UWSP Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the UWSP Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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%
24816
16%
74702
9%
24759
41%
24759
21%
51163

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
21%
950
13%
2648
5%
946
29%
946
17%
1951
January11th to 20thNight
20%
930
11%
2603
4%
930
27%
930
14%
2008
January21st to endNight
20%
990
10%
2735
2%
990
26%
990
13%
2141
February1st to 10thNight
23%
900
13%
2340
2%
900
30%
900
19%
1714
February11th to 20thNight
25%
802
18%
2197
6%
798
34%
798
19%
1544
February21st to endNight
21%
592
16%
1776
5%
592
31%
592
15%
1295
March1st to 10thNight
31%
720
16%
2160
10%
720
36%
720
20%
1452
March11th to 20thNight
28%
622
20%
2062
11%
622
39%
622
20%
1341
March21st to endNight
34%
594
18%
2015
15%
594
41%
594
19%
1377
April1st to 10thNight
25%
540
15%
1800
9%
540
35%
540
18%
1250
April11th to 20thNight
32%
533
18%
1775
13%
533
41%
533
20%
1197
April21st to endNight
31%
540
16%
1714
9%
540
41%
540
21%
1169
May1st to 10thNight
29%
540
13%
1476
7%
540
34%
540
21%
1068
May11th to 20thNight
36%
531
18%
1417
9%
531
43%
531
26%
984
May21st to endNight
50%
583
13%
1552
6%
582
54%
582
29%
1039
June1st to 10thNight
47%
540
13%
1440
5%
540
51%
540
33%
917
June11th to 20thNight
41%
540
14%
1440
6%
540
45%
540
29%
951
June21st to endNight
54%
540
17%
1440
8%
540
58%
540
36%
890
July1st to 10thNight
64%
525
18%
1400
9%
525
66%
525
45%
796
July11th to 20thNight
59%
522
19%
1392
10%
522
63%
522
38%
847
July21st to endNight
65%
591
21%
1487
13%
558
68%
558
44%
854
August1st to 10thNight
64%
537
23%
1423
17%
534
67%
534
39%
876
August11th to 20thNight
58%
534
20%
1668
17%
534
64%
534
30%
1012
August21st to endNight
58%
594
21%
1980
22%
594
63%
594
31%
1144
September1st to 10thNight
55%
540
22%
1800
22%
540
60%
540
32%
1026
September11th to 20thNight
52%
568
28%
1828
24%
568
59%
568
34%
1034
September21st to endNight
46%
720
20%
1980
13%
720
52%
720
31%
1256
October1st to 10thNight
45%
720
21%
2142
14%
720
51%
720
29%
1322
October11th to 20thNight
31%
720
17%
2160
8%
720
40%
720
21%
1460
October21st to endNight
29%
792
14%
2560
9%
792
36%
792
17%
1805
November1st to 10thNight
30%
740
22%
2406
12%
740
43%
740
23%
1519
November11th to 20thNight
21%
840
15%
2550
6%
840
30%
840
16%
1833
November21st to endNight
24%
950
16%
2660
7%
950
32%
950
19%
1896
December1st to 10thNight
21%
950
11%
2660
3%
950
29%
950
17%
1969
December11th to 20thNight
18%
948
12%
3211
3%
948
25%
948
11%
2443
December21st to endNight
16%
1038
7%
4805
4%
1026
23%
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
14%8%47%6%35%5%5%7%36%
74811
Night
14%9%47%5%3445%6%38%
75031
TransparencyDay
46%7%13%22%11%1
74511
Night
46%6%12%22%12%1
74851
SeeingDay
17%10%29%26%13%4
14815
Night
17%10%31%30%11%1
24826

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%11%8%8%7%45%5%5%6%30%
1517
11th to 20thDay
12%15%7%13%7%46%5%5%6%21%
1485
