Orillia
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Orillia clear sky chart from 2005-11-06 to 2024-02-25.

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%
22863
11%
80239
9%
22775
37%
22775
14%
59165

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 10thNight
14%
749
4%
4423
3%
737
20%
737
4%
3744
January11th to 20thNight
16%
756
6%
4266
3%
740
21%
740
4%
3459
January21st to endNight
24%
830
5%
4520
6%
814
28%
814
6%
3617
February1st to 10thNight
16%
760
7%
2470
4%
760
21%
760
8%
2009
February11th to 20thNight
21%
740
11%
2405
5%
740
29%
740
12%
1825
February21st to endNight
22%
611
10%
1953
4%
611
30%
611
13%
1479
March1st to 10thNight
25%
720
15%
1980
8%
720
31%
720
19%
1436
March11th to 20thNight
26%
720
16%
1980
8%
720
34%
720
18%
1446
March21st to endNight
32%
792
17%
2178
9%
792
38%
792
22%
1532
April1st to 10thNight
26%
720
13%
1828
5%
720
30%
720
19%
1396
April11th to 20thNight
34%
641
19%
1705
9%
641
39%
641
25%
1195
April21st to endNight
32%
540
15%
1620
8%
540
37%
540
18%
1164
May1st to 10thNight
44%
518
16%
1598
12%
518
48%
518
24%
1045
May11th to 20thNight
43%
354
21%
1416
19%
354
53%
354
22%
822
May21st to endNight
52%
388
16%
1551
19%
388
60%
388
27%
854
June1st to 10thNight
43%
360
12%
1440
12%
360
52%
360
19%
884
June11th to 20thNight
51%
360
15%
1328
17%
360
58%
360
26%
784
June21st to endNight
50%
360
12%
1260
14%
360
53%
360
21%
814
July1st to 10thNight
62%
350
18%
1238
21%
350
67%
350
33%
662
July11th to 20thNight
56%
348
18%
1392
25%
348
61%
348
27%
768
July21st to endNight
57%
513
16%
1599
15%
485
60%
485
30%
945
August1st to 10thNight
61%
537
17%
1600
13%
534
64%
534
32%
953
August11th to 20thNight
64%
534
20%
1598
13%
534
68%
534
32%
976
August21st to endNight
52%
661
17%
1849
10%
661
54%
661
27%
1229
September1st to 10thNight
52%
720
15%
1800
8%
720
55%
720
32%
1196
September11th to 20thNight
53%
720
22%
1894
14%
720
56%
720
33%
1200
September21st to endNight
46%
720
20%
2020
15%
720
51%
720
25%
1361
October1st to 10thNight
35%
720
13%
2160
10%
720
40%
720
19%
1539
October11th to 20thNight
24%
720
11%
2160
7%
720
30%
720
14%
1680
October21st to endNight
20%
792
13%
2376
7%
792
27%
792
11%
1881
November1st to 10thNight
30%
740
14%
2517
11%
740
35%
740
15%
1806
November11th to 20thNight
19%
760
10%
2660
6%
760
26%
760
10%
2056
November21st to endNight
19%
760
6%
2660
4%
760
23%
760
7%
2192
December1st to 10thNight
13%
760
5%
2660
2%
760
16%
760
5%
2273
December11th to 20thNight
11%
760
6%
3272
2%
759
16%
759
5%
2665
December21st to endNight
10%
829
3%
4863
1%
817
15%
817
3%
4278

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
15%10%47%6%45%5%5%7%32%
78798
Night
15%11%5%8%7%45%5%5%6%29%
80477
TransparencyDay
51%8%12%19%10%1
78507
Night
55%7%12%17%9%1
80304
SeeingDay
18%11%27%27%13%4
13809
Night
20%11%30%28%11%1
22895

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 10thDay
16%15%9%9%8%35%44423%
2517
11th to 20thDay
11%16%7%13%10%6%6%5%5%6%17%
