Our Prairie Sky
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Our Prairie Sky clear sky chart from 2005-11-05 to 2019-06-10.

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
36%
18328
17%
53857
11%
18286
43%
18286
23%
36422

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
21%
1050
14%
2926
4%
1045
29%
1045
17%
2148
January16th to endNight
20%
1120
12%
3105
4%
1120
26%
1120
16%
2365
February1st to 15thNight
20%
902
13%
2553
4%
902
28%
902
17%
1887
February16th to endNight
22%
735
16%
2205
7%
735
31%
735
16%
1600
March1st to 15thNight
23%
840
15%
2520
8%
840
29%
840
18%
1776
March16th to endNight
28%
750
16%
2357
10%
750
36%
750
19%
1641
April1st to 15thNight
27%
629
16%
2097
10%
629
37%
629
19%
1414
April16th to endNight
33%
624
17%
1993
10%
624
41%
624
20%
1356
May1st to 15thNight
37%
630
15%
1890
9%
630
44%
630
21%
1310
May16th to endNight
49%
658
16%
1764
9%
657
54%
657
30%
1165
June1st to 15thNight
51%
612
18%
1632
11%
612
56%
612
34%
1031
June16th to endNight
50%
585
16%
1560
9%
585
55%
585
30%
1033
July1st to 15thNight
65%
555
18%
1480
14%
555
67%
555
39%
887
July16th to endNight
69%
612
22%
1545
18%
579
72%
579
43%
913
August1st to 15thNight
76%
575
22%
1692
22%
572
76%
572
40%
950
August16th to endNight
65%
621
20%
2070
20%
621
69%
621
32%
1180
September1st to 15thNight
64%
603
29%
1968
29%
603
68%
603
35%
1092
September16th to endNight
59%
777
28%
2145
22%
777
63%
777
36%
1286
October1st to 15thNight
45%
780
24%
2220
18%
780
51%
780
29%
1421
October16th to endNight
29%
832
19%
2655
13%
832
38%
832
22%
1712
November1st to 15thNight
29%
820
23%
2666
14%
820
41%
820
22%
1705
November16th to endNight
26%
848
18%
2738
9%
848
36%
848
19%
1841
December1st to 15thNight
20%
1050
13%
2940
4%
1050
29%
1050
17%
2170
December16th to endNight
16%
1120
11%
3136
3%
1120
23%
1120
12%
2539

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%8%36%5%3445%7%36%
54658
Night
14%8%36%5%34446%39%
54025
Cloud CoverDay
14%8%36%5%3445%7%36%
54667
Night
14%8%36%5%34446%39%
54030
TransparencyDay
46%6%11%20%12%1
54344
Night
45%5%11%21%14%2
53857
SeeingDay
17%7%28%25%14%6%
8232
Night
18%8%29%29%12%1
18332

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 15thDay
16%14%47%6%345%46%25%
1672
16th to endDay
13%16%7%8%5%3445%5%26%
1820
February1st to 15thDay
17%13%6%7%5%4435%6%24%
1966
16th to endDay
17%11%6%8%6%33345%28%
1840
March1st to 15thDay
16%13%5%7%5%34445%29%
2090
16th to endDay
18%9%37%6%2445%6%30%
2583
April1st to 15thDay
19%10%36%43435%6%31%
2511
16th to endDay
19%7%245%445%46%36%
2571
May1st to 15thDay
18%9%36%5%35%45%7%30%
2721
16th to endDay
13%5%25%5%35%45%8%38%
3052
June1st to 15thDay
11%435%43345%8%44%
2857
16th to endDay
10%5%25%5%36%6%6%9%37%
2730
July1st to 15thDay
7%425%435%5%6%9%45%
2730
16th to endDay
6%325%5%45%6%7%9%41%
2879
August1st to 15thDay
6%425%5%45%46%8%45%
2510
16th to endDay
9%426%6%35%5%6%8%42%
2484
September1st to 15thDay
13%5%1342445%7%47%
2308
16th to endDay
8%5%244345%5%8%45%
2145
October1st to 15thDay
16%6%25%43445%6%40%
2067
16th to endDay
17%8%36%5%3245%6%36%
1919
November1st to 15thDay
17%7%34423447%40%
1852
16th to endDay
17%8%46%5%24346%36%
1879
December1st to 15thDay
17%12%49%6%35%445%27%
1680
16th to endDay
20%15%47%6%23445%23%
1792
January1st to 15thNight
17%10%46%6%23335%33%
2926
16th to endNight
13%12%6%9%6%34445%28%
3105
February1st to 15thNight
17%12%46%5%24335%32%
2551
16th to endNight
18%10%5%7%5%33346%31%
2205
March1st to 15thNight
15%11%46%5%34345%36%
2507
16th to endNight
16%7%36%5%345%5%6%34%
2357
April1st to 15thNight
17%7%36%434347%36%
2097
16th to endNight
17%7%26%443345%37%
1993
May1st to 15thNight
18%6%35%43446%7%35%
1890
16th to endNight
11%4245%3448%7%42%
1762
June1st to 15thNight
10%425%5%23446%49%
1632
16th to endNight
10%5%25%6%25%45%9%41%
1560
July1st to 15thNight
6%31444436%9%51%
1560
16th to endNight
6%2135%2437%10%51%
1641
August1st to 15thNight
33145%3446%8%53%
1701
16th to endNight
8%313434448%51%
2070
September1st to 15thNight
12%31332235%6%54%
1968
16th to endNight
7%4245%25%45%7%50%
2145
October1st to 15thNight
14%4245%24335%48%
2220
16th to endNight
19%7%24412345%42%
2655
November1st to 15thNight
14%8%35%5%23345%42%
2666
16th to endNight
17%8%36%433346%37%
2738
December1st to 15thNight
18%11%47%5%24345%32%
2940
16th to endNight
21%14%5%8%6%3434422%
3136

