Anacortes
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Anacortes clear sky chart from 2005-11-05 to 2018-01-12.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
41%
14996
9%
48263
9%
14967
42%
14967
14%
36291

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
31%
805
9%
2852
9%
801
32%
801
8%
2360
January16th to endNight
33%
771
8%
2682
8%
771
34%
771
10%
2135
February1st to 15thNight
32%
698
6%
2288
5%
698
34%
698
9%
1852
February16th to endNight
32%
632
11%
2029
10%
632
35%
632
11%
1590
March1st to 15thNight
24%
720
4%
2067
3%
720
26%
720
9%
1749
March16th to endNight
27%
768
5%
2068
3%
768
28%
768
9%
1760
April1st to 15thNight
32%
719
5%
1799
3%
719
33%
719
12%
1503
April16th to endNight
38%
526
8%
1606
8%
526
39%
526
13%
1263
May1st to 15thNight
53%
359
13%
1439
20%
359
55%
359
19%
915
May16th to endNight
50%
375
5%
1496
9%
374
51%
374
12%
1073
June1st to 15thNight
47%
360
3%
1278
3%
360
47%
360
16%
906
June16th to endNight
51%
360
6%
1260
5%
360
52%
360
16%
878
July1st to 15thNight
70%
340
11%
1190
11%
340
72%
340
35%
632
July16th to endNight
75%
376
16%
1369
25%
354
76%
354
36%
664
August1st to 15thNight
76%
434
15%
1507
20%
432
77%
432
38%
763
August16th to endNight
70%
627
21%
1773
18%
627
70%
627
38%
1013
September1st to 15thNight
74%
720
21%
1800
13%
720
75%
720
43%
1084
September16th to endNight
53%
716
17%
1974
14%
716
53%
716
22%
1402
October1st to 15thNight
47%
720
11%
2160
11%
720
49%
720
20%
1518
October16th to endNight
36%
768
8%
2379
9%
768
38%
768
12%
1878
November1st to 15thNight
22%
760
5%
2657
5%
760
23%
760
7%
2256
November16th to endNight
24%
780
5%
2730
3%
780
27%
780
8%
2253
December1st to 15thNight
34%
782
7%
2740
7%
782
35%
782
10%
2184
December16th to endNight
19%
880
5%
3120
4%
880
21%
880
6%
2660

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
19%8%36%5%35%446%32%
49098
Night
23%8%36%5%34445%30%
48420
Cloud CoverDay
21%8%36%5%34446%31%
49098
Night
25%8%35%5%24345%30%
48423
TransparencyDay
53%9%14%15%6%1
48758
Night
56%7%13%15%6%1
48264
SeeingDay
22%6%20%27%18%4
6366
Night
29%5%16%23%20%4
15003

By Month

Percentage Cloud Cover NW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
32%12%47%6%2433318%
1330
16th to endDay
32%9%5%8%6%25%5%3415%
1537
February1st to 15thDay
27%11%48%6%35%445%16%
1576
16th to endDay
24%11%47%5%35%45%6%21%
1445
March1st to 15thDay
29%12%5%8%7%35%33415%
1892
16th to endDay
24%12%48%7%36%435%18%
2155
April1st to 15thDay
22%9%46%6%36%5%6%7%20%
2149
16th to endDay
20%8%47%6%45%5%6%7%23%
2352
May1st to 15thDay
16%5%35%6%36%5%5%7%34%
2511
16th to endDay
18%7%36%6%2445%7%30%
2615
June1st to 15thDay
16%6%35%5%35%45%7%35%
2680
16th to endDay
14%7%245%36%5%5%7%36%
2700
July1st to 15thDay
7%423423346%56%
2700
16th to endDay
8%313322346%60%
2705
August1st to 15thDay
7%424422348%54%
2442
16th to endDay
9%41432446%8%49%
2429
September1st to 15thDay
9%415%324436%53%
2160
16th to endDay
18%9%26%435%446%34%
1985
October1st to 15thDay
21%10%36%42445%6%29%
1800
16th to endDay
28%10%47%6%24346%20%
1843
November1st to 15thDay
35%9%36%6%35%33317%
1528
16th to endDay
30%12%48%6%25%44316%
1560
December1st to 15thDay
27%11%47%6%35%44421%
1548
16th to endDay
31%12%47%6%25%34415%
1456
January1st to 15thNight
34%11%25%43433421%
2852
16th to endNight
29%10%36%5%3445%7%20%
2682
February1st to 15thNight
28%12%47%433336%21%
2276
16th to endNight
25%10%36%6%345%4424%
2029
March1st to 15thNight
30%10%46%6%35%44418%
2067
16th to endNight
27%12%5%7%5%34445%18%
2064
April1st to 15thNight
21%10%47%7%445%6%6%21%
1799
16th to endNight
24%10%36%5%35%346%24%
1606
May1st to 15thNight
16%5%145%2345%8%41%
1439
16th to endNight
15%7%37%6%35%46%9%30%
1496
June1st to 15thNight
17%6%37%5%44336%35%
1278
16th to endNight
14%6%26%5%45%46%7%35%
1260
July1st to 15thNight
6%424312235%62%
1260
16th to endNight
7%21231334466%
1464
August1st to 15thNight
6%313323346%60%
1515
16th to endNight
7%31342335%8%55%
1773
September1st to 15thNight
7%313213436%61%
1800
16th to endNight
17%5%26%7%34446%37%
1974
October1st to 15thNight
18%6%36%6%3433440%
2160
16th to endNight
27%7%36%5%345%5%6%24%
2379
November1st to 15thNight
35%9%37%5%3433417%
2657
16th to endNight
31%10%46%5%35%43420%
2730
December1st to 15thNight
27%10%46%425%446%22%
2740
16th to endNight
33%13%46%5%2433319%
3120

