Grundmeier
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grundmeier clear sky chart from 2005-11-05 to 2017-09-21.

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
37%
16035
20%
46968
11%
15989
45%
15989
28%
29169

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
24%
900
18%
2386
6%
895
34%
895
26%
1574
January16th to endNight
21%
960
19%
2496
5%
960
32%
960
22%
1743
February1st to 15thNight
22%
880
12%
2288
3%
876
27%
876
21%
1668
February16th to endNight
25%
729
22%
1991
6%
729
37%
729
27%
1301
March1st to 15thNight
35%
540
21%
1980
14%
540
45%
540
24%
1156
March16th to endNight
27%
576
14%
2112
8%
576
36%
576
16%
1408
April1st to 15thNight
29%
539
18%
1845
12%
539
41%
539
23%
1127
April16th to endNight
29%
540
18%
1644
11%
540
41%
540
21%
1117
May1st to 15thNight
39%
540
18%
1620
12%
540
46%
540
28%
1019
May16th to endNight
42%
562
16%
1529
7%
561
48%
561
30%
983
June1st to 15thNight
49%
540
17%
1440
7%
540
53%
540
35%
893
June16th to endNight
53%
540
21%
1440
8%
540
58%
540
48%
790
July1st to 15thNight
66%
510
17%
1385
8%
510
69%
510
50%
738
July16th to endNight
76%
564
24%
1594
20%
531
78%
531
52%
772
August1st to 15thNight
64%
539
21%
1610
22%
536
66%
536
40%
893
August16th to endNight
59%
573
23%
1770
23%
573
65%
573
36%
1013
September1st to 15thNight
60%
540
25%
1845
24%
540
67%
540
37%
958
September16th to endNight
50%
510
27%
1881
22%
510
60%
510
34%
955
October1st to 15thNight
38%
653
27%
1973
17%
653
47%
653
33%
1141
October16th to endNight
33%
704
22%
2112
11%
704
43%
704
30%
1262
November1st to 15thNight
33%
836
26%
2299
10%
836
45%
836
34%
1350
November16th to endNight
27%
900
20%
2520
9%
900
37%
900
28%
1594
December1st to 15thNight
21%
900
15%
2520
4%
900
31%
900
20%
1770
December16th to endNight
21%
960
17%
2688
6%
960
32%
960
18%
1944

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
12%7%36%5%3445%7%40%
47889
Night
10%6%35%5%2435%7%45%
47151
Cloud CoverDay
12%7%35%5%3445%7%40%
47900
Night
10%6%35%42445%7%45%
47155
Cloud CoverDay
12%7%35%5%2445%7%40%
47898
Night
10%6%35%5%24447%45%
47155
TransparencyDay
42%414%24%12%1
47590
Night
38%314%26%15%2
46968
SeeingDay
14%7%29%30%14%3
6043
Night
14%9%33%30%11%1
16036

