Wever
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wever 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%
15830
19%
46509
10%
15786
43%
15786
23%
29909

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
23%
900
16%
2506
6%
895
31%
895
19%
1742
January16th to endNight
18%
960
16%
2505
3%
960
27%
960
18%
1783
February1st to 15thNight
20%
877
13%
2288
3%
876
26%
876
18%
1642
February16th to endNight
25%
642
22%
1904
7%
642
37%
642
20%
1219
March1st to 15thNight
27%
630
19%
2070
11%
630
37%
630
19%
1326
March16th to endNight
25%
576
13%
2055
9%
576
32%
576
15%
1436
April1st to 15thNight
26%
539
17%
1797
11%
539
37%
539
20%
1155
April16th to endNight
28%
540
18%
1800
10%
540
41%
540
17%
1199
May1st to 15thNight
31%
540
18%
1554
10%
540
40%
540
21%
1045
May16th to endNight
40%
563
20%
1497
9%
561
49%
561
28%
953
June1st to 15thNight
47%
540
17%
1440
8%
540
53%
540
30%
876
June16th to endNight
42%
540
18%
1440
7%
540
49%
540
30%
896
July1st to 15thNight
61%
510
18%
1360
11%
510
63%
510
38%
807
July16th to endNight
61%
564
24%
1469
16%
531
70%
531
40%
814
August1st to 15thNight
66%
527
23%
1575
23%
524
69%
524
37%
871
August16th to endNight
65%
525
21%
1750
22%
525
71%
525
33%
983
September1st to 15thNight
57%
495
29%
1650
29%
495
62%
495
32%
903
September16th to endNight
56%
583
28%
1784
18%
583
66%
583
36%
981
October1st to 15thNight
45%
660
27%
1980
19%
660
52%
660
32%
1144
October16th to endNight
34%
704
23%
2126
11%
704
45%
704
27%
1298
November1st to 15thNight
31%
700
25%
2276
14%
700
44%
700
25%
1324
November16th to endNight
22%
855
19%
2475
7%
855
34%
855
21%
1641
December1st to 15thNight
21%
900
14%
2520
5%
900
28%
900
16%
1825
December16th to endNight
18%
960
15%
2688
4%
960
28%
960
14%
2046

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%7%36%5%3445%7%39%
47466
Night
12%7%35%424446%43%
46683
Cloud CoverDay
13%7%36%5%3445%7%39%
47475
Night
13%7%35%424446%43%
46687
TransparencyDay
43%5%12%23%13%1
47158
Night
40%412%23%15%2
46510
SeeingDay
13%14%22%26%17%4
5818
Night
14%21%25%26%11%1
15833

