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September Weather in Phnom Penh Cambodia

Daily high temperatures are around 89°F, rarely falling below 84°F or exceeding 93°F.

Daily low temperatures are around 78°F, rarely falling below 76°F or exceeding 80°F.

For reference, on April 6, the hottest day of the year, temperatures in Phnom Penh typically range from 80°F to 96°F, while on January 1, the coldest day of the year, they range from 73°F to 87°F.

Average High and Low Temperature in September in Phnom Penh

The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on September. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature in September in Phnom Penh

Average Hourly Temperature in September in Phnom PenhSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMAugOctwarmwarmhot
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
The average hourly temperature, color coded into bands. The shaded overlays indicate night and civil twilight.

Maracaibo, Venezuela (10,894 miles away); Alenquer, Brazil (10,904 miles); and São Bento, Brazil (10,287 miles) are the far-away foreign places with temperatures most similar to Phnom Penh (view comparison).

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The month of September in Phnom Penh experiences gradually decreasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy decreasing from 91% to 86%.

The clearest day of the month is September 30, with clear, mostly clear, or partly cloudy conditions 14% of the time.

For reference, on August 20, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 92%, while on February 10, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 49%.

Cloud Cover Categories in September in Phnom Penh

Cloud Cover Categories in September in Phnom PenhSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOctSep 19%Sep 19%Sep 3014%Sep 3014%Sep 1110%Sep 1110%Sep 2112%Sep 2112%partly cloudymostly cloudyovercastmostly clear
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Phnom Penh, the chance of a wet day over the course of September is gradually increasing, starting the month at 62% and ending it at 65%.

For reference, the year's highest daily chance of a wet day is 66% on September 27, and its lowest chance is 6% on January 11.

Probability of Precipitation in September in Phnom Penh

Probability of Precipitation in September in Phnom PenhSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%AugOctSep 2766%Sep 2766%Sep 162%Sep 162%Sep 1161%Sep 1161%rain
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during September in Phnom Penh is essentially constant, remaining about 7.1 inches throughout, and rarely exceeding 11.6 inches or falling below 3.2 inches.

Average Monthly Rainfall in September in Phnom Penh

The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average snowfall.

Over the course of September in Phnom Penh, the length of the day is gradually decreasing. From the start to the end of the month, the length of the day decreases by 18 minutes, implying an average daily decrease of 38 seconds, and weekly decrease of 4 minutes, 25 seconds.

The shortest day of the month is September 30, with 12 hours, 2 minutes of daylight and the longest day is September 1, with 12 hours, 20 minutes of daylight.

Hours of Daylight and Twilight in September in Phnom Penh

Hours of Daylight and Twilight in September in Phnom PenhSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hrAugOctSep 2212 hr, 7 minSep 2212 hr, 7 minnightnightdaydaySep 112 hr, 20 minSep 112 hr, 20 min
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The latest sunrise of the month in Phnom Penh is 5:50 AM on September 1 and the earliest sunrise is 53 seconds earlier at 5:49 AM on September 30.

The latest sunset is 6:10 PM on September 1 and the earliest sunset is 19 minutes earlier at 5:51 PM on September 30.

Daylight saving time is not observed in Phnom Penh during 2024.

For reference, on June 20, the longest day of the year, the Sun rises at 5:37 AM and sets 12 hours, 48 minutes later, at 6:26 PM, while on December 21, the shortest day of the year, it rises at 6:15 AM and sets 11 hours, 27 minutes later, at 5:41 PM.

Sunrise & Sunset with Twilight in September in Phnom Penh

Sunrise & Sunset with Twilight in September in Phnom PenhSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMAugOct5:49 AM5:49 AMSep 305:51 PMSep 305:51 PM5:50 AM5:50 AMSep 16:10 PMSep 16:10 PM5:49 AM5:49 AMSep 116:03 PMSep 116:03 PMSolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day over the course of September. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.

