Is It Monsoon in Ko Samui, Thailand? Rainfall and Weather by Month

Is It Monsoon?
Ko Samui, Thailand JANUARY
27°
★★★
Shoulder season
24° to 29°
Rain Tapers Off
Still catching the tail end of the rainy season, though showers are usually brief and the dry season is just around the corner.
☔ Light rain jacket🦟 Insect repellent
27°
★★★
Peak season
25° to 29°
Driest & Coolest
The driest, most comfortable month of the year, with the lowest chance of rain and pleasantly cooler air.
☀️ Sunscreen🏖️ Beach days
28°
★★★
Peak season
26° to 31°
Peak Dry Season
Still one of the driest months, though the heat is starting to build toward the hotter months ahead.
☀️ Sunscreen🥵 Stay hydrated
29°
★★★
Peak season
26° to 32°
Heat Builds
Dry season holds through April, but temperatures climb toward the year's peak.
🥵 Heat protection☀️ Sunscreen
29°
★★★
Off-peak season
26° to 33°
Monsoon's First Peak
The hottest month of the year meets the rainy season's opening burst: hot, sticky, and increasingly wet.
🥵 Heat protection☔ Light rain jacket
29°
★★★
Shoulder season
26° to 33°
Steady Showers
Rain is frequent but usually brief, and it is common to see long dry stretches between downpours.
☔ Umbrella handy🦟 Insect repellent
29°
★★★
Shoulder season
25° to 32°
Calm Monsoon
One of the more forgiving rainy months, it can go a full week without rain, though the air stays hot and muggy.
☔ Umbrella handy🕶️ Sun and rain both
29°
★★★
Shoulder season
25° to 32°
Warm & Showery
Similar to July, showers come and go quickly and long dry, hot spells are common.
☔ Umbrella handy🦟 Insect repellent
28°
★★★
Shoulder season
25° to 32°
Showers Continue
Rain remains frequent but rarely lingers long, typically clearing to sun within the same day.
☔ Umbrella handy🦟 Insect repellent
27°
★★★
Off-peak season
24° to 31°
Rainy Peak Begins
The true rainy peak arrives, with heavier, more frequent downpours and a real risk of flooding.
☔ Heavy rain gear⚠️ Flash-flood aware
27°
★★★
Off-peak season
24° to 29°
Torrential Peak
The wettest, stormiest month of the year, as the retreating monsoon dumps heavy rain and flooding becomes a real risk.
☔ Heavy rain gear⚠️ Flash-flood aware
27°
★★★
Shoulder season
24° to 29°
Rains Begin Easing
Still wet and among the coolest months, but the worst of the rainy peak has passed.
☔ Light rain jacket🦟 Insect repellent
Drag through the year Jan
Jan
⭐️
Feb
⭐️
Mar
⭐️
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
This month
Rainfall
124 mm
8 rainy days this month
Sunshine
6.5 hrs/day
50% of daylight hours
Humidity
81%
Air feels heavy and sticky
Wind
17 km/h
Noticeable breeze
Rainfall
66 mm
4 rainy days this month
Sunshine
7.5 hrs/day
58% of daylight hours
Humidity
77%
Air feels heavy and sticky
Wind
15 km/h
Noticeable breeze
Rainfall
114 mm
5 rainy days this month
Sunshine
7.5 hrs/day
58% of daylight hours
Humidity
75%
Air feels heavy and sticky
Wind
13 km/h
Light, barely noticeable
Rainfall
84 mm
6 rainy days this month
Sunshine
6.5 hrs/day
50% of daylight hours
Humidity
74%
Air feels heavy and sticky
Wind
12 km/h
Light, barely noticeable
Rainfall
130 mm
11 rainy days this month
Sunshine
6 hrs/day
46% of daylight hours
Humidity
78%
Air feels heavy and sticky
Wind
13 km/h
Light, barely noticeable
Rainfall
135 mm
10 rainy days this month
Sunshine
5 hrs/day
38% of daylight hours
Humidity
79%
Air feels heavy and sticky
Wind
17 km/h
Noticeable breeze
Rainfall
114 mm
11 rainy days this month
Sunshine
5 hrs/day
38% of daylight hours
Humidity
80%
Air feels heavy and sticky
Wind
18 km/h
Noticeable breeze
Rainfall
99 mm
10 rainy days this month
Sunshine
5 hrs/day