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
12%11%410%5%35%346%31%
1432
16th to endDay
14%13%5%8%6%34445%27%
1719
February1st to 15thDay
12%10%49%6%25%5%46%32%
1575
16th to endDay
12%11%46%6%34447%35%
1567
March1st to 15thDay
14%9%36%435%45%5%36%
1888
16th to endDay
16%9%47%5%3345%7%31%
2169
April1st to 15thDay
15%10%37%5%24336%37%
2151
16th to endDay
20%7%26%5%23346%34%
2160
May1st to 15thDay
19%7%36%5%34446%33%
2394
16th to endDay
14%6%26%5%35%45%7%37%
2617
June1st to 15thDay
9%5%36%5%45%46%7%41%
2520
16th to endDay
7%425%5%35%5%6%9%43%
2520
July1st to 15thDay
7%324445%5%6%9%46%
2520
16th to endDay
4424436%5%7%10%47%
2596
August1st to 15thDay
7%425%5%36%5%7%9%43%
2289
16th to endDay
10%415%5%34448%47%
2100
September1st to 15thDay
12%3234236%5%7%48%
1980
16th to endDay
7%5%24435%5%5%6%49%
1833
October1st to 15thDay
14%5%24413346%49%
1650
16th to endDay
16%7%24323426%45%
1746
November1st to 15thDay
13%7%34423447%44%
1582
16th to endDay
17%10%35%412346%38%
1482
December1st to 15thDay
19%11%37%5%35%345%29%
1440
16th to endDay
19%12%6%7%5%24345%27%
1536
January1st to 15thNight
12%8%46%5%35%446%37%
2506
16th to endNight
11%10%6%7%5%33346%35%
2505
February1st to 15thNight
14%10%47%5%24447%34%
2285
16th to endNight
13%8%36%423245%44%
1904
March1st to 15thNight
15%8%25%334345%43%
2058
16th to endNight
17%9%35%6%35%45%6%32%
2055
April1st to 15thNight
14%8%35%423446%41%
1797
16th to endNight
19%6%25%6%24445%39%
1800
May1st to 15thNight
16%6%25%43345%7%39%
1554
16th to endNight
9%425%5%35%45%9%44%
1496
June1st to 15thNight
10%32442445%9%49%
1440
16th to endNight
7%425%5%245%6%10%46%
1440
July1st to 15thNight
5%3243245%7%8%51%
1440
16th to endNight
43234245%6%10%52%
1569
August1st to 15thNight
431332447%8%54%
1585
16th to endNight
7%5%14434346%54%
1750
September1st to 15thNight
12%423312347%54%
1650
16th to endNight
7%3144345%6%8%52%
1784
October1st to 15thNight
11%5%13423346%53%
1980
16th to endNight
13%6%25%323445%47%
2126
November1st to 15thNight
12%7%23223336%51%
2276
16th to endNight
16%7%25%424346%41%
2475
December1st to 15thNight
18%9%47%5%23345%34%
2520
16th to endNight
20%12%5%7%5%2334430%
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
12%11%5%10%5%45%346%31%
1432
16th to endDay
15%13%6%7%6%245%45%27%
1719
February1st to 15thDay
12%10%5%8%6%25%5%46%32%
1575
16th to endDay
12%11%46%6%34446%35%
1567
March1st to 15thDay
14%9%36%5%34446%36%
1899
16th to endDay
16%10%47%5%3445%6%32%
2167
April1st to 15thDay
15%10%37%5%23326%37%
2151
16th to endDay
21%7%26%5%24446%34%
2160
May1st to 15thDay
19%7%36%5%35%446%33%
2394
16th to endDay
14%6%36%6%35%45%7%36%
2617
June1st to 15thDay
9%5%26%6%35%46%7%42%
2520
16th to endDay
8%425%5%35%5%6%9%43%
2520
July1st to 15thDay
7%324445%5%6%9%46%
2520
16th to endDay
4424426%5%7%10%47%
2596
August1st to 15thDay
7%325%5%35%5%7%9%43%
2289
16th to endDay
10%415%5%245%48%47%
2100
September1st to 15thDay
12%3243235%5%7%48%
1980
16th to endDay
7%424435%5%5%7%49%
1833
October1st to 15thDay
14%5%24414346%49%
1650
16th to endDay
17%6%24323436%45%
1746
November1st to 15thDay
14%7%35%313447%44%
1582
16th to endDay
18%9%35%422447%37%
1482
December1st to 15thDay
19%12%47%5%34345%29%
1440
16th to endDay
19%13%5%8%5%24345%27%
1536
January1st to 15thNight
12%8%47%5%45%446%37%
2506
16th to endNight
11%10%6%7%6%34346%35%
2505
February1st to 15thNight
14%10%47%5%25%346%35%
2278
16th to endNight
13%8%36%423345%43%
1904
March1st to 15thNight
15%8%34424345%43%
2070
16th to endNight
16%9%45%6%35%45%6%32%
2055
April1st to 15thNight
15%8%36%4235%46%41%
1797
16th to endNight
19%6%25%6%24345%39%
1800
May1st to 15thNight
16%6%25%43445%8%39%
1553
16th to endNight
8%425%6%35%46%9%44%
1496
June1st to 15thNight
10%3143235%5%9%49%
1440
16th to endNight
7%426%4345%5%10%46%
1440
July1st to 15thNight
5%4143345%7%8%51%
1440
16th to endNight
43234245%6%10%52%
1569
August1st to 15thNight
431432446%8%55%
1585
16th to endNight
7%414433446%54%
1750
September1st to 15thNight
12%414312346%54%
1650
16th to endNight
6%2144345%5%8%52%
1784
October1st to 15thNight
12%423323346%53%
1980
16th to endNight
14%5%25%42335%5%47%
