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 2017-04-07.

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
25%
14280
11%
45434
7%
14249
31%
14249
12%
34286

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%
720
6%
2506
3%
716
14%
716
5%
2101
January16th to endNight
15%
768
8%
2688
4%
768
21%
768
7%
2144
February1st to 15thNight
14%
704
7%
2276
3%
701
20%
701
6%
1938
February16th to endNight
18%
631
10%
1893
6%
631
24%
631
9%
1516
March1st to 15thNight
20%
720
12%
2160
7%
720
26%
720
10%
1672
March16th to endNight
20%
768
17%
2001
6%
768
29%
768
14%
1499
April1st to 15thNight
19%
686
14%
1716
5%
686
24%
686
14%
1348
April16th to endNight
26%
569
14%
1559
4%
569
33%
569
15%
1122
May1st to 15thNight
27%
404
17%
1394
10%
404
38%
404
15%
936
May16th to endNight
31%
342
12%
1369
9%
342
40%
342
14%
909
June1st to 15thNight
26%
330
9%
1320
7%
330
35%
330
10%
951
June16th to endNight
39%
330
8%
1320
10%
330
44%
330
16%
855
July1st to 15thNight
47%
310
11%
1240
16%
310
51%
310
18%
779
July16th to endNight
45%
348
11%
1306
13%
326
52%
326
18%
817
August1st to 15thNight
51%
363
14%
1344
14%
361
55%
361
18%
878
August16th to endNight
49%
698
17%
1748
9%
698
52%
698
29%
1172
September1st to 15thNight
45%
660
14%
1655
7%
660
47%
660
26%
1153
September16th to endNight
42%
657
20%
1815
14%
657
46%
657
27%
1190
October1st to 15thNight
29%
660
15%
1919
10%
660
35%
660
15%
1418
October16th to endNight
21%
704
8%
2260
4%
704
27%
704
10%
1793
November1st to 15thNight
22%
700
14%
2277
11%
700
28%
700
12%
1704
November16th to endNight
18%
720
11%
2460
7%
720
23%
720
8%
1916
December1st to 15thNight
10%
720
4%
2520
2%
720
14%
720
4%
2143
December16th to endNight
11%
768
5%
2688
2%
768
14%
768
4%
2332

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
17%9%36%5%345%5%7%31%
45814
Night
18%11%47%5%34445%29%
45604
Cloud CoverDay
17%9%36%5%3445%6%31%
45824
Night
19%11%47%5%34445%29%
45609
TransparencyDay
53%7%10%17%9%
45502
Night
57%6%10%16%8%
45434
SeeingDay
22%21%24%19%9%3
5014
Night
22%24%22%21%8%
14281

