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 2017-09-21.

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
37%
15958
17%
46878
11%
15916
43%
15916
23%
31585

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
19%
900
13%
2506
4%
895
27%
895
16%
1853
January16th to endNight
20%
960
12%
2661
5%
960
26%
960
16%
2019
February1st to 15thNight
21%
770
13%
2181
3%
770
29%
770
18%
1580
February16th to endNight
24%
631
17%
1893
7%
631
33%
631
17%
1353
March1st to 15thNight
23%
720
13%
2160
8%
720
27%
720
17%
1554
March16th to endNight
28%
642
15%
2019
9%
642
35%
642
19%
1419
April1st to 15thNight
28%
539
15%
1797
10%
539
38%
539
20%
1196
April16th to endNight
32%
540
18%
1727
10%
540
41%
540
21%
1166
May1st to 15thNight
36%
540
15%
1620
8%
540
43%
540
22%
1119
May16th to endNight
49%
562
17%
1506
9%
561
54%
561
31%
988
June1st to 15thNight
50%
540
17%
1440
11%
540
55%
540
35%
905
June16th to endNight
49%
540
17%
1440
9%
540
54%
540
31%
949
July1st to 15thNight
62%
510
17%
1360
12%
510
65%
510
37%
828
July16th to endNight
70%
564
22%
1417
18%
531
72%
531
42%
842
August1st to 15thNight
76%
539
22%
1588
21%
536
77%
536
41%
889
August16th to endNight
66%
573
21%
1910
21%
573
71%
573
32%
1087
September1st to 15thNight
63%
557
28%
1817
28%
557
68%
557
35%
1008
September16th to endNight
59%
681
27%
1881
21%
681
63%
681
35%
1128
October1st to 15thNight
48%
660
27%
1878
20%
660
54%
660
32%
1154
October16th to endNight
28%
704
18%
2247
12%
704
36%
704
20%
1474
November1st to 15thNight
31%
700
23%
2276
15%
700
42%
700
24%
1404
November16th to endNight
26%
726
17%
2346
10%
726
35%
726
18%
1585
December1st to 15thNight
19%
900
12%
2520
4%
900
27%
900
16%
1881
December16th to endNight
15%
960
10%
2688
3%
960
22%
960
11%
2204

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
13%8%36%5%3445%7%36%
47987
Night
14%7%35%5%2445%6%39%
47046
Cloud CoverDay
13%7%36%5%3445%7%36%
47996
Night
14%7%35%5%24446%39%
47051
TransparencyDay
46%6%11%21%12%1
47673
Night
45%5%11%21%14%2
46878
SeeingDay
15%7%28%25%16%6%
5965
Night
18%8%29%29%12%1
15962

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%5%7%23%
1432
16th to endDay
13%16%8%8%5%34445%25%
1560
February1st to 15thDay
15%13%6%7%5%4435%6%26%
1678
16th to endDay
16%10%5%8%6%44345%30%
1580
March1st to 15thDay
16%12%5%8%5%3345%5%29%
1790
16th to endDay
18%9%37%6%2445%6%30%
2215
April1st to 15thDay
19%9%36%434346%32%
2151
16th to endDay
19%7%245%445%46%35%
2232
May1st to 15thDay
18%9%36%5%35%45%7%30%
2331
16th to endDay
12%5%25%5%36%45%7%39%
2606
June1st to 15thDay
11%435%43345%8%44%
2520
16th to endDay
10%5%25%5%36%6%7%9%37%
2520
July1st to 15thDay
8%425%5%45%5%6%9%43%
2520
16th to endDay
6%325%5%45%6%7%10%41%
2655
August1st to 15thDay
7%425%5%45%46%8%44%
2361
16th to endDay
9%426%6%35%5%6%8%42%
2292
September1st to 15thDay
12%41342445%7%47%
2130
16th to endDay
9%5%245%3445%9%43%
1872
October1st to 15thDay
13%6%3442445%6%43%
1749
16th to endDay
17%8%36%5%325%5%6%34%
1624
November1st to 15thDay
15%6%35%423347%43%
1582
16th to endDay
17%8%5%6%424346%35%
1611
December1st to 15thDay
18%12%49%6%25%445%26%
1440
16th to endDay
21%16%47%6%3344422%
1536
January1st to 15thNight
18%10%46%5%24345%32%
2506
16th to endNight
13%12%6%9%6%3445%5%28%
2661
February1st to 15thNight
16%12%46%5%24435%34%
2179
16th to endNight
17%10%5%7%5%24346%33%
1893
March1st to 15thNight
16%11%46%5%3434434%
2147
16th to endNight
15%7%36%5%345%5%6%34%
2019
April1st to 15thNight
16%7%36%434347%37%
1797
16th to endNight
18%7%26%433345%38%
1727
May1st to 15thNight
19%6%2442346%7%36%
1620
16th to endNight
11%4245%3348%7%43%
1504
June1st to 15thNight
10%5%25%423446%50%
1440
16th to endNight
9%5%25%6%25%45%9%42%
1440
July1st to 15thNight
6%32444436%9%50%
1440
16th to endNight
6%2135%2437%10%50%
1513
August1st to 15thNight
331343446%9%53%
1597
16th to endNight
9%313424449%51%
1910
September1st to 15thNight
11%31332245%6%54%
1817
16th to endNight
8%4245%25%45%7%49%
1881
October1st to 15thNight
12%424423336%51%
1878
16th to endNight
20%7%34412345%40%
2247
November1st to 15thNight
12%7%35%423346%45%
2276
16th to endNight
17%8%36%434346%37%
2346
December1st to 15thNight
20%10%47%5%24345%31%
2520
16th to endNight
22%14%5%8%6%3433421%
2688

