Bemidji State University
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bemidji State University 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
34%
16107
13%
46389
7%
16060
40%
16060
21%
32498

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
27%
900
10%
2685
6%
895
31%
895
15%
2036
January16th to endNight
21%
960
11%
2649
3%
960
28%
960
14%
2071
February1st to 15thNight
31%
879
14%
2285
5%
875
37%
875
21%
1653
February16th to endNight
30%
789
13%
2051
5%
789
35%
789
19%
1530
March1st to 15thNight
29%
574
13%
2014
9%
574
36%
574
17%
1404
March16th to endNight
30%
576
15%
2112
10%
576
39%
576
16%
1455
April1st to 15thNight
31%
539
16%
1771
12%
539
41%
539
21%
1201
April16th to endNight
33%
540
15%
1620
11%
540
39%
540
19%
1153
May1st to 15thNight
33%
540
13%
1494
6%
540
36%
540
23%
1058
May16th to endNight
40%
563
12%
1456
4%
561
44%
561
30%
983
June1st to 15thNight
43%
540
9%
1260
4%
540
45%
540
33%
854
June16th to endNight
49%
540
9%
1260
5%
540
51%
540
36%
814
July1st to 15thNight
59%
510
14%
1190
8%
510
61%
510
48%
729
July16th to endNight
59%
564
17%
1322
6%
531
61%
531
45%
790
August1st to 15thNight
64%
527
20%
1575
14%
524
68%
524
42%
842
August16th to endNight
52%
525
21%
1580
18%
525
60%
525
39%
880
September1st to 15thNight
54%
495
18%
1658
17%
495
61%
495
32%
936
September16th to endNight
43%
502
21%
1825
17%
502
53%
502
28%
1044
October1st to 15thNight
35%
660
18%
1980
11%
660
41%
660
24%
1298
October16th to endNight
27%
749
12%
2162
4%
749
33%
749
18%
1572
November1st to 15thNight
28%
875
16%
2451
8%
875
35%
875
20%
1752
November16th to endNight
24%
900
12%
2520
6%
900
28%
900
15%
1950
December1st to 15thNight
20%
900
7%
2589
2%
900
24%
900
12%
2072
December16th to endNight
15%
960
8%
2880
2%
960
21%
960
8%
2421

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%9%37%6%35%45%7%33%
47600
Night
11%9%47%6%35%5%5%6%33%
46546
Cloud CoverDay
11%8%26%5%34446%43%
47610
Night
9%8%36%5%24445%44%
46549
Cloud CoverDay
14%8%36%6%3445%7%33%
47611
Night
12%9%47%6%35%5%5%6%34%
46550
Cloud CoverDay
14%8%37%6%35%45%7%33%
47609
Night
12%9%47%6%35%5%5%6%33%
46550
TransparencyDay
49%413%22%8%
47272
Night
49%413%23%8%
46392
SeeingDay
17%8%28%26%15%3
6052
Night
16%8%31%30%11%1
16108