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%14%7%10%7%36%5%45%16%
1432
16th to endDay
12%15%5%9%7%45%5%5%7%21%
1536
February1st to 15thDay
12%12%6%12%10%5%5%5%4419%
1585
16th to endDay
14%14%6%9%7%345%46%23%
1580
March1st to 15thDay
17%13%5%7%7%35%44425%
1790
16th to endDay
18%9%47%5%23335%35%
2220
April1st to 15thDay
21%9%46%434336%32%
2048
16th to endDay
19%8%25%5%24346%37%
2070
May1st to 15thDay
19%6%26%5%34447%34%
2237
16th to endDay
17%6%245%35%5%48%35%
2394
June1st to 15thDay
25%6%244345%5%9%27%
2310
16th to endDay
16%5%25%5%35%6%6%8%32%
2310
July1st to 15thDay
10%6%25%6%35%6%6%8%37%
2310
16th to endDay
11%5%25%5%35%6%7%10%34%
2458
August1st to 15thDay
13%5%26%7%35%5%6%8%35%
2263
16th to endDay
10%435%5%345%49%43%
2102
September1st to 15thDay
17%6%25%423346%43%
1975
16th to endDay
12%5%25%4235%47%46%
1815
October1st to 15thDay
21%8%36%5%24445%31%
1711
16th to endDay
23%12%37%5%34445%24%
1612
November1st to 15thDay
17%11%36%5%35%45%6%30%
1581
16th to endDay
19%11%48%425%6%4427%
1499
December1st to 15thDay
21%17%5%8%6%24445%17%
1440
16th to endDay
25%17%7%8%445%43414%
1536
January1st to 15thNight
18%16%7%12%6%35%435%16%
2506
16th to endNight
12%15%6%10%7%45%45%5%23%
2688
February1st to 15thNight
13%14%8%15%9%4443417%
2275
16th to endNight
15%15%6%9%6%25%435%24%
1893
March1st to 15thNight
19%14%6%6%5%2333329%
2147
16th to endNight
18%11%46%5%2333434%
2001
April1st to 15thNight
22%11%5%6%6%23345%28%
1716
16th to endNight
21%9%3443334437%
1559
May1st to 15thNight
19%7%35%434348%35%
1394
16th to endNight
18%6%25%4345%5%7%36%
1367
June1st to 15thNight
25%8%25%424447%29%
1320
16th to endNight
17%435%6%2445%8%37%
1320
July1st to 15thNight
12%326%4346%7%8%38%
1320
16th to endNight
13%3145%35%5%7%9%39%
1402
August1st to 15thNight
11%5%25%5%35%5%5%8%40%
1354
16th to endNight
12%5%2442345%8%45%
1748
September1st to 15thNight
17%425%5%2345%6%43%
1655
16th to endNight
17%5%25%324345%45%
1815
October1st to 15thNight
23%9%35%5%33336%33%
1919
16th to endNight
30%10%36%5%2443425%
2260
November1st to 15thNight
20%11%46%5%2345%6%29%
2277
16th to endNight
20%12%5%9%5%34345%25%
2460
December1st to 15thNight
22%17%6%9%7%25%33415%
2520
16th to endNight
21%20%6%9%6%3433315%
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
16%15%6%11%7%36%5%5%5%16%
1432
16th to endDay
12%14%5%10%6%35%5%5%6%22%
1536
February1st to 15thDay
12%13%6%11%9%5%7%5%3419%
1585
16th to endDay
14%14%6%9%8%35%445%24%
1580
March1st to 15thDay
17%13%5%8%6%45%44424%
1800
16th to endDay
17%11%47%423345%34%
2220
April1st to 15thDay
21%10%46%423345%33%
2048
16th to endDay
19%9%35%423436%37%
2070
May1st to 15thDay
21%5%36%5%35%347%34%
2237
16th to endDay
17%6%245%35%5%5%8%35%
2394
June1st to 15thDay
26%5%25%5%245%6%8%27%
2310
16th to endDay
17%5%25%435%5%7%8%32%
2310
July1st to 15thDay
12%5%25%5%36%6%6%9%37%
2310
16th to endDay
13%425%6%36%5%7%10%34%
2458
August1st to 15thDay
13%6%26%6%35%5%5%9%35%
2263
16th to endDay
11%4245%345%5%9%42%
2102
September1st to 15thDay
19%5%25%423346%42%
1975
16th to endDay
13%5%2442345%7%45%
1815
October1st to 15thDay
21%8%46%6%3435%5%30%
1711
16th to endDay
24%13%35%6%335%3425%
1612
November1st to 15thDay
17%11%46%5%3445%5%29%
1581
16th to endDay
18%11%5%9%434445%27%
1499
December1st to 15thDay
21%18%5%7%7%345%3418%
1440
16th to endDay
25%17%7%8%5%3434414%
1536
January1st to 15thNight
17%16%6%11%6%45%44416%
2506
16th to endNight
12%15%6%10%7%45%45%422%
2688
February1st to 15thNight
13%14%8%15%9%4433417%
2268
16th to endNight
15%15%6%9%7%35%44424%
1893
March1st to 15thNight
20%13%6%7%5%3324328%
2160
16th to endNight
18%12%5%6%5%2333434%
2000
April1st to 15thNight
23%12%5%6%5%2334427%
1716
16th to endNight
21%8%45%423335%37%
1559
May1st to 15thNight
20%7%25%424348%35%
1394
16th to endNight
19%6%25%5%24448%36%
1367
June1st to 15thNight
26%7%25%5%2445%6%29%
1320
16th to endNight
17%5%25%4345%5%8%37%
1320
July1st to 15thNight
12%435%5%36%47%9%37%
1320
16th to endNight
13%4245%35%5%6%9%39%
1402
August1st to 15thNight
12%5%245%35%5%6%8%38%
1354
16th to endNight
13%5%145%2435%9%43%
1748
September1st to 15thNight
17%5%25%424337%42%
1655
16th to endNight
16%6%13423446%45%
1815
