Petawawa
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Petawawa clear sky chart from 2005-11-05 to 2017-11-30.

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
32%
14917
12%
47805
8%
14888
37%
14888
16%
34734

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
17%
720
5%
2506
3%
716
21%
716
6%
2092
January16th to endNight
26%
768
10%
2604
6%
768
33%
768
11%
1992
February1st to 15thNight
20%
702
9%
2287
5%
701
26%
701
11%
1813
February16th to endNight
22%
631
12%
1997
5%
631
31%
631
12%
1520
March1st to 15thNight
22%
720
12%
2051
7%
720
28%
720
14%
1595
March16th to endNight
34%
768
19%
2070
10%
768
40%
768
23%
1426
April1st to 15thNight
28%
718
14%
1796
5%
718
33%
718
20%
1346
April16th to endNight
33%
613
17%
1693
9%
613
39%
613
22%
1203
May1st to 15thNight
33%
363
16%
1443
16%
363
40%
363
17%
950
May16th to endNight
39%
374
13%
1497
11%
374
48%
374
17%
949
June1st to 15thNight
38%
360
8%
1440
6%
360
45%
360
17%
947
June16th to endNight
45%
360
9%
1440
12%
360
50%
360
18%
927
July1st to 15thNight
53%
340
14%
1360
20%
340
58%
340
25%
770
July16th to endNight
57%
376
13%
1418
15%
354
62%
354
25%
814
August1st to 15thNight
57%
488
14%
1559
12%
486
61%
486
25%
986
August16th to endNight
56%
663
19%
1809
12%
663
60%
663
33%
1134
September1st to 15thNight
45%
720
15%
1800
7%
720
47%
720
28%
1252
September16th to endNight
49%
717
20%
1979
14%
717
53%
717
30%
1285
October1st to 15thNight
32%
720
16%
2160
11%
720
39%
720
20%
1528
October16th to endNight
25%
768
11%
2364
6%
768
33%
768
12%
1851
November1st to 15thNight
30%
760
14%
2596
11%
760
36%
760
14%
1894
November16th to endNight
22%
780
8%
2728
6%
780
25%
780
8%
2158
December1st to 15thNight
16%
720
6%
2520
3%
720
21%
720
7%
2077
December16th to endNight
17%
768
7%
2688
4%
768
21%
768
7%
2225

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
18%9%46%5%35%45%6%31%
48610
Night
17%10%46%5%34445%31%
47975
TransparencyDay
52%6%11%18%9%1
48298
Night
53%6%11%18%9%
47805
SeeingDay
22%10%27%22%12%4
5617
Night
22%9%27%27%11%
14920

