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 2005-11-06 to 2024-01-11.

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%
23537
10%
74841
6%
23488
43%
23488
17%
53221

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 10thNight
35%
1037
9%
3026
6%
1036
38%
1036
13%
2377
January11th to 20thNight
31%
952
11%
2860
6%
952
36%
952
12%
2195
January21st to endNight
27%
880
12%
2970
7%
880
34%
880
11%
2254
February1st to 10thNight
37%
739
9%
2564
10%
739
40%
739
13%
1897
February11th to 20thNight
38%
702
11%
2352
10%
700
41%
700
13%
1766
February21st to endNight
41%
592
12%
1924
10%
592
46%
592
16%
1384
March1st to 10thNight
39%
720
15%
2160
12%
720
43%
720
18%
1539
March11th to 20thNight
40%
720
13%
2052
9%
720
42%
720
19%
1502
March21st to endNight
45%
792
13%
2032
7%
792
47%
792
22%
1493
April1st to 10thNight
42%
720
12%
1800
5%
720
46%
720
22%
1327
April11th to 20thNight
45%
481
13%
1549
12%
481
49%
481
20%
1063
April21st to endNight
38%
360
9%
1440
11%
360
44%
360
14%
974
May1st to 10thNight
38%
360
3%
1440
1%
360
39%
360
13%
988
May11th to 20thNight
47%
354
0%
1121
0%
354
47%
354
25%
711
May21st to endNight
45%
388
0%
1164
0%
388
45%
388
20%
830
June1st to 10thNight
43%
360
0%
1080
0%
360
43%
360
18%
770
June11th to 20thNight
49%
360
0%
1080
0%
360
49%
360
17%
796
June21st to endNight
55%
360
0%
1080
0%
360
55%
360
27%
694
July1st to 10thNight
52%
350
0%
1050
0%
350
52%
350
24%
709
July11th to 20thNight
55%
348
0%
1044
0%
348
55%
348
21%
733
July21st to endNight
58%
394
0%
1214
0%
372
59%
372
26%
756
August1st to 10thNight
59%
358
3%
1341
2%
356
59%
356
20%
833
August11th to 20thNight
51%
356
11%
1424
13%
356
57%
356
21%
827
August21st to endNight
53%
514
14%
1702
13%
514
57%
514
23%
1093
September1st to 10thNight
50%
720
10%
1800
5%
720
52%
720
28%
1239
September11th to 20thNight
50%
720
18%
1800
9%
720
52%
720
29%
1227
September21st to endNight
37%
720
15%
2042
7%
720
43%
720
22%
1416
October1st to 10thNight
40%
720
11%
2160
6%
720
45%
720
19%
1500
October11th to 20thNight
35%
720
13%
2260
8%
720
42%
720
17%
1589
October21st to endNight
30%
792
13%
2700
7%
792
39%
792
14%
1915
November1st to 10thNight
34%
752
15%
2602
13%
752
40%
752
13%
1887
November11th to 20thNight
31%
950
10%
2850
5%
950
35%
950
14%
2153
November21st to endNight
32%
1031
9%
3021
3%
1031
36%
1031
14%
2286
December1st to 10thNight
33%
1040
14%
3040
8%
1040
38%
1040
16%
2261
December11th to 20thNight
34%
1040
10%
3704
4%
1039
39%
1039
11%
2844
December21st to endNight
37%
1135
8%
5393
5%
1114
42%
1114
10%
3393

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
10%9%47%7%46%6%6%8%33%
74503
Night
9%10%48%7%46%6%6%8%31%
75201
TransparencyDay
46%10%17%20%7%1
74165
Night
49%9%15%19%7%1
75057
SeeingDay
15%11%26%27%17%4
15539
Night
14%9%25%33%17%2
23552

