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United States of America

DULLES, VIRGINIA


Home > North America > United States > Virginia
Elevation: 290 feet     Latitude: 38 57N     Longitude: 077 27W

WEATHER
 
CURRENT CONDITIONS

 
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MONTHLY - ALL WEATHER AVERAGES   [ Show Summary ]
[ °C ]   °F
TEMPERATURE 
Average Temperature
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
F55.333.236.244.254.463.272.476.775.467.95646.436.6

Average High Temperature
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
F66.442.546.455.566.775.183.887.986.679.468.257.546

Average Low Temperature
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
F44.223.92632.942.151.26165.564.256.343.835.327.1

Highest Recorded Temperature
Years on Record: 50  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
F105757989939710210510499948479

Lowest Recorded Temperature
Years on Record: 50  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
F-18-18-14-1172836413830159-4

Average Heat Index Temperature
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
F55.533.336.244.254.763.672.877.675.667.855.946.136.9

Average Wind Chill Temperature
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
F53.327.831.240.553.263.372.276.474.767.555.143.732.4

Average Number of Days Above 100F/38C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days0.4------------------0.20.1------------

Average Number of Days Above 90F/32C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days30.3---------0.31.15.611.68.92.70.1------

Average Number of Days Above 80F/26C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days109.6------0.83.810.122.327.927.114.13.10.3---

Average Number of Days Above 70F/21C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days171.30.30.53.71121.628.630.930.826.513.33.40.6

Average Number of Days Above 60F/15C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days229.72.63.210.721.329.530313129.825.312.23

Average Number of Days Above 50F/10C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days280.37.39.419.627.930.93031313030.622.510.1

Average Number of Days Above 40F/4C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days330.617.419.928.4303130313130312921.9

Average Number of Days Below 70F/21C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days349.13128313030.927.523.825.929.1313031

Average Number of Days Below 60F/15C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days27930.92830.929.425.912.24.87.219.329.429.931

Average Number of Days Below 50F/10C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days217.230.727.829.62413.62.30.40.77.222.827.630.5

Average Number of Days Below 40F/4C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days157.429.326.124.212.53.20.1------1.111.721.228.1

Average Number of Days Below 32F/0C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days102.524.321.115.23.90.2------------2.912.422.6

Average Number of Days Below 20F/-6C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days27.310.86.72.3---------------------16.5

Average Number of Days Below 10F/-12C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days5.12.810.2------------------------1.1

Average Number of Days Below 0F/-17C
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days0.90.60.1---------------------------0.1



PRECIPITATION 
Average Precipitation
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
in.41.52.72.73.43.54.643.73.53.93.33.43

Average Number of Days With Precipitation
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days118.79.9910.510.712.210.910.89.48.77.69.19.9

Avg. No. of Days w/Precip. Above 0.1in/2.5mm
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days73.45.75.46.86.87.56.66.55.65.85.15.56.1

Avg. No. of Days w/Precip. Above 0.5in/13mm
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days27.51.81.72.123.22.62.42.12.62.32.42.3

Avg. No. of Days w/Rain Above 1in/25mm
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days10.10.50.70.90.811111.10.80.90.4

Average Precipitable Water
Years on Record: 20  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
in.0.80.40.40.50.60.91.21.41.41.10.80.60.5



PRECIPITATION - RAIN 
Average Number of Rainy Days
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days11710910101210111098910

Average Number of Days With Thunderstorms
Years on Record: 33  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days28------124665211---

Most Rain Reported in a Month
Years on Record: 33  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
in.55.46.65.87.67.310.38.67.210.711.39.27.86.7

Least Recorded Rainfall
Years on Record: 33  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
in.28.90.40.210.30.80.50.90.80.6---0.20.4



PRECIPITATION - SNOW 
Average Snowfall
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
in.227.37.62.80.3------------------0.53.5

Average Number of Days With Snow
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days9.83.52.61.50.3------------------0.31.6

Avg. No. of Days w/Snow Above 1in/2.5cm
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days5.61.91.60.90.1------------------0.11

Avg. No. of Days w/Snow Above 3in/7.5cm
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days2.610.90.3---------------------0.10.3

Avg. No. of Days w/Snow Above 5in/12.7cm
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days0.80.20.30.1------------------------0.2

Avg. No. of Days w/Snowfall Above 10in/25cm
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days0.30.10.1---------------------------0.1

Avg. # of Days w/Snow Depth Above 1in/2.5cm
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days15.75.55.51.60.1------------------0.22.8

Avg. # of Days w/Snow Depth Above 3in/7.5cm
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days8.52.93.10.6---------------------0.11.8

Avg. # of Days w/Snow Depth Above 5in/12.7cm
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days4.21.61.70.3------------------------0.6