Percentage Cloud Cover SE (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
16%15%48%6%345%5%6%25%
1672
16th to endDay
13%15%7%9%5%24445%26%
1820
February1st to 15thDay
17%13%6%7%6%3435%6%24%
1966
16th to endDay
16%11%6%8%6%34435%28%
1840
March1st to 15thDay
16%12%48%5%34445%28%
2100
16th to endDay
18%9%37%6%3445%6%30%
2582
April1st to 15thDay
19%10%36%5%34346%31%
2511
16th to endDay
19%7%24444446%35%
2571
May1st to 15thDay
17%9%36%6%35%45%7%29%
2721
16th to endDay
13%5%35%6%25%45%8%38%
3052
June1st to 15thDay
11%425%5%2445%8%44%
2857
16th to endDay
10%5%25%5%35%7%6%9%37%
2730
July1st to 15thDay
7%4245%36%5%5%9%45%
2730
16th to endDay
6%425%5%36%5%7%10%41%
2879
August1st to 15thDay
6%325%5%45%5%7%8%45%
2510
16th to endDay
9%426%5%35%5%5%8%42%
2484
September1st to 15thDay
13%41343445%7%47%
2308
16th to endDay
8%5%245%245%5%9%45%
2145
October1st to 15thDay
16%6%25%434446%40%
2067
16th to endDay
17%8%36%5%3245%6%36%
1919
November1st to 15thDay
17%7%25%424346%40%
1852
16th to endDay
17%8%46%5%24346%36%
1879
December1st to 15thDay
17%12%5%8%6%25%446%27%
1680
16th to endDay
20%15%5%8%5%33445%23%
1792
January1st to 15thNight
17%10%47%6%24445%33%
2926
16th to endNight
13%11%6%9%6%34445%28%
3105
February1st to 15thNight
17%12%46%5%24345%32%
2544
16th to endNight
18%10%5%7%5%23346%31%
2205
March1st to 15thNight
15%11%46%5%34345%35%
2520
16th to endNight
16%7%36%5%245%5%6%34%
2357
April1st to 15thNight
17%7%36%43435%7%36%
2097
16th to endNight
17%7%26%5%34345%37%
1993
May1st to 15thNight
18%7%25%43445%8%35%
1889
16th to endNight
10%4346%3448%7%42%
1762
June1st to 15thNight
10%425%5%235%47%49%
1632
16th to endNight
9%5%25%6%35%46%9%41%
1560
July1st to 15thNight
6%214435%36%10%51%
1560
16th to endNight
5%3135%3447%10%51%
1641
August1st to 15thNight
3323435%45%9%53%
1701
16th to endNight
8%413424448%51%
2070
September1st to 15thNight
12%31332235%6%54%
1968
16th to endNight
7%4145%25%45%7%50%
2145
October1st to 15thNight
13%5%25%5%23336%47%
2220
16th to endNight
19%7%25%422345%42%
2655
November1st to 15thNight
14%8%35%423345%42%
2666
16th to endNight
17%8%36%433336%37%
2738
December1st to 15thNight
19%10%37%5%24345%32%
2940
16th to endNight
21%14%5%8%6%3433423%
3136

