua Hin, Inner Eastern Thailand, Isaan, Jom Jang, Jomtien, Kalasin, Kamala, Kamphaeng Phet, Kanchanaburi, Kantharalak, Karon, Kata, Khanom, Khao Lak, Khao Lampi Hat Thai Mueang National Park, Khao Phra Thaeo Non Hunting Area, Khao Sok National Park, Khao Yai National Park, Khok Kloi, Khon Kaen, Khun Yuam, Ko Bon, Ko Bulon Leh, Ko Chang, Ko Hae, Ko Jum, Ko Kret, Ko Kut, Ko Lan, Ko Lanta, Ko Lipe, Ko Lon, Ko Mai Thon, Ko Mak, Ko Maphrao, Ko Muk, Ko Nang Yuan, Ko Ngai, Ko Pha ngan, Ko Phayam, Ko Phi Phi, Ko Phra Thong, Ko Poda, Ko Por, Ko Racha, Ko Sak, Ko Samet, Ko Samui, Ko Siboya, Ko Sichang, Ko Sire, Ko Tao, Ko Tarutao, Ko Yao, Krabi Province, Krabi Town, Laem Chabang, Laem Ngop, Laem Sing, Laem Yai, Lamai, Lampang, Lamphun, Lang Suan, Loei, Lom Sak, Lopburi, Lower Northern Thailand, Mae Hong Son, Mae Hong Son Province, Mae La Noi, Mae Nam, Mae Sai, Mae Salong, Mae Sariang, Mae Sot, Maha Sarakham, Mai Khao, Mu Ko Surin National Park, Mukdahan, Nai Han, Nai Thon and Nai Yang, Nakhon Nayok, Nakhon Pathom, Nakhon Phanom, Nakhon Ratchasima, Nakhon Sawan, Nakhon Si Thammarat, Nan, Nang Rong, Narathiwat, Nathon, Nong Bua Lamphu, Nong Khai, Nonthaburi, Northern Andaman Coast, Northern Gulf Coast, Northern Isaan, Northern River Valleys, Northern Thailand, Padang Besar, Pai, Pak Bara, Pak Chong, Pangmapha, Pathum Thani, Patong, Pattani, Pattaya, Phang Nga, Phatthalung, Phayao, Phetchabun, Phetchaburi, Phichit, Phimai, Phitsanulok, Phon Phisai, Phrae, Phu Chi Fa, Phu Kradueng National Park, Phuket, Phuket Town, Prachinburi, Prachuap Khiri Khan, Rai Leh, Ramkhamhaeng National Park, Rangsit, Ranong, Ratchaburi, Rawai, Rayong, Roi Et, Sa Kaeo, Sadao, Sakon Nakhon, Samoeng, Samui South Coast, Samut Prakan, Samut Sakhon, Samut Songkhram, Sangkhla Buri, Saraburi, Sathing Phra, Sattahip, Satun, Si Racha, Si Satchanalai, Similan Islands, Sing Buri, Sisaket, Songkhla, Southern Andaman Coast, Southern Gulf Coast, Southern Isaan, Southern Thailand, Sukhothai, Sungai Kolok, Suphanburi, Surat Thani, Surin, Tak, Tak Bai, Takua Pa, Thaton, Thepha, Three Pagodas Pass, Thungyai Huai Kha Khaeng Wildlife Sanctuaries, Ton Sai, Trang, Trat, Trat Province, Ubon Ratchathani, Udon Thani, Umphang, Uthai Thani, Uttaradit, West of Bangkok, Ya Nui, Yala, Yasothon.
Let's look now what weather you can expect in the area around the capital and in many other cities. The warmest month here is April, the average maximum temperature is 35.2 ℃ (95.36 ℉). The average minimum temperature in this month is 26.1 ℃ (78.98 ℉). The coldest month here is December, the average maximum temperature is 31 ℃ (87.8 ℉). The average minimum temperature in this month is 20.9 ℃ (69.62 ℉). The most rainy month here is September, the average number of rainy days is 18.3. The least rainy month here is January, the average number of rainy days is 1. 
When travelling to some places in Thailand, always consider the altitude of the the place as well. The highest point here is Doi Inthanon (2565 m) and the lowest point is Gulf of Thailand (0 m). So there are quite big differences in altitudes in this country, so you can expect the weather to be different in different altitudes as well. Keep in mind, that the temperature usually decreases by 1.2 - 1.9 ℃ (2.2 - 3.5 ℉) per 200 m (656 ft), depending on the other conditions. (And we should add, that in the very special condition named thermal inversion even the temperature may be higher in higher altitudes.)
