Leduc
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Leduc clear sky chart from 2005-11-06 to 2024-03-28.

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%
23707
11%
81034
8%
23653
45%
23653
17%
55419

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%
936
10%
4683
5%
926
39%
926
10%
3290
January11th to 20thNight
33%
935
19%
4606
7%
930
40%
930
11%
2985
January21st to endNight
29%
931
10%
5000
7%
920
37%
920
9%
3199
February1st to 10thNight
38%
760
11%
2660
9%
760
43%
760
14%
1921
February11th to 20thNight
38%
740
12%
2452
10%
740
43%
740
16%
1736
February21st to endNight
45%
628
15%
1983
14%
628
50%
628
19%
1387
March1st to 10thNight
40%
760
14%
2280
11%
760
44%
760
17%
1675
March11th to 20thNight
42%
760
15%
2112
9%
760
47%
760
22%
1513
March21st to endNight
39%
820
10%
2224
5%
820
42%
820
18%
1679
April1st to 10thNight
42%
634
13%
1714
7%
634
45%
634
22%
1236
April11th to 20thNight
38%
533
13%
1601
9%
533
42%
533
17%
1157
April21st to endNight
40%
540
11%
1620
9%
540
44%
540
21%
1113
May1st to 10thNight
40%
394
8%
1341
8%
394
43%
394
16%
958
May11th to 20thNight
47%
354
7%
1239
5%
354
49%
354
19%
817
May21st to endNight
40%
388
1%
1358
0%
388
40%
388
16%
949
June1st to 10thNight
43%
360
0%
1260
0%
360
43%
360
16%
893
June11th to 20thNight
39%
360
0%
1258
0%
360
39%
360
11%
973
June21st to endNight
56%
360
0%
1092
0%
360
56%
360
22%
749
July1st to 10thNight
56%
350
0%
1225
0%
350
56%
350
22%
791
July11th to 20thNight
56%
348
0%
1218
0%
348
56%
348
19%
823
July21st to endNight
61%
394
5%
1302
5%
372
62%
372
25%
778
August1st to 10thNight
56%
358
7%
1365
8%
356
58%
356
20%
855
August11th to 20thNight
59%
464
10%
1532
13%
464
60%
464
26%
955
August21st to endNight
55%
594
14%
1782
12%
594
57%
594
26%
1163
September1st to 10thNight
55%
583
14%
1672
11%
583
56%
583
27%
1096
September11th to 20thNight
54%
720
18%
1980
11%
720
57%
720
30%
1288
September21st to endNight
47%
720
19%
1980
12%
720
52%
720
29%
1290
October1st to 10thNight
45%
720
16%
2084
10%
720
50%
720
24%
1399
October11th to 20thNight
38%
720
17%
2308
11%
720
45%
720
23%
1523
October21st to endNight
38%
792
15%
2574
9%
792
45%
792
17%
1788
November1st to 10thNight
32%
922
14%
2587
8%
922
36%
922
16%
1947
November11th to 20thNight
32%
950
13%
2802
7%
950
38%
950
17%
2092
November21st to endNight
32%
950
9%
2850
5%
950
37%
950
18%
2080
December1st to 10thNight
34%
950
13%
2850
8%
950
38%
950
17%
2078
December11th to 20thNight
34%
949
11%
3478
6%
949
39%
949
14%
2534
December21st to endNight
37%
1030
9%
4962
6%
1026
42%
1026
14%
2709

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%45%6%6%8%34%
78270
Night
8%10%48%8%46%6%6%8%33%
81660
TransparencyDay
45%9%17%21%7%1
77972
Night
47%8%15%20%9%1
81538
SeeingDay
13%6%23%32%19%6%
14658
Night
13%6%27%36%16%2
23768

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
411%5%9%12%5%6%5%6%10%27%
2219
11th to 20thDay
5%9%5%8%6%36%7%7%9%33%
2199
21st to endDay
7%12%5%8%7%45%5%6%7%35%
2638