Percentage Cloud Cover SW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
37%10%46%5%2432419%
1330
16th to endDay
34%8%37%7%2444418%
1537
February1st to 15thDay
28%13%47%6%34446%16%
1576
16th to endDay
26%10%36%5%4445%5%22%
1445
March1st to 15thDay
31%13%5%8%5%3433416%
1892
16th to endDay
27%11%36%8%35%445%18%
2155
April1st to 15thDay
23%10%47%7%35%5%5%7%19%
2149
16th to endDay
21%8%37%7%345%6%8%21%
2352
May1st to 15thDay
18%6%26%5%36%5%46%34%
2511
16th to endDay
21%7%35%5%3445%7%29%
2615
June1st to 15thDay
20%6%36%5%34446%33%
2680
16th to endDay
17%6%35%5%35%5%6%7%34%
2700
July1st to 15thDay
8%424423346%55%
2700
16th to endDay
10%313323435%58%
2705
August1st to 15thDay
8%5%14313347%56%
2442
16th to endDay
10%415%33345%8%48%
2429
September1st to 15thDay
10%5%2432235%6%53%
2160
16th to endDay
19%7%35%424447%34%
1985
October1st to 15thDay
22%8%445%345%6%6%28%
1800
16th to endDay
30%9%37%5%24446%20%
1843
November1st to 15thDay
37%9%36%5%35%43416%
1528
16th to endDay
34%9%5%6%6%2344416%
1560
December1st to 15thDay
29%10%47%6%24345%21%
1548
16th to endDay
34%13%36%5%34435%16%
1456
January1st to 15thNight
36%10%35%32423421%
2851
16th to endNight
31%9%345%24346%22%
2682
February1st to 15thNight
30%11%46%424436%21%
2276
16th to endNight
27%10%36%5%35%44425%
2029
March1st to 15thNight
33%9%35%5%35%45%5%17%
2067
16th to endNight
31%11%46%6%43445%17%
2068
April1st to 15thNight
22%11%49%6%345%5%6%20%
1799
16th to endNight
26%10%46%434446%24%
1606
May1st to 15thNight
17%5%245%2335%8%40%
1439
16th to endNight
17%8%36%6%25%5%5%7%29%
1496
June1st to 15thNight
20%7%36%445%336%34%
1278
16th to endNight
15%6%25%6%35%5%5%7%34%
1260
July1st to 15thNight
7%422323336%60%
1260
16th to endNight
9%11331223464%
1464
August1st to 15thNight
7%31231235%6%61%
1515
16th to endNight
8%414423447%55%
1773
September1st to 15thNight
7%313313345%60%
1800
16th to endNight
18%7%26%5%34446%37%
1974
October1st to 15thNight
19%6%36%5%34335%38%
2160
16th to endNight
28%8%25%5%35%5%46%23%
2379
November1st to 15thNight
38%10%46%5%2334417%
2657
16th to endNight
33%10%36%6%3434419%
2730
December1st to 15thNight
29%10%36%424346%23%
2740
16th to endNight
36%12%36%5%2433318%
3120

