Koh Samui Weather in December

🇹🇭 Thailand

25°C

High

23°C

Low

Rain Days

10h

Sunshine

82%

Humidity

Asia › 🇹🇭 Thailand › Koh Samui

Updated: March 2026

Is December a Good Time to Visit Koh Samui?

5/10

Fair

December is a fair time to visit Koh Samui (5/10). With 10 daily sunshine hours and only 14 rain days, this month delivers genuinely reliable outdoor conditions, ranking it 7th sunniest of the year in Koh Samui. Culture-focused travellers and those who prefer lighter crowds will find December a practical choice, with prices running lower than peak February without sacrificing all the good weather. November offers a similar profile at lower hotel rates if dates are flexible. The main practical note: Koh Samui's popular sites are busiest between 10am and 3pm regardless of season. Arriving at opening time or after 4pm makes a significant difference to the experience. Planning tips: accommodation is generally available without long lead times, and flight prices are typically lower than peak season. Flexible travellers will find the best deals by booking 2-4 weeks ahead. Mid-week arrivals consistently unlock lower hotel rates than weekend check-ins.

vs November:25°C avg high

Step off the plane in Koh Samui in December and the air meets you at around 25°C, a temperature that feels genuinely welcoming after a long flight. By the time evening arrives and temperatures settle near 23°C, the city takes on a different character entirely. With 10 hours of daylight sun on offer, December gives you the raw material for a genuinely memorable trip.

25°C

Avg High

23°C

Avg Low

14 days

Rain Days

10h

Sunshine

82%

Humidity

Temperature in Koh Samui in December

The narrow 2°C gap between daytime and overnight temperatures, characteristic of coastal cities with maritime moderation, means a single mid-layer works across the whole day. At 82% humidity, the 25°C daytime high feels 2-4°C warmer in practice: quick-dry fabrics and shade-seeking between noon and 3pm are the sensible response. The UV index of 3 is low, meaning sun exposure is minimal concern and sunscreen is largely optional. Wind averages 23 km/h, light enough to be refreshing on warm days but noticeable in open coastal areas or elevated viewpoints. In Fahrenheit: 77°F average high, 73°F overnight low. Data sourced from Open-Meteo ERA5 climate reanalysis (1991–2020 normals).

Temperature in December

Monthly Precipitation (mm)

What to Wear in Koh Samui in December

Morning23°CBefore the day warms up

Afternoon25°CPeak daytime temperature

Evening26°CAfter sunset cools down

Packing for Koh Samui in December means dressing for 25°C days and 23°C evenings. A light cotton tee with a casual overshirt works well at 25°C, the overshirt doubles as a layer for air-conditioned venues. Evening temperatures settle at 23°C, a modest 2°C drop that a light cardigan or denim jacket covers. Comfortable walking trainers are the versatile choice for both outdoor sightseeing and indoor venues. With 14 rain days expected, a compact travel umbrella is worth the bag space. A waterproof jacket is better than an umbrella if you plan full-day outdoor routes. For temple and religious site visits, carry a lightweight scarf or sarong to cover shoulders and knees, required at most major sites across the region. At 82% average humidity, quick-dry synthetic or bamboo fabrics dry overnight and stay comfortable longer than cotton.

💡

Local tip: Temple and religious site visits require covered shoulders and knees in most of Koh Samui's heritage areas. A lightweight scarf or sarong weighs almost nothing and solves the problem instantly.

Events in Koh Samui in December

December has no major festivals or public holidays in Koh Samui, which is one of its practical advantages for independent travellers. Attractions run at lower capacity than during peak event periods, queues are shorter, and accommodation is easier to find without needing to book many months in advance. Local restaurants, markets, and transport operate at a relaxed pace, making this an ideal time for visitors who prefer a more authentic, unhurried experience of everyday city life rather than large crowds drawn in by a single major headline event.

