Niagara
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Niagara clear sky chart from 2005-11-05 to 2017-05-01.

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
34%
14495
12%
45709
9%
14457
38%
14457
15%
33680

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%
717
6%
2475
3%
716
16%
716
5%
2113
January16th to endNight
13%
768
6%
2496
2%
768
17%
768
5%
2163
February1st to 15thNight
13%
704
5%
2287
2%
701
17%
701
6%
1930
February16th to endNight
20%
631
7%
2009
3%
631
24%
631
8%
1650
March1st to 15thNight
23%
720
11%
1980
6%
720
28%
720
13%
1576
March16th to endNight
35%
768
19%
2112
11%
768
42%
768
21%
1513
April1st to 15thNight
28%
718
13%
1811
5%
718
32%
718
19%
1369
April16th to endNight
43%
588
20%
1668
10%
588
49%
588
26%
1127
May1st to 15thNight
48%
449
16%
1445
14%
449
53%
449
23%
963
May16th to endNight
52%
342
17%
1369
18%
342
60%
342
22%
802
June1st to 15thNight
47%
330
13%
1320
15%
330
55%
330
19%
841
June16th to endNight
56%
330
11%
1320
16%
330
60%
330
23%
786
July1st to 15thNight
60%
310
17%
1240
24%
310
64%
310
30%
646
July16th to endNight
63%
449
14%
1398
15%
418
64%
418
30%
832
August1st to 15thNight
65%
494
16%
1474
14%
491
66%
491
29%
925
August16th to endNight
63%
588
21%
1638
14%
588
65%
588
36%
998
September1st to 15thNight
56%
660
20%
1650
11%
660
60%
660
31%
1112
September16th to endNight
55%
657
20%
1839
15%
657
57%
657
28%
1205
October1st to 15thNight
41%
660
17%
1980
16%
660
45%
660
20%
1387
October16th to endNight
22%
704
9%
2112
5%
704
28%
704
11%
1663
November1st to 15thNight
34%
700
17%
2358
16%
700
39%
700
17%
1623
November16th to endNight
23%
720
10%
2520
8%
720
27%
720
9%
1936
December1st to 15thNight
14%
720
4%
2520
2%
720
16%
720
5%
2158
December16th to endNight
12%
768
3%
2688
1%
768
15%
768
4%
2362

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%3445%7%33%
46048
Night
17%10%47%6%34446%30%
45889
Cloud CoverDay
15%8%36%6%3445%7%33%
46058
Night
16%10%47%6%34446%30%
45893
TransparencyDay
50%7%12%18%10%
45746
Night
53%7%10%17%9%
45709
SeeingDay
19%7%22%25%17%7%
4836
Night
22%9%26%27%13%1
14499

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%14%6%9%9%46%445%14%
1462
16th to endDay
14%16%7%13%11%6%445%411%
1728
February1st to 15thDay
16%16%6%12%8%35%6%4315%
1575
16th to endDay
16%13%5%10%9%46%346%19%
1462
March1st to 15thDay
17%10%5%10%7%35%345%25%
1969
16th to endDay
16%7%35%5%34446%37%
2112
April1st to 15thDay
20%9%35%5%33346%34%
2137
16th to endDay
17%7%25%423346%41%
2303
May1st to 15thDay
13%6%35%5%345%6%7%39%
2185
16th to endDay
10%4235%35%46%8%44%
2394
June1st to 15thDay
13%6%35%425%45%8%40%
2310
16th to endDay
12%313425%5%6%10%42%
2310
July1st to 15thDay
6%4244245%7%9%48%
2310
16th to endDay
10%415%5%345%7%10%40%
2355
August1st to 15thDay
7%4245%345%7%10%44%
2145
16th to endDay
10%41343446%8%48%
2201
September1st to 15thDay
16%5%245%235%6%8%40%
1980
16th to endDay
13%5%35%4345%5%6%40%
1787
October1st to 15thDay
19%7%26%5%245%47%33%
1650
16th to endDay
24%10%46%7%24435%24%
1760
November1st to 15thDay
11%10%47%5%445%47%33%
1497
16th to endDay
20%13%47%6%2445%6%23%
1440
December1st to 15thDay
18%18%7%9%6%35%44416%
1440
16th to endDay
21%18%7%12%5%35%45%411%
1536
January1st to 15thNight
21%17%7%9%7%3433416%
2475
16th to endNight
15%16%7%13%9%5%45%4412%
2496
February1st to 15thNight
16%16%7%11%8%35%43418%
2285
16th to endNight
16%13%7%10%7%35%45%5%19%
2009
March1st to 15thNight
20%10%5%9%7%3444424%
1968
16th to endNight
16%9%46%42434437%
2112
April1st to 15thNight
21%9%35%5%35%34433%
1811
16th to endNight
14%425%435%45%5%43%
1668
May1st to 15thNight
17%5%345%3446%8%36%
1445
16th to endNight
12%5%25%43446%6%45%
1367
June1st to 15thNight
14%6%146%35%5%6%8%37%
1320
16th to endNight
10%325%5%35%6%5%9%42%
1320
July1st to 15thNight
5%315%42445%6%54%
1320
16th to endNight
8%3145%35%5%7%8%46%
1503
August1st to 15thNight
9%5%145%35%5%6%7%44%
1485
16th to endNight
9%32442345%6%51%
1638
September1st to 15thNight
16%425%323446%45%
1650
16th to endNight
15%5%25%42445%7%43%
1839
October1st to 15thNight
20%7%36%433346%36%
1980
16th to endNight
26%10%35%5%35%45%5%24%
2112
November1st to 15thNight
15%8%36%5%35%447%35%
2358
16th to endNight
22%11%5%7%5%345%5%5%24%
2520
December1st to 15thNight
23%18%6%9%6%35%435%14%
2520
16th to endNight
22%17%7%10%7%35%44411%
2688

