Average Weather in Selfoss Iceland
In Selfoss, the summers are cool; the winters are long, chilly, wet, and windy; and it is mostly cloudy year round. Over the course of the year, the temperature typically varies from 27°F to 57°F and is rarely below 14°F or above 62°F.
The warm season lasts for 3.0 months, from June 7 to September 6, with an average daily high temperature above 53°F. The hottest day of the year is July 31, with an average high of 57°F and low of 48°F.
The cold season lasts for 4.9 months, from November 6 to April 2, with an average daily high temperature below 39°F. The coldest day of the year is January 1, with an average low of 27°F and high of 35°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
In Selfoss, 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 in Selfoss begins around April 3 and lasts for 7.0 months, ending around November 3. On May 21, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 44% of the time, and overcast or mostly cloudy 56% of the time.
The cloudier part of the year begins around November 3 and lasts for 5.0 months, ending around April 3. On February 5, the cloudiest day of the year, the sky is overcast or mostly cloudy 77% of the time, and clear, mostly clear, or partly cloudy 23% of the time.
Cloud Cover Categories
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Selfoss varies throughout the year.
The wetter season lasts 8.0 months, from August 20 to April 21, with a greater than 42% chance of a given day being a wet day. The chance of a wet day peaks at 55% on February 26.
The drier season lasts 4.0 months, from April 21 to August 20. The smallest chance of a wet day is 28% on May 29.
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 throughout the year is rain alone, with a peak probability of 48% on September 21.
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. Selfoss experiences significant seasonal variation in monthly rainfall.
Rain falls throughout the year in Selfoss. The most rain falls during the 31 days centered around February 15, with an average total accumulation of 5.0 inches.
The least rain falls around June 6, with an average total accumulation of 2.3 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 of the year. Selfoss experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 6.2 months, from October 20 to April 25, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around January 18, with an average total liquid-equivalent accumulation of 1.0 inches.
The snowless period of the year lasts for 5.8 months, from April 25 to October 20. The least snow falls around July 21, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Selfoss varies extremely over the course of the year. In 2017, the shortest day is December 21, with 4 hours, 14 minutes of daylight; the longest day is June 21, with 20 hours, 58 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 2:56 AM on June 20, and the latest sunrise is 8 hours, 20 minutes later at 11:16 AM on December 25. The earliest sunset is at 3:28 PM on December 18, and the latest sunset is 8 hours, 27 minutes later at 11:55 PM on June 21.
Daylight saving time (DST) is not observed in Selfoss during 2017.
Sunrise & Sunset with Twilight
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 Selfoss, 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 Selfoss experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 6.5 months, from October 18 to May 1, with average wind speeds of more than 7.0 miles per hour. The windiest day of the year is December 31, with an average hourly wind speed of 9.0 miles per hour.
The calmer time of year lasts for 5.5 months, from May 1 to October 18. The calmest day of the year is July 21, with an average hourly wind speed of 5.1 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Selfoss varies throughout the year.
The wind is most often from the south for 2.2 months, from June 24 to August 31, with a peak percentage of 32% on July 28. The wind is most often from the east for 9.8 months, from August 31 to June 24, with a peak percentage of 38% on January 1.
Selfoss 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 2.5 months, from June 27 to September 11, with an average temperature above 51°F. The day of the year with the warmest water is August 6, with an average temperature of 53°F.
The time of year with cooler water lasts for 5.4 months, from November 23 to May 3, with an average temperature below 44°F. The day of the year with the coolest water is March 4, with an average temperature of 42°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 extreme seasonal variation over the course of the year.
The brighter period of the year lasts for 2.9 months, from May 5 to August 3, with an average daily incident shortwave energy per square meter above 4.2 kWh. The brightest day of the year is June 17, with an average of 5.3 kWh.
The darker period of the year lasts for 4.8 months, from October 10 to March 5, with an average daily incident shortwave energy per square meter below 1.1 kWh. The darkest day of the year is December 21, with an average of 0.0 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Selfoss are 63.933 deg latitude, -20.997 deg longitude, and 62 ft elevation.
The topography within 2 miles of Selfoss contains only modest variations in elevation, with a maximum elevation change of 180 feet and an average elevation above sea level of 62 feet. Within 10 miles contains only modest variations in elevation (1,791 feet). Within 50 miles contains very significant variations in elevation (5,410 feet).
The area within 2 miles of Selfoss is covered by grassland (53%), artificial surfaces (19%), and shrubs (15%), within 10 miles by shrubs (31%) and grassland (24%), and within 50 miles by water (40%) and shrubs (28%).
This report illustrates the typical weather in Selfoss, 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 Selfoss.
For each station, the records are corrected for the elevation difference between that station and Selfoss 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 Selfoss is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Selfoss 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 .
Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.