Walkerton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Walkerton clear sky chart from 2005-11-05 to 2017-09-17.

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%
15140
11%
46731
8%
15103
36%
15103
14%
35321

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
10%
894
3%
2594
1%
893
12%
893
5%
2309
January16th to endNight
16%
768
4%
2496
2%
768
17%
768
5%
2213
February1st to 15thNight
15%
701
4%
2287
2%
701
18%
701
5%
1996
February16th to endNight
19%
631
8%
1970
4%
631
24%
631
9%
1604
March1st to 15thNight
22%
720
10%
2019
6%
720
26%
720
12%
1620
March16th to endNight
35%
768
18%
2112
11%
768
40%
768
20%
1520
April1st to 15thNight
28%
670
13%
1814
5%
670
33%
670
20%
1338
April16th to endNight
38%
540
17%
1620
10%
540
42%
540
21%
1118
May1st to 15thNight
42%
540
15%
1620
12%
540
46%
540
23%
1090
May16th to endNight
48%
385
16%
1508
15%
385
58%
385
23%
906
June1st to 15thNight
45%
360
12%
1320
12%
360
51%
360
21%
826
June16th to endNight
52%
360
14%
1260
17%
360
57%
360
26%
767
July1st to 15thNight
62%
340
18%
1190
22%
340
66%
340
34%
644
July16th to endNight
58%
557
14%
1558
12%
524
60%
524
30%
963
August1st to 15thNight
62%
539
16%
1609
12%
536
64%
536
30%
1000
August16th to endNight
58%
575
21%
1721
15%
575
61%
575
29%
1070
September1st to 15thNight
53%
720
18%
1878
11%
720
56%
720
31%
1232
September16th to endNight
52%
665
18%
1837
13%
665
55%
665
29%
1202
October1st to 15thNight
37%
660
14%
1963
12%
660
41%
660
18%
1416
October16th to endNight
23%
704
7%
2145
4%
704
27%
704
10%
1750
November1st to 15thNight
29%
700
13%
2347
12%
700
34%
700
14%
1752
November16th to endNight
20%
720
7%
2520
6%
720
23%
720
7%
2099
December1st to 15thNight
11%
720
2%
2520
1%
720
12%
720
3%
2304
December16th to endNight
9%
903
2%
2823
0%
903
11%
903
4%
2582

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
16%10%47%6%3445%6%30%
48041
Night
16%11%5%8%6%34445%28%
46902
Cloud CoverDay
16%10%47%6%34446%29%
48051
Night
16%11%5%8%6%34445%28%
46906
TransparencyDay
54%6%11%17%9%
47730
Night
57%6%10%15%8%
46731
SeeingDay
20%8%26%24%13%6%
5748
Night
22%9%27%27%11%1
15148

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%15%10%16%9%4433410%
1340
16th to endDay
12%19%9%16%10%444349%
1728
February1st to 15thDay
14%17%8%16%9%45%33311%
1575
16th to endDay
16%18%8%11%8%3434415%
1502
March1st to 15thDay
14%13%6%12%8%34425%24%
1930
16th to endDay
15%9%6%7%6%2445%6%31%
2112
April1st to 15thDay
19%13%46%424346%30%
2145
16th to endDay
18%10%24413347%37%
2340
May1st to 15thDay
19%7%25%42345%6%37%
2331
16th to endDay
14%6%345%2445%7%42%
2606
June1st to 15thDay
15%6%244245%5%7%38%
2636
16th to endDay
16%5%25%435%45%8%38%
2700
July1st to 15thDay
11%5%25%426%5%6%8%42%
2700
16th to endDay
11%6%25%4245%7%9%39%
2501
August1st to 15thDay
12%5%26%6%35%5%6%9%36%
2340
16th to endDay
13%5%25%5%35%5%7%8%37%
2468
September1st to 15thDay
16%7%26%5%2435%7%37%
2079
16th to endDay
17%5%35%42345%7%39%
1829
October1st to 15thDay
21%8%37%5%2445%6%29%
1667
16th to endDay
32%13%36%6%35%34416%
1724
November1st to 15thDay
16%15%5%8%435%445%26%
1510
16th to endDay
19%20%7%9%6%45%44414%
1440
December1st to 15thDay
17%22%12%14%8%25%3236%
1440
16th to endDay
19%23%10%12%8%243348%
1398
January1st to 15thNight
20%16%7%12%9%4444410%
2594
16th to endNight
13%15%10%14%11%5%6%44410%
2496
February1st to 15thNight
13%18%8%13%10%45%33314%
2285
16th to endNight
15%13%8%13%8%35%335%18%
1970
March1st to 15thNight
15%12%6%10%8%35%44424%
2007
16th to endNight
15%10%5%7%5%2443436%
2112
April1st to 15thNight
20%11%44423446%32%
1814
16th to endNight
16%7%25%5%3445%5%37%
1620
May1st to 15thNight
16%6%35%5%35%447%37%
1620
16th to endNight
11%5%25%435%45%6%45%
1506
June1st to 15thNight
13%5%25%6%3445%8%39%
1320
16th to endNight
12%5%5%5%25%6%48%43%
1260
July1st to 15thNight
7%41442336%8%51%
1260
16th to endNight
9%325%5%246%5%8%45%
1664
August1st to 15thNight
9%4145%35%5%5%8%45%
1620
16th to endNight
11%5%245%24446%49%
1721
September1st to 15thNight
13%42442435%7%45%
1878
16th to endNight
14%6%24424346%44%
1837
October1st to 15thNight
20%7%25%5%2445%6%32%
1963
16th to endNight
28%12%36%6%2445%5%20%
2145
November1st to 15thNight
19%11%36%5%46%45%6%27%
2347
16th to endNight
22%17%7%8%6%33336%16%
2520
December1st to 15thNight
20%22%9%12%7%243439%
2520
16th to endNight
20%18%12%14%6%343348%
2823