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
10%10%5%9%8%446%8%8%20%
1253
16th to endDay
11%11%7%14%8%47%6%5%7%15%
1572
February1st to 15thDay
8%11%49%8%46%5%6%6%27%
1575
16th to endDay
10%12%5%8%9%5%6%5%5%6%24%
1425
March1st to 15thDay
15%11%48%6%35%445%30%
1943
16th to endDay
17%11%47%6%25%346%30%
2112
April1st to 15thDay
14%9%36%6%35%45%6%33%
2176
16th to endDay
20%11%36%5%24446%30%
2340
May1st to 15thDay
22%10%46%5%23345%31%
2457
16th to endDay
18%5%345%35%46%7%34%
2656
June1st to 15thDay
16%6%35%5%35%5%5%9%32%
2700
16th to endDay
11%5%35%6%45%5%6%9%36%
2700
July1st to 15thDay
9%425%5%35%5%6%9%43%
2700
16th to endDay
7%3245%36%5%5%9%46%
2753
August1st to 15thDay
9%5%245%35%5%6%8%41%
2289
16th to endDay
12%5%24434446%48%
2269
September1st to 15thDay
13%5%36%5%2335%7%43%
1971
16th to endDay
15%8%25%423346%41%
1793
October1st to 15thDay
19%9%24424336%37%
1650
16th to endDay
23%12%46%5%23346%27%
1707
November1st to 15thDay
12%14%47%5%25%345%33%
1407
16th to endDay
13%14%5%10%10%35%445%22%
1440
December1st to 15thDay
13%13%7%9%9%45%5%6%5%19%
1368
16th to endDay
12%17%7%15%9%45%33415%
1344
January1st to 15thNight
8%10%6%10%9%46%6%8%7%21%
2685
16th to endNight
10%12%6%12%8%45%5%8%8%18%
2649
February1st to 15thNight
7%10%49%6%46%6%7%8%29%
2285
16th to endNight
8%10%48%7%5%7%6%6%7%26%
2051
March1st to 15thNight
11%10%5%7%6%36%5%36%32%
2002
16th to endNight
14%10%37%5%35%5%45%33%
2112
April1st to 15thNight
14%9%46%435%345%38%
1771
16th to endNight
20%9%36%43344433%
1620
May1st to 15thNight
19%8%45%433345%36%
1494
16th to endNight
14%5%24425%5%6%6%41%
1454
June1st to 15thNight
13%5%35%425%45%7%43%
1260
16th to endNight
8%3245%25%5%7%10%43%
1260
July1st to 15thNight
5%32332346%9%55%
1260
16th to endNight
5%32342445%11%52%
1413
August1st to 15thNight
6%21243345%8%56%
1585
16th to endNight
8%32442345%6%54%
1580
September1st to 15thNight
10%425%32345%6%50%
1658
16th to endNight
12%5%24324346%49%
1825
October1st to 15thNight
14%7%24435%45%5%41%
1980
16th to endNight
17%11%46%5%25%446%29%
2162
November1st to 15thNight
12%11%5%8%6%2435%5%33%
2451
16th to endNight
13%11%5%9%8%46%5%5%6%22%
2520
December1st to 15thNight
10%14%7%9%9%5%6%7%6%6%16%
2589
16th to endNight
15%15%8%13%8%44345%15%
2880

Percentage Cloud Cover NW (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
7%9%37%6%435%7%7%35%
1254
16th to endDay
7%11%5%12%5%45%5%5%6%29%
1572
February1st to 15thDay
7%10%38%6%35%5%45%39%
1575
16th to endDay
7%11%46%8%5%5%5%4437%
1425
March1st to 15thDay
11%9%27%5%3343443%
1954
16th to endDay
12%9%37%5%23335%43%
2110
April1st to 15thDay
11%7%25%5%34446%44%
2176
16th to endDay
16%10%36%5%22335%39%
2340
May1st to 15thDay
18%9%25%423235%42%
2457
16th to endDay
15%5%1442445%5%46%
2656
June1st to 15thDay
13%5%3443445%6%43%
2700
16th to endDay
10%4245%3345%7%46%
2700
July1st to 15thDay
8%41442445%7%52%
2700
16th to endDay
5%4144345%5%7%53%
2753
August1st to 15thDay
7%5%244345%6%8%46%
2289
16th to endDay
10%424423345%53%
2269
September1st to 15thDay
12%5%15%42335%7%48%
1971
16th to endDay
12%6%25%413336%49%
1793
October1st to 15thDay
17%9%24423345%41%
1650
16th to endDay
20%11%35%5%13236%36%
1707
November1st to 15thDay
9%11%37%42333444%
1407
16th to endDay
10%12%49%7%3443434%
1440
December1st to 15thDay
9%11%48%7%5%35%5%5%33%
1368
16th to endDay
9%16%5%13%9%3432329%
1344
January1st to 15thNight
6%9%38%8%36%6%6%6%35%
2685
16th to endNight
7%12%49%6%345%7%7%32%
2649
February1st to 15thNight
5%8%47%6%36%5%6%5%40%
2278
16th to endNight
5%9%37%7%5%5%5%5%5%39%
2051
March1st to 15thNight
8%8%36%5%34445%45%
2014
16th to endNight
11%9%26%5%2334446%
2110
April1st to 15thNight
11%8%35%42334448%
1771
16th to endNight
17%9%25%42323342%
1620
May1st to 15thNight
13%8%35%32243447%
1493
16th to endNight
12%42441435%5%50%
1455
June1st to 15thNight
11%315%224435%53%
1260
16th to endNight
6%31442345%9%54%
1260
July1st to 15thNight
5%213212348%63%
1260
16th to endNight
421342345%8%60%
1413
August1st to 15thNight
6%21242335%7%60%
1585
16th to endNight
7%313312446%59%
1580
September1st to 15thNight
9%424422346%54%
1658
16th to endNight
10%413323336%57%
1825
October1st to 15thNight
12%8%24423435%47%
1980
16th to endNight
17%9%35%5%23445%38%
2162
November1st to 15thNight
9%10%45%423435%46%
2451
16th to endNight
9%10%48%7%35%445%36%
2520
December1st to 15thNight
7%11%5%8%7%45%5%5%5%32%
2589
16th to endNight
10%14%5%12%8%3433329%
2880

