Fall Weather at Ronald Reagan Washington National Airport United StatesDaily high temperatures decrease by 31°F, from 83°F to 52°F, rarely falling below 40°F or exceeding 92°F. Daily low temperatures decrease by 29°F, from 68°F to 39°F, rarely falling below 29°F or exceeding 75°F. For reference, on July 20, the hottest day of the year, temperatures at Ronald Reagan Washington National Airport typically range from 73°F to 88°F, while on January 30, the coldest day of the year, they range from 30°F to 44°F. The figure below shows you a compact characterization of the hourly average fall temperatures. 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. Qabaqçöl, Azerbaijan (5,833 miles away) is the far-away foreign place with temperatures most similar to Ronald Reagan Washington National Airport (view comparison). CloudsThe fall at Ronald Reagan Washington National Airport experiences rapidly increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 36% to 48%. The lowest chance of overcast or mostly cloudy conditions is 35% on October 11. The clearest day of the fall is October 11, with clear, mostly clear, or partly cloudy conditions 65% of the time. For reference, on January 5, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 52%, while on September 22, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 65%. PrecipitationA wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. At Ronald Reagan Washington National Airport, the chance of a wet day over the course of the fall is gradually decreasing, starting the season at 27% and ending it at 24%. For reference, the year's highest daily chance of a wet day is 39% on June 16, and its lowest chance is 20% on October 19. Over the course of the fall at Ronald Reagan Washington National Airport, the chance of a day with only rain decreases from 27% to 22%, 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. RainfallTo show variation within the season and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day. The average sliding 31-day rainfall during the fall at Ronald Reagan Washington National Airport is essentially constant, remaining about 3.3 inches throughout, and rarely exceeding 6.0 inches or falling below 0.7 inches. The highest average 31-day accumulation is 3.5 inches on September 28. SnowfallAs with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day. The average sliding 31-day snowfall during the fall at Ronald Reagan Washington National Airport is increasing, starting the season at -0.0 inches, when it rarely exceeds 0.0 inches or falls below -0.0 inches, and ending the season at 1.4 inches, when it rarely exceeds 4.7 inches or falls below -0.0 inches. SunOver the course of the fall at Ronald Reagan Washington National Airport, the length of the day is very rapidly decreasing. From the start to the end of the season, the length of the day decreases by 3 hours, 20 minutes, implying an average daily decrease of 2 minutes, 14 seconds, and weekly decrease of 15 minutes, 35 seconds. The shortest day of the fall is November 30, with 9 hours, 40 minutes of daylight and the longest day is September 1, with 13 hours, 0 minutes of daylight. The earliest sunrise of the fall at Ronald Reagan Washington National Airport is 6:37 AM on September 1 and the latest sunrise is 59 minutes later at 7:36 AM on November 2. The latest sunset is 7:37 PM on September 1 and the earliest sunset is 2 hours, 51 minutes earlier at 4:46 PM on November 30. Daylight saving time (DST) starts at 1:00 AM on November 3, 2024, shifting sunrise and sunset to be an hour later. For reference, on June 20, the longest day of the year, the Sun rises at 5:43 AM and sets 14 hours, 54 minutes later, at 8:36 PM, while on December 21, the shortest day of the year, it rises at 7:23 AM and sets 9 hours, 27 minutes later, at 4:49 PM. The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation. MoonThe figure below presents a compact representation of key lunar data for the fall of 2024. 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. HumidityWe 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 Ronald Reagan Washington National Airport is very rapidly decreasing during the fall, falling from 45% to 0% over the course of the season. For reference, on July 27, the muggiest day of the year, there are muggy conditions 68% of the time, while on January 9, the least muggy day of the year, there are muggy conditions 0% of the time. WindThis 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 Ronald Reagan Washington National Airport is rapidly increasing during the fall, increasing from 6.3 miles per hour to 8.4 miles per hour over the course of the season. For reference, on February 26, the windiest day of the year, the daily average wind speed is 9.6 miles per hour, while on July 31, the calmest day of the year, the daily average wind speed is 5.7 miles per hour. The wind direction at Ronald Reagan Washington National Airport during the fall is predominantly out of the south from September 1 to October 16 and the west from October 16 to November 30. Water TemperatureRonald Reagan Washington National 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 Ronald Reagan Washington National Airport is very rapidly decreasing during the fall, falling by 26°F, from 76°F to 49°F, over the course of the season. Growing SeasonDefinitions 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 Ronald Reagan Washington National Airport typically lasts for 7.9 months (242 days), from around March 24 to around November 21, rarely starting before March 5 or after April 11, and rarely ending before November 1 or after December 15. During the fall at Ronald Reagan Washington National Airport, the chance that a given day is within the growing season is very rapidly decreasing falling from 100% to 31% over the course of the season. 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 Ronald Reagan Washington National Airport are very rapidly increasing during the fall, increasing by 1,031°F, from 3,393°F to 4,424°F, over the course of the season. Solar EnergyThis 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 Ronald Reagan Washington National Airport is very rapidly decreasing during the fall, falling by 3.4 kWh, from 5.7 kWh to 2.2 kWh, over the course of the season. TopographyFor the purposes of this report, the geographical coordinates of Ronald Reagan Washington National Airport are 38.852 deg latitude, -77.037 deg longitude, and 13 ft elevation. The topography within 2 miles of Ronald Reagan Washington National Airport contains only modest variations in elevation, with a maximum elevation change of 167 feet and an average elevation above sea level of 21 feet. Within 10 miles also contains only modest variations in elevation (476 feet). Within 50 miles contains only modest variations in elevation (1,909 feet). The area within 2 miles of Ronald Reagan Washington National Airport is covered by artificial surfaces (66%) and water (31%), within 10 miles by artificial surfaces (83%), and within 50 miles by trees (40%) and cropland (22%). Data SourcesThis report illustrates the typical weather at Ronald Reagan Washington National Airport, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016. Temperature and Dew PointRonald Reagan Washington National 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 Washington Executive Airport/Hyde Field, College Park Airport, Mount Vernon Hospital Heliport, Montgomery County Airpark, Tipton Airport, Washington Dulles International Airport, Quantico Marine Corps Airfield / Turner Field, and Baltimore-Washington International Airport. Other DataAll 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 © OpenStreetMap contributors. DisclaimerThe 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. Please review our full terms contained on our Terms of Service page. |