Grande Prairie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grande Prairie clear sky chart from 2005-11-06 to 2024-02-10.

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%
23619
10%
81116
7%
23547
43%
23547
16%
57186

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
33%
1016
11%
5006
5%
1006
37%
1006
8%
3705
January11th to 20thNight
33%
1004
17%
4929
5%
995
38%
995
9%
3306
January21st to endNight
27%
880
8%
5055
7%
866
34%
866
7%
3471
February1st to 10thNight
35%
758
11%
2652
11%
758
37%
758
12%
1967
February11th to 20thNight
35%
701
11%
2391
10%
700
39%
700
13%
1797
February21st to endNight
44%
592
12%
1850
11%
592
48%
592
17%
1353
March1st to 10thNight
38%
720
15%
2160
11%
720
43%
720
19%
1536
March11th to 20thNight
39%
720
16%
2118
10%
720
42%
720
20%
1516
March21st to endNight
45%
792
13%
1980
6%
792
47%
792
20%
1503
April1st to 10thNight
41%
720
10%
1800
5%
720
44%
720
20%
1347
April11th to 20thNight
42%
536
12%
1604
10%
536
45%
536
19%
1144
April21st to endNight
36%
360
9%
1440
10%
360
43%
360
15%
973
May1st to 10thNight
40%
360
5%
1435
4%
360
42%
360
15%
972
May11th to 20thNight
47%
354
2%
1232
0%
354
47%
354
22%
783
May21st to endNight
46%
388
0%
1164
0%
388
46%
388
22%
792
June1st to 10thNight
43%
360
0%
1080
0%
360
43%
360
21%
747
June11th to 20thNight
43%
360
0%
1080
0%
360
43%
360
18%
796
June21st to endNight
48%
360
0%
1080
0%
360
48%
360
24%
725
July1st to 10thNight
55%
350
0%
1050
0%
350
55%
350
25%
685
July11th to 20thNight
50%
348
0%
1044
0%
348
50%
348
21%
736
July21st to endNight
56%
394
1%
1224
0%
372
58%
372
25%
784
August1st to 10thNight
61%
358
5%
1424
6%
356
62%
356
22%
843
August11th to 20thNight
55%
356
12%
1424
14%
356
62%
356
23%
806
August21st to endNight
45%
535
14%
1723
13%
535
48%
535
21%
1151
September1st to 10thNight
46%
720
10%
1800
6%
720
48%
720
25%
1296
September11th to 20thNight
50%
720
17%
1829
9%
720
53%
720
29%
1239
September21st to endNight
41%
720
17%
1988
9%
720
46%
720
23%
1365
October1st to 10thNight
39%
720
11%
2160
7%
720
43%
720
19%
1535
October11th to 20thNight
38%
720
15%
2306
9%
720
47%
720
18%
1587
October21st to endNight
29%
792
12%
2600
5%
792
39%
792
14%
1872
November1st to 10thNight
33%
787
12%
2637
9%
787
38%
787
13%
1966
November11th to 20thNight
26%
950
11%
2850
5%
950
32%
950
13%
2184
November21st to endNight
31%
961
11%
2873
5%
961
36%
961
15%
2184
December1st to 10thNight
33%
1040
14%
3040
7%
1040
38%
1040
18%
2248
December11th to 20thNight
33%
1040
11%
3711
6%
1039
37%
1039
11%
2883
December21st to endNight
36%
1127
8%
5377
5%
1114
42%
1114
10%
3389

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%48%7%46%6%6%8%32%
77289
Night
9%11%5%9%7%46%6%6%8%30%
81622
TransparencyDay
47%9%16%20%7%1
76971
Night
50%8%15%19%8%1
81520
SeeingDay
14%8%23%29%19%7%
15389
Night
14%7%26%34%17%2
23701

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
5%14%8%14%11%5%6%7%5%8%19%
1899
11th to 20thDay
8%14%48%7%5%9%8%9%7%21%
1925
21st to endDay
8%11%47%7%47%7%8%9%27%
2579
