Anacortes
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Anacortes clear sky chart from 2005-11-06 to 2024-03-01.

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
39%
22723
6%
80981
5%
22609
40%
22609
7%
67645

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 10thNight
22%
844
2%
4716
2%
816
23%
816
1%
4301
January11th to 20thNight
30%
804
11%
4538
4%
790
32%
790
3%
3486
January21st to endNight
30%
835
3%
4817
4%
814
31%
814
3%
4360
February1st to 10thNight
27%
760
2%
2470
2%
760
29%
760
5%
2186
February11th to 20thNight
30%
740
5%
2404
5%
740
31%
740
7%
2046
February21st to endNight
27%
628
6%
2001
4%
628
30%
628
5%
1772
March1st to 10thNight
30%
722
4%
2116
3%
722
31%
722
7%
1843
March11th to 20thNight
30%
720
5%
1980
3%
720
33%
720
6%
1759
March21st to endNight
29%
792
3%
2113
1%
792
29%
792
6%
1893
April1st to 10thNight
32%
720
2%
1800
1%
720
32%
720
6%
1609
April11th to 20thNight
35%
653
9%
1721
5%
653
36%
653
9%
1462
April21st to endNight
33%
490
5%
1570
4%
490
34%
490
7%
1354
May1st to 10thNight
50%
360
8%
1440
12%
360
51%
360
9%
1134
May11th to 20thNight
52%
354
7%
1416
12%
354
53%
354
9%
1082
May21st to endNight
47%
389
3%
1552
6%
388
48%
388
6%
1293
June1st to 10thNight
43%
360
2%
1288
2%
360
43%
360
8%
1067
June11th to 20thNight
44%
360
2%
1260
2%
360
44%
360
7%
1049
June21st to endNight
58%
360
6%
1260
5%
360
58%
360
12%
947
July1st to 10thNight
63%
350
8%
1225
8%
350
64%
350
16%
877
July11th to 20thNight
65%
348
11%
1235
13%
348
68%
348
18%
833
July21st to endNight
76%
394
14%
1488
22%
372
78%
372
20%
932
August1st to 10thNight
73%
379
10%
1445
14%
377
74%
377
16%
979
August11th to 20thNight
78%
534
17%
1602
17%
534
79%
534
24%
1070
August21st to endNight
65%
674
14%
1862
11%
674
66%
674
18%
1385
September1st to 10thNight
69%
720
15%
1800
9%
720
70%
720
24%
1306
September11th to 20thNight
56%
720
14%
1800
9%
720
57%
720
17%
1414
September21st to endNight
50%
720
11%
2060
10%
720
51%
720
13%
1636
October1st to 10thNight
49%
720
7%
2160
8%
720
50%
720
12%
1715
October11th to 20thNight
42%
720
7%
2160
7%
720
43%
720
10%
1765
October21st to endNight
35%
792
5%
2488
5%
792
36%
792
8%
2086
November1st to 10thNight
25%
740
3%
2585
3%
740
26%
740
4%
2314
November11th to 20thNight
27%
760
4%
2660
4%
760
28%
760
4%
2362
November21st to endNight
24%
760
2%
2660
1%
760
25%
760
4%
2374
December1st to 10thNight
35%
760
4%
2660
3%
760
35%
760
6%
2319
December11th to 20thNight
17%
811
1%
3430
0%
810
18%
810
2%
3109
December21st to endNight
17%
930
2%
5199
2%
905
19%
905
2%
4526

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%9%37%6%35%45%6%33%
78122
Night
24%10%47%6%34446%29%
81222
TransparencyDay
37%38%10%10%41
77835
Night
41%36%9%10%41
81089
SeeingDay
22%8%20%26%19%5%
14236
Night
28%8%17%24%19%4
22751

