St Catharines
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the St Catharines clear sky chart from 2005-11-05 to 2017-12-20.

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
36%
15246
13%
48105
9%
15209
40%
15209
17%
34513

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%
716
7%
2464
3%
716
17%
716
6%
2060
January16th to endNight
15%
768
7%
2496
2%
768
20%
768
7%
2068
February1st to 15thNight
15%
703
6%
2287
2%
701
20%
701
8%
1864
February16th to endNight
21%
631
7%
2005
4%
631
26%
631
10%
1612
March1st to 15thNight
24%
720
12%
1980
6%
720
29%
720
14%
1563
March16th to endNight
36%
768
19%
2112
11%
768
42%
768
23%
1490
April1st to 15thNight
29%
718
14%
1814
6%
718
33%
718
20%
1364
April16th to endNight
44%
582
20%
1662
10%
582
50%
582
27%
1101
May1st to 15thNight
47%
498
15%
1578
12%
498
52%
498
22%
1065
May16th to endNight
52%
374
17%
1497
19%
374
59%
374
22%
896
June1st to 15thNight
48%
360
13%
1440
14%
360
56%
360
20%
900
June16th to endNight
58%
360
12%
1440
16%
360
62%
360
23%
856
July1st to 15thNight
64%
340
17%
1360
24%
340
67%
340
30%
717
July16th to endNight
66%
499
15%
1531
16%
467
67%
467
31%
903
August1st to 15thNight
67%
539
15%
1609
13%
536
68%
536
32%
975
August16th to endNight
64%
637
23%
1783
15%
637
67%
637
36%
1074
September1st to 15thNight
56%
720
20%
1803
12%
720
60%
720
33%
1195
September16th to endNight
58%
717
22%
2010
18%
717
60%
717
31%
1270
October1st to 15thNight
42%
720
16%
2160
15%
720
46%
720
22%
1483
October16th to endNight
26%
768
12%
2304
8%
768
31%
768
14%
1721
November1st to 15thNight
34%
760
17%
2555
15%
760
39%
760
18%
1720
November16th to endNight
25%
780
11%
2730
7%
780
31%
780
11%
2042
December1st to 15thNight
15%
780
4%
2730
2%
780
17%
780
7%
2228
December16th to endNight
11%
788
5%
2755
1%
788
16%
788
5%
2346

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
14%8%36%6%35%45%7%34%
48730
Night
16%9%47%6%3445%6%32%
48286
Cloud CoverDay
14%8%36%6%35%45%7%33%
48740
Night
16%9%47%6%3445%6%32%
48290
TransparencyDay
49%7%13%19%9%
48429
Night
52%6%12%18%10%
48105
SeeingDay
18%7%23%25%17%7%
5662
Night
20%9%26%28%13%1
15252

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%6%10%9%4445%6%16%
1471
16th to endDay
13%16%6%13%11%45%445%13%
1728
February1st to 15thDay
16%17%6%10%7%45%445%16%
1575
16th to endDay
16%13%6%10%8%36%35%6%18%
1464
March1st to 15thDay
16%11%5%10%7%35%45%425%
1969
16th to endDay
15%9%35%6%34445%37%
2112
April1st to 15thDay
20%8%26%5%24446%33%
2132
16th to endDay
17%6%35%5%24346%41%
2309
May1st to 15thDay
15%6%25%5%35%45%7%37%
2373
16th to endDay
10%5%245%35%5%6%7%43%
2618
June1st to 15thDay
14%5%245%25%45%7%41%
2520
16th to endDay
12%424435%5%6%10%42%
2520
July1st to 15thDay
7%424435%5%6%10%45%
2520
16th to endDay
10%425%5%35%5%7%8%40%
2530
August1st to 15thDay
9%4245%35%6%7%11%41%
2340
16th to endDay
10%4245%2445%9%46%
2406
September1st to 15thDay
14%5%244345%5%7%41%
2156
16th to endDay
13%5%25%4345%6%8%40%
1950
October1st to 15thDay
19%6%36%6%35%45%5%34%
1800
16th to endDay
23%11%26%5%45%445%26%
1920
November1st to 15thDay
12%9%48%6%35%45%7%32%
1629
16th to endDay
19%11%47%5%35%45%6%25%
1560
December1st to 15thDay
17%16%7%8%7%34446%19%
1560
16th to endDay
20%17%7%10%6%45%436%12%
1568
January1st to 15thNight
20%14%7%10%9%3433417%
2464
16th to endNight
15%14%7%11%9%45%5%4416%
2496
February1st to 15thNight
16%16%6%10%6%36%34421%
2285
16th to endNight
16%13%5%11%7%45%445%21%
2005
March1st to 15thNight
20%10%47%7%34445%26%
1968
16th to endNight
16%9%36%5%2444438%
2112
April1st to 15thNight
20%8%37%5%24345%33%
1814
16th to endNight
13%6%25%5%26%45%6%42%
1662
May1st to 15thNight
17%6%35%5%2446%8%36%
1578
16th to endNight
11%5%245%345%5%7%44%
1495
June1st to 15thNight
13%436%436%5%5%8%38%
1440
16th to endNight
10%4145%46%5%5%8%43%
1440
July1st to 15thNight
5%3244245%5%7%54%
1440
16th to endNight
7%4144345%6%9%46%
1637
August1st to 15thNight
7%3145%35%6%6%8%46%
1620
16th to endNight
8%3244245%5%6%52%
1783
September1st to 15thNight
15%5%24423347%45%
1803
16th to endNight
13%425%42435%7%46%
2010
October1st to 15thNight
19%7%35%5%23346%38%
2160
16th to endNight
23%8%46%5%3345%6%28%
2304
November1st to 15thNight
16%8%35%5%34347%35%
2555
16th to endNight
20%11%46%5%35%5%5%6%26%
2730
December1st to 15thNight
21%16%5%8%7%34445%18%
2730
16th to endNight
21%15%8%10%7%44445%14%
2755

