Burnsville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Burnsville clear sky chart from 2005-11-06 to 2024-03-23.

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%
25115
15%
80791
8%
25018
41%
25018
21%
54800

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 10thNight
25%
942
10%
4398
5%
926
33%
926
11%
3310
January11th to 20thNight
24%
948
9%
4331
5%
930
29%
930
9%
3270
January21st to endNight
21%
1032
8%
4477
3%
1023
27%
1023
9%
3378
February1st to 10thNight
24%
950
15%
2470
4%
950
30%
950
22%
1786
February11th to 20thNight
24%
929
16%
2403
5%
924
32%
924
24%
1669
February21st to endNight
27%
724
16%
1980
5%
724
36%
724
22%
1388
March1st to 10thNight
28%
632
15%
2152
9%
632
36%
632
19%
1446
March11th to 20thNight
29%
570
18%
2090
10%
570
41%
570
19%
1354
March21st to endNight
31%
600
15%
2180
12%
600
39%
600
16%
1500
April1st to 10thNight
28%
540
15%
1800
9%
540
38%
540
20%
1198
April11th to 20thNight
29%
533
17%
1767
13%
533
39%
533
17%
1231
April21st to endNight
31%
540
17%
1620
9%
540
41%
540
20%
1130
May1st to 10thNight
31%
540
14%
1530
8%
540
37%
540
24%
1048
May11th to 20thNight
38%
531
18%
1417
9%
531
44%
531
29%
940
May21st to endNight
42%
583
14%
1552
5%
582
47%
582
26%
1045
June1st to 10thNight
48%
540
16%
1440
6%
540
53%
540
37%
882
June11th to 20thNight
44%
540
14%
1440
5%
540
48%
540
32%
924
June21st to endNight
57%
540
17%
1440
9%
540
60%
540
42%
849
July1st to 10thNight
64%
525
17%
1400
8%
525
66%
525
49%
770
July11th to 20thNight
57%
522
21%
1392
9%
522
61%
522
44%
809
July21st to endNight
63%
591
22%
1521
13%
558
66%
558
50%
826
August1st to 10thNight
63%
537
21%
1601
17%
534
66%
534
35%
942
August11th to 20thNight
60%
534
23%
1600
20%
534
66%
534
37%
927
August21st to endNight
53%
594
23%
1894
20%
594
61%
594
36%
1050
September1st to 10thNight
54%
540
23%
1800
22%
540
61%
540
34%
990
September11th to 20thNight
45%
540
26%
1824
19%
540
57%
540
34%
997
September21st to endNight
37%
607
21%
2047
13%
607
48%
607
29%
1196
October1st to 10thNight
38%
720
22%
2160
14%
720
45%
720
30%
1314
October11th to 20thNight
28%
720
20%
2160
8%
720
38%
720
24%
1426
October21st to endNight
30%
792
18%
2392
9%
792
38%
792
19%
1632
November1st to 10thNight
28%
843
20%
2509
9%
843
38%
843
24%
1631
November11th to 20thNight
25%
950
15%
2660
6%
950
32%
950
18%
1953
November21st to endNight
24%
950
16%
2660
6%
950
32%
950
21%
1864
December1st to 10thNight
25%
950
10%
2660
3%
950
31%
950
17%
1954
December11th to 20thNight
19%
949
11%
3212
3%
948
27%
948
12%
2388
December21st to endNight
18%
1037
7%
4812
3%
1026
26%
1026
7%
3783

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%9%47%6%35%5%5%7%36%
78674
Night
12%9%47%6%35%45%6%38%
81272
TransparencyDay
46%7%14%22%10%1
78377
Night
46%6%13%22%11%1
81089
SeeingDay
16%12%32%26%12%3
15038
Night
15%10%34%30%10%1
25148

