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September Weather in Ailuk Marshall Islands

Daily high temperatures are around 83°F, rarely falling below 82°F or exceeding 84°F.

Daily low temperatures are around 82°F, rarely falling below 80°F or exceeding 83°F.

For reference, on October 12, the hottest day of the year, temperatures in Ailuk typically range from 82°F to 83°F, while on February 11, the coldest day of the year, they range from 80°F to 81°F.

Average High and Low Temperature in September in Ailuk

Average High and Low Temperature in September in AilukSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303080°F80°F81°F81°F82°F82°F83°F83°F84°F84°F85°F85°F86°F86°F87°F87°F88°F88°F89°F89°F90°F90°F91°F91°F92°F92°FAugOctSep 183°FSep 183°F82°F82°FSep 3083°FSep 3083°F82°F82°FSep 1183°FSep 1183°F82°F82°FSep 2183°FSep 2183°F82°F82°F
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 Ailuk

Average Hourly Temperature in September in AilukSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 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 AMAugOctwarm
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.

San Andrés, Colombia (7,281 miles away) is the far-away foreign place with temperatures most similar to Ailuk (view comparison).

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The month of September in Ailuk experiences gradually increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 78% to 82%.

The clearest day of the month is September 1, with clear, mostly clear, or partly cloudy conditions 22% of the time.

For reference, on October 14, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 83%, while on March 7, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 30%.

Cloud Cover Categories in September in Ailuk

Cloud Cover Categories in September in AilukSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOctSep 122%Sep 122%Sep 3018%Sep 3018%Sep 1121%Sep 1121%Sep 2120%Sep 2120%mostly clearpartly cloudymostly cloudyovercastclear
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 Ailuk, the chance of a wet day over the course of September is very rapidly increasing, starting the month at 48% and ending it at 57%.

For reference, the year's highest daily chance of a wet day is 58% on October 3, and its lowest chance is 6% on February 7.

Probability of Precipitation in September in Ailuk

Probability of Precipitation in September in AilukSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%0%5%5%10%10%15%15%20%20%25%25%30%30%35%35%40%40%45%45%50%50%55%55%60%60%AugOctSep 148%Sep 148%Sep 3057%Sep 3057%Sep 1150%Sep 1150%Sep 2155%Sep 2155%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 Ailuk is rapidly increasing, starting the month at 4.1 inches, when it rarely exceeds 7.8 inches or falls below 1.2 inches, and ending the month at 5.3 inches, when it rarely exceeds 8.2 inches or falls below 2.8 inches.

Average Monthly Rainfall in September in Ailuk

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 Ailuk, the length of the day is gradually decreasing. From the start to the end of the month, the length of the day decreases by 16 minutes, implying an average daily decrease of 33 seconds, and weekly decrease of 3 minutes, 53 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, 19 minutes of daylight.

Hours of Daylight and Twilight in September in Ailuk

Hours of Daylight and Twilight in September in AilukSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hrAugOctSep 2312 hr, 7 minSep 2312 hr, 7 minnightnightdaydaySep 112 hr, 19 minSep 112 hr, 19 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 Ailuk is 6:30 AM on September 1 and the earliest sunrise is 1 minute, 58 seconds earlier at 6:28 AM on September 30.

The latest sunset is 6:49 PM on September 1 and the earliest sunset is 18 minutes earlier at 6:31 PM on September 30.

Daylight saving time is not observed in Ailuk during 2024.

For reference, on June 20, the longest day of the year, the Sun rises at 6:19 AM and sets 12 hours, 43 minutes later, at 7:03 PM, while on December 21, the shortest day of the year, it rises at 6:52 AM and sets 11 hours, 32 minutes later, at 6:24 PM.

Sunrise & Sunset with Twilight in September in Ailuk

Sunrise & Sunset with Twilight in September in AilukSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930302 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMAugOct6:28 AM6:28 AMSep 306:31 PMSep 306:31 PM6:30 AM6:30 AMSep 16:49 PMSep 16:49 PM6:30 AM6:30 AMSep 116:43 PMSep 116:43 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 Ailuk

Solar Elevation and Azimuth in September in AilukSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 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 Ailuk

