Fort Saint John
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Saint John clear sky chart from 2005-11-05 to

2017-09-12
.

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
41%
14953
9%
46652
6%
14926
44%
14926
16%
33953

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
35%
926
7%
2865
4%
925
37%
925
11%
2261
January16th to endNight
31%
839
12%
2919
10%
839
35%
839
12%
2165
February1st to 15thNight
39%
703
8%
2489
9%
701
42%
701
13%
1848
February16th to endNight
46%
632
9%
2053
9%
632
48%
632
15%
1521
March1st to 15thNight
35%
720
10%
2148
8%
720
38%
720
15%
1622
March16th to endNight
49%
767
13%
2013
7%
767
52%
767
23%
1458
April1st to 15thNight
41%
682
12%
1762
5%
682
46%
682
21%
1316
April16th to endNight
40%
360
9%
1440
12%
360
44%
360
14%
989
May1st to 15thNight
42%
359
1%
1357
1%
359
43%
359
16%
914
May16th to endNight
44%
374
0%
1122
0%
374
44%
374
19%
808
June1st to 15thNight
51%
360
0%
1080
0%
360
51%
360
20%
762
June16th to endNight
53%
360
0%
1080
0%
360
53%
360
22%
742
July1st to 15thNight
53%
340
0%
1020
0%
340
53%
340
24%
688
July16th to endNight
60%
376
0%
1125
0%
354
61%
354
25%
721
August1st to 15thNight
63%
360
4%
1379
5%
358
64%
358
21%
851
August16th to endNight
50%
462
12%
1608
11%
462
56%
462
22%
1006
September1st to 15thNight
57%
706
12%
1765
7%
706
58%
706
32%
1167
September16th to endNight
40%
656
14%
1798
6%
656
44%
656
20%
1290
October1st to 15thNight
37%
660
10%
1987
5%
660
42%
660
17%
1431
October16th to endNight
31%
704
11%
2365
6%
704
38%
704
14%
1722
November1st to 15thNight
34%
767
15%
2517
11%
767
42%
767
16%
1768
November16th to endNight
36%
918
8%
2808
5%
918
39%
918
13%
2175
December1st to 15thNight
35%
930
9%
2880
7%
930
36%
930
11%
2303
December16th to endNight
37%
992
10%
3072
5%
992
41%
992
12%
2425

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
11%9%36%6%45%5%6%7%32%
48073
Night
9%10%48%7%45%5%6%7%30%
46781
TransparencyDay
48%9%17%18%5%
47705
Night
50%8%15%18%5%
46654
SeeingDay
14%9%25%27%18%4
7027
Night
14%7%23%33%18%2
14966

