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 2018-10-08.

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%
16492
11%
50885
8%
16455
36%
16455
15%
38330

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
11%
969
3%
2811
1%
968
13%
968
5%
2480
January16th to endNight
15%
832
4%
2704
2%
832
16%
832
5%
2383
February1st to 15thNight
15%
761
4%
2482
1%
761
18%
761
5%
2159
February16th to endNight
18%
683
8%
2132
4%
683
24%
683
9%
1734
March1st to 15thNight
22%
780
10%
2187
6%
780
26%
780
13%
1741
March16th to endNight
35%
832
18%
2288
11%
832
40%
832
21%
1631
April1st to 15thNight
27%
726
13%
1966
5%
726
33%
726
19%
1467
April16th to endNight
39%
579
17%
1735
11%
579
43%
579
21%
1195
May1st to 15thNight
42%
585
15%
1755
12%
585
46%
585
23%
1174
May16th to endNight
49%
418
16%
1637
15%
418
59%
418
23%
969
June1st to 15thNight
46%
390
13%
1430
14%
390
52%
390
22%
881
June16th to endNight
53%
390
14%
1365
17%
390
57%
390
26%
824
July1st to 15thNight
62%
370
20%
1295
24%
370
67%
370
36%
684
July16th to endNight
58%
604
14%
1698
12%
571
60%
571
30%
1047
August1st to 15thNight
61%
575
17%
1715
13%
572
64%
572
30%
1062
August16th to endNight
58%
623
20%
1865
14%
623
61%
623
28%
1174
September1st to 15thNight
54%
780
19%
2034
12%
780
57%
780
32%
1329
September16th to endNight
54%
777
19%
2145
14%
777
56%
777
29%
1394
October1st to 15thNight
36%
752
13%
2235
11%
752
40%
752
18%
1623
October16th to endNight
23%
768
8%
2340
5%
768
28%
768
10%
1895
November1st to 15thNight
28%
760
13%
2548
11%
760
32%
760
13%
1927
November16th to endNight
20%
780
7%
2730
6%
780
23%
780
7%
2268
December1st to 15thNight
11%
780
1%
2730
1%
780
13%
780
3%
2495
December16th to endNight
9%
978
2%
3058
0%
978
11%
978
4%
2794

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%
52246
Night
16%11%5%8%6%34446%28%
51056
Cloud CoverDay
16%10%47%6%34446%30%
52256
Night
16%11%5%8%6%34446%28%
51060
TransparencyDay
54%6%11%17%9%1
51935
Night
57%6%10%16%8%
50885
SeeingDay
21%8%26%24%13%5%
7124
Night
22%9%27%27%11%1
16500

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
17%15%10%16%9%35%33410%
1452
16th to endDay
12%19%9%16%10%4443410%
1872
February1st to 15thDay
14%17%8%17%9%45%33311%
1710
16th to endDay
16%18%8%11%8%3444416%
1626
March1st to 15thDay
14%14%6%11%8%34425%24%
2092
16th to endDay
15%8%6%7%6%24445%32%
2288
April1st to 15thDay
19%13%47%424345%28%
2324
16th to endDay
19%10%24413347%38%
2500
May1st to 15thDay
19%6%25%42345%6%38%
2526
16th to endDay
14%6%345%2445%7%43%
2829
June1st to 15thDay
15%6%24425%5%5%7%39%
2856
16th to endDay
16%5%25%435%45%8%38%
2925
July1st to 15thDay
11%424425%5%6%8%44%
2925
16th to endDay
11%6%35%4245%7%9%39%
2713
August1st to 15thDay
12%5%25%6%35%5%6%10%35%
2487
16th to endDay
13%5%35%5%345%6%8%37%
2675
September1st to 15thDay
16%7%26%5%2445%7%36%
2252
16th to endDay
16%5%35%43345%7%40%
2145
October1st to 15thDay
22%9%37%6%24346%28%
1895
16th to endDay
30%13%36%6%35%33417%
1881
November1st to 15thDay
17%15%5%9%5%35%445%24%
1639
16th to endDay
19%20%7%9%6%35%44414%
1560
December1st to 15thDay
16%22%11%14%8%25%3246%
1560
16th to endDay
19%23%10%12%8%333348%
1514
January1st to 15thNight
19%16%7%12%9%44445%10%
2811
16th to endNight
13%15%9%14%11%5%6%44410%
2704
February1st to 15thNight
12%18%8%14%10%45%33413%
2480
16th to endNight
15%12%8%13%8%35%335%19%
2132
March1st to 15thNight
14%13%5%10%8%35%44425%
2175
16th to endNight
14%10%5%6%5%3443437%
2288
April1st to 15thNight
20%11%45%5%23446%31%
1966
16th to endNight
16%7%25%5%3445%5%37%
1735
May1st to 15thNight
15%6%35%434447%38%
1755
16th to endNight
11%5%25%43446%6%45%
1635
June1st to 15thNight
13%5%25%6%3345%8%40%
1430
16th to endNight
12%415%4246%48%44%
1365
July1st to 15thNight
7%41442336%8%53%
1365
16th to endNight
8%325%5%346%5%8%45%
1804
August1st to 15thNight
9%4145%35%5%5%8%45%
1726
16th to endNight
11%5%245%34446%47%
1865
September1st to 15thNight
12%42442436%7%45%
2034
16th to endNight
13%5%25%42435%7%44%
2145
October1st to 15thNight
21%8%25%5%2445%6%32%
2235
16th to endNight
27%11%46%6%2445%5%21%
2340
November1st to 15thNight
20%11%36%5%35%45%6%25%
2548
16th to endNight
22%16%7%8%6%33336%17%
2730
December1st to 15thNight
19%22%9%13%7%343439%
2730
16th to endNight
19%18%11%14%7%343348%
3058

