Cardston
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cardston clear sky chart from 2005-11-05 to 2017-09-23.

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
35%
15272
16%
46861
8%
15240
43%
15240
25%
29223

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
24%
900
13%
2685
5%
895
31%
895
17%
1838
January16th to endNight
28%
783
18%
2703
11%
783
39%
783
19%
1709
February1st to 15thNight
27%
700
14%
2360
7%
698
37%
698
18%
1558
February16th to endNight
28%
632
13%
1974
8%
632
36%
632
17%
1356
March1st to 15thNight
27%
720
13%
2095
4%
720
37%
720
23%
1361
March16th to endNight
29%
768
12%
2112
2%
768
37%
768
20%
1476
April1st to 15thNight
29%
624
13%
1713
4%
624
35%
624
22%
1151
April16th to endNight
31%
540
16%
1620
8%
540
39%
540
25%
1047
May1st to 15thNight
40%
494
14%
1518
10%
494
47%
494
27%
936
May16th to endNight
42%
375
10%
1309
8%
374
46%
374
19%
864
June1st to 15thNight
40%
360
6%
1260
2%
360
43%
360
26%
755
June16th to endNight
44%
360
7%
1260
2%
360
48%
360
29%
702
July1st to 15thNight
60%
340
10%
1190
5%
340
66%
340
44%
558
July16th to endNight
64%
376
19%
1314
20%
354
74%
354
45%
576
August1st to 15thNight
65%
456
21%
1528
20%
454
72%
454
43%
748
August16th to endNight
59%
573
29%
1719
21%
573
65%
573
45%
878
September1st to 15thNight
53%
657
21%
1830
13%
657
57%
657
41%
1040
September16th to endNight
47%
688
23%
1903
13%
688
55%
688
38%
1099
October1st to 15thNight
38%
660
20%
1922
10%
660
48%
660
27%
1207
October16th to endNight
34%
704
20%
2279
9%
704
48%
704
25%
1348
November1st to 15thNight
23%
802
18%
2377
7%
802
35%
802
23%
1467
November16th to endNight
23%
900
14%
2610
4%
900
34%
900
21%
1713
December1st to 15thNight
28%
900
14%
2700
7%
900
35%
900
18%
1866
December16th to endNight
22%
960
14%
2880
4%
960
31%
960
17%
1970

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%7%35%5%35%5%5%8%42%
48080
Night
6%7%35%5%3445%8%44%
47014
Cloud CoverDay
9%7%35%5%35%5%5%7%42%
48081
Night
6%7%35%5%2445%8%44%
47017
TransparencyDay
39%6%15%24%11%2
47738
Night
37%6%18%24%11%2
46861
SeeingDay
14%13%27%26%14%3
5995
Night
12%13%31%30%11%1
15277

