Fort Nelson
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Nelson clear sky chart from 2005-11-05 to 2017-12-02.

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
43%
15312
8%
47593
6%
15287
45%
15287
15%
35784

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
5%
2999
4%
925
39%
925
8%
2490
January16th to endNight
43%
883
14%
2963
14%
883
45%
883
14%
2232
February1st to 15thNight
39%
720
10%
2588
9%
719
43%
719
13%
1936
February16th to endNight
47%
632
9%
2053
9%
632
48%
632
15%
1518
March1st to 15thNight
35%
720
10%
2168
8%
720
37%
720
14%
1695
March16th to endNight
46%
768
13%
2041
8%
768
48%
768
22%
1497
April1st to 15thNight
42%
614
10%
1694
7%
614
46%
614
18%
1273
April16th to endNight
45%
362
7%
1442
8%
362
47%
362
14%
976
May1st to 15thNight
42%
359
0%
1210
0%
359
42%
359
18%
830
May16th to endNight
50%
374
0%
1122
0%
374
50%
374
19%
799
June1st to 15thNight
52%
360
0%
911
0%
360
52%
360
21%
676
June16th to endNight
53%
360
0%
900
0%
360
53%
360
23%
665
July1st to 15thNight
57%
340
0%
850
0%
340
57%
340
24%
622
July16th to endNight
58%
376
0%
1076
0%
354
59%
354
18%
776
August1st to 15thNight
61%
360
0%
1281
0%
358
61%
358
21%
835
August16th to endNight
49%
451
6%
1597
6%
451
52%
451
15%
1136
September1st to 15thNight
51%
678
9%
1758
5%
678
53%
678
25%
1256
September16th to endNight
41%
716
10%
1971
6%
716
42%
716
17%
1509
October1st to 15thNight
39%
720
11%
2160
6%
720
45%
720
19%
1551
October16th to endNight
39%
768
10%
2655
7%
768
45%
768
14%
1932
November1st to 15thNight
36%
872
12%
2810
9%
872
41%
872
13%
2157
November16th to endNight
41%
1020
8%
3120
7%
1020
42%
1020
13%
2439
December1st to 15thNight
38%
942
7%
2960
6%
942
38%
942
10%
2402
December16th to endNight
39%
992
9%
3264
7%
992
42%
992
10%
2582

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
12%9%47%6%35%5%6%7%29%
48930
Night
10%12%5%9%7%45%5%5%7%26%
47706
TransparencyDay
50%8%16%19%5%
48548
Night
55%7%13%17%5%
47593
SeeingDay
15%5%21%29%22%6%
7532
Night
15%418%34%22%3
15324

