Bismarck
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bismarck clear sky chart from 2005-11-06 to 2024-03-28.

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
41%
25258
17%
80917
11%
25169
48%
25169
25%
51762

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
32%
936
13%
4376
7%
926
40%
926
12%
2994
January11th to 20thNight
31%
947
13%
4361
7%
930
35%
930
12%
2945
January21st to endNight
30%
1036
10%
4705
6%
1023
35%
1023
11%
3262
February1st to 10thNight
35%
950
12%
2636
6%
950
40%
950
19%
1933
February11th to 20thNight
35%
789
17%
2267
9%
789
40%
789
23%
1540
February21st to endNight
42%
628
18%
1884
10%
628
48%
628
26%
1235
March1st to 10thNight
34%
760
13%
2280
8%
760
38%
760
20%
1609
March11th to 20thNight
39%
647
20%
2167
14%
647
47%
647
24%
1350
March21st to endNight
38%
615
13%
2159
9%
615
45%
615
19%
1481
April1st to 10thNight
36%
540
19%
1800
13%
540
47%
540
25%
1124
April11th to 20thNight
36%
533
18%
1671
14%
533
45%
533
24%
1133
April21st to endNight
39%
540
18%
1620
13%
540
46%
540
26%
1056
May1st to 10thNight
46%
540
16%
1609
10%
540
50%
540
30%
995
May11th to 20thNight
45%
531
17%
1417
8%
531
48%
531
33%
909
May21st to endNight
46%
584
14%
1480
5%
582
48%
582
32%
979
June1st to 10thNight
53%
540
17%
1260
7%
540
56%
540
42%
790
June11th to 20thNight
44%
540
12%
1260
5%
540
47%
540
37%
826
June21st to endNight
57%
540
16%
1260
7%
540
61%
540
51%
742
July1st to 10thNight
63%
525
15%
1316
8%
525
65%
525
48%
770
July11th to 20thNight
55%
522
19%
1392
8%
522
59%
522
51%
755
July21st to endNight
64%
591
23%
1488
12%
558
66%
558
54%
767
August1st to 10thNight
63%
537
25%
1439
16%
534
67%
534
47%
790
August11th to 20thNight
60%
534
26%
1600
20%
534
68%
534
44%
856
August21st to endNight
59%
594
29%
1862
27%
594
68%
594
47%
928
September1st to 10thNight
59%
540
25%
1800
23%
540
69%
540
44%
881
September11th to 20thNight
56%
540
26%
1959
27%
540
63%
540
35%
1011
September21st to endNight
44%
540
27%
1980
23%
540
56%
540
31%
1062
October1st to 10thNight
40%
540
22%
1980
18%
540
48%
540
24%
1183
October11th to 20thNight
41%
849
22%
2289
11%
849
48%
849
29%
1481
October21st to endNight
34%
990
22%
2574
7%
990
42%
990
30%
1669
November1st to 10thNight
36%
925
22%
2405
9%
925
44%
925
29%
1576
November11th to 20thNight
39%
950
22%
2473
12%
950
44%
950
26%
1685
November21st to endNight
37%
950
17%
2817
9%
950
45%
950
26%
1802
December1st to 10thNight
34%
950
11%
2850
7%
950
40%
950
18%
2054
December11th to 20thNight
31%
948
13%
3437
8%
948
37%
948
16%
2293
December21st to endNight
29%
1037
10%
5044
7%
1026
37%
1026
10%
3296

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
10%7%37%6%35%5%6%7%41%
78436
Night
8%8%37%6%45%5%6%7%41%
81601
TransparencyDay
41%7%15%25%11%1
78139
Night
41%6%14%26%12%1
81420
SeeingDay
14%9%30%30%14%3
15122
Night
12%7%31%37%12%1
25298

