Chestermere
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chestermere 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
44%
15066
13%
46441
9%
15039
48%
15039
22%
31632

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%
896
11%
2685
7%
895
38%
895
15%
2003
January16th to endNight
41%
825
17%
2745
13%
825
48%
825
20%
1843
February1st to 15thNight
44%
698
13%
2410
12%
696
49%
696
19%
1608
February16th to endNight
42%
632
13%
1983
11%
632
47%
632
18%
1402
March1st to 15thNight
38%
720
13%
2112
9%
720
44%
720
20%
1514
March16th to endNight
36%
768
11%
2094
4%
768
40%
768
18%
1567
April1st to 15thNight
35%
623
11%
1703
5%
623
38%
623
18%
1280
April16th to endNight
38%
540
12%
1620
9%
540
43%
540
20%
1149
May1st to 15thNight
43%
426
11%
1417
11%
426
47%
426
22%
923
May16th to endNight
47%
374
4%
1309
3%
374
48%
374
16%
938
June1st to 15thNight
43%
360
0%
1260
0%
360
43%
360
15%
905
June16th to endNight
54%
360
0%
1260
0%
360
54%
360
23%
815
July1st to 15thNight
64%
340
2%
1190
0%
340
65%
340
27%
706
July16th to endNight
64%
376
10%
1273
11%
354
66%
354
31%
701
August1st to 15thNight
64%
393
11%
1441
13%
391
67%
391
25%
847
August16th to endNight
64%
525
19%
1575
15%
525
67%
525
40%
863
September1st to 15thNight
57%
602
18%
1658
14%
602
59%
602
33%
1049
September16th to endNight
55%
656
19%
1815
13%
656
61%
656
38%
1086
October1st to 15thNight
45%
660
17%
1941
11%
660
50%
660
22%
1339
October16th to endNight
47%
704
19%
2288
13%
704
55%
704
24%
1489
November1st to 15thNight
38%
828
17%
2403
11%
828
44%
828
24%
1625
November16th to endNight
36%
900
14%
2679
8%
900
42%
900
22%
1839
December1st to 15thNight
39%
900
11%
2700
8%
900
41%
900
17%
2027
December16th to endNight
41%
960
15%
2880
9%
960
44%
960
18%
2114

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%8%36%6%35%5%6%8%34%
47570
Night
8%9%47%6%35%5%6%8%35%
46591
Cloud CoverDay
10%8%36%6%35%5%6%8%34%
47571
Night
8%9%47%6%35%5%6%8%34%
46594
TransparencyDay
45%7%16%21%7%1
47224
Night
45%7%15%21%8%1
46441
SeeingDay
14%6%24%30%18%5%
5878
Night
12%426%37%16%2
15078

