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 2018-02-14.

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%
15686
6%
48734
5%
15661
41%
15661
14%
36629

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
39%
1015
10%
3444
6%
1015
42%
1015
13%
2596
January16th to endNight
34%
1088
7%
3409
5%
1088
35%
1088
10%
2696
February1st to 15thNight
42%
913
12%
2863
9%
912
46%
912
17%
2001
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
60%
360
0%
1161
0%
358
60%
358
25%
714
August16th to endNight
50%
433
2%
1521
2%
433
51%
433
15%
1087
September1st to 15thNight
47%
582
5%
1674
3%
582
49%
582
19%
1197
September16th to endNight
33%
716
6%
1980
3%
716
35%
716
14%
1537
October1st to 15thNight
35%
720
6%
2265
5%
720
36%
720
12%
1762
October16th to endNight
26%
894
2%
2688
1%
894
27%
894
6%
2358
November1st to 15thNight
28%
951
3%
2938
3%
951
29%
951
6%
2597
November16th to endNight
33%
1020
3%
3315
3%
1020
33%
1020
7%
2810
December1st to 15thNight
29%
1020
6%
3520
5%
1020
31%
1020
9%
2778
December16th to endNight
38%
1088
7%
3890
7%
1088
40%
1088
10%
3059

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%32%
49428
Night
9%11%5%9%8%45%5%6%7%26%
48827
TransparencyDay
48%8%15%20%5%
49024
Night
55%7%14%17%4
48736
SeeingDay
11%12%15%26%23%10%
7675
Night
12%15%16%28%20%6%
15698

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%9%8%46%6%6%10%21%
825
16th to endDay
6%12%6%11%10%5%9%5%6%5%21%
1164
February1st to 15thDay
28%5%10%10%49%7%9%9%22%
1311
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%41%
2793
16th to endDay
16%9%37%6%36%5%5%7%28%
2679
September1st to 15thDay
16%10%47%6%345%6%7%28%
2285
16th to endDay
17%12%47%6%35%5%5%6%25%
1980
October1st to 15thDay
13%17%5%8%7%45%45%6%20%
1693
16th to endDay
15%23%7%10%7%24436%13%
1524
November1st to 15thDay
13%14%9%12%9%5%5%46%5%12%
1246
16th to endDay
8%12%8%13%9%46%8%6%7%13%
975
December1st to 15thDay
7%13%7%13%7%47%7%6%8%15%
768
16th to endDay
6%11%6%9%9%6%8%8%6%9%16%
684
January1st to 15thNight
6%13%6%9%8%5%5%5%6%9%22%
3444
16th to endNight
7%13%7%12%9%5%6%5%6%5%19%
3409
February1st to 15thNight
37%5%7%9%47%7%8%10%29%
2853
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%43%
1167
16th to endNight
14%7%36%6%3446%8%33%
1521
September1st to 15thNight
11%8%35%5%35%5%6%8%35%
1674
16th to endNight
16%9%37%7%46%5%5%5%27%
1980
October1st to 15thNight
14%14%48%6%3445%6%26%
2265
16th to endNight
17%18%7%11%8%3443416%
2688
November1st to 15thNight
14%15%7%12%10%5%6%5%5%5%12%
2938
16th to endNight
8%13%7%14%10%5%6%6%6%8%11%
3315
December1st to 15thNight
8%15%7%12%9%45%6%5%8%16%
3520
16th to endNight
7%12%6%12%10%47%5%6%7%18%
3890

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%7%14%18%3
825
16th to endDay
60%6%10%15%7%
1164
February1st to 15thDay
51%7%16%19%5%
1311
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
41%10%18%22%6%
2774
16th to endDay
55%11%18%12%1
2679
September1st to 15thDay
54%11%19%13%
2285
16th to endDay
58%8%18%10%2
1980
October1st to 15thDay
63%9%17%9%
1693
16th to endDay
75%6%11%7%
1524
November1st to 15thDay
74%6%10%6%1
1246
16th to endDay
65%8%14%10%
975
December1st to 15thDay
63%8%10%14%2
768
16th to endDay
60%7%13%16%1
684
January1st to 15thNight
57%7%13%18%3
3444
16th to endNight
64%5%11%14%4
3409
February1st to 15thNight
46%8%16%19%8%
2865
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
33%10%23%24%6%1
1161
16th to endNight
48%11%18%20%1
1521
September1st to 15thNight
44%11%22%18%2
1674
16th to endNight
56%8%19%13%1
1980
October1st to 15thNight
57%9%18%12%
2265
16th to endNight
74%6%11%7%
2688
November1st to 15thNight
75%7%8%7%1
2938
16th to endNight
69%8%12%7%1
3315
December1st to 15thNight
64%6%12%14%1
3520
16th to endNight
63%6%12%15%2
3890

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
4426%37%23%3
90
16th to endDay
14%311%28%31%11%
96
February1st to 15thDay
2120%38%26%10%
86
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%21%29%21%
585
16th to endDay
20%7%13%25%21%12%
388
September1st to 15thDay
24%10%17%20%18%9%
315
16th to endDay
20%10%21%25%14%7%
315
October1st to 15thDay
23%5%18%28%18%6%
160
16th to endDay
29%218%18%22%7%
127
November1st to 15thDay
15%6%17%28%21%10%
90
16th to endDay
10%117%40%22%8%
90
December1st to 15thDay
18%6%17%34%14%9%
64
16th to endDay
1314%35%27%17%
62
January1st to 15thNight
10%16%19%29%18%6%
1020
16th to endNight
12%16%18%30%15%6%
1088
February1st to 15thNight
5%17%18%29%20%9%
917
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%31%11%
360
16th to endNight
16%9%12%28%27%5%
433
September1st to 15thNight
15%10%17%25%23%6%
582
16th to endNight
21%11%22%26%15%3
716
October1st to 15thNight
22%10%18%29%16%3
720
16th to endNight
25%10%16%22%19%5%
894
November1st to 15thNight
19%15%15%24%18%6%
951
16th to endNight
11%17%16%26%20%9%
1020
December1st to 15thNight
14%18%20%26%14%7%
1020
16th to endNight
9%15%12%27%25%9%
1088
Page generated at 2018-02-15 08:58:51. Version ac04

Copyright 2018 A. Danko


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