Average Weather at Attu Heliport Greenland
At Attu Heliport, the summers are cold and mostly cloudy and the winters are frigid, dry, windy, and overcast. Over the course of the year, the temperature typically varies from -1°F to 49°F and is rarely below -19°F or above 55°F.
Based on the tourism score, the best time of year to visit Attu Heliport for warm-weather activities is from mid July to early August.
The warm season lasts for 3.6 months, from June 1 to September 20, with an average daily high temperature above 41°F. The hottest day of the year is July 22, with an average high of 49°F and low of 40°F.
The cold season lasts for 3.1 months, from December 30 to April 2, with an average daily high temperature below 16°F. The coldest day of the year is February 26, with an average low of -1°F and high of 8°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
At Attu Heliport, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year at Attu Heliport begins around April 19 and lasts for 6.8 months, ending around November 12. On May 28, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 42% of the time, and overcast or mostly cloudy 58% of the time.
The cloudier part of the year begins around November 12 and lasts for 5.2 months, ending around April 19. On January 19, the cloudiest day of the year, the sky is overcast or mostly cloudy 86% of the time, and clear, mostly clear, or partly cloudy 14% of the time.
Cloud Cover Categories
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days at Attu Heliport varies throughout the year.
The wetter season lasts 5.1 months, from June 11 to November 14, with a greater than 14% chance of a given day being a wet day. The chance of a wet day peaks at 23% on August 10.
The drier season lasts 6.9 months, from November 14 to June 11. The smallest chance of a wet day is 4% on January 6.
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 at Attu Heliport changes throughout the year.
Rain alone is the most common for 6.2 months, from April 27 to November 3. The highest chance of a day with rain alone is 23% on August 10.
Snow alone is the most common for 5.8 months, from November 3 to April 27. The highest chance of a day with snow alone is 6% on December 4.
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 of the year. Attu Heliport experiences some seasonal variation in monthly rainfall.
The rainy period of the year lasts for 5.6 months, from May 10 to October 30, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around August 11, with an average total accumulation of 1.7 inches.
The rainless period of the year lasts for 6.4 months, from October 30 to May 10. The least rain falls around February 23, with an average total accumulation of 0.0 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 of the year. Attu Heliport experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 7.4 months, from October 6 to May 20, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around November 15, with an average total liquid-equivalent accumulation of 0.3 inches.
The snowless period of the year lasts for 4.6 months, from May 20 to October 6. The least snow falls around August 11, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
Due to its extreme latitude, Attu Heliport 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.
In the summer at Attu Heliport during 2019, the Sun is continuously above the horizon for 1.7 months, rising at 1:59 AM on May 26, and not setting again until 1:14 AM on July 18.
In the winter at Attu Heliport during 2019, the Sun is continuously below the horizon for 3.6 weeks, setting at 12:42 PM on December 9, and not rising again until 12:19 PM on January 3.
Hours of Daylight and Twilight
Daylight saving time (DST) is observed at Attu Heliport during 2019, starting in the spring on March 30, lasting 6.9 months, and ending in the fall on October 26.
Sunrise & Sunset with Twilight and Daylight Saving Time
The perceived humidity level at Attu Heliport, 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
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed at Attu Heliport experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 4.7 months, from September 28 to February 18, with average wind speeds of more than 9.8 miles per hour. The windiest day of the year is December 3, with an average hourly wind speed of 12.4 miles per hour.
The calmer time of year lasts for 7.3 months, from February 18 to September 28. The calmest day of the year is July 13, with an average hourly wind speed of 7.3 miles per hour.
Average Wind Speed
The predominant average hourly wind direction at Attu Heliport is from the north throughout the year.
Attu Heliport 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 some seasonal variation over the course of the year.
The time of year with warmer water lasts for 2.8 months, from July 5 to September 29, with an average temperature above 38°F. The day of the year with the warmest water is August 22, with an average temperature of 40°F.
The time of year with cooler water lasts for 5.1 months, from December 3 to May 7, with an average temperature below 32°F. The day of the year with the coolest water is March 1, with an average temperature of 30°F.
Average Water Temperature
Best Time of Year to Visit
To characterize how pleasant the weather is at Attu Heliport throughout the year, we compute two travel scores.
The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Attu Heliport for general outdoor tourist activities is from mid July to early August, with a peak score in the third week of July.
The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F.
For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.
Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.
Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.
Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.
Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.
The growing season at Attu Heliport typically lasts for 3.2 months (99 days), from around June 17 to around September 24, rarely starting before May 28 or after July 9, and rarely ending before September 5 or after October 10.
Time Spent in Various Temperature Bands and the Growing Season
Growing Degree Days
The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.
The brighter period of the year lasts for 2.6 months, from May 7 to July 26, with an average daily incident shortwave energy per square meter above 4.6 kWh. The brightest day of the year is June 19, with an average of 5.8 kWh.
The darker period of the year lasts for 5.1 months, from October 5 to March 7, with an average daily incident shortwave energy per square meter below 1.2 kWh. The darkest day of the year is December 22, with an average of 0.0 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Attu Heliport are 67.940 deg latitude, -53.623 deg longitude, and 0 ft elevation.
The topography within 2 miles of Attu Heliport contains only modest variations in elevation, with a maximum elevation change of 341 feet and an average elevation above sea level of 34 feet. Within 10 miles contains only modest variations in elevation (1,010 feet). Within 50 miles contains very significant variations in elevation (4,856 feet).
The area within 2 miles of Attu Heliport is covered by water (55%) and sparse vegetation (32%), within 10 miles by water (59%) and sparse vegetation (22%), and within 50 miles by water (56%) and grassland (13%).
This report illustrates the typical weather at Attu Heliport, 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
Attu Heliport 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.There are no other weather stations in our network within 200 kilometers of this location. Consequently, in the case of missing or erroneous measurements from this station, we fall back on NASA's MERRA-2 modern-era reanalysis , adjusted according to typical seasonal and diurnal differences between this station and the wide-area MERRA-2 reconstructed values.
Time zones for aiports and weather stations are provided by AskGeo.com .