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 2017-09-21.

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
39%
15874
17%
46858
11%
15832
44%
15832
23%
31792

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
16%
900
13%
2506
5%
895
24%
895
14%
1940
January16th to endNight
21%
945
11%
2673
5%
945
25%
945
14%
2056
February1st to 15thNight
21%
701
11%
2115
4%
701
28%
701
16%
1550
February16th to endNight
23%
631
15%
1893
7%
631
30%
631
16%
1365
March1st to 15thNight
26%
720
13%
2154
9%
720
30%
720
16%
1554
March16th to endNight
30%
702
15%
2046
8%
702
37%
702
20%
1452
April1st to 15thNight
29%
539
15%
1797
8%
539
39%
539
20%
1191
April16th to endNight
35%
540
20%
1696
12%
540
44%
540
24%
1105
May1st to 15thNight
38%
540
14%
1620
9%
540
44%
540
20%
1150
May16th to endNight
52%
562
16%
1604
10%
561
56%
561
26%
1064
June1st to 15thNight
57%
540
17%
1440
11%
540
61%
540
37%
886
June16th to endNight
55%
540
17%
1440
12%
540
59%
540
33%
927
July1st to 15thNight
63%
510
16%
1360
13%
510
65%
510
36%
841
July16th to endNight
73%
564
23%
1434
17%
531
76%
531
43%
828
August1st to 15thNight
69%
539
22%
1609
20%
536
71%
536
36%
930
August16th to endNight
68%
573
21%
1910
21%
573
72%
573
33%
1075
September1st to 15thNight
61%
597
26%
1857
23%
597
65%
597
34%
1080
September16th to endNight
63%
681
27%
1881
21%
681
66%
681
35%
1143
October1st to 15thNight
53%
660
27%
1816
21%
660
58%
660
35%
1102
October16th to endNight
30%
704
18%
2277
13%
704
37%
704
21%
1476
November1st to 15thNight
38%
700
25%
2276
19%
700
49%
700
27%
1371
November16th to endNight
27%
720
17%
2340
12%
720
35%
720
17%
1637
December1st to 15thNight
21%
806
10%
2426
5%
806
27%
806
13%
1881
December16th to endNight
17%
960
10%
2688
3%
960
23%
960
11%
2188

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%5%3445%7%35%
48009
Night
14%8%36%5%34446%38%
47029
Cloud CoverDay
14%8%36%5%3445%7%35%
48018
Night
14%8%36%5%34446%38%
47034
TransparencyDay
47%6%11%20%12%1
47698
Night
46%5%11%20%14%2
46858
SeeingDay
17%6%23%25%19%8%
5889
Night
18%8%27%29%13%1
15878