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
7%12%47%5%35%6%5%8%33%
1253
16th to endDay
6%10%48%7%45%6%7%7%32%
1490
February1st to 15thDay
6%10%6%7%6%36%7%5%7%31%
1452
16th to endDay
5%11%6%10%6%46%5%6%7%28%
1491
March1st to 15thDay
411%5%8%7%5%5%5%5%7%31%
1848
16th to endDay
9%14%5%8%6%45%46%7%26%
2126
April1st to 15thDay
11%14%5%8%6%35%5%5%8%24%
2245
16th to endDay
13%11%47%6%35%5%6%7%29%
2340
May1st to 15thDay
11%8%46%6%345%6%7%34%
2532
16th to endDay
21%7%35%5%346%6%8%25%
2802
June1st to 15thDay
20%6%36%5%36%5%6%7%26%
2700
16th to endDay
12%6%26%6%345%8%9%33%
2700
July1st to 15thDay
10%4145%36%6%7%9%41%
2700
16th to endDay
5%3245%25%5%7%10%47%
2807
August1st to 15thDay
11%5%25%4345%7%9%41%
2425
16th to endDay
9%4135%345%5%9%46%
2275
September1st to 15thDay
12%7%14423346%48%
1971
16th to endDay
9%6%35%5%33448%43%
1815
October1st to 15thDay
15%8%37%6%245%5%7%32%
1686
16th to endDay
6%10%36%6%35%5%5%8%38%
1584
November1st to 15thDay
8%11%47%6%35%5%5%7%34%
1444
16th to endDay
6%12%5%7%5%3346%8%35%
1280
December1st to 15thDay
5%11%6%10%9%46%6%5%6%26%
1260
16th to endDay
411%49%7%36%6%6%10%29%
1344
January1st to 15thNight
5%11%5%10%9%45%6%6%7%26%
2685
16th to endNight
5%12%47%435%6%7%9%33%
2745
February1st to 15thNight
6%10%47%7%45%46%8%34%
2399
16th to endNight
411%5%9%8%47%5%5%8%28%
1983
March1st to 15thNight
410%5%8%7%45%6%7%9%29%
2112
16th to endNight
7%14%5%8%5%36%5%6%7%27%
2091
April1st to 15thNight
12%12%46%6%46%5%5%7%27%
1703
16th to endNight
12%11%47%5%3446%8%31%
1620
May1st to 15thNight
10%9%46%5%35%36%7%38%
1416
16th to endNight
18%7%35%5%36%46%9%29%
1309
June1st to 15thNight
16%8%46%6%35%5%6%8%28%
1260
16th to endNight
12%325%6%36%5%7%9%35%
1260
July1st to 15thNight
6%424436%6%6%9%45%
1260
16th to endNight
6%4235%35%45%7%53%
1360
August1st to 15thNight
10%225%445%46%10%42%
1449
16th to endNight
7%31432246%10%53%
1575
September1st to 15thNight
11%6%143245%5%8%46%
1658
16th to endNight
10%41342445%8%50%
1815
October1st to 15thNight
12%8%36%5%35%46%7%36%
1941
16th to endNight
7%9%35%5%245%7%8%39%
2288
November1st to 15thNight
6%9%46%5%25%6%6%7%39%
2403
16th to endNight
5%12%5%7%5%345%6%7%35%
2679
December1st to 15thNight
411%6%9%8%5%6%6%5%7%28%
2700
16th to endNight
410%5%9%8%5%6%6%6%7%29%
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
8%11%48%5%345%6%8%33%
1253
16th to endDay
7%11%48%7%35%6%6%7%31%
1490
February1st to 15thDay
7%11%48%6%37%5%5%7%31%
1452
16th to endDay
5%11%6%10%7%45%5%6%7%27%
1491
March1st to 15thDay
5%12%6%8%8%46%5%5%8%31%
1848
16th to endDay
10%13%6%8%6%36%46%7%26%
2127
April1st to 15thDay
12%13%5%7%6%35%6%6%7%24%
2245
16th to endDay
14%10%37%6%345%5%8%30%
2340
May1st to 15thDay
11%9%36%6%35%5%5%7%35%
2532
16th to endDay
20%8%35%5%35%5%6%8%26%
2802
June1st to 15thDay
20%6%36%6%35%5%6%8%26%
2700
16th to endDay
12%6%35%6%345%7%9%34%
2700
July1st to 15thDay
9%4245%26%5%6%9%41%
2700
16th to endDay
6%313435%5%8%9%48%
2807
August1st to 15thDay
11%5%244245%6%9%41%
2425
16th to endDay
9%413435%5%5%9%46%
2275
September1st to 15thDay
13%6%24423335%48%
1971
16th to endDay
10%6%25%5%34449%43%
1815
October1st to 15thDay
15%8%37%6%35%45%7%34%
1686
16th to endDay
7%8%46%5%36%5%6%6%39%
1584
November1st to 15thDay
8%11%5%7%6%35%46%7%32%
1444
16th to endDay
6%12%5%8%5%3446%8%34%
1280
December1st to 15thDay
5%13%6%10%8%47%5%5%5%26%
1260
16th to endDay
411%410%6%35%7%7%9%27%
1344
January1st to 15thNight
5%12%5%10%8%46%6%6%8%24%
2685
16th to endNight
6%11%47%5%36%5%7%9%32%
2745
February1st to 15thNight
7%9%47%7%45%5%5%8%33%
2399
16th to endNight
5%11%5%10%8%45%6%5%8%28%
1983
March1st to 15thNight
411%6%7%7%47%6%6%9%28%
2112
16th to endNight
7%13%7%8%5%46%5%6%7%26%
2094
April1st to 15thNight
12%11%5%6%7%35%5%6%8%26%
1703
16th to endNight
11%11%37%6%2445%9%32%
1620
May1st to 15thNight
10%8%47%43445%6%39%
1416
16th to endNight
18%6%26%5%45%5%6%7%30%
1309
June1st to 15thNight
17%6%5%7%5%47%5%6%6%27%
1260
16th to endNight
12%5%26%5%46%5%6%9%36%
1260
July1st to 15thNight
6%4245%45%6%8%8%43%
1260
16th to endNight
5%3145%35%45%9%51%
1360
August1st to 15thNight
9%415%5%346%7%10%41%
1449
16th to endNight
7%42332346%9%52%
1575
September1st to 15thNight
11%6%2442446%7%45%
1658
16th to endNight
10%41342346%8%50%
