How we know: Sources are listed at the end. Weather figures are official Thai Meteorological Department climate normals; route and entry facts come from the cited airport, news and travel-guide pages. Wildly does not publish fare averages in prose; live prices are on the linked route pages.
Thailand's "best time to visit" is the cool season from November to February, and for Bangkok, Chiang Mai and the Andaman coast that advice is correct. But the country has two coastlines on two monsoon schedules, so a beach trip in the "wrong" months is usually a matter of picking the other coast rather than cancelling. Below is the month-by-month picture for Bangkok, how Phuket and the Gulf islands differ, the holiday weeks that fill every flight, and what US travellers need to know about getting there and getting in.
Bangkok weather by month
Thai Meteorological Department 1991–2020 normals for Bangkok Metropolis:
| Month | Avg high | Avg low | Rainfall | Rainy days | |---|---|---|---|---| | January | 91°F (33°C) | 74°F (23°C) | 0.9 in | 2 | | February | 93°F (34°C) | 77°F (25°C) | 0.8 in | 2 | | March | 94°F (35°C) | 79°F (26°C) | 2.0 in | 3 | | April | 96°F (36°C) | 81°F (27°C) | 3.7 in | 5 | | May | 95°F (35°C) | 80°F (27°C) | 8.5 in | 12 | | June | 94°F (34°C) | 79°F (26°C) | 7.8 in | 13 | | July | 92°F (34°C) | 79°F (26°C) | 7.5 in | 14 | | August | 92°F (33°C) | 79°F (26°C) | 8.9 in | 16 | | September | 92°F (33°C) | 78°F (25°C) | 13.2 in | 18 | | October | 92°F (33°C) | 77°F (25°C) | 11.4 in | 14 | | November | 92°F (33°C) | 76°F (25°C) | 1.8 in | 4 | | December | 90°F (32°C) | 74°F (23°C) | 0.5 in | 1 |
Bangkok is hot every month; the variables are humidity and rain. December–February see under an inch a month. April is the hottest month, with an average high of 96°F, and Wikivoyage notes heat indices well above that. The wet season builds from May and peaks in September, the wettest month at 13 inches on 18 rainy days, before switching off abruptly in November.
Three seasons, two coasts
Wikivoyage divides the Thai year into cool (November–February, little rain, the most popular time to visit), hot (March–April, with temperatures as high as 104°F and April the hottest month) and rainy (May–October, though it "only really gets underway" in September, and when it rains it pours).
That calendar applies to Bangkok, the north and the Andaman coast: Phuket, Krabi, Ko Phi Phi and Ko Lanta. Phuket's normals show under an inch of rain in February and 2 inches in January, rising to 9–10 inches a month from May to July and 12–14 inches in August, September and October, with rough seas that close some island crossings.
The Gulf coast runs on a different clock. Wikivoyage notes that the central Gulf coast, including Ko Samui, Ko Pha Ngan and Ko Tao, has the rains reversed: its dry peak season is May to October and its rainy off-season is November to February, when the northeast monsoon pushes moisture across the Gulf. In practice the Gulf islands are wettest from October through December, so a June or July beach trip should point at Samui, while a December trip should point at Phuket.
Season by season
November–February (cool season, peak). Dry across Bangkok, the north and the Andaman coast, and by Thai standards cool, with Wikivoyage noting temperatures as low as 41°F in the northern mountains. It is also when demand peaks: Wikivoyage warns that around Christmas–New Year and Chinese New Year a few weeks later, flights and accommodation can be expensive and difficult to find.
March–April (hot season). Bangkok averages 94–96°F and temple sightseeing is hard work after mid-morning. The compensation is Songkran, the Thai New Year, officially 13–15 April, which Wikivoyage calls "the world's largest water fight." Domestic travel surges for the holiday and road accidents spike, so avoid long overland journeys that week.
May–October (rainy season). Rain in Bangkok typically arrives as heavy afternoon or evening downpours rather than all-day drizzle, and flooding is not uncommon in September and October. Hotels and flights are quieter and the countryside is green. This is the Gulf coast's dry season: Ko Samui, Ko Pha Ngan and Ko Tao are at their best. The Andaman coast is wet and some boats stop running.