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
7%9%47%7%35%35%6%36%
1549
16th to endDay
11%12%5%8%6%3435%7%29%
1728
February1st to 15thDay
12%11%5%8%6%45%346%32%
1575
16th to endDay
12%10%37%6%3435%5%36%
1494
March1st to 15thDay
12%9%5%7%5%2335%6%36%
1969
16th to endDay
18%11%5%7%434445%30%
2112
April1st to 15thDay
16%8%46%5%24346%36%
2103
16th to endDay
25%8%35%434346%30%
2315
May1st to 15thDay
17%7%35%5%345%46%34%
2331
16th to endDay
15%6%25%5%35%5%5%7%36%
2586
June1st to 15thDay
13%6%25%5%345%5%8%39%
2520
16th to endDay
6%3245%36%5%6%9%48%
2520
July1st to 15thDay
7%425%4235%6%9%48%
2490
16th to endDay
6%314326%46%10%50%
2466
August1st to 15thDay
8%6%24436%5%6%8%43%
2340
16th to endDay
11%5%25%42446%7%45%
2431
September1st to 15thDay
11%415%42445%7%49%
2112
16th to endDay
10%314323347%55%
1866
October1st to 15thDay
13%5%35%313326%51%
1650
16th to endDay
14%7%34423346%43%
1760
November1st to 15thDay
9%5%24424347%50%
1556
16th to endDay
12%9%35%5%2335%6%41%
1440
December1st to 15thDay
13%10%410%6%34336%31%
1440
16th to endDay
14%12%5%11%6%3445%6%24%
1536
January1st to 15thNight
7%7%46%7%3445%7%40%
2386
16th to endNight
9%11%47%6%35%45%6%36%
2496
February1st to 15thNight
13%9%48%7%34445%33%
2285
16th to endNight
8%7%35%5%3435%6%44%
1991
March1st to 15thNight
12%7%34424347%45%
1968
16th to endNight
14%10%46%42446%8%33%
2112
April1st to 15thNight
13%8%24423448%42%
1845
16th to endNight
17%9%35%5%34446%36%
1644
May1st to 15thNight
14%4245%2235%7%44%
1620
16th to endNight
11%5%26%42435%8%44%
1527
June1st to 15thNight
7%436%425%46%7%46%
1440
16th to endNight
32133245%6%8%58%
1440
July1st to 15thNight
311332445%9%59%
1467
16th to endNight
321231436%10%59%
1702
August1st to 15thNight
5%32442345%9%52%
1620
16th to endNight
8%4245%2345%6%53%
1770
September1st to 15thNight
9%41341435%6%56%
1845
16th to endNight
9%423323347%54%
1881
October1st to 15thNight
13%5%24312336%52%
1973
16th to endNight
15%7%24312225%51%
2112
November1st to 15thNight
8%424414346%53%
2299
16th to endNight
10%7%36%32435%6%45%
2520
December1st to 15thNight
12%11%37%6%24445%35%
2520
16th to endNight
14%10%5%9%6%33346%31%
2688