21st to endDay
12%15%7%13%8%45%45%7%23%
1620
February1st to 10thDay
10%11%6%8%6%36%5%6%7%32%
1620
11th to 20thDay
11%10%47%7%35%5%5%7%35%
1650
21st to endDay
12%11%5%10%6%46%5%48%28%
1480
March1st to 10thDay
14%10%6%6%6%35%5%5%7%36%
1800
11th to 20thDay
13%8%5%7%6%445%47%38%
1913
21st to endDay
18%10%47%5%35%46%7%32%
2340
April1st to 10thDay
15%11%5%7%7%35%5%5%7%31%
2160
11th to 20thDay
20%10%46%5%3445%6%33%
2134
21st to endDay
19%10%46%6%45%5%46%31%
2245
May1st to 10thDay
17%7%37%6%36%5%6%8%33%
2480
11th to 20thDay
17%7%37%6%3445%7%38%
2479
21st to endDay
14%6%36%6%45%5%6%8%39%
2725
June1st to 10thDay
13%5%245%35%45%9%44%
2520
11th to 20thDay
15%5%26%6%36%5%6%9%39%
2520
21st to endDay
12%5%25%6%45%5%7%9%40%
2520
July1st to 10thDay
6%325%5%45%6%7%11%47%
2520
11th to 20thDay
9%325%5%46%6%7%9%46%
2520
21st to endDay
9%435%5%35%6%6%8%48%
2743
August1st to 10thDay
8%5%25%6%46%6%7%10%41%
2507
11th to 20thDay
13%5%25%5%445%5%8%43%
2231
21st to endDay
13%5%26%5%345%48%46%
2376
September1st to 10thDay
16%5%3444446%6%44%
2160
11th to 20thDay
14%5%25%3345%6%7%46%
2113
21st to endDay
15%7%36%445%5%6%7%38%
1980
October1st to 10thDay
15%7%26%6%3345%7%41%
1817
11th to 20thDay
19%12%36%5%34447%31%
1800
21st to endDay
18%11%46%6%23446%36%
1796
November1st to 10thDay
14%9%45%6%2345%7%42%
1672
11th to 20thDay
15%11%5%9%7%445%5%5%29%
1627
21st to endDay
15%10%48%5%4445%6%35%
1520
December1st to 10thDay
13%12%5%10%7%46%6%5%5%28%
1520
11th to 20thDay
12%14%6%10%7%45%5%5%6%25%
1918
21st to endDay
20%20%8%10%6%3334318%
2783
January1st to 10thNight
12%11%6%9%7%45%436%32%
2648
11th to 20thNight
13%13%7%11%8%45%45%5%27%
2603
21st to endNight
12%14%7%10%8%46%5%5%6%23%
2735
February1st to 10thNight
9%12%6%10%6%4445%6%33%
2340
11th to 20thNight
10%8%5%7%6%46%5%46%38%
2196
21st to endNight
17%11%48%8%345%45%32%
1776
March1st to 10thNight
13%9%45%5%35%5%5%7%39%
2160
11th to 20thNight
13%8%47%6%34446%40%
2062
21st to endNight
18%10%36%6%2445%6%36%
2015
April1st to 10thNight
19%9%47%5%3445%5%35%
1800
11th to 20thNight
22%7%35%5%2445%6%37%
1775
21st to endNight
18%9%26%5%35%5%5%6%37%
1714
May1st to 10thNight
19%8%36%6%4445%6%34%
1476
11th to 20thNight
17%6%36%5%3446%7%39%
1416
21st to endNight
12%6%25%5%35%5%7%7%42%
1551
June1st to 10thNight
11%5%35%5%35%5%6%8%46%
1440
11th to 20thNight
12%5%36%6%345%6%8%42%
1440
21st to endNight
10%425%5%3446%8%49%
1440
July1st to 10thNight
7%3135%2347%9%55%
1440
11th to 20thNight
8%43342447%9%51%
1440
21st to endNight
7%4135%2445%8%57%
1575
August1st to 10thNight
8%325%435%46%8%51%
1432
11th to 20thNight
10%6%35%5%3445%8%49%
1668
21st to endNight
11%5%2442445%7%51%
1980
September1st to 10thNight
10%5%2443445%7%52%
1800
11th to 20thNight
13%42342435%7%54%
1828
21st to endNight
13%6%35%4245%48%47%
1980
October1st to 10thNight
13%6%35%425%45%7%48%
2142
11th to 20thNight
16%8%36%5%25%5%5%7%37%
2160
21st to endNight
18%12%36%5%34446%34%
2560
November1st to 10thNight
15%9%35%43445%6%44%
2406