By Month

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 10thDay
12%15%7%16%8%4434422%
2527
11th to 20thDay
6%12%6%11%10%5%8%8%7%6%20%
2566
21st to endDay
9%19%8%11%7%35%446%24%
3135
February1st to 10thDay
9%11%6%8%8%5%6%6%6%6%31%
1710
11th to 20thDay
9%9%6%8%7%35%5%5%6%35%
1664
21st to endDay
13%10%5%9%6%45%5%6%6%32%
1473
March1st to 10thDay
13%12%6%8%6%3445%6%32%
2045
11th to 20thDay
14%10%46%5%36%45%7%36%
2090
21st to endDay
21%10%47%6%3445%6%30%
2219
April1st to 10thDay
17%10%46%5%3445%7%34%
2160
11th to 20thDay
20%11%46%5%34445%32%
2139
21st to endDay
21%11%45%6%35%45%6%30%
2340
May1st to 10thDay
17%8%36%6%45%5%5%8%33%
2430
11th to 20thDay
17%7%35%5%3445%8%39%
2479
21st to endDay
14%7%35%6%36%5%5%8%37%
2725
June1st to 10thDay
12%5%24435%5%6%9%45%
2520
11th to 20thDay
13%6%26%6%35%5%5%10%39%
2520
21st to endDay
10%425%5%47%7%8%8%40%
2520
July1st to 10thDay
7%4245%35%5%8%11%47%
2520
11th to 20thDay
8%4244345%6%9%51%
2520
21st to endDay
5%4245%36%6%7%9%48%
2705
August1st to 10thDay
9%5%25%6%46%7%7%9%40%
2328
11th to 20thDay
13%5%25%4345%6%8%44%
2301
21st to endDay
9%425%5%2445%8%52%
2462
September1st to 10thDay
12%5%25%5%45%45%6%46%
2160
11th to 20thDay
13%5%244245%5%7%48%
2134
21st to endDay
15%7%25%5%335%5%7%42%
1895
October1st to 10thDay
17%7%35%5%3345%6%43%
1800
11th to 20thDay
15%9%35%6%345%5%6%40%
1800
21st to endDay
18%11%46%5%2435%6%36%
1962
November1st to 10thDay
11%10%5%7%6%35%45%6%38%
1564
11th to 20thDay
11%13%7%10%7%35%45%6%30%
1520
21st to endDay
14%9%37%7%3345%7%36%
1520
December1st to 10thDay
12%11%5%10%9%5%7%5%5%5%27%
1520
11th to 20thDay
11%12%7%10%7%35%5%5%6%29%
1918
21st to endDay
22%13%7%16%7%3433418%
2783
January1st to 10thNight
10%14%8%14%8%34445%27%
4428
11th to 20thNight
7%11%6%11%10%5%8%9%7%5%22%
4402
21st to endNight
11%20%8%10%6%3443427%
4532
February1st to 10thNight
7%11%5%10%7%5%5%45%6%35%
2470
11th to 20thNight
7%8%5%8%6%46%5%47%40%
2403
21st to endNight
12%8%48%6%45%45%5%38%
1980
March1st to 10thNight
12%9%47%6%35%45%7%38%
2152
11th to 20thNight
13%9%46%6%45%447%38%
2090
21st to endNight
19%10%46%5%25%45%6%34%
2180
April1st to 10thNight
16%11%36%4345%5%6%38%
1800
11th to 20thNight
22%8%46%435%45%6%33%
1767
21st to endNight
19%9%26%5%4445%7%35%
1620
May1st to 10thNight
18%7%35%5%2446%7%38%
1530
11th to 20thNight
15%5%26%4345%5%6%45%
1416
21st to endNight
13%5%45%6%45%45%8%41%
1551
June1st to 10thNight
10%5%25%5%245%6%9%48%
1440
11th to 20thNight
9%5%25%6%45%6%6%7%46%
1440
21st to endNight
7%225%5%345%5%10%53%
1440
July1st to 10thNight
43133245%6%10%57%
1440
11th to 20thNight
5%225%435%46%9%55%
1440
21st to endNight
5%314335%45%8%60%
1611
August1st to 10thNight
6%3246%347%6%8%50%
1611
11th to 20thNight
11%5%2432445%8%53%
1600
21st to endNight
7%425%5%3445%6%56%
1894
September1st to 10thNight
10%3245%235%5%8%53%
1800
11th to 20thNight
11%5%2343435%8%53%
1824
21st to endNight
14%5%25%423445%51%
2047
October1st to 10thNight
15%6%36%323346%48%
2160
11th to 20thNight
15%9%35%5%3445%6%41%
2160
21st to endNight
18%10%36%424346%38%
2392
November1st to 10thNight
13%8%46%5%35%45%6%43%
2509
11th to 20thNight
12%10%5%10%7%35%445%34%
2660
21st to endNight
14%9%47%7%35%346%38%
2660
December1st to 10thNight
10%10%5%10%9%45%45%6%31%
2660
11th to 20thNight
11%13%5%10%9%46%45%6%28%
3279
21st to endNight
23%13%6%10%7%44445%21%
4884