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
58%6%11%13%8%1
1673
16th to endDay
60%5%11%14%7%
1820
February1st to 15thDay
61%49%15%7%1
1968
16th to endDay
57%5%9%19%5%1
1840
March1st to 15thDay
56%5%10%18%7%
2100
16th to endDay
53%5%11%21%6%
2583
April1st to 15thDay
53%49%19%11%
2511
16th to endDay
48%6%12%16%11%4
2571
May1st to 15thDay
52%7%11%21%7%
2721
16th to endDay
43%7%10%22%14%2
3056
June1st to 15thDay
36%8%10%25%17%1
2857
16th to endDay
38%9%13%21%14%1
2730
July1st to 15thDay
35%7%11%24%16%4
2581
16th to endDay
34%9%15%23%13%2
2712
August1st to 15thDay
33%8%14%24%16%1
2495
16th to endDay
38%8%11%22%16%3
2484
September1st to 15thDay
35%6%11%23%18%5%
2308
16th to endDay
34%6%10%26%20%1
2145
October1st to 15thDay
44%6%9%23%13%2
2067
16th to endDay
48%5%12%20%12%1
1919
November1st to 15thDay
43%412%21%15%2
1852
16th to endDay
50%411%23%9%
1879
December1st to 15thDay
58%5%10%17%7%
1680
16th to endDay
63%5%11%12%6%
1792
January1st to 15thNight
54%411%17%11%1
2926
16th to endNight
57%412%15%8%
3105
February1st to 15thNight
55%410%18%9%1
2553
16th to endNight
54%410%19%9%1
2205
March1st to 15thNight
51%5%10%20%10%1
2520
16th to endNight
48%6%12%20%11%1
2357
April1st to 15thNight
47%5%10%21%13%1
2097
16th to endNight
47%6%8%18%14%4
1993
May1st to 15thNight
46%6%12%22%11%
1890
16th to endNight
37%7%14%19%16%3
1764
June1st to 15thNight
34%6%11%25%19%2
1632
16th to endNight
38%7%12%22%16%2
1560
July1st to 15thNight
28%7%12%26%18%4
1480
16th to endNight
26%7%16%27%17%4
1545
August1st to 15thNight
26%6%16%27%20%2
1692
16th to endNight
30%7%11%25%19%4
2070
September1st to 15thNight
30%411%24%23%5%
1968
16th to endNight
31%5%8%28%22%3
2145
October1st to 15thNight
38%6%8%25%19%2
2220
16th to endNight
44%410%23%15%1
2655
November1st to 15thNight
44%48%22%16%3
2666
16th to endNight
48%412%22%10%
2738
December1st to 15thNight
55%410%19%10%
2940
16th to endNight
65%48%14%6%
3136

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
26%11%32%21%7%
180
16th to endDay
19%15%36%23%5%
192
February1st to 15thDay
29%17%38%13%1
180
16th to endDay
27%13%38%13%6%
159
March1st to 15thDay
30%14%31%19%3
180
16th to endDay
27%11%30%19%9%2
377
April1st to 15thDay
26%12%29%20%9%1
390
16th to endDay
22%11%30%18%11%5%
379
May1st to 15thDay
21%10%28%21%13%4
408
16th to endDay
17%7%32%23%12%6%
664
June1st to 15thDay
12%430%30%16%5%
616
16th to endDay
14%6%31%27%14%4
570
July1st to 15thDay
9%425%26%20%14%
550
16th to endDay
7%225%32%22%9%
595
August1st to 15thDay
8%115%33%24%16%
426
16th to endDay
10%218%30%23%13%
396
September1st to 15thDay
13%316%28%26%11%
375
16th to endDay
7%5%20%30%26%10%
374
October1st to 15thDay
21%5%28%27%13%4
297
16th to endDay
23%10%36%22%5%
192
November1st to 15thDay
21%10%27%21%13%6%
180
16th to endDay
25%11%36%21%5%
180
December1st to 15thDay
20%17%34%17%8%1
180
16th to endDay
23%17%46%9%3
192
January1st to 15thNight
23%13%36%21%5%
1050
16th to endNight
19%13%37%26%2
1120
February1st to 15thNight
25%11%36%22%3
905
16th to endNight
24%12%33%24%4
735
March1st to 15thNight
23%11%36%22%5%
840
16th to endNight
19%9%36%23%9%
750
April1st to 15thNight
21%11%35%24%6%
629
16th to endNight
20%10%30%26%10%
624
May1st to 15thNight
21%431%29%11%
630
16th to endNight
13%226%37%18%1
659
June1st to 15thNight
11%226%43%14%
612
16th to endNight
10%228%37%20%1
585
July1st to 15thNight
8%119%41%26%2
555
16th to endNight
5%116%43%29%3
612
August1st to 15thNight
5%10%47%31%4
575
16th to endNight
9%116%36%31%4
621
September1st to 15thNight
13%313%35%27%5%
603
16th to endNight
8%5%19%34%28%3
777
October1st to 15thNight
17%7%24%33%16%1
780
16th to endNight
22%11%32%23%8%
832
November1st to 15thNight
19%11%35%23%9%1
820
16th to endNight
22%12%33%24%7%
848
December1st to 15thNight
25%13%33%22%4
1050
16th to endNight
28%12%33%22%2
1120
Page generated at 2019-06-10 18:29:50. Version ac04

Copyright 2019 A. Danko


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