2680
21st to endDay
18%21%8%11%7%4344416%
3124
February1st to 10thDay
14%15%7%13%11%45%5%4419%
1710
11th to 20thDay
11%14%8%10%8%4445%6%25%
1663
21st to endDay
17%14%7%11%8%44435%23%
1395
March1st to 10thDay
13%11%49%8%45%5%45%31%
1977
11th to 20thDay
12%13%5%8%7%45%445%32%
1980
21st to endDay
18%10%37%6%2445%6%35%
2178
April1st to 10thDay
18%11%48%6%35%45%5%30%
2132
11th to 20thDay
20%10%35%5%25%45%6%36%
2217
21st to endDay
20%10%46%5%34346%34%
2340
May1st to 10thDay
18%8%46%5%35%5%6%7%34%
2359
11th to 20thDay
14%7%45%5%3445%7%42%
2478
21st to endDay
12%6%26%5%36%5%6%7%43%
2725
June1st to 10thDay
17%6%25%5%35%46%8%38%
2520
11th to 20thDay
12%5%25%5%35%5%7%9%40%
2625
21st to endDay
15%6%35%5%445%5%9%39%
2700
July1st to 10thDay
9%425%5%45%46%10%46%
2682
11th to 20thDay
11%5%36%5%45%6%6%9%42%
2520
21st to endDay
10%5%35%6%46%5%7%9%38%
2621
August1st to 10thDay
11%5%25%6%345%7%9%43%
2327
11th to 20thDay
10%6%25%5%36%6%7%9%41%
2303
21st to endDay
10%7%26%5%45%6%7%8%40%
2489
September1st to 10thDay
14%6%26%6%4445%8%40%
2160
11th to 20thDay
13%5%26%5%35%5%5%7%44%
2063
21st to endDay
15%6%36%6%46%6%6%6%37%
1940
October1st to 10thDay
18%9%36%6%35%46%7%32%
1800
11th to 20thDay
22%10%48%6%5%6%46%5%25%
1800
21st to endDay
25%11%5%8%7%445%5%5%21%
1980
November1st to 10thDay
17%11%5%7%7%35%6%6%7%26%
1555
11th to 20thDay
17%12%6%8%7%46%7%5%7%22%
1520
21st to endDay
19%16%6%8%7%47%6%46%17%
1520
December1st to 10thDay
15%18%9%11%9%46%45%5%14%
1520
11th to 20thDay
18%15%6%8%7%45%5%47%22%
1906
21st to endDay
27%17%7%12%7%3444313%
2772
January1st to 10thNight
16%19%8%12%9%45%45%5%13%
4429
11th to 20thNight
14%12%7%12%12%5%6%445%18%
4276
21st to endNight
18%16%7%10%7%445%5%5%18%
4532
February1st to 10thNight
12%16%6%12%10%46%5%5%6%17%
2470
11th to 20thNight
12%13%6%11%7%36%5%5%6%25%
2403
21st to endNight
14%14%5%9%7%45%5%5%5%26%
1953
March1st to 10thNight
14%11%5%8%6%35%446%34%
1970
11th to 20thNight
13%11%6%8%6%45%445%34%
1979
21st to endNight
15%9%37%6%345%5%6%37%
2178
April1st to 10thNight
19%11%47%6%4445%6%30%
1828
11th to 20thNight
16%8%46%5%35%6%5%6%38%
1705
21st to endNight
17%9%38%6%35%45%6%33%
1620
May1st to 10thNight
17%6%35%6%345%6%8%38%
1598
11th to 20thNight
14%6%35%435%46%8%44%
1415
21st to endNight
11%424435%45%9%49%
1550
June1st to 10thNight
14%6%46%5%35%5%6%8%40%
1440
11th to 20thNight
9%6%26%5%345%6%9%44%
1328
21st to endNight
12%7%27%6%35%5%5%8%39%
1260
July1st to 10thNight
7%4345%3445%6%55%
1273
11th to 20thNight
10%6%25%5%35%46%9%47%
1440
21st to endNight
9%434435%5%6%9%46%
1693
August1st to 10thNight
8%5%15%5%45%46%8%49%
1611
11th to 20thNight
6%425%5%45%5%6%8%50%
1598
21st to endNight
13%5%25%5%45%6%6%7%43%
1849
September1st to 10thNight
9%5%26%5%35%5%6%8%45%
1800
11th to 20thNight
12%5%245%245%5%8%48%
1894
21st to endNight
15%7%36%5%3445%7%42%
2020
October1st to 10thNight
18%6%36%6%45%6%5%7%34%
2160
11th to 20thNight
20%11%48%6%35%45%6%26%
2160
21st to endNight
22%9%49%7%45%5%5%6%24%
2376
