Crater Lake National Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crater Lake National Park clear sky chart from 2005-11-05 to 2017-08-12.

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
50%
14713
17%
46518
17%
14682
52%
14682
22%
30948

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
35%
717
11%
2506
11%
716
38%
716
12%
1875
January16th to endNight
44%
768
18%
2541
18%
768
46%
768
17%
1800
February1st to 15thNight
38%
699
9%
2288
9%
697
40%
697
13%
1732
February16th to endNight
36%
632
13%
1963
11%
632
39%
632
13%
1507
March1st to 15thNight
33%
720
7%
2046
6%
720
34%
720
12%
1639
March16th to endNight
30%
768
9%
2073
7%
768
30%
768
12%
1691
April1st to 15thNight
34%
719
9%
1799
6%
719
34%
719
15%
1450
April16th to endNight
48%
672
15%
1752
9%
672
49%
672
24%
1251
May1st to 15thNight
53%
416
16%
1496
15%
416
58%
416
24%
908
May16th to endNight
50%
375
13%
1496
17%
374
52%
374
17%
1000
June1st to 15thNight
61%
360
14%
1440
20%
360
64%
360
22%
848
June16th to endNight
74%
360
24%
1440
39%
360
76%
360
39%
656
July1st to 15thNight
87%
340
25%
1360
40%
340
87%
340
54%
515
July16th to endNight
86%
407
34%
1445
45%
383
88%
383
59%
543
August1st to 15thNight
88%
526
34%
1575
30%
523
89%
523
60%
708
August16th to endNight
80%
646
38%
1696
24%
646
82%
646
62%
830
September1st to 15thNight
83%
660
40%
1650
26%
660
85%
660
75%
766
September16th to endNight
66%
656
31%
1803
26%
656
69%
656
42%
1024
October1st to 15thNight
59%
660
20%
1980
19%
660
64%
660
33%
1174
October16th to endNight
50%
704
18%
2118
20%
704
51%
704
22%
1450
November1st to 15thNight
36%
700
12%
2323
13%
700
38%
700
14%
1740
November16th to endNight
35%
720
9%
2520
9%
720
37%
720
12%
1888
December1st to 15thNight
39%
720
13%
2520
12%
720
42%
720
15%
1828
December16th to endNight
30%
768
12%
2688
11%
768
33%
768
10%
2125

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
8%10%46%5%23345%43%
47472
Night
8%10%47%6%34445%40%
46693
TransparencyDay
42%49%18%17%6%
47146
Night
46%49%17%15%6%
46519
SeeingDay
23%14%26%22%10%2
5571
Night
18%10%14%28%23%4
14722