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
7%10%5%7%7%4445%6%36%
1549
16th to endDay
11%12%5%8%6%3345%7%29%
1728
February1st to 15thDay
11%11%6%8%6%45%345%32%
1575
16th to endDay
12%10%47%7%24446%35%
1494
March1st to 15thDay
12%9%6%7%5%2335%6%37%
1980
16th to endDay
17%12%5%6%5%25%445%30%
2112
April1st to 15thDay
16%8%46%5%33446%36%
2103
16th to endDay
25%8%35%435%346%30%
2315
May1st to 15thDay
17%8%35%5%35%5%47%34%
2331
16th to endDay
16%5%26%5%35%5%5%7%36%
2586
June1st to 15thDay
13%5%25%5%34448%39%
2520
16th to endDay
6%314435%5%7%8%48%
2520
July1st to 15thDay
7%4244245%6%9%48%
2490
16th to endDay
5%323435%46%10%50%
2466
August1st to 15thDay
8%5%345%35%5%6%9%42%
2340
16th to endDay
11%5%2442346%7%45%
2431
September1st to 15thDay
11%4144245%47%50%
2112
16th to endDay
11%213323347%55%
1866
October1st to 15thDay
14%5%25%313326%51%
1650
16th to endDay
14%8%24414346%43%
1760
November1st to 15thDay
9%425%424447%50%
1556
16th to endDay
12%9%36%5%23346%41%
1440
December1st to 15thDay
13%10%410%6%34436%31%
1440
16th to endDay
14%12%5%11%6%3445%6%24%
1536
January1st to 15thNight
7%7%37%7%3445%7%40%
2386
16th to endNight
9%11%5%7%5%3445%6%36%
2496
February1st to 15thNight
13%9%48%7%34345%34%
2278
16th to endNight
8%8%35%5%3445%5%44%
1991
March1st to 15thNight
12%7%24324347%45%
1980
16th to endNight
14%10%46%5%3445%7%33%
2112
April1st to 15thNight
14%7%24423447%42%
1845
16th to endNight
17%8%35%5%34446%36%
1644
May1st to 15thNight
14%5%3432336%8%44%
1619
16th to endNight
11%6%15%43445%8%44%
1527
June1st to 15thNight
7%426%5%2446%8%46%
1440
16th to endNight
321342446%8%58%
1440
July1st to 15thNight
321323445%9%59%
1467
16th to endNight
321232436%9%60%
1702
August1st to 15thNight
5%32442435%8%53%
1620
16th to endNight
8%4245%2245%6%53%
1770
September1st to 15thNight
9%313323446%56%
1845
16th to endNight
9%423323346%55%
1881
October1st to 15thNight
14%424312236%52%
1973
16th to endNight
15%6%25%312225%51%
2112
November1st to 15thNight
8%424423346%53%
2299
16th to endNight
10%7%36%424346%45%
2520
December1st to 15thNight
12%11%38%5%24446%35%
2520
16th to endNight
14%10%5%9%6%24346%31%
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
7%10%47%8%4445%6%36%
1549
16th to endDay
11%12%5%8%6%2445%7%29%
1728
February1st to 15thDay
12%11%5%8%6%45%346%32%
1575
16th to endDay
12%9%47%6%3445%5%36%
1494
March1st to 15thDay
12%9%5%7%5%2335%6%36%
1980
16th to endDay
18%11%5%7%425%35%5%30%
2110
April1st to 15thDay
16%8%36%5%23446%36%
2103
16th to endDay
25%8%345%34346%30%
2315
May1st to 15thDay
17%7%35%435%5%47%34%
2331
16th to endDay
16%5%26%5%25%5%47%36%
2586
June1st to 15thDay
14%5%26%5%345%48%39%
2520
16th to endDay
6%3145%35%5%7%8%48%
2520
July1st to 15thDay
7%4244245%6%9%48%
2490
16th to endDay
6%324435%46%9%50%
2466
August1st to 15thDay
8%6%145%25%6%6%9%43%
2340
16th to endDay
11%5%2442345%7%46%
2431
September1st to 15thDay
11%414424447%49%
2112
16th to endDay
11%213323447%55%
1866
October1st to 15thDay
13%5%25%323325%51%
1650
16th to endDay
14%8%25%424346%43%
1760
November1st to 15thDay
9%425%424437%50%
1556
16th to endDay
12%9%36%5%2335%6%41%
1440
December1st to 15thDay
14%10%410%6%34435%32%
1440
16th to endDay
14%12%5%11%7%35%45%6%25%
1536
January1st to 15thNight
8%7%36%7%3445%7%40%
2386
16th to endNight
10%10%46%6%24446%36%
2496
February1st to 15thNight
13%9%49%7%34445%34%
2278
16th to endNight
8%7%36%6%3445%6%44%
1991
March1st to 15thNight
12%7%3442335%7%45%
1980
16th to endNight
14%10%46%42445%7%33%
2112
April1st to 15thNight
14%7%245%23448%42%
1845
16th to endNight
18%8%25%5%3435%6%36%
1644
May1st to 15thNight
14%425%41336%7%44%
1619
16th to endNight
11%5%25%4345%48%44%
1527
June1st to 15thNight
7%5%26%5%245%6%8%45%
1440
16th to endNight
321342446%8%57%
1440
July1st to 15thNight
3213334449%59%
1467
16th to endNight
311232436%9%60%
1702
August1st to 15thNight
6%3245%1445%9%53%
1620
16th to endNight
8%4245%2245%6%53%
1770
September1st to 15thNight
9%31341335%6%56%
1845
16th to endNight
9%5%13423346%55%
1881
October1st to 15thNight
14%424422336%52%
1973
16th to endNight
15%6%25%31232451%