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
17%15%6%10%10%35%446%15%
1471
16th to endDay
14%16%5%12%11%46%45%413%
1728
February1st to 15thDay
16%17%6%11%8%45%45%6%15%
1575
16th to endDay
17%14%5%10%9%35%36%5%18%
1464
March1st to 15thDay
16%11%5%10%7%35%45%5%24%
1980
16th to endDay
15%9%35%5%35%45%5%36%
2111
April1st to 15thDay
20%8%26%5%33446%32%
2132
16th to endDay
17%6%25%5%23346%40%
2309
May1st to 15thDay
14%6%25%5%35%45%7%37%
2373
16th to endDay
9%5%25%5%35%5%6%8%42%
2618
June1st to 15thDay
13%6%25%435%45%7%41%
2520
16th to endDay
12%324425%6%6%10%41%
2520
July1st to 15thDay
7%425%435%5%7%9%45%
2520
16th to endDay
10%425%6%35%5%7%9%39%
2530
August1st to 15thDay
8%4145%347%7%11%41%
2340
16th to endDay
10%42442445%8%45%
2406
September1st to 15thDay
14%6%2443445%7%40%
2156
16th to endDay
13%5%245%35%46%8%40%
1950
October1st to 15thDay
19%6%27%5%35%45%5%34%
1800
16th to endDay
23%10%37%5%45%445%25%
1920
November1st to 15thDay
12%9%47%6%25%45%7%32%
1629
16th to endDay
19%11%47%5%35%447%25%
1560
December1st to 15thDay
17%16%6%9%7%345%46%19%
1560
16th to endDay
20%18%7%10%7%44345%12%
1568
January1st to 15thNight
20%15%7%11%8%3434317%
2464
16th to endNight
15%14%7%12%9%5%5%44416%
2496
February1st to 15thNight
16%15%6%11%6%35%44420%
2278
16th to endNight
16%13%6%10%7%35%5%5%5%20%
2005
March1st to 15thNight
20%10%48%7%34445%25%
1980
16th to endNight
16%9%36%42444438%
2112
April1st to 15thNight
20%9%46%6%2444433%
1814
16th to endNight
13%6%24435%45%6%42%
1662
May1st to 15thNight
16%6%35%5%3446%8%35%
1577
16th to endNight
11%5%246%3446%7%43%
1495
June1st to 15thNight
13%436%436%5%5%8%37%
1440
16th to endNight
9%4245%46%5%5%8%42%
1440
July1st to 15thNight
6%325%42445%7%53%
1440
16th to endNight
7%4245%35%5%5%9%46%
1637
August1st to 15thNight
7%324435%6%7%7%46%
1620
16th to endNight
8%32442445%7%51%
1783
September1st to 15thNight
14%5%15%424447%45%
1803
16th to endNight
13%5%25%43335%6%46%
2010
October1st to 15thNight
19%6%35%6%23346%37%
2160
16th to endNight
24%8%37%5%3445%6%27%
2304
November1st to 15thNight
17%7%36%444348%35%
2555
16th to endNight
20%11%5%6%6%35%5%46%26%
2730
December1st to 15thNight
21%16%6%9%6%33445%18%
2730
16th to endNight
20%15%7%10%7%44445%13%
2755