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
70%6%6%10%5%
1330
16th to endDay
69%8%9%8%21
1537
February1st to 15thDay
69%9%8%7%32
1576
16th to endDay
63%8%9%12%5%
1445
March1st to 15thDay
73%6%9%8%1
1892
16th to endDay
69%7%11%9%
2155
April1st to 15thDay
64%10%13%9%1
2149
16th to endDay
60%9%14%11%3
2352
May1st to 15thDay
50%10%15%16%6%
2511
16th to endDay
54%13%17%12%2
2619
June1st to 15thDay
51%9%19%13%5%
2680
16th to endDay
49%11%18%17%3
2700
July1st to 15thDay
30%8%17%27%12%3
2541
16th to endDay
27%7%17%32%12%1
2537
August1st to 15thDay
30%9%19%28%10%2
2425
16th to endDay
33%8%19%27%8%1
2429
September1st to 15thDay
31%9%16%21%19%2
2160
16th to endDay
50%8%15%16%8%1
1985
October1st to 15thDay
52%9%16%15%6%
1800
16th to endDay
64%9%11%10%4
1843
November1st to 15thDay
72%7%9%6%21
1528
16th to endDay
69%8%7%8%4
1560
December1st to 15thDay
66%7%7%10%6%
1548
16th to endDay
71%7%8%7%31
1456
January1st to 15thNight
68%6%6%11%5%
2852
16th to endNight
63%7%10%12%41
2682
February1st to 15thNight
65%6%12%8%42
2288
16th to endNight
61%7%9%15%5%
2029
March1st to 15thNight
69%6%11%9%2
2067
16th to endNight
70%6%11%11%
2068
April1st to 15thNight
63%9%12%12%3
1799
16th to endNight
62%5%13%14%3
1606
May1st to 15thNight
42%8%17%21%9%
1440
16th to endNight
52%9%19%13%3
1496
June1st to 15thNight
53%418%16%41
1278
16th to endNight
49%8%16%20%21
1260
July1st to 15thNight
28%5%17%29%14%4
1190
16th to endNight
25%416%31%17%4
1369
August1st to 15thNight
24%6%21%29%13%3
1507
16th to endNight
29%5%19%30%11%3
1773
September1st to 15thNight
26%7%16%25%19%5%
1800
16th to endNight
47%7%12%22%8%1
1974
October1st to 15thNight
50%414%20%9%
2160
16th to endNight
59%8%13%12%5%
2379
November1st to 15thNight
72%6%9%7%22
2657
16th to endNight
67%8%10%7%5%
2730
December1st to 15thNight
63%8%11%11%6%
2740
16th to endNight
72%7%8%7%31
3120

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
23%412%20%21%17%
82
16th to endDay
52%6%17%10%12%1
82
February1st to 15thDay
34%8%25%16%13%1
236
16th to endDay
35%9%20%18%14%1
215
March1st to 15thDay
43%14%22%13%5%
270
16th to endDay
37%12%21%19%6%1
288
April1st to 15thDay
26%10%24%22%13%3
269
16th to endDay
20%12%26%27%11%2
270
May1st to 15thDay
22%6%26%26%16%1
288
16th to endDay
20%5%17%30%18%7%
330
June1st to 15thDay
20%421%35%15%2
475
16th to endDay
15%425%32%19%1
495
July1st to 15thDay
8%320%37%25%5%
475
16th to endDay
9%116%36%29%6%
374
August1st to 15thDay
10%110%34%32%11%
315
16th to endDay
7%315%34%30%8%
332
September1st to 15thDay
15%120%31%26%5%
315
16th to endDay
20%418%29%20%5%
315
October1st to 15thDay
27%6%21%24%15%4
315
16th to endDay
36%8%16%19%15%3
259
November1st to 15thDay
46%13%23%14%2
90
16th to endDay
36%13%22%11%6%10%
90
December1st to 15thDay
43%8%12%10%15%10%
90
16th to endDay
40%8%21%19%6%3
96
January1st to 15thNight
40%9%14%15%18%1
805
16th to endNight
37%6%17%20%15%2
771
February1st to 15thNight
36%5%16%25%12%2
704
16th to endNight
33%7%19%22%15%2
632
March1st to 15thNight
38%11%20%17%10%1
720
16th to endNight
36%8%19%24%8%2
768
April1st to 15thNight
28%7%18%26%15%3
719
16th to endNight
30%417%29%15%2
526
May1st to 15thNight
21%314%30%26%3
360
16th to endNight
21%214%27%28%4
375
June1st to 15thNight
24%219%26%24%3
360
16th to endNight
17%415%32%26%4
360
July1st to 15thNight
10%211%32%37%5%
340
16th to endNight
10%9%29%42%7%
376
August1st to 15thNight
9%15%20%48%14%
434
16th to endNight
11%19%27%38%11%
627
September1st to 15thNight
10%18%29%37%13%
720
16th to endNight
23%213%25%26%8%
716
October1st to 15thNight
24%415%24%25%5%
720
16th to endNight
34%6%13%22%17%5%
768
November1st to 15thNight
41%8%20%21%7%
760
16th to endNight
38%9%19%16%11%4
780
December1st to 15thNight
36%5%14%24%16%2
782
16th to endNight
41%9%24%17%7%
880
Page generated at 2018-01-12 19:01:32. Version ac04

Copyright 2018 A. Danko


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