38% of daylight hours
Humidity
78%
Air feels heavy and sticky
Wind
18 km/h
Noticeable breeze
Rainfall
119 mm
11 rainy days this month
Sunshine
5 hrs/day
38% of daylight hours
Humidity
80%
Air feels heavy and sticky
Wind
16 km/h
Noticeable breeze
Rainfall
295 mm
16 rainy days this month
Sunshine
4.5 hrs/day
35% of daylight hours
Humidity
80%
Air feels heavy and sticky
Wind
14 km/h
Light, barely noticeable
Rainfall
445 mm
16 rainy days this month
Sunshine
6 hrs/day
46% of daylight hours
Humidity
81%
Air feels heavy and sticky
Wind
18 km/h
Noticeable breeze
Rainfall
264 mm
12 rainy days this month
Sunshine
5.5 hrs/day
42% of daylight hours
Humidity
82%
Air feels heavy and sticky
Wind
19 km/h
Noticeable breeze
★★★ peak season, ★★☆ decent shoulder months, ★☆☆ true off-peak, based on rain frequency, heat, and haze.
Seasons at a glance
🌟
Peak season: Feb, Mar, Apr
Ko Samui's driest, sunniest stretch, though even in these months a stray shower can pass through. February and March are the driest of all, and by April the heat starts building toward the year's peak. Expect the busiest beaches and highest hotel rates of the year, book Chaweng and Lamai well ahead.
🌤️
Shoulder season: Jan, Jun, Jul, Aug, Sep, Dec
This tier spans very different parts of the year. Early January is still catching the tail end of the rains before the dry season properly begins, while June through September sit in the calmer middle of the monsoon, showers arrive most days but are usually short, and it's common to go a week without rain in July or August. December carries real rain totals too, as the wettest peak from October and November eases but hasn't fully let up yet.
☔
Off-peak season: May, Oct, Nov
May opens the rainy season with its first real burst of rain alongside the year's hottest temperatures, while October and November bring the true rainy peak, when the retreating monsoon can dump torrential, occasionally flooding rain on the island, November especially. Widely considered the worst time to visit, though hotel prices drop to match.
Good to know
✈️
Samui has its own airport, at a price
Samui International (USM) is privately owned by Bangkok Airways, which has a near-monopoly on direct flights, so tickets often cost far more than flying elsewhere in Thailand. Many budget travelers fly into Surat Thani on the mainland instead and take a roughly 1 to 1.5 hour ferry across.
🌊
Flooding is a real risk, October to December
The retreating monsoon has caused serious flooding on the east coast in past years, including a major island-wide flood in late 2016. Keep travel plans flexible if visiting during this window.
🎉
The Full Moon Party is not actually on Samui
That famous beach party happens on neighboring Ko Pha Ngan. Speedboats run regularly from Samui's piers, usually a 20 to 30 minute ride, and it's a popular night out, but don't expect it on the island itself.
🏊
The sea stays swimmable year round
Sea temperatures hold between about 28 and 30°C every month, even in the wettest weeks, so the water itself is rarely the problem, the rain is.
Top attractions
1
Big Buddha (Wat Phra Yai)
A 12-meter golden Buddha statue on a small island connected by causeway, free to visit and one of the most photographed sights on Samui.
2
Chaweng Beach
The island's longest, most famous stretch of white sand and turquoise water, lined with resorts, restaurants, and the busiest nightlife on Samui.
3
Ang Thong National Marine Park
A 42-island archipelago of limestone cliffs and hidden lagoons reachable by day trip, with kayaking, snorkeling, and a hike up to the park's emerald lake viewpoint.