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%14%47%6%35%5%5%6%24%
1432
16th to endDay
13%16%7%9%6%24445%25%
1560
February1st to 15thDay
15%13%7%7%5%3435%6%26%
1678
16th to endDay
15%10%5%8%6%44436%30%
1580
March1st to 15thDay
17%12%47%5%3445%6%28%
1800
16th to endDay
18%9%36%6%34447%30%
2214
April1st to 15thDay
19%10%36%5%24346%32%
2151
16th to endDay
19%7%245%44446%35%
2232
May1st to 15thDay
18%9%36%5%35%45%7%29%
2331
16th to endDay
12%5%35%6%25%5%5%7%39%
2606
June1st to 15thDay
10%425%5%2445%8%44%
2520
16th to endDay
9%5%25%5%36%7%6%9%37%
2520
July1st to 15thDay
7%425%5%36%5%5%9%43%
2520
16th to endDay
6%425%5%36%5%7%10%41%
2655
August1st to 15thDay
7%325%5%45%5%7%8%44%
2361
16th to endDay
9%326%5%35%5%6%8%42%
2292
September1st to 15thDay
13%41343445%7%47%
2130
16th to endDay
9%5%25%5%345%5%9%43%
1872
October1st to 15thDay
14%6%24424446%43%
1749
16th to endDay
18%8%36%5%3345%6%34%
1624
November1st to 15thDay
15%6%24423347%43%
1582
16th to endDay
17%8%46%5%34346%35%
1611
December1st to 15thDay
18%12%48%6%25%346%26%
1440
16th to endDay
21%16%5%8%6%2344422%
1536
January1st to 15thNight
18%10%47%6%24445%32%
2506
16th to endNight
14%12%7%9%6%34445%28%
2661
February1st to 15thNight
16%11%46%5%24445%34%
2172
16th to endNight
17%10%5%7%5%23346%33%
1893
March1st to 15thNight
17%11%46%5%3434434%
2160
16th to endNight
15%7%36%5%245%5%6%34%
2019
April1st to 15thNight
16%7%36%5%3435%7%37%
1797
16th to endNight
18%7%36%434345%38%
1727
May1st to 15thNight
19%7%25%42446%8%35%
1619
16th to endNight
11%4336%3348%7%43%
1504
June1st to 15thNight
10%425%5%23447%50%
1440
16th to endNight
9%435%6%25%5%6%9%42%
1440
July1st to 15thNight
6%314435%36%9%50%
1440
16th to endNight
5%3135%3437%10%50%
1513
August1st to 15thNight
3313435%45%9%53%
1597
16th to endNight
9%313424448%51%
1910
September1st to 15thNight
12%31332245%6%54%
1817
16th to endNight
8%4145%35%45%6%49%
1881
October1st to 15thNight
12%414423336%50%
1878
16th to endNight
20%7%35%422345%40%
2247
November1st to 15thNight
12%7%35%423346%44%
2276
16th to endNight
18%8%36%433336%37%
2346
December1st to 15thNight
20%10%37%5%24345%31%
2520
16th to endNight
22%15%5%8%6%3433421%
2688