By Month

Percentage Cloud Cover SW (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
49%6%14%14%45%46%8%27%
2538
11th to 20thDay
46%410%10%49%15%11%8%19%
2540
21st to endDay
6%10%5%11%9%5%6%5%6%6%31%
2794
February1st to 10thDay
8%13%7%9%9%5%7%45%7%27%
1543
11th to 20thDay
5%13%5%9%9%5%6%6%7%7%29%
1815
21st to endDay
7%11%5%12%8%46%5%5%7%31%
1570
March1st to 10thDay
9%12%6%9%8%45%447%30%
1900
11th to 20thDay
8%8%38%8%45%5%5%9%36%
2012
21st to endDay
15%11%48%7%35%5%5%7%29%
2349
April1st to 10thDay
10%9%36%6%46%5%6%8%37%
2160
11th to 20thDay
16%11%38%5%35%5%5%6%34%
2237
21st to endDay
17%9%35%5%345%5%7%37%
2340
May1st to 10thDay
15%8%36%5%35%45%6%41%
2348
11th to 20thDay
14%6%36%5%245%6%8%43%
2478
21st to endDay
15%7%35%6%35%5%6%8%38%
2793
June1st to 10thDay
13%5%244345%5%9%45%
2700
11th to 20thDay
12%5%26%435%47%8%44%
2700
21st to endDay
8%424425%5%6%9%51%
2700
July1st to 10thDay
6%314435%5%7%9%52%
2600
11th to 20thDay
6%3134245%6%8%58%
2520
21st to endDay
5%3144245%6%8%58%
2742
August1st to 10thDay
8%5%24435%6%5%7%51%
2490
11th to 20thDay
11%41442445%7%53%
2301
21st to endDay
6%425%423446%58%
2490
September1st to 10thDay
11%424423346%57%
2160
11th to 20thDay
10%41442346%7%54%
1999
21st to endDay
12%6%24424346%53%
1980
October1st to 10thDay
17%6%26%434446%44%
1980
11th to 20thDay
10%8%46%5%3445%8%44%
1650
21st to endDay
12%9%38%5%3346%7%39%
1782
November1st to 10thDay
10%9%47%6%345%5%8%38%
1673
11th to 20thDay
8%10%49%7%45%45%7%37%
1706
21st to endDay
5%10%48%7%36%47%7%37%
1359
December1st to 10thDay
6%11%5%10%8%5%6%5%6%9%30%
1330
11th to 20thDay
7%11%6%8%7%35%5%6%8%33%
1683
21st to endDay
11%10%310%7%45%5%5%6%35%
2474
January1st to 10thNight
5%11%5%12%10%46%6%6%7%30%
4417
11th to 20thNight
47%48%8%6%11%8%9%8%25%
4430
21st to endNight
410%5%10%9%6%7%6%6%6%32%
4873
February1st to 10thNight
8%11%5%8%8%5%6%6%6%7%29%
2636
11th to 20thNight
6%11%48%6%45%5%6%6%38%
2267
21st to endNight
7%9%5%8%7%35%5%5%9%39%
1884
March1st to 10thNight
8%10%5%9%7%45%5%5%6%34%
2280
11th to 20thNight
10%10%37%5%345%47%43%
2167
21st to endNight
12%10%37%7%35%5%6%7%35%
2159
April1st to 10thNight
7%9%37%6%35%6%6%8%41%
1800
11th to 20thNight
13%8%46%5%36%5%7%7%36%
1671
21st to endNight
14%7%25%6%3445%8%41%
1620
May1st to 10thNight
10%7%245%45%6%7%8%43%
1609
11th to 20thNight
11%6%35%5%35%46%9%44%
1417
21st to endNight
12%5%25%4345%7%9%43%
1480
June1st to 10thNight
10%324335%46%9%51%
1260
11th to 20thNight
8%5%25%5%35%5%6%8%48%
1260
21st to endNight
42142245%6%10%58%
1260
July1st to 10thNight
5%3234245%5%8%58%
1356
11th to 20thNight
431332445%10%61%
1440
21st to endNight
422232346%8%63%
1576
August1st to 10thNight
43244235%6%9%59%
1447
11th to 20thNight
5%3244245%48%60%
1600
21st to endNight
5%31432345%8%62%
1862
September1st to 10thNight
8%313223346%64%
1800
11th to 20thNight
8%41343445%7%57%
1959
21st to endNight
12%5%2342245%6%54%
1980
October1st to 10thNight
15%7%24433448%46%
1980
11th to 20thNight
12%7%26%435%45%6%46%
2289
21st to endNight
11%7%35%43445%8%44%
2574
November1st to 10thNight
8%8%25%5%46%6%7%7%42%
2405
11th to 20thNight
7%9%49%7%35%46%6%39%
2473
21st to endNight
6%6%47%6%35%5%6%9%42%
2817
December1st to 10thNight
7%10%6%9%7%47%6%6%6%31%
2850
11th to 20thNight
8%10%49%6%46%5%6%7%35%
3514
21st to endNight
12%11%49%7%35%5%46%33%
5189