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
18%15%48%6%34445%23%
1432
16th to endDay
14%16%7%10%5%3435%5%23%
1549
February1st to 15thDay
15%14%5%9%7%45%335%25%
1744
16th to endDay
14%13%6%9%5%245%47%26%
1580
March1st to 15thDay
19%13%6%7%5%2345%6%26%
1796
16th to endDay
17%11%36%5%245%5%7%29%
2187
April1st to 15thDay
18%9%25%5%2435%6%35%
2151
16th to endDay
18%7%36%42345%7%34%
2262
May1st to 15thDay
21%8%36%5%3445%7%28%
2331
16th to endDay
12%6%25%6%35%5%5%6%38%
2509
June1st to 15thDay
10%425%6%3445%8%43%
2520
16th to endDay
9%426%5%36%5%6%9%39%
2520
July1st to 15thDay
10%5%246%26%5%6%9%40%
2520
16th to endDay
7%3245%35%6%8%11%40%
2637
August1st to 15thDay
7%3246%345%5%10%44%
2338
16th to endDay
8%325%6%36%6%6%9%41%
2292
September1st to 15thDay
11%5%245%245%5%7%44%
2091
16th to endDay
11%5%245%2435%7%46%
1872
October1st to 15thDay
14%6%245%24446%43%
1812
16th to endDay
18%8%15%5%3445%6%35%
1595
November1st to 15thDay
14%7%35%323246%46%
1582
16th to endDay
18%10%47%5%25%346%31%
1620
December1st to 15thDay
19%13%5%9%6%34335%24%
1533
16th to endDay
22%14%6%8%5%35%346%19%
1536
January1st to 15thNight
19%12%5%8%6%3333427%
2506
16th to endNight
14%14%6%10%6%3434427%
2673
February1st to 15thNight
17%12%5%7%5%23335%31%
2113
16th to endNight
15%12%49%6%24345%32%
1893
March1st to 15thNight
17%10%46%5%35%445%31%
2141
16th to endNight
16%8%37%6%34447%33%
2046
April1st to 15thNight
16%6%36%435%447%37%
1797
16th to endNight
17%7%25%42335%8%39%
1696
May1st to 15thNight
19%6%36%5%2446%6%34%
1620
16th to endNight
12%435%5%35%5%6%7%40%
1602
June1st to 15thNight
8%4245%2345%6%50%
1440
16th to endNight
8%5%25%5%35%45%8%45%
1440
July1st to 15thNight
7%4244346%7%10%45%
1440
16th to endNight
5%314325%45%9%53%
1531
August1st to 15thNight
5%4144245%8%10%47%
1620
16th to endNight
7%215%43445%8%51%
1910
September1st to 15thNight
10%42343345%6%51%
1857
16th to endNight
10%424424448%50%
1881
October1st to 15thNight
12%32442335%7%49%
1816
16th to endNight
18%7%35%42335%6%40%
2277
November1st to 15thNight
12%6%33423447%46%
2276
16th to endNight
19%10%46%5%34346%33%
2340
December1st to 15thNight
20%12%6%8%5%2443426%
2426
16th to endNight
23%14%6%7%6%34345%20%
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
18%15%5%8%6%34345%23%
1432
16th to endDay
14%17%6%10%5%3345%6%23%
1549
February1st to 15thDay
15%14%5%9%7%35%435%25%
1744
16th to endDay
15%12%7%9%5%35%446%26%
1580
March1st to 15thDay
20%12%6%6%5%2435%6%25%
1806
16th to endDay
17%11%47%5%2445%7%29%
2186
April1st to 15thDay
19%9%35%42445%5%35%
2151
16th to endDay
18%7%26%5%2345%7%34%
2262
May1st to 15thDay
20%8%36%6%35%45%6%29%
2331
16th to endDay
12%6%25%5%35%5%5%7%38%
2509
June1st to 15thDay
10%425%5%3445%8%43%
2520
16th to endDay
9%426%5%36%5%6%9%39%
2520
July1st to 15thDay
10%5%245%35%5%7%9%40%
2520
16th to endDay
7%4245%36%6%8%11%41%
2637
August1st to 15thDay
7%325%5%345%5%10%44%
2338
16th to endDay
8%4245%35%6%6%9%41%
2292
September1st to 15thDay
12%5%245%245%5%6%44%
2091
16th to endDay
12%5%245%2435%7%46%
1872
October1st to 15thDay
14%7%245%34445%43%
1812
16th to endDay
18%8%15%5%2445%6%35%
1595
November1st to 15thDay
14%8%34323246%47%
1582
16th to endDay
18%10%47%5%25%346%31%
1620
December1st to 15thDay
19%13%5%10%6%34336%23%
1533
16th to endDay
22%14%6%8%5%35%346%19%
1536
January1st to 15thNight
19%12%6%9%6%3423427%
2506
16th to endNight
15%14%6%10%6%3434427%
2673
February1st to 15thNight
17%12%47%5%24345%31%
2106
16th to endNight
15%12%49%6%24345%32%
1893
March1st to 15thNight
18%10%46%5%25%445%31%
2154
16th to endNight
16%8%36%6%245%47%33%
2046
April1st to 15thNight
16%7%36%434447%37%
1797
16th to endNight
17%7%25%42335%7%39%
1696
May1st to 15thNight
20%6%36%5%3446%6%33%
1619
16th to endNight
12%435%435%5%6%7%40%
1602
June1st to 15thNight
8%425%42345%6%51%
1440
16th to endNight
8%5%25%4345%5%9%45%
1440
July1st to 15thNight
7%3244345%7%10%46%
1440
16th to endNight
5%324325%45%9%54%
1531
August1st to 15thNight
5%4144246%8%10%47%
1620
16th to endNight
7%315%434448%51%
1910
September1st to 15thNight
10%423433346%52%
1857
16th to endNight
10%424424448%50%
1881
October1st to 15thNight
13%32442345%6%49%
