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WA Cloud Cover

The cloud cover data below was derived from observations of hourly cloud cover from 25 weather stations, which are often located at an airport. Prior to the inception of the Automated Surface Observing System (ASOS) and the Automated Weather Observing System in 1980's, cloud cover was determined by a human observer. The ASOS/AWOS systems, measure cloud cover in oktas (8th's) using a ceilometer which is accurate to 12,000 ft.

The tables below are a monthly average from 1973-2000* of hourly cloud cover between sunrise and sunset that show the average cloud cover (in oktas) and the mean number of days clear, partly cloudy, and cloudy. Clear denotes an average sky cover of 0-2 oktas, partly cloudy denotes an average sky cover of 3-5 oktas and cloudy denotes an average sky cover of 6-8 oktas.

For each station, daily and monthly cloud cover data is also available for download. Information on the format of these files is available here and a station list is available here.

* In most cases cloud cover data is not available prior to 1973 and few stations may have shorter records.

 

Select Station:  



Bellingham International Airport  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.5
4.0
4.3
22.7
2
6.2
3.8
5.2
19.5
3
6.0
4.1
7.6
19.3
4
5.9
4.1
8.9
17.1
5
5.5
4.4
11.6
15.0
6
5.4
5.0
10.5
14.5
7
4.3
9.1
11.9
10.0
8
4.5
9.6
11.5
9.9
9
4.5
8.6
10.0
11.3
10
5.9
4.6
7.8
18.6
11
6.5
3.2
4.9
21.9
12
6.4
3.5
5.9
21.6

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Bremerton National Airport  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.4
2.5
5.5
23.1
2
6.1
2.3
7.1
19.1
3
6.1
2.7
8.5
19.8
4
5.0
2.5
10.5
17.1
5
5.9
2.8
12.9
15.3
6
4.6
3.7
12.2
14.1
7
4.6
6.3
10.6
14.1
8
3.9
6.2
12.8
12.0
9
2.8
11.6
8.5
9.9
10
5.9
5.1
9.3
16.5
11
6.7
1.3
8.1
20.6
12
6.7
2.2
6.8
22.1

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Ephrata Airport  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.4
3.4
6.8
20.9
2
5.9
3.9
7.4
17.3
3
5.5
4.6
11.6
14.8
4
5.3
4.8
12.3
12.9
5
5.0
6.4
13.5
11.2
6
4.6
7.2
14.1
8.7
7
3.2
15.1
10.8
5.0
8
3.4
14.5
11.3
5.2
9
3.5
13.5
10.1
6.4
10
4.6
9.0
10.5
11.5
11
6.0
4.1
8.1
17.7
12
6.3
3.6
7.1
20.4

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Fairchild Air Force Base  (1971-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.6
2.6
6.2
22.3
2
6.3
2.9
7.1
18.5
3
6.0
3.1
10.4
17.5
4
5.8
3.3
11.1
15.6
5
5.5
4.1
14.0
12.9
6
5.1
4.9
14.5
10.5
7
3.8
12.5
12.7
5.8
8
3.7
12.7
12.7
5.6
9
4.1
11.1
11.2
7.7
10
5.1
6.6
11.3
13.1
11
6.5
2.1
7.1
20.8
12
6.6
2.6
6.2
22.2

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Felts Field  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.6
2.9
5.7
22.4
2
6.4
3.3
5.4
19.9
3
6.0
3.9
8.9
18.2
4
5.8
3.9
10.1
15.9
5
5.4
4.4
13.1
13.5
6
5.0
6.3
12.6
11.2
7
3.6
12.9
11.3
6.7
8
3.7
13.2
11.2
6.6
9
3.9
11.8
10.1
8.1
10
5.0
7.8
8.7
14.5
11
6.7
1.9
6.3
21.8
12
6.6
2.9
5.7
22.4