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 15thDay
11%10%5%9%8%5%46%7%9%21%
1253
16th to endDay
11%11%7%13%8%46%7%5%7%15%
1572
February1st to 15thDay
8%11%49%9%47%5%6%6%27%
1575
16th to endDay
10%12%5%8%8%5%6%5%5%6%24%
1425
March1st to 15thDay
15%11%5%8%6%34445%30%
1954
16th to endDay
17%11%37%6%35%346%31%
2112
April1st to 15thDay
15%9%36%5%35%45%6%34%
2176
16th to endDay
21%11%36%5%24446%30%
2340
May1st to 15thDay
23%10%46%5%33345%31%
2457
16th to endDay
19%5%345%25%5%5%8%34%
2656
June1st to 15thDay
16%6%35%5%345%5%9%33%
2700
16th to endDay
12%5%35%6%35%5%6%9%36%
2700
July1st to 15thDay
9%4245%345%6%9%44%
2700
16th to endDay
7%315%435%5%5%9%46%
2753
August1st to 15thDay
10%5%245%445%7%8%41%
2289
16th to endDay
13%5%24424446%48%
2269
September1st to 15thDay
13%6%26%42335%7%43%
1971
16th to endDay
16%6%35%5%23446%42%
1793
October1st to 15thDay
19%10%245%24345%37%
1650
16th to endDay
23%12%46%423345%27%
1707
November1st to 15thDay
12%15%48%5%25%33434%
1407
16th to endDay
14%14%5%10%9%45%445%21%
1440
December1st to 15thDay
13%12%7%9%8%5%5%5%5%5%19%
1368
16th to endDay
12%17%7%15%10%4433415%
1344
January1st to 15thNight
8%11%6%10%8%46%6%7%6%22%
2685
16th to endNight
10%12%6%12%7%35%6%7%8%18%
2649
February1st to 15thNight
7%10%5%8%6%36%6%6%8%29%
2278
16th to endNight
8%11%48%7%47%5%7%7%26%
2051
March1st to 15thNight
11%10%5%7%6%36%5%46%32%
2014
16th to endNight
14%10%48%5%345%4433%
2112
April1st to 15thNight
14%10%35%5%25%345%38%
1771
16th to endNight
20%9%36%4245%4433%
1620
May1st to 15thNight
19%8%46%424445%37%
1493
16th to endNight
15%5%25%4245%5%7%41%
1454
June1st to 15thNight
13%5%25%325%45%7%43%
1260
16th to endNight
9%3235%25%5%7%10%43%
1260
July1st to 15thNight
6%32341346%8%55%
1260
16th to endNight
5%21342446%10%53%
1413
August1st to 15thNight
7%2125%3345%7%56%
1585
16th to endNight
9%32332345%6%54%
1580
September1st to 15thNight
10%5%2442345%6%50%
1658
16th to endNight
12%5%24323437%49%
1825
October1st to 15thNight
14%8%24425%446%42%
1980
16th to endNight
17%11%46%5%2445%6%30%
2162
November1st to 15thNight
13%11%5%8%5%24345%34%
2451
16th to endNight
13%12%5%9%7%45%5%6%6%22%
2520
December1st to 15thNight
11%14%6%10%8%47%6%6%6%16%
2589
16th to endNight
15%15%8%13%8%44445%15%
2880

