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 2018-03-21.

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%
15858
9%
49301
6%
15831
45%
15831
16%
35885

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
36%
1016
7%
3105
5%
1015
38%
1015
12%
2446
January16th to endNight
31%
922
11%
3162
9%
922
35%
922
11%
2382
February1st to 15thNight
39%
765
9%
2700
10%
763
42%
763
14%
1998
February16th to endNight
45%
684
9%
2222
9%
684
48%
684
15%
1642
March1st to 15thNight
37%
780
11%
2327
9%
780
39%
780
16%
1743
March16th to endNight
50%
791
13%
2079
7%
791
52%
791
22%
1514
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%
720
12%
1800
7%
720
58%
720
32%
1192
September16th to endNight
41%
716
15%
1962
7%
716
45%
716
21%
1390
October1st to 15thNight
38%
720
10%
2168
5%
720
43%
720
18%
1551
October16th to endNight
31%
768
12%
2580
7%
768
39%
768
14%
1855
November1st to 15thNight
35%
833
14%
2733
10%
833
41%
833
15%
1955
November16th to endNight
35%
1002
8%
3042
5%
1002
38%
1002
12%
2362
December1st to 15thNight
37%
1020
9%
3120
7%
1020
38%
1020
12%
2447
December16th to endNight
38%
1088
11%
3328
5%
1088
43%
1088
12%
2611

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%
49613
Night
9%10%48%7%45%5%6%7%30%
49430
TransparencyDay
48%9%17%18%5%
49245
Night
50%8%15%18%5%
49303
SeeingDay
14%9%25%27%18%4
7538
Night
14%7%23%34%18%2
15871

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%13%5%11%8%6%6%5%46%22%
1164
16th to endDay
9%14%5%7%7%37%5%6%8%25%
1427
February1st to 15thDay
6%11%410%9%5%6%6%6%7%25%
1491
16th to endDay
6%12%6%9%9%45%5%5%7%27%
1538
March1st to 15thDay
7%15%7%8%7%335%5%6%28%
1963
16th to endDay
11%16%5%7%6%35%5%5%7%26%
2270
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%
2160
16th to endDay
11%5%35%6%35%5%7%7%36%
1998
October1st to 15thDay
12%11%48%6%35%446%31%
1792
16th to endDay
15%13%46%6%3446%7%29%
1644
November1st to 15thDay
14%12%47%6%34446%29%
1441
16th to endDay
10%13%5%10%9%5%6%5%5%6%21%
1248
December1st to 15thDay
10%15%5%9%7%35%7%47%22%
1170
16th to endDay
7%12%410%10%5%6%6%6%8%19%
1248
January1st to 15thNight
7%11%6%10%9%5%6%5%6%7%22%
3105
16th to endNight
10%16%5%7%6%45%46%7%25%
3162
February1st to 15thNight
8%12%5%9%9%4446%8%25%
2688
16th to endNight
5%9%5%9%10%46%6%7%7%25%
2222
March1st to 15thNight
7%13%5%10%7%36%46%7%27%
2327
16th to endNight
9%11%46%6%45%5%6%7%33%
2076
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%45%
1800
16th to endNight
11%6%35%5%35%46%8%38%
1962
October1st to 15thNight
12%10%36%5%35%5%6%8%31%
2168
16th to endNight
13%12%46%5%3445%6%31%
2580
November1st to 15thNight
11%12%46%6%35%5%46%32%
2733
16th to endNight
8%13%6%10%8%46%45%6%24%
3042
December1st to 15thNight
9%15%5%10%7%45%46%6%23%
3120
16th to endNight
6%12%5%10%9%5%7%6%6%8%20%
3328

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
61%8%15%11%2
1164
16th to endDay
56%9%14%13%41
1427
February1st to 15thDay
55%9%14%13%6%
1491
16th to endDay
54%8%16%15%3
1538
March1st to 15thDay
54%6%14%17%6%
1963
16th to endDay
57%7%17%14%3
2270
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%
2160
16th to endDay
43%10%19%20%6%
1998
October1st to 15thDay
54%7%15%20%2
1792
16th to endDay
52%8%18%16%3
1644
November1st to 15thDay
54%8%13%19%4
1441
16th to endDay
61%7%14%11%4
1248
December1st to 15thDay
59%7%14%13%4
1170
16th to endDay
60%6%12%14%4
1248
January1st to 15thNight
58%9%15%12%3
3105
16th to endNight
57%7%13%15%41
3162
February1st to 15thNight
55%7%16%15%5%
2700
16th to endNight
53%8%16%17%3
2222
March1st to 15thNight
53%8%13%19%3
2327
16th to endNight
48%6%16%20%7%
2080
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%9%22%25%7%
1800
16th to endNight
42%11%16%21%7%
1962
October1st to 15thNight
48%8%18%19%4
2168
16th to endNight
51%8%16%20%2
2580
November1st to 15thNight
51%8%14%21%4
2733
16th to endNight
59%7%12%16%2
3042
December1st to 15thNight
60%7%13%14%4
3120
16th to endNight
58%9%11%15%4
3328

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%5%16%34%15%14%
90
16th to endDay
17%7%21%34%13%5%
96
February1st to 15thDay
7%8%31%35%12%4
93
16th to endDay
13%6%28%30%16%4
250
March1st to 15thDay
18%8%29%25%16%1
330
16th to endDay
19%7%26%29%15%1
311
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%8%21%29%17%5%
315
16th to endDay
11%18%27%26%11%3
315
October1st to 15thDay
21%16%24%22%11%3
307
16th to endDay
25%10%13%32%15%3
123
November1st to 15thDay
21%8%28%28%11%1
90
16th to endDay
17%8%20%27%20%5%
90
December1st to 15thDay
11%218%33%28%5%
90
16th to endDay
8%9%12%35%29%5%
96
January1st to 15thNight
13%8%22%36%16%2
1020
16th to endNight
18%10%26%31%11%1
922
February1st to 15thNight
14%8%23%32%17%3
771
16th to endNight
9%322%37%23%3
684
March1st to 15thNight
11%8%26%34%15%2
780
16th to endNight
14%417%37%23%3
792
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
11%417%36%25%2
720
16th to endNight
14%9%25%29%18%1
716
October1st to 15thNight
17%9%26%30%14%1
720
16th to endNight
19%9%28%28%11%1
768
November1st to 15thNight
15%8%28%33%12%2
833
16th to endNight
14%7%25%36%14%1
1002
December1st to 15thNight
16%8%22%38%13%1
1020
16th to endNight
12%6%21%35%21%2
1088
Page generated at 2018-03-22 08:34:21. Version ac04

Copyright 2018 A. Danko


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