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 10thDay
30%17%5%9%7%35%435%14%
2219
11th to 20thDay
26%12%47%6%2445%6%23%
2307
21st to endDay
36%14%49%7%35%44310%
2837
February1st to 10thDay
28%12%48%7%45%5%5%6%16%
1710
11th to 20thDay
26%12%49%6%36%435%22%
1665
21st to endDay
24%12%5%9%7%3445%6%20%
1452
March1st to 10thDay
23%13%5%8%7%36%446%22%
1849
11th to 20thDay
25%12%47%6%35%445%24%
1980
21st to endDay
23%11%49%7%37%5%5%6%20%
2242
April1st to 10thDay
23%10%5%7%6%36%5%6%7%22%
2160
11th to 20thDay
19%10%47%5%45%6%6%7%26%
2187
21st to endDay
21%8%48%6%45%5%6%7%27%
2389
May1st to 10thDay
16%6%37%6%36%5%5%8%35%
2520
11th to 20thDay
15%7%35%6%45%5%6%8%35%
2477
21st to endDay
18%8%47%6%3446%6%35%
2723
June1st to 10thDay
18%7%36%6%35%45%7%36%
2669
11th to 20thDay
17%7%36%7%46%6%6%7%32%
2700
21st to endDay
11%6%35%446%5%5%7%44%
2700
July1st to 10thDay
8%5%2443345%7%53%
2700
11th to 20thDay
8%42442435%7%56%
2682
21st to endDay
6%213312346%67%
2741
August1st to 10thDay
8%5%24433348%57%
2483
11th to 20thDay
6%31442446%8%57%
2298
21st to endDay
10%5%2443446%9%48%
2494
September1st to 10thDay
10%5%26%4245%47%51%
2160
11th to 20thDay
14%7%36%5%35%45%7%42%
2160
21st to endDay
19%8%26%5%345%47%37%
1899
October1st to 10thDay
20%10%37%5%35%5%6%6%32%
1800
11th to 20thDay
24%11%47%6%345%5%7%24%
1800
21st to endDay
28%8%47%7%35%446%25%
1867
November1st to 10thDay
31%11%47%7%36%5%45%18%
1488
11th to 20thDay
29%11%48%6%3444423%
1520
21st to endDay
30%11%49%7%35%5%5%418%
1520
December1st to 10thDay
27%11%5%7%6%35%346%23%
1520
11th to 20thDay
30%13%410%8%46%5%5%312%
1762
21st to endDay
26%15%5%9%8%36%5%5%6%12%
2442
January1st to 10thNight
30%15%49%8%45%44413%
4726
11th to 20thNight
28%11%46%43445%8%24%
4576
21st to endNight
35%15%48%6%34345%13%
4817
February1st to 10thNight
30%13%5%7%5%34435%21%
2470
11th to 20thNight
24%14%48%6%3444424%
2402
21st to endNight
28%10%47%6%35%45%5%23%
2001
March1st to 10thNight
26%10%46%6%45%5%5%5%24%
2116
11th to 20thNight
25%12%47%6%45%45%5%23%
1979
21st to endNight
28%12%5%7%6%345%5%6%19%
2113
April1st to 10thNight
23%11%47%8%4446%6%23%
1800
11th to 20thNight
22%9%47%7%45%5%47%26%
1721
21st to endNight
23%11%5%8%6%3435%6%26%
1570
May1st to 10thNight
15%6%26%5%3446%7%42%
1440
11th to 20thNight
15%7%36%6%35%5%7%9%35%
1416
21st to endNight
17%7%47%7%45%45%7%33%
1552
June1st to 10thNight
18%7%47%6%5%5%45%7%33%
1288
11th to 20thNight
18%7%37%6%446%5%8%32%
1260
21st to endNight
12%5%35%5%4436%8%45%
1260
July1st to 10thNight
10%5%35%423446%56%
1260
11th to 20thNight
8%5%24322446%60%
1277
21st to endNight
5%21231434471%
1576
August1st to 10thNight
7%413334446%61%
1453
11th to 20thNight
7%313323347%64%
1602
21st to endNight
8%4245%3445%8%53%
1862
September1st to 10thNight
9%424323447%58%
1800
11th to 20thNight
15%5%26%5%34446%45%
1800
21st to endNight
16%6%36%6%3445%6%41%
2060
October1st to 10thNight
17%6%37%6%4444441%
2160
11th to 20thNight
24%7%35%5%34447%33%
2160
21st to endNight
27%8%36%5%33446%31%
2488
November1st to 10thNight
33%10%47%6%4444420%
2585
11th to 20thNight
30%10%36%6%35%445%23%
2660
21st to endNight
31%10%46%6%35%5%45%21%
2660
December1st to 10thNight
27%10%36%5%35%45%6%26%
2660
11th to 20thNight
31%14%49%7%45%445%13%
3438
21st to endNight
29%15%5%8%6%45%44416%
5214