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%10%17%9%35%33410%
1340
16th to endDay
11%19%10%16%10%443349%
1728
February1st to 15thDay
14%18%8%17%9%45%33411%
1575
16th to endDay
16%18%8%11%8%4343415%
1502
March1st to 15thDay
15%13%6%11%8%34435%23%
1941
16th to endDay
15%9%6%7%6%25%446%30%
2111
April1st to 15thDay
19%13%46%424446%30%
2145
16th to endDay
18%10%24423347%37%
2340
May1st to 15thDay
19%7%25%42445%7%37%
2331
16th to endDay
14%6%25%5%25%45%7%42%
2606
June1st to 15thDay
15%6%34425%45%7%38%
2636
16th to endDay
16%4245%25%45%8%38%
2700
July1st to 15thDay
11%5%345%35%5%6%8%41%
2700
16th to endDay
11%6%25%435%5%7%9%39%
2501
August1st to 15thDay
12%5%36%6%35%6%6%9%35%
2340
16th to endDay
13%5%35%5%35%5%6%8%37%
2468
September1st to 15thDay
16%7%26%5%2345%7%37%
2079
16th to endDay
18%5%26%42345%7%40%
1829
October1st to 15thDay
21%8%47%5%3345%5%29%
1667
16th to endDay
32%13%37%6%35%235%16%
1724
November1st to 15thDay
17%14%5%8%5%34445%26%
1510
16th to endDay
19%20%6%9%7%45%35%414%
1440
December1st to 15thDay
17%22%12%13%8%35%2346%
1440
16th to endDay
18%23%10%12%8%233248%
1398
January1st to 15thNight
19%17%6%13%8%45%43410%
2594
16th to endNight
13%15%9%14%11%6%5%44410%
2496
February1st to 15thNight
13%18%8%13%10%45%33413%
2278
16th to endNight
15%13%8%13%8%35%335%18%
1970
March1st to 15thNight
15%12%6%11%8%34445%24%
2019
16th to endNight
15%10%5%7%5%34335%35%
2112
April1st to 15thNight
20%12%35%423446%32%
1814
16th to endNight
15%8%25%5%35%445%37%
1620
May1st to 15thNight
16%6%35%5%25%45%7%37%
1619
16th to endNight
11%5%2443446%6%45%
1506
June1st to 15thNight
14%5%25%5%3445%8%38%
1320
16th to endNight
12%4145%336%5%8%43%
1260
July1st to 15thNight
7%42442346%7%52%
1260
16th to endNight
9%415%5%346%6%8%45%
1664
August1st to 15thNight
10%5%145%25%5%6%7%45%
1620
16th to endNight
11%5%24424446%48%
1721
September1st to 15thNight
13%425%43335%7%44%
1878
16th to endNight
14%6%25%324346%45%
1837
October1st to 15thNight
21%6%26%5%3436%7%32%
1963
16th to endNight
28%11%37%6%34445%20%
2145
November1st to 15thNight
19%11%35%6%45%45%6%27%
2347
16th to endNight
22%16%6%9%7%33245%17%
2520
December1st to 15thNight
20%22%9%12%7%243439%
2520
16th to endNight
20%17%12%13%7%343338%
2823

