Average Weather in Siem Reap Cambodia
In Siem Reap, the wet season is oppressive and overcast, the dry season is muggy and partly cloudy, and it is hot year round. Over the course of the year, the temperature typically varies from 70°F to 95°F and is rarely below 64°F or above 102°F.
Based on the beach/pool score, the best time of year to visit Siem Reap for hot-weather activities is from mid November to early March.
The hot season lasts for 2.1 months, from March 13 to May 17, with an average daily high temperature above 93°F. The hottest day of the year is April 18, with an average high of 95°F and low of 81°F.
The cool season lasts for 3.6 months, from September 27 to January 15, with an average daily high temperature below 87°F. The coldest day of the year is January 1, with an average low of 70°F and high of 85°F.
Average High and Low Temperature
The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.
Average Hourly Temperature
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
Juchitán de Zaragoza, Mexico (10,019 miles away); Santarém, Brazil (10,802 miles); and São Luís, Brazil (10,148 miles) are the far-away foreign places with temperatures most similar to Siem Reap (view comparison).
In Siem Reap, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year in Siem Reap begins around November 5 and lasts for 4.7 months, ending around March 28. On February 10, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 55% of the time, and overcast or mostly cloudy 45% of the time.
The cloudier part of the year begins around March 28 and lasts for 7.3 months, ending around November 5. On August 26, the cloudiest day of the year, the sky is overcast or mostly cloudy 92% of the time, and clear, mostly clear, or partly cloudy 8% of the time.
Cloud Cover Categories
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Siem Reap varies very significantly throughout the year.
The wetter season lasts 5.9 months, from April 27 to October 23, with a greater than 37% chance of a given day being a wet day. The chance of a wet day peaks at 72% on September 4.
The drier season lasts 6.1 months, from October 23 to April 27. The smallest chance of a wet day is 2% on December 20.
Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 72% on September 4.
Daily Chance of Precipitation
To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Siem Reap experiences extreme seasonal variation in monthly rainfall.
The rainy period of the year lasts for 9.5 months, from February 15 to November 29, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around September 8, with an average total accumulation of 8.7 inches.
The rainless period of the year lasts for 2.5 months, from November 29 to February 15. The least rain falls around December 24, with an average total accumulation of 0.1 inches.
Average Monthly Rainfall
The length of the day in Siem Reap varies over the course of the year. In 2021, the shortest day is December 21, with 11 hours, 20 minutes of daylight; the longest day is June 21, with 12 hours, 55 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:36 AM on June 1, and the latest sunrise is 55 minutes later at 6:31 AM on January 23. The earliest sunset is at 5:34 PM on November 20, and the latest sunset is 1 hour, 2 minutes later at 6:35 PM on July 9.
Daylight saving time (DST) is not observed in Siem Reap during 2021.
Sunrise & Sunset with Twilight
The figure below presents a compact representation of key lunar data for 2021. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases.
Moon Rise, Set & Phases
We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.
Siem Reap experiences significant seasonal variation in the perceived humidity.
The muggier period of the year lasts for 10 months, from February 9 to December 20, during which time the comfort level is muggy, oppressive, or miserable at least 66% of the time. The muggiest day of the year is August 16, with muggy conditions 100% of the time.
The least muggy day of the year is January 21, with muggy conditions 55% of the time.
Humidity Comfort Levels
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.
The average hourly wind speed in Siem Reap experiences mild seasonal variation over the course of the year.
The windier part of the year lasts for 3.2 months, from May 31 to September 6, with average wind speeds of more than 5.6 miles per hour. The windiest day of the year is August 6, with an average hourly wind speed of 6.8 miles per hour.
The calmer time of year lasts for 8.8 months, from September 6 to May 31. The calmest day of the year is October 6, with an average hourly wind speed of 4.5 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Siem Reap varies throughout the year.
The wind is most often from the south for 2.3 months, from February 24 to May 1, with a peak percentage of 44% on April 28. The wind is most often from the west for 5.3 months, from May 1 to October 9, with a peak percentage of 76% on August 10. The wind is most often from the north for 2.7 months, from October 9 to January 1, with a peak percentage of 59% on December 1.
Best Time of Year to Visit
To characterize how pleasant the weather is in Siem Reap throughout the year, we compute two travel scores.
The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Siem Reap for general outdoor tourist activities is from early December to early February, with a peak score in the first week of January.
The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Siem Reap for hot-weather activities is from mid November to early March, with a peak score in the second week of February.
For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.
Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.
Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.
Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.
Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.
Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).
Temperatures in Siem Reap are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.
Time Spent in Various Temperature Bands and the Growing Season
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.
Growing Degree Days
This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.
The average daily incident shortwave solar energy experiences some seasonal variation over the course of the year.
The brighter period of the year lasts for 2.2 months, from January 22 to March 29, with an average daily incident shortwave energy per square meter above 5.6 kWh. The brightest day of the year is March 1, with an average of 6.0 kWh.
The darker period of the year lasts for 4.2 months, from June 6 to October 12, with an average daily incident shortwave energy per square meter below 4.4 kWh. The darkest day of the year is September 18, with an average of 4.0 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Siem Reap are 13.362 deg latitude, 103.861 deg longitude, and 59 ft elevation.
The topography within 2 miles of Siem Reap is essentially flat, with a maximum elevation change of 69 feet and an average elevation above sea level of 58 feet. Within 10 miles is essentially flat (420 feet). Within 50 miles contains only modest variations in elevation (1,683 feet).
The area within 2 miles of Siem Reap is covered by artificial surfaces (63%) and cropland (31%), within 10 miles by cropland (64%), and within 50 miles by cropland (35%) and trees (33%).
This report illustrates the typical weather in Siem Reap, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.
Temperature and Dew Point
There is only a single weather station, Siem Reap International Airport, in our network suitable to be used as a proxy for the historical temperature and dew point records of Siem Reap.
At a distance of 8 kilometers from Siem Reap, closer than our threshold of 150 kilometers, this station is deemed sufficiently nearby to be relied upon as our primary source for temperature and dew point records.
The station records are corrected for the elevation difference between the station and Siem Reap according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
Please note that the station records themselves may additionally have been back-filled using other nearby stations or the MERRA-2 reanalysis.
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , by Jean Meeus.
All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.
Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.
Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.
Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .
Time zones for airports and weather stations are provided by AskGeo.com .
Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.
The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.
We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.
We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.