February1st to 10thDay
8%13%6%10%9%5%5%6%7%8%23%
1512
11th to 20thDay
6%16%5%11%9%5%5%6%6%7%24%
1454
21st to endDay
6%14%6%10%9%5%7%5%6%6%26%
1405
March1st to 10thDay
5%11%5%10%9%5%6%8%6%7%27%
1800
11th to 20thDay
8%12%6%10%7%36%5%6%6%28%
1838
21st to endDay
8%14%6%10%8%36%6%7%8%24%
2376
April1st to 10thDay
5%9%6%9%8%5%7%6%7%8%30%
2160
11th to 20thDay
9%11%49%8%36%6%6%7%31%
2305
21st to endDay
10%11%38%7%46%6%7%8%30%
2520
May1st to 10thDay
11%9%49%7%46%5%5%7%33%
2524
11th to 20thDay
10%7%36%6%47%6%7%7%37%
2658
21st to endDay
15%6%37%7%45%6%6%8%32%
3111
June1st to 10thDay
13%7%37%7%45%5%6%8%34%
2880
11th to 20thDay
17%8%48%7%45%6%6%7%28%
2880
21st to endDay
11%7%36%7%46%5%6%8%38%
2880
July1st to 10thDay
13%6%26%5%36%6%6%9%38%
2880
11th to 20thDay
12%6%36%6%47%6%7%8%36%
2880
21st to endDay
11%435%6%35%6%6%8%42%
3015
August1st to 10thDay
10%6%25%5%46%5%7%9%40%
2507
11th to 20thDay
7%5%26%5%45%6%6%9%43%
2475
21st to endDay
12%6%37%6%46%6%6%9%35%
2630
September1st to 10thDay
15%6%36%5%345%5%6%42%
2160
11th to 20thDay
14%6%36%5%3447%8%40%
2131
21st to endDay
12%6%36%5%35%5%7%8%39%
1968
October1st to 10thDay
11%9%410%7%35%46%7%34%
1800
11th to 20thDay
13%9%47%7%45%6%7%6%31%
1654
21st to endDay
11%13%6%7%6%35%5%6%6%31%
1752
November1st to 10thDay
13%15%6%9%9%5%5%45%6%24%
1422
11th to 20thDay
10%13%5%9%8%345%5%7%29%
1330
21st to endDay
8%14%5%11%9%45%46%8%27%
1307
December1st to 10thDay
9%11%7%7%8%5%7%5%5%5%30%
1140
11th to 20thDay
12%12%5%10%7%5%7%7%5%7%23%
1442
21st to endDay
5%9%37%7%46%7%8%9%36%
2090
January1st to 10thNight
5%14%8%15%10%45%5%5%6%23%
5046
11th to 20thNight
7%11%5%7%9%5%7%8%10%9%23%
5002
21st to endNight
10%15%5%8%6%46%5%7%9%26%
5077
February1st to 10thNight
9%15%6%10%8%45%46%8%25%
2652
11th to 20thNight
7%14%6%12%9%46%6%5%7%25%
2389
21st to endNight
412%7%9%9%5%7%5%7%7%27%
1850
March1st to 10thNight
6%11%6%10%9%45%5%5%7%31%
2160
11th to 20thNight
9%14%5%8%6%35%5%6%8%29%
2117
21st to endNight
8%12%6%8%5%5%7%6%6%8%28%
1980
April1st to 10thNight
6%10%5%10%8%5%7%7%7%9%26%
1800
11th to 20thNight
8%10%5%9%8%45%6%7%7%31%
1604
21st to endNight
11%11%47%6%36%6%6%7%32%
1440
May1st to 10thNight
12%10%38%8%45%6%5%7%32%
1435
11th to 20thNight
10%8%35%6%46%6%6%10%37%
1232
21st to endNight
14%9%45%5%346%8%7%35%
1164
June1st to 10thNight
11%8%48%6%46%6%6%7%35%
1080
11th to 20thNight
18%7%38%5%5%6%7%6%10%26%
1080
21st to endNight
12%6%36%6%35%6%8%9%35%
1080
July1st to 10thNight
11%5%26%6%35%7%6%8%42%
1080
11th to 20thNight
13%5%27%7%47%6%8%9%33%
1080
21st to endNight
10%5%35%6%5%6%7%7%9%38%
1296
August1st to 10thNight
9%5%35%5%45%5%7%10%43%
1432
11th to 20thNight
6%325%7%47%7%8%10%43%
1424
21st to endNight
11%6%38%7%36%5%7%9%36%
1723
September1st to 10thNight
13%7%37%6%45%5%7%8%36%
1800
11th to 20thNight
12%7%25%5%35%5%6%9%40%
1829
21st to endNight
12%7%37%6%35%46%8%37%
1988
October1st to 10thNight
11%10%36%7%5%6%5%5%8%33%
2160
11th to 20thNight
10%8%48%7%46%5%7%8%33%
2306
21st to endNight
12%13%5%8%6%46%6%6%7%30%
2600
November1st to 10thNight
14%14%5%9%7%45%5%6%6%25%