October1st to 15thNight
22%9%36%423335%33%
1919
16th to endNight
29%11%36%5%3344424%
2260
November1st to 15thNight
22%11%46%5%23445%28%
2277
16th to endNight
19%13%5%9%5%3334425%
2460
December1st to 15thNight
22%18%6%9%7%3433315%
2520
16th to endNight
22%20%6%9%7%3443315%
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%6%7%10%3
1433
16th to endDay
61%8%13%10%5%
1536
February1st to 15thDay
68%7%6%13%3
1588
16th to endDay
64%7%9%10%8%
1580
March1st to 15thDay
62%6%11%12%5%1
1800
16th to endDay
55%49%15%12%2
2220
April1st to 15thDay
55%6%7%18%10%1
2048
16th to endDay
49%5%8%19%13%3
2070
May1st to 15thDay
50%6%8%18%14%1
2237
16th to endDay
47%9%10%18%11%1
2398
June1st to 15thDay
55%9%10%16%8%
2310
16th to endDay
47%9%12%19%10%
2310
July1st to 15thDay
41%9%13%25%10%
2161
16th to endDay
44%10%13%22%7%
2291
August1st to 15thDay
46%11%13%21%7%
2249
16th to endDay
38%9%14%24%12%
2102
September1st to 15thDay
43%7%9%27%12%
1975
16th to endDay
38%8%12%26%13%
1815
October1st to 15thDay
55%6%10%17%8%
1711
16th to endDay
62%7%11%13%5%
1612
November1st to 15thDay
56%7%11%15%7%1
1581
16th to endDay
60%7%11%12%7%
1499
December1st to 15thDay
68%7%10%10%2
1440
16th to endDay
75%5%7%5%5%
1536
January1st to 15thNight
71%6%10%8%3
2506
16th to endNight
64%7%9%12%6%
2688
February1st to 15thNight
72%5%6%10%4
2276
16th to endNight
63%6%8%12%8%
1893
March1st to 15thNight
60%5%9%17%6%1
2160
16th to endNight
54%48%16%12%3
2001
April1st to 15thNight
59%5%7%15%11%
1716
16th to endNight
51%48%16%16%2
1559
May1st to 15thNight
48%5%8%17%17%2
1394
16th to endNight
46%8%11%19%11%1
1369
June1st to 15thNight
55%7%10%17%8%
1320
16th to endNight
44%7%12%24%9%1
1320
July1st to 15thNight
39%10%14%24%10%
1240
16th to endNight
40%9%15%22%11%1
1306
August1st to 15thNight
40%10%15%23%9%
1344
16th to endNight
36%9%13%26%13%
1748
September1st to 15thNight
42%6%11%28%9%
1655
16th to endNight
39%6%11%29%12%1
1815
October1st to 15thNight
54%5%9%20%9%
1919
16th to endNight
64%5%10%13%5%
2260
November1st to 15thNight
57%5%11%14%8%2
2277
16th to endNight
62%5%10%14%41
2460
December1st to 15thNight
74%5%9%9%1
2520
16th to endNight
75%6%7%7%2
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
16%30%26%21%5%
60
16th to endDay
32%21%28%14%3
64
February1st to 15thDay
24%33%26%12%2
120
16th to endDay
22%29%29%13%3
239
March1st to 15thDay
28%25%21%20%3
270
16th to endDay
24%27%22%14%6%3
288
April1st to 15thDay
30%25%19%17%6%1
235
16th to endDay
21%31%19%14%10%3
210
May1st to 15thDay
25%21%24%18%7%2
228
16th to endDay
16%22%30%19%8%2
267
June1st to 15thDay
30%21%22%17%7%
255
16th to endDay
15%18%33%22%8%1
255
July1st to 15thDay
12%18%22%26%15%4
245
16th to endDay
12%17%28%28%11%1
270
August1st to 15thDay
19%13%24%20%16%5%
253
16th to endDay
14%10%18%27%17%10%
268
September1st to 15thDay
16%14%20%22%17%8%
255
16th to endDay
15%14%24%19%15%10%
254
October1st to 15thDay
24%18%26%13%15%2
255
16th to endDay
35%20%21%17%5%
245
November1st to 15thDay
24%21%26%17%9%
235
16th to endDay
25%31%21%10%10%1
119
December1st to 15thDay
26%28%25%15%5%
60
16th to endDay
39%23%31%6%
64
January1st to 15thNight
20%32%27%15%3
720
16th to endNight
20%31%24%19%3
768
February1st to 15thNight
20%27%29%19%3
704
16th to endNight
22%29%24%19%4
631
March1st to 15thNight
27%28%20%21%2
720
16th to endNight
23%29%21%17%6%1
768
April1st to 15thNight
25%28%22%20%3
686
16th to endNight
20%31%18%19%8%
569
May1st to 15thNight
21%23%23%20%10%
404
16th to endNight
16%23%24%24%9%1
343
June1st to 15thNight
23%22%21%24%8%
330
16th to endNight
17%19%18%32%10%
330
July1st to 15thNight
10%15%19%31%20%1
310
16th to endNight
11%19%18%36%13%
348
August1st to 15thNight
14%13%14%36%18%2
363
16th to endNight
16%12%15%28%24%2
698
September1st to 15thNight
18%12%18%32%16%1
660
16th to endNight
18%14%21%23%19%2
657
October1st to 15thNight
27%18%20%20%11%
660
16th to endNight
31%19%23%18%6%
704
November1st to 15thNight
23%25%24%17%7%1
700
16th to endNight
24%32%20%14%8%1
720
December1st to 15thNight
30%31%22%11%3
720
16th to endNight
28%29%25%13%3
768
Page generated at 2017-04-08 05:35:17. Version ac04

Copyright 2017 A. Danko


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