Solar Elevation and Azimuth in September in Phnom Penh

Solar Elevation and Azimuth in September in Phnom PenhSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMAugOct001010202020303040405050506060707080800001010202030303040405050606060707080
northeastsouthwest
Solar elevation and azimuth over the course of September 2024. The black lines are lines of constant solar elevation (the angle of the sun above the horizon, in degrees). The background color fills indicate the azimuth (the compass bearing) of the sun. The lightly tinted areas at the boundaries of the cardinal compass points indicate the implied intermediate directions (northeast, southeast, southwest, and northwest).

The figure below presents a compact representation of key lunar data for September 2024. 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. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

Moon Rise, Set & Phases in September in Phnom Penh

Moon Rise, Set & Phases in September in Phnom PenhSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM12 AM4 AM4 AM8 AM8 AM12 PM12 PM4 PM4 PM8 PM8 PM12 AM12 AMAugOctAug 46:14 PMAug 46:14 PMAug 201:26 AMAug 201:26 AMSep 38:56 AMSep 38:56 AMSep 189:35 AMSep 189:35 AMOct 31:50 AMOct 31:50 AMOct 176:27 PMOct 176:27 PM5:26 AM5:26 AM6:29 PM6:29 PM6:07 PM6:07 PM6:06 AM6:06 AM5:49 AM5:49 AM6:24 PM6:24 PM5:28 PM5:28 PM5:44 AM5:44 AM5:59 AM5:59 AM6:08 PM6:08 PM5:32 PM5:32 PM6:21 AM6:21 AM
The time in which the moon is above the horizon (light blue area), with new moons (dark gray lines) and full moons (blue lines) indicated. The shaded overlays indicate night and civil twilight.
Sep 2024IlluminationMoonriseMoonsetMoonriseMeridian PassingDistance
1
4%4:13 AMENE5:10 PMWNW-10:43 AMN248,303 mi
2
1%5:02 AMENE5:48 PMWNW-11:27 AMN249,878 mi
3
0%5:49 AME6:24 PMW-12:08 PMS251,108 mi
4
1%6:34 AME6:58 PMW-12:47 PMS251,959 mi
5
4%7:18 AME7:32 PMW-1:25 PMS252,376 mi
6
9%8:01 AME8:07 PMW-2:04 PMS252,289 mi
7
15%8:46 AMESE8:43 PMWSW-2:44 PMS251,623 mi
8
23%9:33 AMESE9:22 PMWSW-3:27 PMS250,309 mi
9
32%10:22 AMESE10:05 PMWSW-4:13 PMS248,305 mi
10
42%11:15 AMESE10:52 PMWSW-5:03 PMS245,612 mi
11
50%12:10 PMESE11:45 PMWSW-5:57 PMS242,296 mi
12
63%1:07 PMESE--6:55 PMS238,503 mi
13
73%-12:43 AMWSW2:04 PMESE7:55 PMS234,464 mi
14
83%-1:44 AMWSW3:00 PMESE8:53 PMS230,489 mi
15
91%-2:45 AMWSW3:52 PMESE9:50 PMS226,937 mi
16
97%-3:46 AMWSW4:42 PMESE10:44 PMS224,163 mi
17
100%-4:46 AMWSW5:28 PME11:36 PMS222,465 mi
18
100%-5:44 AMW6:13 PME--
19
99%-6:42 AMW6:59 PME12:27 AMS222,024 mi
20
96%-7:41 AMWNW7:45 PMENE1:18 AMS222,871 mi
21
90%-8:41 AMWNW8:35 PMENE2:11 AMN224,883 mi
22
81%-9:42 AMWNW9:28 PMENE3:06 AMN227,812 mi
23
70%-10:44 AMWNW10:24 PMENE4:04 AMN231,332 mi
24
59%-11:46 AMWNW11:22 PMENE5:04 AMN235,105 mi
25
50%-12:44 PMWNW-6:03 AMN238,824 mi
26
37%12:20 AMENE1:38 PMWNW-7:00 AMN242,257 mi
27
28%1:16 AMENE2:26 PMWNW-7:53 AMN245,251 mi
28
19%2:10 AMENE3:10 PMWNW-8:41 AMN247,729 mi
29
12%3:00 AMENE3:49 PMWNW-9:26 AMN249,672 mi
30
6%3:47 AMENE4:25 PMW-10:07 AMS251,095 mi

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.