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
69%6%10%10%2
1472
16th to endDay
73%410%9%1
1728
February1st to 15thDay
69%8%9%10%1
1577
16th to endDay
66%5%12%11%3
1464
March1st to 15thDay
61%7%11%14%5%
1980
16th to endDay
49%6%10%22%9%1
2112
April1st to 15thDay
52%6%11%18%10%
2132
16th to endDay
45%5%10%20%15%2
2309
May1st to 15thDay
44%7%11%23%12%
2373
16th to endDay
37%8%14%24%13%1
2622
June1st to 15thDay
41%7%14%23%12%1
2520
16th to endDay
35%8%16%24%14%
2520
July1st to 15thDay
31%9%12%24%20%1
2371
16th to endDay
40%8%15%22%11%1
2373
August1st to 15thDay
33%10%17%22%14%1
2327
16th to endDay
34%8%11%29%13%1
2406
September1st to 15thDay
41%7%13%24%12%1
2156
16th to endDay
39%7%14%25%12%
1950
October1st to 15thDay
50%6%10%19%11%
1800
16th to endDay
59%7%14%13%4
1920
November1st to 15thDay
50%7%15%17%7%1
1629
16th to endDay
59%6%14%13%6%
1560
December1st to 15thDay
66%5%16%9%1
1560
16th to endDay
73%7%9%8%1
1568
January1st to 15thNight
71%5%8%10%3
2464
16th to endNight
70%5%11%9%2
2496
February1st to 15thNight
67%5%11%12%2
2287
16th to endNight
65%5%11%11%5%
2005
March1st to 15thNight
61%5%10%17%4
1980
16th to endNight
48%49%22%13%1
2112
April1st to 15thNight
53%5%8%19%12%
1814
16th to endNight
41%6%10%22%16%3
1662
May1st to 15thNight
44%7%10%22%13%1
1578
16th to endNight
38%7%12%23%15%2
1497
June1st to 15thNight
42%6%11%21%16%1
1440
16th to endNight
38%6%13%23%16%1
1440
July1st to 15thNight
29%6%11%25%23%2
1360
16th to endNight
33%7%15%22%17%3
1531
August1st to 15thNight
31%9%18%25%13%1
1609
16th to endNight
30%7%10%32%16%1
1783
September1st to 15thNight
37%6%13%24%15%1
1803
16th to endNight
38%411%27%16%
2010
October1st to 15thNight
48%410%21%14%
2160
16th to endNight
56%5%15%15%6%
2304
November1st to 15thNight
48%5%14%19%11%
2555
16th to endNight
57%6%14%16%4
2730
December1st to 15thNight
68%5%14%8%3
2730
16th to endNight
72%6%10%8%1
2755

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
19%20%35%8%13%1
67
16th to endDay
32%14%33%14%5%
96
February1st to 15thDay
22%18%43%15%
90
16th to endDay
21%14%33%26%3
102
March1st to 15thDay
24%14%30%23%8%
270
16th to endDay
23%5%31%30%5%4
288
April1st to 15thDay
24%11%27%25%9%2
270
16th to endDay
21%6%28%21%16%6%
270
May1st to 15thDay
21%422%23%20%6%
288
16th to endDay
13%6%24%31%17%8%
331
June1st to 15thDay
15%6%20%35%17%4
315
16th to endDay
15%323%28%24%4
315
July1st to 15thDay
11%213%33%26%12%
305
16th to endDay
10%220%30%23%12%
326
August1st to 15thDay
8%17%27%29%16%
313
16th to endDay
13%312%24%27%18%
332
September1st to 15thDay
12%216%22%30%15%
315
16th to endDay
14%315%21%25%19%
314
October1st to 15thDay
19%7%25%18%19%9%
315
16th to endDay
29%14%24%20%10%
336
November1st to 15thDay
18%9%27%30%11%2
152
16th to endDay
24%14%33%18%8%
90
December1st to 15thDay
17%24%32%18%6%
90
16th to endDay
30%23%37%6%1
72
January1st to 15thNight
28%18%30%17%5%
720
16th to endNight
23%14%34%21%5%
768
February1st to 15thNight
24%17%32%22%3
704
16th to endNight
21%14%32%27%4
631
March1st to 15thNight
25%11%32%22%7%
720
16th to endNight
19%7%29%30%11%1
768
April1st to 15thNight
23%9%29%29%7%
718
16th to endNight
16%5%28%33%14%1
582
May1st to 15thNight
18%420%35%18%2
498
16th to endNight
13%422%35%21%1
375
June1st to 15thNight
14%127%36%18%
360
16th to endNight
8%322%45%20%
360
July1st to 15thNight
10%217%44%23%2
340
16th to endNight
9%215%46%22%3
499
August1st to 15thNight
9%211%38%32%5%
539
16th to endNight
11%114%36%32%3
637
September1st to 15thNight
15%416%32%26%5%
720
16th to endNight
16%415%28%27%8%
717
October1st to 15thNight
22%6%21%25%20%2
720
16th to endNight
29%9%28%25%5%
768
November1st to 15thNight
19%8%29%26%13%1
760
16th to endNight
25%15%29%20%9%
780
December1st to 15thNight
31%15%28%19%3
780
16th to endNight
26%16%33%19%3
788
Page generated at 2017-12-21 07:04:51. Version ac04

Copyright 2017 A. Danko


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