What to Pack for Koh Samui in December

Based on 25°C average highs and 14 rainy days

Light layers for morning and evening
Breathable T-shirts and comfortable trousers
UV-protective sunglasses
Compact folding umbrella
Waterproof outer layer or packable rain jacket
Quick-dry clothing that recovers fast after a shower
SPF 30+ sunscreen
Comfortable walking shoes (a second pair lets the first air out overnight)
Universal travel adapter
Small day pack for city exploration
Reusable water bottle

Best Activities in Koh Samui in December

Explore outdoor markets and street food stallsMid-morning (10am-12pm)At 25°C, the temperature is ideal for extended walking without overheating
Guided walking tour of the historic centreMorning or late afternoonComfortable temperatures allow several hours on foot without fatigue
Visit rooftop viewpoints and observation decksGolden hour (1 hour before sunset)Warm clear evenings provide exceptional visibility for panoramic photography
Day trip to the surrounding countryside or coastFull day (depart by 8am)December is reliably dry enough for rural day trips without weather risk
Spend a morning in the national or city art museumOpens at 10am; arrive earlyWith 14 rain days expected, having a full-day indoor plan is practical insurance
Cooking class focused on regional cuisineHalf-day sessions run 10am-1pm or 3-6pmIndoor activity that fills a rainy half-day with genuine cultural content
Visit covered historical sites: cathedral, palace, or bazaarAny time; most crowded middayRoofed monuments and covered markets provide exploration without weather exposure
Visit the main botanical garden or city park at seasonal peakYear-round; best light in morningDecember brings distinct seasonal changes to public green spaces worth exploring
Try the seasonal farmer's market for local produce and street foodSaturday morning markets typically 8am-1pmDecember seasonal produce is at peak availability, offering dishes not found at other times of year

Why is Koh Samui warm in December?

In December, Koh Samui sits in the dry season corridor, as the ITCZ shifts away from the region and trade winds bring drier, more stable air. This produces reliably sunny days reaching 25°C, with lower humidity than the wet months. Overnight lows of 23°C offer a pleasant reprieve from the midday heat. Climate data: Open-Meteo ERA5 (1991–2020).

Sunshine Hours

The average number of hours per day with direct sunlight. Calculated from satellite measurements. Days with more than 7 hours of sunshine are ideal for outdoor activities. Under 3 hours means overcast conditions dominate.

UV Index

A scale from 0-11+ measuring ultraviolet radiation intensity. UV 0-2: Minimal risk. UV 3-5: Moderate -- wear sunscreen. UV 6-7: High -- hat and SPF 30+ essential. UV 8-10: Very High -- limit midday exposure. UV 11+: Extreme -- seek shade between 10am-4pm.

Rain Days

A rain day is counted when precipitation exceeds 0.1mm. This threshold captures even light drizzle. Unlike total rainfall in mm, rain days tells you how often you might need an umbrella, which is useful for planning outdoor activities.

Humidity

Relative humidity as a percentage. Below 40%: Dry -- skin and throat may feel parched. 40-60%: Comfortable -- ideal for most people. 60-80%: Sticky -- light, breathable fabrics recommended. Above 80%: Muggy -- heat feels more intense; quick-dry clothing is essential.

Frequently Asked Questions: Koh Samui in December

In December, Koh Samui experiences average highs of 25°C (77°F) and lows of 23°C (73°F). Expect around 14 rainy days and 10 hours of sunshine per day, with humidity averaging 82%. The 2°C gap between daytime and overnight temperatures is worth planning around: light layers work for most visitors during the day, but an overshirt or cardigan handles the cooler evenings. UV exposure is moderate at index 3.

Koh Samui typically sees 14 rainy days in December, with total precipitation of around 147mm. Rain is moderate and manageable. Showers tend to pass quickly, and a light rain layer or foldable umbrella is sufficient protection for most days. For context, the driest month in Koh Samui typically sees 4-6 fewer rain days than December.