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 10thDay
8%12%6%11%8%7%7%7%6%7%21%
1139
11th to 20thDay
8%14%6%11%9%5%6%6%6%8%21%
1130
21st to endDay
9%15%5%8%9%47%46%8%25%
1386
February1st to 10thDay
6%12%410%10%6%7%5%5%9%25%
1395
11th to 20thDay
6%13%5%9%9%5%6%6%6%8%25%
1493
21st to endDay
411%8%12%8%5%5%6%6%8%28%
1332
March1st to 10thDay
6%13%7%10%8%45%5%5%7%30%
1800
11th to 20thDay
9%13%6%8%7%35%5%6%8%29%
1906
21st to endDay
8%16%5%9%7%45%5%5%6%29%
2323
April1st to 10thDay
6%10%48%8%46%7%7%9%31%
2160
11th to 20thDay
9%12%49%7%46%6%5%8%29%
2357
21st to endDay
12%10%47%7%47%6%6%8%30%
2520
May1st to 10thDay
11%8%45%7%47%6%6%9%33%
2520
11th to 20thDay
11%7%35%5%46%5%6%7%39%
2774
21st to endDay
16%6%35%6%46%7%7%9%31%
3111
June1st to 10thDay
13%6%36%5%36%6%7%9%35%
2880
11th to 20thDay
16%7%48%7%46%6%7%8%28%
2880
21st to endDay
9%5%26%6%36%6%7%8%41%
2880
July1st to 10thDay
11%6%25%5%45%6%8%10%38%
2880
11th to 20thDay
13%5%36%6%45%6%7%9%36%
2880
21st to endDay
10%5%25%5%45%6%8%9%42%
3029
August1st to 10thDay
10%7%36%6%45%6%6%9%38%
2590
11th to 20thDay
9%5%245%45%6%6%9%44%
2475
21st to endDay
11%5%25%7%45%6%7%9%38%
2653
September1st to 10thDay
14%5%25%5%35%5%6%8%42%
2160
11th to 20thDay
11%6%25%7%45%5%7%7%40%
2160
21st to endDay
10%6%47%7%35%5%7%8%36%
1918
October1st to 10thDay
11%11%47%7%36%6%5%7%34%
1800
11th to 20thDay
10%10%48%8%45%46%7%33%
1699
21st to endDay
12%13%47%7%345%6%7%31%
1656
November1st to 10thDay
15%11%410%7%35%5%5%7%28%
1456
11th to 20thDay
10%13%6%9%8%45%6%5%6%29%
1330
21st to endDay
9%13%411%9%5%7%45%6%27%
1159
December1st to 10thDay
9%14%410%8%46%7%5%7%27%
1140
11th to 20thDay
8%14%5%9%9%6%7%7%6%10%20%
1442
21st to endDay
5%8%37%7%5%7%8%8%10%33%
2090
January1st to 10thNight
7%13%6%11%9%6%7%6%7%7%22%
3026
11th to 20thNight
7%12%6%10%10%5%7%5%6%8%25%
2860
21st to endNight
9%17%6%9%7%46%46%7%24%
2970
February1st to 10thNight
6%13%6%10%10%5%5%47%8%25%
2564
11th to 20thNight
8%12%5%10%9%47%6%6%9%24%
2350
21st to endNight
410%5%11%10%46%7%7%8%27%
1924
March1st to 10thNight
5%10%5%11%8%36%5%7%7%32%
2160
11th to 20thNight
7%13%48%7%46%6%6%8%30%
2051
21st to endNight
8%13%47%7%5%5%46%7%33%
2032
April1st to 10thNight
5%9%39%10%46%7%7%7%34%
1800
11th to 20thNight
10%12%38%6%35%6%6%8%33%
1549
21st to endNight
12%9%49%6%45%5%6%8%33%
1440
May1st to 10thNight
11%10%47%6%5%5%7%6%7%31%
1440
11th to 20thNight
10%7%27%6%345%6%10%40%
1121
21st to endNight
15%6%37%7%36%6%7%8%31%
1164
June1st to 10thNight
11%8%47%7%46%6%5%7%34%
1080
11th to 20thNight
15%9%37%6%36%7%7%9%28%
1080
21st to endNight
12%6%25%5%37%5%6%10%39%
1080
July1st to 10thNight
9%6%47%7%45%6%6%9%38%
1080
11th to 20thNight
12%5%25%5%47%7%9%11%33%
1080
21st to endNight
6%426%6%46%5%7%12%42%
1285
August1st to 10thNight
9%435%6%47%6%8%9%40%
1348
11th to 20thNight
8%4246%5%5%6%6%8%45%
1424
21st to endNight
10%5%26%5%45%6%8%9%39%
1702
September1st to 10thNight
13%7%25%435%6%6%8%41%
1800
11th to 20thNight
11%7%25%6%35%45%9%44%
1800
21st to endNight
10%6%47%5%45%5%6%7%40%
2042
October1st to 10thNight
11%9%47%6%45%6%6%8%34%
2160
11th to 20thNight
10%10%47%6%46%6%7%8%33%
2260
21st to endNight
12%13%48%6%345%6%7%32%
2700
November1st to 10thNight
14%13%48%7%45%5%5%7%29%
2602
11th to 20thNight
7%15%6%9%7%46%6%5%7%27%
2850
21st to endNight
7%11%5%10%9%5%7%5%6%7%26%
3021
December1st to 10thNight
7%12%5%9%9%46%6%7%7%28%
3040
11th to 20thNight
8%15%5%11%8%5%8%6%6%7%22%
3750
21st to endNight
48%37%9%5%8%7%8%9%31%
5566