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
10%16%6%13%10%5%7%45%6%14%
940
16th to endDay
8%14%5%8%7%46%5%6%7%24%
1272
February1st to 15thDay
8%9%6%11%9%47%6%5%8%23%
1275
16th to endDay
6%12%6%12%9%5%5%35%7%24%
1421
March1st to 15thDay
8%16%8%11%8%44445%22%
1791
16th to endDay
8%14%6%9%6%36%45%7%27%
2183
April1st to 15thDay
8%10%5%6%6%35%5%8%8%31%
2250
16th to endDay
11%11%46%6%36%46%8%28%
2518
May1st to 15thDay
11%6%36%5%35%45%7%39%
2739
16th to endDay
16%6%25%5%35%5%5%7%35%
2991
June1st to 15thDay
15%6%36%5%46%5%7%7%30%
3048
16th to endDay
15%6%36%5%35%6%6%9%31%
3060
July1st to 15thDay
16%7%35%6%35%5%6%7%32%
3060
16th to endDay
12%6%36%8%46%7%7%9%28%
3020
August1st to 15thDay
11%5%26%4345%6%9%39%
2671
16th to endDay
15%5%26%6%445%5%7%34%
2605
September1st to 15thDay
13%6%246%45%5%5%7%39%
2202
16th to endDay
16%8%36%6%35%5%6%6%29%
1986
October1st to 15thDay
14%11%36%43445%7%33%
1800
16th to endDay
14%13%5%8%7%2446%7%24%
1568
November1st to 15thDay
12%16%7%9%7%435%4422%
1365
16th to endDay
7%14%7%13%10%45%45%5%20%
1170
December1st to 15thDay
13%15%6%8%8%37%5%5%8%15%
1035
16th to endDay
5%15%9%11%9%5%7%5%7%6%15%
960
January1st to 15thNight
9%16%6%12%9%6%6%5%6%6%15%
2999
16th to endNight
8%13%6%9%8%36%6%6%6%25%
2963
February1st to 15thNight
9%12%5%11%8%45%5%5%6%24%
2576
16th to endNight
7%12%6%10%7%45%5%6%6%27%
2053
March1st to 15thNight
7%15%6%10%10%46%5%45%22%
2168
16th to endNight
7%14%5%7%7%3446%8%30%
2037
April1st to 15thNight
7%13%5%8%6%36%45%6%30%
1694
16th to endNight
10%11%45%5%36%7%7%6%30%
1442
May1st to 15thNight
11%9%446%45%5%6%8%33%
1209
16th to endNight
16%8%36%435%5%5%7%32%
1122
June1st to 15thNight
14%5%26%7%47%6%7%6%31%
911
16th to endNight
13%6%26%7%35%6%6%8%32%
900
July1st to 15thNight
17%5%15%6%35%5%6%8%34%
900
16th to endNight
10%6%26%7%5%9%7%8%11%24%
1149
August1st to 15thNight
10%6%35%5%45%7%6%9%37%
1288
16th to endNight
14%6%37%8%46%6%6%9%27%
1597
September1st to 15thNight
11%6%26%6%35%6%7%8%34%
1758
16th to endNight
19%8%27%6%45%5%5%7%25%
1971
October1st to 15thNight
13%11%47%6%3345%8%30%
2160
16th to endNight
13%13%48%6%34446%29%
2655
November1st to 15thNight
11%17%7%9%6%3433426%
2810
16th to endNight
7%13%6%12%9%35%45%6%22%
3120
December1st to 15thNight
10%15%7%10%9%5%445%6%19%
2960
16th to endNight
7%15%7%12%9%45%5%6%8%16%
3264

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
69%6%10%10%2
940
16th to endDay
56%6%13%17%5%1
1272
February1st to 15thDay
57%7%12%19%3
1275
16th to endDay
58%6%15%16%3
1421
March1st to 15thDay
61%5%12%13%6%
1791
16th to endDay
54%6%14%19%4
2183
April1st to 15thDay
46%9%15%21%6%
2250
16th to endDay
49%6%13%20%9%
2518
May1st to 15thDay
41%6%14%26%9%
2739
16th to endDay
45%7%10%25%9%1
2996
June1st to 15thDay
48%9%14%20%6%
3048
16th to endDay
45%9%16%23%3
3060
July1st to 15thDay
48%8%17%21%3
2881
16th to endDay
46%12%23%16%
2830
August1st to 15thDay
39%10%25%20%3
2653
16th to endDay
46%8%23%19%1
2605
September1st to 15thDay
42%9%22%20%5%
2202
16th to endDay
50%9%17%17%4
1986
October1st to 15thDay
49%7%14%25%3
1800
16th to endDay
56%7%14%17%2
1568
November1st to 15thDay
63%6%8%16%4
1365
16th to endDay
64%5%10%14%31
1170
December1st to 15thDay
65%6%14%10%3
1035
16th to endDay
63%7%8%14%6%
960
January1st to 15thNight
67%7%10%10%3
2999
16th to endNight
57%6%11%17%5%1
2963
February1st to 15thNight
58%6%10%18%5%
2588
16th to endNight
55%6%15%16%5%
2053
March1st to 15thNight
61%5%11%14%6%
2168
16th to endNight
50%6%14%20%7%
2041
April1st to 15thNight
53%7%11%18%8%
1694
16th to endNight
49%7%9%18%12%1
1442
May1st to 15thNight
46%8%11%20%11%1
1210
16th to endNight
49%7%9%21%9%2
1122
June1st to 15thNight
48%9%12%22%7%
911
16th to endNight
45%11%16%19%7%
900
July1st to 15thNight
44%10%16%22%6%
850
16th to endNight
45%13%22%16%2
1076
August1st to 15thNight
41%9%20%23%4
1281
16th to endNight
49%10%17%20%2
1597
September1st to 15thNight
41%11%17%23%5%
1758
16th to endNight
54%8%13%17%5%
1971
October1st to 15thNight
50%6%15%20%6%
2160
16th to endNight
54%6%14%19%4
2655
November1st to 15thNight
61%47%20%5%
2810
16th to endNight
60%6%10%15%5%
3120
December1st to 15thNight
65%6%13%12%2
2960
16th to endNight
63%6%10%14%5%
3264