1816
16th to endNight
18%6%35%43235%6%39%
2277
November1st to 15thNight
13%6%24423447%46%
2276
16th to endNight
19%10%46%5%34246%33%
2340
December1st to 15thNight
20%12%6%8%5%2443426%
2426
16th to endNight
23%14%6%7%6%33345%20%
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
63%410%14%7%
1433
16th to endDay
62%413%13%6%
1549
February1st to 15thDay
61%410%14%8%
1746
16th to endDay
58%5%12%18%5%
1580
March1st to 15thDay
59%412%16%6%
1806
16th to endDay
53%6%13%20%5%1
2187
April1st to 15thDay
49%5%11%21%12%
2151
16th to endDay
48%6%11%18%9%5%
2262
May1st to 15thDay
54%7%10%18%8%
2331
16th to endDay
44%8%10%19%14%2
2513
June1st to 15thDay
38%6%11%24%17%1
2520
16th to endDay
39%8%13%19%15%2
2520
July1st to 15thDay
39%7%11%21%17%3
2371
16th to endDay
33%8%18%24%13%2
2471
August1st to 15thDay
34%7%13%24%18%1
2325
16th to endDay
36%8%12%21%16%5%
2292
September1st to 15thDay
38%6%12%21%17%4
2091
16th to endDay
36%6%8%25%20%1
1872
October1st to 15thDay
41%5%9%24%17%2
1812
16th to endDay
47%5%11%22%11%
1595
November1st to 15thDay
40%311%22%18%3
1582
16th to endDay
53%5%11%21%8%
1620
December1st to 15thDay
63%310%17%4
1533
16th to endDay
66%5%10%13%3
1536
January1st to 15thNight
60%37%16%10%
2506
16th to endNight
60%313%15%6%
2673
February1st to 15thNight
55%413%16%8%1
2115
16th to endNight
54%411%20%8%
1893
March1st to 15thNight
53%5%11%18%8%2
2154
16th to endNight
50%5%12%21%8%1
2046
April1st to 15thNight
45%5%11%20%14%1
1797
16th to endNight
43%5%10%21%13%6%
1696
May1st to 15thNight
49%6%11%21%10%1
1620
16th to endNight
39%8%12%19%15%3
1604
June1st to 15thNight
32%5%12%25%21%2
1440
16th to endNight
35%6%13%22%17%4
1440
July1st to 15thNight
31%7%13%22%20%3
1360
16th to endNight
26%6%15%29%18%4
1434
August1st to 15thNight
27%8%13%23%24%1
1609
16th to endNight
30%7%12%22%22%5%
1910
September1st to 15thNight
33%410%24%20%6%
1857
16th to endNight
33%5%8%25%24%2
1881
October1st to 15thNight
33%411%24%22%2
1816
16th to endNight
44%5%11%25%12%1
2277
November1st to 15thNight
37%48%22%21%4
2276
16th to endNight
53%211%22%9%
2340
December1st to 15thNight
61%49%15%7%
2426
16th to endNight
66%49%13%5%
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
31%14%32%15%5%1
90
16th to endDay
31%11%34%20%2
96
February1st to 15thDay
17%17%46%15%2
90
16th to endDay
19%11%35%23%9%
81
March1st to 15thDay
31%16%33%15%3
96
16th to endDay
30%7%29%19%10%1
288
April1st to 15thDay
26%9%30%21%11%2
270
16th to endDay
22%9%24%23%13%5%
270
May1st to 15thDay
25%10%26%23%10%4
288
16th to endDay
18%429%23%17%7%
409
June1st to 15thDay
13%422%33%20%6%
495
16th to endDay
13%5%29%25%18%6%
495
July1st to 15thDay
12%223%29%21%11%
475
16th to endDay
8%214%30%28%16%
497
August1st to 15thDay
9%110%25%31%21%
313
16th to endDay
10%213%23%36%14%
332
September1st to 15thDay
13%213%28%30%11%
315
16th to endDay
14%410%21%38%11%
275
October1st to 15thDay
14%5%23%28%19%7%
252
16th to endDay
26%9%35%29%
96
November1st to 15thDay
10%8%21%25%23%11%
90
16th to endDay
31%11%35%15%6%
90
December1st to 15thDay
22%15%40%17%4
90
16th to endDay
28%16%44%7%3
96
January1st to 15thNight
24%15%36%19%3
900
16th to endNight
19%15%33%27%3
945
February1st to 15thNight
23%11%35%26%3
704
16th to endNight
22%12%33%26%4
631
March1st to 15thNight
21%12%33%27%5%
720
16th to endNight
18%10%35%27%7%
702
April1st to 15thNight
18%10%38%24%8%
539
16th to endNight
22%6%31%27%10%
540
May1st to 15thNight
22%5%27%33%10%
540
16th to endNight
13%323%37%20%1
563
June1st to 15thNight
10%222%44%19%
540
16th to endNight
10%323%41%20%
540
July1st to 15thNight
8%117%44%25%2
510
16th to endNight
6%13%38%36%4
564
August1st to 15thNight
6%13%42%30%6%
539
16th to endNight
8%13%32%37%6%
573
September1st to 15thNight
13%317%35%25%4
597
16th to endNight
11%414%33%32%3
681
October1st to 15thNight
14%6%21%35%18%3
660
16th to endNight
23%10%32%23%9%
704
November1st to 15thNight
17%7%32%29%10%1
700
16th to endNight
23%14%29%23%9%
720
December1st to 15thNight
27%12%30%22%5%
806
16th to endNight
30%12%32%20%4
960
Page generated at 2017-09-22 07:35:30. Version ac04

Copyright 2017 A. Danko


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