February1st to 10thDay
8%14%5%10%8%36%47%9%24%
1520
11th to 20thDay
6%12%7%10%9%46%6%6%7%27%
1615
21st to endDay
411%7%11%9%5%8%7%6%8%24%
1470
March1st to 10thDay
7%12%6%11%10%5%6%5%5%8%25%
1900
11th to 20thDay
7%12%48%6%35%5%7%9%34%
2066
21st to endDay
9%12%6%11%9%46%6%6%9%22%
2283
April1st to 10thDay
8%11%49%7%5%5%6%7%8%30%
2245
11th to 20thDay
11%12%5%7%6%35%6%7%8%29%
2310
21st to endDay
12%9%47%7%45%5%7%9%32%
2340
May1st to 10thDay
10%9%49%8%46%7%6%8%29%
2616
11th to 20thDay
8%7%36%6%46%6%7%8%40%
2654
21st to endDay
18%7%46%5%46%46%8%32%
2917
June1st to 10thDay
16%8%36%6%45%5%7%8%31%
2700
11th to 20thDay
18%9%47%8%47%6%6%7%24%
2700
21st to endDay
10%5%25%5%45%6%7%11%37%
2848
July1st to 10thDay
11%6%36%7%35%6%8%8%38%
2700
11th to 20thDay
10%6%26%6%46%6%7%10%36%
2700
21st to endDay
9%425%435%6%7%9%46%
2938
August1st to 10thDay
9%5%25%6%35%7%9%10%37%
2564
11th to 20thDay
8%5%25%6%35%5%7%10%43%
2368
21st to endDay
10%6%26%5%45%5%6%9%43%
2574
September1st to 10thDay
12%5%35%6%45%5%6%8%41%
2286
11th to 20thDay
14%7%245%335%5%9%42%
1980
21st to endDay
9%6%26%5%35%6%7%8%43%
1980
October1st to 10thDay
10%9%48%7%5%5%45%5%38%
1876
11th to 20thDay
10%8%48%6%35%5%5%8%38%
1651
21st to endDay
10%12%5%7%7%46%47%7%31%
1766
November1st to 10thDay
8%14%6%10%7%5%6%5%6%6%27%
1488
11th to 20thDay
7%11%6%12%7%35%5%6%7%31%
1375
21st to endDay
5%10%7%12%8%46%5%5%7%31%
1330
December1st to 10thDay
6%10%5%11%11%5%8%5%6%7%27%
1330
11th to 20thDay
7%10%6%9%9%45%7%7%9%27%
1682
21st to endDay
48%36%8%46%5%6%8%42%
2442
January1st to 10thNight
410%6%12%10%5%7%6%6%7%26%
4726
11th to 20thNight
48%49%11%6%6%7%7%7%33%
4699
21st to endNight
7%13%410%8%45%5%5%7%32%
5046
February1st to 10thNight
5%12%6%12%9%5%6%6%5%7%27%
2660
11th to 20thNight
6%12%5%10%8%5%6%7%6%7%29%
2451
21st to endNight
5%11%48%9%5%6%6%5%7%32%
1983
March1st to 10thNight
5%11%5%11%9%5%7%5%6%8%29%
2280
11th to 20thNight
7%9%5%8%7%47%6%8%8%31%
2112
21st to endNight
8%13%6%10%7%46%6%7%8%26%
2224
April1st to 10thNight
7%9%37%9%5%7%6%7%8%31%
1714
11th to 20thNight
10%11%5%9%8%5%7%5%5%7%28%
1601
21st to endNight
12%9%47%6%35%5%5%9%34%
1620
May1st to 10thNight
11%10%5%9%7%46%6%7%7%28%
1341
11th to 20thNight
10%8%46%8%36%6%6%7%35%
1239
21st to endNight
19%8%47%5%35%46%8%31%
1358
June1st to 10thNight
15%7%5%7%6%36%6%6%8%30%
1260
11th to 20thNight
17%9%48%8%5%6%8%6%8%21%
1258
21st to endNight
11%7%45%7%37%6%7%8%35%
1092
July1st to 10thNight
11%7%46%6%35%5%6%10%37%
1260
11th to 20thNight
8%5%37%7%5%7%7%8%9%34%
1260
21st to endNight
10%6%24436%6%7%11%42%
1379
August1st to 10thNight
10%7%25%6%35%6%8%9%40%
1372
11th to 20thNight
10%7%35%445%6%7%10%41%
1532
21st to endNight
10%6%26%5%36%6%7%9%40%
1782
September1st to 10thNight
12%5%36%5%346%6%8%42%
1672
11th to 20thNight
11%7%36%5%3445%8%44%
1980
21st to endNight
9%7%36%5%345%6%8%43%
1980
October1st to 10thNight
11%9%37%6%45%6%6%6%38%
2084
11th to 20thNight
9%9%47%6%45%5%6%8%38%
2308
21st to endNight
7%9%49%8%5%6%6%6%8%32%
2574
November1st to 10thNight