11th to 20thNight
14%11%5%8%7%35%5%45%34%
2550
21st to endNight
14%11%49%5%34446%36%
2660
December1st to 10thNight
13%11%5%10%6%35%5%5%7%31%
2660
11th to 20thNight
12%14%6%10%7%45%5%45%28%
3279
21st to endNight
25%15%6%9%5%3343422%
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
54%6%12%19%9%1
1518
11th to 20thDay
63%6%11%11%7%1
1485
21st to endDay
61%5%12%14%7%1
1620
February1st to 10thDay
51%5%14%18%10%1
1620
11th to 20thDay
49%6%12%22%10%2
1659
21st to endDay
54%7%11%17%9%2
1480
March1st to 10thDay
49%6%14%20%10%1
1800
11th to 20thDay
47%6%13%20%13%2
1913
21st to endDay
51%6%12%21%8%1
2340
April1st to 10thDay
52%7%11%19%11%1
2160
11th to 20thDay
52%6%8%21%11%2
2134
21st to endDay
53%7%10%18%11%1
2245
May1st to 10thDay
47%8%14%21%9%1
2480
11th to 20thDay
45%6%12%23%12%1
2483
21st to endDay
43%8%12%22%13%2
2725
June1st to 10thDay
36%7%14%28%13%1
2520
11th to 20thDay
41%8%13%25%13%1
2520
21st to endDay
38%8%15%26%12%1
2520
July1st to 10thDay
30%9%17%30%13%2
2451
11th to 20thDay
31%9%16%27%15%3
2445
21st to endDay
32%8%16%25%17%2
2591
August1st to 10thDay
36%10%16%27%10%2
2492
11th to 20thDay
38%8%14%27%12%
2231
21st to endDay
37%5%13%27%16%1
2376
September1st to 10thDay
39%6%12%26%16%1
2160
11th to 20thDay
36%8%17%31%8%1
2113
21st to endDay
43%8%13%26%11%
1980
October1st to 10thDay
42%7%11%30%10%
1817
11th to 20thDay
52%6%12%20%8%1
1800
21st to endDay
51%413%21%10%1
1796
November1st to 10thDay
42%6%13%23%15%1
1672
11th to 20thDay
56%6%11%19%8%1
1627
21st to endDay
50%5%15%22%6%1
1520
December1st to 10thDay
57%6%12%19%5%1
1520
11th to 20thDay
57%7%14%13%7%2
1915
21st to endDay
70%6%7%12%5%
2783
January1st to 10thNight
54%5%11%19%10%1
2648
11th to 20thNight
58%7%12%16%7%
2603
21st to endNight
60%6%9%14%9%
2735
February1st to 10thNight
52%5%10%21%10%1
2340
11th to 20thNight
46%8%11%23%11%2
2197
21st to endNight
54%6%10%18%10%2
1776
March1st to 10thNight
45%7%14%22%10%3
2160
11th to 20thNight
44%6%11%23%14%2
2062
21st to endNight
49%6%9%22%13%2
2015
April1st to 10thNight
50%5%8%18%17%2
1800
11th to 20thNight
47%6%9%21%13%4
1775
21st to endNight
45%7%12%20%14%2
1714
May1st to 10thNight
51%6%13%16%14%1
1476
11th to 20thNight
44%6%11%25%11%2
1417
21st to endNight
38%8%15%22%15%1
1552
June1st to 10thNight
33%9%14%27%16%1
1440
11th to 20thNight
39%7%13%24%15%2
1440
21st to endNight
32%6%16%30%12%4
1440
July1st to 10thNight
24%7%15%33%19%3
1400
11th to 20thNight
28%9%16%25%19%2
1392
21st to endNight
25%7%16%30%18%4
1487
August1st to 10thNight
29%8%14%31%15%2
1423
11th to 20thNight
33%9%14%26%17%1
1668
21st to endNight
32%7%14%24%20%3
1980
September1st to 10thNight
31%7%12%29%20%1
1800
11th to 20thNight
31%6%14%34%15%1
1828
21st to endNight
36%6%13%31%13%1
1980
October1st to 10thNight
36%7%11%31%14%2
2142
11th to 20thNight
44%7%14%24%10%1
2160
21st to endNight
52%6%11%20%11%
2560
November1st to 10thNight
42%5%12%24%15%2
2406
11th to 20thNight
52%6%13%16%12%1
2550
21st to endNight
49%6%14%24%6%1