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
19%14%6%12%8%35%44415%
1462
16th to endDay
14%15%7%13%12%5%5%44411%
1728
February1st to 15thDay
16%17%7%11%7%36%5%4415%
1575
16th to endDay
17%13%5%9%10%46%44418%
1462
March1st to 15thDay
17%11%5%10%8%445%4424%
1980
16th to endDay
16%8%35%6%34446%36%
2111
April1st to 15thDay
20%8%35%434446%34%
2137
16th to endDay
17%7%25%423346%40%
2303
May1st to 15thDay
13%6%26%43446%7%38%
2185
16th to endDay
9%5%244345%6%7%43%
2394
June1st to 15thDay
13%5%35%435%35%9%39%
2310
16th to endDay
13%3134245%6%10%42%
2310
July1st to 15thDay
6%42443447%9%47%
2310
16th to endDay
11%3145%35%6%7%10%40%
2355
August1st to 15thDay
8%4244445%7%10%44%
2145
16th to endDay
10%41442445%9%46%
2201
September1st to 15thDay
16%5%2443345%7%41%
1980
16th to endDay
13%6%35%4345%6%6%39%
1787
October1st to 15thDay
20%6%36%435%446%33%
1650
16th to endDay
25%10%28%6%34445%23%
1760
November1st to 15thDay
11%11%46%7%346%48%31%
1497
16th to endDay
19%12%5%8%6%245%45%23%
1440
December1st to 15thDay
18%17%8%9%7%2435%5%15%
1440
16th to endDay
20%18%7%11%7%245%4412%
1536
January1st to 15thNight
20%17%7%10%8%3433416%
2475
16th to endNight
15%16%7%12%10%45%445%13%
2496
February1st to 15thNight
16%15%7%13%8%3444417%
2278
16th to endNight
15%13%7%11%8%3445%5%18%
2009
March1st to 15thNight
20%11%5%9%7%25%445%24%
1980
16th to endNight
17%7%5%7%5%15%43437%
2112
April1st to 15thNight
22%8%46%5%3434433%
1811
16th to endNight
14%5%25%435%45%6%42%
1668
May1st to 15thNight
16%6%25%5%2447%8%36%
1444
16th to endNight
12%425%425%45%6%45%
1367
June1st to 15thNight
14%425%6%35%5%5%8%37%
1320
16th to endNight
9%4245%45%6%5%7%43%
1320
July1st to 15thNight
5%333425%45%7%53%
1320
16th to endNight
8%224436%5%6%9%45%
1503
August1st to 15thNight
9%5%246%35%5%6%7%44%
1485
16th to endNight
9%42442336%6%51%
1638
September1st to 15thNight
16%5%25%324446%45%
1650
16th to endNight
14%5%25%424447%43%
1839
October1st to 15thNight
20%7%35%434336%36%
1980
16th to endNight
26%10%36%5%35%45%5%23%
2112
November1st to 15thNight
14%9%36%5%35%447%35%
2358
16th to endNight
21%12%47%5%345%5%5%23%
2520
December1st to 15thNight
23%16%6%9%6%25%445%15%
2520
16th to endNight
21%17%7%10%7%35%44411%
2688

