McCall
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the McCall clear sky chart from 2005-11-05 to 2017-10-31.

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
49%
15012
16%
47503
15%
14984
52%
14984
23%
31466

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
36%
716
10%
2506
9%
716
39%
716
11%
1923
January16th to endNight
43%
768
12%
2688
13%
768
45%
768
15%
1938
February1st to 15thNight
34%
700
8%
2301
6%
696
38%
696
13%
1771
February16th to endNight
32%
632
9%
1895
8%
632
35%
632
12%
1518
March1st to 15thNight
33%
720
7%
2152
5%
720
36%
720
13%
1677
March16th to endNight
34%
768
8%
2043
5%
768
36%
768
15%
1608
April1st to 15thNight
42%
719
11%
1799
6%
719
43%
719
20%
1341
April16th to endNight
46%
554
18%
1634
13%
554
49%
554
25%
1058
May1st to 15thNight
52%
512
17%
1592
14%
512
56%
512
30%
938
May16th to endNight
59%
374
12%
1496
17%
374
60%
374
19%
936
June1st to 15thNight
56%
360
9%
1440
13%
360
58%
360
20%
890
June16th to endNight
69%
360
20%
1440
29%
360
74%
360
37%
682
July1st to 15thNight
82%
340
21%
1360
35%
340
86%
340
51%
532
July16th to endNight
85%
376
32%
1416
46%
354
89%
354
60%
507
August1st to 15thNight
78%
460
30%
1533
31%
458
81%
458
54%
675
August16th to endNight
76%
668
33%
1814
24%
668
77%
668
60%
880
September1st to 15thNight
75%
720
32%
1848
20%
720
79%
720
58%
967
September16th to endNight
65%
716
31%
1980
25%
716
67%
716
41%
1139
October1st to 15thNight
54%
720
21%
2040
18%
720
58%
720
31%
1268
October16th to endNight
51%
768
18%
2496
17%
768
54%
768
23%
1638
November1st to 15thNight
42%
700
16%
2275
15%
700
46%
700
18%
1610
November16th to endNight
37%
720
11%
2394
10%
720
39%
720
15%
1750
December1st to 15thNight
33%
857
7%
2657
4%
857
36%
857
12%
2068
December16th to endNight
30%
784
9%
2704
7%
784
33%
784
9%
2152

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
10%9%36%424446%42%
48252
Night
12%9%35%423446%43%
47673
Cloud CoverDay
12%11%35%424446%40%
48253
Night
13%11%35%423346%41%
47676
TransparencyDay
44%6%10%18%14%6%
47924
Night
43%6%12%19%13%4
47504
SeeingDay
17%17%31%22%9%1
5489
Night
18%6%19%32%21%2
15022

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
15%15%5%8%5%34435%28%
1432
16th to endDay
16%17%35%32345%6%31%
1536
February1st to 15thDay
14%15%6%8%5%2445%5%29%
1562
16th to endDay
12%20%6%10%5%35%336%21%
1579
March1st to 15thDay
17%18%6%8%7%245%45%19%
1807
16th to endDay
15%18%5%10%6%4435%5%20%
2177
April1st to 15thDay
12%14%5%8%7%35%446%26%
2149
16th to endDay
11%11%46%433447%37%
2325
May1st to 15thDay
8%7%35%6%3445%7%43%
2355
16th to endDay
12%10%48%7%4445%6%31%
2615
June1st to 15thDay
15%8%46%6%46%5%47%31%
2520
16th to endDay
7%414423336%57%
2520
July1st to 15thDay
321321345%6%65%
2520
16th to endDay
1112212346%73%
2657
August1st to 15thDay
2212223446%66%
2418
16th to endDay
222223246%69%
2387
September1st to 15thDay
3212212236%69%
2112
16th to endDay
9%5%145%23435%54%
1980
October1st to 15thDay
11%6%25%32345%6%47%
1918
16th to endDay
14%11%26%423446%38%
1726
November1st to 15thDay
18%11%36%5%35%447%30%
1584
16th to endDay
16%12%46%434346%31%
1564
December1st to 15thDay
17%15%6%8%5%23446%25%
1285
16th to endDay
21%18%5%7%5%23345%22%
1524
January1st to 15thNight
18%16%47%5%23335%28%
2506
16th to endNight
14%16%36%424445%35%
2688
February1st to 15thNight
17%16%46%5%2343430%
2290
16th to endNight
14%16%5%7%6%43446%26%
1895
March1st to 15thNight
17%15%46%5%2444429%
2152
16th to endNight
14%13%36%435%5%5%7%28%
2040
April1st to 15thNight
11%10%46%6%35%5%6%6%34%
1799
16th to endNight
12%7%34432346%46%
1634
May1st to 15thNight
8%425%42435%6%52%
1592
16th to endNight
9%5%26%445%6%5%8%39%
1496
June1st to 15thNight
13%5%25%42445%8%42%
1440
16th to endNight
7%21231435%6%60%
1440
July1st to 15thNight
11122345%6%70%
1440
16th to endNight
21222235%75%
1512
August1st to 15thNight
311321225%7%68%
1541
16th to endNight
212212337%71%
1814
September1st to 15thNight
321222335%5%69%
1848
16th to endNight
10%412323345%58%
1980
October1st to 15thNight
9%4245%24447%49%
2040
16th to endNight
14%7%25%42345%7%42%
2496
November1st to 15thNight
20%10%2343245%7%35%
2275
16th to endNight
19%11%35%433436%33%
2394
December1st to 15thNight
16%15%47%5%2445%5%29%
2657
16th to endNight
17%20%47%42443426%
2704