Avg. # of Days w/Snow Depth Above 10in/25cm
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days1.60.60.80.1------------------------0.1



HUMIDITY 
Average Relative Humidity
Years on Record: 20  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
%67.563.761.161.36268.971.871.171.772.772.16866.2

Average Morning Relative Humidity
Years on Record: 33  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
%82777778778284868989888278

Average Evening Relative Humidity
Years on Record: 33  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
%53575249465354545555525457

Average Dew Point
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
F43.922.224.230.340.351.861.565.364.157.645.935.226.5



DEGREE DAYS 
Heating Degree Days
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days471798680664733513015---256298560882

Cooling Degree Days
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days1178------31772237363324141192---

Growing Degree Days
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days378099531814106728287875362186414



BAROMETER 
Average Sea Level Pressure
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
InHg30.130.130.130303030303030.130.130.130.1



SKY CONDITIONS 
Average Length of Day
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Hours12.710.311.212.413.714.815.415.114.112.811.610.510

Average Number of Days With Fog
Years on Record: 33  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days170131012101416192018141212

Average Number of Clear Days
Years on Record: 31  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days917877768891177

Average Number of Cloudy Days
Years on Record: 31  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days168171416141412121212121517

Average Number of Partly Cloudy Days
Years on Record: 31  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
Days1067689101211119887

Average Percent Chance - Clear Skies
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
%18.518.818.820.518.916.113.713.115.521.425.12118.6

Average Percent Chance - Scattered Clouds
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
%10.58.28.68.2910.513.71514.511.39.68.98.4

Average Percent Chance - Few Clouds
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
%14.112.412.712.612.514.315.816.716.315.214.813.212.3

Average Percent Chance - Broken Clouds
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
%20.317.116.716.819.120.92627.424.620.118.418.817.7

Average Percent Chance - Overcast Skies
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
%36.643.643.141.940.538.330.827.928.931.932.138.143

Average Total Sky Cover
Years on Record: 20  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
%5963.161.461.660.859.85958.15654.85160.362

Average Opaque Sky Cover
Years on Record: 20  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
%53.158.155.756.754.353.251.752.949.649.645.354.356.7



WIND 
Average Wind Speed
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
mph77.888.68.176.35.95.666.377.3

Highest Reported Hourly Wind Speed
Years on Record: 49  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
mph59394644464059484337394341

Average Percent Chance - Calm Winds
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
%12.810.810.48.69.911.313.214.615.414.915.914.913.6

Average Primary Wind Direction
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
°306360360358327.1287.1278274.3233.6209.4271.8355.9360

Average Secondary Wind Direction
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
°212.7183.6140.1110.3215.1261.6280.1268.9215.6249.1233.5206.4184.4

Average Wind Vector Direction
Years on Record: 30  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
°275.6301.4303.8305.6291.5249.4236.8240.4247.7259286.1290.2296.7



SOLAR RADIATION 
Average Daily Solar Radiation - Global
Years on Record: 22  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
kWh/m23.922.83.74.75.35.65.654.33.42.21.7

Average Daily Solar Radiation - Diffuse
Years on Record: 22  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
kWh/m21.60.81.11.522.32.52.42.11.71.20.90.7

Average Daily Solar Radiation - Reflected
Years on Record: 22  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
kWh/m24.33.13.74.34.74.94.954.84.74.53.42.9

Average Daily Solar Radiation - Direct
Years on Record: 22  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
kWh/m24.23.13.74.14.44.74.84.94.64.64.63.52.9

Maximum Daily Solar Radiation - Global
Years on Record: 22  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
kWh/m23.922.83.74.75.35.65.654.33.42.21.7

Maximum Daily Solar Radiation - Diffuse
Years on Record: 22  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
kWh/m21.70.81.21.62.12.42.52.52.21.71.30.90.8

Maximum Daily Solar Radiation - Reflected
Years on Record: 22  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
kWh/m253.74.65.35.45.85.75.45.45.55.74.33.4

Maximum Daily Solar Radiation - Direct
Years on Record: 22  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
kWh/m25.43.95.25.55.66.46.65.85.666.44.83.6

Minimum Daily Solar Radiation - Global
Years on Record: 22  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
kWh/m23.21.72.2343.54.754.43.72.71.61.3

Minimum Daily Solar Radiation - Diffuse
Years on Record: 22  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
kWh/m21.50.811.41.92.22.32.321.510.80.7

Minimum Daily Solar Radiation - Reflected
Years on Record: 22  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
kWh/m23.42.52.83.443.34.24.54.23.93.42.22

Minimum Daily Solar Radiation - Direct
Years on Record: 22  Chart This
 ANNUAL  JAN  FEB  MAR  APR  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC 
kWh/m22.82.32.42.73.323.43.93.63.431.91.8




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