2126
November1st to 15thNight
12%7%23313336%51%
2276
16th to endNight
16%7%25%42435%5%41%
2475
December1st to 15thNight
18%9%47%5%2334434%
2520
16th to endNight
20%12%5%7%42344430%
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
54%411%18%11%
1433
16th to endDay
56%5%13%17%6%
1719
February1st to 15thDay
52%417%19%5%
1576
16th to endDay
48%5%13%21%10%
1567
March1st to 15thDay
48%416%21%7%1
1899
16th to endDay
51%5%14%20%7%1
2169
April1st to 15thDay
50%211%23%11%
2151
16th to endDay
50%410%20%11%1
2160
May1st to 15thDay
50%6%10%22%9%
2394
16th to endDay
45%7%12%18%14%1
2621
June1st to 15thDay
40%6%11%23%15%1
2520
16th to endDay
35%8%13%23%16%2
2520
July1st to 15thDay
33%7%13%27%14%3
2371
16th to endDay
30%7%16%27%17%
2434
August1st to 15thDay
33%8%15%25%15%
2275
16th to endDay
35%5%11%26%16%4
2100
September1st to 15thDay
32%5%11%26%19%4
1980
16th to endDay
32%5%12%30%17%2
1833
October1st to 15thDay
36%49%25%22%1
1650
16th to endDay
40%412%25%14%2
1746
November1st to 15thDay
39%411%23%18%2
1582
16th to endDay
47%414%23%9%
1482
December1st to 15thDay
57%413%18%5%
1440
16th to endDay
59%410%15%8%1
1536
January1st to 15thNight
47%413%19%13%
2506
16th to endNight
50%316%20%9%
2505
February1st to 15thNight
49%413%21%10%
2288
16th to endNight
42%413%26%12%1
1904
March1st to 15thNight
43%412%26%10%1
2070
16th to endNight
52%5%13%20%8%
2055
April1st to 15thNight
43%49%24%14%3
1797
16th to endNight
47%411%19%14%3
1800
May1st to 15thNight
42%6%13%22%14%
1554
16th to endNight
35%7%14%21%19%2
1498
June1st to 15thNight
31%6%15%25%19%2
1440
16th to endNight
32%7%12%22%20%4
1440
July1st to 15thNight
28%5%14%29%16%4
1360
16th to endNight
24%5%16%28%22%1
1469
August1st to 15thNight
25%7%14%30%18%3
1575
16th to endNight
30%6%10%25%20%7%
1750
September1st to 15thNight
31%49%27%22%5%
1650
16th to endNight
27%413%29%22%2
1784
October1st to 15thNight
32%310%24%24%4
1980
16th to endNight
38%410%27%17%2
2126
November1st to 15thNight
35%411%23%20%4
2276
16th to endNight
43%412%26%12%
2475
December1st to 15thNight
52%413%21%7%
2520
16th to endNight
58%410%17%8%
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
31%10%37%15%5%
90
16th to endDay
20%16%32%20%9%
96
February1st to 15thDay
15%15%42%14%12%
90
16th to endDay
17%18%28%25%6%3
81
March1st to 15thDay
25%13%42%13%5%
90
16th to endDay
30%15%28%16%7%1
153
April1st to 15thDay
16%22%27%22%10%
270
16th to endDay
23%17%25%20%10%2
270
May1st to 15thDay
17%23%26%21%9%1
423
16th to endDay
16%18%25%24%10%4
517
June1st to 15thDay
9%14%20%33%17%4
495
16th to endDay
7%18%26%29%15%2
495
July1st to 15thDay
10%10%18%31%21%8%
475
16th to endDay
5%12%13%33%27%6%
515
August1st to 15thDay
6%8%14%31%29%9%
474
16th to endDay
8%8%12%25%35%9%
268
September1st to 15thDay
10%8%14%32%26%6%
255
16th to endDay
7%10%18%24%30%8%
209
October1st to 15thDay
13%8%24%23%17%12%
90
16th to endDay
22%8%31%30%7%
96
November1st to 15thDay
36%30%33%17%8%
90
16th to endDay
40%18%24%13%3
90
December1st to 15thDay
21%23%27%16%10%1
90
16th to endDay
31%19%40%6%2
96
January1st to 15thNight
13%27%30%21%7%
900
16th to endNight
14%26%31%23%3
960
February1st to 15thNight
17%25%30%21%4
880
16th to endNight
16%24%31%23%4
642
March1st to 15thNight
16%25%26%25%6%
630
16th to endNight
17%24%27%22%7%
576
April1st to 15thNight
17%25%28%23%4
539
16th to endNight
19%22%25%24%7%
540
May1st to 15thNight
16%22%26%24%8%1
540
16th to endNight
9%19%24%31%14%1
563
June1st to 15thNight
9%19%17%36%15%1
540
16th to endNight
7%18%26%31%15%
540
July1st to 15thNight
7%12%12%40%25%1
510
16th to endNight
5%17%9%38%27%2
564
August1st to 15thNight
6%10%9%38%31%3
527
16th to endNight
7%10%10%35%33%2
525
September1st to 15thNight
13%11%13%32%25%4
495
16th to endNight
7%12%18%29%27%5%
583
October1st to 15thNight
13%12%24%27%19%2
660
16th to endNight
14%17%30%29%7%
704
November1st to 15thNight
14%22%30%23%9%
700
16th to endNight
16%24%32%19%6%
855
December1st to 15thNight
21%26%26%21%4
900
16th to endNight
22%26%27%20%3
960
Page generated at 2017-08-13 13:16:31. Version ac04

Copyright 2017 A. Danko


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