2112
November1st to 15thNight
8%424424346%53%
2299
16th to endNight
11%7%36%424346%46%
2520
December1st to 15thNight
12%11%38%6%24446%35%
2520
16th to endNight
14%10%5%9%6%34346%31%
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
46%416%20%11%
1550
16th to endDay
53%315%19%7%
1728
February1st to 15thDay
53%313%21%7%
1576
16th to endDay
49%312%20%11%2
1494
March1st to 15thDay
47%414%22%10%1
1980
16th to endDay
55%5%13%18%6%1
2112
April1st to 15thDay
47%412%25%8%1
2103
16th to endDay
54%311%19%9%
2315
May1st to 15thDay
48%413%23%9%
2331
16th to endDay
46%5%13%22%11%1
2590
June1st to 15thDay
41%5%15%23%13%1
2520
16th to endDay
31%5%16%30%13%2
2520
July1st to 15thDay
31%5%16%29%12%4
2343
16th to endDay
29%5%17%28%17%2
2311
August1st to 15thDay
35%5%16%26%14%1
2326
16th to endDay
35%411%28%15%3
2431
September1st to 15thDay
33%313%30%17%1
2112
16th to endDay
29%413%31%19%
1866
October1st to 15thDay
36%29%29%19%1
1650
16th to endDay
42%212%26%15%1
1760
November1st to 15thDay
33%313%25%21%1
1556
16th to endDay
44%215%25%11%
1440
December1st to 15thDay
54%314%18%6%1
1440
16th to endDay
59%314%15%6%1
1536
January1st to 15thNight
43%215%22%14%
2386
16th to endNight
47%415%22%10%
2496
February1st to 15thNight
52%313%21%7%1
2288
16th to endNight
41%312%24%15%2
1991
March1st to 15thNight
39%313%28%13%2
1980
16th to endNight
49%5%13%22%7%1
2112
April1st to 15thNight
41%311%27%14%1
1845
16th to endNight
47%413%20%12%1
1644
May1st to 15thNight
38%413%26%15%1
1620
16th to endNight
38%5%17%23%13%2
1529
June1st to 15thNight
34%5%15%27%15%2
1440
16th to endNight
22%415%30%22%4
1440
July1st to 15thNight
21%420%32%15%4
1385
16th to endNight
18%416%36%20%3
1594
August1st to 15thNight
28%415%30%18%2
1610
16th to endNight
31%412%24%19%7%
1770
September1st to 15thNight
28%311%30%21%3
1845
16th to endNight
29%311%33%19%2
1881
October1st to 15thNight
34%310%26%22%3
1973
16th to endNight
37%213%26%18%1
2112
November1st to 15thNight
31%314%25%21%3
2299
16th to endNight
39%315%27%13%1
2520
December1st to 15thNight
49%314%23%8%
2520
16th to endNight
53%312%19%9%1
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
13%14%46%22%3
90
16th to endDay
26%8%41%18%32
96
February1st to 15thDay
15%17%37%24%4
90
16th to endDay
24%7%34%19%13%
81
March1st to 15thDay
18%17%38%21%3
90
16th to endDay
35%14%28%19%2
96
April1st to 15thDay
17%13%37%26%4
222
16th to endDay
31%10%28%18%9%1
425
May1st to 15thDay
20%12%28%27%9%1
468
16th to endDay
17%7%35%25%12%2
517
June1st to 15thDay
13%430%30%19%2
495
16th to endDay
5%7%36%32%15%3
495
July1st to 15thDay
5%130%35%20%7%
475
16th to endDay
5%121%44%22%4
515
August1st to 15thDay
9%319%37%26%4
493
16th to endDay
15%318%34%21%6%
471
September1st to 15thDay
7%228%36%17%5%
267
16th to endDay
8%7%30%31%20%1
105
October1st to 15thDay
10%5%34%33%11%5%
90
16th to endDay
15%6%40%31%6%
96
November1st to 15thDay
5%7%35%36%10%4
90
16th to endDay
33%14%35%13%3
90
December1st to 15thDay
18%20%37%18%31
90
16th to endDay
32%26%36%41
96
January1st to 15thNight
11%14%41%24%6%
900
16th to endNight
16%14%39%24%5%
960
February1st to 15thNight
17%10%41%25%5%
880
16th to endNight
12%12%43%22%7%1
729
March1st to 15thNight
16%10%33%28%10%1
540
16th to endNight
20%11%35%23%8%1
576
April1st to 15thNight
19%12%34%28%5%
539
16th to endNight
22%9%33%24%9%
540
May1st to 15thNight
17%8%31%32%9%
540
16th to endNight
13%5%31%36%12%
563
June1st to 15thNight
10%327%44%13%
540
16th to endNight
5%332%43%14%
540
July1st to 15thNight
4122%43%26%1
510
16th to endNight
3113%52%28%1
564
August1st to 15thNight
7%217%46%24%1
539
16th to endNight
10%318%38%23%5%
573
September1st to 15thNight
11%320%36%24%4
540
16th to endNight
12%5%27%33%18%2
510
October1st to 15thNight
15%7%33%29%11%2
653
16th to endNight
18%8%33%27%10%
704
November1st to 15thNight
11%14%37%26%10%
836
16th to endNight
15%14%39%22%7%
900
December1st to 15thNight
17%13%38%25%5%
900
16th to endNight
19%11%36%25%6%
960
Page generated at 2017-09-22 06:35:31. Version ac04

Copyright 2017 A. Danko


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