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Average Weather in September in Ilulissat Greenland

In Ilulissat, the month of September is characterized by rapidly falling daily high temperatures, with daily highs decreasing by 10°F, from 44°F to 35°F over the course of the month, and rarely exceeding 49°F or dropping below 28°F.

Daily low temperatures decrease by 9°F, from 37°F to 28°F, rarely falling below 20°F or exceeding 42°F.

For reference, on July 18, the hottest day of the year, temperatures in Ilulissat typically range from 42°F to 52°F, while on February 27, the coldest day of the year, they range from -3°F to 8°F.

Average High and Low Temperature in September

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

Average Hourly Temperature in September in Ilulissat1815222911223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM4 AM8 AM12 PM4 PM8 PM12 AMAugOctvery coldfreezingcold
The average hourly temperature, color coded into bands: 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 shaded overlays indicate night and civil twilight.

Terskol, Russia (3,553 miles away) is the far-away foreign place with temperatures most similar to Ilulissat (view comparison).

Clouds

The month of September in Ilulissat experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 58% throughout the month.

The clearest day of the month is September 30, with clear, mostly clear, or partly cloudy conditions 43% of the time.

For reference, on January 1, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 76%, while on July 10, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 51%.

Cloud Cover Categories in September

Cloud Cover Categories in September in Ilulissat181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOctSep 142%Sep 142%Sep 3043%Sep 3043%Sep 1141%Sep 1141%Sep 2142%Sep 2142%clearpartly cloudyovercastmostly clearmostly cloudy
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.

Precipitation

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Ilulissat, the chance of a wet day over the course of September is decreasing, starting the month at 20% and ending it at 16%.

For reference, the year's highest daily chance of a wet day is 23% on August 16, and its lowest chance is 6% on January 6.

Over the course of September in Ilulissat, the chance of a day with only rain decreases from 20% to 11%, the chance of a day with mixed snow and rain increases from 0% to 2%, and the chance of a day with only snow increases from 0% to 2%.

Probability of Precipitation in September

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 Ilulissat is decreasing, starting the month at 1.6 inches, when it rarely exceeds 3.4 inches or falls below 0.4 inches, and ending the month at 0.9 inches, when it rarely exceeds 1.9 inches or falls below 0.2 inches.

Average Monthly Rainfall in September

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 liquid-equivalent snowfall.

Snowfall

We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. As with rainfall, we consider the liquid-equivalent snowfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day liquid-equivalent snowfall during September in Ilulissat is essentially constant, remaining about 0.1 inches throughout, and rarely exceeding 0.5 inches or falling below -0.0 inches.

Average Monthly Liquid-Equivalent Snowfall in September

The average liquid-equivalent snowfall (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 rainfall.

Sun

Due to its extreme latitude, Ilulissat experiences polar day (also known as the midnight Sun) during the summer and polar night during the winter. These are periods of time in which the sun is continuously above or below the horizon for more than one day. The precise start and end dates of polar day and night vary from year to year and depend on the precise location and elevation of the observer, and the local topography.

Neither polar day nor polar night occur during the month of September.

Over the course of September in Ilulissat, the length of the day is very rapidly decreasing. From the start to the end of the month, the length of the day decreases by 4 hours, 1 minute, implying an average daily decrease of 8 minutes, 19 seconds, and weekly decrease of 58 minutes, 11 seconds.

The shortest day of the month is September 30, with 11 hours, 15 minutes of daylight and the longest day is September 1, with 15 hours, 16 minutes of daylight.

Hours of Daylight and Twilight in September

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 earliest sunrise of the month in Ilulissat is 5:45 AM on September 1 and the latest sunrise is 1 hour, 51 minutes later at 7:36 AM on September 30.

The latest sunset is 9:00 PM on September 1 and the earliest sunset is 2 hours, 10 minutes earlier at 6:50 PM on September 30.

Daylight saving time is observed in Ilulissat during 2017, but it neither starts nor ends during September, so the entire month is in daylight saving time.

Sunrise & Sunset with Twilight and Daylight Saving Time in September

Sunrise & Sunset with Twilight and Daylight Saving Time in September in Ilulissat181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930302 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMAugOct5:45 AM5:45 AMSep 19:00 PMSep 19:00 PM7:36 AM7:36 AMSep 306:50 PMSep 306:50 PM6:24 AM6:24 AMSep 118:15 PMSep 118:15 PM7:02 AM7:02 AMSep 217:30 PMSep 217:30 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.

Humidity

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 Ilulissat is essentially constant during September, remaining around 0% throughout.

Humidity Comfort Levels in September

The percentage of time spent at various humidity comfort levels, categorized by dew point: dry < 55°F < comfortable < 60°F < humid < 65°F < muggy < 70°F < oppressive < 75°F < miserable.

Wind

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 Ilulissat is increasing during September, increasing from 7.4 miles per hour to 9.3 miles per hour over the course of the month.

For reference, on November 29, the windiest day of the year, the daily average wind speed is 11.7 miles per hour, while on July 14, the calmest day of the year, the daily average wind speed is 5.5 miles per hour.

Average Wind Speed in September

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 Ilulissat throughout September is predominantly from the east, with a peak proportion of 53% on September 30.

Wind Direction in September

Wind Direction in September in IlulissatSE181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOctsoutheastnorthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Water Temperature

Ilulissat 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 Ilulissat is gradually decreasing during September, falling by 2°F, from 39°F to 37°F, over the course of the month.

Average Water Temperature in September

The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

Growing Season

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).

The growing season in Ilulissat typically lasts for 3.0 months (92 days), from around June 8 to around September 8, rarely starting before May 19 or after July 2, and rarely ending before August 18 or after September 26.

During September in Ilulissat, the chance that a given day is within the growing season is very rapidly decreasing falling from 67% to 5% over the course of the month.

Time Spent in Various Temperature Bands and the Growing Season in September

Time Spent in Various Temperature Bands and the Growing Season in September in Ilulissatgrowing season181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOct67%Sep 167%Sep 1Sep 305%Sep 305%Sep 1142%Sep 1142%Sep 2119%Sep 2119%90%Aug 1890%Aug 18Aug 697%Aug 697%frigidfreezingvery coldcold
The percentage of time spent in various temperature bands: 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 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 Ilulissat are essentially constant during September, remaining around 45°F throughout.

Growing Degree Days in September

The average growing degree days accumulated over the course of September, with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

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 Ilulissat is rapidly decreasing during September, falling by 1.6 kWh, from 3.0 kWh to 1.4 kWh, over the course of the month.

Average Daily Incident Shortwave Solar Energy in September

The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Topography

For the purposes of this report, the geographical coordinates of Ilulissat are 69.217 deg latitude, -51.100 deg longitude, and 0 ft elevation.

The topography within 2 miles of Ilulissat contains only modest variations in elevation, with a maximum elevation change of 394 feet and an average elevation above sea level of 101 feet. Within 10 miles contains only modest variations in elevation (1,654 feet). Within 50 miles contains very significant variations in elevation (4,396 feet).

The area within 2 miles of Ilulissat is covered by water (28%), sparse vegetation (25%), trees (17%), and snow and glaciers (16%), within 10 miles by water (50%) and snow and glaciers (21%), and within 50 miles by water (41%) and snow and glaciers (32%).

Data Sources

This report illustrates the typical weather in Ilulissat year round, 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, Egedesminde, in our network suitable to be used as a proxy for the historical temperature and dew point records of Ilulissat.

At a distance of 91 kilometers from Ilulissat, 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 Ilulissat 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 Tables of the Sun, Moon and Planets , 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 aiports 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.

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.