Washington-Dulles Airport, D.C.
H
I S T O R I C A L
W
E A T H E R
D
A T A
Average Temperature
Year
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
°F
53.8
30.6
33.6
43.2
52.7
62.2
71
75.6
74.2
67.1
55.1
45.4
35.4
°C
12
0
0
6
11
16
21
24
23
19
12
7
1
Years Charted: 30
Source:
National Weather Service, San Francisco
Results based on data collected from 1961 - 1990
Average High Temperature
Year
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
°F
65.1
40.1
43.8
54.6
65.1
74.3
82.8
87
85.5
78.9
67.7
56.7
45
°C
18
4
6
12
18
23
28
30
29
26
19
13
7
Years Charted: 30
Source:
National Weather Service, San Francisco
Results based on data collected from 1961 - 1990
Average Low Temperature
Year
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
°F
42.5
21
23.3
31.8
40.3
50
59.2
64.1
62.8
55.4
42.4
34.2
25.8
°C
5
-6
-4
0
4
10
15
17
17
13
5
1
-3
Years Charted: 30
Source:
National Weather Service, San Francisco
Results based on data collected from 1961 - 1990
Highest Recorded Temperature
Year
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
°F
104
75
79
89
92
97
100
104
104
99
90
84
78
°C
40
23
26
31
33
36
37
40
40
37
32
28
25
Years Charted: 31
Source:
National Weather Service, San Francisco
Results based on data collected through 1993
Lowest Recorded Temperature
Year
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
°F
-18
-18
-14
-1
17
28
36
41
38
30
15
9
-4
°C
-27
-27
-25
-18
-8
-2
2
5
3
-1
-9
-12
-20
Years Charted: 31
Source:
National Weather Service, San Francisco
Results based on data collected through 1993
Mean Number of Days Below 32°F/0°C
Total
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
Days
115
26
23
17
6
---
0
0
0
---
5
14
23
Years Charted: 31
Source:
National Weather Service, San Francisco
Results based on data collected through 1993
Average Precipitation
Year
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
in.
40.24
2.7
2.81
3.17
3.11
4.02
3.92
3.49
3.94
3.36
3.2
3.3
3.22
mm
1022
68
71
80
78
102
99
88
100
85
81
83
81
Years Charted: 30
Source:
National Weather Service, San Francisco
Results based on data collected from 1961 - 1990
Average Snowfall
Year
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
in.
22.6
7.2
6.8
3.3
0.3
0
0
0
0
0
0
1.1
3.9
mm
574
182
172
83
7
0
0
0
0
0
0
27
99
Years Charted: 31
Source:
National Weather Service, San Francisco
Results based on data collected through 1993
Average Wind Speed
Year
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
mph
7.4
8.2
8.6
9.1
8.8
7.4
6.8
6.2
5.9
6.2
6.6
7.7
7.8
km/h
11
13
13
14
14
11
10
9
9
9
10
12
12
Years Charted: 31
Source:
National Weather Service, San Francisco
Results based on data collected through 1993
Average Days of Precipitation
Total
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
Days
117
10
9
10
10
12
10
11
10
9
8
9
10
Years Charted: 30
Source:
National Weather Service, San Francisco
Results based on data collected through 1993
Mean Number of Cloudy Days
Total
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
Days
168
17
14
16
14
14
12
12
12
12
12
15
17
Years Charted: 31
Source:
National Weather Service, San Francisco
Results based on data collected through 1993
Mean Number of Partly Cloudy Days
Total
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
Days
106
7
6
8
9
10
12
11
11
9
8
8
7
Years Charted: 31
Source:
National Weather Service, San Francisco
Results based on data collected through 1993
Mean Number of Clear Days
Total
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
Days
91
7
8
7
7
7
6
8
8
9
11
7
7
Years Charted: 31
Source:
National Weather Service, San Francisco
Results based on data collected through 1993
Average Morning Relative Humidity
Year
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
%
83
77
78
78
77
83
84
86
89
90
88
83
79
Years Charted: 24
Source:
National Weather Service, San Francisco
Results based on data collected through 1993
Average Afternoon Relative Humidity
Year
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
%
55
58
54
52
48
55
55
55
56
56
54
55
58
Years Charted: 24
Source:
National Weather Service, San Francisco
Results based on data collected through 1993
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