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%113%30%31%10%
60
16th to endDay
6%315%31%35%7%
64
February1st to 15thDay
8%125%40%18%6%
60
16th to endDay
11%420%32%27%3
211
March1st to 15thDay
16%5%26%30%15%4
262
16th to endDay
18%6%22%23%22%6%
288
April1st to 15thDay
13%6%28%32%16%2
269
16th to endDay
17%12%26%27%14%2
270
May1st to 15thDay
14%7%23%30%19%4
516
16th to endDay
16%5%17%31%24%4
705
June1st to 15thDay
16%6%21%30%21%3
675
16th to endDay
13%319%26%25%11%
675
July1st to 15thDay
19%318%27%23%7%
645
16th to endDay
12%319%32%26%5%
679
August1st to 15thDay
10%416%27%30%10%
465
16th to endDay
18%6%31%27%14%2
332
September1st to 15thDay
13%6%25%27%17%9%
315
16th to endDay
17%6%26%25%19%4
315
October1st to 15thDay
21%6%28%28%12%3
315
16th to endDay
20%6%20%18%25%8%
105
November1st to 15thDay
14%318%40%20%3
90
16th to endDay
11%212%37%24%12%
90
December1st to 15thDay
20%19%38%22%6%
62
16th to endDay
7%110%29%40%9%
64
January1st to 15thNight
15%418%37%20%4
930
16th to endNight
15%419%42%17%2
883
February1st to 15thNight
12%6%22%33%21%2
725
16th to endNight
10%5%16%39%25%2
632
March1st to 15thNight
14%7%22%34%17%3
720
16th to endNight
13%220%31%25%5%
768
April1st to 15thNight
12%7%24%29%22%3
614
16th to endNight
16%425%31%19%2
362
May1st to 15thNight
13%8%25%28%20%3
360
16th to endNight
18%5%14%31%27%1
375
June1st to 15thNight
16%318%36%24%1
360
16th to endNight
13%215%26%33%7%
360
July1st to 15thNight
17%214%32%27%4
340
16th to endNight
11%213%35%30%7%
376
August1st to 15thNight
11%213%27%39%5%
360
16th to endNight
17%117%30%28%4
451
September1st to 15thNight
14%319%32%23%6%
678
16th to endNight
22%419%31%20%3
716
October1st to 15thNight
21%323%33%15%1
720
16th to endNight
21%5%18%32%18%3
768
November1st to 15thNight
19%5%19%30%21%3
872
16th to endNight
13%416%42%20%3
1020
December1st to 15thNight
16%5%17%38%17%3
942
16th to endNight
14%315%36%23%6%
992
Page generated at 2017-12-03 08:16:45. Version ac04

Copyright 2017 A. Danko


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