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%10%17%10%35%33410%
1452
16th to endDay
12%19%9%16%9%4433410%
1872
February1st to 15thDay
14%18%8%17%9%45%33311%
1710
16th to endDay
16%18%8%11%8%3343416%
1626
March1st to 15thDay
15%14%6%12%8%34425%23%
2103
16th to endDay
15%8%5%7%6%25%445%32%
2287
April1st to 15thDay
20%13%47%423445%28%
2324
16th to endDay
19%10%24423347%38%
2500
May1st to 15thDay
19%7%2442445%7%37%
2526
16th to endDay
14%6%245%2445%7%43%
2829
June1st to 15thDay
15%6%34425%45%7%38%
2856
16th to endDay
16%4245%25%45%8%39%
2925
July1st to 15thDay
11%424435%5%5%8%43%
2925
16th to endDay
11%6%26%435%5%6%9%39%
2713
August1st to 15thDay
12%435%6%35%6%6%9%35%
2487
16th to endDay
13%5%35%5%35%5%6%8%36%
2675
September1st to 15thDay
16%7%26%5%3445%7%36%
2252
16th to endDay
17%5%26%42345%7%40%
2145
October1st to 15thDay
22%9%47%5%3335%5%29%
1895
16th to endDay
31%13%27%6%35%235%17%
1881
November1st to 15thDay
17%15%5%8%5%34445%24%
1639
16th to endDay
19%20%7%8%7%45%35%414%
1560
December1st to 15thDay
16%23%12%13%8%35%2337%
1560
16th to endDay
18%22%10%12%9%333248%
1514
January1st to 15thNight
19%16%6%13%8%45%44411%
2811
16th to endNight
13%15%9%14%10%5%5%44410%
2704
February1st to 15thNight
13%17%8%13%10%45%33413%
2473
16th to endNight
15%13%8%12%8%35%345%19%
2132
March1st to 15thNight
14%13%6%11%8%3444425%
2187
16th to endNight
14%9%5%7%5%34435%37%
2288
April1st to 15thNight
20%12%36%424446%31%
1966
16th to endNight
16%8%25%5%34445%37%
1735
May1st to 15thNight
16%6%35%5%25%45%7%38%
1754
16th to endNight
11%5%2443446%6%45%
1635
June1st to 15thNight
13%5%25%6%3445%8%40%
1430
16th to endNight
12%4145%335%5%8%43%
1365
July1st to 15thNight
7%32442346%7%54%
1365
16th to endNight
8%415%5%346%5%8%45%
1804
August1st to 15thNight
9%5%145%25%5%6%7%45%
1726
16th to endNight
11%5%2443445%6%47%
1865
September1st to 15thNight
13%42443435%8%44%
2034
16th to endNight
13%5%25%324447%44%
2145
October1st to 15thNight
22%7%26%5%3435%6%31%
2235
16th to endNight
27%10%37%6%35%445%21%
2340
November1st to 15thNight
20%12%36%6%45%45%6%25%
2548
16th to endNight
22%16%6%9%7%33345%17%
2730
December1st to 15thNight
19%22%9%13%7%25%3339%
2730
16th to endNight
20%17%12%13%7%343339%
3058