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
9%12%5%11%8%6%6%5%46%22%
1074
16th to endDay
8%14%5%7%7%36%5%5%8%26%
1317
February1st to 15thDay
6%11%410%9%5%6%5%6%7%25%
1373
16th to endDay
6%13%6%10%9%445%5%7%25%
1421
March1st to 15thDay
8%16%7%8%7%335%5%6%27%
1812
16th to endDay
10%16%5%7%6%35%45%7%27%
2209
April1st to 15thDay
8%11%47%7%36%5%5%7%32%
2184
16th to endDay
11%10%37%7%47%6%5%7%28%
2520
May1st to 15thDay
10%7%346%36%5%6%8%38%
2592
16th to endDay
16%6%35%6%46%6%7%7%28%
2991
June1st to 15thDay
13%426%5%46%5%7%9%32%
2880
16th to endDay
12%6%35%6%45%5%6%7%37%
2880
July1st to 15thDay
11%5%25%5%35%6%6%9%37%
2880
16th to endDay
10%425%5%35%6%8%8%40%
2965
August1st to 15thDay
9%5%245%45%6%6%8%41%
2574
16th to endDay
10%425%6%45%5%6%9%38%
2593
September1st to 15thDay
11%425%43445%8%44%
2114
16th to endDay
11%5%45%6%35%47%7%38%
1832
October1st to 15thDay
13%11%5%8%6%25%5%46%29%
1643
16th to endDay
15%13%46%6%3446%7%28%
1507
November1st to 15thDay
14%12%47%5%3445%6%31%
1328
16th to endDay
10%13%5%10%9%5%6%5%5%6%21%
1152
December1st to 15thDay
11%15%5%10%8%45%7%48%19%
1080
16th to endDay
8%12%411%10%6%6%6%5%7%19%
1152
January1st to 15thNight
7%11%6%10%9%5%6%5%6%7%22%
2865
16th to endNight
10%15%47%6%45%46%7%26%
2919
February1st to 15thNight
8%11%5%9%10%45%5%6%9%24%
2477
16th to endNight
6%10%5%9%9%46%6%7%7%25%
2053
March1st to 15thNight
8%12%5%10%7%36%46%7%27%
2148
16th to endNight
9%12%46%6%35%5%6%6%34%
2010
April1st to 15thNight
7%9%39%8%46%46%6%33%
1762
16th to endNight
12%9%48%5%35%6%6%6%32%
1440
May1st to 15thNight
10%7%36%6%45%6%7%7%34%
1357
16th to endNight
15%6%38%5%35%5%6%8%30%
1122
June1st to 15thNight
11%6%46%6%36%6%6%8%34%
1080
16th to endNight
14%7%25%5%26%5%5%8%34%
1080
July1st to 15thNight
8%5%36%5%45%5%6%9%37%
1080
16th to endNight
8%325%5%35%5%7%11%39%
1202
August1st to 15thNight
7%3146%46%6%8%9%41%
1386
16th to endNight
9%425%6%35%6%7%9%40%
1608
September1st to 15thNight
9%5%14425%5%6%8%44%
1765
16th to endNight
11%6%35%5%35%5%6%8%37%
1798
October1st to 15thNight
12%10%36%5%345%6%8%31%
1987
16th to endNight
13%13%5%6%5%345%6%6%30%
2365
November1st to 15thNight
11%11%46%5%35%5%5%7%33%
2517
16th to endNight
8%13%6%11%8%46%45%6%25%
2808
December1st to 15thNight
10%16%6%10%7%45%45%6%21%
2880
16th to endNight
7%13%5%10%9%5%7%6%6%7%20%
3072

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
62%8%15%11%2
1074
16th to endDay
54%9%14%14%5%1
1317
February1st to 15thDay
55%10%15%12%6%
1373
16th to endDay
56%8%16%14%3
1421
March1st to 15thDay
55%7%14%16%6%
1812
16th to endDay
57%6%17%14%3
2209
April1st to 15thDay
49%8%15%17%8%
2184
16th to endDay
53%8%15%17%5%
2520
May1st to 15thDay
42%8%15%21%10%
2592
16th to endDay
50%9%14%18%6%
2996
June1st to 15thDay
46%11%16%19%5%
2880
16th to endDay
44%9%15%22%7%
2880
July1st to 15thDay
41%9%17%22%8%
2711
16th to endDay
37%12%24%22%3
2779
August1st to 15thDay
38%10%23%23%3
2556
16th to endDay
40%10%22%22%3
2593
September1st to 15thDay
36%9%24%23%5%
2114
16th to endDay
43%9%18%20%6%
1832
October1st to 15thDay
54%7%15%20%1
1643
16th to endDay
54%8%19%14%3
1507
November1st to 15thDay
53%8%13%20%4
1328
16th to endDay
61%6%14%11%4
1152
December1st to 15thDay
62%7%15%11%3
1080
16th to endDay
62%6%13%13%4
1152
January1st to 15thNight
58%10%15%12%3
2865
16th to endNight
55%7%13%16%41
2919
February1st to 15thNight
55%7%16%15%4
2489
16th to endNight
53%8%16%17%3
2053
March1st to 15thNight
54%8%14%17%41
2148
16th to endNight
48%6%16%20%7%
2014
April1st to 15thNight
50%7%11%19%10%
1762
16th to endNight
49%8%12%19%8%1
1440
May1st to 15thNight
46%8%12%21%10%
1358
16th to endNight
49%7%12%20%8%1
1122
June1st to 15thNight
45%10%13%21%8%
1080
16th to endNight
44%8%16%20%8%
1080
July1st to 15thNight
40%10%16%22%10%
1020
16th to endNight
34%12%25%22%4
1125
August1st to 15thNight
36%12%17%27%5%
1379
16th to endNight
37%10%22%23%5%
1608
September1st to 15thNight
35%8%22%25%7%
1765
16th to endNight
43%12%15%21%7%
1798
October1st to 15thNight
48%9%18%19%3
1987
16th to endNight
52%8%16%20%2
2365
November1st to 15thNight
49%8%15%22%4
2517
16th to endNight
59%7%12%16%31
2808
December1st to 15thNight
62%7%12%14%3
2880
16th to endNight
58%9%12%15%3
3072

