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Chain Lake Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chain Lake Provincial Park clear sky chart from 2005-11-05 to 2017-10-16.

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
34%
15296
15%
47132
8%
15264
42%
15264
20%
30711

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
21%
900
13%
2685
5%
895
29%
895
14%
1901
January16th to endNight
25%
787
18%
2707
9%
787
38%
787
17%
1723
February1st to 15thNight
29%
700
14%
2405
7%
697
39%
697
15%
1591
February16th to endNight
30%
632
15%
1962
10%
632
40%
632
18%
1349
March1st to 15thNight
23%
720
14%
2118
5%
720
33%
720
16%
1418
March16th to endNight
31%
768
11%
2088
2%
768
37%
768
17%
1521
April1st to 15thNight
30%
638
11%
1718
4%
638
35%
638
16%
1238
April16th to endNight
33%
540
12%
1620
8%
540
37%
540
16%
1147
May1st to 15thNight
41%
437
11%
1461
11%
437
45%
437
20%
943
May16th to endNight
41%
374
7%
1309
5%
374
43%
374
14%
941
June1st to 15thNight
38%
360
3%
1260
0%
360
39%
360
17%
853
June16th to endNight
45%
360
4%
1260
0%
360
45%
360
22%
763
July1st to 15thNight
56%
340
5%
1190
2%
340
57%
340
31%
655
July16th to endNight
62%
376
13%
1310
15%
354
68%
354
33%
670
August1st to 15thNight
60%
411
16%
1483
19%
409
64%
409
29%
813
August16th to endNight
55%
573
24%
1719
18%
573
60%
573
40%
920
September1st to 15thNight
53%
677
20%
1826
12%
677
56%
677
36%
1096
September16th to endNight
45%
716
22%
1980
12%
716
52%
716
33%
1181
October1st to 15thNight
40%
720
16%
2109
9%
720
47%
720
21%
1426
October16th to endNight
37%
708
22%
2301
10%
708
51%
708
23%
1406
November1st to 15thNight
21%
799
18%
2374
7%
799
33%
799
18%
1518
November16th to endNight
22%
900
14%
2667
4%
900
30%
900
18%
1778
December1st to 15thNight
27%
900
14%
2700
7%
900
34%
900
16%
1854
December16th to endNight
24%
960
16%
2880
5%
960
33%
960
16%
2006

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
9%8%36%5%35%5%6%8%37%
48328
Night
6%7%36%5%345%6%8%42%
47285
Cloud CoverDay
10%8%36%5%35%5%5%8%37%
48329
Night
6%7%36%5%345%5%8%42%
47288
TransparencyDay
43%9%15%20%9%1
47985
Night
39%9%16%22%11%1
47132
SeeingDay
17%18%30%21%9%2
6093
Night
12%17%30%25%12%2
15302

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
25%5%8%5%35%5%7%10%40%
1253
16th to endDay
28%38%7%35%6%7%9%37%
1527
February1st to 15thDay
36%37%6%26%6%7%10%37%
1458
16th to endDay
210%7%9%7%45%5%6%9%31%
1512
March1st to 15thDay
27%5%9%6%35%6%7%10%37%
1842
16th to endDay
6%12%5%9%7%45%5%6%6%28%
2134
April1st to 15thDay
10%14%48%5%345%6%8%27%
2230
16th to endDay
10%14%46%6%345%6%7%30%
2340
May1st to 15thDay
13%9%35%5%35%5%5%7%33%
2490
16th to endDay
23%9%37%6%35%5%6%6%23%
2802
June1st to 15thDay
20%7%46%6%35%5%5%6%28%
2700
16th to endDay
15%6%25%6%36%6%6%7%34%
2700
July1st to 15thDay
10%5%24436%5%6%8%42%
2700
16th to endDay
7%314435%5%5%8%51%
2766
August1st to 15thDay
11%5%14435%6%7%8%42%
2468
16th to endDay
10%3134245%5%8%50%
2483
September1st to 15thDay
14%6%135%24335%50%
2133
16th to endDay
10%5%1332445%7%50%
1980
October1st to 15thDay
11%10%36%5%345%5%7%36%
1849
16th to endDay
6%8%35%5%25%5%7%11%38%
1591
November1st to 15thDay
5%9%35%4246%6%7%43%
1473
16th to endDay
310%6%7%434448%42%
1293
December1st to 15thDay
36%310%7%46%7%6%8%35%
1260
16th to endDay
28%48%6%3447%10%38%
1344
January1st to 15thNight
37%5%7%7%45%6%5%10%36%
2685
16th to endNight
28%5%7%6%35%5%6%9%39%
2707
February1st to 15thNight
27%47%6%35%5%7%9%39%
2394
16th to endNight
38%5%8%7%45%5%5%7%38%
1962
March1st to 15thNight
18%47%6%35%46%10%40%
2118
16th to endNight
410%47%6%35%5%6%10%34%
2085
April1st to 15thNight
9%12%46%5%2446%6%36%
1718
16th to endNight
9%11%37%5%35%447%36%
1620
May1st to 15thNight
9%9%35%5%24448%41%
1460
16th to endNight
23%6%26%424347%31%
1309
June1st to 15thNight
17%5%25%5%25%445%39%
1260
16th to endNight
10%423436%6%6%7%44%
1260
July1st to 15thNight
8%31442345%8%53%
1260
16th to endNight
5%31232346%8%56%
1400
August1st to 15thNight
9%42342345%6%51%
1491
16th to endNight
9%212213348%59%
1719
September1st to 15thNight
12%5%2322345%56%
1826
16th to endNight
11%41331345%8%52%
1980
October1st to 15thNight
10%8%25%5%2446%7%41%
2109
16th to endNight
5%8%244245%6%8%45%
2301
November1st to 15thNight
39%35%4245%6%8%45%
2374
16th to endNight
38%47%6%3445%10%40%
2667
December1st to 15thNight
37%48%6%36%6%5%9%37%
2700
16th to endNight
19%5%9%6%35%5%7%7%37%
2880

