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Climate and Average Weather Year Round at Washington Dulles International Airport Virginia, United States

At Washington Dulles International Airport, the summers are warm and humid, the winters are very cold and snowy, and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 25°F to 87°F and is rarely below 12°F or above 95°F.

Based on the tourism score, the best times of year to visit Washington Dulles International Airport for warm-weather activities are from early June to early July and from early August to late September.

Climate at Washington Dulles International Airport

very coldcoldcoolwarmhotwarmcoolcoldJanFebMarAprMayJunJulAugSepOctNovDecNowNow65%65%48%48%clearovercastprecipitation: 3.6 inprecipitation: 3.6 in2.4 in2.4 inmuggy: 61%muggy: 61%0%0%drydrytourism score: 6.5tourism score: 6.50.30.3
Washington Dulles International Airport weather by month. Click on each chart for more information.

The hot season lasts for 3.6 months, from May 29 to September 16, with an average daily high temperature above 78°F. The hottest month of the year at Washington Dulles International Airport is July, with an average high of 87°F and low of 67°F.

The cold season lasts for 3.1 months, from November 30 to March 3, with an average daily high temperature below 51°F. The coldest month of the year at Washington Dulles International Airport is January, with an average low of 26°F and high of 42°F.

Average High and Low Temperature at Washington Dulles International Airport

Average High and Low Temperature at Washington Dulles International AirporthotcoldcoldJanFebMarAprMayJunJulAugSepOctNovDec0°F0°F10°F10°F20°F20°F30°F30°F40°F40°F50°F50°F60°F60°F70°F70°F80°F80°F90°F90°F100°F100°FJan 3042°FJan 3042°FJul 2087°FJul 2087°F25°F25°F68°F68°FMay 2978°FMay 2978°FSep 1678°FSep 1678°FNov 3051°FNov 3051°FMar 351°FMar 351°F58°F58°F59°F59°F34°F34°F32°F32°FNowNow
The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.
AverageJanFebMarAprMayJunJulAugSepOctNovDec
High 42°F46°F55°F66°F75°F83°F87°F85°F78°F67°F56°F46°F
Temp. 33°F36°F44°F55°F64°F72°F77°F75°F68°F56°F46°F37°F
Low 26°F28°F36°F45°F54°F63°F67°F66°F58°F47°F37°F30°F

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 Washington Dulles International Airport

Average Hourly Temperature at Washington Dulles International AirportJanFebMarAprMayJunJulAugSepOctNovDec12 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMNowNowfreezingvery coldvery coldcoldcoldcoolcoolcomfortablewarmhotfreezingfreezing
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 average hourly temperature, color coded into bands. The shaded overlays indicate night and civil twilight.

Tbilisi, Georgia (5,796 miles away) is the far-away foreign place with temperatures most similar to Washington Dulles International Airport (view comparison).

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At Washington Dulles International Airport, the average percentage of the sky covered by clouds experiences mild seasonal variation over the course of the year.

The clearer part of the year at Washington Dulles International Airport begins around July 1 and lasts for 4.3 months, ending around November 11.

The clearest month of the year at Washington Dulles International Airport is September, during which on average the sky is clear, mostly clear, or partly cloudy 64% of the time.

The cloudier part of the year begins around November 11 and lasts for 7.7 months, ending around July 1.

The cloudiest month of the year at Washington Dulles International Airport is January, during which on average the sky is overcast or mostly cloudy 51% of the time.

Cloud Cover Categories at Washington Dulles International Airport

Cloud Cover Categories at Washington Dulles International AirportclearercloudiercloudierJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%Sep 2265%Sep 2265%Jan 1148%Jan 1148%Jul 156%Jul 156%Nov 1157%Nov 1157%NowNowclearmostly clearpartly cloudymostly cloudyovercast
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds.
FractionJanFebMarAprMayJunJulAugSepOctNovDec
Cloudier 51%51%49%48%48%45%41%37%36%37%45%51%
Clearer 49%49%51%52%52%55%59%63%64%63%55%49%

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days at Washington Dulles International Airport varies throughout the year.