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Hanford  (1985-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.5
3.2
7.3
20.5
2
6.0
4.5
6.8
17.2
3
5.3
5.5
10.9
14.6
4
5.3
5.5
11.8
12.7
5
4.8
6.9
12.8
11.2
6
4.2
9.1
13.2
7.6
7
2.8
16.8
10.2
4.0
8
2.6
17.9
9.6
3.5
9
2.5
16.1
9.3
4.6
10
4.2
10.1
11.1
9.8
11
5.8
4.8
8.3
16.8
12
6.4
4.1
5.9
21.0

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Moses Lake/Grant County Airport  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.3
3.4
7.6
20.0
2
5.7
4.6
7.7
16.2
3
5.3
6.1
10.5
14.5
4
5.1
6.4
11.3
12.3
5
4.6
7.7
12.8
10.5
6
4.1
9.8
12.3
7.9
7
3.0
15.9
10.4
4.7
8
3.0
16.2
9.9
5.0
9
3.1
15.2
9.2
5.6
10
4.2
10.7
10.3
10.0
11
5.5
4.7
8.7
16.6
12
5.8
4.7
6.3
20.0

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Olympia Airport  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.8
2.2
5.1
23.7
2
6.7
1.9
5.5
21.2
3
6.3
2.6
9.0
19.5
4
6.0
3.1
9.9
17.1
5
5.9
3.5
10.8
16.7
6
5.5
4.7
11.0
14.3
7
4.6
8.4
11.3
11.4
8
4.5
8.3
12.5
10.3
9
4.6
7.8
12.0
10.2
10
5.9
3.3
10.6
17.1
11
6.7
1.8
6.0
22.2
12
6.8
2.2
5.2
23.7

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Omak  (1998-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
5.6
6.3
8.4
16.3
2
4.3
10.5
7.5
10.5
3
3.3
14.0
11.5
5.5
4
1.2
21.4
7.6
1.0
5
2.6
16.7
11.7
2.7
6
2.1
19.3
10.3
0.3
7
1.0
26.2
4.4
0.3
8
0.6
28.2
2.1
0.7
9
1.1
23.7
6.3
0.0
10
1.9
20.4
8.0
2.6
11
5.1
11.2
7.6
11.2
12
5.4
9.0
7.6
14.4

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Pasco  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.4
3.1
6.2
21.6
2
6.0
3.9
7.2
17.3
3
5.2
6.9
10.1
14.0
4
4.9
6.8
11.4
11.8
5
4.5
8.5
12.7
9.8
6
3.9
11.0
12.3
6.6
7
2.5
18.4
8.7
3.9
8
2.7
18.0
8.4
4.6
9
2.7
16.6
8.5
4.8
10
4.1
11.6
9.3
10.1
11
5.9
4.2
8.0
17.8
12
6.2
4.4
5.6
21.0

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Pullman/Moscow Regional Airport  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.4
3.5
6.4
21.1
2
5.7
4.6
7.6
16.3
3
5.4
5.5
9.0
16.5
4
5.5
4.9
10.2
14.8
5
4.8
6.2
11.5
13.3
6
4.5
8.4
11.0
10.7
7
2.7
15.7
9.7
5.6
8
2.4
16.7
9.8
4.5
9
3.0
15.6
8.1
6.3
10
4.6
9.0
9.2
12.8
11
5.9
4.3
7.0
18.7
12
6.1
4.4
6.1
20.5

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Quillayute State Airport  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.4
4.1
5.0
22.0
2
6.3
3.9
5.3
19.3
3
6.2
3.5
8.1
19.4
4
6.1
3.6
8.1
18.3
5
6.1
3.1
10.0
18.0
6
6.1
3.3
9.1
17.6
7
5.5
5.3
11.0
14.7
8
5.2
6.1
10.9
13.9
9
4.8
8.0
10.2
11.8
10
5.7
5.1
9.6
16.3
11
6.4
3.1
6.6
20.3
12
6.4
4.2
5.7
21.0