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
26%39%6%345%6%10%40%
1253
16th to endDay
28%47%6%36%5%7%9%37%
1527
February1st to 15thDay
37%37%6%36%6%7%9%37%
1458
16th to endDay
211%7%8%7%36%5%6%8%31%
1512
March1st to 15thDay
28%5%9%5%45%5%7%9%37%
1842
16th to endDay
7%13%5%10%7%46%5%5%7%27%
2135
April1st to 15thDay
10%15%47%5%445%6%8%27%
2230
16th to endDay
10%15%46%5%3446%7%30%
2340
May1st to 15thDay
13%10%25%6%35%5%5%7%33%
2490
16th to endDay
23%9%27%6%45%5%5%6%24%
2802
June1st to 15thDay
19%8%36%6%45%5%5%7%28%
2700
16th to endDay
15%6%35%5%45%5%6%7%35%
2700
July1st to 15thDay
10%5%24436%5%6%8%43%
2700
16th to endDay
7%314435%5%5%8%51%
2766
August1st to 15thDay
11%5%234346%7%9%42%
2468
16th to endDay
10%3134245%5%7%50%
2483
September1st to 15thDay
14%5%235%23335%50%
2133
16th to endDay
10%5%13424448%50%
1980
October1st to 15thDay
11%10%36%5%2445%8%36%
1849
16th to endDay
6%9%35%43447%11%38%
1591
November1st to 15thDay
5%9%45%4246%5%7%43%
1473
16th to endDay
410%5%7%434439%42%
1293
December1st to 15thDay
37%48%8%46%7%5%8%35%
1260
16th to endDay
28%5%8%6%35%46%10%38%
1344
January1st to 15thNight
38%5%8%7%45%6%5%10%35%
2685
16th to endNight
28%47%6%35%6%6%9%39%
2707
February1st to 15thNight
38%5%7%6%25%6%5%9%38%
2394
16th to endNight
39%5%8%8%3445%7%37%
1962
March1st to 15thNight
18%48%6%345%7%10%39%
2118
16th to endNight
5%10%47%6%35%5%6%10%34%
2088
April1st to 15thNight
10%11%5%6%4245%6%6%36%
1718
16th to endNight
8%13%37%5%35%446%36%
1620
May1st to 15thNight
10%9%35%433447%42%
1460
16th to endNight
23%6%25%6%34347%32%
1309
June1st to 15thNight
16%6%35%5%25%346%39%
1260
16th to endNight
11%414326%6%6%7%44%
1260
July1st to 15thNight
7%41442345%8%52%
1260
16th to endNight
6%31232445%8%56%
1400
August1st to 15thNight
9%42342445%7%50%
1491
16th to endNight
9%22313348%58%
1719
September1st to 15thNight
13%5%12322335%56%
1826
16th to endNight
11%41332245%7%52%
1980
October1st to 15thNight
11%8%25%5%2445%7%41%
2109
16th to endNight
5%9%244245%6%8%45%
2301
November1st to 15thNight
48%35%4245%6%9%45%
2374
16th to endNight
39%46%6%3446%10%39%
2667
December1st to 15thNight
38%47%6%46%6%6%9%37%
2700
16th to endNight
29%6%9%7%35%5%6%8%36%
2880

