Start with the place where weather matters most
For a trip centered on Bangkok and northern sightseeing, start by comparing dates in November–February. For beaches, choose the coast first: Phuket and Krabi are on the Andaman side; Koh Samui and Koh Phangan are in the Gulf. A dry week in Bangkok does not tell you whether an island boat will run.
Use the seasonal pattern to shortlist dates. Use the destination forecast, marine warnings and your operator's latest information to decide the actual day's activities.
Which region are you visiting?
The Thai Meteorological Department (TMD) describes a southwest monsoon around mid-May–mid-October and a northeast monsoon around mid-October–mid-February. The latter brings cooler, drier air to much of upper Thailand but moisture to the southern east coast. The start and end vary by year. TMD climate overview (Thai).
On a small screen, scroll the table sideways to read the checks for each region.
| Your route | Dates to compare | What to verify |
|---|---|---|
| Bangkok and central Thailand | November–February for a cooler-season city trip; March–April if you can work around heat. | Check the city forecast and build shade or indoor stops into walking days. |
| Chiang Mai and the north | Compare November–February for cooler conditions. Mountain plans need their own forecast. | Check elevation, overnight temperature and current air quality before committing to outdoor activities. |
| Phuket and Krabi: Andaman coast | Compare dates outside the southwest monsoon first if boats or beach time are the priority. | Check wave warnings, ferry operation and the specific beach's flags. A seasonal label is not permission to swim. |
| Koh Samui and Koh Phangan: Gulf islands | Do not copy Phuket's calendar: late-year northeast monsoon rain is a separate concern. | Check the southern east-coast forecast and your island transfer. Compare another coast or flexible land activities if dates are fixed. |
Why December is not a nationwide guarantee: TMD's December 2025 report describes scarce rain in much of upper Thailand while the southern east coast continued to receive rain. That is one historical month's regional contrast, not a prediction for your December trip. TMD December 2025 summary.
Already have a travel month?
Use these checkpoints to narrow a route, rather than ranking every month as universally good or bad.
- January–February: compare a city/north route with your chosen beach region; check a mountain overnight separately from a Bangkok hotel stay.
- March–April: decide how much walking you want and whether the accommodation and daily schedule suit hot conditions. A festival or fixed event can matter more to you than the coolest month.
- May–June: allow for the transition into the southwest monsoon. Check cancellation terms before making a boat trip the centerpiece of the itinerary.
- July–September: compare coasts and keep a usable land-based alternative. Rain-day counts alone do not tell you when to schedule an outdoor activity.
- October: check the forecast for every stop on a multi-region route as the monsoon pattern changes.
- November–December: do not transfer upper Thailand's cooler-season expectations to the southern east coast.
A practical check before paying
Pick the activity you would be most disappointed to lose: a mountain hike, island transfer, beach day or city walk. Give that destination priority when comparing dates. Then check the rest of your route.
These checkboxes are a temporary reading aid; selections are not saved when you reload.
Start at TMD weather and warnings and choose your province or region. For a boat day, read the marine information and confirm the route with the operator. A forecast cannot guarantee that a service will run.
Turn your route into a packing decision
- City walking: prioritize breathable clothes, sun protection and footwear you can walk in. Choose rain protection that you can carry during the day's stops.
- Boat or beach days: protect documents and electronics from spray and rain; check the operator's baggage and safety instructions.
- Mountain or cool overnight stops: choose layers from the local overnight forecast and activity, rather than a lowland monthly average.
- A route with frequent wet conditions: plan how wet clothes will dry and where laundry fits. Pack quantities around that plan rather than an assumed daily downpour schedule.
Thailand packing list: documents, temples and activity gear covers the next decisions. Use the packing-cube weight comparison to check whether organizers fit your entered baggage limit.
Build a Thailand packing list. The form starts with Bangkok; change the destination and travel dates to match your trip.
Questions that a monthly weather table cannot answer
Does rainy season mean rain all day?
Neither a monthly rain total nor a count of wet days reveals the duration or timing of individual showers. Dividing one by the other gives an average amount per counted wet day, not hours of rain. Check the short-range forecast; keep plans flexible when warnings or conditions require it.
Which month is cheapest?
Compare live quotes for your departure airport, exact dates, room type and cancellation terms. A weather table contains no fare or hotel-price data. Include transfers and the cost of changing an activity before deciding which option is better value.
Why is the old Bangkok table no longer here?
The previous table summarized one year, 2025, for Bangkok. Open-Meteo's historical service uses weather reanalysis, which combines observations with modeling; it is not a set of direct measurements at your hotel. A single year is not a long-term climate normal and cannot stand in for every Thai region. Open-Meteo historical data methods.
Regional season patterns are used here for initial planning, with forecasts for near-departure choices. We do not promise dry days, fixed shower lengths or a cheapest month.
Next food decision: Thai dishes and questions to ask when ordering.