The wetter season lasts 4.4 months, from April 7 to August 20, with a greater than 29% chance of a given day being a wet day. The month with the most wet days at Washington Dulles International Airport is June, with an average of 11.3 days with at least 0.04 inches of precipitation.

The drier season lasts 7.6 months, from August 20 to April 7. The month with the fewest wet days at Washington Dulles International Airport is January, with an average of 6.5 days with at least 0.04 inches of precipitation.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone at Washington Dulles International Airport is June, with an average of 11.3 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 39% on July 12.

Daily Chance of Precipitation at Washington Dulles International Airport

Daily Chance of Precipitation at Washington Dulles International AirportwetdrydryJanFebMarAprMayJunJulAugSepOctNovDec0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%Jul 1239%Jul 1239%Oct 1920%Oct 1920%Apr 729%Apr 729%Aug 2029%Aug 2029%NowNowrainmixedsnow
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).
Days ofJanFebMarAprMayJunJulAugSepOctNovDec
Rain 3.9d4.3d6.9d9.0d11.1d11.3d11.4d9.8d7.8d6.8d6.3d5.4d
Mixed 1.5d1.4d0.8d0.1d0.0d0.0d0.0d0.0d0.0d0.0d0.5d1.1d
Snow 1.1d0.9d0.4d0.0d0.0d0.0d0.0d0.0d0.0d0.0d0.1d0.5d
Any 6.5d6.6d8.1d9.0d11.1d11.3d11.4d9.8d7.8d6.8d6.9d7.0d

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. Washington Dulles International Airport experiences some seasonal variation in monthly rainfall.

Rain falls throughout the year at Washington Dulles International Airport. The month with the most rain at Washington Dulles International Airport is May, with an average rainfall of 3.6 inches.

The month with the least rain at Washington Dulles International Airport is January, with an average rainfall of 1.8 inches.

Average Monthly Rainfall at Washington Dulles International Airport

Average Monthly Rainfall at Washington Dulles International AirportJanFebMarAprMayJunJulAugSepOctNovDec0 in0 in2 in2 in4 in4 in6 in6 in8 in8 inMay 183.6 inMay 183.6 inJan 291.8 inJan 291.8 inSep 283.4 inSep 283.4 inNowNow
The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average snowfall.
JanFebMarAprMayJunJulAugSepOctNovDec
Rainfall 1.8″1.9″2.8″3.3″3.6″3.4″3.0″3.0″3.3″3.2″3.0″2.4″

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Washington Dulles International Airport experiences significant seasonal variation in monthly snowfall.

The snowy period of the year lasts for 4.4 months, from November 16 to March 27, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow at Washington Dulles International Airport is February, with an average snowfall of 6.8 inches.

The snowless period of the year lasts for 7.6 months, from March 27 to November 16. The least snow falls around July 14, with an average total accumulation of 0.0 inches.

Average Monthly Snowfall at Washington Dulles International Airport

Average Monthly Snowfall at Washington Dulles International AirportsnowsnowJanFebMarAprMayJunJulAugSepOctNovDec0 in0 in5 in5 in10 in10 in15 in15 in20 in20 inFeb 57.2 inFeb 57.2 inJul 140.0 inJul 140.0 inNov 161.0 inNov 161.0 inMar 271.0 inMar 271.0 inNowNow
The average snowfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average rainfall.
JanFebMarAprMayJunJulAugSepOctNovDec
Snowfall 6.3″6.8″2.3″0.0″0.0″0.0″0.0″0.0″0.0″0.1″0.9″3.9″

The length of the day at Washington Dulles International Airport varies significantly over the course of the year. In 2024, the shortest day is December 21, with 9 hours, 26 minutes of daylight; the longest day is June 20, with 14 hours, 54 minutes of daylight.

