Weather in Siem Reap in December

A good month. December is a solid month to be in Siem Reap. Highs average 32.5 °C, lows 20.6 °C, and rain falls on 2 days — nothing in the month is working against you.

December is the highest-scoring month of the twelve. The nearest rival is November, and the month at the other end of the year is May.

Rain falls on only 2 days, so an itinerary with no wet-weather fallback is a reasonable risk. Pack for 32.5 °C days and 20.6 °C nights; the spread matters more here than any single number.

What the averages hide

Averages flatten a month, and this one hides a few things: 5 days clear 35 °C, so a serious heatwave is normal rather than notable. Across the twenty years measured, the hottest December day reached 38.4 °C and the coldest night fell to 12.8 °C.

December is dependably dry, and that reliability is the point: across the twenty years measured, the wettest December on record still only managed 27 mm, and the driest managed 0 mm. There is no meaningful variability to plan around, which makes this one of the few months anywhere that you can build a fixed outdoor itinerary against without a fallback. The wettest single day in twenty years of Decembers brought 15 mm. Rain simply is not the variable that decides this trip — heat, crowds and cost are.

Wind is light at 6.1 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 65%.

How December sits in the year

Temperatures hold steady either side: 31.7 °C in November, 32.5 here, 33.9 in January. Nothing about the timing within the month matters much. Rain has already shifted: 6 days fewer than November had.

Daylight in December

Siem Reap sits close enough to the equator that daylight barely moves all year — 11.3 hours in December, against a range of just 1.6 hours across the whole calendar. Sunrise and sunset land at roughly the same time whenever you come.

An inland climate

Despite being inland, the year stays fairly even: 16.1 °C between the year's warmest afternoons and coldest nights.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

December in Siem Reap versus nearby

If Siem Reap is one option among several, the nearby comparison is worth making. Ubon Ratchathani is close enough to be a coin toss — within a degree on temperature, 1 day less rain. Nakhon Ratchasima is a better bet in December — 3.3 °C cooler, 1 day less rain.

So: December is the answer for Siem Reap. If it is booked out or priced out, November is the next best thing at 7 points behind, and May is the month to keep off the shortlist.

Every month in Siem Reap

See all twelve months in Siem Reap, or where else to go in December.