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
54%8%16%17%5%
2539
11th to 20thDay
52%8%14%17%8%
2540
21st to endDay
51%8%13%22%6%
2794
February1st to 10thDay
55%7%12%17%7%1
1543
11th to 20thDay
51%7%13%21%7%1
1825
21st to endDay
52%7%14%19%9%
1570
March1st to 10thDay
55%7%15%16%7%
1900
11th to 20thDay
46%6%15%23%10%1
2012
21st to endDay
53%6%17%19%5%
2349
April1st to 10thDay
44%6%16%22%11%1
2160
11th to 20thDay
50%6%13%20%10%1
2240
21st to endDay
47%6%14%25%8%1
2340
May1st to 10thDay
44%5%12%25%13%1
2348
11th to 20thDay
39%6%15%27%13%
2482
21st to endDay
44%8%14%26%8%
2793
June1st to 10thDay
37%7%16%29%10%1
2700
11th to 20thDay
36%7%16%28%12%2
2700
21st to endDay
28%8%20%29%14%1
2700
July1st to 10thDay
26%8%17%33%15%3
2531
11th to 20thDay
23%6%15%32%18%6%
2445
21st to endDay
22%7%14%35%19%3
2590
August1st to 10thDay
31%8%16%27%16%4
2474
11th to 20thDay
30%5%15%34%14%1
2301
21st to endDay
26%6%13%32%20%3
2490
September1st to 10thDay
30%412%33%19%2
2160
11th to 20thDay
29%6%15%34%16%2
1999
21st to endDay
33%5%13%31%16%2
1980
October1st to 10thDay
41%6%14%25%13%1
1980
11th to 20thDay
39%5%12%30%12%1
1650
21st to endDay
43%7%15%23%12%1
1782
November1st to 10thDay
44%7%14%22%13%1
1673
11th to 20thDay
46%7%15%22%10%1
1706
21st to endDay
44%6%19%21%10%
1359
December1st to 10thDay
50%7%15%20%7%1
1330
11th to 20thDay
46%8%19%21%6%
1680
21st to endDay
49%6%10%27%7%
2474
January1st to 10thNight
51%7%12%23%6%
4417
11th to 20thNight
51%7%16%19%7%
4430
21st to endNight
51%8%12%23%6%
4873
February1st to 10thNight
52%6%12%19%10%
2636
11th to 20thNight
45%5%13%25%10%2
2267
21st to endNight
43%5%15%24%12%2
1884
March1st to 10thNight
50%5%14%21%9%
2280
11th to 20thNight
42%413%28%13%
2167
21st to endNight
48%7%17%19%8%1
2159
April1st to 10thNight
39%6%13%25%14%3
1800
11th to 20thNight
47%411%21%15%2
1671
21st to endNight
41%6%13%26%13%1
1620
May1st to 10thNight
37%5%15%26%16%2
1609
11th to 20thNight
36%6%15%24%18%1
1418
21st to endNight
36%8%18%28%10%1
1480
June1st to 10thNight
30%5%16%35%13%2
1260
11th to 20thNight
33%7%17%28%12%2
1260
21st to endNight
20%7%20%33%17%2
1260
July1st to 10thNight
22%8%14%35%17%4
1316
11th to 20thNight
20%5%15%34%20%6%
1392
21st to endNight
18%5%15%34%24%4
1488
August1st to 10thNight
21%7%16%34%17%5%
1439
11th to 20thNight
24%6%14%34%20%4
1600
21st to endNight
20%5%11%35%23%4
1862
September1st to 10thNight
22%412%35%23%3
1800
11th to 20thNight
27%6%15%31%19%2
1959
21st to endNight
31%5%11%35%17%2
1980
October1st to 10thNight
39%5%15%23%17%1
1980
11th to 20thNight
38%5%9%31%14%3
2289
21st to endNight
38%5%14%27%14%2
2574
November1st to 10thNight
38%6%15%22%16%2
2405
11th to 20thNight
44%5%15%23%11%2
2473
21st to endNight
39%7%19%27%9%
2817
December1st to 10thNight
51%7%15%19%7%
2850
11th to 20thNight
46%7%20%20%7%
3516
21st to endNight
52%5%10%24%9%1
5189

