When is the best time to visit Thailand?

Thailand by season in one view

Thailand has no single best month, because the country is long and faces two seas. The north and the centre follow one calendar, the Andaman coast (Phuket) another, and the Gulf of Thailand islands (Ko Samui) a third. A trip that looks ideal in the north in January can fall in a different part of the rain cycle for the Gulf in November.

This page uses monthly averages for four stations that the Thai Meteorological Department supplies to the WMO: Bangkok for the central plain, Chiang Mai for the north, Phuket for the Andaman coast and Ko Samui for the Gulf. Bangkok's figures cover 1961 to 1990; the WMO page does not state a period for the other three, so read them as long-run averages rather than recent weather.

The national monsoon pattern

The World Bank Group and Asian Development Bank climate profile (2021) describes a tropical climate driven by monsoon winds. It places the wet monsoon season from May to October and says the northeast monsoon, starting in October, brings cold, dry air mostly to the north and northeast. In the south it says the same monsoon gives mild weather and abundant rain along the eastern coast.

For the 1991 to 2020 period the profile puts the national mean annual temperature at 26.3 degrees Celsius, the hottest months at April and May and the coldest at December and January. It gives mean annual rainfall as 1,542 mm, with August and September the wettest months at roughly 255 mm each. Those are country-wide averages, so they smooth over the contrasts shown in the station tables below.

The Thai Meteorological Department (TMD) gives year-specific markers. Its May 2025 summary states that continuous rain across the country marked the beginning of the rainy season on 15 May that year, and its August to October 2025 outlook, describing the 1991 to 2020 normal, says most areas get their heaviest monthly rain of the year in September. It describes October as the change from the rainy to the cool season, with cooler air in the upper country from mid-month, while the south still gets heavy rain in the second half of the month.

Central Thailand: Bangkok

Bangkok is hot all year. The average high ranges from 31.3 degrees Celsius in December to 34.9 in April, and the average low never falls below 20.8. The rain cycle is the clearer signal: January averages 9.0 mm on 1.0 day, while September averages 344.0 mm on 18.0 days, the wettest month in this 1961 to 1990 set.

For a city stay that means the driest and least hot stretch is usually November to February, when monthly rain runs from 9.0 to 48.0 mm, and the heat of March to May arrives before the rains. If you are choosing a base for a month or more, our guide to Bangkok neighbourhoods for long stays covers the practical side, and a kitchen helps on days when afternoon rain makes eating out less appealing.

Northern Thailand: Chiang Mai

Chiang Mai has the widest temperature swing of the four stations. Its average low is 14.2 degrees Celsius in January against 23.9 in June, and the average high peaks at 36.1 in April, higher than any month at Bangkok, Phuket or Ko Samui in these tables. That fits the TMD May 2025 summary, which reports hot weather persisting in the upper country early in the month, with very hot conditions in some northern areas.

Rain follows the monsoon. January and February are the driest months at 7.7 and 9.2 mm, and August is the wettest at 224.6 mm on 20.6 days. November to February is when the northeast monsoon's drier, cooler air is most evident in the north, with November to January daytime averages between 28.3 and 29.8 degrees. If you are weighing Chiang Mai for a longer stay, the cooler months are the usual choice, though the figures show nights of about 14.2 to 15.3 degrees even then.

Andaman coast: Phuket

Phuket's temperatures barely move: average highs sit between 31.2 and 33.8 degrees Celsius all year. Rain is what changes. January averages 23.3 mm and February 25.8 mm, but from May to October every month averages 236.9 mm or more, with September the wettest at 386.5 mm on 22.8 days.

So the coast's drier window is roughly December to March on these averages, with 61.9 mm in December and 59.0 mm in March, while April (137.8 mm) and November (173.7 mm) are the transition months. We have no source for sea conditions, so check local operators' schedules for the dates you plan.

Gulf of Thailand: Ko Samui

Ko Samui follows a different rain calendar from Phuket. In July it averages 122.8 mm, against 284.1 mm at Phuket, and in September 116.8 mm against 386.5. Its wet peak comes late: October averages 290.2 mm and November 489.6 mm on 19.6 days, the wettest month at this station, against 173.7 mm for Phuket in November.

The driest stretch is February to April, with 57.8, 77.8 and 76.6 mm. This fits the climate profile's note that the northeast monsoon brings abundant rain along the eastern coast of the south. For anyone planning a Gulf beach stay, the contrast with the Andaman side is the main planning fact: a month that suits one coast can be the wettest on the other. Closer to Bangkok, Hua Hin and Pattaya lie on the Gulf too, but we have no station table for them here.

Heat, floods and tropical cyclones

Three seasonal hazards are worth planning around, and none of them is a forecast for your dates. The first is heat in the hot months: the ADB and World Bank profile names April and May as the hottest months nationally, and the Chiang Mai table shows April as its peak.

The second is flooding in the wet season. In its October 2025 summary TMD reported abundant rain almost the whole month, with flooding in many provinces including Chiang Mai, Phitsanulok, Ubon Ratchathani and several central provinces, linked in part to the remnants of typhoon Matmo over northern Vietnam early in the month. The same summary puts October 2025 national rainfall 9 % below normal, so this is one dated example of local flooding, not a guide to any other year.

The third is tropical cyclones. TMD's August to October 2025 outlook, again describing the 1991 to 2020 normal, notes that some tropical cyclones may move toward the north and northeast in August, dissipate near or toward Thailand in September, and approach the east and the upper Gulf in October. For live warnings during your trip, use the TMD website rather than seasonal averages.

Best months by purpose

The list below is our reading of the station tables and the sources above. It is a selection by weather, not a ranking, and it ignores crowds and prices.

• Cooler, drier north: November to February, when Chiang Mai rain is 7.7 to 51.3 mm a month at the extremes of that run and daytime averages are 28.3 to 32.2 degrees Celsius.
• Andaman beaches: January to March, with Phuket at 23.3, 25.8 and 59.0 mm.
• Gulf islands: February to April, with Ko Samui at 57.8, 77.8 and 76.6 mm.
• Bangkok city days: November to February, when monthly rain runs from 9.0 to 48.0 mm on the 1961 to 1990 averages.
• Avoiding the worst of the heat: skip March to May in the north, where Chiang Mai April averages 36.1 degrees.
• Less rain in the wet season: June to August on the Gulf side, where Ko Samui rain is well below Phuket's in the same months, if you accept showers.

Shoulder seasons and planning notes

The shoulder months differ by coast. On the Andaman side, April and November sit between the dry and wet seasons (137.8 and 173.7 mm). On the Gulf side the shoulder is May and June (about 146.5 and 112.7 mm) and again around December (209.1 mm), after the late wet peak. In the north, October is the hinge month, with rain falling to 118.1 mm from 200.2 mm in September.

For longer stays, a kitchen can make wet-season weeks easier because you are not tied to restaurant hours when storms pass. Compare apartment-style stays in the table above for the places we list, and see our note on aparthotels in Asia for long stays. For entry rules, check the official Thai immigration website before you book.