Atikokan
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Atikokan clear sky chart from 2005-11-06 to 2024-09-29.

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
29%
25814
10%
95078
6%
25581
34%
25581
13%
68765

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
22%
943
8%
4712
4%
926
28%
926
7%
3613
January11th to 20thNight
20%
944
5%
4493
4%
930
24%
930
6%
3733
January21st to endNight
16%
1036
5%
4877
3%
1023
22%
1023
6%
4032
February1st to 10thNight
24%
950
10%
2475
3%
950
29%
950
15%
1930
February11th to 20thNight
30%
929
15%
2404
7%
925
35%
925
20%
1769
February21st to endNight
26%
711
12%
1967
5%
711
32%
711
14%
1512
March1st to 10thNight
24%
754
20%
3716
8%
742
30%
742
11%
2343
March11th to 20thNight
25%
563
12%
3472
9%
550
38%
550
9%
2401
March21st to endNight
31%
621
10%
3573
13%
605
40%
605
9%
2521
April1st to 10thNight
28%
570
14%
1900
10%
570
37%
570
17%
1323
April11th to 20thNight
28%
563
13%
1859
8%
563
36%
563
17%
1315
April21st to endNight
34%
570
13%
1610
7%
570
38%
570
20%
1153
May1st to 10thNight
29%
569
17%
2475
6%
559
34%
559
14%
1536
May11th to 20thNight
35%
555
11%
2471
6%
541
40%
541
16%
1528
May21st to endNight
38%
608
8%
2719
5%
593
42%
593
16%
1754
June1st to 10thNight
40%
570
7%
1421
3%
570
42%
570
27%
996
June11th to 20thNight
40%
570
8%
1330
3%
570
44%
570
32%
912
June21st to endNight
46%
570
7%
1330
5%
570
47%
570
28%
950
July1st to 10thNight
52%
541
6%
2116
7%
535
54%
535
27%
1241
July11th to 20thNight
45%
540
9%
2061
5%
533
49%
533
25%
1181
July21st to endNight
51%
614
10%
2338
7%
569
53%
569
23%
1416
August1st to 10thNight
49%
559
16%
2325
9%
545
54%
545
23%
1397
August11th to 20thNight
49%
551
12%
2521
11%
543
55%
543
19%
1416
August21st to endNight
44%
619
11%
3149
13%
605
49%
605
17%
1823
September1st to 10thNight
45%
570
18%
1900
16%
570
52%
570
26%
1166
September11th to 20thNight
41%
570
15%
1900
12%
570
47%
570
23%
1223
September21st to endNight
32%
704
16%
2141
12%
704
37%
704
19%
1491
October1st to 10thNight
27%
720
13%
2160
7%
720
32%
720
17%
1601
October11th to 20thNight
24%
720
13%
2160
6%
720
29%
720
15%
1604
October21st to endNight
21%
792
9%
2550
4%
792
26%
792
11%
2003
November1st to 10thNight
21%
882
10%
2548
5%
882
25%
882
12%
2012
November11th to 20thNight
16%
950
7%
2660
3%
950
20%
950
8%
2258
November21st to endNight
14%
950
6%
2660
2%
950
17%
950
8%
2271
December1st to 10thNight
17%
950
6%
2660
2%
950
20%
950
7%
2294
December11th to 20thNight
16%
949
8%
3260
3%
949
20%
949
6%
2628
December21st to endNight
13%
1037
4%
5165
2%
1026
17%
1026
3%
4419

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
14%11%49%5%5%5%45%7%32%
101547
Night
14%12%410%6%5%5%45%6%29%
96824
TransparencyDay
51%6%13%21%8%1
101294
Night
55%6%12%19%7%1
96695
SeeingDay
20%14%33%21%9%2
16097
Night
19%11%32%27%10%1
25945