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
11%11%410%8%5%45%8%9%20%
1253
16th to endDay
10%12%7%14%8%47%6%6%6%14%
1572
February1st to 15thDay
8%11%5%8%8%5%7%5%6%6%27%
1575
16th to endDay
10%12%47%9%6%7%5%5%7%23%
1425
March1st to 15thDay
15%11%49%6%35%445%30%
1954
16th to endDay
17%10%36%5%34447%30%
2110
April1st to 15thDay
14%9%36%5%35%45%6%34%
2176
16th to endDay
21%11%35%5%3335%6%30%
2340
May1st to 15thDay
22%9%37%5%33335%30%
2457
16th to endDay
18%6%245%35%5%5%7%34%
2656
June1st to 15thDay
16%5%26%6%345%5%9%33%
2700
16th to endDay
11%5%36%5%36%5%6%8%36%
2700
July1st to 15thDay
9%4245%345%6%9%44%
2700
16th to endDay
6%325%435%5%7%9%46%
2753
August1st to 15thDay
9%5%25%6%35%5%6%8%41%
2289
16th to endDay
12%5%1442445%6%47%
2269
September1st to 15thDay
13%6%26%42336%7%42%
1971
16th to endDay
15%6%25%5%33435%42%
1793
October1st to 15thDay
19%10%25%424346%36%
1650
16th to endDay
22%12%47%433446%27%
1707
November1st to 15thDay
12%14%48%6%3434433%
1407
16th to endDay
13%15%5%10%9%44445%20%
1440
December1st to 15thDay
13%12%6%10%9%5%5%5%5%5%18%
1368
16th to endDay
12%18%6%15%10%45%33415%
1344
January1st to 15thNight
8%10%6%10%9%36%6%7%6%22%
2685
16th to endNight
10%12%6%12%8%46%6%7%7%18%
2649
February1st to 15thNight
7%10%48%6%36%6%6%8%29%
2278
16th to endNight
8%10%47%8%5%6%6%7%6%27%
2051
March1st to 15thNight
10%11%5%6%6%46%5%46%32%
2014
16th to endNight
13%11%47%5%35%445%33%
2112
April1st to 15thNight
14%9%46%5%24445%38%
1771
16th to endNight
19%10%36%5%33445%32%
1620
May1st to 15thNight
19%7%46%433445%36%
1493
16th to endNight
15%5%25%4245%5%7%40%
1454
June1st to 15thNight
13%6%25%425%45%7%42%
1260
16th to endNight
9%4235%35%6%6%10%42%
1260
July1st to 15thNight
6%3133135%5%9%54%
1260
16th to endNight
5%32342445%11%53%
1413
August1st to 15thNight
6%31342435%8%55%
1585
16th to endNight
9%31342346%6%53%
1580
September1st to 15thNight
10%42442345%6%50%
1658
16th to endNight
12%5%24413337%49%
1825
October1st to 15thNight
14%8%24435%446%41%
1980
16th to endNight
17%12%36%5%35%45%5%29%
2162
November1st to 15thNight
12%12%5%8%6%24446%33%
2451
16th to endNight
13%11%6%8%9%45%5%5%5%22%
2520
December1st to 15thNight
10%14%6%10%8%47%7%5%6%16%
2589
16th to endNight
15%16%7%13%9%44445%14%
2880

