Burlington
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Burlington clear sky chart from 2005-11-05 to 2018-10-08.

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
46%
17309
22%
51138
14%
17273
55%
17273
28%
32016

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
29%
776
24%
2522
11%
776
46%
776
23%
1519
January16th to endNight
25%
832
26%
2704
12%
832
43%
832
25%
1618
February1st to 15thNight
27%
761
22%
2482
10%
761
43%
761
24%
1481
February16th to endNight
25%
683
27%
2005
10%
683
43%
683
28%
1226
March1st to 15thNight
30%
780
26%
2145
13%
780
42%
780
28%
1342
March16th to endNight
35%
832
21%
2288
11%
832
43%
832
26%
1494
April1st to 15thNight
37%
778
24%
2014
10%
778
45%
778
33%
1248
April16th to endNight
43%
758
21%
1914
9%
758
49%
758
32%
1243
May1st to 15thNight
50%
585
19%
1755
11%
585
56%
585
28%
1120
May16th to endNight
59%
609
16%
1828
12%
609
61%
609
28%
1176
June1st to 15thNight
63%
585
15%
1755
14%
585
65%
585
29%
1128
June16th to endNight
70%
585
16%
1755
14%
585
71%
585
30%
1108
July1st to 15thNight
69%
555
15%
1665
14%
555
69%
555
29%
1054
July16th to endNight
73%
612
15%
1739
12%
579
75%
579
30%
1108
August1st to 15thNight
66%
575
17%
1715
14%
572
66%
572
25%
1172
August16th to endNight
69%
774
16%
2016
12%
774
70%
774
31%
1347
September1st to 15thNight
66%
780
23%
2008
18%
780
67%
780
33%
1335
September16th to endNight
53%
777
19%
2154
17%
777
55%
777
24%
1495
October1st to 15thNight
54%
752
27%
2255
25%
752
60%
752
31%
1395
October16th to endNight
47%
768
35%
2304
23%
768
64%
768
36%
1281
November1st to 15thNight
45%
760
28%
2281
19%
760
57%
760
33%
1330
November16th to endNight
44%
780
28%
2509
20%
780
55%
780
30%
1431
December1st to 15thNight
36%
780
23%
2621
14%
780
48%
780
24%
1625
December16th to endNight
29%
832
23%
2704
13%
832
43%
832
21%
1740

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
13%424435%5%5%7%42%
51956
Night
13%5%2442445%7%45%
51331
Cloud CoverDay
13%424435%5%5%7%42%
51966
Night
13%5%2442445%7%45%
51335
TransparencyDay
39%5%12%21%17%4
51667
Night
37%5%11%21%18%5%
51138
SeeingDay
15%6%19%23%22%11%
7120
Night
15%7%23%31%19%2
17318

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%5%24434346%44%
1746
16th to endDay
15%6%23223445%49%
1872
February1st to 15thDay
15%6%245%23347%43%
1710
16th to endDay
15%5%24433346%45%
1750
March1st to 15thDay
14%42341445%7%48%
2134
16th to endDay
16%5%24424446%43%
2288
April1st to 15thDay
11%31332435%8%51%
2264
16th to endDay
14%424425%45%6%44%
2332
May1st to 15thDay
14%5%25%435%5%5%7%39%
2526
16th to endDay
11%425%6%46%6%6%9%37%
2639
June1st to 15thDay
8%425%4345%7%10%42%
2535
16th to endDay
7%325%436%5%7%10%42%
2535
July1st to 15thDay
8%425%6%46%7%8%9%36%
2535
16th to endDay
6%5%26%6%47%7%8%11%32%
2673
August1st to 15thDay
11%425%6%46%7%8%10%32%
2487
16th to endDay
10%5%25%6%5%7%6%7%8%34%
2525
September1st to 15thDay
11%4245%3446%8%43%
2280
16th to endDay
21%6%25%4245%5%6%36%
2135
October1st to 15thDay
16%42321343451%
1875
16th to endDay
11%31333324357%
1920
November1st to 15thDay
15%413323345%51%
1907
16th to endDay
12%32442435%6%50%
1778
December1st to 15thDay
15%5%243245%46%45%
1638
16th to endDay
20%7%25%223347%41%
1872
January1st to 15thNight
15%5%24413446%47%
2522
16th to endNight
16%6%23423345%47%
2704
February1st to 15thNight
16%5%23324346%47%
2480
16th to endNight
13%5%24423447%47%
2005
March1st to 15thNight
14%5%13423346%49%
2133
16th to endNight
15%5%24424447%43%
2288
April1st to 15thNight
12%5%2442435%7%49%
2014
16th to endNight
13%4245%34446%46%
1914
May1st to 15thNight
10%425%445%46%7%43%
1755
16th to endNight
11%5%25%43446%10%41%
1826
June1st to 15thNight
9%326%425%6%6%11%39%
1755
16th to endNight
6%325%5%346%8%10%42%
1755
July1st to 15thNight
7%425%5%36%5%8%10%40%
1755
16th to endNight
5%425%5%36%7%8%12%38%
1847
August1st to 15thNight
10%5%25%6%35%6%7%9%36%
1726
16th to endNight
8%415%5%45%7%7%11%37%
2016
September1st to 15thNight
11%5%244245%6%7%45%
2008
16th to endNight
17%7%25%5%3445%6%37%
2154
October1st to 15thNight
16%6%24323235%49%
2255
16th to endNight
11%41232333358%
2304
November1st to 15thNight
14%413323335%53%
2281
16th to endNight
13%424313446%51%
2509
December1st to 15thNight
15%5%25%5%24345%44%
2621
16th to endNight
19%6%35%414446%40%
2704