Pack light layers, a light jacket for evenings, comfortable walking shoes, and sunscreen for Koh Samui in December. Daytime temperatures of 25°C are pleasant, but the evening drop to 23°C means a jacket is essential if you plan to be out after dark. With 14 rainy days, bring a compact umbrella or waterproof jacket for unexpected showers. Comfortable walking shoes are a priority given the amount of ground most visitors cover.

December is a reasonable time to visit Koh Samui. Expect 14 rainy days, so pack a light rain layer for flexibility. Average temperatures of 25°C make outdoor exploration comfortable during the dry periods. With 10 daily sunshine hours, there are reliable windows of good weather to plan outdoor activities around, even if the month is not the driest on the calendar.

The average high temperature in Koh Samui in December is 25°C (77°F), and the average low is 23°C (73°F). The mean daily temperature is approximately 24°C (75°F). The day-to-night range of 2°C is narrow, typical of coastal or maritime cities. These are 30-year climate normals based on the 1991 to 2020 reference period; individual years will vary, particularly in transitional months like spring and autumn.

The best month to visit Koh Samui is generally February. February offers the most sunshine at 11 hours per day and only 6 rainy days. Average temperatures reach 25°C, making it comfortable for sightseeing, outdoor dining, and exploring the city. If your travel dates are flexible, planning your trip around February gives you the best chance of dry, bright weather.

December is shoulder or low season in Koh Samui, meaning fewer tourists and generally lower prices than peak months. With 10 sunshine hours and 14 rainy days, the weather is less of a draw for mass tourism. This is an advantage for travellers who prefer a quieter, more relaxed experience with shorter queues and easier accommodation availability.

In December, Koh Samui suits a range of activities thanks to mild temperatures around 25°C. Mix of indoor and outdoor activities works well given the moderate chance of rain. Top options include exploring historic neighbourhoods, visiting museums and galleries, local food markets, and day trips to surrounding areas. With 10 hours of sunshine, parks and waterfront walks are particularly enjoyable.

December ranks 7th sunniest of the year in Koh Samui, with an average 10 daily sunshine hours. The driest months are February, March, and January. April is the hottest month (27°C avg high); January is the coolest (25°C). From here, temperatures fall 0°C into January. Compared to last month (November: 25°C high, 22 rain days), December is similarly warm and drier. December sits in the middle of the annual sunshine ranking for Koh Samui, offering a reasonable balance of good weather and manageable crowds.

Year-Round Climate

Month	High	Low	Rain Days	Sun	Details
January	25°C	23°C	11	10h	View
February	25°C	23°C	6	11h	View
March	26°C	24°C	10	11h	View
April	27°C	24°C	12	11h	View
May	27°C	24°C	22	10h	View
June	27°C	24°C	19	10h	View
July	27°C	24°C	18	9h	View
August	27°C	24°C	18	9h	View
September	26°C	23°C	22	9h	View
October	25°C	23°C	26	9h	View
November	25°C	23°C	22	9h	View
December	25°C	23°C	14	10h	View

Other Months in Koh Samui

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Plan Your Trip to Koh Samui

Best Time to Visit Koh Samui Koh Samui vs Bangkok in December Koh Samui vs Penang in December

Nearby Destinations with Similar Weather

These cities are within 500 km and experience broadly comparable weather conditions during the same calendar month, making them practical standalone alternatives or worthwhile additions to a longer regional itinerary.

Bangkok🇹🇭 Thailand475 km away

31°C21°C low

Penang🇲🇾 Malaysia457 km away

29°C25°C low

Phuket🇹🇭 Thailand254 km away

28°C25°C low

Phu Quoc🇻🇳 Vietnam443 km away

28°C25°C low

Data Sources for Koh Samui

Koh Samui on Wikipedia Open-Meteo Climate API NOAA National Centers UK Met Office WMO GeoNames

Climate normals represent 30-year averages (1991-2020). Individual years may vary.