Moon Rise, Set & Phases in September in AilukSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM12 AM4 AM4 AM8 AM8 AM12 PM12 PM4 PM4 PM8 PM8 PM12 AM12 AMAugOctAug 411:14 PMAug 411:14 PMAug 206:26 AMAug 206:26 AMSep 31:56 PMSep 31:56 PMSep 182:35 PMSep 182:35 PMOct 36:50 AMOct 36:50 AMOct 1711:27 PMOct 1711:27 PM5:58 AM5:58 AM6:59 PM6:59 PM6:35 PM6:35 PM6:37 AM6:37 AM6:22 AM6:22 AM6:57 PM6:57 PM6:45 PM6:45 PM7:11 AM7:11 AM6:31 AM6:31 AM6:42 PM6:42 PM6:04 PM6:04 PM6:48 AM6:48 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%4:46 AMENE5:40 PMWNW-11:15 AMN247,983 mi
2
1%5:35 AMENE6:20 PMWNW-11:59 AMN249,618 mi
3
0%6:22 AMENE6:57 PMW-12:40 PMS250,913 mi
4
1%7:06 AME7:32 PMW-1:20 PMS251,835 mi
5
4%7:49 AME8:06 PMW-1:58 PMS252,336 mi
6
8%8:32 AME8:41 PMW-2:37 PMS252,345 mi
7
14%9:16 AMESE9:17 PMWSW-3:16 PMS251,789 mi
8
22%10:02 AMESE9:56 PMWSW-3:58 PMS250,597 mi
9
30%10:50 AMESE10:39 PMWSW-4:44 PMS248,718 mi
10
40%11:42 AMESE11:26 PMWSW-5:33 PMS246,148 mi
11
50%12:36 PMESE--6:27 PMS242,936 mi
12
61%-12:18 AMWSW1:33 PMESE7:24 PMS239,215 mi
13
71%-1:15 AMWSW2:31 PMESE8:24 PMS235,199 mi
14
81%-2:15 AMWSW3:27 PMESE9:23 PMS231,187 mi
15
90%-3:17 AMWSW4:21 PMESE10:20 PMS227,531 mi
16
96%-4:17 AMWSW5:11 PMESE11:14 PMS224,593 mi
17
98%-5:16 AMWSW5:59 PME--
18
100%-6:14 AMW6:45 PME12:07 AMS222,683 mi
19
100%-7:11 AMW7:31 PME12:58 AMS222,007 mi
20
97%-8:09 AMW8:18 PMENE1:49 AMS222,626 mi
21
91%-9:08 AMWNW9:07 PMENE2:41 AMN224,443 mi
22
82%-10:08 AMWNW10:00 PMENE3:36 AMN227,229 mi
23
72%-11:10 AMWNW10:56 PMENE4:34 AMN230,668 mi
24
61%-12:12 PMWNW11:54 PMENE5:33 AMN234,419 mi
25
50%-1:11 PMWNW-6:33 AMN238,168 mi
26
39%12:53 AMENE2:05 PMWNW-7:30 AMN241,666 mi
27
29%1:49 AMENE2:55 PMWNW-8:24 AMN244,747 mi
28
20%2:43 AMENE3:40 PMWNW-9:13 AMN247,321 mi
29
13%3:33 AMENE4:20 PMWNW-9:58 AMN249,360 mi
30
7%4:20 AMENE4:58 PMW-10:40 AMN250,875 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 Ailuk is essentially constant during September, remaining around 100% throughout.

For reference, on January 1, the muggiest day of the year, there are muggy conditions 100% of the time, while on January 6, the least muggy day of the year, there are muggy conditions 100% of the time.

Humidity Comfort Levels in September in Ailuk

Humidity Comfort Levels in September in AilukSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%AugOctSep 16100%Sep 16100%Sep 1100%Sep 1100%Sep 30100%Sep 30100%miserablemiserableoppressiveoppressive
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 Ailuk is essentially constant during September, remaining within 0.3 miles per hour of 11.2 miles per hour throughout.

For reference, on December 26, the windiest day of the year, the daily average wind speed is 19.0 miles per hour, while on September 5, the calmest day of the year, the daily average wind speed is 10.9 miles per hour.

The lowest daily average wind speed during September is 10.9 miles per hour on September 5.

Average Wind Speed in September in Ailuk

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

The hourly average wind direction in Ailuk throughout September is predominantly from the east, with a peak proportion of 79% on September 29.

Wind Direction in September in Ailuk

Wind Direction in September in AilukSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%20%80%40%60%60%40%80%20%100%0%AugOcteastsouthwestnorth
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).

Ailuk is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average surface water temperature in Ailuk is essentially constant during September, remaining around 84°F throughout.

The highest average surface water temperature during September is 84°F on September 13.

Average Water Temperature in September in Ailuk

Average Water Temperature in September in AilukSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303082.0°F82.0°F82.5°F82.5°F83.0°F83.0°F83.5°F83.5°F84.0°F84.0°F84.5°F84.5°F85.0°F85.0°F85.5°F85.5°F86.0°F86.0°FAugOctSep 1384°FSep 1384°FSep 184°FSep 184°FSep 3084°FSep 3084°FSep 2184°FSep 2184°F
The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

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 Ailuk 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 Ailuk

Time Spent in Various Temperature Bands and the Growing Season in September in AilukSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%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 16warm
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 Ailuk are very rapidly increasing during September, increasing by 929°F, from 7,632°F to 8,561°F, over the course of the month.

Growing Degree Days in September in Ailuk

Growing Degree Days in September in AilukSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930307,400°F7,400°F7,600°F7,600°F7,800°F7,800°F8,000°F8,000°F8,200°F8,200°F8,400°F8,400°F8,600°F8,600°FAugOctSep 17,632°FSep 17,632°FSep 308,561°FSep 308,561°FSep 117,949°FSep 117,949°FSep 218,273°FSep 218,273°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 Ailuk is essentially constant during September, remaining within 0.2 kWh of 4.6 kWh throughout.

Average Daily Incident Shortwave Solar Energy in September in Ailuk

Average Daily Incident Shortwave Solar Energy in September in AilukSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300 kWh0 kWh1 kWh1 kWh2 kWh2 kWh3 kWh3 kWh4 kWh4 kWh5 kWh5 kWh6 kWh6 kWh7 kWh7 kWhAugOctSep 14.8 kWhSep 14.8 kWhSep 304.5 kWhSep 304.5 kWhSep 114.7 kWhSep 114.7 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 Ailuk are 10.220 deg latitude, 169.980 deg longitude, and 33 ft elevation.

The topography within 2 miles of Ailuk is essentially flat, with a maximum elevation change of 46 feet and an average elevation above sea level of 1 foot. Within 10 miles is also essentially flat (52 feet). Within 50 miles is also essentially flat (62 feet).

The area within 2 miles of Ailuk is covered by water (100%), within 10 miles by water (100%), and within 50 miles by water (100%).

This report illustrates the typical weather in Ailuk, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Ailuk is further than 200 kilometers from the nearest reliable weather station, so the weather-related data on this page were taken entirely from NASA's MERRA-2 satellite-era reanalysis . 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.

The temperature and dew point estimates are corrected for the difference between the reference elevation of the MERRA-2 grid cell and the elevation of Ailuk, according to the International Standard Atmosphere .

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.

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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