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Seattle Boeing Field  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.6
2.9
5.2
22.8
2
6.5
2.9
4.6
21.0
3
6.3
3.5
7.5
20.0
4
6.2
3.0
8.4
18.6
5
5.8
4.2
9.4
17.4
6
5.6
4.6
9.8
15.6
7
4.5
9.6
10.0
11.3
8
4.5
9.2
10.4
11.4
9
4.7
8.4
10.3
11.3
10
6.0
3.9
8.6
18.6
11
6.8
1.8
5.5
22.7
12
6.7
2.5
5.5
22.9

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Seattle-Tacoma International Airport  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.6
2.7
5.6
22.7
2
6.5
2.7
5.8
20.0
3
6.3
3.0
7.9
20.1
4
6.2
2.3
10.6
17.1
5
5.8
3.8
11.0
16.2
6
5.6
4.0
11.2
14.8
7
4.6
8.8
11.6
10.6
8
4.5
7.9
13.0
10.1
9
4.7
8.2
11.5
10.3
10
6.0
3.5
10.3
17.1
11
6.7
2.0
6.1
21.9
12
6.7
2.2
5.9
22.9

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Shelton/Sanderson Field  (1998-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.0
5.1
8.3
17.6
2
5.6
5.2
10.4
13.0
3
5.0
6.3
13.1
11.6
4
3.4
12.4
13.4
4.1
5
4.8
6.0
15.5
9.5
6
4.8
7.6
9.7
12.7
7
4.0
10.7
12.1
8.2
8
3.7
11.2
13.7
6.1
9
2.8
16.2
8.5
5.3
10
4.3
9.8
11.3
9.8
11
6.1
6.5
8.4
15.2
12
6.5
6.4
6.1
18.5

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Snohomish Co/Paine Field  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.4
3.4
5.4
22.2
2
6.4
3.5
4.5
20.5
3
6.3
3.7
6.8
20.5
4
6.2
3.1
7.4
19.5
5
5.9
4.3
9.1
17.6
6
5.8
4.9
9.3
15.9
7
4.5
9.5
9.4
12.1
8
4.2
9.6
10.1
11.3
9
4.7
9.2
8.9
11.9
10
5.9
4.7
7.4
18.9
11
6.6
2.7
4.7
22.6
12
6.6
3.0
4.9
23.0

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Spokane International Airport  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.7
2.5
5.7
22.8
2
6.4
2.9
5.9
19.7
3
6.0
3.7
9.7
17.7
4
5.7
3.6
11.3
15.1
5
5.3
5.1
13.3
12.7
6
4.9
5.9
13.2
10.9
7
3.6
13.2
11.6
6.2
8
3.4
12.9
12.3
5.8
9
3.8
11.8
10.4
7.8
10
5.0
7.3
10.0
13.7
11
6.6
2.4
6.5
21.1
12
6.7
2.5
5.4
23.1

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Stampede Pass  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.8
3.5
5.1
22.4
2
6.3
3.7
5.2
19.6
3
6.2
3.8
7.2
20.1
4
6.1
4.6
6.6
18.8
5
5.6
4.9
8.2
17.9
6
5.6
5.7
8.1
16.2
7
4.5
11.3
8.9
10.7
8
3.4
12.8
9.6
8.6
9
3.9
12.5
7.4
10.2
10
5.0
7.9
7.7
15.5
11
6.8
3.3
4.8
21.9
12
6.6
3.6
5.3
22.1

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Tacoma Narrows  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.4
2.4
5.8
22.8
2
6.1
3.1
6.4
19.1
3
6.0
3.7
7.9
19.4
4
5.9
3.2
10.1
16.8
5
5.5
4.8
10.7
15.5
6
5.4
5.7
10.3
14.0
7
4.7
9.7
10.9
10.4
8
4.2
9.2
12.3
9.5
9
4.1
9.8
11.0
9.2
10
5.9
4.0
9.9
17.1
11
6.5
2.5
6.3
21.2
12
6.6
2.4
5.8
22.9

