Yellowknife
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Yellowknife 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
39%
14789
6%
46063
5%
14764
41%
14764
14%
34574

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
38%
925
9%
3178
6%
925
42%
925
12%
2407
January16th to endNight
32%
992
7%
3147
6%
992
34%
992
10%
2469
February1st to 15thNight
41%
841
12%
2651
10%
840
45%
840
16%
1864
February16th to endNight
35%
632
11%
2162
11%
632
39%
632
11%
1646
March1st to 15thNight
48%
720
17%
2189
13%
720
51%
720
22%
1486
March16th to endNight
50%
767
13%
2037
8%
767
52%
767
26%
1383
April1st to 15thNight
46%
556
11%
1636
8%
556
50%
556
22%
1088
April16th to endNight
52%
369
2%
1326
0%
369
53%
369
28%
714
May1st to 15thNight
44%
359
0%
1099
0%
359
44%
359
23%
696
May16th to endNight
47%
374
0%
926
0%
374
47%
374
29%
625
June1st to 15thNight
50%
240
0%
600
0%
240
50%
240
30%
376
June16th to endNight
53%
180
0%
540
0%
180
53%
180
23%
334
July1st to 15thNight
55%
313
0%
653
0%
313
55%
313
31%
474
July16th to endNight
53%
376
0%
898
0%
354
56%
354
28%
615
August1st to 15thNight
59%
352
0%
1133
0%
350
60%
350
24%
705
August16th to endNight
49%
397
2%
1394
2%
397
50%
397
15%
1002
September1st to 15thNight
46%
533
5%
1534
3%
533
48%
533
18%
1109
September16th to endNight
30%
656
5%
1815
2%
656
32%
656
13%
1434
October1st to 15thNight
33%
660
7%
2076
6%
660
35%
660
11%
1624
October16th to endNight
26%
819
2%
2463
1%
819
27%
819
6%
2145
November1st to 15thNight
27%
876
3%
2706
3%
876
28%
876
5%
2414
November16th to endNight
32%
930
3%
3060
3%
930
32%
930
7%
2586
December1st to 15thNight
30%
930
6%
3249
5%
930
32%
930
9%
2526
December16th to endNight
37%
992
6%
3591
6%
992
38%
992
9%
2852

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%9%47%7%35%5%6%7%33%
47998
Night
9%11%5%9%8%45%5%6%7%26%
46156
TransparencyDay
48%8%15%21%6%
47594
Night
55%7%14%17%4
46065
SeeingDay
11%13%15%26%23%10%
7188
Night
12%16%16%28%20%6%
14801