By Month

Percentage Cloud Cover NE (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
7%16%7%16%11%7%6%45%5%16%
2218
11th to 20thDay
6%11%5%15%8%7%10%6%7%5%17%
2465
21st to endDay
9%17%13%20%8%6%5%45%49%
2783
February1st to 10thDay
8%12%5%12%7%7%9%7%7%6%21%
1703
11th to 20thDay
8%11%413%9%6%446%6%28%
1664
21st to endDay
7%13%6%11%8%5%446%6%29%
1486
March1st to 10thDay
10%12%38%5%4435%6%41%
3148
11th to 20thDay
7%13%8%13%6%5%4346%31%
3480
21st to endDay
15%16%5%11%5%4334430%
3995
April1st to 10thDay
14%13%39%7%45%45%7%30%
2280
11th to 20thDay
18%12%37%44345%6%33%
2267
21st to endDay
17%13%48%5%5%4345%33%
2570
May1st to 10thDay
18%11%37%5%4435%7%33%
4428
11th to 20thDay
16%9%37%5%5%445%8%34%
4399
21st to endDay
21%7%36%44435%6%37%
4837
June1st to 10thDay
17%7%26%4445%6%8%36%
2755
11th to 20thDay
17%7%37%5%45%45%7%36%
2850
21st to endDay
18%6%26%5%5%5%47%9%33%
2850
July1st to 10thDay
10%6%27%5%5%5%5%8%9%39%
4750
11th to 20thDay
11%425%44446%10%46%
4611
21st to endDay
12%7%27%5%5%446%8%39%
4814
August1st to 10thDay
14%6%28%6%5%6%47%8%33%
4423
11th to 20thDay
14%5%1434447%10%44%
4101
21st to endDay
15%7%36%445%46%9%38%
4322
September1st to 10thDay
15%7%37%44435%8%40%
2280
11th to 20thDay
17%9%37%5%4446%8%34%
2280
21st to endDay
22%9%28%44435%7%31%
1984
October1st to 10thDay
18%14%39%5%45%35%7%27%
1800
11th to 20thDay
19%17%5%10%5%45%346%22%
1800
21st to endDay
20%21%49%44324424%
1805
November1st to 10thDay
16%21%6%10%5%5%5%345%21%
1528
11th to 20thDay
15%19%7%16%7%5%423418%
1520
21st to endDay
16%17%6%18%7%5%3345%16%
1520
December1st to 10thDay
9%17%5%18%10%7%6%46%414%
1520
11th to 20thDay
12%18%7%13%7%5%5%445%20%
1869
21st to endDay
21%23%7%11%7%4323415%
2442
January1st to 10thNight
7%17%6%15%9%6%5%46%6%19%
4737
11th to 20thNight
7%11%5%16%12%11%10%6%4415%
4502
21st to endNight
9%18%13%18%6%45%445%14%
4884
February1st to 10thNight
8%12%6%11%7%7%9%47%7%23%
2475
11th to 20thNight
8%11%311%7%5%7%5%6%6%30%
2403
21st to endNight
5%15%6%12%9%7%6%45%5%26%
1967
March1st to 10thNight
11%12%39%6%5%5%346%35%
3722
11th to 20thNight
9%13%5%12%8%6%5%446%28%
3479
21st to endNight
19%14%410%5%4335%6%26%
3636
April1st to 10thNight
16%13%38%444446%33%
1900
11th to 20thNight
16%14%48%5%4435%7%31%
1859
21st to endNight
19%12%37%5%45%45%5%32%
1610
May1st to 10thNight
18%9%36%34435%6%38%
2523
11th to 20thNight
13%8%37%5%5%445%7%38%
2506
21st to endNight
23%7%25%434445%40%
2750
June1st to 10thNight
18%6%26%5%4445%7%39%
1421
11th to 20thNight
13%426%5%445%7%8%42%
1330
21st to endNight
14%5%26%5%5%5%5%6%7%41%
1330
July1st to 10thNight
11%6%25%44447%9%44%
2220
11th to 20thNight
8%415%4445%7%10%48%
2344
21st to endNight
11%6%26%34345%7%49%
2750
August1st to 10thNight
15%6%25%34446%10%43%
2517
11th to 20thNight
11%425%435%45%9%47%
2734
21st to endNight
17%5%25%44435%7%44%
3338
September1st to 10thNight
12%6%26%5%4435%7%45%
1900
11th to 20thNight
16%7%36%34345%5%44%
1900
21st to endNight
22%10%35%43425%7%36%
2141
October1st to 10thNight
20%12%36%45%435%7%32%
2160
11th to 20thNight
19%15%47%5%35%346%29%
2160
21st to endNight
19%15%411%5%4336%6%23%
2550
November1st to 10thNight
16%17%412%6%4435%5%24%
2548
11th to 20thNight
16%17%6%16%7%5%434417%
2660
21st to endNight
13%17%8%15%9%5%434417%
2660
December1st to 10thNight
9%16%6%17%10%8%6%45%5%15%
2660
11th to 20thNight
11%16%6%14%8%6%5%5%6%6%17%
3323
21st to endNight
21%22%7%13%6%4433313%
5225