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 10thDay
65%6%11%15%3
2528
11th to 20thDay
62%6%10%16%5%
2566
21st to endDay
62%6%14%14%4
3135
February1st to 10thDay
52%7%15%18%8%1
1710
11th to 20thDay
50%5%13%24%8%1
1673
21st to endDay
51%7%13%18%11%
1473
March1st to 10thDay
52%6%14%20%7%1
2045
11th to 20thDay
48%6%14%23%8%1
2090
21st to endDay
55%7%10%21%6%1
2219
April1st to 10thDay
49%6%13%21%10%1
2160
11th to 20thDay
54%5%11%18%11%2
2139
21st to endDay
54%7%12%19%8%1
2340
May1st to 10thDay
49%7%13%21%9%2
2430
11th to 20thDay
44%7%14%23%11%1
2483
21st to endDay
45%8%11%22%12%1
2725
June1st to 10thDay
33%8%15%29%13%1
2520
11th to 20thDay
41%8%13%23%14%1
2520
21st to endDay
36%10%18%25%10%2
2520
July1st to 10thDay
29%9%18%30%13%1
2451
11th to 20thDay
28%8%15%27%18%3
2445
21st to endDay
28%9%18%27%15%2
2555
August1st to 10thDay
37%9%15%27%9%3
2314
11th to 20thDay
36%9%15%30%11%1
2301
21st to endDay
29%6%16%30%18%1
2462
September1st to 10thDay
37%7%13%29%14%
2160
11th to 20thDay
35%7%18%32%9%1
2134
21st to endDay
41%6%13%31%9%1
1895
October1st to 10thDay
42%6%12%28%12%1
1800
11th to 20thDay
43%6%13%25%12%1
1800
21st to endDay
50%5%14%22%10%1
1962
November1st to 10thDay
45%6%14%18%13%3
1564
11th to 20thDay
55%6%13%17%9%1
1520
21st to endDay
47%7%18%22%7%1
1520
December1st to 10thDay
58%7%16%13%6%
1520
11th to 20thDay
56%7%17%15%5%
1915
21st to endDay
69%6%10%11%4
2783
January1st to 10thNight
60%5%12%17%5%
4428
11th to 20thNight
60%6%13%15%5%
4402
21st to endNight
62%49%19%6%1
4532
February1st to 10thNight
51%413%21%10%1
2470
11th to 20thNight
45%6%14%25%9%1
2404
21st to endNight
48%5%12%22%12%1
1980
March1st to 10thNight
46%7%15%22%10%
2152
11th to 20thNight
47%412%23%13%1
2090
21st to endNight
50%6%11%22%9%1
2180
April1st to 10thNight
47%5%11%23%14%1
1800
11th to 20thNight
51%5%9%18%14%2
1767
21st to endNight
47%7%10%20%14%2
1620
May1st to 10thNight
44%7%14%19%14%2
1530
11th to 20thNight
39%7%15%22%15%3
1417
21st to endNight
41%7%12%20%17%2
1552
June1st to 10thNight
30%8%15%28%18%2
1440
11th to 20thNight
35%8%14%22%18%3
1440
21st to endNight
25%8%17%31%16%3
1440
July1st to 10thNight
21%7%17%34%20%2
1400
11th to 20thNight
24%7%15%32%18%4
1392
21st to endNight
21%5%18%33%17%5%
1521
August1st to 10thNight
29%8%14%29%15%4
1601
11th to 20thNight
30%6%17%28%18%2
1600
21st to endNight
28%7%14%29%19%4
1894
September1st to 10thNight
29%6%13%33%18%1
1800
11th to 20thNight
30%6%16%31%17%1
1824
21st to endNight
36%5%13%30%16%1
2047
October1st to 10thNight
37%5%11%30%15%2
2160
11th to 20thNight
42%6%14%22%14%2
2160
21st to endNight
48%5%13%21%12%1
2392
November1st to 10thNight
41%7%14%23%14%2
2509
11th to 20thNight
53%6%12%18%11%1
2660
21st to endNight
48%5%16%22%7%1
2660
December1st to 10thNight
53%7%15%19%6%
2660
11th to 20thNight
56%7%14%17%5%1
3281
21st to endNight
65%6%11%14%4
4884

