Wiarton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wiarton 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%
15160
10%
46738
7%
15123
35%
15123
14%
35508

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
9%
896
1%
2619
0%
895
11%
895
4%
2400
January16th to endNight
17%
803
3%
2531
2%
803
18%
803
5%
2270
February1st to 15thNight
17%
701
3%
2287
1%
701
19%
701
5%
1972
February16th to endNight
24%
631
8%
1976
3%
631
29%
631
10%
1591
March1st to 15thNight
23%
720
11%
2022
6%
720
28%
720
15%
1572
March16th to endNight
37%
768
18%
2112
11%
768
41%
768
22%
1494
April1st to 15thNight
31%
663
14%
1803
6%
663
37%
663
22%
1284
April16th to endNight
38%
540
17%
1620
10%
540
44%
540
23%
1100
May1st to 15thNight
46%
531
14%
1611
13%
531
49%
531
22%
1071
May16th to endNight
50%
374
15%
1497
13%
374
59%
374
22%
880
June1st to 15thNight
48%
360
12%
1287
12%
360
54%
360
22%
813
June16th to endNight
56%
360
13%
1260
15%
360
60%
360
26%
765
July1st to 15thNight
64%
340
17%
1190
20%
340
69%
340
35%
632
July16th to endNight
60%
530
14%
1502
14%
497
61%
497
29%
935
August1st to 15thNight
59%
539
16%
1609
12%
536
62%
536
30%
987
August16th to endNight
59%
573
18%
1719
14%
573
62%
573
30%
1071
September1st to 15thNight
54%
717
16%
1870
10%
717
57%
717
30%
1248
September16th to endNight
50%
665
18%
1837
14%
665
51%
665
26%
1245
October1st to 15thNight
35%
660
13%
1964
10%
660
39%
660
16%
1461
October16th to endNight
20%
704
6%
2154
4%
704
23%
704
9%
1792
November1st to 15thNight
25%
700
11%
2363
10%
700
28%
700
12%
1825
November16th to endNight
19%
720
5%
2520
4%
720
20%
720
6%
2147
December1st to 15thNight
11%
720
1%
2520
0%
720
12%
720
3%
2322
December16th to endNight
8%
945
2%
2865
0%
945
10%
945
3%
2631

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%5%3445%6%32%
48029
Night
17%11%5%8%6%34446%27%
46909
Cloud CoverDay
15%10%47%5%3445%6%32%
48039
Night
16%11%5%8%6%34446%27%
46913
TransparencyDay
51%6%12%18%9%
47718
Night
57%6%11%15%8%
46738
SeeingDay
19%6%24%28%16%5%
5792
Night
21%9%27%26%12%2
15168

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
19%18%11%15%8%343237%
1316
16th to endDay
14%18%9%14%10%5%443310%
1691
February1st to 15thDay
12%18%9%14%9%45%34412%
1575
16th to endDay
15%16%7%8%7%47%5%45%17%
1494
March1st to 15thDay
13%10%49%6%45%5%5%5%28%
1927
16th to endDay
14%7%46%6%25%5%5%6%35%
2112
April1st to 15thDay
21%10%26%423347%33%
2154
16th to endDay
19%7%25%423347%38%
2340
May1st to 15thDay
18%6%34415%447%40%
2337
16th to endDay
12%5%244245%49%44%
2618
June1st to 15thDay
12%6%34425%5%6%8%39%
2670
16th to endDay
13%5%245%345%6%8%41%
2700
July1st to 15thDay
9%5%2442446%8%47%
2700
16th to endDay
9%5%243245%6%10%44%
2555
August1st to 15thDay
11%5%2442345%8%47%
2340
16th to endDay
13%5%25%43445%7%42%
2474
September1st to 15thDay
15%6%25%5%24447%40%
2085
16th to endDay
18%5%25%42446%8%37%
1829
October1st to 15thDay
21%10%37%5%34335%31%
1665
16th to endDay
32%13%47%5%3334416%
1716
November1st to 15thDay
20%15%46%7%345%46%21%
1495
16th to endDay
23%20%7%8%6%345%3413%
1440
December1st to 15thDay
20%23%9%13%7%243347%
1440
16th to endDay
20%25%9%11%6%343347%
1356
January1st to 15thNight
21%18%8%13%9%344437%
2619
16th to endNight
15%17%9%14%9%34445%11%
2531
February1st to 15thNight
13%18%8%12%9%5%5%44414%
2285
16th to endNight
16%12%7%10%7%35%446%20%
1976
March1st to 15thNight
16%11%6%8%6%2445%427%
2010
16th to endNight
14%8%5%6%5%23335%39%
2112
April1st to 15thNight
20%8%35%42435%7%35%
1803
16th to endNight
19%7%25%5%24446%37%
1620
May1st to 15thNight
15%6%46%5%35%446%36%
1611
16th to endNight
11%426%435%5%5%7%43%
1495
June1st to 15thNight
12%6%25%5%35%45%9%38%
1287
16th to endNight
11%5%236%245%6%8%42%
1260
July1st to 15thNight
9%32342335%9%51%
1260
16th to endNight
8%423436%5%6%8%46%
1608
August1st to 15thNight
9%5%15%4245%6%9%45%
1620
16th to endNight
9%6%25%6%33446%46%
1719
September1st to 15thNight
13%425%4245%5%7%43%
1870
16th to endNight
14%6%26%5%34336%41%
1837
October1st to 15thNight
21%8%36%6%3446%6%29%
1964
16th to endNight
28%11%37%6%34346%19%
2154
November1st to 15thNight
19%12%49%6%35%446%24%
2363
16th to endNight
24%17%5%7%5%33445%16%
2520
December1st to 15thNight
20%24%9%12%5%344338%
2520
16th to endNight
22%21%9%12%7%342339%
2865