Hours of Daylight and Twilight at Washington Dulles International Airport

Hours of Daylight and Twilight at Washington Dulles International AirportJanFebMarAprMayJunJulAugSepOctNovDec0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hr12 hr, 7 minMar 1912 hr, 7 minMar 1914 hr, 54 minJun 2014 hr, 54 minJun 2012 hr, 10 minSep 2212 hr, 10 minSep 229 hr, 26 minDec 219 hr, 26 minDec 21nightnightdayNowNow
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.
Hours ofJanFebMarAprMayJunJulAugSepOctNovDec
Daylight 9.8h10.8h12.0h13.3h14.3h14.9h14.6h13.6h12.4h11.1h10.0h9.5h

The earliest sunrise is at 5:43 AM on June 13, and the latest sunrise is 1 hour, 55 minutes later at 7:38 AM on November 2. The earliest sunset is at 4:47 PM on December 7, and the latest sunset is 3 hours, 52 minutes later at 8:39 PM on June 27.

Daylight saving time (DST) is observed at Washington Dulles International Airport during 2024, starting in the spring on March 10, lasting 7.8 months, and ending in the fall on November 3.

Sunrise & Sunset with Twilight and Daylight Saving Time at Washington Dulles International Airport

Sunrise & Sunset with Twilight and Daylight Saving Time at Washington Dulles International AirportJanFebMarAprMayJunJulAugSepOctNovDec12 AM2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMJun 135:43 AMJun 135:43 AM8:39 PMJun 278:39 PMJun 27Dec 74:47 PMDec 74:47 PM7:38 AMNov 27:38 AMNov 2Mar 10DSTMar 10DSTDSTNov 3DSTNov 3daynightnightnightnightSolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day over the course of the year 2024. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray. The transitions to and from daylight saving time are indicated by the 'DST' labels.

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.

Solar Elevation and Azimuth at Washington Dulles International Airport

Solar Elevation and Azimuth at Washington Dulles International AirportJanFebMarAprMayJunJulAugSepOctNovDec12 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AM0001010101020202030303040404050506060700001010102020202030304040505060702874NowNow
northeastsouthwest
Solar elevation and azimuth over the course of the year 2024. The black lines are lines of constant solar elevation (the angle of the sun above the horizon, in degrees). The background color fills indicate the azimuth (the compass bearing) of the sun. The lightly tinted areas at the boundaries of the cardinal compass points indicate the implied intermediate directions (northeast, southeast, southwest, and northwest).

The figure below presents a compact representation of key lunar data for 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.

Moon Rise, Set & Phases at Washington Dulles International Airport

The time in which the moon is above the horizon (light blue area), with new moons (dark gray lines) and full moons (blue lines) indicated. The shaded overlays indicate night and civil 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.

Washington Dulles International Airport experiences extreme seasonal variation in the perceived humidity.

The muggier period of the year lasts for 4.0 months, from May 24 to September 23, during which time the comfort level is muggy, oppressive, or miserable at least 15% of the time. The month with the most muggy days at Washington Dulles International Airport is July, with 17.9 days that are muggy or worse.

The month with the fewest muggy days at Washington Dulles International Airport is February, with 0.0 days that are muggy or worse.

Humidity Comfort Levels at Washington Dulles International Airport

Humidity Comfort Levels at Washington Dulles International AirportmuggyJanFebMarAprMayJunJulAugSepOctNovDec0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%Feb 190%Feb 190%Jul 2761%Jul 2761%May 2415%May 2415%Sep 2315%Sep 2315%NowNowoppressiveoppressivemuggymuggydrydryhumidhumidcomfortablecomfortable
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The percentage of time spent at various humidity comfort levels, categorized by dew point.
JanFebMarAprMayJunJulAugSepOctNovDec
Muggy days 0.0d0.0d0.0d0.2d3.3d11.3d17.9d15.1d6.7d1.2d0.1d0.0d

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 Washington Dulles International Airport experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 6.4 months, from October 26 to May 8, with average wind speeds of more than 7.3 miles per hour. The windiest month of the year at Washington Dulles International Airport is March, with an average hourly wind speed of 9.0 miles per hour.