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 10thDay
59%9%15%13%4
1139
11th to 20thDay
59%9%13%13%33
1130
21st to endDay
58%8%13%15%6%
1386
February1st to 10thDay
55%8%12%14%10%1
1395
11th to 20thDay
54%11%14%15%6%
1501
21st to endDay
53%8%16%16%6%1
1332
March1st to 10thDay
53%6%14%18%8%1
1800
11th to 20thDay
51%8%15%19%6%1
1906
21st to endDay
55%8%16%16%5%
2323
April1st to 10thDay
46%10%15%20%8%1
2160
11th to 20thDay
52%9%15%18%7%
2357
21st to endDay
50%9%13%21%6%
2520
May1st to 10thDay
45%9%17%20%8%1
2520
11th to 20thDay
43%8%13%21%14%1
2778
21st to endDay
47%10%15%21%6%1
3112
June1st to 10thDay
43%10%16%21%9%1
2880
11th to 20thDay
51%10%14%18%5%
2880
21st to endDay
39%10%18%23%9%
2880
July1st to 10thDay
38%11%19%24%8%
2801
11th to 20thDay
44%12%22%19%4
2793
21st to endDay
34%12%23%27%4
2860
August1st to 10thDay
41%10%22%23%4
2572
11th to 20thDay
34%10%23%27%6%
2475
21st to endDay
41%11%19%24%6%
2653
September1st to 10thDay
38%10%24%23%4
2160
11th to 20thDay
40%10%19%25%6%
2160
21st to endDay
43%11%18%20%8%
1918
October1st to 10thDay
49%8%16%22%5%
1800
11th to 20thDay
49%9%16%22%4
1699
21st to endDay
50%8%18%18%6%
1656
November1st to 10thDay
55%9%12%19%5%
1456
11th to 20thDay
54%8%18%15%5%
1330
21st to endDay
57%6%15%15%7%1
1159
December1st to 10thDay
54%9%13%13%10%1
1140
11th to 20thDay
58%7%12%17%5%
1444
21st to endDay
40%11%18%18%11%1
2090
January1st to 10thNight
58%9%14%13%5%1
3026
11th to 20thNight
56%10%13%15%6%2
2860
21st to endNight
58%8%13%14%7%
2970
February1st to 10thNight
56%7%15%14%8%1
2564
11th to 20thNight
55%9%14%17%5%
2352
21st to endNight
51%9%14%19%7%1
1924
March1st to 10thNight
48%8%15%21%7%1
2160
11th to 20thNight
50%9%13%21%6%
2052
21st to endNight
48%8%15%21%8%
2032
April1st to 10thNight
46%10%12%19%12%1
1800
11th to 20thNight
46%8%13%22%9%1
1549
21st to endNight
47%9%11%23%8%2
1440
May1st to 10thNight
49%10%12%20%9%
1440
11th to 20thNight
39%7%12%25%15%1
1121
21st to endNight
48%9%13%19%10%1
1164
June1st to 10thNight
46%11%11%20%12%1
1080
11th to 20thNight
51%10%14%19%5%1
1080
21st to endNight
37%9%21%22%10%1
1080
July1st to 10thNight
40%10%16%24%8%
1050
11th to 20thNight
41%14%20%20%5%
1044
21st to endNight
32%14%22%28%4
1214
August1st to 10thNight
35%13%19%25%7%
1341
11th to 20thNight
34%10%20%28%7%1
1424
21st to endNight
38%11%21%22%8%
1702
September1st to 10thNight
38%10%22%23%7%1
1800
11th to 20thNight
38%9%17%30%6%
1800
21st to endNight
42%10%15%22%9%1
2042
October1st to 10thNight
45%10%18%20%7%1
2160
11th to 20thNight
47%9%16%22%5%
2260
21st to endNight
50%9%15%18%7%
2700
November1st to 10thNight
54%8%12%22%4
2602
11th to 20thNight
55%9%14%17%5%
2850
21st to endNight
55%8%14%17%5%1
3021
December1st to 10thNight
53%8%12%17%9%1
3040
11th to 20thNight
56%10%13%14%6%
3747
21st to endNight
44%10%17%20%8%1
5566

