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 2018-01-20.

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%
15693
10%
48403
7%
15656
35%
15656
14%
36887

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
12%
971
2%
2838
1%
970
13%
970
4%
2587
January16th to endNight
16%
826
3%
2598
2%
826
17%
826
5%
2327
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
32%
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
51%
374
15%
1497
13%
374
60%
374
22%
880
June1st to 15thNight
48%
360
12%
1287
12%
360
54%
360
22%
813
June16th to endNight
55%
360
13%
1260
14%
360
60%
360
26%
765
July1st to 15thNight
64%
340
17%
1190
20%
340
68%
340
35%
632
July16th to endNight
60%
530
14%
1502
14%
497
60%
497
29%
935
August1st to 15thNight
59%
539
16%
1609
12%
536
62%
536
30%
987
August16th to endNight
58%
573
18%
1719
14%
573
60%
573
30%
1071
September1st to 15thNight
53%
717
16%
1870
10%
717
56%
717
30%
1248
September16th to endNight
50%
717
19%
1980
15%
717
52%
717
26%
1336
October1st to 15thNight
35%
720
13%
2143
10%
720
39%
720
17%
1586
October16th to endNight
20%
768
7%
2350
4%
768
24%
768
10%
1934
November1st to 15thNight
24%
760
10%
2565
10%
760
27%
760
11%
2010
November16th to endNight
18%
780
5%
2730
4%
780
20%
780
6%
2325
December1st to 15thNight
10%
780
1%
2730
0%
780
11%
780
3%
2516
December16th to endNight
8%
1024
2%
3104
0%
1024
10%
1024
3%
2851

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%
49116
Night
17%11%5%8%6%34446%27%
48574
Cloud CoverDay
15%10%47%5%3445%6%31%
49126
Night
16%11%5%8%6%34446%27%
48578
TransparencyDay
52%6%12%18%9%
48805
Night
57%7%11%15%8%
48403
SeeingDay
19%6%24%27%15%5%
6146
Night
21%9%27%26%12%2
15701

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%344337%
1427
16th to endDay
14%18%10%14%10%5%443310%
1728
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
17%5%25%43446%7%38%
1980
October1st to 15thDay
21%10%36%5%34335%31%
1816
16th to endDay
31%13%47%5%2334418%
1872
November1st to 15thDay
20%15%46%7%345%46%20%
1623
16th to endDay
22%21%6%8%6%345%3413%
1560
December1st to 15thDay
18%24%10%13%7%243347%
1560
16th to endDay
19%24%9%11%8%343347%
1469
January1st to 15thNight
20%18%8%13%9%344448%
2838
16th to endNight
14%17%9%14%9%34445%11%
2598
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%34446%41%
1980
October1st to 15thNight
21%8%36%5%3446%6%30%
2143
16th to endNight
28%11%37%6%34346%19%
2350
November1st to 15thNight
20%13%48%6%35%446%22%
2565
16th to endNight
24%17%5%7%5%33445%16%
2730
December1st to 15thNight
19%24%9%12%5%344338%
2730
16th to endNight
21%21%9%12%8%342339%
3104

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%343337%
1427
16th to endDay
13%19%9%15%10%4443310%
1728
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
16%6%35%5%2446%7%37%
1980
October1st to 15thDay
20%9%37%6%23435%31%
1816
16th to endDay
32%11%48%43334418%
1872
November1st to 15thDay
18%15%47%7%35%45%6%20%
1623
16th to endDay
21%20%5%8%6%35%44413%
1560
December1st to 15thDay
18%23%9%11%9%334338%
1560
16th to endDay
19%24%8%12%8%442346%
1469
January1st to 15thNight
20%17%7%13%10%35%4448%
2838
16th to endNight
14%17%9%13%9%4445%5%11%
2598
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%
1980
October1st to 15thNight
20%7%37%5%35%45%6%30%
2143
16th to endNight
26%11%47%6%34346%19%
2350
November1st to 15thNight
18%13%48%7%3445%5%23%
2565
16th to endNight
22%18%5%8%5%34345%17%
2730
December1st to 15thNight
18%23%9%11%7%25%3448%
2730
16th to endNight
20%20%9%13%8%343338%
3104

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%5%4
1428
16th to endDay
79%5%8%31
1728
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
43%7%14%25%8%
1980
October1st to 15thDay
55%5%10%18%9%
1816
16th to endDay
70%5%11%9%3
1872
November1st to 15thDay
63%8%11%10%5%
1623
16th to endDay
74%8%10%5%1
1560
December1st to 15thDay
82%8%5%2
1560
16th to endDay
83%5%7%3
1469
January1st to 15thNight
79%7%8%31
2838
16th to endNight
75%8%9%41
2598
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
42%6%14%26%9%
1980
October1st to 15thNight
53%7%9%19%9%
2143
16th to endNight
65%7%12%10%3
2350
November1st to 15thNight
61%7%13%12%4
2565
16th to endNight
70%9%12%6%1
2730
December1st to 15thNight
80%8%7%2
2730
16th to endNight
81%6%7%3
3104

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%16%36%21%3
107
16th to endDay
28%8%33%24%4
109
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
18%6%15%22%25%10%
314
October1st to 15thDay
19%10%27%26%11%4
315
16th to endDay
35%12%27%21%3
288
November1st to 15thDay
25%10%27%25%7%2
113
16th to endDay
27%13%37%17%3
90
December1st to 15thDay
22%25%34%13%4
90
16th to endDay
35%18%36%9%
96
January1st to 15thNight
26%16%33%18%4
975
16th to endNight
21%14%32%23%6%
826
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
15%6%18%28%23%6%
717
October1st to 15thNight
24%7%26%25%12%3
720
16th to endNight
34%11%28%20%4
768
November1st to 15thNight
25%12%30%20%9%1
760
16th to endNight
32%15%28%18%5%
780
December1st to 15thNight
29%19%34%13%2
780
16th to endNight
29%16%33%16%4
1024
Page generated at 2018-01-21 12:19:33. Version ac04

Copyright 2018 A. Danko


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