12%14%6%8%7%36%46%7%26%
2587
11th to 20thNight
7%13%6%9%7%46%5%6%7%29%
2802
21st to endNight
6%10%6%11%9%5%6%5%6%8%29%
2850
December1st to 10thNight
8%13%5%9%8%5%6%45%7%29%
2850
11th to 20thNight
6%12%6%10%8%46%7%6%8%26%
3510
21st to endNight
38%38%7%45%6%6%8%43%
5214

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
51%9%13%20%7%
2219
11th to 20thDay
45%7%11%15%20%2
2220
21st to endDay
46%7%18%23%5%
2638
February1st to 10thDay
54%5%16%16%8%1
1520
11th to 20thDay
54%8%14%16%8%
1624
21st to endDay
52%8%14%18%8%
1470
March1st to 10thDay
56%8%14%16%5%
1900
11th to 20thDay
45%7%15%21%11%1
2067
21st to endDay
56%9%14%16%4
2283
April1st to 10thDay
48%10%15%19%7%1
2245
11th to 20thDay
51%8%13%20%8%
2310
21st to endDay
47%8%16%20%7%2
2340
May1st to 10thDay
50%9%15%18%8%
2616
11th to 20thDay
39%8%15%27%10%
2658
21st to endDay
49%7%14%20%10%
2918
June1st to 10thDay
49%7%16%20%7%
2700
11th to 20thDay
57%9%15%15%4
2700
21st to endDay
38%11%22%23%5%1
2848
July1st to 10thDay
39%11%20%24%5%1
2626
11th to 20thDay
40%12%25%21%2
2619
21st to endDay
33%11%27%26%3
2775
August1st to 10thDay
37%12%25%22%3
2546
11th to 20thDay
34%9%26%24%7%
2368
21st to endDay
36%9%22%26%8%
2574
September1st to 10thDay
39%8%20%24%7%2
2286
11th to 20thDay
38%8%19%28%7%
1980
21st to endDay
36%10%19%26%8%2
1980
October1st to 10thDay
47%6%16%20%9%
1876
11th to 20thDay
42%8%18%22%10%
1651
21st to endDay
50%8%12%22%7%
1766
November1st to 10thDay
56%9%14%15%6%1
1488
11th to 20thDay
51%8%16%19%6%
1375
21st to endDay
51%9%15%18%6%1
1330
December1st to 10thDay
55%8%11%16%8%1
1330
11th to 20thDay
49%9%18%16%7%
1684
21st to endDay
38%8%10%26%16%2
2442
January1st to 10thNight
53%9%14%16%7%1
4726
11th to 20thNight
48%7%13%15%15%2
4740
21st to endNight
49%8%16%20%7%
5046
February1st to 10thNight
54%6%12%18%8%1
2660
11th to 20thNight
51%8%13%17%10%1
2452
21st to endNight
48%8%12%20%11%1
1983
March1st to 10thNight
52%8%13%19%7%1
2280
11th to 20thNight
46%9%14%20%10%1
2112
21st to endNight
53%8%15%17%6%1
2224
April1st to 10thNight
46%10%14%19%11%1
1714
11th to 20thNight
53%7%11%18%9%2
1601
21st to endNight
45%8%14%20%12%1
1620
May1st to 10thNight
50%9%12%18%9%1
1341
11th to 20thNight
45%8%11%22%13%1
1239
21st to endNight
50%8%12%17%10%2
1358
June1st to 10thNight
49%10%14%20%7%
1260
11th to 20thNight
58%10%15%12%4
1258
21st to endNight
42%12%21%21%41
1092
July1st to 10thNight
41%9%20%23%6%1
1225
11th to 20thNight
40%15%23%19%4
1218
21st to endNight
33%12%22%30%4
1302
August1st to 10thNight
39%11%22%25%3
1365
11th to 20thNight
36%10%22%25%6%1
1532
21st to endNight
38%10%18%25%8%1
1782
September1st to 10thNight
39%8%18%23%11%2
1672
11th to 20thNight
37%8%16%28%9%2
1980
21st to endNight
37%8%14%25%13%2
1980
October1st to 10thNight
43%7%15%24%11%1
2084
11th to 20thNight
43%7%15%26%9%1
2308
21st to endNight
47%9%15%21%7%1
2574
November1st to 10thNight
55%7%12%19%7%
2587
11th to 20thNight
53%8%13%18%7%1
2802
21st to endNight
51%8%16%17%6%1
2850
