Thailand Monsoon 2026: When the Rainy Season Starts and Ends in Bangkok, Phuket & Koh Samui
✅ Last verified on-the-ground: 2026-07-23
Thailand does not have one monsoon. It has two, running on opposite calendars, and that single fact decides whether your July Phuket trip is sunny or a washout. The southwest monsoon hits the Andaman coast (Phuket, Krabi, Phi Phi) from May through October. The Gulf coast (Koh Samui, Koh Phangan, Koh Tao) waits it out, then catches the other side of the same system from September through December. Bangkok sits between them, getting a shorter, sharper wet season roughly June through October. Picking the wrong window is the difference between ₹858 (~300 THB or ~$8.90) dorm beds on dry islands and ₹4,288 (~1,500 THB or ~$44.51) beds in a rain-lashed Patong. Here is the month-by-month breakdown, the cost swings, and what happens on the ground. For related planning, see our guides on Sea Backpacking Hub and Thailand Monsoon Season Honest Review Should You Go.
Quick Answers
| What | Answer | Price (INR) |
|---|---|---|
| When does monsoon start in Bangkok? | Mid-May to early June, runs through October | ₹0 |
| When does monsoon start in Phuket (Andaman)? | Mid-May, peaks Aug-Oct | ₹0 |
| When does monsoon start in Koh Samui (Gulf)? | September, runs through December | ₹0 |
| Cheapest month to fly Bangkok from India | June or September | ₹12,000 (~$124.56) |
| Best month for Andaman diving visibility | February to April | ₹18,000 (~$186.84) |
The Two Monsoons, in Plain English
Thailand gets rain from two different weather systems, and they hit at opposite times. The southwest monsoon, blowing up from the Indian Ocean, soaks the west coast from May through October. That is Phuket, Krabi, the Similan Islands, and Phi Phi getting rained on. Then the wind reverses around October, and the northeast monsoon drags rain down across the Gulf of Thailand. That is Koh Samui, Koh Phangan, and Koh Tao getting drenched from September right through December. There is a window, roughly late October to early December, where both coasts are wet at the same time. Travellers who plan around only one monsoon almost always get caught by the other. You may also find Thailand Weather By Month Phuket useful for this trip.
Bangkok itself is inland, so it dodges the worst of both. Its rainy season runs roughly June through October, with September the wettest month on average. The rain in Bangkok is short, sharp, and predictable: build any afternoon plan around a 2 to 3 hour window starting around 4 PM. Streets flood fast, drains are bad, and the BTS does not close, so you keep moving. It is annoying, not a deal-breaker. See also: Chiang Mai Burning Season Survival Guide.
Month-by-Month Breakdown
| Month | Weather | Crowds | Cost Level | Verdict |
|---|---|---|---|---|
| January | Dry, cool, peak season everywhere | high | Peak (₹₹₹) | Best month, most expensive |
| February | Dry, warming up | High | Peak (₹₹₹) | Great diving in Andaman |
| March | Hot, dry, haze starts in north | High | Shoulder-peak (₹₹) | Last dry month for Andaman |
| April | Hottest month, Songkran crowds | Peak Songkran | Peak (₹₹₨) | Avoid north, fine for islands |
| May | Rains begin Andaman, Gulf still dry | Falling | Shoulder (₹₹) | Gulf islands at their best |
| June | Bangkok wet, Andaman wet, Gulf dry | Low | Budget (₹) | Best month for Koh Samui |
| July | Peak southwest monsoon, Andaman wet | Lowest Andaman | Cheapest (₹) | Similan closes, Phuket quiet |
| August | Peak southwest monsoon continues | Lowest | Cheapest (₹) | Same as July, plus flooding risk |
| September | Worst Andaman rain, Gulf starts wet | Lowest | Cheapest (₹) | Bangkok floods possible |
| October | Transition month, both coasts wet | Rising | Shoulder (₹) | Hit-and-miss, check forecasts |
| November | Andaman dry again, Gulf still wet | Rising fast | Shoulder (₹₹) | Phuket opens up |
| December | Dry everywhere except Koh Samui | High | Peak (₹₨) | Christmas rush begins |
Subodh’s Pro Tip: If you want one window that covers both coasts, book late December through January. If you want cheap and dry on just one coast, target June (Gulf) or November (Andaman). For related planning, see our guide on Scuba Diving Thailand Similan Islands Best Visibility Season.