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
22%15%6%10%6%3233421%
1432
16th to endDay
14%16%5%8%7%45%435%23%
1617
February1st to 15thDay
11%15%6%12%7%46%445%19%
1575
16th to endDay
16%15%6%8%5%44446%23%
1476
March1st to 15thDay
17%13%46%6%36%445%27%
1897
16th to endDay
13%7%5%6%43435%6%38%
2154
April1st to 15thDay
23%10%45%42424432%
2152
16th to endDay
21%7%25%42443437%
2277
May1st to 15thDay
20%9%35%5%3435%5%32%
2506
16th to endDay
17%6%35%5%35%5%46%35%
2618
June1st to 15thDay
20%6%36%5%45%45%6%30%
2520
16th to endDay
15%6%35%6%36%5%6%8%34%
2520
July1st to 15thDay
14%425%5%35%5%7%7%36%
2520
16th to endDay
11%5%25%6%37%5%6%10%35%
2654
August1st to 15thDay
12%6%26%6%36%5%5%7%36%
2390
16th to endDay
12%6%25%5%35%5%6%9%38%
2381
September1st to 15thDay
17%5%35%43345%7%38%
2160
16th to endDay
15%6%35%424336%43%
1978
October1st to 15thDay
20%9%25%6%23445%34%
1800
16th to endDay
29%9%37%7%34435%23%
1860
November1st to 15thDay
18%10%36%6%34445%31%
1589
16th to endDay
27%13%5%7%6%2433419%
1558
December1st to 15thDay
22%15%6%8%7%45%445%14%
1440
16th to endDay
22%18%7%8%5%2333419%
1536
January1st to 15thNight
19%17%7%10%7%45%34416%
2506
16th to endNight
14%16%5%8%6%35%445%25%
2604
February1st to 15thNight
13%13%6%11%7%36%5%45%22%
2285
16th to endNight
16%13%5%9%7%3435%426%
1997
March1st to 15thNight
18%13%48%6%3443427%
2039
16th to endNight
14%9%45%5%23336%40%
2070
April1st to 15thNight
22%10%36%424335%33%
1796
16th to endNight
19%8%35%5%24336%37%
1693
May1st to 15thNight
21%7%36%423346%35%
1443
16th to endNight
15%5%25%7%26%45%5%39%
1495
June1st to 15thNight
18%6%25%5%2445%8%35%
1440
16th to endNight
15%5%245%35%5%7%8%35%
1440
July1st to 15thNight
10%3245%445%5%7%46%
1440
16th to endNight
11%423435%5%6%8%45%
1514
August1st to 15thNight
10%5%25%3345%6%8%43%
1569
16th to endNight
9%4244245%5%8%47%
1809
September1st to 15thNight
14%6%36%5%24346%41%
1800
16th to endNight
15%6%14424345%46%
1979
October1st to 15thNight
21%7%35%5%23345%38%
2160
16th to endNight
25%11%35%6%34345%25%
2364
November1st to 15thNight
19%10%36%5%44446%30%
2596
16th to endNight
24%13%5%8%6%2443423%
2728
December1st to 15thNight
22%17%6%8%5%3443418%
2520
16th to endNight
24%17%6%8%5%3443417%
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
67%5%8%12%5%
1433
16th to endDay
64%410%13%6%1
1617
February1st to 15thDay
65%5%10%13%4
1577
16th to endDay
61%49%13%9%
1476
March1st to 15thDay
59%411%15%7%1
1908
16th to endDay
46%410%20%14%4
2154
April1st to 15thDay
55%38%18%11%2
2152
16th to endDay
49%47%20%15%2
2277
May1st to 15thDay
52%5%9%16%13%2
2506
16th to endDay
48%7%10%19%11%2
2622
June1st to 15thDay
53%6%11%18%9%
2520
16th to endDay
46%7%12%19%11%1
2520
July1st to 15thDay
40%8%12%24%12%1
2371
16th to endDay
43%8%16%22%8%
2487
August1st to 15thDay
45%8%15%19%10%
2376
16th to endDay
41%8%16%24%8%
2381
September1st to 15thDay
43%7%15%22%11%
2160
16th to endDay
43%412%30%7%
1978
October1st to 15thDay
52%6%12%18%9%
1800
16th to endDay
63%6%11%13%4
1860
November1st to 15thDay
53%7%14%17%6%
1589
16th to endDay
68%6%9%10%3
1558
December1st to 15thDay
71%6%10%8%2
1440
16th to endDay
69%5%9%11%3
1536
January1st to 15thNight
71%6%9%9%3
2506
16th to endNight
60%6%10%14%7%
2604
February1st to 15thNight
63%6%11%14%4
2287
16th to endNight
60%5%9%18%7%
1997
March1st to 15thNight
60%49%16%7%
2051
16th to endNight
46%410%19%16%2
2070
April1st to 15thNight
53%47%18%13%2
1796
16th to endNight
49%47%20%14%3
1693
May1st to 15thNight
49%47%19%15%3
1443
16th to endNight
43%8%12%20%13%2
1497
June1st to 15thNight
46%7%14%20%10%
1440
16th to endNight
43%8%13%20%13%
1440
July1st to 15thNight
33%8%13%25%17%1
1360
16th to endNight
35%7%16%28%12%
1418
August1st to 15thNight
35%11%15%25%12%
1559
16th to endNight
32%8%18%30%9%
1809
September1st to 15thNight
43%5%13%25%11%
1800
16th to endNight
38%5%14%32%7%
1979
October1st to 15thNight
48%6%9%22%11%
2160
16th to endNight
61%6%12%16%4
2364
November1st to 15thNight
54%6%13%16%8%
2596
16th to endNight
65%5%12%12%3
2728
December1st to 15thNight
68%6%10%10%3
2520
16th to endNight
70%5%9%9%4
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
28%18%26%23%3
60
16th to endDay
44%6%31%9%9%
77
February1st to 15thDay
30%17%37%14%
90
16th to endDay
34%13%28%20%2
135
March1st to 15thDay
26%14%30%22%5%
270
16th to endDay
20%14%28%23%10%2
288
April1st to 15thDay
27%14%31%15%8%2
270
16th to endDay
26%13%25%16%12%4
270
May1st to 15thDay
32%9%21%22%8%4
288
16th to endDay
18%13%33%20%11%2
331
June1st to 15thDay
25%10%27%22%11%1
315
16th to endDay
13%10%31%27%13%3
315
July1st to 15thDay
14%5%27%32%15%4
305
16th to endDay
11%328%33%17%5%
326
August1st to 15thDay
16%421%27%22%7%
313
16th to endDay
15%323%27%18%11%
332
September1st to 15thDay
18%6%22%20%19%13%
315
16th to endDay
16%7%22%23%20%9%
314
October1st to 15thDay
26%10%25%21%13%1
315
16th to endDay
29%16%24%21%6%
321
November1st to 15thDay
21%12%30%22%13%
153
16th to endDay
35%16%34%7%32
90
December1st to 15thDay
13%21%35%20%8%1
60
16th to endDay
40%14%35%7%1
64
January1st to 15thNight
27%12%29%23%6%
720
16th to endNight
23%9%29%27%8%
768
February1st to 15thNight
19%11%38%23%6%
704
16th to endNight
23%12%32%24%6%
631
March1st to 15thNight
26%12%30%25%4
720
16th to endNight
19%13%28%26%11%
768
April1st to 15thNight
26%13%28%25%5%
718
16th to endNight
22%11%28%27%10%
613
May1st to 15thNight
24%6%28%28%11%1
363
16th to endNight
17%7%30%32%10%
375
June1st to 15thNight
20%5%29%34%10%
360
16th to endNight
18%5%24%36%13%
360
July1st to 15thNight
10%325%40%18%1
340
16th to endNight
10%323%41%20%
376
August1st to 15thNight
12%219%37%26%1
488
16th to endNight
10%422%37%22%1
663
September1st to 15thNight
18%426%27%20%2
720
16th to endNight
18%5%19%29%23%2
717
October1st to 15thNight
24%8%29%24%12%
720
16th to endNight
30%11%25%24%7%
768
November1st to 15thNight
25%11%26%25%10%
760
16th to endNight
30%15%24%21%6%
780
December1st to 15thNight
30%13%30%21%4
720
16th to endNight
34%10%27%21%5%
768
Page generated at 2017-12-01 12:13:40. Version ac04

Copyright 2017 A. Danko


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