December1st to 10thNight
54%5%13%17%9%1
2850
11th to 20thNight
53%9%17%16%6%
3507
21st to endNight
37%7%16%20%16%3
5214

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
8%6%26%33%22%6%
180
11th to 20thDay
8%9%26%36%16%6%
180
21st to endDay
12%7%28%32%15%7%
198
February1st to 10thDay
11%12%25%33%14%5%
180
11th to 20thDay
13%228%34%18%5%
247
21st to endDay
7%429%33%18%8%
282
March1st to 10thDay
11%7%27%34%17%3
460
11th to 20thDay
10%426%35%18%7%
460
21st to endDay
14%5%25%32%20%4
491
April1st to 10thDay
10%12%27%36%11%4
420
11th to 20thDay
16%6%21%33%19%6%
412
21st to endDay
17%11%24%29%15%5%
420
May1st to 10thDay
13%10%23%33%17%5%
555
11th to 20thDay
10%6%21%36%20%7%
625
21st to endDay
16%6%20%30%20%7%
679
June1st to 10thDay
18%7%24%32%15%3
630
11th to 20thDay
19%7%22%26%20%6%
630
21st to endDay
12%5%19%30%25%9%
778
July1st to 10thDay
13%416%34%24%9%
621
11th to 20thDay
12%421%30%25%8%
618
21st to endDay
9%5%17%33%26%10%
684
August1st to 10thDay
11%420%31%21%13%
504
11th to 20thDay
9%5%21%32%26%7%
437
21st to endDay
12%6%18%29%26%9%
495
September1st to 10thDay
15%8%27%26%19%6%
450
11th to 20thDay
19%6%24%28%19%5%
450
21st to endDay
12%12%28%28%15%5%
450
October1st to 10thDay
16%6%26%29%18%5%
346
11th to 20thDay
13%7%31%31%13%4
270
21st to endDay
15%13%31%26%12%2
297
November1st to 10thDay
17%6%27%33%15%3
270
11th to 20thDay
14%6%30%34%13%2
201
21st to endDay
6%5%33%39%12%5%
180
December1st to 10thDay
9%5%26%36%20%4
180
11th to 20thDay
12%8%28%29%18%4
180
21st to endDay
9%419%41%23%5%
198
January1st to 10thNight
10%8%31%35%15%2
950
11th to 20thNight
11%8%32%35%13%2
950
21st to endNight
13%11%32%31%11%2
942
February1st to 10thNight
9%7%24%39%19%3
760
11th to 20thNight
11%6%32%36%15%1
744
21st to endNight
10%425%35%21%4
628
March1st to 10thNight
9%5%28%39%16%3
760
11th to 20thNight
11%430%36%15%3
760
21st to endNight
14%5%26%36%16%3
820
April1st to 10thNight
13%5%27%32%20%3
634
11th to 20thNight
15%6%27%36%14%2
533
21st to endNight
16%7%27%34%15%1
540
May1st to 10thNight
15%8%24%37%15%2
394
11th to 20thNight
11%6%25%39%17%2
354
21st to endNight
20%5%22%33%19%2
389
June1st to 10thNight
19%6%24%36%13%2
360
11th to 20thNight
19%6%23%31%18%2
360
21st to endNight
12%5%17%36%29%2
360
July1st to 10thNight
15%315%43%24%
350
11th to 20thNight
10%421%43%20%2
348
21st to endNight
12%415%42%23%3
394
August1st to 10thNight
13%416%32%29%4
358
11th to 20thNight
15%217%39%25%3
464
21st to endNight
12%319%40%25%1
594
September1st to 10thNight
15%318%41%22%2
583
11th to 20thNight
13%322%42%20%1
720
21st to endNight
11%428%40%15%1
720
October1st to 10thNight
15%427%38%15%1
720
11th to 20thNight
14%433%33%14%2
720
21st to endNight
13%7%31%35%14%1
792
November1st to 10thNight
19%6%30%35%9%1
922
11th to 20thNight
13%8%33%32%11%2
950
21st to endNight
9%5%36%37%11%2
950
December1st to 10thNight
15%7%30%30%14%3
950
11th to 20thNight
11%6%33%35%14%2
950
21st to endNight
10%5%29%36%18%3
1045
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