High River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the High River clear sky chart from 2005-11-05 to 2017-09-18.

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
40%
15200
15%
46805
9%
15169
46%
15169
23%
30682

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
32%
898
13%
2685
7%
895
37%
895
17%
1909
January16th to endNight
34%
810
19%
2730
13%
810
43%
810
20%
1749
February1st to 15thNight
38%
701
14%
2402
10%
697
45%
697
20%
1559
February16th to endNight
37%
632
15%
1974
10%
632
44%
632
18%
1396
March1st to 15thNight
30%
720
16%
2112
8%
720
40%
720
20%
1454
March16th to endNight
29%
768
12%
2095
3%
768
35%
768
18%
1540
April1st to 15thNight
30%
626
12%
1706
5%
626
34%
626
18%
1253
April16th to endNight
33%
540
13%
1620
8%
540
39%
540
20%
1121
May1st to 15thNight
41%
437
12%
1441
11%
437
46%
437
22%
932
May16th to endNight
41%
374
5%
1309
3%
374
43%
374
16%
917
June1st to 15thNight
38%
360
2%
1260
0%
360
38%
360
18%
840
June16th to endNight
54%
360
2%
1260
0%
360
54%
360
28%
740
July1st to 15thNight
58%
340
3%
1190
0%
340
59%
340
29%
679
July16th to endNight
59%
376
12%
1288
11%
354
65%
354
34%
678
August1st to 15thNight
64%
414
13%
1486
16%
412
67%
412
29%
833
August16th to endNight
57%
573
24%
1719
19%
573
61%
573
43%
900
September1st to 15thNight
55%
663
19%
1818
13%
663
58%
663
39%
1072
September16th to endNight
49%
667
22%
1847
13%
667
56%
667
39%
1080
October1st to 15thNight
44%
660
18%
1936
10%
660
51%
660
23%
1320
October16th to endNight
44%
704
21%
2288
13%
704
54%
704
27%
1393
November1st to 15thNight
30%
817
19%
2392
10%
817
40%
817
24%
1547
November16th to endNight
33%
900
16%
2667
8%
900
40%
900
23%
1773
December1st to 15thNight
37%
900
13%
2700
9%
900
40%
900
18%
1945
December16th to endNight
34%
960
16%
2880
8%
960
40%
960
18%
2052

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%5%35%5%6%8%36%
48022
Night
7%8%46%6%35%5%5%8%38%
46956
Cloud CoverDay
10%7%36%5%35%5%6%8%37%
48023
Night
7%8%36%6%35%5%5%8%38%
46959
TransparencyDay
43%6%16%22%9%1
47677
Night
42%6%15%22%10%1
46805
SeeingDay
14%13%30%25%12%2
6006
Night
12%8%29%33%13%2
15207

