Average Weather in Anchorage Alaska, United States
In Anchorage, the temperature typically varies from 13°F to 68°F over the course of the year, and is rarely below -8°F or above 75°F.
The warm season lasts for 3.7 months, from May 19 to September 11, with an average daily high temperature above 59°F. The hottest day of the year is July 20, with an average high of 68°F and low of 55°F.
The cold season lasts for 4.0 months, from November 5 to March 5, with an average daily high temperature below 32°F. The coldest day of the year is January 17, with an average low of 13°F and high of 23°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
The length of the day in Anchorage varies extremely over the course of the year. In 2017, the shortest day is December 21, with 5 hours, 27 minutes of daylight; the longest day is June 21, with 19 hours, 23 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 4:19 AM on June 19, and the latest sunrise is 5 hours, 56 minutes later at 10:15 AM on December 26. The earliest sunset is at 3:40 PM on December 16, and the latest sunset is 8 hours, 3 minutes later at 11:42 PM on June 22.
Daylight saving time (DST) is observed in Anchorage during 2017, starting in the spring on March 12, lasting 7.8 months, and ending in the fall on November 5.
Sunrise & Sunset with Twilight and Daylight Saving Time
In Anchorage, the average percentage of the sky covered by clouds experiences mild seasonal variation over the course of the year.
The clearer part of the year in Anchorage begins around February 13 and lasts for 2.3 months, ending around April 22. On March 16, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 48% of the time, and overcast or mostly cloudy 52% of the time.
The cloudier part of the year begins around April 22 and lasts for 9.7 months, ending around February 13. On December 18, the cloudiest day of the year, the sky is overcast or mostly cloudy 63% of the time, and clear, mostly clear, or partly cloudy 37% of the time.
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Anchorage varies throughout the year.
The wetter season lasts 3.6 months, from July 10 to October 28, with a greater than 26% chance of a given day being a wet day. The chance of a wet day peaks at 39% on September 27.
The drier season lasts 8.4 months, from October 28 to July 10. The smallest chance of a wet day is 13% on March 28.
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 in Anchorage changes throughout the year.
Rain alone is the most common for 7.6 months, from March 20 to November 6. The highest chance of a day with rain alone is 38% on September 23.
Snow alone is the most common for 4.4 months, from November 6 to March 20. The highest chance of a day with snow alone is 17% on December 15.
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 in the year. Anchorage experiences significant seasonal variation in monthly rainfall.
The rainy period of the year lasts for 7.5 months, from April 12 to November 28, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around September 5, with an average total accumulation of 3.1 inches.
The rainless period of the year lasts for 4.5 months, from November 28 to April 12. The least rain falls around March 14, with and average total accumulation of 0.3 inches.
Average Monthly Rainfall
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. Colder, drier snow tends to be on the higher end of that range and warmer, wetter snow on the lower end.
As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day in the year. Anchorage experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 6.4 months, from October 2 to April 14, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around December 12, with an average total liquid-equivalent accumulation of 1.0 inches.
The snowless period of the year lasts for 5.6 months, from April 14 to October 2. The least snow falls around July 18, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
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 perceived humidity level in Anchorage, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, remaining a virtually constant 0% throughout.
Humidity Comfort Levels
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 Anchorage experiences mildly seasonal variation over the course of the year.
The windier part of the year lasts for 7.1 months, from September 14 to April 17, with average wind speeds of more than 2.9 miles per hour. The windiest day of the year is January 8, with an average hourly wind speed of 3.5 miles per hour.
The calmer time of year lasts for 4.9 months, from April 17 to September 14. The calmest day of the year is July 6, with an average hourly wind speed of 2.3 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Anchorage varies throughout the year.
The wind is most often from the south for 4.0 months, from May 9 to September 10, with a peak percentage of 60% on July 3. The wind is most often from the east for 3.9 weeks, from September 10 to October 7 and for 5.3 months, from November 30 to May 9, with a peak percentage of 49% on February 11. The wind is most often from the north for 1.8 months, from October 7 to November 30, with a peak percentage of 50% on November 6.
Anchorage 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 water temperature experiences significant seasonal variation over the course of the year.
The time of year with warmer water lasts for 2.8 months, from June 30 to September 24, with an average temperature above 50°F. The day of the year with the warmest water is August 14, with an average temperature of 55°F.
The time of year with cooler water lasts for 5.8 months, from November 24 to May 18, with an average temperature below 37°F. The day of the year with the coolest water is March 2, with an average temperature of 32°F.
Average Water Temperature
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 very significant seasonal variation over the course of the year.
The brighter period of the year lasts for 3.0 months, from April 30 to July 31, with an average daily incident shortwave energy per square meter above 4.6 kWh. The brightest day of the year is June 10, with an average of 5.8 kWh.
The darker period of the year lasts for 4.1 months, from October 17 to February 21, with an average daily incident shortwave energy per square meter below 1.3 kWh. The darkest day of the year is December 21, with an average of 0.1 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Anchorage are 61.218 deg latitude, -149.900 deg longitude, and 69 ft elevation (map ).
The topography within 2 miles of Anchorage contains only modest variations in elevation, with a maximum elevation change of 177 feet, and an average elevation above sea level of 48 feet. Within 10 miles contains large variations in elevation (3,212 feet). Within 50 miles contains extreme variations in elevation (7,936 feet).
The area within 2 miles of Anchorage is covered by artificial surfaces (79%) and sparse vegetation (14%), within 10 miles by water (29%) and trees (22%), and within 50 miles by trees (32%) and shrubs (21%).
This report illustrates the typical weather in Anchorage, 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 are 2 weather stations near enough to contribute to our estimation of the temperature and dew point in Anchorage.
For each station, the records are corrected for the elevation difference between that station and Anchorage according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at Anchorage is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Anchorage and a given station.
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 .