2637
11th to 20thNight
9%17%6%10%7%445%5%6%27%
2850
21st to endNight
10%14%5%10%8%445%5%7%27%
2873
December1st to 10thNight
8%12%5%9%9%5%5%5%6%7%30%
3040
11th to 20thNight
9%15%6%10%7%5%7%6%5%7%23%
3750
21st to endNight
410%48%8%5%6%7%6%8%33%
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
60%8%13%16%31
1899
11th to 20thDay
55%7%11%11%15%2
1943
21st to endDay
46%13%21%14%6%
2579
February1st to 10thDay
55%7%14%13%9%
1512
11th to 20thDay
58%9%14%14%6%
1462
21st to endDay
57%6%13%15%7%1
1405
March1st to 10thDay
51%9%15%18%7%
1800
11th to 20thDay
52%7%14%18%7%1
1838
21st to endDay
54%10%17%14%4
2376
April1st to 10thDay
47%11%17%18%7%1
2160
11th to 20thDay
48%8%16%19%8%1
2305
21st to endDay
48%9%14%21%7%
2520
May1st to 10thDay
49%8%15%18%9%1
2524
11th to 20thDay
42%8%15%21%13%1
2662
21st to endDay
47%9%14%19%9%2
3112
June1st to 10thDay
47%8%15%20%9%1
2880
11th to 20thDay
53%9%13%18%7%
2880
21st to endDay
42%9%16%23%9%1
2880
July1st to 10thDay
39%10%17%24%8%1
2801
11th to 20thDay
43%11%20%22%4
2793
21st to endDay
36%10%22%26%6%
2847
August1st to 10thDay
37%13%22%22%5%
2490
11th to 20thDay
35%10%21%28%6%
2475
21st to endDay
44%9%19%22%6%
2630
September1st to 10thDay
42%7%21%23%6%1
2160
11th to 20thDay
41%8%19%24%7%
2131
21st to endDay
40%10%17%23%10%1
1968
October1st to 10thDay
48%8%17%21%6%
1800
11th to 20thDay
49%8%16%21%5%
1654
21st to endDay
51%8%16%20%6%
1752
November1st to 10thDay
59%5%13%17%5%1
1422
11th to 20thDay
54%7%17%16%7%
1330
21st to endDay
56%6%14%15%7%2
1307
December1st to 10thDay
54%8%12%17%9%1
1140
11th to 20thDay
57%7%16%14%6%
1444
21st to endDay
39%10%16%22%11%2
2090
January1st to 10thNight
60%7%11%15%6%1
5046
11th to 20thNight
52%7%12%13%16%1
5046
21st to endNight
51%11%19%14%5%
5077
February1st to 10thNight
57%7%14%13%9%
2652
11th to 20thNight
58%7%12%18%5%
2391
21st to endNight
53%7%16%17%6%1
1850
March1st to 10thNight
52%5%15%20%8%
2160
11th to 20thNight
50%6%11%23%9%
2118
21st to endNight
51%9%14%19%7%1
1980
April1st to 10thNight
49%9%15%17%9%1
1800
11th to 20thNight
50%8%13%19%9%1
1604
21st to endNight
48%9%12%22%9%1
1440
May1st to 10thNight
50%7%12%20%11%1
1435
11th to 20thNight
41%8%13%22%15%1
1232
21st to endNight
44%8%16%21%10%1
1164
June1st to 10thNight
46%8%14%22%10%
1080
11th to 20thNight
50%10%15%19%5%
1080
21st to endNight
41%9%19%20%10%
1080
July1st to 10thNight
37%12%16%26%9%1
1050
11th to 20thNight
44%11%19%21%5%
1044
21st to endNight
36%12%24%24%5%
1224
August1st to 10thNight
34%11%23%24%7%
1424
11th to 20thNight
30%12%21%28%8%1
1424
21st to endNight
43%9%18%23%7%1
1723
September1st to 10thNight
44%8%19%22%6%1
1800
11th to 20thNight
39%8%19%26%9%
1829
21st to endNight
43%8%16%21%11%1
1988
October1st to 10thNight
49%8%16%20%7%
2160
11th to 20thNight
47%8%17%23%5%
2306
21st to endNight
52%8%14%18%8%
2600
November1st to 10thNight
57%7%13%18%5%1
2637
11th to 20thNight
58%8%12%15%8%
2850
21st to endNight
56%8%13%16%5%2
2873
December1st to 10thNight
52%7%13%17%10%1
3040
11th to 20thNight
59%8%12%14%6%
3747