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 10thDay
61%28%7%5%
2219
11th to 20thDay
47%27%11%9%5%1
2328
21st to endDay
65%26%431
2837
February1st to 10thDay
47%39%7%5%2
1710
11th to 20thDay
43%38%7%7%41
1674
21st to endDay
47%37%7%6%2
1452
March1st to 10thDay
45%38%9%5%21
1849
11th to 20thDay
45%37%8%7%21
1980
21st to endDay
45%40%7%7%1
2242
April1st to 10thDay
44%39%11%5%1
2160
11th to 20thDay
39%38%8%8%5%1
2187
21st to endDay
40%39%9%7%31
2389
May1st to 10thDay
37%39%10%11%3
2520
11th to 20thDay
31%40%13%11%5%
2480
21st to endDay
40%40%10%9%2
2724
June1st to 10thDay
35%39%12%8%41
2669
11th to 20thDay
38%41%12%7%2
2700
21st to endDay
29%40%12%13%6%1
2700
July1st to 10thDay
20%40%14%17%7%2
2626
11th to 20thDay
21%38%11%22%7%
2601
21st to endDay
16%39%10%23%9%3
2589
August1st to 10thDay
21%39%15%18%5%1
2466
11th to 20thDay
18%39%13%19%9%2
2298
21st to endDay
24%39%13%17%6%1
2494
September1st to 10thDay
18%40%12%18%9%4
2160
11th to 20thDay
27%39%11%13%10%1
2160
21st to endDay
31%40%10%12%5%2
1899
October1st to 10thDay
32%40%11%11%5%
1800
11th to 20thDay
37%40%10%10%21
1800
21st to endDay
40%40%8%7%5%
1867
November1st to 10thDay
45%42%5%5%31
1488
11th to 20thDay
44%41%6%6%2
1520
21st to endDay
44%43%6%5%2
1520
December1st to 10thDay
42%42%7%6%3
1520
11th to 20thDay
47%40%7%6%1
1765
21st to endDay
57%31%8%41
2442
January1st to 10thNight
61%29%6%41
4726
11th to 20thNight
46%27%10%13%31
4616
21st to endNight
62%26%5%5%2
4817
February1st to 10thNight
47%36%9%6%2
2470
11th to 20thNight
41%38%9%7%5%1
2404
21st to endNight
48%35%6%8%2
2001
March1st to 10thNight
42%38%10%7%2
2116
11th to 20thNight
45%38%7%7%21
1980
21st to endNight
45%39%9%7%
2113
April1st to 10thNight
44%39%10%6%1
1800
11th to 20thNight
39%38%8%9%5%2
1721
21st to endNight
43%36%8%8%41
1570
May1st to 10thNight
32%39%11%13%5%
1440
11th to 20thNight
29%39%13%12%6%
1416
21st to endNight
39%39%10%10%2
1552
June1st to 10thNight
38%38%10%9%42
1288
11th to 20thNight
37%40%13%8%2
1260
21st to endNight
28%38%13%14%43
1260
July1st to 10thNight
21%39%11%18%8%3
1225
11th to 20thNight
17%38%14%22%8%2
1235
21st to endNight
13%37%10%21%16%4
1488
August1st to 10thNight
19%37%14%20%9%1
1445
11th to 20thNight
15%36%14%19%13%3
1602
21st to endNight
23%38%11%20%8%1
1862
September1st to 10thNight
16%38%10%21%10%4
1800
11th to 20thNight
26%38%9%13%11%2
1800
21st to endNight
29%39%10%15%6%1
2060
October1st to 10thNight
32%37%10%14%7%
2160
11th to 20thNight
34%38%10%14%3
2160
21st to endNight
37%39%10%9%5%
2488
November1st to 10thNight
43%42%6%6%21
2585
11th to 20thNight
43%42%8%5%2
2660
21st to endNight
41%43%7%6%2
2660
December1st to 10thNight
39%43%8%7%3
2660
11th to 20thNight
49%39%7%32
3435
21st to endNight
54%31%9%5%1
5214