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
79%5%6%6%1
1453
16th to endDay
79%47%6%2
1872
February1st to 15thDay
77%5%6%8%1
1712
16th to endDay
70%6%8%9%4
1626
March1st to 15thDay
64%410%12%7%
2103
16th to endDay
51%5%13%15%11%2
2288
April1st to 15thDay
57%5%8%18%9%
2324
16th to endDay
46%5%10%19%15%2
2500
May1st to 15thDay
45%5%10%24%13%
2526
16th to endDay
40%6%14%21%15%2
2833
June1st to 15thDay
42%6%13%22%13%
2856
16th to endDay
43%6%13%24%11%
2925
July1st to 15thDay
35%7%14%22%18%3
2766
16th to endDay
38%8%15%22%12%1
2556
August1st to 15thDay
41%8%16%19%11%1
2474
16th to endDay
42%8%15%22%9%
2675
September1st to 15thDay
45%7%13%21%10%1
2252
16th to endDay
42%6%14%27%8%
2145
October1st to 15thDay
56%5%9%16%9%1
1895
16th to endDay
70%5%11%8%3
1881
November1st to 15thDay
62%6%12%12%6%
1639
16th to endDay
73%6%9%7%2
1560
December1st to 15thDay
83%5%6%3
1560
16th to endDay
83%46%5%
1514
January1st to 15thNight
76%5%9%6%1
2811
16th to endNight
77%5%9%42
2704
February1st to 15thNight
76%48%8%1
2482
16th to endNight
68%410%10%5%
2132
March1st to 15thNight
62%5%8%15%6%
2187
16th to endNight
50%49%20%12%2
2288
April1st to 15thNight
54%5%9%17%12%
1966
16th to endNight
47%5%8%17%17%2
1735
May1st to 15thNight
44%6%9%22%14%2
1755
16th to endNight
37%7%11%25%15%2
1637
June1st to 15thNight
41%5%11%23%15%1
1430
16th to endNight
36%7%13%24%15%1
1365
July1st to 15thNight
27%6%12%26%24%2
1295
16th to endNight
34%8%14%23%17%1
1698
August1st to 15thNight
34%8%15%26%13%1
1715
16th to endNight
37%7%11%28%13%1
1865
September1st to 15thNight
37%6%13%28%12%1
2034
16th to endNight
39%6%14%26%12%
2145
October1st to 15thNight
51%7%10%18%11%
2235
16th to endNight
64%6%13%11%4
2340
November1st to 15thNight
58%6%12%15%5%1
2548
16th to endNight
70%6%11%9%1
2730
December1st to 15thNight
81%7%7%31
2730
16th to endNight
81%5%7%4
3058

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
21%18%42%14%2
112
16th to endDay
31%11%34%21%1
144
February1st to 15thDay
31%20%38%9%
135
16th to endDay
28%25%31%12%1
120
March1st to 15thDay
23%13%32%19%9%1
288
16th to endDay
24%8%31%24%9%1
352
April1st to 15thDay
28%12%27%21%8%2
330
16th to endDay
24%10%24%24%9%7%
319
May1st to 15thDay
24%5%28%23%12%5%
348
16th to endDay
16%5%27%25%17%6%
395
June1st to 15thDay
18%7%24%30%16%2
501
16th to endDay
17%6%29%29%14%2
570
July1st to 15thDay
11%426%30%18%7%
550
16th to endDay
11%425%29%19%9%
422
August1st to 15thDay
14%221%29%19%13%
358
16th to endDay
18%415%26%20%14%
396
September1st to 15thDay
14%319%25%21%15%
375
16th to endDay
18%5%20%25%18%12%
374
October1st to 15thDay
26%8%24%24%11%3
345
16th to endDay
36%14%25%19%4
297
November1st to 15thDay
28%14%25%18%11%1
117
16th to endDay
35%15%32%11%32
90
December1st to 15thDay
31%27%27%11%2
90
16th to endDay
40%14%35%9%
96
January1st to 15thNight
26%16%34%16%5%
973
16th to endNight
21%12%36%24%5%
832
February1st to 15thNight
21%16%34%23%3
764
16th to endNight
24%12%33%24%5%
683
March1st to 15thNight
20%14%32%23%7%1
780
16th to endNight
19%8%30%30%9%1
832
April1st to 15thNight
26%10%30%25%6%
726
16th to endNight
20%9%25%32%10%1
579
May1st to 15thNight
20%5%25%32%13%1
585
16th to endNight
13%426%40%15%
419
June1st to 15thNight
15%5%23%42%12%
390
16th to endNight
16%223%42%14%1
390
July1st to 15thNight
8%220%46%21%1
370
16th to endNight
9%220%40%24%1
604
August1st to 15thNight
12%115%39%29%1
575
16th to endNight
13%218%33%28%3
623
September1st to 15thNight
14%421%32%20%7%
780
16th to endNight
16%5%18%34%20%4
777
October1st to 15thNight
25%6%25%27%13%1
752
16th to endNight
32%11%27%23%2
768
November1st to 15thNight
26%11%29%22%9%
760
16th to endNight
31%14%26%22%5%
780
December1st to 15thNight
32%15%32%16%2
780
16th to endNight
30%12%35%16%3
978
Page generated at 2018-10-09 10:39:11. Version ac04

Copyright 2018 A. Danko


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