November1st to 10thNight
17%10%47%6%45%5%5%6%32%
2517
11th to 20thNight
16%14%48%6%5%5%5%6%7%24%
2660
21st to endNight
19%13%5%8%7%46%6%6%7%19%
2660
December1st to 10thNight
19%14%7%12%7%5%5%5%5%5%16%
2660
11th to 20thNight
16%17%6%11%7%45%46%6%17%
3288
21st to endNight
26%19%7%12%7%3443410%
4884

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 10thDay
64%7%14%9%6%
2518
11th to 20thDay
70%7%10%8%5%
2680
21st to endDay
70%8%8%8%5%1
3124
February1st to 10thDay
68%7%9%13%41
1710
11th to 20thDay
59%7%10%15%8%1
1672
21st to endDay
66%5%9%14%7%
1395
March1st to 10thDay
53%8%14%15%9%1
1980
11th to 20thDay
52%7%10%17%11%2
1980
21st to endDay
49%5%10%17%15%3
2178
April1st to 10thDay
55%6%10%19%10%1
2132
11th to 20thDay
48%6%10%22%14%1
2217
21st to endDay
51%6%10%19%12%3
2340
May1st to 10thDay
48%7%10%20%13%2
2359
11th to 20thDay
42%7%9%26%14%1
2482
21st to endDay
38%9%14%22%14%3
2725
June1st to 10thDay
43%7%12%24%13%
2520
11th to 20thDay
38%8%13%24%15%1
2625
21st to endDay
41%8%15%23%12%1
2700
July1st to 10thDay
32%9%14%26%17%1
2609
11th to 20thDay
36%8%16%29%10%1
2445
21st to endDay
40%9%13%26%11%1
2474
August1st to 10thDay
35%10%17%24%12%2
2314
11th to 20thDay
36%10%18%25%11%
2303
21st to endDay
38%10%16%25%11%1
2489
September1st to 10thDay
41%6%14%28%10%1
2160
11th to 20thDay
37%7%15%29%11%
2063
21st to endDay
45%9%13%25%7%
1940
October1st to 10thDay
51%7%13%18%10%1
1800
11th to 20thDay
59%8%13%15%5%1
1800
21st to endDay
64%7%12%11%6%
1980
November1st to 10thDay
56%8%14%16%6%
1555
11th to 20thDay
59%11%12%12%5%1
1520
21st to endDay
67%10%11%10%2
1520
December1st to 10thDay
72%8%10%8%2
1520
11th to 20thDay
64%9%10%10%6%
1906
21st to endDay
75%7%8%8%2
2772
January1st to 10thNight
73%8%9%8%2
4429
11th to 20thNight
68%9%11%9%3
4276
21st to endNight
67%8%12%9%41
4532
February1st to 10thNight
66%7%10%13%31
2470
11th to 20thNight
59%7%12%16%6%
2405
21st to endNight
58%7%12%16%7%
1953
March1st to 10thNight
51%6%14%18%10%1
1980
11th to 20thNight
52%6%10%19%11%2
1980
21st to endNight
47%6%10%20%14%2
2178
April1st to 10thNight
55%5%9%19%10%1
1828
11th to 20thNight
46%6%9%22%15%2
1705
21st to endNight
51%7%11%14%15%1
1620
May1st to 10thNight
43%6%12%18%18%3
1598
11th to 20thNight
40%5%11%23%18%3
1416
21st to endNight
33%7%15%25%17%3
1551
June1st to 10thNight
42%7%12%23%15%2
1440
11th to 20thNight
36%7%13%24%19%1
1328
21st to endNight
43%7%14%22%13%1
1260
July1st to 10thNight
28%8%13%27%22%2
1238
11th to 20thNight
34%6%14%30%15%
1392
21st to endNight
33%8%14%28%15%1
1599
August1st to 10thNight
32%8%19%28%14%
1600
11th to 20thNight
32%9%17%24%17%1
1598
21st to endNight
39%9%14%26%11%1
1849
September1st to 10thNight
35%10%16%26%12%1
1800
11th to 20thNight
34%8%14%30%13%
1894
21st to endNight
43%7%13%27%10%
2020
October1st to 10thNight
49%9%13%18%11%1
2160
11th to 20thNight
58%8%12%18%5%
2160
21st to endNight
61%8%10%13%8%
2376
November1st to 10thNight
52%8%13%18%8%
2517
11th to 20thNight
59%9%12%13%6%1
2660
21st to endNight