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
15%17%6%9%424325%27%
1432
16th to endDay
16%18%5%6%323346%29%
1536
February1st to 15thDay
16%16%7%7%433445%26%
1562
16th to endDay
12%23%8%11%5%2344418%
1579
March1st to 15thDay
17%21%6%8%6%3444417%
1807
16th to endDay
16%23%6%9%5%24445%18%
2178
April1st to 15thDay
14%17%6%8%6%3445%6%23%
2149
16th to endDay
12%15%36%42335%7%34%
2325
May1st to 15thDay
9%9%36%5%245%6%9%38%
2355
16th to endDay
14%12%47%7%3445%7%28%
2615
June1st to 15thDay
17%9%36%5%35%45%6%30%
2520
16th to endDay
10%5%14312345%56%
2520
July1st to 15thDay
4312323347%62%
2520
16th to endDay
22221334472%
2657
August1st to 15thDay
3213324446%63%
2418
16th to endDay
3312213345%67%
2387
September1st to 15thDay
4313322245%67%
2112
16th to endDay
10%6%23323335%53%
1980
October1st to 15thDay
14%7%34433445%45%
1918
16th to endDay
17%13%25%424436%36%
1726
November1st to 15thDay
19%15%45%424446%27%
1584
16th to endDay
17%15%46%5%2434429%
1564
December1st to 15thDay
18%17%7%8%413445%23%
1285
16th to endDay
20%20%5%9%42434421%
1524
January1st to 15thNight
18%18%48%424335%26%
2506
16th to endNight
14%17%5%5%323345%33%
2688
February1st to 15thNight
17%18%5%7%42334328%
2290
16th to endNight
14%19%8%8%42444424%
1895
March1st to 15thNight
17%19%5%6%424336%25%
2152
16th to endNight
15%17%45%5%245%5%6%26%
2043
April1st to 15thNight
12%13%46%5%35%5%6%6%31%
1799
16th to endNight
12%8%25%423446%43%
1634
May1st to 15thNight
8%6%2443445%6%50%
1592
16th to endNight
10%7%25%6%346%6%8%38%
1496
June1st to 15thNight
15%5%25%33445%7%41%
1440
16th to endNight
8%213322446%59%
1440
July1st to 15thNight
2112213448%68%
1440
16th to endNight
2111212245%75%
1512
August1st to 15thNight
32221236%6%67%
1541
16th to endNight
212222346%69%
1814
September1st to 15thNight
3213212245%69%
1848
16th to endNight
11%423322345%57%
1980
October1st to 15thNight
11%5%25%43435%6%47%
2040
16th to endNight
16%9%25%42345%6%39%
2496
November1st to 15thNight
21%12%34323346%33%
2275
16th to endNight
19%15%45%422345%32%
2394
December1st to 15thNight
16%17%5%7%5%24445%26%
2657
16th to endNight
17%22%6%7%42433423%
2704