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
80%5%6%6%1
1341
16th to endDay
79%47%6%2
1728
February1st to 15thDay
77%5%7%8%1
1577
16th to endDay
72%5%8%9%4
1502
March1st to 15thDay
64%410%13%6%
1941
16th to endDay
52%5%13%15%10%1
2112
April1st to 15thDay
55%6%9%19%9%
2145
16th to endDay
46%5%11%20%14%1
2340
May1st to 15thDay
46%5%10%22%13%
2331
16th to endDay
41%6%13%21%14%2
2610
June1st to 15thDay
43%5%13%23%13%
2636
16th to endDay
43%6%13%24%11%
2700
July1st to 15thDay
36%7%14%22%15%2
2541
16th to endDay
38%8%15%23%12%1
2344
August1st to 15thDay
41%8%16%19%12%1
2327
16th to endDay
41%9%16%22%10%1
2468
September1st to 15thDay
45%7%13%22%10%1
2079
16th to endDay
43%6%14%26%9%
1829
October1st to 15thDay
55%5%10%16%10%1
1667
16th to endDay
71%6%10%8%3
1724
November1st to 15thDay
60%6%12%12%7%
1510
16th to endDay
74%6%8%7%2
1440
December1st to 15thDay
84%6%5%3
1440
16th to endDay
82%46%5%
1398
January1st to 15thNight
77%6%8%5%1
2594
16th to endNight
78%5%9%42
2496
February1st to 15thNight
76%48%8%1
2287
16th to endNight
68%410%10%5%
1970
March1st to 15thNight
62%5%9%15%5%
2019
16th to endNight
51%49%19%12%2
2112
April1st to 15thNight
52%5%10%18%12%
1814
16th to endNight
47%5%9%17%16%2
1620
May1st to 15thNight
45%5%10%22%14%2
1620
16th to endNight
38%7%11%25%13%2
1508
June1st to 15thNight
42%5%11%22%15%1
1320
16th to endNight
37%7%13%24%15%1
1260
July1st to 15thNight
29%6%12%27%22%1
1190
16th to endNight
34%8%14%23%17%1
1558
August1st to 15thNight
34%8%16%25%13%1
1609
16th to endNight
36%6%11%28%14%1
1721
September1st to 15thNight
38%6%13%28%11%1
1878
16th to endNight
40%5%14%26%12%
1837
October1st to 15thNight
50%7%11%18%11%
1963
16th to endNight
65%6%12%10%4
2145
November1st to 15thNight
56%6%13%16%6%1
2347
16th to endNight
70%5%10%9%1
2520
December1st to 15thNight
81%6%7%31
2520
16th to endNight
81%6%7%4
2823

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
20%22%44%9%4
75
16th to endDay
30%13%29%26%1
96
February1st to 15thDay
34%18%36%10%
90
16th to endDay
25%25%30%14%2
81
March1st to 15thDay
25%12%33%20%7%
231
16th to endDay
26%7%29%23%11%2
288
April1st to 15thDay
25%11%27%23%9%2
270
16th to endDay
24%10%26%21%9%8%
270
May1st to 15thDay
24%5%28%21%12%6%
288
16th to endDay
17%6%29%22%16%6%
331
June1st to 15thDay
18%7%24%29%16%3
431
16th to endDay
16%7%29%28%14%3
495
July1st to 15thDay
12%5%27%29%17%7%
475
16th to endDay
11%324%29%20%10%
355
August1st to 15thDay
13%221%27%20%14%
313
16th to endDay
16%5%14%27%20%15%
332
September1st to 15thDay
14%417%27%21%14%
315
16th to endDay
20%420%23%17%13%
259
October1st to 15thDay
21%8%24%29%12%3
255
16th to endDay
38%11%25%19%4
236
November1st to 15thDay
23%12%28%19%14%2
78
16th to endDay
36%16%26%13%33
60
December1st to 15thDay
36%31%20%10%1
60
16th to endDay
43%17%37%1
64
January1st to 15thNight
26%17%34%15%5%
898
16th to endNight
21%11%35%24%5%
768
February1st to 15thNight
21%16%34%23%3
704
16th to endNight
23%12%31%26%5%
631
March1st to 15thNight
21%15%32%23%6%
720
16th to endNight
20%8%30%29%9%1
768
April1st to 15thNight
26%10%30%25%6%
670
16th to endNight
20%10%26%31%10%1
540
May1st to 15thNight
21%5%26%32%13%1
540
16th to endNight
13%426%38%16%
386
June1st to 15thNight
16%5%24%40%12%
360
16th to endNight
16%223%41%14%1
360
July1st to 15thNight
9%220%46%20%1
340
16th to endNight
9%321%41%23%1
557
August1st to 15thNight
11%115%41%28%1
539
16th to endNight
14%218%33%28%4
575
September1st to 15thNight
15%420%32%19%7%
720
16th to endNight
17%5%18%34%19%4
665
October1st to 15thNight
23%6%25%28%13%1
660
16th to endNight
33%11%27%23%3
704
November1st to 15thNight
25%11%30%22%10%1
700
16th to endNight
31%13%25%23%5%
720
December1st to 15thNight
33%15%32%15%2
720
16th to endNight
31%12%35%16%3
903
Page generated at 2017-09-18 08:38:27. Version ac04

Copyright 2017 A. Danko


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