21st to endNight
45%9%14%24%7%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
11%9%17%38%19%6%
180
11th to 20thDay
18%8%19%32%18%4
180
21st to endDay
10%12%26%34%15%4
198
February1st to 10thDay
12%12%17%34%18%6%
178
11th to 20thDay
11%14%23%31%16%5%
214
21st to endDay
10%9%21%35%22%4
313
March1st to 10thDay
9%8%25%34%19%5%
420
11th to 20thDay
9%6%22%36%18%8%
420
21st to endDay
13%7%25%29%22%4
462
April1st to 10thDay
6%9%26%33%16%9%
420
11th to 20thDay
13%10%19%34%17%7%
412
21st to endDay
17%11%22%27%18%5%
420
May1st to 10thDay
17%10%24%29%17%3
427
11th to 20thDay
15%6%19%31%22%8%
629
21st to endDay
16%6%21%27%22%8%
874
June1st to 10thDay
13%9%27%31%17%4
810
11th to 20thDay
20%8%20%26%21%5%
810
21st to endDay
14%6%20%27%23%10%
810
July1st to 10thDay
15%5%21%29%24%7%
796
11th to 20thDay
12%5%26%27%21%8%
792
21st to endDay
11%7%21%32%21%8%
761
August1st to 10thDay
13%8%19%26%22%12%
447
11th to 20thDay
9%11%28%28%16%8%
437
21st to endDay
15%8%27%28%13%8%
495
September1st to 10thDay
19%11%22%23%18%6%
450
11th to 20thDay
19%7%24%24%19%7%
450
21st to endDay
12%11%33%22%17%6%
450
October1st to 10thDay
17%13%23%25%18%5%
450
11th to 20thDay
19%12%21%27%16%5%
304
21st to endDay
19%13%27%21%15%6%
282
November1st to 10thDay
17%8%26%27%19%4
180
11th to 20thDay
17%8%24%34%15%2
180
21st to endDay
12%9%29%34%9%5%
180
December1st to 10thDay
8%7%27%37%15%6%
180
11th to 20thDay
12%11%24%33%17%3
180
21st to endDay
15%6%16%38%17%9%
198
January1st to 10thNight
14%7%24%35%17%3
1040
11th to 20thNight
13%9%27%32%15%2
1026
21st to endNight
16%13%28%30%12%1
895
February1st to 10thNight
16%10%23%29%17%5%
758
11th to 20thNight
14%8%25%33%18%2
704
21st to endNight
9%7%23%36%20%5%
592
March1st to 10thNight
9%8%30%32%18%3
720
11th to 20thNight
14%6%26%38%13%2
720
21st to endNight
14%5%23%34%22%2
792
April1st to 10thNight
10%7%28%37%15%3
720
11th to 20thNight
13%8%23%37%18%1
536
21st to endNight
12%10%31%28%19%1
360
May1st to 10thNight
16%7%28%35%13%2
360
11th to 20thNight
13%6%26%35%19%1
354
21st to endNight
16%6%21%33%22%2
389
June1st to 10thNight
16%6%24%30%23%
360
11th to 20thNight
21%322%29%23%3
360
21st to endNight
14%425%33%21%3
360
July1st to 10thNight
12%321%40%23%1
350
11th to 20thNight
15%421%35%23%3
348
21st to endNight
11%421%36%24%4
394
August1st to 10thNight
13%317%31%32%4
358
11th to 20thNight
7%427%37%24%2
356
21st to endNight
15%424%36%19%1
535
September1st to 10thNight
16%5%23%35%19%2
720
11th to 20thNight
14%6%21%35%20%3
720
21st to endNight
16%10%26%32%14%2
720
October1st to 10thNight
18%7%29%30%14%1
720
11th to 20thNight
13%9%28%36%13%3
720
21st to endNight
17%10%32%30%9%1
792
November1st to 10thNight
20%6%26%32%14%3
787
11th to 20thNight
19%10%31%29%9%1
950
21st to endNight
16%10%27%35%10%2
961
December1st to 10thNight
13%8%28%35%13%3
1040
11th to 20thNight
14%8%27%32%15%3
1040
21st to endNight
14%6%25%36%18%2
1144
Page generated at 2024-02-07 04:11:55. Version ac07

Copyright 2024 Attilla Danko


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