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
16%5%24433346%45%
1746
16th to endDay
16%5%23224445%49%
1872
February1st to 15thDay
15%6%245%24247%43%
1710
16th to endDay
15%5%34433346%45%
1750
March1st to 15thDay
14%423324447%48%
2145
16th to endDay
16%5%24424446%43%
2287
April1st to 15thDay
11%31332345%8%51%
2264
16th to endDay
13%424425%446%44%
2332
May1st to 15thDay
14%5%35%435%5%5%7%39%
2526
16th to endDay
11%415%6%46%5%6%9%38%
2639
June1st to 15thDay
9%325%435%5%7%10%42%
2535
16th to endDay
7%425%435%6%7%11%41%
2535
July1st to 15thDay
8%425%5%47%7%8%10%35%
2535
16th to endDay
6%5%26%7%47%6%9%11%32%
2673
August1st to 15thDay
11%425%7%46%7%7%10%32%
2487
16th to endDay
10%5%26%6%5%7%6%6%8%34%
2525
September1st to 15thDay
11%4145%345%6%8%43%
2280
16th to endDay
20%6%25%42445%6%36%
2135
October1st to 15thDay
16%42431343451%
1875
16th to endDay
11%41342323457%
1920
November1st to 15thDay
15%413323345%52%
1907
16th to endDay
12%325%424346%50%
1778
December1st to 15thDay
15%5%243245%45%45%
1638
16th to endDay
20%7%25%313347%41%
1872
January1st to 15thNight
15%5%24323446%47%
2522
16th to endNight
16%6%23423345%47%
2704
February1st to 15thNight
16%5%23324345%48%
2473
16th to endNight
13%5%24323446%47%
2005
March1st to 15thNight
14%5%23423346%49%
2145
16th to endNight
16%5%25%32445%6%43%
2288
April1st to 15thNight
12%5%2442435%7%49%
2014
16th to endNight
13%5%25%334446%46%
1914
May1st to 15thNight
10%425%445%46%7%43%
1754
16th to endNight
11%5%25%4345%6%9%41%
1826
June1st to 15thNight
9%426%435%6%7%11%39%
1755
16th to endNight
6%325%5%246%8%10%42%
1755
July1st to 15thNight
8%4145%36%5%8%10%40%
1755
16th to endNight
5%425%5%26%7%8%11%38%
1847
August1st to 15thNight
10%5%25%5%36%5%7%10%36%
1726
16th to endNight
8%415%5%45%7%7%11%37%
2016
September1st to 15thNight
11%5%25%42446%7%45%
2008
16th to endNight
16%7%25%5%3445%5%37%
2154
October1st to 15thNight
15%6%24323235%49%
2255
16th to endNight
11%41232333358%
2304
November1st to 15thNight
14%413323335%53%
2281
16th to endNight
13%424314346%51%
2509
December1st to 15thNight
15%5%35%5%23345%44%
2621
16th to endNight
19%6%35%414436%40%
2704