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%11%7%10%7%46%6%7%10%19%
761
16th to endDay
6%12%7%11%9%5%8%45%5%23%
1074
February1st to 15thDay
28%5%10%10%48%6%9%9%23%
1222
16th to endDay
410%7%12%11%5%7%5%6%7%22%
1312
March1st to 15thDay
6%9%37%6%5%6%6%7%10%31%
1770
16th to endDay
5%11%5%8%7%46%6%7%7%29%
2185
April1st to 15thDay
7%9%5%6%6%35%5%5%7%38%
2311
16th to endDay
25%36%7%46%5%6%8%43%
2634
May1st to 15thDay
6%7%36%6%35%46%7%43%
2850
16th to endDay
12%6%35%423447%45%
3186
June1st to 15thDay
9%6%26%6%35%5%6%7%40%
3360
16th to endDay
9%5%35%5%35%5%5%8%41%
3420
July1st to 15thDay
9%6%36%7%47%6%6%8%33%
3264
16th to endDay
7%426%6%36%6%7%9%39%
3209
August1st to 15thDay
10%6%35%5%35%5%5%7%40%
2736
16th to endDay
16%9%37%7%37%5%5%7%27%
2454
September1st to 15thDay
16%10%47%6%345%6%6%27%
2095
16th to endDay
18%13%47%6%35%5%5%6%24%
1815
October1st to 15thDay
14%17%5%7%7%45%45%6%20%
1552
16th to endDay
15%23%7%10%6%24446%14%
1398
November1st to 15thDay
14%14%9%12%9%5%5%46%5%12%
1149
16th to endDay
8%11%7%13%10%46%7%7%7%14%
900
December1st to 15thDay
8%13%7%12%7%36%7%6%9%16%
710
16th to endDay
7%12%7%9%9%6%7%6%6%9%15%
631
January1st to 15thNight
7%13%7%9%8%5%5%5%7%9%21%
3178
16th to endNight
7%13%7%12%9%5%6%5%5%5%20%
3147
February1st to 15thNight
37%5%7%10%47%7%8%9%28%
2641
16th to endNight
6%12%7%11%9%5%6%5%5%7%22%
2162
March1st to 15thNight
37%5%8%8%45%5%6%6%37%
2189
16th to endNight
46%5%7%5%45%7%6%8%37%
2034
April1st to 15thNight
6%8%47%6%36%6%5%5%39%
1636
16th to endNight
34246%3347%8%51%
1326
May1st to 15thNight
5%6%37%5%35%6%6%7%40%
1098
16th to endNight
11%6%44334445%46%
926
June1st to 15thNight
11%4143345%7%9%44%
600
16th to endNight
6%5%25%5%445%5%12%43%
540
July1st to 15thNight
8%427%7%5%5%5%7%10%36%
693
16th to endNight
6%5%25%8%35%5%6%9%40%
959
August1st to 15thNight
8%5%245%235%7%10%41%
1139
16th to endNight
15%7%36%5%3446%8%32%
1394
September1st to 15thNight
11%8%26%6%35%5%6%8%34%
1534
16th to endNight
17%10%37%7%46%5%5%5%25%
1815
October1st to 15thNight
14%14%48%6%3445%6%26%
2076
16th to endNight
17%18%7%10%8%3443416%
2463
November1st to 15thNight
15%15%7%12%10%5%6%5%45%11%
2706
16th to endNight
9%12%7%14%10%5%6%6%6%8%11%
3060
December1st to 15thNight
8%14%7%11%9%45%6%5%9%17%
3249
16th to endNight
8%13%7%12%10%47%5%6%7%17%
3591

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
56%8%14%17%3
761
16th to endDay
60%49%16%8%
1074
February1st to 15thDay
50%7%16%19%5%
1222
16th to endDay
57%5%12%15%6%1
1312
March1st to 15thDay
46%5%13%24%8%1
1770
16th to endDay
49%7%14%21%6%
2186
April1st to 15thDay
43%6%14%26%8%
2311
16th to endDay
36%9%15%32%5%
2634
May1st to 15thDay
38%8%14%27%10%
2850
16th to endDay
38%6%9%29%15%1
3191
June1st to 15thDay
41%7%13%27%9%
3360
16th to endDay
39%10%15%23%9%1
3420
July1st to 15thDay
44%11%16%21%5%
3075
16th to endDay
36%12%23%25%2
3007
August1st to 15thDay
42%10%18%22%5%
2717
16th to endDay
56%12%19%11%
2454
September1st to 15thDay
55%11%18%13%
2095
16th to endDay
60%8%17%10%2
1815
October1st to 15thDay
63%9%17%8%
1552
16th to endDay
73%6%12%7%
1398
November1st to 15thDay
75%6%10%6%1
1149
16th to endDay
65%8%15%10%
900
December1st to 15thDay
61%9%10%15%2
710
16th to endDay
62%7%13%15%1
631
January1st to 15thNight
57%7%13%18%3
3178
16th to endNight
63%411%14%5%
3147
February1st to 15thNight
48%7%16%18%8%
2653
16th to endNight
60%5%11%14%6%
2162
March1st to 15thNight
45%6%13%26%7%1
2189
16th to endNight
41%6%16%24%10%
2037
April1st to 15thNight
43%6%13%26%10%1
1636
16th to endNight
29%6%14%38%10%
1326
May1st to 15thNight
39%6%16%28%9%
1099
16th to endNight
39%5%9%28%16%
926
June1st to 15thNight
33%6%16%32%11%
600
16th to endNight
32%10%16%29%9%
540
July1st to 15thNight
37%9%14%32%5%
653
16th to endNight
37%10%21%27%2
898
August1st to 15thNight
34%10%24%23%6%
1133
16th to endNight
48%11%18%19%1
1394
September1st to 15thNight
45%12%21%18%2
1534
16th to endNight
58%8%18%11%2
1815
October1st to 15thNight
58%9%18%12%1
2076
16th to endNight
73%7%11%7%
2463
November1st to 15thNight
76%7%7%6%1
2706
16th to endNight
69%8%12%8%1
3060
December1st to 15thNight
62%6%13%15%1
3249
16th to endNight
65%6%12%13%1
3591