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
39%11%17%23%6%2
1253
16th to endDay
42%9%15%20%9%3
1527
February1st to 15thDay
40%10%17%22%7%1
1458
16th to endDay
48%9%14%19%6%
1512
March1st to 15thDay
41%11%19%20%7%
1842
16th to endDay
55%10%14%14%5%
2135
April1st to 15thDay
53%9%14%13%7%1
2230
16th to endDay
52%9%14%16%6%
2340
May1st to 15thDay
49%8%14%18%8%
2490
16th to endDay
58%10%13%11%5%
2807
June1st to 15thDay
54%10%13%13%8%
2700
16th to endDay
45%10%14%20%9%1
2700
July1st to 15thDay
37%10%16%23%10%1
2541
16th to endDay
30%8%14%26%16%3
2593
August1st to 15thDay
35%11%19%23%8%1
2451
16th to endDay
30%7%14%30%13%2
2483
September1st to 15thDay
38%5%11%23%17%3
2133
16th to endDay
33%7%13%29%13%2
1980
October1st to 15thDay
46%9%16%17%9%
1849
16th to endDay
39%10%18%23%7%1
1591
November1st to 15thDay
39%10%17%20%10%
1473
16th to endDay
40%7%20%20%8%2
1293
December1st to 15thDay
45%10%16%19%6%1
1260
16th to endDay
41%9%16%21%10%1
1344
January1st to 15thNight
44%11%16%17%7%2
2685
16th to endNight
39%9%16%19%12%3
2707
February1st to 15thNight
42%10%15%20%10%1
2405
16th to endNight
45%7%13%21%10%1
1962
March1st to 15thNight
39%10%22%20%6%
2118
16th to endNight
44%11%17%18%7%
2088
April1st to 15thNight
45%9%15%19%9%
1718
16th to endNight
48%8%13%21%6%1
1620
May1st to 15thNight
41%7%15%24%9%
1461
16th to endNight
52%7%15%17%6%1
1309
June1st to 15thNight
46%7%15%19%10%
1260
16th to endNight
35%9%16%25%11%1
1260
July1st to 15thNight
28%7%19%28%13%1
1190
16th to endNight
24%8%16%29%17%3
1310
August1st to 15thNight
31%6%17%28%14%1
1483
16th to endNight
24%5%14%31%20%2
1719
September1st to 15thNight
30%5%11%27%18%4
1826
16th to endNight
29%7%16%27%14%4
1980
October1st to 15thNight
40%9%14%21%12%1
2109
16th to endNight
34%9%16%27%11%
2301
November1st to 15thNight
34%10%18%21%12%
2374
16th to endNight
40%9%20%16%9%3
2667
December1st to 15thNight
41%11%18%19%7%1
2700
16th to endNight
43%10%15%21%8%
2880

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
6%8%31%16%23%13%
60
16th to endDay
9%23%31%15%10%9%
64
February1st to 15thDay
16%25%35%18%12
71
16th to endDay
12%22%32%27%5%
171
March1st to 15thDay
13%37%40%6%1
270
16th to endDay
19%32%31%14%1
288
April1st to 15thDay
21%29%32%14%2
269
16th to endDay
27%21%25%18%5%1
270
May1st to 15thDay
20%17%26%22%10%2
345
16th to endDay
24%11%19%25%15%3
517
June1st to 15thDay
19%18%26%22%11%3
495
16th to endDay
13%14%33%22%12%3
495
July1st to 15thDay
12%9%29%26%19%2
475
16th to endDay
10%16%36%23%10%2
435
August1st to 15thDay
12%11%33%27%13%2
315
16th to endDay
12%15%34%24%9%4
332
September1st to 15thDay
24%13%29%23%6%3
315
16th to endDay
14%22%28%22%7%3
315
October1st to 15thDay
21%17%30%21%7%
213
16th to endDay
10%17%29%28%9%6%
99
November1st to 15thDay
25%22%31%14%5%1
90
16th to endDay
13%18%24%15%15%12%
65
December1st to 15thDay
6%20%28%31%11%1
60
16th to endDay
14%20%26%21%14%3
64
January1st to 15thNight
12%23%36%20%6%1
900
16th to endNight
9%22%37%22%7%1
787
February1st to 15thNight
9%19%33%23%10%3
704
16th to endNight
10%12%37%26%11%2
632
March1st to 15thNight
8%23%37%21%7%1
720
16th to endNight
11%17%32%28%7%1
768
April1st to 15thNight
15%23%25%24%9%1
638
16th to endNight
17%13%28%26%12%
540
May1st to 15thNight
13%14%25%29%16%1
438
16th to endNight
24%6%21%27%19%1
375
June1st to 15thNight
18%10%25%25%16%1
360
16th to endNight
11%10%25%31%19%1
360
July1st to 15thNight
9%425%34%25%1
340
16th to endNight
6%5%20%45%21%
376
August1st to 15thNight
9%218%36%32%1
411
16th to endNight
8%8%24%34%21%1
573
September1st to 15thNight
17%6%19%27%22%6%
677
16th to endNight
12%12%26%25%16%5%
716
October1st to 15thNight
17%14%23%27%14%2
720
16th to endNight
12%16%27%30%11%1
708
November1st to 15thNight
12%30%32%18%5%
799
16th to endNight
10%22%39%19%5%2
900
December1st to 15thNight
8%23%34%23%7%2
900
16th to endNight
8%23%34%22%8%1
960
Page generated at 2017-10-17 14:35:18. Version ac04

Copyright 2017 A. Danko


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