2660
December1st to 10thNight
53%6%14%21%6%
2660
11th to 20thNight
58%6%11%18%6%1
3281
21st to endNight
65%6%8%15%5%
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
16%14%31%26%10%2
270
11th to 20thDay
20%13%37%21%7%1
257
21st to endDay
23%10%32%29%6%
264
February1st to 10thDay
15%16%40%23%5%
240
11th to 20thDay
18%21%35%18%8%
240
21st to endDay
20%17%44%18%11
198
March1st to 10thDay
18%15%41%19%7%
240
11th to 20thDay
22%13%31%23%9%2
240
21st to endDay
27%12%31%22%8%1
426
April1st to 10thDay
25%14%30%26%3
420
11th to 20thDay
29%13%27%19%10%2
412
21st to endDay
21%14%32%20%12%1
420
May1st to 10thDay
20%13%31%26%8%1
563
11th to 20thDay
20%11%31%23%11%4
625
21st to endDay
19%9%27%26%13%6%
679
June1st to 10thDay
11%8%29%31%15%6%
630
11th to 20thDay
17%8%29%28%15%4
630
21st to endDay
14%7%28%31%15%5%
630
July1st to 10thDay
7%321%34%26%10%
621
11th to 20thDay
8%6%26%35%16%9%
618
21st to endDay
7%427%33%21%8%
684
August1st to 10thDay
10%423%30%23%9%
626
11th to 20thDay
13%6%20%24%25%11%
536
21st to endDay
15%6%20%29%22%8%
495
September1st to 10thDay
17%8%21%28%18%7%
450
11th to 20thDay
13%6%21%35%19%5%
450
21st to endDay
18%11%27%25%15%3
450
October1st to 10thDay
17%13%27%23%16%4
287
11th to 20thDay
24%17%33%19%7%
270
21st to endDay
24%16%36%19%42
297
November1st to 10thDay
17%15%36%21%10%1
270
11th to 20thDay
17%20%36%21%5%
270
21st to endDay
20%16%41%16%7%
270
December1st to 10thDay
18%15%42%17%7%
270
11th to 20thDay
18%20%38%19%5%1
270
21st to endDay
28%18%34%15%4
297
January1st to 10thNight
17%12%38%26%6%1
950
11th to 20thNight
19%12%35%27%6%1
930
21st to endNight
19%9%37%27%7%
990
February1st to 10thNight
15%12%37%30%5%1
900
11th to 20thNight
16%13%38%25%8%
802
21st to endNight
22%15%35%24%4
592
March1st to 10thNight
17%14%32%28%8%1
720
11th to 20thNight
19%11%36%25%9%
622
21st to endNight
20%11%28%31%8%2
594
April1st to 10thNight
22%11%36%24%7%
540
11th to 20thNight
24%9%31%29%7%
533
21st to endNight
22%10%32%29%7%1
540
May1st to 10thNight
22%8%35%28%6%1
540
11th to 20thNight
19%9%31%31%9%1
531
21st to endNight
15%6%23%40%16%
584
June1st to 10thNight
13%6%27%39%14%1
540
11th to 20thNight
14%5%31%37%13%1
540
21st to endNight
10%5%23%45%15%1
540
July1st to 10thNight
8%219%43%26%2
525
11th to 20thNight
8%422%43%20%2
522
21st to endNight
7%319%46%22%2
591
August1st to 10thNight
9%216%47%24%2
537
11th to 20thNight
12%318%35%28%4
534
21st to endNight
13%320%41%19%3
594
September1st to 10thNight
13%423%38%17%5%
540
11th to 20thNight
13%5%26%34%19%3
568
21st to endNight
16%7%25%35%16%1
720
October1st to 10thNight
16%8%26%30%20%1
720
11th to 20thNight
19%12%32%29%7%
720
21st to endNight
23%12%31%26%8%1
792
November1st to 10thNight
19%9%37%26%8%1
740
11th to 20thNight
19%15%37%22%7%
840
21st to endNight
21%15%35%23%6%
950
December1st to 10thNight
20%11%39%24%6%
950
11th to 20thNight
21%14%34%25%6%1
950
21st to endNight
27%13%33%23%4
1045
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