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
59%6%12%12%8%
1433
16th to endDay
61%5%10%15%6%
1560
February1st to 15thDay
59%410%16%7%1
1680
16th to endDay
55%5%10%20%5%1
1580
March1st to 15thDay
56%6%11%18%7%
1800
16th to endDay
53%6%12%21%5%
2215
April1st to 15thDay
52%49%20%12%
2151
16th to endDay
48%6%12%17%10%4
2232
May1st to 15thDay
52%6%11%22%6%
2331
16th to endDay
42%7%10%20%15%2
2610
June1st to 15thDay
36%8%10%24%18%1
2520
16th to endDay
38%9%13%20%15%2
2520
July1st to 15thDay
37%7%11%24%16%2
2371
16th to endDay
34%9%16%23%13%2
2488
August1st to 15thDay
33%8%14%24%16%1
2346
16th to endDay
37%8%11%22%16%3
2292
September1st to 15thDay
35%6%11%24%18%3
2130
16th to endDay
35%6%10%27%18%1
1872
October1st to 15thDay
40%6%9%25%15%1
1749
16th to endDay
48%5%12%20%10%1
1624
November1st to 15thDay
40%411%23%17%2
1582
16th to endDay
50%412%23%9%
1611
December1st to 15thDay
59%5%10%17%6%
1440
16th to endDay
65%5%9%12%6%
1536
January1st to 15thNight
54%412%16%10%
2506
16th to endNight
57%413%15%8%
2661
February1st to 15thNight
52%5%11%19%9%1
2181
16th to endNight
52%5%11%20%9%1
1893
March1st to 15thNight
52%5%11%19%9%2
2160
16th to endNight
48%7%13%20%9%1
2019
April1st to 15thNight
46%5%10%21%14%1
1797
16th to endNight
46%6%8%20%13%4
1727
May1st to 15thNight
46%6%11%22%12%
1620
16th to endNight
36%7%13%19%18%3
1506
June1st to 15thNight
34%6%10%26%19%3
1440
16th to endNight
37%7%12%21%18%2
1440
July1st to 15thNight
30%7%12%26%18%3
1360
16th to endNight
26%7%16%27%17%4
1417
August1st to 15thNight
26%6%16%27%19%2
1588
16th to endNight
30%7%11%25%19%5%
1910
September1st to 15thNight
30%5%10%25%24%4
1817
16th to endNight
32%5%8%29%21%3
1881
October1st to 15thNight
34%5%9%26%22%1
1878
16th to endNight
45%411%23%13%1
2247
November1st to 15thNight
41%38%24%18%4
2276
16th to endNight
48%412%22%11%
2346
December1st to 15thNight
56%410%18%9%
2520
16th to endNight
67%48%13%5%1
2688

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
25%11%33%21%8%
90
16th to endDay
15%16%35%25%6%1
96
February1st to 15thDay
18%18%47%12%2
90
16th to endDay
17%14%38%16%12%1
81
March1st to 15thDay
33%17%28%15%4
90
16th to endDay
27%14%29%18%9%1
255
April1st to 15thDay
24%12%29%20%10%1
270
16th to endDay
22%10%31%21%8%5%
270
May1st to 15thDay
23%9%30%20%12%3
288
16th to endDay
16%7%33%25%12%4
506
June1st to 15thDay
11%430%30%16%5%
495
16th to endDay
13%7%34%27%13%4
495
July1st to 15thDay
10%428%27%17%11%
475
16th to endDay
7%226%30%22%10%
515
August1st to 15thDay
8%115%33%23%17%
376
16th to endDay
8%219%30%24%14%
332
September1st to 15thDay
12%316%30%28%8%
315
16th to endDay
9%417%30%28%9%
275
October1st to 15thDay
15%426%29%16%6%
189
16th to endDay
23%8%43%20%3
96
November1st to 15thDay
8%10%25%28%18%7%
90
16th to endDay
35%12%31%15%5%
90
December1st to 15thDay
18%18%37%17%5%1
90
16th to endDay
30%21%41%33
96
January1st to 15thNight
23%14%37%20%4
900
16th to endNight
20%13%35%26%3
960
February1st to 15thNight
22%12%38%22%4
773
16th to endNight
22%12%34%25%4
631
March1st to 15thNight
24%12%35%21%6%
720
16th to endNight
18%10%37%23%9%
642
April1st to 15thNight
20%11%35%25%6%
539
16th to endNight
21%9%31%26%9%
540
May1st to 15thNight
22%431%28%11%
540
16th to endNight
12%227%38%17%
563
June1st to 15thNight
11%227%43%14%
540
16th to endNight
9%329%36%20%
540
July1st to 15thNight
9%121%42%23%1
510
16th to endNight
5%116%43%30%3
564
August1st to 15thNight
5%10%47%31%5%
539
16th to endNight
10%115%36%31%4
573
September1st to 15thNight
13%313%37%27%4
557
16th to endNight
9%418%34%28%3
681
October1st to 15thNight
15%6%23%33%18%1
660
16th to endNight
24%11%32%22%8%
704
November1st to 15thNight
16%12%36%23%10%1
700
16th to endNight
22%12%32%23%8%
726
December1st to 15thNight
27%13%32%21%4
900
16th to endNight
30%11%33%21%2
960
Page generated at 2017-09-22 06:35:37. Version ac04

Copyright 2017 A. Danko


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