Getting there from the US
Suvarnabhumi (BKK) is Bangkok's main international airport and the country's long-haul gateway. Per its destinations table, United is the only US carrier listed, with service from Los Angeles and Hong Kong; Airways reports that the DOT approved United's Los Angeles–Bangkok service in 2025 as an extension of its Los Angeles–Hong Kong flights under fifth-freedom rights, making United the only US airline serving Thailand. Every other routing connects through an Asian or Gulf hub: Tokyo (ANA, JAL), Seoul (Korean Air, Asiana), Taipei (EVA, China Airlines, Starlux), Hong Kong (Cathay Pacific), Singapore, Doha, Dubai or Istanbul, all of which appear in the Suvarnabhumi table.
Phuket (HKT), Chiang Mai (CNX) and Ko Samui (USM) have no US service; connect in Bangkok or fly in directly from Singapore, Hong Kong or the Gulf. Expect 17–20 hours door to door from the West Coast with one stop, and 20-plus from the East Coast. For today's prices see LAX to Bangkok, SFO to Bangkok, JFK to Bangkok, Seattle to Bangkok and LAX to Phuket.
When fares tend to be lowest
US–Thailand demand peaks over Christmas–New Year, Chinese New Year and the mid-April Songkran week, and it stays firm through the whole cool season because that is when Europeans, Australians and Americans all want to be there. The windows when airlines and hub carriers have the most seats to fill are May–June and September–October, when the Andaman coast and Bangkok are in monsoon. Late January to early March, after the holiday rush but still in the dry season, is the compromise most people should aim for.
That is a demand-calendar argument, not a price forecast. With one US nonstop and a dozen hub carriers competing, fares move with capacity and promotions as much as season. Pick a window, check what the route is actually pricing at on LAX to Bangkok, and set a price alert at a fare you would happily pay. Wildly checks the route daily and emails you when it drops.
Entry requirements for US citizens
Per Wikivoyage's "Get in" section, US citizens may enter Thailand visa-free for tourism for up to 60 days, and the exemption is granted only twice per calendar year if entering by land or sea. Wikivoyage also notes that border officials may refuse entry without proof of onward travel, so carry evidence of your departure flight. Rules have changed several times in recent years; confirm with the Thai embassy or the official Thailand e-Visa site before you fly.
Where to go, by month
- November–February: Bangkok, Chiang Mai and the north, Phuket, Krabi and the Andaman islands.
- March–April: Beaches over cities; Songkran in Chiang Mai or Bangkok if you want the party, elsewhere if you do not.
- May–October: Ko Samui, Ko Pha Ngan and Ko Tao on the Gulf; Bangkok and the north between showers; skip the Andaman islands in September–October.
FAQ
What is the single best month to visit Thailand? February for the broadest good weather: Bangkok under an inch of rain, the Andaman coast dry, and the Christmas and Chinese New Year peaks behind you. December is the classic but busier choice.
Which coast is dry in July? The Gulf: Ko Samui, Ko Pha Ngan and Ko Tao. Phuket and the Andaman side average 9–10 inches of rain a month in June and July.
Is the rainy season a bad time to go? Not necessarily. Rain usually comes in short, heavy bursts, prices are lower and the Gulf islands are in their dry season. September and October are the months to be most careful about, especially in Bangkok and on the Andaman coast.
Can I fly nonstop from the US? United operates Los Angeles–Bangkok via Hong Kong under fifth-freedom rights; there is no true nonstop. Everyone else connects through a Northeast Asian or Gulf hub.
Do I need a visa? No, for tourist stays of up to 60 days on a US passport, per Wikivoyage. Carry proof of onward travel.
Sources
- Bangkok climate normals 1991–2020 (Thai Meteorological Department, via Wikipedia)
- Phuket climate normals 1991–2020 (Thai Meteorological Department, via Wikipedia)
- Wikivoyage: Thailand — Climate, Holidays and Get in
- Suvarnabhumi Airport — Airlines and destinations (Wikipedia)
- Airways: United authorized to expand its Southeast Asia network (DOT approval, 2025)