Weather in Siem Reap in January

A good month. January works. It is not the peak, but nothing about it fights you. Highs average 33.9 °C, lows 21 °C, and rain falls on 3 days — nothing in the month is working against you.

January ranks 3 of 12 in Siem Reap. Only December scores clearly higher, and the difference is small enough to be settled by price rather than weather.

Rain falls on only 3 days, so an itinerary with no wet-weather fallback is a reasonable risk. Pack for 33.9 °C days and 21 °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: 11 days clear 35 °C, so a serious heatwave is normal rather than notable. Across the twenty years measured, the hottest January day reached 37.8 °C and the coldest night fell to 12.6 °C.

This is the volatile part. January rainfall has ranged from 0 mm to 45 mm across the twenty years measured — a 45 mm spread around an average of 12 mm. The average is real but almost no individual January looks like it, so treat the figure as the middle of a wide range rather than a forecast.

Wind is light at 5.4 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 57%.

How January sits in the year

Temperatures hold steady either side: 32.5 °C in December, 33.9 here, 35.9 in February. Nothing about the timing within the month matters much.

Daylight in January

Siem Reap sits close enough to the equator that daylight barely moves all year — 11.4 hours in January, 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

Busy. Popular without being frantic; book the things you care about, improvise the rest.

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

January 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, 2 days less rain. Nakhon Ratchasima is a better bet in January — 3 °C cooler, 1 day less rain.

So: January works, with December the better month by 8 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Siem Reap

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