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
5%11%47%5%35%46%8%37%
1253
16th to endDay
410%47%7%445%5%9%35%
1506
February1st to 15thDay
5%10%47%7%26%5%7%8%32%
1460
16th to endDay
310%7%10%7%46%5%6%9%27%
1497
March1st to 15thDay
39%48%6%36%6%5%9%35%
1848
16th to endDay
8%12%5%8%7%36%6%5%7%27%
2126
April1st to 15thDay
11%12%47%6%45%5%6%7%27%
2241
16th to endDay
13%11%36%5%345%6%7%30%
2340
May1st to 15thDay
12%7%36%5%46%5%6%7%35%
2506
16th to endDay
21%7%36%6%45%5%5%8%26%
2802
June1st to 15thDay
19%8%36%5%35%5%7%7%27%
2700
16th to endDay
13%425%5%46%5%6%8%35%
2700
July1st to 15thDay
8%5%14435%7%6%8%43%
2700
16th to endDay
4414435%5%6%9%50%
2790
August1st to 15thDay
12%5%134346%6%9%43%
2466
16th to endDay
8%3133245%5%9%50%
2483
September1st to 15thDay
14%5%13423336%50%
2141
16th to endDay
9%5%2443345%9%47%
1838
October1st to 15thDay
13%8%38%7%2336%7%34%
1691
16th to endDay
6%9%25%6%45%5%7%10%36%
1584
November1st to 15thDay
7%9%46%5%46%5%6%7%36%
1455
16th to endDay
5%11%6%7%42346%10%37%
1291
December1st to 15thDay
312%5%9%8%6%7%5%5%6%28%
1260
16th to endDay
310%5%7%6%45%7%6%10%32%
1344
January1st to 15thNight
410%5%9%8%46%5%6%9%29%
2685
16th to endNight
49%5%8%6%345%6%8%37%
2730
February1st to 15thNight
5%11%5%7%5%45%5%5%7%37%
2391
16th to endNight
5%10%6%9%7%46%5%5%6%32%
1974
March1st to 15thNight
39%5%8%7%37%6%5%9%32%
2112
16th to endNight
6%12%5%9%6%35%5%6%8%29%
2092
April1st to 15thNight
12%11%5%6%5%35%45%6%31%
1706
16th to endNight
11%10%46%5%25%447%35%
1620
May1st to 15thNight
9%8%37%6%3445%9%38%
1440
16th to endNight
19%6%25%7%345%5%7%31%
1309
June1st to 15thNight
16%6%37%6%15%449%34%
1260
16th to endNight
10%4244245%7%9%43%
1260
July1st to 15thNight
6%3245%3445%8%50%
1260
16th to endNight
5%31343447%8%53%
1376
August1st to 15thNight
7%4245%35%45%7%49%
1494
16th to endNight
8%31222236%8%58%
1719
September1st to 15thNight
11%423322347%54%
1818
16th to endNight
10%42332346%8%51%
1847
October1st to 15thNight
11%7%36%6%25%5%5%6%37%
1936
16th to endNight
8%8%245%3446%8%43%
2288
November1st to 15thNight
5%8%26%5%35%45%8%41%
2392
16th to endNight
5%10%5%7%6%2445%9%37%
2667
December1st to 15thNight
39%5%9%8%48%5%6%8%30%
2700
16th to endNight
311%5%9%8%46%5%6%7%31%
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
6%11%46%6%35%5%5%8%36%
1253
16th to endDay
5%10%47%6%445%6%8%35%
1506
February1st to 15thDay
5%10%5%7%6%37%6%7%8%32%
1460
16th to endDay
410%7%9%8%37%5%6%8%28%
1497
March1st to 15thDay
39%5%8%6%46%6%5%9%34%
1848
16th to endDay
9%13%5%8%6%35%5%6%7%27%
2127
April1st to 15thDay
11%12%5%7%7%35%5%5%7%27%
2241
16th to endDay
14%10%36%6%35%46%8%30%
2340
May1st to 15thDay
12%7%26%5%26%5%6%7%36%
2506
16th to endDay
21%6%36%6%35%45%7%27%
2802
June1st to 15thDay
18%6%45%6%35%5%6%7%28%
2700
16th to endDay
13%425%5%46%5%7%8%35%
2700
July1st to 15thDay
9%414435%6%7%9%44%
2700
16th to endDay
5%313435%6%7%8%50%
2790
August1st to 15thDay
11%5%234245%7%9%43%
2466
16th to endDay
8%31332446%8%51%
2483
September1st to 15thDay
13%5%24324336%51%
2141
16th to endDay
9%5%24434448%47%
1838
October1st to 15thDay
13%8%36%7%2445%7%35%
1691
16th to endDay
6%9%36%6%346%6%9%37%
1584
November1st to 15thDay
8%9%5%6%5%46%6%47%35%
1455
16th to endDay
5%11%6%8%42336%9%37%
1291
December1st to 15thDay
311%6%10%8%6%7%6%46%28%
1260
16th to endDay
310%5%9%6%36%6%5%10%31%
1344
January1st to 15thNight
410%5%9%8%36%6%5%9%29%
2685
16th to endNight
5%10%48%5%345%6%9%37%
2730
February1st to 15thNight
5%11%48%5%35%5%6%8%36%
2391
16th to endNight
5%11%6%9%7%46%5%5%6%31%
1974
March1st to 15thNight
410%5%8%6%45%6%7%9%32%
2112
16th to endNight
6%12%5%8%7%36%46%9%28%
2095
April1st to 15thNight
13%11%5%5%6%345%5%6%31%
1706
16th to endNight
12%11%36%5%245%6%6%35%
1620
May1st to 15thNight
9%8%36%5%35%46%7%39%
1440
16th to endNight
19%7%25%6%345%5%8%30%
1309
June1st to 15thNight
15%7%37%5%3445%8%34%
1260
16th to endNight
11%415%3245%7%9%43%
1260
July1st to 15thNight
6%3145%35%45%8%49%
1260
16th to endNight
6%3134245%6%8%53%
1376
August1st to 15thNight
7%415%5%3445%8%49%
1494
16th to endNight
7%41221325%8%58%
1719
September1st to 15thNight
11%413323346%54%
1818
16th to endNight
10%42332435%8%52%
1847
October1st to 15thNight
12%7%26%5%35%5%5%6%37%