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
13%9%29%33%12%4
270
11th to 20thDay
12%13%34%28%9%4
270
21st to endDay
11%11%33%27%14%3
297
February1st to 10thDay
11%12%41%31%4
270
11th to 20thDay
11%10%40%29%9%1
270
21st to endDay
14%8%33%32%13%
225
March1st to 10thDay
23%9%35%23%8%2
270
11th to 20thDay
13%13%35%27%9%3
270
21st to endDay
18%8%39%19%12%3
379
April1st to 10thDay
17%16%37%23%7%
420
11th to 20thDay
25%14%29%22%10%1
518
21st to endDay
21%11%31%24%13%1
600
May1st to 10thDay
17%10%29%28%13%2
603
11th to 20thDay
18%9%27%30%12%3
625
21st to endDay
15%9%30%24%17%4
679
June1st to 10thDay
11%10%24%31%19%5%
630
11th to 20thDay
13%9%37%27%13%2
630
21st to endDay
10%8%28%36%15%2
630
July1st to 10thDay
6%5%27%41%19%2
621
11th to 20thDay
6%7%32%37%17%2
618
21st to endDay
5%427%38%22%3
684
August1st to 10thDay
8%421%40%22%5%
626
11th to 20thDay
11%420%34%23%7%
615
21st to endDay
9%6%26%32%23%4
609
September1st to 10thDay
13%11%30%28%16%2
450
11th to 20thDay
11%6%29%34%17%3
289
21st to endDay
18%14%25%29%13%1
270
October1st to 10thDay
21%9%29%24%16%1
270
11th to 20thDay
14%17%33%22%12%2
270
21st to endDay
22%12%38%22%5%1
297
November1st to 10thDay
21%10%30%29%10%1
270
11th to 20thDay
13%12%35%29%9%2
270
21st to endDay
12%13%31%30%13%1
270
December1st to 10thDay
14%7%37%27%10%4
270
11th to 20thDay
17%10%35%31%6%1
270
21st to endDay
15%11%37%25%8%3
297
January1st to 10thNight
11%10%35%34%10%1
950
11th to 20thNight
13%10%32%33%11%1
950
21st to endNight
10%10%36%36%9%
1045
February1st to 10thNight
15%9%30%37%10%1
950
11th to 20thNight
11%8%35%34%11%1
793
21st to endNight
11%5%29%41%11%3
628
March1st to 10thNight
13%9%34%33%9%2
760
11th to 20thNight
15%7%32%34%11%1
647
21st to endNight
16%6%30%36%11%1
615
April1st to 10thNight
10%9%37%38%6%1
540
11th to 20thNight
17%8%33%33%8%1
533
21st to endNight
19%6%29%31%14%
540
May1st to 10thNight
14%6%28%38%14%
540
11th to 20thNight
14%5%30%39%12%1
531
21st to endNight
14%6%29%37%13%
584
June1st to 10thNight
11%7%27%39%16%1
540
11th to 20thNight
11%6%36%35%13%
540
21st to endNight
6%329%46%15%1
540
July1st to 10thNight
6%224%50%18%
525
11th to 20thNight
4434%44%15%
522
21st to endNight
5%226%52%14%1
591
August1st to 10thNight
5%324%50%17%
537
11th to 20thNight
7%326%43%19%2
534
21st to endNight
6%5%27%44%19%1
594
September1st to 10thNight
9%325%45%16%2
540
11th to 20thNight
8%428%42%17%1
540
21st to endNight
14%6%31%36%12%1
540
October1st to 10thNight
19%7%29%36%9%
540
11th to 20thNight
17%9%27%34%12%1
849
21st to endNight
16%8%36%29%10%1
990
November1st to 10thNight
12%10%35%32%10%1
925
11th to 20thNight
11%10%31%36%10%1
950
21st to endNight
9%11%33%38%8%
950
December1st to 10thNight
12%7%34%35%11%1
950
11th to 20thNight
14%11%30%34%10%1
950
21st to endNight
18%10%27%34%11%
1045
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