Cascadia State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cascadia State Park clear sky chart from 2005-11-05 to 2017-09-14.

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
44%
14718
14%
46847
13%
14691
45%
14691
18%
33461

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
29%
716
10%
2506
8%
716
33%
716
11%
1965
January16th to endNight
33%
768
14%
2569
12%
768
37%
768
14%
1909
February1st to 15thNight
30%
699
7%
2288
7%
698
31%
698
10%
1866
February16th to endNight
26%
632
11%
1987
8%
632
32%
632
9%
1596
March1st to 15thNight
31%
720
5%
2044
5%
720
32%
720
10%
1717
March16th to endNight
28%
768
6%
2078
4%
768
29%
768
10%
1774
April1st to 15thNight
27%
719
6%
1799
4%
719
28%
719
11%
1529
April16th to endNight
41%
630
9%
1710
6%
630
42%
630
15%
1349
May1st to 15thNight
46%
398
12%
1479
14%
398
47%
398
17%
1007
May16th to endNight
42%
375
8%
1496
12%
374
42%
374
11%
1115
June1st to 15thNight
51%
360
9%
1440
13%
360
52%
360
14%
997
June16th to endNight
58%
360
13%
1440
24%
360
58%
360
23%
843
July1st to 15thNight
81%
340
20%
1360
34%
340
82%
340
46%
560
July16th to endNight
83%
376
32%
1416
44%
354
86%
354
54%
534
August1st to 15thNight
82%
538
29%
1611
27%
535
83%
535
55%
757
August16th to endNight
77%
675
34%
1821
24%
675
79%
675
57%
909
September1st to 15thNight
75%
716
33%
1790
21%
716
76%
716
59%
940
September16th to endNight
62%
656
26%
1806
23%
656
64%
656
34%
1115
October1st to 15thNight
53%
660
16%
1980
16%
660
55%
660
24%
1311
October16th to endNight
41%
704
14%
2131
15%
704
43%
704
16%
1599
November1st to 15thNight
28%
700
9%
2368
9%
700
29%
700
8%
1937
November16th to endNight
31%
720
8%
2520
7%
720
34%
720
11%
1958
December1st to 15thNight
30%
720
10%
2520
7%
720
34%
720
12%
1929
December16th to endNight
23%
768
7%
2688
7%
768
25%
768
7%
2245

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
24%9%24323335%36%
47887
Night
26%10%2432333434%
47015
Cloud CoverDay
25%9%24323335%36%
47887
Night
26%10%2432333434%
47019
TransparencyDay
52%39%17%12%4
47559
Night
54%39%15%12%4
46847
SeeingDay
29%11%26%21%7%2
5656
Night
32%5%12%26%20%3
14728

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
37%12%2443323321%
1432
16th to endDay
32%10%13322335%30%
1653
February1st to 15thDay
34%12%45%423445%18%
1576
16th to endDay
31%17%36%42332319%
1486
March1st to 15thDay
37%15%45%43334413%
1914
16th to endDay
37%16%46%32324414%
2145
April1st to 15thDay
32%18%47%42323414%
2149
16th to endDay
30%12%45%424346%22%
2247
May1st to 15thDay
26%8%35%313335%33%
2472
16th to endDay
34%9%34313346%24%
2615
June1st to 15thDay
29%8%35%5%23235%30%
2520
16th to endDay
18%5%25%423347%41%
2520
July1st to 15thDay
6%312212335%67%
2520
16th to endDay
6%312211235%70%
2654
August1st to 15thDay
331222225%6%66%
2340
16th to endDay
5%33212235%67%
2380
September1st to 15thDay
7%413211125%67%
2145
16th to endDay
19%5%245%23335%45%
1821
October1st to 15thDay
24%8%25%423335%36%
1650
16th to endDay
30%7%36%423345%30%
1741
November1st to 15thDay
42%9%25%42323418%
1491
16th to endDay
33%10%36%43433421%
1440
December1st to 15thDay
31%12%36%424335%23%
1440
16th to endDay
40%16%3422223317%
1536
January1st to 15thNight
35%12%35%41332422%
2506
16th to endNight
30%11%35%32233429%
2569
February1st to 15thNight
31%14%37%5%2333419%
2276
16th to endNight
30%17%3442323323%
1987
March1st to 15thNight
36%15%2442333419%
2044
16th to endNight
36%14%35%424335%16%
2074
April1st to 15thNight
33%17%35%42333419%
1799
16th to endNight
27%11%24424346%27%
1710
May1st to 15thNight
21%9%36%323336%35%
1478
16th to endNight
28%9%35%5%33347%25%
1496
June1st to 15thNight
25%7%24424436%33%
1440
16th to endNight
15%5%25%422236%47%
1440
July1st to 15thNight
6%21211332470%
1440
16th to endNight
5%211122476%
1512
August1st to 15thNight
4211213335%70%
1620
16th to endNight
4213211225%72%
1821
September1st to 15thNight
6%2221222471%
1790
16th to endNight
16%414422246%49%
1806
October1st to 15thNight
20%6%25%313345%43%
1980
16th to endNight
28%8%25%42243431%
2131
November1st to 15thNight
38%9%25%42344419%
2368
16th to endNight
34%11%25%41333425%
2520
December1st to 15thNight
32%12%44322335%25%
2520
16th to endNight
37%16%35%42332317%
2688