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
37%5%7%7%4446%8%38%
1253
16th to endDay
310%48%7%35%45%9%35%
1531
February1st to 15thDay
410%37%6%45%5%6%9%36%
1503
16th to endDay
412%5%10%6%25%5%5%9%34%
1499
March1st to 15thDay
18%48%6%346%6%8%40%
1864
16th to endDay
7%10%47%6%36%5%6%8%31%
2111
April1st to 15thDay
9%10%46%6%35%6%6%8%31%
2234
16th to endDay
12%10%27%6%25%46%6%35%
2340
May1st to 15thDay
10%8%36%5%245%5%7%39%
2433
16th to endDay
22%8%26%6%35%5%5%6%27%
2802
June1st to 15thDay
14%5%25%5%46%5%6%8%34%
2700
16th to endDay
10%414435%46%9%44%
2700
July1st to 15thDay
5%314435%5%6%7%52%
2700
16th to endDay
431232345%7%61%
2763
August1st to 15thDay
9%31332446%9%50%
2423
16th to endDay
7%313323448%55%
2483
September1st to 15thDay
13%413323246%53%
2126
16th to endDay
11%314423447%52%
1893
October1st to 15thDay
11%10%36%433446%42%
1708
16th to endDay
5%7%35%6%45%5%7%7%40%
1592
November1st to 15thDay
5%8%35%6%15%5%6%8%44%
1468
16th to endDay
410%5%8%6%23449%39%
1350
December1st to 15thDay
39%5%7%8%36%6%6%8%34%
1260
16th to endDay
28%5%8%5%36%6%7%7%36%
1344
January1st to 15thNight
37%48%8%35%5%6%9%36%
2685
16th to endNight
39%47%5%345%6%8%41%
2703
February1st to 15thNight
49%48%6%35%5%5%8%37%
2349
16th to endNight
210%5%9%6%46%5%5%7%34%
1974
March1st to 15thNight
17%47%6%4446%10%42%
2095
16th to endNight
7%9%46%5%26%5%7%10%35%
2109
April1st to 15thNight
9%10%343245%7%8%38%
1713
16th to endNight
10%11%3443445%6%42%
1620
May1st to 15thNight
8%7%25%5%3446%7%44%
1517
16th to endNight
20%6%244235%5%9%35%
1309
June1st to 15thNight
13%5%245%2445%8%45%
1260
16th to endNight
9%4133345%7%6%49%
1260
July1st to 15thNight
5%3231335%8%62%
1260
16th to endNight
5%11221335%6%66%
1404
August1st to 15thNight
6%21322335%9%59%
1536
16th to endNight
7%213312446%62%
1719
September1st to 15thNight
12%412213345%58%
1830
16th to endNight
10%41332345%6%53%
1903
October1st to 15thNight
12%7%2342346%8%44%
1922
16th to endNight
6%6%35%4345%5%8%47%
2279
November1st to 15thNight
47%35%5%2446%7%48%
2377
16th to endNight
39%47%6%3446%8%41%
2610
December1st to 15thNight
39%5%7%6%35%6%5%8%36%
2700
16th to endNight
210%5%8%7%345%6%8%36%
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
39%5%7%7%36%45%8%38%
1253
16th to endDay
310%48%6%445%5%9%36%
1531
February1st to 15thDay
5%9%37%7%36%5%6%9%35%
1503
16th to endDay
412%49%6%25%46%8%34%
1499
March1st to 15thDay
18%5%7%6%26%6%5%8%40%
1864
16th to endDay
7%11%5%5%6%36%6%6%9%31%
2112
April1st to 15thDay
10%9%45%5%36%6%6%9%31%
2234
16th to endDay
13%9%36%6%35%5%5%5%36%
2340
May1st to 15thDay
11%8%35%5%35%46%6%40%
2433
16th to endDay
22%8%25%6%35%446%28%
2802
June1st to 15thDay
15%5%35%5%35%5%5%7%36%
2700
16th to endDay
11%414435%5%6%8%44%
2700
July1st to 15thDay
5%3134246%6%8%53%
2700
16th to endDay
421322445%7%61%
2763
August1st to 15thDay
9%31232447%9%51%
2423
16th to endDay
7%31342345%7%55%
2483
September1st to 15thDay
14%413323335%53%
2126
16th to endDay
12%314424346%52%
1893
October1st to 15thDay
11%9%35%5%23436%42%
1708
16th to endDay
6%7%36%6%36%46%8%39%
1592
November1st to 15thDay
5%8%446%25%47%8%42%
1468
16th to endDay
5%10%6%7%6%3335%8%39%
1350
December1st to 15thDay
311%5%7%7%36%7%7%7%33%
1260
16th to endDay
28%5%7%6%46%6%6%8%35%
1344
January1st to 15thNight
37%48%7%46%5%5%10%35%
2685
16th to endNight
39%47%5%35%5%6%7%41%
2703
February1st to 15thNight
49%48%7%25%46%8%37%
2349
16th to endNight
211%5%9%7%45%6%5%6%33%
1974
March1st to 15thNight
17%47%6%45%46%10%41%
2095
16th to endNight
7%9%45%6%36%5%6%10%34%
2112
April1st to 15thNight
9%10%34325%47%7%39%
1713
16th to endNight
10%11%3443445%6%42%
1620
May1st to 15thNight
8%6%25%5%245%5%8%44%
1517
16th to endNight
21%5%243245%5%8%35%
1309
June1st to 15thNight
14%42442346%8%45%
1260
16th to endNight
9%5%133345%5%7%49%
1260
July1st to 15thNight
5%21221236%8%62%
1260
16th to endNight
422213446%66%
1404
August1st to 15thNight
7%21321235%9%59%
1536
16th to endNight
6%312312446%62%
1719
September1st to 15thNight
12%413212335%58%
1830
16th to endNight
10%5%1232345%6%53%
1903
October1st to 15thNight
12%6%244245%5%9%43%
1922
16th to endNight