Pros and Cons of Monsoon Travel in Thailand
Pros:
- Cheapest flights of the year, often ₹12,000 (~$124.56) round trip from Delhi or Mumbai into Bangkok
- Dorm beds in Phuket drop to ₹858-₹1,429 (~300-500 THB or ~$8.90-$14.84) a night, half the December rate
- No queues at the Grand Palace, Maya Bay, or Railay Beach
- Lush green landscapes, fewer sunburns, lower humidity on some islands
- Dive sites like the Similan close anyway, so prices on liveaboards in other regions drop
Cons:
- Ferry cancellations between Phuket and the Phi Phi Islands are routine in July and August
- The Similan Islands national park closes entirely from mid-May to mid-October for marine recovery
- Koh Samui gets slammed September through November, the opposite of what most first-time visitors expect
- Bangkok floods can strand you for a day or two if you are on a tight schedule
- Some beach resorts on the Andaman shut down completely for the low season
The price swings are real, but so are the trade-offs. A dorm bed in Phuket Old Town that runs ₹3,431 (~1,200 THB or ~$35.61) in January drops to ₹858-₹1,429 (~300-500 THB or ~$8.90-$14.84) in July and August, and you can usually negotiate a private room for under ₹2,287 (~800 THB or ~$23.74). Flights from India follow the same curve: December and January flights from Mumbai to Bangkok are ₹22,000-₹28,000 (~$228.36-$290.64) round trip, June and September are often ₹11,000-₹14,000 (~$114.18-$145.32) on the same route. The catch is that you are paying for the risk. If a typhoon tracks across the Andaman, ferries stop, boats cancel, and you lose two or three days of your trip. Travellers report that July and August rain is usually 2 to 4 hours of heavy afternoon showers with dry mornings, not full-day downpours, but you should still budget a flex day or two.
Region-by-Region: What Happens
Bangkok and Central Thailand
The capital’s wet season runs roughly mid-May through October, with September the worst month. Rain comes in heavy, predictable bursts, often between 4 PM and 7 PM. Mornings are usually dry. Flooding is a real risk in low-lying areas near the Chao Phraya, but the BTS, MRT, and most malls stay operational. The good news: humidity is lower than April, temperatures sit around 30 to 33°C instead of 38°C, and accommodation is cheap. A dorm bed in Khao San or Silom runs ₹715-₹1,115 (~250-390 THB or ~$7.42-$11.57) in the wet months, compared to ₹1,429-₹2,287 (~500-800 THB or ~$14.84-$23.74) in December.
Phuket, Krabi, and the Andaman Coast
This is the side most travellers ask about, and it is the worst-behaved during the southwest monsoon. Rain begins in mid-May, builds through June and July, peaks in August and September, then drops off sharply in October. November opens up, and December through April is reliably dry. The Similan Islands close for the season from May 16 to October 15 every year, full stop. Maya Bay on Phi Phi also closes periodically for reef recovery, check the national park notice before booking ferries. If you are diving, the Andaman is at its best from February to early April, when visibility is 20 to 30 metres and the water is calm.
Koh Samui, Koh Phangan, and the Gulf Coast
The Gulf coast runs on the opposite calendar. The southwest monsoon barely touches it, so June, July, and August are dry, sunny, and pleasant. Koh Samui in July is one of the underrated months in Thailand: low crowds, calm seas, dorm beds at normal rates (₹743-₹1,115 (~260-390 THB or ~$7.72-$11.57)), and ferry connections all running. The catch is October through December. The northeast monsoon turns the Gulf wavy and rainy, and the Full Moon Party on Koh Phangan in November or December is a wet, muddy affair compared to the February edition. Travellers report December ferry cancellations between Koh Samui and Koh Phangan are common.
What to Pack for Monsoon Thailand
Pack for rain that arrives hard and stops fast. You want quick-dry shirts over cotton, a real rain poncho (the 7-Eleven ones disintegrate in a week), and a dry bag for your phone and passport on boat days. A pair of cheap sandals with grip helps on flooded sidewalks. Skip the heavy jacket unless you are heading north to Chiang Mai in December or January, when nights drop below 15°C.