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
59%9%11%14%4
1432
16th to endDay
55%8%14%15%5%2
1536
February1st to 15thDay
58%9%12%14%3
1562
16th to endDay
68%6%11%11%2
1579
March1st to 15thDay
68%7%9%10%4
1807
16th to endDay
67%7%8%13%3
2178
April1st to 15thDay
60%7%14%13%3
2149
16th to endDay
48%7%14%20%8%
2325
May1st to 15thDay
41%7%13%28%9%
2355
16th to endDay
54%9%10%18%6%1
2619
June1st to 15thDay
52%6%10%18%9%2
2520
16th to endDay
29%5%8%24%27%5%
2520
July1st to 15thDay
20%48%17%30%19%
2371
16th to endDay
12%35%14%31%32%
2490
August1st to 15thDay
18%5%8%19%28%18%
2401
16th to endDay
17%47%22%32%15%
2387
September1st to 15thDay
19%48%21%31%14%
2112
16th to endDay
32%49%28%19%4
1980
October1st to 15thDay
38%7%11%26%14%2
1918
16th to endDay
48%6%11%19%14%
1726
November1st to 15thDay
55%8%14%15%5%
1584
16th to endDay
56%7%13%14%7%1
1564
December1st to 15thDay
61%9%14%12%2
1285
16th to endDay
64%7%11%11%3
1524
January1st to 15thNight
60%7%10%14%6%1
2506
16th to endNight
52%8%12%16%9%1
2688
February1st to 15thNight
59%7%11%14%5%
2301
16th to endNight
62%7%10%14%31
1895
March1st to 15thNight
59%6%12%14%5%
2152
16th to endNight
54%10%14%15%4
2043
April1st to 15thNight
49%9%17%18%5%
1799
16th to endNight
40%7%15%26%9%
1634
May1st to 15thNight
32%7%13%34%11%
1593
16th to endNight
41%8%16%25%7%
1496
June1st to 15thNight
40%8%13%23%10%3
1440
16th to endNight
24%5%12%28%23%5%
1440
July1st to 15thNight
14%49%21%32%17%
1360
16th to endNight
11%25%18%33%28%
1416
August1st to 15thNight
15%48%23%29%18%
1533
16th to endNight
15%39%22%31%17%
1814
September1st to 15thNight
18%38%25%29%15%
1848
16th to endNight
29%410%26%22%7%
1980
October1st to 15thNight
35%6%12%26%16%2
2040
16th to endNight
42%7%13%19%16%
2496
November1st to 15thNight
49%8%13%19%8%
2275
16th to endNight
55%6%12%15%8%2
2394
December1st to 15thNight
58%8%13%14%4
2657
16th to endNight
64%7%10%12%5%
2704

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
18%120%35%16%8%
60
16th to endDay
31%6%29%18%9%4
64
February1st to 15thDay
28%16%21%19%13%1
142
16th to endDay
24%30%27%11%5%
238
March1st to 15thDay
33%26%27%10%1
270
16th to endDay
32%24%26%13%2
288
April1st to 15thDay
24%21%29%12%7%3
269
16th to endDay
22%24%32%14%4
270
May1st to 15thDay
13%21%37%20%6%
288
16th to endDay
22%12%25%25%9%4
330
June1st to 15thDay
19%20%28%20%8%1
315
16th to endDay
11%17%33%26%11%
315
July1st to 15thDay
6%11%38%28%13%
305
16th to endDay
314%40%30%8%1
327
August1st to 15thDay
5%9%38%33%12%1
315
16th to endDay
48%36%31%14%3
332
September1st to 15thDay
6%16%31%27%13%4
315
16th to endDay
14%12%32%27%12%
315
October1st to 15thDay
17%22%29%22%6%1
292
16th to endDay
29%10%19%25%11%4
144
November1st to 15thDay
26%12%18%26%15%
90
16th to endDay
23%27%22%18%6%2
81
December1st to 15thDay
43%20%25%8%3
60
16th to endDay
29%12%17%29%9%1
64
January1st to 15thNight
26%6%18%29%16%1
720
16th to endNight
22%5%19%28%20%4
768
February1st to 15thNight
28%5%22%28%14%1
704
16th to endNight
22%10%23%25%15%2
632
March1st to 15thNight
25%12%23%25%12%1
720
16th to endNight
22%11%26%28%10%
768
April1st to 15thNight
16%10%23%27%18%3
719
16th to endNight
16%8%23%33%16%1
554
May1st to 15thNight
11%7%23%37%19%1
513
16th to endNight
12%315%37%28%3
375
June1st to 15thNight
18%315%39%21%1
360
16th to endNight
8%214%45%28%1
360
July1st to 15thNight
2110%46%36%2
340
16th to endNight
19%53%33%1
376
August1st to 15thNight
3111%44%36%2
460
16th to endNight
3114%38%38%4
668
September1st to 15thNight
3114%38%37%4
720
16th to endNight
12%313%31%32%6%
716
October1st to 15thNight
12%6%19%35%22%3
720
16th to endNight
20%417%33%19%4
768
November1st to 15thNight
28%5%18%32%14%1
700
16th to endNight
25%10%20%25%15%3
720
December1st to 15thNight
24%8%22%30%12%
857
16th to endNight
29%9%22%25%12%
784
Page generated at 2017-11-01 15:23:40. Version ac04

Copyright 2017 A. Danko


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