65%10%13%10%2
2660
December1st to 10thNight
71%9%10%8%2
2660
11th to 20thNight
68%8%12%10%3
3288
21st to endNight
79%5%7%7%2
4884

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 10thDay
17%21%37%17%8%2
180
11th to 20thDay
20%19%36%18%6%1
225
21st to endDay
26%12%30%25%6%1
297
February1st to 10thDay
23%20%37%15%4
270
11th to 20thDay
18%19%38%23%2
270
21st to endDay
26%25%26%23%
218
March1st to 10thDay
20%11%40%25%4
420
11th to 20thDay
15%19%35%26%6%
420
21st to endDay
27%10%33%21%10%
462
April1st to 10thDay
18%13%36%24%8%1
420
11th to 20thDay
25%13%26%23%9%4
412
21st to endDay
23%12%30%25%8%2
420
May1st to 10thDay
23%8%28%28%11%3
423
11th to 20thDay
17%5%28%31%17%3
447
21st to endDay
15%6%23%34%18%5%
485
June1st to 10thDay
18%5%26%34%15%2
450
11th to 20thDay
14%7%23%35%17%5%
555
21st to endDay
15%6%26%36%14%3
630
July1st to 10thDay
9%5%20%38%22%6%
604
11th to 20thDay
14%321%34%20%8%
444
21st to endDay
8%423%41%18%6%
488
August1st to 10thDay
12%418%34%24%8%
446
11th to 20thDay
13%415%33%27%9%
439
21st to endDay
12%8%21%29%23%7%
495
September1st to 10thDay
13%7%23%30%19%8%
450
11th to 20thDay
12%5%22%28%23%10%
450
21st to endDay
14%10%28%23%20%4
450
October1st to 10thDay
21%10%27%23%13%6%
450
11th to 20thDay
22%18%30%23%5%1
450
21st to endDay
28%16%31%20%5%
495
November1st to 10thDay
23%22%23%24%8%
226
11th to 20thDay
19%23%33%19%5%1
180
21st to endDay
24%18%40%16%1
180
December1st to 10thDay
22%24%35%16%4
180
11th to 20thDay
25%24%30%16%41
180
21st to endDay
28%22%35%13%2
198
January1st to 10thNight
24%19%33%19%5%1
760
11th to 20thNight
27%13%32%23%5%1
760
21st to endNight
20%10%31%31%7%1
836
February1st to 10thNight
20%12%40%24%3
760
11th to 20thNight
18%13%38%26%6%
743
21st to endNight
23%13%35%25%4
611
March1st to 10thNight
20%13%35%28%4
720
11th to 20thNight
18%13%38%26%5%1
720
21st to endNight
20%9%31%29%10%
792
April1st to 10thNight
25%10%31%28%6%
720
11th to 20thNight
20%10%30%27%12%1
641
21st to endNight
19%9%31%29%12%
540
May1st to 10thNight
20%5%22%36%15%2
518
11th to 20thNight
19%5%26%36%13%1
354
21st to endNight
12%326%40%19%
389
June1st to 10thNight
15%6%29%36%14%1
360
11th to 20thNight
12%5%26%39%17%1
360
21st to endNight
13%7%23%39%17%1
360
July1st to 10thNight
8%419%45%23%2
350
11th to 20thNight
11%6%21%40%21%2
348
21st to endNight
11%322%41%23%1
513
August1st to 10thNight
11%318%38%28%2
537
11th to 20thNight
5%420%37%30%4
534
21st to endNight
13%5%23%32%24%2
661
September1st to 10thNight
12%5%24%33%21%4
720
11th to 20thNight
13%5%22%32%21%6%
720
21st to endNight
18%8%21%31%17%5%
720
October1st to 10thNight
20%8%32%25%14%2
720
11th to 20thNight
24%14%32%22%8%1
720
21st to endNight
27%15%31%22%4
792
November1st to 10thNight
23%14%29%23%9%1
740
11th to 20thNight
23%18%34%18%6%1
760
21st to endNight
27%17%32%20%4
760
December1st to 10thNight
27%21%32%16%4
760
11th to 20thNight
23%18%38%15%41
760
21st to endNight
31%15%35%18%2
836
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