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
70%8%8%10%2
1463
16th to endDay
75%7%8%6%1
1728
February1st to 15thDay
71%9%7%10%1
1577
16th to endDay
67%6%9%11%3
1462
March1st to 15thDay
62%6%11%14%4
1980
16th to endDay
49%7%10%22%9%1
2112
April1st to 15thDay
52%5%12%18%11%
2137
16th to endDay
45%410%20%16%2
2303
May1st to 15thDay
42%7%11%23%13%
2185
16th to endDay
37%7%14%24%14%1
2398
June1st to 15thDay
42%7%13%22%11%1
2310
16th to endDay
36%8%15%24%14%
2310
July1st to 15thDay
31%8%12%25%21%1
2161
16th to endDay
38%10%15%22%12%1
2197
August1st to 15thDay
34%10%16%22%14%1
2132
16th to endDay
34%7%12%30%12%1
2201
September1st to 15thDay
43%7%12%24%12%
1980
16th to endDay
41%8%12%24%12%
1787
October1st to 15thDay
51%6%10%18%12%
1650
16th to endDay
62%7%13%12%3
1760
November1st to 15thDay
51%7%14%16%8%1
1497
16th to endDay
60%7%12%12%6%
1440
December1st to 15thDay
68%9%12%7%1
1440
16th to endDay
74%7%9%7%1
1536
January1st to 15thNight
73%6%8%8%3
2475
16th to endNight
72%8%9%7%2
2496
February1st to 15thNight
69%8%9%10%2
2287
16th to endNight
65%8%10%10%5%
2009
March1st to 15thNight
62%5%10%16%4
1980
16th to endNight
49%6%7%21%13%1
2112
April1st to 15thNight
55%49%18%12%
1811
16th to endNight
41%7%9%22%16%3
1668
May1st to 15thNight
44%6%11%22%13%1
1445
16th to endNight
37%7%11%24%16%2
1369
June1st to 15thNight
43%7%10%20%15%1
1320
16th to endNight
37%8%13%22%17%1
1320
July1st to 15thNight
30%6%12%25%23%2
1240
16th to endNight
32%8%15%21%17%4
1398
August1st to 15thNight
34%9%15%24%14%1
1474
16th to endNight
31%6%10%32%15%1
1638
September1st to 15thNight
39%6%13%24%15%1
1650
16th to endNight
39%6%10%26%15%
1839
October1st to 15thNight
48%6%9%20%13%1
1980
16th to endNight
59%8%12%13%5%
2112
November1st to 15thNight
48%7%12%18%12%
2358
16th to endNight
59%7%12%14%4
2520
December1st to 15thNight
70%8%10%7%2
2520
16th to endNight
75%8%9%6%1
2688

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%20%32%12%10%3
65
16th to endDay
31%17%29%16%5%
96
February1st to 15thDay
21%22%41%14%1
90
16th to endDay
25%11%36%20%7%
108
March1st to 15thDay
26%12%30%22%8%
270
16th to endDay
23%7%28%28%7%3
288
April1st to 15thDay
24%9%30%25%7%2
270
16th to endDay
24%426%23%14%6%
270
May1st to 15thDay
19%321%25%21%8%
229
16th to endDay
12%425%27%20%9%
267
June1st to 15thDay
19%421%30%21%3
255
16th to endDay
18%317%28%27%5%
255
July1st to 15thDay
10%312%33%26%13%
245
16th to endDay
13%218%31%22%11%
270
August1st to 15thDay
11%115%30%25%16%
253
16th to endDay
13%410%24%28%19%
268
September1st to 15thDay
14%315%24%27%16%
255
16th to endDay
17%5%16%22%25%13%
254
October1st to 15thDay
21%8%20%18%22%8%
255
16th to endDay
35%10%26%21%6%
272
November1st to 15thDay
11%12%26%33%10%5%
117
16th to endDay
21%18%23%16%20%
60
December1st to 15thDay
18%28%31%15%6%
60
16th to endDay
23%31%35%9%
64
January1st to 15thNight
30%18%30%15%4
720
16th to endNight
26%13%34%20%5%
768
February1st to 15thNight
23%18%32%21%4
704
16th to endNight
24%13%30%26%4
631
March1st to 15thNight
27%10%31%23%6%
720
16th to endNight
19%7%30%29%11%1
768
April1st to 15thNight
26%8%29%27%6%
718
16th to endNight
16%5%28%33%14%1
588
May1st to 15thNight
18%420%37%17%2
449
16th to endNight
13%423%36%19%2
343
June1st to 15thNight
16%127%34%18%1
330
16th to endNight
10%322%45%17%
330
July1st to 15thNight
8%220%41%24%2
310
16th to endNight
10%118%44%22%2
449
August1st to 15thNight
11%212%37%30%5%
494
16th to endNight
12%115%35%30%5%
588
September1st to 15thNight
17%316%31%26%4
660
16th to endNight
17%316%29%24%7%
657
October1st to 15thNight
23%6%19%27%19%2
660
16th to endNight
33%10%27%23%5%
704
November1st to 15thNight
20%8%31%23%14%1
700
16th to endNight
28%14%27%19%9%
720
December1st to 15thNight
34%16%27%18%3
720
16th to endNight
28%16%32%17%3
768
Page generated at 2017-05-02 08:43:28. Version ac04

Copyright 2017 A. Danko


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