Fall in Koh Samui brings a mix of warm weather, high humidity, and frequent showers that really shape the island’s tropical rhythm. Daytime highs usually sit between 85°F and 89°F, while nights stay comfortably warm around 79°F.
Rain happens a lot, but the sun still manages to break through, and the sea stays inviting for swimming.
September starts off wetter, and by November, the rain really ramps up, often hitting its peak for the year. As fall moves along, skies gradually clear a bit, giving you more chances to hit the beach or try outdoor fun between showers.
If you’re wondering how fall stacks up to other seasons, it helps to know what to expect. Whether you’re after lazy beach days, curious about local festivals, or just trying to figure out what to pack, knowing the average fall weather in Koh Samui makes planning a trip a whole lot easier.
Overview of Fall Weather in Koh Samui
In the fall, you’ll get warm tropical temps, plenty of rain, and sticky humidity. Days get a bit shorter, clouds move around, and the sea and winds slowly shift as the season goes on.
Temperature Trends During Fall
Most days, highs in Koh Samui range from 89°F (32°C) in early fall to about 85°F (29°C) by late November. Nights don’t cool off much, with lows around 79°F (26°C), so you can usually stick with light clothes.
The sea stays warm enough for swimming, with water temps dropping only slightly from 85°F (29°C) to 83°F (28°C). Unlike some places, day and night temps don’t really swing much, so things feel steady but definitely humid.
Compared to the hottest spring months, fall feels a touch cooler but still pretty muggy. Sometimes a coastal breeze helps, especially later in the season when winds start blowing in more from the east.
Rainfall and Humidity Patterns
Rain really defines fall in Koh Samui. There’s about a 50% chance of a wet day, and October and November bring the heaviest showers. Monthly rainfall can hit 12 inches (300 mm), making November the wettest month on the island.
Showers usually come in short, intense bursts, then clear up for a while. After a lot of rain, low-lying areas sometimes flood, so you might need extra travel time.
Humidity stays high, with dew points above 75°F (24°C) all season. Expect muggy air all day and night, and you’ll probably want air conditioning or at least a fan to stay comfortable.
Sunshine Hours and Cloud Cover
Days get a bit shorter through the fall, from around 12 hours in September to 11.5 hours by late November. Sunrises come later, sunsets a bit earlier, so there’s a little less outdoor time.
Clouds hang around a lot, especially in September and October, when it’s mostly cloudy or overcast more than 70% of the time. By late November, things clear up a bit, but sunny days are still pretty rare.
Even with all those clouds, UV levels stay strong in Thailand. You’ll want sun protection whenever the sun does pop out, since those breaks can bring some pretty intense rays.
Month-by-Month Breakdown: September to November
In fall, Koh Samui shifts toward wetter conditions, shorter sunny spells, and higher humidity. Temperatures stay warm, but the rain patterns make each month feel different when it comes to comfort and planning.
September Weather Highlights
September stays warm, with highs around 30–31°C (86–88°F) and lows near 25°C (77°F). The sea is still nice at about 29°C (84°F), so swimming and water activities are definitely doable.
Rain starts to pick up compared to summer. You’ll probably see 120–130 mm (4.7–5 in) of rain, spread over plenty of days. Showers hit hard and fast, so packing light rain gear is a good idea.
Humidity sticks above 80%, making afternoons feel sticky. Even with the rain, you get about 12 hours of daylight, and mornings often work best for outdoor plans before showers roll in later.
October Weather Highlights
October brings some of the heaviest rain in Koh Samui, with totals around 300 mm (12 in). You might see as many as 20 rainy days, with heavy downpours and the occasional thunderstorm.
Temperatures hold steady, with highs at 30°C (86°F) and lows near 24–25°C (75–77°F). The sea stays warm at 29°C (84°F), though storms can make the water a bit murky.
Humidity peaks at about 85%, and you’ll notice fewer sunshine hours. You can still get out and do things, but it’s smart to keep your plans flexible. Indoor attractions, spas, or quick trips between showers work best.
November Weather Highlights
November is the height of the monsoon season in Koh Samui. Rainfall often tops 500 mm (20 in), with frequent and heavy downpours. You can expect rain most days, and flooding in low spots isn’t unusual.
Temperatures stay mild, with highs near 29°C (84°F) and lows around 24°C (75°F). The sea holds at 29°C (84°F), but it gets rougher—so boat trips or snorkeling might be off the table.
Humidity stays up near 85%, and sunshine is pretty limited. If you visit this month, plan for more indoor time and fewer long stretches on the beach.
Comparing Fall to Other Seasons in Koh Samui
Fall in Koh Samui means more rain and humidity than other times of year. The island stays warm, but sunshine and storms trade places depending on the month.
Dry Season Versus Fall
Koh Samui’s dry season usually runs from mid-December through April. During that time, you’ll get steady sunshine, calm seas, and lower humidity. Daytime temps average 28–32°C (82–90°F), which is why the beaches fill up.
In fall, especially October and November, rain is much more common. November often brings over 500 mm of rain, which can really mess with outdoor plans. Temperatures stay about the same, but the higher humidity makes it feel heavier.
If you’re after the best time to visit Koh Samui for swimming, snorkeling, or just soaking up the sun, dry season is your best bet. Fall is still warm, but skies are cloudier and beach days aren’t as reliable.