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
18%18%11%15%10%343238%
1316
16th to endDay
13%19%9%15%10%4443310%
1691
February1st to 15thDay
13%17%9%14%9%5%5%43411%
1575
16th to endDay
15%16%7%9%8%45%446%16%
1494
March1st to 15thDay
13%11%49%6%46%5%45%28%
1938
16th to endDay
14%7%46%7%25%5%5%7%34%
2111
April1st to 15thDay
20%11%35%424346%32%
2154
16th to endDay
19%7%25%423447%38%
2340
May1st to 15thDay
17%6%34424446%40%
2337
16th to endDay
11%5%144345%5%8%44%
2618
June1st to 15thDay
13%6%24425%5%6%8%39%
2670
16th to endDay
12%5%245%345%5%8%40%
2700
July1st to 15thDay
10%42342447%8%46%
2700
16th to endDay
9%5%243245%7%9%44%
2555
August1st to 15thDay
10%42443445%8%46%
2340
16th to endDay
12%6%25%4345%5%8%41%
2474
September1st to 15thDay
14%6%35%5%245%47%39%
2085
16th to endDay
17%6%35%5%2446%7%37%
1829
October1st to 15thDay
21%9%47%6%23435%31%
1665
16th to endDay
33%12%48%5%3334416%
1716
November1st to 15thDay
18%15%47%7%35%45%6%21%
1495
16th to endDay
22%20%5%8%6%35%44413%
1440
December1st to 15thDay
19%23%9%11%8%334338%
1440
16th to endDay
19%24%9%12%7%44235%6%
1356
January1st to 15thNight
20%18%8%13%10%35%4347%
2619
16th to endNight
15%17%9%13%9%44445%11%
2531
February1st to 15thNight
13%17%8%12%9%45%44414%
2278
16th to endNight
15%12%7%11%6%45%5%45%21%
1976
March1st to 15thNight
14%12%5%9%6%43445%27%
2022
16th to endNight
13%10%5%6%5%33335%39%
2112
April1st to 15thNight
20%8%26%423347%34%
1803
16th to endNight
18%7%35%424446%37%
1620
May1st to 15thNight
14%6%46%6%35%45%6%36%
1610
16th to endNight
10%5%25%5%3446%6%43%
1495
June1st to 15thNight
12%6%25%5%35%45%9%38%
1287
16th to endNight
11%5%245%35%5%6%7%42%
1260
July1st to 15thNight
9%32331435%10%51%
1260
16th to endNight
7%414435%6%6%7%46%
1608
August1st to 15thNight
8%6%25%4245%6%9%45%
1620
16th to endNight
10%5%35%434447%46%
1719
September1st to 15thNight
12%425%5%3446%7%43%
1870
16th to endNight
13%6%36%6%24347%41%
1837
October1st to 15thNight
20%7%38%5%35%446%30%
1964
16th to endNight
27%11%47%6%34346%19%
2154
November1st to 15thNight
17%13%48%7%345%5%5%24%
2363
16th to endNight
22%17%5%9%5%34345%17%
2520
December1st to 15thNight
19%23%9%11%7%25%3448%
2520
16th to endNight
21%20%10%12%8%343338%
2865

