Bangkok in December: what to expect

December sits in Bangkok's cool season, the window from November to February when the monsoon has gone and the humidity drops. Expect daytime highs near 31 °C and nights around 21 °C, with the odd cooler morning in the low 20s that locals treat as cold. Rain is uncommon: a brief shower is possible but rarely lasts or blocks a day.

This is also the month with the most comfortable evenings. Outdoor plans — a river ferry at dusk, a night market, a rooftop bar — work without the sweat that makes April and May hard. Air quality is usually better than the February–April haze period, though still worth checking on still days.

Daylight runs about 11 hours, with sunrise near 06:30 and sunset near 18:00, so plan temple and market visits in the morning and leave evenings for food and the river.

December splits into two halves. The first three weeks are busy but manageable: hotel rates are high-season normal, and you can still book good mid-range rooms a few weeks out. From about 20 December, when Christmas and New Year travellers arrive together with Thai holidaymakers, the city fills. That stretch to 5 January carries the year's highest room rates, and flights into Suvarnabhumi and Don Mueang are at their fullest.

Practical effects: book hotels four to eight weeks ahead for the late-December window, and book intercity buses, trains and domestic flights for 30 December and 2 January early — those are the two heaviest travel days of the Thai year. Restaurants in popular areas take reservations; walk-in waits at riverside and Sukhumvit places get long after 19:00.

If your dates are flexible, the first half of the month gives you the same weather for noticeably less money.

The month's anchor is New Year. Bangkok marks 31 December with countdown events and fireworks, mostly around the river and the big malls, and roads near those areas close early in the evening. The city also runs a run-up of light displays and markets through the second half of the month.

5 December is a royal and memorial day, a public holiday with ceremonies and a subdued tone in some areas; some government sites and a few businesses adjust hours. Alcohol sales rules can change on religious and election days — check locally before planning a big night.

Elsewhere in Thailand, the cool season brings the country's biggest crowds to Chiang Mai and the Andaman coast, so domestic flights and island ferries are busy all month.

December is the month to spend time outdoors in Bangkok. The old city's temple cluster — Wat Phra Kaew, Wat Pho and Wat Arun — is at its most walkable, though it is also at its most crowded, so arrive at opening. The Chao Phraya river ferries are a cheap way to move between sights and are pleasant in the cool air.

For markets, Chatuchak weekend market and the riverside night markets are comfortable in December in a way they are not in April. Rooftop bars and riverside restaurants are worth booking for sunset. Day trips to Ayutthaya and Kanchanaburi work well now: dry roads, mild temperatures and no flooding.

If you want a beach add-on, the Andaman coast (Phuket, Krabi) is in its best window. The Gulf islands (Samui, Phangan, Tao) are still wet in early December and can see ferry cancellations — the parent Thailand guide flags this as the one regional exception in an otherwise dry month.

Pack for warm days and mild evenings. Light cotton and linen, comfortable walking shoes for temple floors and long market walks, and one light layer for cool mornings, over-air-conditioned malls and the occasional breezy boat. A compact umbrella is optional in December but useful if a shower passes.

Temple visits need shoulders and knees covered, so bring a scarf or light long-sleeve top. Sunscreen and a hat matter more than you would expect for a 31 °C day in the sun. If your trip runs into New Year, book transport before you fly and keep a printed or offline copy of tickets.

November is the start of the cool season: slightly warmer and wetter than December, with medium crowds and prices and the Loy Krathong festival. It is a good shoulder option if December dates are too expensive.

January is the other peak month: dry, cool and busy, with prices staying high into the first week. February stays dry and warms up, and the northern haze season begins late in the month — Bangkok itself remains fine.