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 2017-12-20.

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%
15610
13%
48047
9%
15583
49%
15583
22%
32644

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
65%
405
10%
1477
12%
403
67%
403
25%
867
August16th to endNight
65%
573
21%
1719
17%
573
67%
573
41%
936
September1st to 15thNight
57%
657
17%
1809
13%
657
58%
657
34%
1132
September16th to endNight
56%
716
20%
1980
14%
716
61%
716
37%
1193
October1st to 15thNight
44%
720
16%
2118
10%
720
50%
720
23%
1453
October16th to endNight
46%
768
20%
2496
14%
768
54%
768
24%
1616
November1st to 15thNight
38%
899
17%
2609
11%
899
44%
899
23%
1796
November16th to endNight
36%
975
15%
2902
8%
975
42%
975
22%
1984
December1st to 15thNight
40%
975
13%
2925
9%
975
43%
975
18%
2145
December16th to endNight
41%
984
15%
2951
9%
984
44%
984
18%
2168

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%
48831
Night
8%9%47%6%35%5%6%8%35%
48197
Cloud CoverDay
10%8%36%6%35%5%6%8%35%
48832
Night
8%9%47%6%35%5%6%8%35%
48200
TransparencyDay
45%7%16%21%8%1
48485
Night
44%7%15%21%9%1
48047
SeeingDay
14%6%24%30%18%5%
6289
Night
12%426%37%16%2
15622

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%
2475
16th to endDay
9%4134345%5%9%48%
2483
September1st to 15thDay
12%7%14423346%49%
2150
16th to endDay
9%7%25%5%33448%44%
1980
October1st to 15thDay
14%9%37%6%245%6%7%32%
1839
16th to endDay
7%9%36%6%35%5%6%8%37%
1728
November1st to 15thDay
7%12%5%7%6%35%5%5%7%32%
1567
16th to endDay
6%11%5%7%5%3346%9%36%
1386
December1st to 15thDay
5%10%6%10%9%46%6%5%6%29%
1365
16th to endDay
411%5%9%7%35%6%6%10%28%
1372
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%5%6%10%43%
1485
16th to endNight
7%31432246%9%54%
1719
September1st to 15thNight
11%5%1432345%7%47%
1809
16th to endNight
10%41442445%8%50%
1980
October1st to 15thNight
11%9%26%5%45%46%7%36%
2118
16th to endNight
7%9%35%5%345%7%7%40%
2496
November1st to 15thNight
6%10%46%5%26%5%6%7%37%
2609
16th to endNight
5%12%5%7%6%345%6%7%35%
2902
December1st to 15thNight
410%5%9%8%46%6%5%6%30%
2925
16th to endNight
410%5%9%8%5%6%6%6%7%29%
2951

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%42%
2475
16th to endDay
9%413435%45%9%48%
2483
September1st to 15thDay
13%6%24423336%49%
2150
16th to endDay
9%6%25%5%34349%44%
1980
October1st to 15thDay
15%8%37%5%3445%7%33%
1839
16th to endDay
7%8%36%5%36%5%6%7%38%
1728
November1st to 15thDay
8%11%5%7%7%35%46%7%31%
1567
16th to endDay
6%11%5%7%5%2446%9%35%
1386
December1st to 15thDay
5%13%6%9%8%47%45%5%29%
1365
16th to endDay
5%11%5%10%6%35%7%7%9%27%
1372
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%6%10%42%
1485
16th to endNight
6%5%2332336%9%54%
1719
September1st to 15thNight
11%6%2432446%7%47%
1809
16th to endNight
10%41342346%8%49%
1980
October1st to 15thNight
11%8%36%6%35%45%7%37%
2118
16th to endNight
8%8%35%4345%7%8%39%
2496
November1st to 15thNight
6%10%5%6%5%36%5%6%7%36%
2609
16th to endNight
6%11%48%6%3446%8%34%
2902
December1st to 15thNight
5%9%6%10%8%5%6%6%6%6%30%
2925
16th to endNight
411%5%9%9%46%5%5%7%28%
2951

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%8%22%24%6%1
2458
16th to endDay
30%7%19%29%11%1
2483
September1st to 15thDay
36%6%13%23%15%4
2150
16th to endDay
38%6%12%29%11%2
1980
October1st to 15thDay
48%7%14%20%9%
1839
16th to endDay
42%7%13%26%8%
1728
November1st to 15thDay
49%8%13%19%7%1
1567
16th to endDay
44%5%17%21%8%1
1386
December1st to 15thDay
55%6%13%16%7%1
1365
16th to endDay
47%8%16%18%8%
1372
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
33%9%20%26%8%
1477
16th to endNight
25%6%18%32%14%3
1719
September1st to 15thNight
34%6%13%23%16%5%
1809
16th to endNight
30%6%17%26%14%4
1980
October1st to 15thNight
45%7%13%22%10%1
2118
16th to endNight
38%9%16%24%10%
2496
November1st to 15thNight
43%7%15%20%11%1
2609
16th to endNight
45%7%18%18%8%2
2902
December1st to 15thNight
51%7%13%19%6%1
2925
16th to endNight
52%7%12%21%6%
2951

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%318%31%23%8%
315
16th to endDay
8%5%21%32%21%9%
332
September1st to 15thDay
19%6%20%27%18%7%
315
16th to endDay
12%7%23%30%17%7%
315
October1st to 15thDay
21%6%20%29%15%4
201
16th to endDay
13%6%27%32%14%5%
144
November1st to 15thDay
20%5%24%31%11%5%
135
16th to endDay
8%240%20%18%10%
94
December1st to 15thDay
6%228%36%17%7%
90
16th to endDay
18%120%27%22%9%
72
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%211%37%33%3
405
16th to endNight
10%216%42%27%
573
September1st to 15thNight
15%318%33%25%3
657
16th to endNight
11%321%39%20%2
716
October1st to 15thNight
17%325%32%17%2
720
16th to endNight
12%427%39%13%1
768
November1st to 15thNight
11%7%33%35%10%2
899
16th to endNight
11%5%34%35%10%2
975
December1st to 15thNight
10%430%37%15%2
975
16th to endNight
9%328%42%13%3
984
Page generated at 2017-12-21 05:04:51. Version ac04

Copyright 2017 A. Danko


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