The calmer time of year lasts for 5.6 months, from May 8 to October 26. The calmest month of the year at Washington Dulles International Airport is July, with an average hourly wind speed of 5.6 miles per hour.

Average Wind Speed at Washington Dulles International Airport

Average Wind Speed at Washington Dulles International AirportwindywindyJanFebMarAprMayJunJulAugSepOctNovDec0 mph0 mph2 mph2 mph4 mph4 mph6 mph6 mph8 mph8 mph10 mph10 mph12 mph12 mph14 mph14 mphFeb 269.1 mphFeb 269.1 mphJul 315.5 mphJul 315.5 mphOct 267.3 mphOct 267.3 mphMay 87.3 mphMay 87.3 mphNowNow
The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.
JanFebMarAprMayJunJulAugSepOctNovDec
Wind Speed (mph) 8.58.99.08.37.06.15.65.66.47.17.77.9

The predominant average hourly wind direction at Washington Dulles International Airport varies throughout the year.

The wind is most often from the south for 1.1 months, from May 8 to June 11 and for 2.3 months, from July 29 to October 6, with a peak percentage of 33% on August 15. The wind is most often from the west for 1.6 months, from June 11 to July 29 and for 7.1 months, from October 6 to May 8, with a peak percentage of 37% on July 5.

Wind Direction at Washington Dulles International Airport

Wind Direction at Washington Dulles International AirportWSWSWJanFebMarAprMayJunJulAugSepOctNovDec0%100%20%80%40%60%60%40%80%20%100%0%NowNowwestsouthnortheast
northeastsouthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions, excluding hours in which the mean wind speed is less than 1.0 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Washington Dulles International 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 water temperature experiences extreme seasonal variation over the course of the year.

The time of year with warmer water lasts for 3.3 months, from June 22 to October 1, with an average temperature above 68°F. The month of the year at Washington Dulles International Airport with the warmest water is August, with an average temperature of 76°F.

The time of year with cooler water lasts for 3.4 months, from December 21 to April 3, with an average temperature below 44°F. The month of the year at Washington Dulles International Airport with the coolest water is February, with an average temperature of 37°F.

Average Water Temperature at Washington Dulles International Airport

Average Water Temperature at Washington Dulles International AirportwarmcoolJanFebMarAprMayJunJulAugSepOctNovDec30°F30°F40°F40°F50°F50°F60°F60°F70°F70°F80°F80°FAug 976°FAug 976°F36°FFeb 536°FFeb 5Jun 2268°FJun 2268°FOct 168°FOct 168°FDec 2144°FDec 2144°FApr 344°FApr 344°FNowNow
The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.
WaterJanFebMarAprMayJunJulAugSepOctNovDec
Temperature 39°F37°F40°F47°F56°F66°F74°F76°F72°F64°F54°F45°F

To characterize how pleasant the weather is at Washington Dulles International Airport 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 times of year to visit Washington Dulles International Airport for general outdoor tourist activities are from early June to early July and from early August to late September, with a peak score in the first week of September.

Tourism Score at Washington Dulles International Airport

Tourism Score at Washington Dulles International Airportbest timeJanFebMarAprMayJunJulAugSepOctNovDec002244668810106.56.50.30.36.06.05.75.7NowNowtemperaturetemperature cloudscloudsprecipitationprecipitationtourism score
The tourism score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Washington Dulles International Airport for hot-weather activities is from late June to late August, with a peak score in the last week of July.

Beach/Pool Score at Washington Dulles International Airport

Beach/Pool Score at Washington Dulles International Airportbest timeJanFebMarAprMayJunJulAugSepOctNovDec002244668810105.95.90.00.0NowNowtemperaturetemperature cloudscloudsprecipitationprecipitationbeach/pool score
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

Methodology

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.

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 Washington Dulles International Airport typically lasts for 6.4 months (195 days), from around April 10 to around October 22, rarely starting before March 23 or after April 29, and rarely ending before October 2 or after November 10.