Typical (usual) weather in Thailand in January is this: The average highest temperature in Thailand in January is 32 ℃ (89.6 ℉). The average lowest temperature is 21.2 ℃ (70.16 ℉). At the beginning of January you can expect lower temperatures, the average highest temperature is around 31.5 ℃ (88.7 ℉). At the end of January you can expect higher temperatures, the average highest temperature is around 32.25 ℃ (90.05 ℉). The average number of rainy days in January is 1. The average rainfall is 9.2 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:19 (hours and minutes), in the middle of the month 11:24 and at the end of the month 11:31.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Thailand in February is this: The average highest temperature in Thailand in February is 32.5 ℃ (90.5 ℉). The average lowest temperature is 24 ℃ (75.2 ℉). At the beginning of February you can expect lower temperatures, the average highest temperature is around 32.25 ℃ (90.05 ℉). At the end of February you can expect higher temperatures, the average highest temperature is around 33.25 ℃ (91.85 ℉). The average number of rainy days in February is 2. The average rainfall is 29.9 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:31 (hours and minutes), in the middle of the month 11:41 and at the end of the month 11:52.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Thailand in March is this: The average highest temperature in Thailand in March is 34 ℃ (93.2 ℉). The average lowest temperature is 25.2 ℃ (77.36 ℉). At the beginning of March you can expect lower temperatures, the average highest temperature is around 33.25 ℃ (91.85 ℉). At the end of March you can expect higher temperatures, the average highest temperature is around 34.6 ℃ (94.28 ℉). The average number of rainy days in March is 2. The average rainfall is 28.3 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:52 (hours and minutes), in the middle of the month 12:03 and at the end of the month 12:15.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Thailand in April is this: The average highest temperature in Thailand in April is 35.2 ℃ (95.36 ℉). The average lowest temperature is 26.1 ℃ (78.98 ℉). At the beginning of April you can expect lower temperatures, the average highest temperature is around 34.6 ℃ (94.28 ℉). At the end of April you can expect lower temperatures, the average highest temperature is around 34.55 ℃ (94.19 ℉). The average number of rainy days in April is 4.1. The average rainfall is 64.6 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:15 (hours and minutes), in the middle of the month 12:26 and at the end of the month 12:36.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Thailand in May is this: The average highest temperature in Thailand in May is 33.9 ℃ (93.02 ℉). The average lowest temperature is 26.1 ℃ (78.98 ℉). At the beginning of May you can expect higher temperatures, the average highest temperature is around 34.55 ℃ (94.19 ℉). At the end of May you can expect lower temperatures, the average highest temperature is around 33.85 ℃ (92.93 ℉). The average number of rainy days in May is 12.7. The average rainfall is 222.9 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:36 (hours and minutes), in the middle of the month 12:45 and at the end of the month 12:52.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Thailand in June is this: The average highest temperature in Thailand in June is 33.8 ℃ (92.84 ℉). The average lowest temperature is 25.8 ℃ (78.44 ℉). At the beginning of June you can expect higher temperatures, the average highest temperature is around 33.85 ℃ (92.93 ℉). At the end of June you can expect lower temperatures, the average highest temperature is around 33 ℃ (91.4 ℉). The average number of rainy days in June is 12.3. The average rainfall is 146.7 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:52 (hours and minutes), in the middle of the month 12:55 and at the end of the month 12:55.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Thailand in July is this: The average highest temperature in Thailand in July is 32.2 ℃ (89.96 ℉). The average lowest temperature is 25.8 ℃ (78.44 ℉). At the beginning of July you can expect higher temperatures, the average highest temperature is around 33 ℃ (91.4 ℉). At the end of July you can expect higher temperatures, the average highest temperature is around 32.85 ℃ (91.13 ℉). The average number of rainy days in July is 13.2. The average rainfall is 153.1 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:55 (hours and minutes), in the middle of the month 12:51 and at the end of the month 12:45.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Thailand in August is this: The average highest temperature in Thailand in August is 33.5 ℃ (92.3 ℉). The average lowest temperature is 24.5 ℃ (76.1 ℉). At the beginning of August you can expect lower temperatures, the average highest temperature is around 32.85 ℃ (91.13 ℉). At the end of August you can expect lower temperatures, the average highest temperature is around 32.7 ℃ (90.86 ℉). The average number of rainy days in August is 15.2. The average rainfall is 199.8 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:45 (hours and minutes), in the middle of the month 12:36 and at the end of the month 12:26.