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
36%13%2443323321%
1432
16th to endDay
32%10%2332233430%
1653
February1st to 15thDay
34%12%36%424345%18%
1576
16th to endDay
31%18%35%42343319%
1486
March1st to 15thDay
36%16%35%423335%13%
1914
16th to endDay
37%17%45%31323414%
2145
April1st to 15thDay
32%18%46%5%2323414%
2149
16th to endDay
30%14%35%424336%22%
2247
May1st to 15thDay
26%9%24422335%34%
2472
16th to endDay
35%8%24323346%23%
2615
June1st to 15thDay
30%8%445%2323430%
2520
16th to endDay
18%5%25%323347%42%
2520
July1st to 15thDay
6%213212235%67%
2520
16th to endDay
6%31211222471%
2654
August1st to 15thDay
432312346%66%
2340
16th to endDay
5%313212235%68%
2380
September1st to 15thDay
7%322211225%67%
2145
16th to endDay
19%5%25%422335%45%
1821
October1st to 15thDay
25%7%245%13335%37%
1650
16th to endDay
30%7%25%42433430%
1741
November1st to 15thDay
44%8%3432333418%
1491
16th to endDay
33%11%26%5%2334422%
1440
December1st to 15thDay
31%13%35%5%2423423%
1440
16th to endDay
39%18%2421323318%
1536
January1st to 15thNight
35%12%35%32223423%
2506
16th to endNight
30%12%3432323329%
2569
February1st to 15thNight
31%15%45%5%3433419%
2276
16th to endNight
30%19%2442233322%
1987
March1st to 15thNight
35%16%3432344418%
2044
16th to endNight
35%16%45%423335%16%
2078
April1st to 15thNight
34%17%25%42333418%
1799
16th to endNight
27%12%23424445%27%
1710
May1st to 15thNight
21%10%35%423436%35%
1478
16th to endNight
29%9%345%24347%24%
1496
June1st to 15thNight
26%6%2433435%5%34%
1440
16th to endNight
16%5%245%23235%47%
1440
July1st to 15thNight
6%21311223470%
1440
16th to endNight
41121112476%
1512
August1st to 15thNight
422212245%70%
1620
16th to endNight
421221222472%
1821
September1st to 15thNight
6%21221222471%
1790
16th to endNight
16%5%13323336%49%
1806
October1st to 15thNight
20%7%33323435%43%
1980
16th to endNight
29%8%25%32334431%
2131
November1st to 15thNight
40%9%25%42344418%
2368
16th to endNight
35%11%25%32233326%
2520
December1st to 15thNight
32%12%34322335%25%
2520
16th to endNight
36%17%3442332317%
2688