The chance that a given day will be muggy in Phnom Penh is essentially constant during September, remaining around 100% throughout.

For reference, on August 9, the muggiest day of the year, there are muggy conditions 100% of the time, while on January 20, the least muggy day of the year, there are muggy conditions 65% of the time.

Humidity Comfort Levels in September in Phnom Penh

Humidity Comfort Levels in September in Phnom PenhSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%AugOctSep 1100%Sep 1100%Sep 30100%Sep 30100%Sep 11100%Sep 11100%Sep 21100%Sep 21100%miserablemiserableoppressiveoppressivemuggymuggy
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The percentage of time spent at various humidity comfort levels, categorized by dew point.

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 Phnom Penh is decreasing during September, decreasing from 6.9 miles per hour to 5.4 miles per hour over the course of the month.

For reference, on August 4, the windiest day of the year, the daily average wind speed is 7.7 miles per hour, while on October 7, the calmest day of the year, the daily average wind speed is 5.2 miles per hour.

Average Wind Speed in September in Phnom Penh

The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The wind direction in Phnom Penh during September is predominantly out of the west from September 1 to September 29 and the south from September 29 to September 30.

Wind Direction in September in Phnom Penh

Wind Direction in September in Phnom PenhWSNSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%20%80%40%60%60%40%80%20%100%0%AugOctwestsouthnortheast
northeastsouthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions, excluding hours in which the mean wind speed is less than 1.0 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

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 Phnom Penh 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 in September in Phnom Penh

Time Spent in Various Temperature Bands and the Growing Season in September in Phnom PenhSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOct100%Sep 16100%Sep 16warmhot
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
The percentage of time spent in various temperature bands. The black line is the percentage chance that a given day is within the growing season.

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.

The average accumulated growing degree days in Phnom Penh are very rapidly increasing during September, increasing by 922°F, from 7,934°F to 8,856°F, over the course of the month.

Growing Degree Days in September in Phnom Penh

Growing Degree Days in September in Phnom PenhSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930307,800°F7,800°F8,000°F8,000°F8,200°F8,200°F8,400°F8,400°F8,600°F8,600°F8,800°F8,800°F9,000°F9,000°FAugOctSep 17,934°FSep 17,934°FSep 308,856°FSep 308,856°FSep 118,258°FSep 118,258°FSep 218,575°FSep 218,575°F
The average growing degree days accumulated over the course of September, with 25th to 75th and 10th to 90th percentile bands.

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 in Phnom Penh is essentially constant during September, remaining within 0.1 kWh of 4.0 kWh throughout.

The lowest average daily incident shortwave solar energy during September is 3.9 kWh on September 19.

Average Daily Incident Shortwave Solar Energy in September in Phnom Penh

Average Daily Incident Shortwave Solar Energy in September in Phnom PenhSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300 kWh0 kWh1 kWh1 kWh2 kWh2 kWh3 kWh3 kWh4 kWh4 kWh5 kWh5 kWh6 kWh6 kWhAugOctSep 193.9 kWhSep 193.9 kWhSep 14.0 kWhSep 14.0 kWhSep 304.0 kWhSep 304.0 kWh
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

For the purposes of this report, the geographical coordinates of Phnom Penh are 11.562 deg latitude, 104.916 deg longitude, and 66 ft elevation.

The topography within 2 miles of Phnom Penh is essentially flat, with a maximum elevation change of 82 feet and an average elevation above sea level of 46 feet. Within 10 miles is essentially flat (112 feet). Within 50 miles contains only modest variations in elevation (2,444 feet).

The area within 2 miles of Phnom Penh is covered by artificial surfaces (85%) and water (10%), within 10 miles by cropland (44%) and artificial surfaces (23%), and within 50 miles by cropland (63%) and trees (11%).

This report illustrates the typical weather in Phnom Penh, 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, Phnom Penh International Airport, in our network suitable to be used as a proxy for the historical temperature and dew point records of Phnom Penh.

At a distance of 8 kilometers from Phnom Penh, 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 Phnom Penh 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.

Other Data

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 © OpenStreetMap contributors.

Disclaimer

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.

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