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 10thDay
10%9%30%36%9%6%
180
11th to 20thDay
19%9%30%32%8%3
160
21st to endDay
14%13%28%32%10%3
176
February1st to 10thDay
14%14%29%29%9%4
160
11th to 20thDay
14%13%28%28%13%3
253
21st to endDay
10%12%30%28%14%5%
280
March1st to 10thDay
14%14%23%27%16%5%
420
11th to 20thDay
10%13%30%28%15%3
420
21st to endDay
17%15%26%25%17%2
462
April1st to 10thDay
11%16%34%22%13%4
420
11th to 20thDay
16%13%27%25%14%5%
412
21st to endDay
21%13%30%23%11%2
420
May1st to 10thDay
16%16%31%23%9%4
423
11th to 20thDay
14%8%25%31%18%4
743
21st to endDay
16%9%23%26%20%5%
874
June1st to 10thDay
14%12%28%28%16%2
810
11th to 20thDay
18%8%26%25%21%3
810
21st to endDay
12%7%21%27%24%8%
810
July1st to 10thDay
12%8%22%31%22%6%
796
11th to 20thDay
13%7%23%27%20%9%
792
21st to endDay
10%6%26%31%21%5%
775
August1st to 10thDay
13%11%18%30%22%7%
530
11th to 20thDay
12%12%32%23%15%6%
437
21st to endDay
16%13%25%25%16%6%
495
September1st to 10thDay
18%10%24%27%16%5%
450
11th to 20thDay
17%11%24%30%14%5%
450
21st to endDay
12%21%29%24%11%2
450
October1st to 10thDay
21%15%24%24%12%4
450
11th to 20thDay
16%14%28%27%13%2
349
21st to endDay
19%12%24%27%17%2
234
November1st to 10thDay
21%11%26%29%13%2
180
11th to 20thDay
18%11%30%29%11%2
180
21st to endDay
17%15%26%27%13%2
180
December1st to 10thDay
13%12%32%26%14%4
180
11th to 20thDay
16%12%25%27%19%1
180
21st to endDay
10%7%21%40%19%3
198
January1st to 10thNight
13%8%24%38%14%2
1040
11th to 20thNight
14%12%27%35%11%1
952
21st to endNight
18%12%28%30%11%1
880
February1st to 10thNight
14%11%23%31%17%4
739
11th to 20thNight
14%8%26%35%16%2
704
21st to endNight
7%6%27%35%21%4
592
March1st to 10thNight
8%10%26%33%18%4
720
11th to 20thNight
12%7%29%32%19%1
720
21st to endNight
15%7%20%33%23%2
792
April1st to 10thNight
9%8%26%35%20%2
720
11th to 20thNight
15%7%24%35%16%2
481
21st to endNight
14%9%27%29%19%1
360
May1st to 10thNight
15%9%28%31%15%3
360
11th to 20thNight
12%7%25%30%24%1
354
21st to endNight
17%6%21%33%21%3
389
June1st to 10thNight
13%9%25%29%23%2
360
11th to 20thNight
18%5%17%32%24%4
360
21st to endNight
13%321%33%28%2
360
July1st to 10thNight
11%5%22%31%30%1
350
11th to 20thNight
12%5%18%35%23%6%
348
21st to endNight
7%5%21%40%24%3
394
August1st to 10thNight
11%413%27%39%6%
358
11th to 20thNight
10%6%25%31%26%2
356
21st to endNight
13%224%35%23%3
514
September1st to 10thNight
16%6%20%36%20%2
720
11th to 20thNight
14%7%21%32%25%2
720
21st to endNight
14%12%28%30%14%1
720
October1st to 10thNight
16%10%25%32%16%1
720
11th to 20thNight
17%10%28%31%12%2
720
21st to endNight
19%11%27%31%11%1
792
November1st to 10thNight
19%8%25%32%14%2
752
11th to 20thNight
14%11%31%34%10%
950
21st to endNight
13%12%28%34%12%1
1031
December1st to 10thNight
13%10%29%34%12%1
1040
11th to 20thNight
14%11%25%36%13%2
1040
21st to endNight
13%6%25%36%17%2
1144
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Copyright 2024 Attilla Danko


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