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
69%26%8%10%3
1432
16th to endDay
58%47%13%9%6%
1653
February1st to 15thDay
69%48%9%6%
1576
16th to endDay
71%37%9%6%1
1486
March1st to 15thDay
74%5%5%9%3
1914
16th to endDay
75%48%8%3
2145
April1st to 15thDay
74%39%8%3
2149
16th to endDay
64%412%11%5%1
2247
May1st to 15thDay
54%313%19%8%
2472
16th to endDay
62%5%12%16%2
2619
June1st to 15thDay
59%313%17%5%1
2520
16th to endDay
43%316%24%8%3
2520
July1st to 15thDay
20%312%25%29%8%
2371
16th to endDay
18%2425%34%14%
2487
August1st to 15thDay
18%313%30%23%9%
2324
16th to endDay
21%29%31%28%7%
2380
September1st to 15thDay
21%16%29%25%15%
2145
16th to endDay
42%39%22%17%5%
1821
October1st to 15thDay
51%47%15%16%4
1650
16th to endDay
57%48%12%14%2
1741
November1st to 15thDay
70%27%10%6%1
1491
16th to endDay
67%36%9%8%4
1440
December1st to 15thDay
66%46%12%10%
1440
16th to endDay
73%16%10%6%2
1536
January1st to 15thNight
66%37%8%11%3
2506
16th to endNight
60%27%11%9%8%
2569
February1st to 15thNight
69%38%9%7%1
2288
16th to endNight
67%37%12%6%2
1987
March1st to 15thNight
69%48%10%5%
2044
16th to endNight
72%410%9%3
2078
April1st to 15thNight
71%310%8%6%
1799
16th to endNight
60%6%13%13%5%2
1710
May1st to 15thNight
51%412%19%10%1
1479
16th to endNight
60%5%13%16%4
1496
June1st to 15thNight
51%6%13%18%7%
1440
16th to endNight
41%316%26%8%3
1440
July1st to 15thNight
18%313%24%28%11%
1360
16th to endNight
14%25%23%36%17%
1416
August1st to 15thNight
17%39%34%25%8%
1611
16th to endNight
18%210%30%30%8%
1821
September1st to 15thNight
19%28%28%25%16%
1790
16th to endNight
36%310%23%16%9%
1806
October1st to 15thNight
44%411%15%18%5%
1980
16th to endNight
56%5%7%12%12%4
2131
November1st to 15thNight
68%5%6%8%9%
2368
16th to endNight
64%36%9%8%7%
2520
December1st to 15thNight
62%37%13%11%
2520
16th to endNight
74%27%8%5%1
2688

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
40%10%20%15%13%1
60
16th to endDay
43%5%15%22%12%1
181
February1st to 15thDay
45%8%19%18%7%
236
16th to endDay
46%14%19%15%4
223
March1st to 15thDay
53%16%18%10%1
270
16th to endDay
48%14%21%13%1
288
April1st to 15thDay
43%14%19%14%7%1
269
16th to endDay
47%15%21%10%5%1
270
May1st to 15thDay
37%14%23%17%32
288
16th to endDay
36%10%18%22%8%4
330
June1st to 15thDay
32%13%25%18%8%1
315
16th to endDay
17%10%34%26%8%2
315
July1st to 15thDay
8%10%37%26%12%4
305
16th to endDay
5%11%40%27%9%5%
327
August1st to 15thDay
410%35%33%9%6%
315
16th to endDay
6%11%29%33%13%6%
332
September1st to 15thDay
10%11%33%30%11%3
310
16th to endDay
20%11%29%28%8%1
255
October1st to 15thDay
30%10%30%18%8%1
255
16th to endDay
38%8%22%20%9%1
253
November1st to 15thDay
41%8%12%30%8%
75
16th to endDay
46%13%15%18%5%1
60
December1st to 15thDay
61%15%20%3
60
16th to endDay
45%9%14%20%9%1
64
January1st to 15thNight
42%6%15%20%11%2
720
16th to endNight
37%5%14%22%13%5%
768
February1st to 15thNight
39%5%15%25%12%1
704
16th to endNight
43%8%14%23%10%
632
March1st to 15thNight
47%6%9%23%11%1
720
16th to endNight
45%7%11%22%10%1
768
April1st to 15thNight
47%7%10%20%12%1
719
16th to endNight
36%6%11%23%17%3
630
May1st to 15thNight
28%7%11%25%25%2
399
16th to endNight
34%410%22%26%2
375
June1st to 15thNight
29%310%28%26%2
360
16th to endNight
20%310%32%32%1
360
July1st to 15thNight
7%15%38%44%2
340
16th to endNight
427%36%47%1
376
August1st to 15thNight
6%15%27%48%11%
538
16th to endNight
6%29%36%37%8%
675
September1st to 15thNight
8%111%32%38%7%
716
16th to endNight
19%39%34%28%4
656
October1st to 15thNight
24%412%31%23%4
660
16th to endNight
32%6%12%25%17%5%
704
November1st to 15thNight
47%413%24%9%
700
16th to endNight
42%6%12%25%10%1
720
December1st to 15thNight
40%5%19%22%10%2
720
16th to endNight
48%7%16%18%9%
768
Page generated at 2017-09-15 07:29:57. Version ac04

Copyright 2017 A. Danko


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