Rainy Season Versus Fall
Koh Samui’s rainy season doesn’t line up with the rest of Thailand. Instead of peaking in summer, the heaviest rain comes in late fall, especially November. That makes fall the wettest time of year here.
Earlier rainy months like May and June bring shorter showers and more sunshine. In October and November, though, you’ll see longer downpours and rougher seas, which can make ferry rides and water sports tricky.
The upside? Fall is less crowded and hotels are sometimes cheaper. You’ll find sunny breaks, but it’s best to keep your schedule flexible. If you don’t mind rain or want fewer tourists, fall can work. If you want guaranteed beach weather, the earlier rainy season months might be easier.
How Fall Weather Affects Beach Holidays
Rain and shifting winds really change how you’ll enjoy the beach. Temperatures stay warm, but the sea and sky can affect swimming, boating, and other beach plans.
Sea Conditions and Swimming
Fall brings choppier seas to Koh Samui compared to the calm water of late winter and spring. October and November, especially, see stronger winds and higher waves as the rainy season peaks.
The Gulf of Thailand stays warm, around 27–29°C (81–84°F), so swimming is still comfortable. But currents pick up, and snorkeling visibility drops when rain stirs up the water.
Some days, you’ll see red flags on the beaches—especially in November, when storms are common. Lifeguards might restrict swimming during rough surf. On calmer days, you can swim safely, but it’s smart to stay close to shore and watch for warnings.
If you’re thinking about diving or snorkeling trips, tour operators often change schedules depending on the weather. Conditions are usually better early in the fall, while late fall often brings more cancellations.
Beach Activities in the Fall
Beach holidays in fall are still fun, but you’ll probably need to adjust your plans. Afternoon showers pop up a lot, so mornings are usually best for paddleboarding, kayaking, or just walking the shore.
Sand quality mostly stays good, but heavy rain can leave it damp for a while. With fewer visitors, you’ll have more space on the beach.
When rain hits, covered beach bars and cafes let you hang out by the water without getting soaked. Many resorts set up sheltered spots, so you can still enjoy the coast even if it’s pouring.
If sunbathing is your thing, October usually has more clear spells than November. By late fall, clouds increase, but it’s still warm enough to relax on the sand between showers.
Travel Tips for Visiting Koh Samui in the Fall
Fall means warm temps, high humidity, and the start of the rainy season in Koh Samui. You’ll get a mix of sun and passing showers, so if you prep for both, you’ll be a lot more comfortable.
What to Pack for Fall Weather
Pack light, breathable clothes, since days average around 26–30°C (79–86°F). Cotton or linen shirts, shorts, and dresses work well in the humidity. A light rain jacket or poncho comes in handy, especially from late October through November.
Bring sandals for the beach and water-resistant shoes for wet streets. Mosquito repellent is a must, since bugs get busier when it’s wet. Don’t skip sunscreen, because UV is strong even on cloudy days.
If you plan to take boats, pack seasickness bands or motion tablets—the seas can get rough in fall. A small umbrella, quick-dry towel, and waterproof bag help keep your stuff dry during sudden showers.
If you want to visit temples or eat at nicer places, bring modest clothes like long skirts, pants, and shirts with sleeves. They’ll also help with mosquitoes in the evening.
Accommodation and Crowds
Fall is shoulder season in Koh Samui, so things are quieter than the busy months from December to February. Hotels are easier to book, and rates are often lower.
Luxury resorts around Choeng Mon or Bophut sometimes offer deals, and mid-range or family hotels aren’t as crowded. Pools, beaches, and restaurants feel calmer, which is honestly pretty nice.
Rainy days can limit outdoor tours, but most hotels offer indoor activities or spa options. Booking flexible stays helps if the weather changes. If you want privacy and lower prices, fall is a really practical time to visit.
Local Events and Festivals During Fall
Fall in Koh Samui mixes cultural traditions with lively seasonal events. You’ll get a taste of religious ceremonies, national holidays, and unique island gatherings that show off both Thai heritage and the local festive spirit.
Cultural Celebrations
In October, Wan Awk Phansa signals the end of Buddhist Lent. Temples all over Koh Samui host ceremonies, and locals show up with offerings for the monks.
This celebration feels quieter and more reflective than others, but honestly, it gives you a real window into Thai religious life.
Later in October, Chulalongkorn Memorial Day honors King Chulalongkorn. People across Thailand observe it with respect and remembrance.
It’s not a festival with parades or parties, but it does shape public schedules and you might catch some unique local traditions if you’re around.
In November, Loy Krathong arrives with the full moon. Locals float decorated baskets, or krathongs, on the water to let go of negativity.
On Koh Samui, you’ll find beaches, ponds, and temples glowing with candlelit offerings. It’s honestly one of the most visually stunning events you’ll see all season.
Seasonal Attractions
Fall brings a mix of cultural charm and lively nightlife. The nearby island of Koh Phangan hosts the Full Moon Party, and plenty of visitors make the trip from Koh Samui.
If you like smaller crowds, you might check out the Half Moon Festival or the Jungle Experience. Both events pop up around the same time and focus on outdoor music and dancing.
You’ll probably spot local regattas and fun runs during the cooler months before peak tourist season. These events really show off the island’s active vibe, and you can either join in or just watch from the sidelines.
Markets and food fairs start popping up everywhere as well. Vendors bring out Thai street food, handmade crafts, and whatever’s in season, so you can soak up the island’s fall atmosphere at your own pace.