1815
October1st to 15thNight
12%8%36%6%35%5%5%7%36%
1941
16th to endNight
8%8%35%4345%7%8%39%
2288
November1st to 15thNight
6%9%5%5%5%36%5%6%7%37%
2403
16th to endNight
6%12%5%8%6%3446%8%34%
2679
December1st to 15thNight
5%10%6%10%8%5%6%6%6%6%28%
2700
16th to endNight
410%5%9%9%46%5%5%7%28%
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
46%6%16%23%5%1
1253
16th to endDay
47%8%14%15%9%3
1490
February1st to 15thDay
49%7%16%17%6%1
1452
16th to endDay
52%8%14%17%7%
1491
March1st to 15thDay
50%7%18%16%6%
1848
16th to endDay
55%8%14%17%4
2127
April1st to 15thDay
55%7%14%14%7%
2245
16th to endDay
51%7%13%17%8%1
2340
May1st to 15thDay
46%7%14%21%9%
2532
16th to endDay
54%7%14%18%5%
2807
June1st to 15thDay
53%8%13%17%5%1
2700
16th to endDay
43%9%18%23%5%1
2700
July1st to 15thDay
36%9%21%23%7%
2541
16th to endDay
29%9%21%28%10%1
2631
August1st to 15thDay
37%9%23%23%5%1
2408
16th to endDay
33%7%19%28%10%1
2275
September1st to 15thDay
37%6%13%23%15%3
1971
16th to endDay
38%6%11%29%10%3
1815
October1st to 15thDay
47%7%14%20%9%
1686
16th to endDay
42%7%13%27%7%1
1584
November1st to 15thDay
47%7%13%20%7%1
1444
16th to endDay
45%5%17%20%8%1
1280
December1st to 15thDay
58%6%13%14%6%
1260
16th to endDay
46%8%16%18%8%
1344
January1st to 15thNight
53%7%14%16%5%2
2685
16th to endNight
44%7%15%19%9%3
2745
February1st to 15thNight
47%5%15%20%9%1
2410
16th to endNight
50%6%11%19%10%
1983
March1st to 15thNight
48%8%16%19%5%
2112
16th to endNight
53%6%14%17%7%
2094
April1st to 15thNight
54%6%13%16%9%
1703
16th to endNight
49%7%13%21%7%1
1620
May1st to 15thNight
42%7%13%24%11%
1417
16th to endNight
50%9%15%17%5%1
1309
June1st to 15thNight
51%8%14%16%7%1
1260
16th to endNight
40%8%21%22%7%
1260
July1st to 15thNight
33%9%22%27%7%
1190
16th to endNight
28%8%18%32%10%1
1273
August1st to 15thNight
34%9%21%26%8%
1441
16th to endNight
25%6%19%31%12%3
1575
September1st to 15thNight
34%7%14%22%16%4
1658
16th to endNight
30%6%18%26%13%4
1815
October1st to 15thNight
45%7%13%21%9%1
1941
16th to endNight
39%9%15%25%9%
2288
November1st to 15thNight
42%7%15%21%11%1
2403
16th to endNight
46%6%18%17%8%2
2679
December1st to 15thNight
53%7%14%18%4
2700
16th to endNight
52%7%12%21%6%
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
16%310%31%13%25%
60
16th to endDay
7%325%28%21%14%
64
February1st to 15thDay
17%5%17%37%18%2
69
16th to endDay
12%428%38%17%
150
March1st to 15thDay
8%13%42%27%7%
270
16th to endDay
11%13%38%24%9%2
288
April1st to 15thDay
18%11%30%26%12%1
269
16th to endDay
23%9%22%28%11%4
270
May1st to 15thDay
14%7%27%25%19%5%
378
16th to endDay
21%420%24%23%5%
517
June1st to 15thDay
19%6%22%31%16%3
495
16th to endDay
13%426%32%18%4
495
July1st to 15thDay
12%218%32%26%7%
475
16th to endDay
8%323%36%21%5%
476
August1st to 15thDay
13%419%32%22%9%
300
16th to endDay
10%6%24%32%18%7%
268
September1st to 15thDay
20%6%20%28%16%7%
255
16th to endDay
12%9%26%32%15%4
255
October1st to 15thDay
21%8%17%33%14%3
151
16th to endDay
13%119%38%18%8%
96
November1st to 15thDay
20%6%23%36%10%3
90
16th to endDay
7%131%15%26%15%
63
December1st to 15thDay
6%31%41%16%3
60
16th to endDay
14%120%28%25%10%
64
January1st to 15thNight
11%7%30%35%12%2
900
16th to endNight
13%5%29%37%12%1
825
February1st to 15thNight
11%6%23%36%18%3
704
16th to endNight
10%326%38%18%3
632
March1st to 15thNight
9%433%36%13%2
720
16th to endNight
13%430%38%11%1
768
April1st to 15thNight
16%5%30%31%15%1
623
16th to endNight
18%5%26%36%13%
540
May1st to 15thNight
12%5%29%33%18%
427
16th to endNight
22%320%30%22%
375
June1st to 15thNight
18%423%34%16%1
360
16th to endNight
14%320%41%20%1
360
July1st to 15thNight
7%217%40%30%2
340
16th to endNight
7%219%47%21%2
376
August1st to 15thNight
11%212%36%33%3
393
16th to endNight
10%217%42%26%
525
September1st to 15thNight
16%317%32%26%3
602
16th to endNight
11%322%39%19%2
656
October1st to 15thNight
17%325%33%18%2
660
16th to endNight
13%326%39%14%1
704
November1st to 15thNight
11%6%35%35%9%2
828
16th to endNight
12%5%34%34%10%2
900
December1st to 15thNight
10%431%37%14%2
900
16th to endNight
9%327%42%13%3
960
Page generated at 2017-08-13 12:16:30. Version ac04

Copyright 2017 A. Danko


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