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
68%5%7%13%6%
2219
11th to 20thDay
65%5%9%19%3
2465
21st to endDay
78%45%9%4
2783
February1st to 10thDay
59%5%10%15%9%1
1703
11th to 20thDay
55%410%20%9%1
1673
21st to endDay
54%412%16%12%1
1486
March1st to 10thDay
43%5%11%23%16%1
3150
11th to 20thDay
53%6%12%21%8%
3480
21st to endDay
57%5%8%15%13%1
3995
April1st to 10thDay
54%5%8%18%14%2
2280
11th to 20thDay
51%5%11%20%12%1
2267
21st to endDay
54%5%8%19%13%1
2570
May1st to 10thDay
47%7%13%22%11%1
4440
11th to 20thDay
46%8%13%22%11%1
4403
21st to endDay
45%8%11%21%14%1
4837
June1st to 10thDay
43%7%15%24%10%1
2755
11th to 20thDay
46%6%12%23%13%1
2850
21st to endDay
45%8%16%24%7%
2850
July1st to 10thDay
38%7%18%28%8%
4676
11th to 20thDay
32%6%22%34%6%
4530
21st to endDay
42%6%15%30%6%
4662
August1st to 10thDay
46%6%15%24%8%1
4408
11th to 20thDay
34%6%23%33%4
4142
21st to endDay
42%5%20%27%6%
4321
September1st to 10thDay
42%7%16%27%8%
2280
11th to 20thDay
46%8%21%21%4
2280
21st to endDay
51%7%14%22%5%
1984
October1st to 10thDay
56%8%13%19%4
1800
11th to 20thDay
62%6%12%16%4
1800
21st to endDay
64%5%11%17%3
1805
November1st to 10thDay
65%6%12%11%41
1528
11th to 20thDay
72%48%12%4
1520
21st to endDay
73%6%10%7%4
1520
December1st to 10thDay
72%7%8%11%3
1520
11th to 20thDay
67%5%10%11%6%1
1870
21st to endDay
75%35%13%4
2442
January1st to 10thNight
65%5%11%15%4
4737
11th to 20thNight
71%6%9%11%3
4502
21st to endNight
72%5%9%10%4
4884
February1st to 10thNight
59%5%11%15%9%
2475
11th to 20thNight
52%5%14%18%10%1
2404
21st to endNight
59%5%10%16%9%2
1967
March1st to 10thNight
50%5%12%17%15%1
3733
11th to 20thNight
56%5%13%16%7%1
3480
21st to endNight
56%6%10%17%10%2
3636
April1st to 10thNight
50%6%10%18%15%1
1900
11th to 20thNight
53%5%10%18%12%2
1859
21st to endNight
51%5%10%20%13%1
1610
May1st to 10thNight
44%7%11%25%13%
2530
11th to 20thNight
42%8%14%24%10%2
2507
21st to endNight
46%7%11%22%12%2
2751
June1st to 10thNight
44%7%14%24%11%
1421
11th to 20thNight
37%8%11%24%19%1
1330
21st to endNight
40%10%15%25%9%1
1330
July1st to 10thNight
34%7%22%27%9%
2185
11th to 20thNight
29%8%20%33%10%
2302
21st to endNight
34%6%15%36%8%1
2662
August1st to 10thNight
37%6%18%29%10%1
2508
11th to 20thNight
34%6%19%34%6%
2759
21st to endNight
39%5%21%28%7%
3338
September1st to 10thNight
37%7%15%31%9%
1900
11th to 20thNight
41%8%20%27%5%
1900
21st to endNight
48%6%12%27%6%
2141
October1st to 10thNight
53%7%11%23%6%
2160
11th to 20thNight
56%5%13%21%3
2160
21st to endNight
61%7%13%14%4
2550
November1st to 10thNight
62%6%12%15%5%
2548
11th to 20thNight
71%5%9%10%4
2660
21st to endNight
71%6%10%10%3
2660
December1st to 10thNight
72%7%8%10%3
2660
11th to 20thNight
66%7%11%12%4
3321
21st to endNight
77%45%10%3
5225