1936
16th to endNight
8%8%245%245%6%8%43%
2288
November1st to 15thNight
6%8%36%6%35%46%8%41%
2392
16th to endNight
5%10%5%7%5%3446%8%37%
2667
December1st to 15thNight
49%49%8%5%8%5%6%7%30%
2700
16th to endNight
311%5%10%8%46%5%6%7%30%
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
44%5%16%24%6%2
1253
16th to endDay
44%5%16%19%9%3
1506
February1st to 15thDay
46%7%16%20%7%2
1460
16th to endDay
52%5%15%18%7%
1497
March1st to 15thDay
44%7%19%20%7%
1848
16th to endDay
52%7%14%18%6%
2127
April1st to 15thDay
53%6%14%17%6%1
2241
16th to endDay
50%6%14%19%8%1
2340
May1st to 15thDay
44%5%15%22%10%
2506
16th to endDay
54%6%14%17%6%
2807
June1st to 15thDay
51%8%15%17%7%1
2700
16th to endDay
42%8%17%21%7%1
2700
July1st to 15thDay
33%8%20%26%9%1
2541
16th to endDay
28%8%18%28%13%2
2615
August1st to 15thDay
34%8%22%25%7%1
2449
16th to endDay
28%6%17%32%13%1
2483
September1st to 15thDay
35%413%24%17%4
2141
16th to endDay
34%6%10%32%12%3
1838
October1st to 15thDay
46%6%14%20%9%1
1691
16th to endDay
39%8%16%26%7%1
1584
November1st to 15thDay
46%7%14%21%8%1
1455
16th to endDay
42%418%22%9%2
1291
December1st to 15thDay
55%6%14%17%6%
1260
16th to endDay
45%6%15%21%9%1
1344
January1st to 15thNight
49%6%16%18%6%2
2685
16th to endNight
42%6%14%20%11%3
2730
February1st to 15thNight
44%5%15%22%10%1
2402
16th to endNight
51%5%11%21%10%
1974
March1st to 15thNight
44%7%17%22%6%
2112
16th to endNight
51%7%14%18%7%
2095
April1st to 15thNight
52%6%12%18%10%
1706
16th to endNight
46%6%14%23%7%1
1620
May1st to 15thNight
42%6%13%26%11%
1441
16th to endNight
50%7%16%17%5%1
1309
June1st to 15thNight
46%6%15%20%9%
1260
16th to endNight
34%7%20%26%10%1
1260
July1st to 15thNight
32%7%19%28%11%
1190
16th to endNight
26%8%18%30%13%3
1288
August1st to 15thNight
31%7%19%28%11%1
1486
16th to endNight
23%5%15%33%18%3
1719
September1st to 15thNight
30%414%25%19%5%
1818
16th to endNight
30%416%28%14%5%
1847
October1st to 15thNight
44%6%14%20%12%1
1936
16th to endNight
36%6%17%26%12%
2288
November1st to 15thNight
39%6%14%23%14%
2392
16th to endNight
43%6%18%18%10%3
2667
December1st to 15thNight
50%7%15%19%6%
2700
16th to endNight
50%6%13%22%7%
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
13%325%20%26%11%
60
16th to endDay
15%10%23%28%12%9%
64
February1st to 15thDay
11%14%36%26%9%1
71
16th to endDay
9%13%37%30%9%
156
March1st to 15thDay
8%28%45%13%4
270
16th to endDay
12%28%35%17%5%1
288
April1st to 15thDay
21%25%29%17%5%
269
16th to endDay
22%13%33%23%6%
270
May1st to 15thDay
17%15%28%22%13%3
363
16th to endDay
24%8%21%27%15%3
517
June1st to 15thDay
18%11%30%24%12%2
495
16th to endDay
13%8%32%29%11%3
495
July1st to 15thDay
10%7%27%30%21%2
475
16th to endDay
9%11%33%27%15%2
459
August1st to 15thDay
12%7%30%32%12%4
315
16th to endDay
9%9%37%25%11%4
332
September1st to 15thDay
19%11%28%26%11%3
315
16th to endDay
10%19%28%28%9%3
264
October1st to 15thDay
18%15%27%20%16%
153
16th to endDay
8%10%26%36%13%5%
96
November1st to 15thDay
17%18%27%26%5%3
90
16th to endDay
418%23%24%15%13%
65
December1st to 15thDay
6%13%36%26%13%3
60
16th to endDay
10%6%25%31%17%9%
64
January1st to 15thNight
10%13%30%32%11%1
900
16th to endNight
11%10%32%33%10%1
810
February1st to 15thNight
11%11%27%32%14%3
704
16th to endNight
10%7%30%33%14%2
632
March1st to 15thNight
9%10%39%28%9%1
720
16th to endNight
13%10%35%31%8%1
768
April1st to 15thNight
17%12%30%27%11%1
626
16th to endNight
18%9%28%31%12%
540
May1st to 15thNight
13%10%27%30%17%1
438
16th to endNight
23%5%22%31%17%
375
June1st to 15thNight
18%7%28%26%16%2
360
16th to endNight
13%421%40%18%1
360
July1st to 15thNight
9%320%40%25%1
340
16th to endNight
9%223%40%22%1
376
August1st to 15thNight
10%315%38%28%2
414
16th to endNight
9%424%37%23%1
573
September1st to 15thNight
15%5%19%33%23%3
663
16th to endNight
11%5%29%34%14%4
667
October1st to 15thNight
17%6%25%34%13%3
660
16th to endNight
13%6%27%36%13%1
704
November1st to 15thNight
9%14%37%29%6%1
817
16th to endNight
11%11%35%31%8%2
900
December1st to 15thNight
9%10%31%33%11%3
900
16th to endNight
10%7%33%35%11%1
960
Page generated at 2017-09-19 05:32:32. Version ac04

Copyright 2017 A. Danko


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