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
41%37%20%22%4
1747
16th to endDay
38%27%23%20%8%
1872
February1st to 15thDay
41%37%23%20%4
1712
16th to endDay
40%410%21%18%4
1750
March1st to 15thDay
36%39%23%20%6%
2145
16th to endDay
42%49%21%18%4
2288
April1st to 15thDay
30%311%27%18%7%
2264
16th to endDay
38%410%18%19%7%
2332
May1st to 15thDay
41%6%14%20%13%2
2526
16th to endDay
41%6%16%23%10%1
2643
June1st to 15thDay
34%8%17%24%14%
2535
16th to endDay
34%8%16%22%15%2
2535
July1st to 15thDay
40%10%14%19%11%3
2396
16th to endDay
41%10%17%20%9%
2518
August1st to 15thDay
43%10%16%19%10%
2474
16th to endDay
43%8%16%18%11%1
2525
September1st to 15thDay
37%8%13%18%17%4
2280
16th to endDay
47%6%7%18%18%2
2135
October1st to 15thDay
37%39%25%18%4
1875
16th to endDay
31%26%25%26%7%
1920
November1st to 15thDay
34%39%18%26%7%
1907
16th to endDay
34%37%21%26%5%
1778
December1st to 15thDay
39%49%24%17%4
1638
16th to endDay
43%410%20%17%3
1872
January1st to 15thNight
37%48%17%24%6%
2522
16th to endNight
39%37%22%21%6%
2704
February1st to 15thNight
38%38%21%22%5%
2482
16th to endNight
37%39%23%20%4
2005
March1st to 15thNight
37%47%22%22%6%
2145
16th to endNight
40%5%8%23%17%4
2288
April1st to 15thNight
35%39%24%22%5%
2014
16th to endNight
38%311%19%18%8%
1914
May1st to 15thNight
38%6%12%23%16%2
1755
16th to endNight
37%7%15%25%11%1
1828
June1st to 15thNight
36%8%18%22%12%1
1755
16th to endNight
33%9%16%22%13%3
1755
July1st to 15thNight
34%9%16%22%13%3
1665
16th to endNight
33%11%20%21%11%2
1739
August1st to 15thNight
40%10%16%18%11%1
1715
16th to endNight
36%9%20%23%8%2
2016
September1st to 15thNight
35%8%13%21%16%4
2008
16th to endNight
45%6%10%16%18%2
2154
October1st to 15thNight
38%38%22%21%4
2255
16th to endNight
30%25%23%26%10%
2304
November1st to 15thNight
33%37%18%25%10%
2281
16th to endNight
34%36%21%26%8%
2509
December1st to 15thNight
42%38%21%18%5%
2621
16th to endNight
45%39%19%17%4
2704

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
20%18%34%20%6%
135
16th to endDay
18%23%30%15%9%2
144
February1st to 15thDay
24%14%45%14%1
135
16th to endDay
24%12%37%18%6%
208
March1st to 15thDay
17%15%37%21%8%
330
16th to endDay
18%11%37%25%5%1
352
April1st to 15thDay
15%12%28%24%16%3
330
16th to endDay
17%5%21%31%17%5%
319
May1st to 15thDay
14%11%21%26%19%6%
348
16th to endDay
17%215%21%30%11%
395
June1st to 15thDay
10%213%25%32%16%
375
16th to endDay
8%215%26%31%15%
375
July1st to 15thDay
8%110%27%30%22%
365
16th to endDay
10%18%22%38%19%
390
August1st to 15thDay
13%29%23%29%22%
358
16th to endDay
11%26%23%28%29%
396
September1st to 15thDay
17%211%14%29%25%
375
16th to endDay
26%210%23%23%13%
374
October1st to 15thDay
19%314%23%25%13%
345
16th to endDay
12%5%22%28%23%7%
336
November1st to 15thDay
21%6%21%25%20%4
325
16th to endDay
10%10%24%25%24%5%
158
December1st to 15thDay
20%7%38%22%10%
108
16th to endDay
24%15%30%21%7%
144
January1st to 15thNight
18%12%32%28%6%
780
16th to endNight
19%12%38%25%3
832
February1st to 15thNight
20%12%35%28%2
764
16th to endNight
16%13%39%26%3
683
March1st to 15thNight
17%12%34%27%6%
780
16th to endNight
18%10%31%31%8%
832
April1st to 15thNight
15%12%31%30%9%
778
16th to endNight
16%7%26%35%13%
758
May1st to 15thNight
11%5%25%38%17%1
585
16th to endNight
14%112%34%31%4
611
June1st to 15thNight
10%212%33%35%4
585
16th to endNight
8%110%36%39%3
585
July1st to 15thNight
9%17%33%41%6%
555
16th to endNight
7%6%33%43%8%
612
August1st to 15thNight
13%16%33%39%6%
575
16th to endNight
11%15%31%41%8%
774
September1st to 15thNight
13%17%32%35%8%
780
16th to endNight
21%112%30%30%3
777
October1st to 15thNight
19%317%30%23%6%
752
16th to endNight
12%7%29%26%20%3
768
November1st to 15thNight
17%6%26%31%16%2
760
16th to endNight
14%10%26%31%15%1
780
December1st to 15thNight
18%7%31%32%9%
780
16th to endNight
23%9%31%29%6%
832
Page generated at 2018-10-09 10:39:12. Version ac04

Copyright 2018 A. Danko


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