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
1326%45%21%1
60
16th to endDay
20%49%28%31%6%
64
February1st to 15thDay
3118%33%28%15%
60
16th to endDay
14%36%33%29%12%
62
March1st to 15thDay
9%12%14%30%21%12%
231
16th to endDay
9%13%16%28%21%10%
288
April1st to 15thDay
8%13%20%27%23%5%
269
16th to endDay
6%16%14%31%25%5%
393
May1st to 15thDay
9%17%20%24%23%4
561
16th to endDay
9%16%13%29%24%6%
705
June1st to 15thDay
9%15%17%27%21%9%
675
16th to endDay
10%15%12%25%24%13%
675
July1st to 15thDay
10%11%14%23%29%10%
645
16th to endDay
9%14%11%24%25%14%
703
August1st to 15thDay
8%10%9%20%28%22%
566
16th to endDay
19%9%11%24%22%12%
319
September1st to 15thDay
24%11%16%20%17%10%
255
16th to endDay
23%12%23%25%10%4
255
October1st to 15thDay
27%5%15%29%17%5%
113
16th to endDay
31%218%16%21%9%
85
November1st to 15thDay
18%8%25%23%15%10%
60
16th to endDay
13%115%36%20%13%
60
December1st to 15thDay
25%223%30%11%6%
43
16th to endDay
2417%34%21%19%
41
January1st to 15thNight
10%18%17%29%17%6%
930
16th to endNight
12%18%18%30%14%5%
992
February1st to 15thNight
5%18%17%28%20%10%
845
16th to endNight
8%16%17%32%20%5%
632
March1st to 15thNight
418%14%33%18%10%
720
16th to endNight
6%17%12%30%25%6%
768
April1st to 15thNight
7%19%15%32%19%5%
556
16th to endNight
418%16%35%21%3
369
May1st to 15thNight
6%21%20%32%18%1
360
16th to endNight
9%18%17%33%20%1
375
June1st to 15thNight
11%17%14%27%27%1
240
16th to endNight
10%17%11%31%28%1
180
July1st to 15thNight
7%11%13%31%30%4
313
16th to endNight
7%17%11%23%33%6%
376
August1st to 15thNight
12%10%8%26%30%11%
352
16th to endNight
17%10%12%25%27%5%
397
September1st to 15thNight
15%11%17%25%22%7%
533
16th to endNight
22%12%22%25%14%2
656
October1st to 15thNight
23%11%18%28%15%3
660
16th to endNight
26%11%15%21%19%5%
819
November1st to 15thNight
20%16%14%22%17%7%
876
16th to endNight
11%18%16%25%18%9%
930
December1st to 15thNight
13%19%19%25%14%7%
930
16th to endNight
9%16%12%27%23%9%
992
Page generated at 2017-08-13 12:16:42. Version ac04

Copyright 2017 A. Danko


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