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Thailand in September is this: The average highest temperature in Thailand in September is 31.9 ℃ (89.42 ℉). The average lowest temperature is 24.8 ℃ (76.64 ℉). At the beginning of September you can expect higher temperatures, the average highest temperature is around 32.7 ℃ (90.86 ℉). At the end of September you can expect lower temperatures, the average highest temperature is around 31.85 ℃ (89.33 ℉). The average number of rainy days in September is 18.3. The average rainfall is 350.9 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:26 (hours and minutes), in the middle of the month 12:14 and at the end of the month 12:03.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Thailand in October is this: The average highest temperature in Thailand in October is 31.8 ℃ (89.24 ℉). The average lowest temperature is 24.8 ℃ (76.64 ℉). At the beginning of October you can expect higher temperatures, the average highest temperature is around 31.85 ℃ (89.33 ℉). At the end of October you can expect higher temperatures, the average highest temperature is around 32.15 ℃ (89.87 ℉). The average number of rainy days in October is 13.9. The average rainfall is 246.7 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:03 (hours and minutes), in the middle of the month 11:52 and at the end of the month 11:41.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Thailand in November is this: The average highest temperature in Thailand in November is 32.5 ℃ (90.5 ℉). The average lowest temperature is 23.4 ℃ (74.12 ℉). At the beginning of November you can expect lower temperatures, the average highest temperature is around 32.15 ℃ (89.87 ℉). At the end of November you can expect lower temperatures, the average highest temperature is around 31.75 ℃ (89.15 ℉). The average number of rainy days in November is 5.1. The average rainfall is 46.8 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:41 (hours and minutes), in the middle of the month 11:31 and at the end of the month 11:24.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Thailand in December is this: The average highest temperature in Thailand in December is 31 ℃ (87.8 ℉). The average lowest temperature is 20.9 ℃ (69.62 ℉). At the beginning of December you can expect higher temperatures, the average highest temperature is around 31.75 ℃ (89.15 ℉). At the end of December you can expect higher temperatures, the average highest temperature is around 31.5 ℃ (88.7 ℉). The average number of rainy days in December is 1. The average rainfall is 10.2 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:24 (hours and minutes), in the middle of the month 11:19 and at the end of the month 11:19.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.| Bangkok | temperature: 25.8 ℃ (78.44 ℉) | highest temperature: 31 ℃ (87.8 ℉) | lowest temperature: 20.9 ℃ (69.62 ℉) | rainfall: 10.2mm | rainy days: 1 |
| Mae Hong Son | temperature: - | highest temperature: 28.6 ℃ (83.48 ℉) | lowest temperature: 15.6 ℃ (60.08 ℉) | rainfall: 14.5mm | rainy days: 1.7 |
| Chiang Rai | temperature: - | highest temperature: 26.6 ℃ (79.88 ℉) | lowest temperature: 12.9 ℃ (55.22 ℉) | rainfall: 17.2mm | rainy days: 2 |
| Chiang Mai | temperature: - | highest temperature: 28.9 ℃ (84.02 ℉) | lowest temperature: 15.2 ℃ (59.36 ℉) | rainfall: 18.2mm | rainy days: 1.6 |
| Tak | temperature: - | highest temperature: 30.9 ℃ (87.62 ℉) | lowest temperature: 16.8 ℃ (62.24 ℉) | rainfall: 4.9mm | rainy days: 0.8 |
| Phetchabun | temperature: - | highest temperature: 30.9 ℃ (87.62 ℉) | lowest temperature: 17.3 ℃ (63.14 ℉) | rainfall: 6.6mm | rainy days: 0.7 |
| Sukhothai | temperature: - | highest temperature: 32.2 ℃ (89.96 ℉) | lowest temperature: 19.8 ℃ (67.64 ℉) | rainfall: 2.1mm | rainy days: 2 |
| Khon Kaen | temperature: - | highest temperature: 29.6 ℃ (85.28 ℉) | lowest temperature: 17.2 ℃ (62.96 ℉) | rainfall: 4.2mm | rainy days: 0.7 |
| Ubon Ratchathani | temperature: - | highest temperature: 30.5 ℃ (86.9 ℉) | lowest temperature: 18 ℃ (64.4 ℉) | rainfall: 1.2mm | rainy days: 0.6 |
| Nakhon Ratchasima | temperature: - | highest temperature: 29 ℃ (84.2 ℉) | lowest temperature: 17.6 ℃ (63.68 ℉) | rainfall: 2.9mm | rainy days: 0.7 |
| Kanchanaburi | temperature: - | highest temperature: 31.3 ℃ (88.34 ℉) | lowest temperature: 18.9 ℃ (66.02 ℉) | rainfall: 6mm | rainy days: 1 |
| Pattaya | temperature: - | highest temperature: 29.6 ℃ (85.28 ℉) | lowest temperature: 22.5 ℃ (72.5 ℉) | rainfall: 6.4mm | rainy days: 1.1 |
| Hua Hin | temperature: - | highest temperature: 29.6 ℃ (85.28 ℉) | lowest temperature: 22.4 ℃ (72.32 ℉) | rainfall: 11.3mm | rainy days: 1.4 |
| Ko Samui | temperature: - | highest temperature: 29.8 ℃ (85.64 ℉) | lowest temperature: 24.5 ℃ (76.1 ℉) | rainfall: 207.2mm | rainy days: 14 |
| Songkhla | temperature: - | highest temperature: 28.9 ℃ (84.02 ℉) | lowest temperature: 24.9 ℃ (76.82 ℉) | rainfall: 413.7mm | rainy days: 20.1 |
| Phuket | temperature: - | highest temperature: 32.1 ℃ (89.78 ℉) | lowest temperature: 24.1 ℃ (75.38 ℉) | rainfall: 62.5mm | rainy days: 8.3 |