6%6%344345%5%8%46%
2279
November1st to 15thNight
47%346%25%46%7%47%
2377
16th to endNight
310%47%5%25%46%8%40%
2610
December1st to 15thNight
39%6%7%6%35%6%5%9%36%
2700
16th to endNight
211%5%8%7%35%5%6%7%35%
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
43%8%16%25%31
1253
16th to endDay
44%7%15%21%7%2
1531
February1st to 15thDay
43%7%20%19%6%1
1503
16th to endDay
46%6%18%21%5%1
1499
March1st to 15thDay
40%7%22%21%6%
1864
16th to endDay
48%8%16%20%5%
2112
April1st to 15thDay
47%8%16%18%9%
2234
16th to endDay
47%5%13%23%8%1
2340
May1st to 15thDay
41%5%14%25%12%
2433
16th to endDay
55%5%15%15%7%
2807
June1st to 15thDay
45%7%14%21%10%1
2700
16th to endDay
35%5%16%29%10%1
2700
July1st to 15thDay
27%6%13%28%19%4
2541
16th to endDay
21%5%13%30%24%5%
2591
August1st to 15thDay
26%6%16%29%16%3
2406
16th to endDay
26%410%32%21%5%
2483
September1st to 15thDay
33%210%26%19%7%
2126
16th to endDay
33%5%12%28%15%5%
1893
October1st to 15thDay
42%5%18%22%9%
1708
16th to endDay
40%6%18%23%8%1
1592
November1st to 15thDay
38%9%17%24%9%
1468
16th to endDay
41%6%20%19%9%2
1350
December1st to 15thDay
47%6%19%20%4
1260
16th to endDay
43%7%18%21%9%
1344
January1st to 15thNight
44%7%21%18%6%2
2685
16th to endNight
40%6%17%22%9%2
2703
February1st to 15thNight
44%7%17%20%9%1
2360
16th to endNight
49%5%15%21%8%
1974
March1st to 15thNight
37%8%25%23%5%
2095
16th to endNight
43%8%20%21%6%
2112
April1st to 15thNight
41%6%19%23%8%
1713
16th to endNight
42%416%27%7%1
1620
May1st to 15thNight
37%5%16%27%12%
1518
16th to endNight
45%6%18%19%9%
1309
June1st to 15thNight
37%5%17%27%10%1
1260
16th to endNight
33%417%27%15%1
1260
July1st to 15thNight
21%315%32%18%7%
1190
16th to endNight
18%5%12%29%24%10%
1314
August1st to 15thNight
22%5%16%33%17%4
1528
16th to endNight
23%39%31%26%6%
1719
September1st to 15thNight
29%311%28%19%7%
1830
16th to endNight
30%317%27%16%4
1903
October1st to 15thNight
37%5%18%26%9%1
1922
16th to endNight
34%6%18%27%12%
2279
November1st to 15thNight
35%6%22%22%12%1
2377
16th to endNight
40%6%23%17%9%2
2610
December1st to 15thNight
44%8%18%21%6%1
2700
16th to endNight
45%7%19%20%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
8%128%25%18%18%
60
16th to endDay
9%9%34%29%9%7%
64
February1st to 15thDay
5%23%34%26%7%2
78
16th to endDay
17%12%34%25%8%
158
March1st to 15thDay
9%29%43%15%2
270
16th to endDay
17%25%34%19%3
288
April1st to 15thDay
17%26%30%18%6%
269
16th to endDay
22%15%22%26%9%2
270
May1st to 15thDay
16%14%28%24%13%2
345
16th to endDay
25%6%16%28%18%4
517
June1st to 15thDay
15%14%24%25%16%3
495
16th to endDay
11%10%29%28%16%4
495
July1st to 15thDay
9%5%21%35%22%4
475
16th to endDay
8%6%28%35%16%5%
432
August1st to 15thDay
9%6%24%30%21%8%
315
16th to endDay
9%8%22%30%21%6%
332
September1st to 15thDay
20%11%27%20%16%2
315
16th to endDay
12%18%29%23%11%2
284
October1st to 15thDay
25%15%20%27%10%1
148
16th to endDay
6%8%30%28%18%8%
96
November1st to 15thDay
15%20%31%28%4
90
16th to endDay
12%12%32%29%5%9%
75
December1st to 15thDay
13%13%26%33%10%3
60
16th to endDay
14%12%28%23%15%6%
64
January1st to 15thNight
11%23%34%22%6%1
900
16th to endNight
10%19%33%27%6%1
783
February1st to 15thNight
11%16%32%25%11%2
704
16th to endNight
12%10%35%30%10%
632
March1st to 15thNight
7%15%40%28%6%
720
16th to endNight
12%15%33%29%8%
768
April1st to 15thNight
16%14%34%25%9%
624
16th to endNight
17%8%35%30%8%
540
May1st to 15thNight
12%11%28%30%15%
495
16th to endNight
25%421%32%16%
375
June1st to 15thNight
18%6%30%30%12%1
360
16th to endNight
14%6%29%34%15%
360
July1st to 15thNight
8%324%41%21%
340
16th to endNight
6%322%49%17%
376
August1st to 15thNight
8%117%44%25%1
456
16th to endNight
8%5%21%44%18%1
573
September1st to 15thNight
16%222%36%17%4
657
16th to endNight
14%7%26%34%15%1
688
October1st to 15thNight
16%10%27%29%15%1
660
16th to endNight
12%15%30%31%8%1
704
November1st to 15thNight
11%22%37%22%4
802
16th to endNight
11%17%41%22%6%1
900
December1st to 15thNight
9%17%33%28%8%1
900
16th to endNight
9%19%36%24%8%1
960
Page generated at 2017-09-24 07:15:46. Version ac04

Copyright 2017 A. Danko


Cardston Clear Sky Chart | Charts Home