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 10thDay
35%17%17%14%11%7%
180
11th to 20thDay
32%17%18%14%12%6%
180
21st to endDay
42%12%18%13%13%1
228
February1st to 10thDay
40%9%21%19%9%2
370
11th to 20thDay
35%12%22%20%10%1
365
21st to endDay
33%14%21%19%11%1
326
March1st to 10thDay
32%11%24%21%11%1
421
11th to 20thDay
31%11%18%20%16%4
420
21st to endDay
31%11%22%22%12%2
462
April1st to 10thDay
28%13%21%22%13%3
420
11th to 20thDay
23%13%23%22%13%6%
412
21st to endDay
25%12%23%25%13%3
420
May1st to 10thDay
16%8%23%30%20%2
423
11th to 20thDay
23%5%17%28%21%5%
448
21st to endDay
18%7%22%29%16%6%
485
June1st to 10thDay
21%7%26%29%16%3
599
11th to 20thDay
22%8%24%34%10%3
630
21st to endDay
10%6%23%31%25%5%
630
July1st to 10thDay
12%320%34%25%6%
621
11th to 20thDay
8%6%20%34%26%6%
600
21st to endDay
6%214%33%33%11%
487
August1st to 10thDay
11%411%28%35%12%
447
11th to 20thDay
6%113%30%39%11%
437
21st to endDay
10%6%18%33%27%7%
495
September1st to 10thDay
15%419%33%24%5%
450
11th to 20thDay
15%6%17%30%27%5%
450
21st to endDay
22%6%19%24%21%7%
450
October1st to 10thDay
24%6%19%24%18%10%
450
11th to 20thDay
30%9%20%16%16%8%
450
21st to endDay
32%12%20%18%13%5%
382
November1st to 10thDay
33%17%20%17%11%2
180
11th to 20thDay
35%11%18%14%14%8%
180
21st to endDay
32%14%18%17%8%10%
180
December1st to 10thDay
40%17%13%8%11%11%
180
11th to 20thDay
39%17%18%15%10%1
180
21st to endDay
39%10%22%22%5%2
198
January1st to 10thNight
41%13%17%14%12%2
850
11th to 20thNight
38%11%14%18%18%1
816
21st to endNight
37%9%17%21%13%2
836
February1st to 10thNight
38%10%17%23%11%2
760
11th to 20thNight
33%10%17%24%15%1
744
21st to endNight
35%10%19%22%11%3
628
March1st to 10thNight
31%13%19%22%13%2
722
11th to 20thNight
32%11%19%20%15%3
720
21st to endNight
35%10%19%25%9%2
792
April1st to 10thNight
31%10%17%25%15%3
720
11th to 20thNight
26%9%19%26%16%3
653
21st to endNight
30%7%19%28%14%2
490
May1st to 10thNight
19%6%16%34%22%3
360
11th to 20thNight
21%5%14%26%29%5%
354
21st to endNight
20%418%29%24%4
389
June1st to 10thNight
22%422%28%22%2
360
11th to 20thNight
22%6%19%33%18%2
360
21st to endNight
15%416%32%29%4
360
July1st to 10thNight
12%315%33%33%4
350
11th to 20thNight
11%315%32%33%5%
348
21st to endNight
7%213%31%39%8%
394
August1st to 10thNight
9%37%25%45%11%
379
11th to 20thNight
9%16%23%46%15%
534
21st to endNight
12%313%31%34%7%
674
September1st to 10thNight
11%212%37%31%7%
720
11th to 20thNight
19%413%21%33%12%
720
21st to endNight
20%5%16%25%28%7%
720
October1st to 10thNight
22%5%15%23%27%8%
720
11th to 20thNight
30%8%12%22%22%6%
720
21st to endNight
31%9%18%24%14%4
792
November1st to 10thNight
36%12%19%22%11%
740
11th to 20thNight
37%11%18%18%14%2
760
21st to endNight
36%11%20%17%13%4
760
December1st to 10thNight
32%9%16%24%16%3
760
11th to 20thNight
39%12%22%19%8%1
811
21st to endNight
39%13%23%18%7%1
935
Page generated at 2024-02-27 03:30:12. Version ac07

Copyright © 2024 Attilla Danko.


Anacortes Clear Sky Chart |Charts Home