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Average Weather in September at Deadhorse Airport Alaska, United States

At Deadhorse Airport, the month of September is characterized by rapidly falling daily high temperatures, with daily highs decreasing by 13°F, from 45°F to 32°F over the course of the month, and rarely exceeding 58°F or dropping below 23°F.

Daily low temperatures decrease by 11°F, from 35°F to 24°F, rarely falling below 13°F or exceeding 41°F.

For reference, on July 28, the hottest day of the year, temperatures at Deadhorse Airport typically range from 41°F to 56°F, while on February 9, the coldest day of the year, they range from -22°F to -9°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 at Deadhorse Airport1815222911223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM4 AM8 AM12 PM4 PM8 PM12 AMAugOctvery coldfrigidfreezingcold
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 (4,584 miles away); Tosontsengel, Mongolia (3,579 miles); and McMurdo Station, Antarctica (10,401 miles) are the far-away foreign places with temperatures most similar to Deadhorse Airport (view comparison).

Clouds

The month of September at Deadhorse Airport experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 72% throughout the month.

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

For reference, on January 21, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 88%, while on June 27, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 36%.

Cloud Cover Categories in September

Cloud Cover Categories in September at Deadhorse Airport181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOctSep 127%Sep 127%Sep 3030%Sep 3030%Sep 1128%Sep 1128%Sep 2129%Sep 2129%mostly clearmostly cloudyovercastclearpartly 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. At Deadhorse Airport, the chance of a wet day over the course of September is very rapidly decreasing, starting the month at 19% and ending it at 11%.

For reference, the year's highest daily chance of a wet day is 23% on August 15, and its lowest chance is 2% on April 1.

Over the course of September at Deadhorse Airport, the chance of a day with only rain decreases from 17% to 3%, the chance of a day with mixed snow and rain remains an essentially constant 2% throughout, and the chance of a day with only snow increases from 1% to 5%.

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 at Deadhorse Airport is decreasing, starting the month at 0.9 inches, when it rarely exceeds 1.8 inches or falls below 0.2 inches, and ending the month at 0.3 inches, when it rarely exceeds 0.7 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 at Deadhorse Airport is essentially constant, remaining about 0.2 inches throughout, and rarely exceeding 0.6 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, Deadhorse Airport 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 at Deadhorse Airport, 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, 15 minutes, implying an average daily decrease of 8 minutes, 47 seconds, and weekly decrease of 1 hour, 1 minute, 27 seconds.

The shortest day of the month is September 30, with 11 hours, 10 minutes of daylight and the longest day is September 1, with 15 hours, 24 minutes of daylight.

Hours of Daylight and Twilight in September

Hours of Daylight and Twilight in September at Deadhorse Airport181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hrAugOctSep 2212 hr, 19 minSep 2212 hr, 19 minSep 115 hr, 24 minSep 115 hr, 24 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 earliest sunrise of the month at Deadhorse Airport is 6:10 AM on September 1 and the latest sunrise is 1 hour, 58 minutes later at 8:07 AM on September 30.

The latest sunset is 9:34 PM on September 1 and the earliest sunset is 2 hours, 17 minutes earlier at 7:17 PM on September 30.

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

Sunrise & Sunset with Twilight in September

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 at Deadhorse Airport 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 at Deadhorse Airport is increasing during September, increasing from 9.9 miles per hour to 11.4 miles per hour over the course of the month.

For reference, on January 12, the windiest day of the year, the daily average wind speed is 12.6 miles per hour, while on July 29, the calmest day of the year, the daily average wind speed is 9.2 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 at Deadhorse Airport throughout September is predominantly from the east, with a peak proportion of 46% on September 29.

Wind Direction in September

Wind Direction in September at Deadhorse Airport181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOcteastwestnorthsouth
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

Deadhorse Airport 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 at Deadhorse Airport is gradually decreasing during September, falling by 3°F, from 35°F to 32°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 at Deadhorse Airport typically lasts for 1.9 months (57 days), from around June 23 to around August 20, rarely starting before June 4, or ending after September 10.

The month of September at Deadhorse Airport is more likely than not fully outside of the growing season, with the chance that a given day is in the growing season rapidly decreasing from 22% to 0% 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 at Deadhorse Airportgrowing season181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%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 300%Sep 300%Sep 119%Sep 119%Sep 213%Sep 213%50%Aug 2050%Aug 20frigidfreezingvery coldcoldcool
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 at Deadhorse Airport are essentially constant during September, remaining within 2°F of 138°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 at Deadhorse Airport is decreasing during September, falling by 1.3 kWh, from 2.4 kWh to 1.1 kWh, over the course of the month.

Average Daily Incident Shortwave Solar Energy in September

Average Daily Incident Shortwave Solar Energy in September at Deadhorse Airport181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300.0 kWh0.5 kWh1.0 kWh1.5 kWh2.0 kWh2.5 kWh3.0 kWh3.5 kWh4.0 kWh4.5 kWh5.0 kWh5.5 kWh6.0 kWhAugOctSep 12.4 kWhSep 12.4 kWhSep 301.1 kWhSep 301.1 kWhSep 111.9 kWhSep 111.9 kWhSep 211.5 kWhSep 211.5 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.

Topography

For the purposes of this report, the geographical coordinates of Deadhorse Airport are 70.195 deg latitude, -148.465 deg longitude, and 49 ft elevation.

The topography within 2 miles of Deadhorse Airport is essentially flat, with a maximum elevation change of 46 feet and an average elevation above sea level of 51 feet. Within 10 miles is essentially flat (141 feet). Within 50 miles contains only modest variations in elevation (1,030 feet).

The area within 2 miles of Deadhorse Airport is covered by sparse vegetation (36%), grassland (31%), water (14%), and herbaceous vegetation (14%), within 10 miles by grassland (41%) and sparse vegetation (32%), and within 50 miles by water (39%) and grassland (36%).

Data Sources

This report illustrates the typical weather at Deadhorse Airport 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

Deadhorse Airport has a weather station that reported reliably enough during the analysis period that we have included it in our network. When available, historical temperature and dew point measurements are taken directly from this weather station. These records are obtained from NOAA's Integrated Surface Hourly data set, falling back on ICAO METAR records as required.

In the case of missing or erroneous measurements from this station, we fall back on records from nearby stations, adjusted according to typical seasonal and diurnal intra-station differences. For a given day of the year and hour of the day, the fallback station is selected to minimize the prediction error over the years for which there are measurements for both stations.

The stations on which we may fall back are Nuiqsut Airport and Barter Island LRRS Airport.

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.