If you are doing any island hopping, add sea sickness pills to your kit. The Andaman in July and August gets choppy enough that even seasoned boat travellers get queasy. Pharmacies in Bangkok and Phuket sell them cheap.
Safety Alert: Thailand’s monsoon flooding can be sudden, especially in low-lying Bangkok neighbourhoods and rural areas north of the capital. Before any monsoon trip, check the Indian MEA travel advisory at mea.gov.in and Thailand’s own Disaster Relief Monitoring portal for current flood and weather warnings. Do not drive motorbikes in heavy rain, road fatalities spike in monsoon months.
Season Costs Comparison
| Item | Peak Season | Shoulder Season | Low (Monsoon) Season |
|---|---|---|---|
| Flight from India (round trip) | ₹25,000 (~$259.50) | ₹18,000 (~$186.84) | ₹12,000 (~$124.56) |
| Dorm bed Phuket (per night) | ₹1,429 (~500 THB or ~$14.84) | ₹1,001 (~350 THB or ~$10.39) | ₹858 (~300 THB or ~$8.90) |
| Dorm bed Bangkok (per night) | ₹1,144 (~400 THB or ~$11.87) | ₹858 (~300 THB or ~$8.90) | ₹715 (~250 THB or ~$7.42) |
| Dorm bed Koh Samui (per night) | ₹1,287 (~450 THB or ~$13.35) | ₹915 (~320 THB or ~$9.50) | ₹743 (~260 THB or ~$7.72) |
| Private room Bangkok (per night) | ₹4,288 (~1,500 THB or ~$44.51) | ₹2,859 (~1,000 THB or ~$29.68) | ₹2,287 (~800 THB or ~$23.74) |
| Local street meal (pad thai) | ₹172 (~60 THB or ~$1.78) | ₹172 (~60 THB or ~$1.78) | ₹172 (~60 THB or ~$1.78) |
| Full Moon Party ticket Koh Phangan | ₹572 (~200 THB or ~$5.94) | ₹572 (~200 THB or ~$5.94) | ₹572 (~200 THB or ~$5.94) |
Dorm and private room figures use the canonical ranges for Bangkok, Phuket, and Koh Samui (Gulf coast uses the Koh Phangan normal range, since Koh Samui dorms track the same market). Food and event prices barely move by season. Flights and accommodation are where you save.
Getting Connected
For real-time flood alerts, typhoon tracking, and ferry cancellation notices, you need data working the moment you land. Get Nomad eSIM covers Thailand and lets you load it before you fly.
FAQ
Is it worth going to Thailand during the monsoon? Yes, if you pick the right coast for the right month. June in Koh Samui is excellent. July in Phuket is cheap but wet. Travellers report that monsoon rain is usually a 2 to 4 hour afternoon window, not all-day, so you can still sightsee.
When is monsoon season in Phuket 2026? Mid-May through October, peaking in August and September. November opens up.
When is monsoon season in Koh Samui 2026? September through December, with October and November the wettest. June, July, and August are dry on the Gulf.
Can I do the Full Moon Party during monsoon? Yes, Koh Phangan runs them every month. The November and December editions are wetter and muddier than the February or March ones. Book early if you want a dorm bed during Full Moon week, prices spike to ₹4,288-₹6,290 (~1,500-2,200 THB or ~$44.51-$65.29).
Is it safe to travel to Thailand during monsoon season? Generally yes, but check the Indian MEA travel advisory and Thailand’s Disaster Relief portal before you fly. Bangkok floods and typhoon tracking across the Andaman are the two real risks.
How much cheaper is monsoon travel? Flights drop 40 to 50 percent from peak. Dorm beds drop 30 to 50 percent. Tours and ferries sometimes drop, sometimes stay flat because operators price for margins.
What is the green season? Marketing term for the monsoon. Same rain, fancier name. Operators use it to sell July and August trips.
Subodh’s Take
Two monsoons, opposite coasts, opposite months. Travellers who try to do Phuket and Koh Samui in the same July trip will get one coast in sun and the other in rain, and there is no fixing that without moving the dates. The honest move: pick one coast for the trip, target either June (Gulf) or November (Andaman) for the cheapest dry window, or pay full price and go in January when both coasts are reliable. Monsoon travel is fine if your itinerary has flex days, but it is not the right pick if you have a hard 7-day window with three islands locked in.