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
11%316%36%16%15%
60
16th to endDay
12%9%23%35%10%7%
64
February1st to 15thDay
7%6%28%38%14%4
63
16th to endDay
15%424%31%18%5%
211
March1st to 15thDay
20%9%33%21%13%1
270
16th to endDay
19%8%28%29%15%
288
April1st to 15thDay
15%14%34%23%9%1
269
16th to endDay
19%14%32%19%11%2
270
May1st to 15thDay
15%13%33%21%13%3
369
16th to endDay
16%7%23%28%19%4
705
June1st to 15thDay
14%7%26%27%20%3
675
16th to endDay
13%6%22%27%24%6%
675
July1st to 15thDay
10%7%26%30%19%5%
645
16th to endDay
9%6%24%31%22%5%
633
August1st to 15thDay
11%6%18%29%26%7%
369
16th to endDay
15%14%32%25%10%1
332
September1st to 15thDay
17%9%21%29%16%5%
300
16th to endDay
11%21%30%23%9%3
255
October1st to 15thDay
23%14%25%23%10%2
248
16th to endDay
26%48%35%19%4
82
November1st to 15thDay
20%11%35%26%5%1
60
16th to endDay
18%11%11%26%25%6%
60
December1st to 15thDay
13%311%30%35%6%
60
16th to endDay
10%9%15%29%26%7%
64
January1st to 15thNight
12%8%23%35%16%3
930
16th to endNight
17%11%27%31%11%1
839
February1st to 15thNight
13%8%24%31%18%3
709
16th to endNight
9%322%36%24%3
632
March1st to 15thNight
11%8%27%35%13%3
720
16th to endNight
14%418%37%23%2
768
April1st to 15thNight
12%6%25%35%18%1
682
16th to endNight
16%7%26%28%20%1
360
May1st to 15thNight
13%7%26%30%18%3
360
16th to endNight
17%421%30%24%1
375
June1st to 15thNight
12%5%20%30%26%3
360
16th to endNight
17%216%32%26%4
360
July1st to 15thNight
10%423%34%23%3
340
16th to endNight
8%5%16%40%25%3
376
August1st to 15thNight
8%14%28%42%6%
360
16th to endNight
12%225%33%22%3
462
September1st to 15thNight
12%417%36%25%2
706
16th to endNight
14%10%26%29%17%1
656
October1st to 15thNight
17%9%26%32%13%
660
16th to endNight
20%9%28%28%12%1
704
November1st to 15thNight
14%9%29%33%11%2
767
16th to endNight
14%8%24%36%14%1
918
December1st to 15thNight
17%8%22%36%13%2
930
16th to endNight
13%7%22%34%20%2
992
Page generated at 2017-09-13 04:39:10. Version ac04

Copyright 2017 A. Danko


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