May Weather in Reykjavík Iceland
Daily high temperatures increase by 6°F, from 45°F to 51°F, rarely falling below 39°F or exceeding 57°F.
Daily low temperatures increase by 7°F, from 36°F to 43°F, rarely falling below 28°F or exceeding 47°F.
For reference, on July 31, the hottest day of the year, temperatures in Reykjavík typically range from 49°F to 57°F, while on January 24, the coldest day of the year, they range from 28°F to 36°F.
Average High and Low Temperature in May in Reykjavík
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on May. 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 May in Reykjavík
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 month of May in Reykjavík 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 lowest chance of overcast or mostly cloudy conditions is 57% on May 21.
The clearest day of the month is May 21, with clear, mostly clear, or partly cloudy conditions 43% of the time.
For reference, on January 21, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 78%, while on May 21, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 43%.
Cloud Cover Categories in May in Reykjavík
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. In Reykjavík, the chance of a wet day over the course of May is rapidly decreasing, starting the month at 36% and ending it at 29%.
For reference, the year's highest daily chance of a wet day is 55% on February 26, and its lowest chance is 29% on July 7.
Over the course of May in Reykjavík, the chance of a day with only rain decreases from 34% to 29%, the chance of a day with mixed snow and rain remains an essentially constant 1% throughout, and the chance of a day with only snow remains an essentially constant 0% throughout.
Probability of Precipitation in May in Reykjavík
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 May in Reykjavík is gradually decreasing, starting the month at 2.7 inches, when it rarely exceeds 4.7 inches or falls below 0.9 inches, and ending the month at 2.2 inches, when it rarely exceeds 4.0 inches or falls below 0.8 inches.
Average Monthly Rainfall in May in Reykjavík
Over the course of May in Reykjavík, the length of the day is very rapidly increasing. From the start to the end of the month, the length of the day increases by 3 hours, 10 minutes, implying an average daily increase of 6 minutes, 20 seconds, and weekly increase of 44 minutes, 18 seconds.
The shortest day of the month is May 1, with 16 hours, 53 minutes of daylight and the longest day is May 31, with 20 hours, 3 minutes of daylight.
Hours of Daylight and Twilight in May in Reykjavík
The latest sunrise of the month in Reykjavík is 4:59 AM on May 1 and the earliest sunrise is 1 hour, 34 minutes earlier at 3:25 AM on May 31.
The earliest sunset is 9:52 PM on May 1 and the latest sunset is 1 hour, 36 minutes later at 11:27 PM on May 31.
Daylight saving time is not observed in Reykjavík during 2021.
For reference, on June 21, the longest day of the year, the Sun rises at 2:55 AM and sets 21 hours, 8 minutes later, at 12:03 AM, while on December 21, the shortest day of the year, it rises at 11:22 AM and sets 4 hours, 7 minutes later, at 3:29 PM.
Sunrise & Sunset with Twilight in May in Reykjavík
The figure below presents a compact representation of key lunar data for May 2021. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.
Moon Rise, Set & Phases in May in Reykjavík
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 Reykjavík is essentially constant during May, remaining around 0% throughout.
Humidity Comfort Levels in May in Reykjavík
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
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 Reykjavík is rapidly decreasing during May, decreasing from 11.5 miles per hour to 9.1 miles per hour over the course of the month.
For reference, on January 7, the windiest day of the year, the daily average wind speed is 16.1 miles per hour, while on July 21, the calmest day of the year, the daily average wind speed is 7.9 miles per hour.
Average Wind Speed in May in Reykjavík
The wind direction in Reykjavík during May is predominantly out of the east from May 1 to May 6 and the south from May 6 to May 31.
Wind Direction in May in Reykjavík
Reykjavík 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 Reykjavík is increasing during May, rising by 4°F, from 43°F to 47°F, over the course of the month.
Average Water Temperature in May in Reykjavík
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 Reykjavík typically lasts for 4.9 months (148 days), from around May 10 to around October 6, rarely starting before April 22 or after May 30, and rarely ending before September 16 or after October 24.
During May in Reykjavík, the chance that a given day is within the growing season is very rapidly increasing rising from 26% to 92% over the course of the month.
Time Spent in Various Temperature Bands and the Growing Season in May in Reykjavík
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
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 Reykjavík are essentially constant during May, remaining within 6°F of 7°F throughout.
Growing Degree Days in May in Reykjavík
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 Reykjavík is increasing during May, rising by 1.1 kWh, from 3.9 kWh to 5.1 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in May in Reykjavík
For the purposes of this report, the geographical coordinates of Reykjavík are 64.135 deg latitude, -21.895 deg longitude, and 125 ft elevation.
The topography within 2 miles of Reykjavík contains only modest variations in elevation, with a maximum elevation change of 203 feet and an average elevation above sea level of 57 feet. Within 10 miles contains only modest variations in elevation (2,851 feet). Within 50 miles contains large variations in elevation (4,426 feet).
The area within 2 miles of Reykjavík is covered by artificial surfaces (83%), within 10 miles by water (39%) and shrubs (30%), and within 50 miles by water (53%) and shrubs (23%).
This report illustrates the typical weather in Reykjavík, 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 Reykjavík.
For each station, the records are corrected for the elevation difference between that station and Reykjavík 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 Reykjavík is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Reykjavík 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 Algorithms 2nd Edition , 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 airports 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.
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.