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 10thDay
11%12%36%27%11%2
270
11th to 20thDay
14%15%41%25%4
270
21st to endDay
17%11%38%23%10%2
297
February1st to 10thDay
14%17%43%21%41
270
11th to 20thDay
14%18%39%23%5%1
270
21st to endDay
17%15%40%26%2
225
March1st to 10thDay
18%15%40%20%6%
270
11th to 20thDay
18%14%37%24%7%1
270
21st to endDay
25%20%24%22%8%2
289
April1st to 10thDay
23%15%36%20%5%1
420
11th to 20thDay
28%14%25%22%10%1
417
21st to endDay
26%14%30%20%8%2
600
May1st to 10thDay
19%16%33%23%8%1
603
11th to 20thDay
20%14%29%21%13%3
625
21st to endDay
16%11%27%30%13%3
679
June1st to 10thDay
9%9%27%34%18%3
630
11th to 20thDay
13%7%39%28%10%2
630
21st to endDay
10%11%31%27%17%3
630
July1st to 10thDay
8%5%24%32%23%8%
621
11th to 20thDay
10%7%28%30%20%5%
618
21st to endDay
6%5%28%37%19%5%
684
August1st to 10thDay
10%5%24%35%21%5%
626
11th to 20thDay
14%423%31%22%6%
615
21st to endDay
10%7%27%35%16%5%
581
September1st to 10thDay
16%10%28%28%14%4
450
11th to 20thDay
13%8%29%30%17%3
424
21st to endDay
19%14%33%20%10%4
270
October1st to 10thDay
19%13%27%26%12%4
270
11th to 20thDay
16%23%34%22%5%1
270
21st to endDay
26%16%37%13%7%1
297
November1st to 10thDay
18%18%38%17%9%1
270
11th to 20thDay
16%21%43%17%3
270
21st to endDay
22%14%43%16%4
270
December1st to 10thDay
15%13%39%27%6%1
270
11th to 20thDay
18%18%34%24%5%
270
21st to endDay
27%15%37%16%4
297
January1st to 10thNight
12%12%40%29%7%1
950
11th to 20thNight
16%13%37%28%5%1
950
21st to endNight
18%11%38%28%5%1
1045
February1st to 10thNight
12%12%40%29%6%1
950
11th to 20thNight
12%12%43%26%6%1
929
21st to endNight
16%13%35%28%7%1
724
March1st to 10thNight
15%10%40%27%8%1
632
11th to 20thNight
17%11%38%28%6%
570
21st to endNight
22%13%29%25%11%2
600
April1st to 10thNight
19%13%36%26%5%
540
11th to 20thNight
27%11%29%27%6%
533
21st to endNight
21%11%33%25%9%1
540
May1st to 10thNight
19%10%34%30%6%1
540
11th to 20thNight
17%9%33%30%11%1
531
21st to endNight
15%9%27%34%14%1
584
June1st to 10thNight
11%5%31%41%12%
540
11th to 20thNight
10%5%36%41%8%
540
21st to endNight
8%326%47%16%1
540
July1st to 10thNight
5%324%39%27%1
525
11th to 20thNight
5%5%29%44%16%2
522
21st to endNight
6%325%49%17%2
591
August1st to 10thNight
6%321%47%22%1
537
11th to 20thNight
12%222%38%23%3
534
21st to endNight
7%429%35%23%2
594
September1st to 10thNight
10%6%25%38%18%3
540
11th to 20thNight
11%7%34%30%15%3
540
21st to endNight
14%11%34%28%13%
607
October1st to 10thNight
18%10%29%28%14%1
720
11th to 20thNight
20%11%37%25%7%1
720
21st to endNight
24%11%29%28%7%
792
November1st to 10thNight
18%13%36%26%7%
843
11th to 20thNight
17%14%37%25%6%
950
21st to endNight
17%15%37%23%7%
950
December1st to 10thNight
15%11%38%28%7%
950
11th to 20thNight
19%11%39%25%6%1
950
21st to endNight
25%13%33%25%4
1045
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