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The Dalles Municipal Airport  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.6
2.5
6.6
21.9
2
6.2
3.1
6.8
18.6
3
5.3
5.7
10.5
14.8
4
5.2
5.8
11.4
12.8
5
4.4
9.0
13.2
8.8
6
3.8
11.2
11.4
7.4
7
2.6
17.6
10.0
3.4
8
2.7
17.4
9.5
4.1
9
2.9
16.3
8.9
4.9
10
4.3
9.9
10.9
10.3
11
6.3
2.7
7.5
19.8
12
6.5
2.7
6.0
22.3

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Toledo-Winlock Memorial Field  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.7
3.0
4.3
23.7
2
6.8
2.9
4.3
21.4
3
6.3
3.6
5.9
21.4
4
6.0
2.8
7.8
19.4
5
5.9
4.7
8.4
17.9
6
5.6
5.9
9.4
14.7
7
4.3
9.8
9.1
12.1
8
5.0
8.9
9.9
12.2
9
4.1
10.1
8.6
11.4
10
6.3
4.7
8.3
18.0
11
7.0
2.2
4.0
23.8
12
7.0
2.4
3.9
24.7

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Walla Walla Airport  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.9
1.6
5.6
23.8
2
6.5
2.7
6.5
19.3
3
5.9
4.5
8.9
17.5
4
5.6
4.9
10.3
14.8
5
5.2
6.0
12.2
12.8
6
4.5
8.2
12.6
9.2
7
3.1
15.6
9.9
5.5
8
3.1
15.2
10.6
5.2
9
3.5
13.7
9.6
6.8
10
4.7
8.8
9.8
12.4
11
6.5
2.6
6.3
21.2
12
6.7
2.2
5.7
23.1

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Wenatchee/Pangborn Airport  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.3
4.1
8.3
18.5
2
5.6
4.4
9.0
15.1
3
5.0
6.6
11.6
12.9
4
4.8
7.3
12.2
10.5
5
4.3
8.1
15.0
7.9
6
3.9
10.7
12.9
6.4
7
2.8
16.6
10.3
4.1
8
2.8
16.8
9.8
4.4
9
2.8
16.4
8.7
4.8
10
3.8
12.3
9.7
9.0
11
5.7
4.5
8.8
16.6
12
6.2
4.4
7.2
19.4

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Whidbey Island Naval Air Station  (1971-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.4
2.8
8.0
20.2
2
6.3
2.3
8.3
17.9
3
6.1
2.0
11.2
17.8
4
6.0
2.1
11.7
16.2
5
5.8
2.3
14.2
14.5
6
5.8
2.3
14.0
13.7
7
4.9
5.6
15.4
10.0
8
4.8
5.1
16.4
9.5
9
4.8
6.4
13.7
9.9
10
5.9
2.9
11.2
16.9
11
6.5
1.8
8.6
19.6
12
6.5
1.9
8.6
20.5

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Yakima Air Terminal  (1973-2000)

Download data: Daily Cloud Cover   Monthly Cloud Cover

Month
Avg. Cloud Cover
Days Clear
Days Partly Cloudy
Days Cloudy
1
6.0
4.3
7.4
19.3
2
5.7
4.9
7.6
16.0
3
5.1
7.1
10.8
13.1
4
4.8
7.3
11.5
11.2
5
4.4
8.6
13.5
8.9
6
3.9
11.3
11.9
6.8
7
2.6
17.3
10.1
3.6
8
2.7
17.3
9.7
3.9
9
2.7
16.4
9.2
4.5
10
3.9
11.7
10.2
9.1
11
5.6
5.5
8.7
15.8
12
6.0
4.9
7.4
18.7

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Related Links

- MODIS Cloud Fraction
- Average Percent of Possible Sunshine