Average Weather in August at London Heathrow Airport United Kingdom
At London Heathrow Airport, the month of August is characterized by gradually falling daily high temperatures, with daily highs decreasing by 4°F, from 74°F to 70°F over the course of the month, and rarely exceeding 83°F or dropping below 64°F. The highest daily average high temperature is 74°F on August 2.
Daily low temperatures decrease by 3°F, from 58°F to 55°F, rarely falling below 49°F or exceeding 63°F.
For reference, on July 28, the hottest day of the year, temperatures at London Heathrow Airport typically range from 58°F to 74°F, while on February 7, the coldest day of the year, they range from 36°F to 46°F.
Average High and Low Temperature in August
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on August. 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 August
The month of August at London Heathrow Airport experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 45% throughout the month.
The clearest day of the month is August 1, with clear, mostly clear, or partly cloudy conditions 56% of the time.
For reference, on December 27, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 74%, while on July 15, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 58%.
Cloud Cover Categories in August
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. At London Heathrow Airport, the chance of a wet day over the course of August is essentially constant, remaining around 22% throughout.
For reference, the year's highest daily chance of a wet day is 33% on December 30, and its lowest chance is 20% on September 11.
Probability of Precipitation in August
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 August at London Heathrow Airport is essentially constant, remaining about 1.5 inches throughout, and rarely exceeding 2.9 inches or falling below 0.4 inches.
Average Monthly Rainfall in August
Over the course of August at London Heathrow Airport, the length of the day is rapidly decreasing. From the start to the end of the month, the length of the day decreases by 1 hour, 47 minutes, implying an average daily decrease of 3 minutes, 33 seconds, and weekly decrease of 24 minutes, 52 seconds.
The shortest day of the month is August 31, with 13 hours, 37 minutes of daylight and the longest day is August 1, with 15 hours, 24 minutes of daylight.
Hours of Daylight and Twilight in August
The earliest sunrise of the month at London Heathrow Airport is 5:25 AM on August 1 and the latest sunrise is 47 minutes later at 6:13 AM on August 31.
The latest sunset is 8:49 PM on August 1 and the earliest sunset is 59 minutes earlier at 7:50 PM on August 31.
Daylight saving time is observed at London Heathrow Airport during 2017, but it neither starts nor ends during August, so the entire month is in daylight saving time.
For reference, on June 21, the longest day of the year, the Sun rises at 4:44 AM and sets 16 hours, 38 minutes later, at 9:22 PM, while on December 21, the shortest day of the year, it rises at 8:04 AM and sets 7 hours, 50 minutes later, at 3:55 PM.
Sunrise & Sunset with Twilight in August
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 London Heathrow Airport is essentially constant during August, remaining around 0% throughout.
The highest chance of a muggy day during August is 1% on August 11.
For reference, on August 11, the muggiest day of the year, there are muggy conditions 1% of the time, while on October 1, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in August
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 London Heathrow Airport is gradually increasing during August, increasing from 9.7 miles per hour to 10.3 miles per hour over the course of the month.
For reference, on January 3, the windiest day of the year, the daily average wind speed is 13.3 miles per hour, while on August 3, the calmest day of the year, the daily average wind speed is 9.7 miles per hour.
The lowest daily average wind speed during August is 9.7 miles per hour on August 3.
Average Wind Speed in August
Wind Direction in August
London Heathrow 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 London Heathrow Airport is essentially constant during August, remaining within 1°F of 63°F throughout.
The highest average surface water temperature during August is 63°F on August 28.
Average Water Temperature in August
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 London Heathrow Airport typically lasts for 8.1 months (249 days), from around March 23 to around November 27, rarely starting before February 14 or after April 21, and rarely ending before November 2 or after December 22.
The month of August at London Heathrow Airport is reliably fully within the growing season.
Time Spent in Various Temperature Bands and the Growing Season in August
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 London Heathrow Airport is increasing during August, increasing by 433°F, from 1,126°F to 1,559°F, over the course of the month.
Growing Degree Days in August
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 London Heathrow Airport is decreasing during August, falling by 1.2 kWh, from 5.9 kWh to 4.7 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in August
For the purposes of this report, the geographical coordinates of London Heathrow Airport are 51.471 deg latitude, -0.456 deg longitude, and 75 ft elevation.
The topography within 2 miles of London Heathrow Airport contains only modest variations in elevation, with a maximum elevation change of 125 feet and an average elevation above sea level of 78 feet. Within 10 miles also contains only modest variations in elevation (407 feet). Within 50 miles contains only modest variations in elevation (1,027 feet).
The area within 2 miles of London Heathrow Airport is covered by artificial surfaces (75%) and grassland (14%), within 10 miles by artificial surfaces (68%) and grassland (16%), and within 50 miles by cropland (41%) and grassland (26%).
This report illustrates the typical weather at London Heathrow 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
London Heathrow 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 include but are not limited to RAF Northolt, Bracknell / Beaufort Park, London Weather Centre, Farnborough Airport, Luton Airport, London Gatwick Airport, London City Airport, and RAF Odiham.
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.
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.