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 2017-08-12.

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%
14573
11%
46473
7%
14542
31%
14542
12%
34990

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
20%
718
13%
1796
5%
718
25%
718
14%
1409
April16th to endNight
25%
621
15%
1701
4%
621
33%
621
15%
1227
May1st to 15thNight
27%
441
16%
1521
9%
441
37%
441
14%
1048
May16th to endNight
32%
374
12%
1497
10%
374
41%
374
14%
993
June1st to 15thNight
26%
360
9%
1440
7%
360
35%
360
11%
1023
June16th to endNight
38%
360
9%
1440
10%
360
44%
360
16%
939
July1st to 15thNight
47%
340
10%
1360
16%
340
51%
340
18%
854
July16th to endNight
47%
376
13%
1418
16%
354
54%
354
19%
880
August1st to 15thNight
52%
385
14%
1434
13%
383
56%
383
19%
926
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%35%45%7%31%
47514
Night
18%11%47%5%34445%29%
46643
Cloud CoverDay
17%9%36%5%3445%6%31%
47524
Night
19%11%47%5%34445%29%
46648
TransparencyDay
53%7%10%17%9%
47202
Night
57%6%10%16%8%
46473
SeeingDay
22%20%25%18%9%2
5513
Night
22%24%22%21%8%
14574

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%36%434336%32%
2152
16th to endDay
19%8%25%5%24346%37%
2258
May1st to 15thDay
20%6%36%5%34347%33%
2441
16th to endDay
17%6%245%35%5%5%8%34%
2618
June1st to 15thDay
24%5%25%4345%5%9%28%
2520
16th to endDay
16%5%25%5%35%6%6%8%32%
2520
July1st to 15thDay
11%6%25%5%35%6%6%8%37%
2520
16th to endDay
12%425%5%35%6%7%10%34%
2654
August1st to 15thDay
12%5%26%7%35%5%6%8%36%
2417
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%10%5%6%6%23345%29%
1796
16th to endNight
21%8%3443334437%
1701
May1st to 15thNight
20%8%36%434348%32%
1521
16th to endNight
18%5%25%4345%6%7%35%
1495
June1st to 15thNight
25%7%25%424447%29%
1440
16th to endNight
17%435%6%2445%8%37%
1440
July1st to 15thNight
11%426%5%346%7%8%39%
1440
16th to endNight
13%3145%35%5%6%9%39%
1514
August1st to 15thNight
11%5%25%5%35%5%5%8%41%
1444
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%11%36%423345%33%
2152
16th to endDay
19%10%35%423436%36%
2258
May1st to 15thDay
21%6%36%6%34347%32%
2441
16th to endDay
18%6%245%35%5%5%8%34%
2618
June1st to 15thDay
25%5%25%42446%8%28%
2520
16th to endDay
18%5%25%435%5%7%8%32%
2520
July1st to 15thDay
12%5%25%5%36%6%6%9%37%
2520
16th to endDay
13%425%5%36%5%7%9%35%
2654
August1st to 15thDay
12%6%26%6%35%5%5%9%35%
2417
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%11%5%6%5%2334428%
1796
16th to endNight
21%8%45%424335%37%
1701
May1st to 15thNight
21%8%35%5%24347%33%
1521
16th to endNight
18%6%245%3445%8%35%
1495
June1st to 15thNight
25%7%25%5%24447%29%
1440
16th to endNight
17%5%25%4345%5%8%37%
1440
July1st to 15thNight
12%425%5%36%47%9%38%
1440
16th to endNight
13%4245%35%5%7%8%40%
1514
August1st to 15thNight
12%5%245%35%5%6%8%40%
1444
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%11%1
2152
16th to endDay
50%5%8%19%12%3
2258
May1st to 15thDay
53%5%8%17%13%1
2441
16th to endDay
48%9%11%17%11%1
2622
June1st to 15thDay
54%8%9%17%8%
2520
16th to endDay
48%9%12%19%9%
2520
July1st to 15thDay
41%9%12%24%10%
2371
16th to endDay
44%10%13%22%8%
2487
August1st to 15thDay
45%11%14%21%7%
2403
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%
1796
16th to endNight
51%48%18%15%2
1701
May1st to 15thNight
50%5%7%17%16%2
1521
16th to endNight
46%8%12%20%10%1
1497
June1st to 15thNight
54%7%10%17%8%
1440
16th to endNight
44%8%13%23%9%
1440
July1st to 15thNight
38%10%15%23%11%
1360
16th to endNight
39%9%15%22%12%
1418
August1st to 15thNight
40%10%16%23%9%
1434
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%23%21%16%6%1
270
16th to endDay
23%31%19%14%8%2
270
May1st to 15thDay
29%20%23%15%7%2
288
16th to endDay
18%22%31%17%8%2
331
June1st to 15thDay
31%18%25%16%7%
315
16th to endDay
17%20%33%20%6%
315
July1st to 15thDay
14%16%26%25%14%3
305
16th to endDay
12%15%28%28%13%
326
August1st to 15thDay
17%13%23%22%17%4
297
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%27%22%21%3
718
16th to endNight
22%30%20%18%8%
621
May1st to 15thNight
23%23%22%20%9%
441
16th to endNight
16%22%25%24%9%1
375
June1st to 15thNight
22%21%23%24%8%
360
16th to endNight
18%18%20%32%9%
360
July1st to 15thNight
10%14%21%33%19%1
340
16th to endNight
11%18%17%35%15%
376
August1st to 15thNight
14%12%14%35%19%2
385
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 2017-08-13 14:16:42. Version ac04

Copyright 2017 A. Danko


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