Time Spent in Various Temperature Bands and the Growing Season at Washington Dulles International Airport

Time Spent in Various Temperature Bands and the Growing Season at Washington Dulles International Airportgrowing seasonJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%50%Apr 1050%Apr 1050%Oct 2250%Oct 2290%Apr 2990%Apr 2990%Oct 290%Oct 210%Mar 2310%Mar 2310%Nov 1010%Nov 100%Dec 140%Dec 14Jul 26100%Jul 26100%freezingvery coldcoolcomfortablewarmhotcoldfrigid
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 percentage of time spent in various temperature bands. The black line is the percentage chance that a given day is within the growing 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.

Based on growing degree days alone, the first spring blooms at Washington Dulles International Airport should appear around March 21, only rarely appearing before March 5 or after April 7.

Growing Degree Days at Washington Dulles International Airport

Growing Degree Days at Washington Dulles International AirportJanFebMarAprMayJunJulAugSepOctNovDec0°F0°F500°F500°F1,000°F1,000°F1,500°F1,500°F2,000°F2,000°F2,500°F2,500°F3,000°F3,000°F3,500°F3,500°F4,000°F4,000°FMar 2187°FMar 2187°FJun 6900°FJun 6900°FJul 141,800°FJul 141,800°FDec 313,920°FDec 313,920°FNowNow
The average growing degree days accumulated over the course of the year, with 25th to 75th and 10th to 90th percentile bands.

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 significant seasonal variation over the course of the year.

The brighter period of the year lasts for 3.8 months, from April 27 to August 22, with an average daily incident shortwave energy per square meter above 6.0 kWh. The brightest month of the year at Washington Dulles International Airport is June, with an average of 6.9 kWh.

The darker period of the year lasts for 3.1 months, from November 5 to February 9, with an average daily incident shortwave energy per square meter below 3.0 kWh. The darkest month of the year at Washington Dulles International Airport is December, with an average of 2.1 kWh.

Average Daily Incident Shortwave Solar Energy at Washington Dulles International Airport

Average Daily Incident Shortwave Solar Energy at Washington Dulles International AirportbrightdarkdarkJanFebMarAprMayJunJulAugSepOctNovDec0 kWh0 kWh1 kWh1 kWh2 kWh2 kWh3 kWh3 kWh4 kWh4 kWh5 kWh5 kWh6 kWh6 kWh7 kWh7 kWh8 kWh8 kWh9 kWh9 kWhJun 226.9 kWhJun 226.9 kWhDec 222.0 kWhDec 222.0 kWhApr 276.0 kWhApr 276.0 kWhAug 226.0 kWhAug 226.0 kWhNov 53.0 kWhNov 53.0 kWhFeb 93.0 kWhFeb 93.0 kWhNowNow
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.
JanFebMarAprMayJunJulAugSepOctNovDec
Solar Energy (kWh) 2.33.24.45.56.46.96.76.15.13.82.62.1

For the purposes of this report, the geographical coordinates of Washington Dulles International Airport are 38.949 deg latitude, -77.449 deg longitude, and 285 ft elevation.

The topography within 2 miles of Washington Dulles International Airport contains only modest variations in elevation, with a maximum elevation change of 118 feet and an average elevation above sea level of 287 feet. Within 10 miles also contains only modest variations in elevation (367 feet). Within 50 miles contains only modest variations in elevation (3,461 feet).

The area within 2 miles of Washington Dulles International Airport is covered by artificial surfaces (84%), within 10 miles by artificial surfaces (51%) and trees (35%), and within 50 miles by trees (46%) and cropland (32%).

This report illustrates the typical weather at Washington Dulles International 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 Point

Washington Dulles International 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 Leesburg Executive Airport, Manassas Regional Airport, Mount Vernon Hospital Heliport, Montgomery County Airpark, Ronald Reagan Washington National Airport, Warrenton-Fauquier Airport, Quantico Marine Corps Airfield / Turner Field, and Frederick Municipal Airport.

Other Data

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 © OpenStreetMap contributors.

Disclaimer

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.

Please review our full terms contained on our Terms of Service page.