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
15%14%41%21%9%
270
11th to 20thDay
17%10%41%25%7%1
270
21st to endDay
15%11%42%26%6%
297
February1st to 10thDay
16%17%46%14%6%1
270
11th to 20thDay
19%19%39%16%5%3
270
21st to endDay
16%23%44%13%4
225
March1st to 10thDay
12%15%41%25%6%
270
11th to 20thDay
11%23%41%17%5%3
270
21st to endDay
18%18%34%19%9%2
401
April1st to 10thDay
22%16%34%18%9%1
460
11th to 20thDay
26%14%28%21%9%1
465
21st to endDay
26%15%29%21%8%2
650
May1st to 10thDay
25%18%31%19%5%2
653
11th to 20thDay
21%14%33%20%9%3
675
21st to endDay
24%12%30%25%7%2
734
June1st to 10thDay
21%14%30%23%10%3
680
11th to 20thDay
18%18%34%20%7%3
680
21st to endDay
21%10%29%24%11%4
680
July1st to 10thDay
11%10%33%26%14%6%
671
11th to 20thDay
16%11%29%25%15%5%
668
21st to endDay
12%9%31%25%17%6%
739
August1st to 10thDay
14%9%32%27%15%3
676
11th to 20thDay
18%8%24%28%17%5%
665
21st to endDay
20%9%30%24%15%2
629
September1st to 10thDay
16%14%31%25%13%2
490
11th to 20thDay
22%13%30%22%11%2
490
21st to endDay
29%16%28%17%10%
365
October1st to 10thDay
23%19%30%18%9%2
270
11th to 20thDay
24%19%34%18%4
270
21st to endDay
37%20%31%9%21
297
November1st to 10thDay
26%17%35%16%6%
270
11th to 20thDay
24%21%36%16%3
270
21st to endDay
27%20%36%13%31
270
December1st to 10thDay
16%19%44%16%4
270
11th to 20thDay
21%16%41%17%4
270
21st to endDay
22%15%37%21%32
297
January1st to 10thNight
16%13%38%25%8%1
950
11th to 20thNight
18%12%38%24%7%1
950
21st to endNight
17%11%38%26%7%
1045
February1st to 10thNight
14%13%36%26%9%1
950
11th to 20thNight
14%14%33%27%9%2
929
21st to endNight
13%15%35%26%10%1
711
March1st to 10thNight
16%14%35%26%9%
760
11th to 20thNight
17%15%35%22%9%1
570
21st to endNight
22%11%28%26%10%3
627
April1st to 10thNight
20%13%34%26%7%
570
11th to 20thNight
21%12%32%24%10%
563
21st to endNight
23%8%28%29%10%1
570
May1st to 10thNight
22%10%33%27%7%1
570
11th to 20thNight
20%12%30%24%12%1
561
21st to endNight
21%8%27%32%11%
617
June1st to 10thNight
21%7%29%29%14%
570
11th to 20thNight
16%6%33%35%11%
570
21st to endNight
16%6%25%36%16%1
570
July1st to 10thNight
10%6%28%37%18%1
555
11th to 20thNight
11%6%31%30%20%2
552
21st to endNight
9%6%26%36%21%2
624
August1st to 10thNight
11%429%38%17%1
567
11th to 20thNight
14%8%22%31%23%3
564
21st to endNight
19%7%25%32%16%1
627
September1st to 10thNight
15%7%27%33%18%1
570
11th to 20thNight
20%7%28%27%16%1
570
21st to endNight
28%10%26%25%9%2
704
October1st to 10thNight
27%11%30%23%9%1
720
11th to 20thNight
28%13%29%23%6%1
720
21st to endNight
28%13%30%24%6%
792
November1st to 10thNight
26%12%31%24%6%1
882
11th to 20thNight
26%14%32%20%7%1
950
21st to endNight
24%17%37%19%4
950
December1st to 10thNight
18%13%38%23%6%1
950
11th to 20thNight
21%14%36%22%7%1
950
21st to endNight
26%12%31%22%7%1
1045
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