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
83%6%44
1317
16th to endDay
79%5%8%42
1691
February1st to 15thDay
76%6%8%7%1
1577
16th to endDay
68%6%10%9%5%
1494
March1st to 15thDay
56%6%12%16%7%
1938
16th to endDay
48%6%12%17%13%1
2112
April1st to 15thDay
52%49%21%11%
2154
16th to endDay
45%5%11%21%14%2
2340
May1st to 15thDay
43%5%10%23%15%2
2337
16th to endDay
36%6%14%24%15%1
2622
June1st to 15thDay
40%7%13%24%13%
2670
16th to endDay
38%8%13%25%12%
2700
July1st to 15thDay
32%7%15%26%16%2
2541
16th to endDay
34%7%15%27%13%1
2398
August1st to 15thDay
35%7%16%24%14%1
2327
16th to endDay
38%8%16%24%10%1
2474
September1st to 15thDay
43%6%13%24%10%
2085
16th to endDay
44%7%14%24%8%
1829
October1st to 15thDay
55%5%10%18%9%
1665
16th to endDay
71%6%11%8%2
1716
November1st to 15thDay
62%8%11%11%6%
1495
16th to endDay
74%7%10%5%1
1440
December1st to 15thDay
82%8%6%2
1440
16th to endDay
83%5%6%3
1356
January1st to 15thNight
80%6%8%31
2619
16th to endNight
76%8%8%41
2531
February1st to 15thNight
73%7%9%8%1
2287
16th to endNight
64%7%11%10%5%
1976
March1st to 15thNight
58%6%10%16%6%
2022
16th to endNight
48%5%9%18%15%2
2112
April1st to 15thNight
50%410%21%11%1
1803
16th to endNight
46%410%17%18%2
1620
May1st to 15thNight
46%410%20%16%2
1611
16th to endNight
39%6%12%24%15%2
1497
June1st to 15thNight
42%6%11%23%15%1
1287
16th to endNight
38%5%13%27%14%
1260
July1st to 15thNight
28%5%13%29%19%2
1190
16th to endNight
34%9%13%24%17%
1502
August1st to 15thNight
34%7%17%24%14%1
1609
16th to endNight
35%7%14%26%13%1
1719
September1st to 15thNight
37%8%14%27%11%
1870
16th to endNight
43%6%14%25%9%
1837
October1st to 15thNight
53%7%10%18%9%
1964
16th to endNight
66%7%11%9%3
2154
November1st to 15thNight
60%6%14%12%41
2363
16th to endNight
70%8%12%7%
2520
December1st to 15thNight
80%8%7%2
2520
16th to endNight
81%6%7%4
2865

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%15%36%22%4
71
16th to endDay
31%5%34%23%5%
96
February1st to 15thDay
24%18%38%17%
90
16th to endDay
24%17%28%28%1
81
March1st to 15thDay
20%12%31%28%5%1
228
16th to endDay
21%7%25%30%11%3
288
April1st to 15thDay
24%5%34%23%8%2
270
16th to endDay
25%427%22%15%4
270
May1st to 15thDay
21%323%28%17%4
288
16th to endDay
15%6%22%31%20%3
331
June1st to 15thDay
14%427%31%18%3
465
16th to endDay
14%227%33%17%4
495
July1st to 15thDay
14%221%35%18%8%
475
16th to endDay
13%122%33%22%6%
383
August1st to 15thDay
14%213%29%29%11%
313
16th to endDay
18%414%28%22%11%
332
September1st to 15thDay
13%5%19%27%20%13%
315
16th to endDay
20%6%16%24%22%10%
259
October1st to 15thDay
19%9%28%27%11%3
255
16th to endDay
37%10%27%19%3
228
November1st to 15thDay
20%9%26%29%10%4
75
16th to endDay
30%11%33%21%3
60
December1st to 15thDay
26%23%31%13%5%
60
16th to endDay
40%23%31%4
64
January1st to 15thNight
27%16%33%17%3
900
16th to endNight
21%13%33%23%6%
803
February1st to 15thNight
21%14%35%22%5%
704
16th to endNight
20%10%32%28%7%
631
March1st to 15thNight
20%11%37%23%7%
720
16th to endNight
19%6%30%28%13%1
768
April1st to 15thNight
22%9%30%29%7%1
663
16th to endNight
22%5%27%27%15%1
540
May1st to 15thNight
18%319%36%18%2
531
16th to endNight
14%224%34%22%1
375
June1st to 15thNight
14%424%36%18%2
360
16th to endNight
11%221%38%24%
360
July1st to 15thNight
10%117%42%23%2
340
16th to endNight
8%220%39%25%3
530
August1st to 15thNight
11%119%33%29%3
539
16th to endNight
12%316%32%28%5%
573
September1st to 15thNight
15%420%31%17%9%
717
16th to endNight
16%6%19%29%22%6%
665
October1st to 15thNight
23%8%26%25%13%2
660
16th to endNight
35%11%28%20%4
704
November1st to 15thNight
24%12%31%20%10%1
700
16th to endNight
32%15%27%19%5%
720
December1st to 15thNight
30%20%32%13%2
720
16th to endNight
30%16%32%15%4
945
Page generated at 2017-09-18 08:38:24. Version ac04

Copyright 2017 A. Danko


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