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
56%5%10%21%6%
1254
16th to endDay
66%410%13%4
1572
February1st to 15thDay
56%313%19%7%
1576
16th to endDay
59%410%18%6%
1425
March1st to 15thDay
56%413%18%7%
1954
16th to endDay
55%312%22%4
2112
April1st to 15thDay
49%411%22%11%1
2176
16th to endDay
55%312%18%9%
2340
May1st to 15thDay
56%210%23%6%
2457
16th to endDay
47%5%13%21%11%
2660
June1st to 15thDay
47%5%17%22%6%
2700
16th to endDay
43%6%15%25%8%
2700
July1st to 15thDay
35%6%14%30%12%
2541
16th to endDay
34%6%18%28%11%
2581
August1st to 15thDay
38%5%15%30%8%1
2275
16th to endDay
36%415%29%13%
2269
September1st to 15thDay
39%316%31%7%
1971
16th to endDay
43%315%32%4
1793
October1st to 15thDay
49%315%22%8%
1650
16th to endDay
58%315%16%6%
1707
November1st to 15thDay
53%412%18%10%1
1407
16th to endDay
63%412%11%6%
1440
December1st to 15thDay
64%313%15%2
1368
16th to endDay
73%37%10%5%
1344
January1st to 15thNight
58%410%19%6%
2685
16th to endNight
60%5%10%16%5%
2649
February1st to 15thNight
49%413%24%7%
2288
16th to endNight
54%412%20%7%
2051
March1st to 15thNight
52%413%20%8%
2014
16th to endNight
52%413%20%7%
2112
April1st to 15thNight
48%49%25%11%1
1771
16th to endNight
54%210%18%12%1
1620
May1st to 15thNight
49%411%22%11%
1494
16th to endNight
41%5%13%24%14%1
1456
June1st to 15thNight
40%319%25%10%1
1260
16th to endNight
34%5%22%27%8%1
1260
July1st to 15thNight
25%5%17%34%15%1
1190
16th to endNight
26%5%17%32%15%1
1322
August1st to 15thNight
26%415%39%12%2
1575
16th to endNight
29%415%33%15%2
1580
September1st to 15thNight
33%418%34%9%
1658
16th to endNight
35%413%36%9%
1825
October1st to 15thNight
43%413%27%9%
1980
16th to endNight
54%414%22%4
2162
November1st to 15thNight
52%213%20%9%1
2451
16th to endNight
59%5%13%13%6%
2520
December1st to 15thNight
64%413%13%3
2589
16th to endNight
72%38%11%4
2880

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
20%12%35%17%13%1
90
16th to endDay
16%6%34%29%12%1
96
February1st to 15thDay
15%18%37%25%2
90
16th to endDay
27%248%17%31
81
March1st to 15thDay
20%8%31%26%13%
90
16th to endDay
15%6%35%19%19%3
96
April1st to 15thDay
14%11%37%25%10%
295
16th to endDay
30%8%26%21%12%1
450
May1st to 15thDay
26%11%27%22%9%2
468
16th to endDay
22%8%28%25%11%3
517
June1st to 15thDay
17%10%31%25%11%3
495
16th to endDay
13%10%31%25%14%5%
495
July1st to 15thDay
11%7%21%29%22%7%
475
16th to endDay
7%6%27%27%22%8%
515
August1st to 15thDay
9%5%20%33%24%6%
474
16th to endDay
14%6%23%32%18%4
437
September1st to 15thDay
13%423%35%19%2
246
16th to endDay
17%6%34%25%15%
90
October1st to 15thDay
20%238%27%6%4
90
16th to endDay
32%10%22%23%8%2
96
November1st to 15thDay
14%10%26%27%18%2
90
16th to endDay
42%11%23%20%3
90
December1st to 15thDay
13%8%38%28%10%
90
16th to endDay
16%14%31%27%5%5%
96
January1st to 15thNight
14%10%34%26%10%2
900
16th to endNight
16%11%39%27%6%
960
February1st to 15thNight
12%10%32%30%11%1
880
16th to endNight
13%8%35%29%9%3
789
March1st to 15thNight
15%8%37%26%10%1
574
16th to endNight
18%9%29%26%12%2
576
April1st to 15thNight
19%7%34%28%8%
539
16th to endNight
25%6%26%28%11%
540
May1st to 15thNight
23%7%30%29%8%
540
16th to endNight
18%331%35%9%1
563
June1st to 15thNight
15%5%29%38%10%
540
16th to endNight
10%6%26%37%18%
540
July1st to 15thNight
7%324%42%20%1
510
16th to endNight
7%323%41%22%1
564
August1st to 15thNight
8%219%45%21%2
527
16th to endNight
11%5%27%33%20%1
525
September1st to 15thNight
12%5%23%33%21%3
495
16th to endNight
11%7%31%30%15%2
502
October1st to 15thNight
18%9%29%31%10%
660
16th to endNight
24%9%31%27%7%
749
November1st to 15thNight
17%11%34%27%7%1
875
16th to endNight
19%11%35%24%7%1
900
December1st to 15thNight
16%11%35%27%8%
900
16th to endNight
23%9%32%25%6%1
960
Page generated at 2017-08-13 13:16:56. Version ac04

Copyright 2017 A. Danko


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