By Month

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
12%13%49%7%35%46%6%27%
1432
16th to endDay
11%14%48%5%23446%33%
1680
February1st to 15thDay
12%16%5%8%7%35%5%5%7%20%
1576
16th to endDay
7%17%11%11%7%43425%22%
1511
March1st to 15thDay
11%21%7%10%6%24345%21%
1911
16th to endDay
11%21%8%10%6%23336%21%
2151
April1st to 15thDay
10%21%7%10%6%33336%22%
2149
16th to endDay
7%15%5%8%5%2445%7%34%
2205
May1st to 15thDay
7%9%47%5%3345%7%41%
2453
16th to endDay
12%14%48%5%23337%32%
2615
June1st to 15thDay
9%8%35%5%33446%44%
2520
16th to endDay
5%425%323335%59%
2520
July1st to 15thDay
2112213235%72%
2520
16th to endDay
211211222377%
2624
August1st to 15thDay
1112223345%70%
2291
16th to endDay
3212223476%
2154
September1st to 15thDay
1112223235%74%
1980
16th to endDay
5%6%25%423346%55%
1826
October1st to 15thDay
10%9%36%5%14435%44%
1650
16th to endDay
14%10%47%42335%5%39%
1752
November1st to 15thDay
11%13%410%6%3435%8%27%
1536
16th to endDay
10%14%6%11%9%24445%26%
1440
December1st to 15thDay
12%12%7%8%6%245%5%6%28%
1440
16th to endDay
12%19%7%10%6%3444422%
1536
January1st to 15thNight
11%12%5%9%7%45%5%45%27%
2506
16th to endNight
9%13%49%7%34445%32%
2541
February1st to 15thNight
11%13%5%9%9%4445%5%25%
2276
16th to endNight
8%16%7%12%8%34345%26%
1963
March1st to 15thNight
8%18%6%10%8%36%45%7%20%
2046
16th to endNight
9%16%7%12%10%44445%22%
2073
April1st to 15thNight
8%15%6%11%9%4445%5%22%
1799
16th to endNight
411%5%9%5%25%5%5%6%37%
1752
May1st to 15thNight
5%8%25%6%35%45%7%43%
1496
16th to endNight
7%10%48%7%35%447%35%
1496
June1st to 15thNight
7%7%36%5%34447%46%
1440
16th to endNight
5%31342322464%
1440
July1st to 15thNight
212312335%71%
1440
16th to endNight
22221222377%
1543
August1st to 15thNight
11232245%471%
1584
16th to endNight
121232223376%
1696
September1st to 15thNight
111233479%
1650
16th to endNight
6%5%24322346%56%
1803
October1st to 15thNight
7%6%35%5%2345%5%51%
1980
16th to endNight
10%9%47%8%2445%5%37%
2118
November1st to 15thNight
11%10%5%10%10%5%4446%25%
2323
16th to endNight
9%14%6%9%8%45%5%5%426%
2520
December1st to 15thNight
14%11%5%8%7%3445%5%29%
2520
16th to endNight
13%16%6%10%7%46%43422%
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
56%5%12%12%9%3
1432
16th to endDay
51%5%9%15%10%7%
1680
February1st to 15thDay
60%6%13%11%8%
1576
16th to endDay
65%49%12%6%1
1511
March1st to 15thDay
66%48%13%6%
1911
16th to endDay
65%5%10%11%6%
2151
April1st to 15thDay
65%5%11%12%5%
2149
16th to endDay
49%7%15%17%9%1
2205
May1st to 15thDay
42%5%13%23%13%1
2453
16th to endDay
53%5%11%21%7%
2619
June1st to 15thDay
41%6%11%22%16%2
2520
16th to endDay
27%411%30%21%5%
2520
July1st to 15thDay
14%29%25%30%17%
2371
16th to endDay
14%2314%39%25%
2459
August1st to 15thDay
15%37%26%28%18%
2275
16th to endDay
13%26%22%42%13%
2154
September1st to 15thDay
13%1420%36%22%
1980
16th to endDay
30%38%25%22%10%
1826
October1st to 15thDay
41%5%8%16%19%8%
1650
16th to endDay
45%412%17%15%3
1752
November1st to 15thDay
55%412%12%12%1
1536
16th to endDay
60%49%11%9%5%
1440
December1st to 15thDay
56%5%9%19%8%
1440
16th to endDay
66%47%11%8%2
1536
January1st to 15thNight
58%6%8%10%11%3
2506
16th to endNight
52%5%6%14%11%9%
2541
February1st to 15thNight
59%5%11%11%10%1
2288
16th to endNight
60%48%15%8%1
1963
March1st to 15thNight
64%5%8%9%10%1
2046
16th to endNight
65%5%11%11%6%
2073
April1st to 15thNight
62%5%11%12%7%
1799
16th to endNight
46%6%14%21%8%1
1752
May1st to 15thNight
39%6%13%26%12%3
1497
16th to endNight
48%6%13%21%8%1
1496
June1st to 15thNight
39%5%13%23%13%3
1440
16th to endNight
24%310%35%21%4
1440
July1st to 15thNight
14%28%29%27%17%
1360
16th to endNight
13%1313%41%25%
1445
August1st to 15thNight
13%37%27%30%16%
1575
16th to endNight
14%36%22%38%15%
1696
September1st to 15thNight
9%15%24%37%21%
1650
16th to endNight
28%38%24%20%14%
1803
October1st to 15thNight
33%5%11%20%21%8%
1980
16th to endNight
47%412%14%16%4
2118
November1st to 15thNight
59%49%13%10%2
2323
16th to endNight
59%5%8%9%9%6%
2520
December1st to 15thNight
56%5%8%17%12%
2520
16th to endNight
66%36%11%9%2
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
38%16%21%16%6%
60
16th to endDay
31%17%16%20%12%1
208
February1st to 15thDay
37%12%23%22%5%
236
16th to endDay
33%22%21%17%31
227
March1st to 15thDay
41%20%18%15%3
270
16th to endDay
36%24%21%13%4
288
April1st to 15thDay
32%19%23%14%6%3
269
16th to endDay
31%21%23%15%42
270
May1st to 15thDay
25%18%29%18%7%1
288
16th to endDay
31%10%20%20%11%5%
330
June1st to 15thDay
20%15%28%21%11%1
315
16th to endDay
11%12%33%22%13%5%
315
July1st to 15thDay
9%6%33%32%14%3
305
16th to endDay
29%37%30%12%7%
327
August1st to 15thDay
27%30%36%16%7%
300
16th to endDay
8%11%29%25%16%7%
268
September1st to 15thDay
5%9%31%30%18%3
255
16th to endDay
15%12%27%27%17%
255
October1st to 15thDay
29%12%24%20%12%
255
16th to endDay
34%11%22%19%10%1
264
November1st to 15thDay
23%6%28%30%10%1
82
16th to endDay
36%18%25%11%6%1
60
December1st to 15thDay
48%18%23%10%
60
16th to endDay
32%14%17%23%12%
64
January1st to 15thNight
21%15%19%23%15%4
720
16th to endNight
23%11%13%24%20%6%
768
February1st to 15thNight
25%12%16%27%18%1
704
16th to endNight
24%12%19%27%12%1
632
March1st to 15thNight
27%16%15%22%15%3
720
16th to endNight
28%16%17%22%13%1
768
April1st to 15thNight
22%15%21%21%15%2
719
16th to endNight
15%14%18%25%21%5%
672
May1st to 15thNight
15%7%17%33%23%3
417
16th to endNight
18%7%14%27%26%5%
375
June1st to 15thNight
15%5%13%33%30%2
360
16th to endNight
10%210%43%31%2
360
July1st to 15thNight
2439%49%2
340
16th to endNight
4344%41%5%
407
August1st to 15thNight
2335%50%7%
526
16th to endNight
4210%39%38%5%
646
September1st to 15thNight
1310%33%44%7%
660
16th to endNight
12%6%10%28%33%8%
656
October1st to 15thNight
14%6%13%34%25%5%
660
16th to endNight
22%7%12%27%22%7%
704
November1st to 15thNight
24%12%18%25%14%4
700
16th to endNight
27%13%17%19%16%4
720
December1st to 15thNight
27%10%17%24%16%3
720
16th to endNight
29%18%16%21%11%2
768
Page generated at 2017-08-13 11:16:44. Version ac04

Copyright 2017 A. Danko


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