Greenwood
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Greenwood clear sky chart from 2005-11-05 to 2018-02-13.

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
31%
16801
21%
48793
8%
16757
42%
16757
28%
28478

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
22%
975
20%
2716
6%
970
34%
970
23%
1613
January16th to endNight
17%
1040
21%
2912
4%
1040
33%
1040
19%
1721
February1st to 15thNight
20%
764
17%
2435
6%
763
32%
763
18%
1489
February16th to endNight
24%
632
19%
1894
7%
632
35%
632
23%
1139
March1st to 15thNight
26%
720
19%
2160
6%
720
38%
720
26%
1262
March16th to endNight
27%
633
16%
2007
7%
633
38%
633
23%
1243
April1st to 15thNight
25%
539
17%
1798
8%
539
39%
539
22%
1115
April16th to endNight
29%
540
16%
1715
9%
540
40%
540
20%
1103
May1st to 15thNight
35%
540
17%
1512
9%
540
42%
540
29%
924
May16th to endNight
29%
563
15%
1498
5%
561
35%
561
26%
1002
June1st to 15thNight
35%
540
11%
1440
4%
540
39%
540
28%
932
June16th to endNight
39%
540
16%
1440
5%
540
45%
540
41%
810
July1st to 15thNight
54%
510
17%
1360
9%
510
58%
510
45%
753
July16th to endNight
58%
564
23%
1416
15%
531
61%
531
50%
762
August1st to 15thNight
55%
539
24%
1481
14%
536
63%
536
43%
826
August16th to endNight
58%
573
28%
1910
24%
573
70%
573
44%
902
September1st to 15thNight
51%
540
25%
1800
16%
540
67%
540
37%
927
September16th to endNight
46%
537
30%
1967
23%
537
59%
537
37%
938
October1st to 15thNight
30%
666
24%
2106
12%
666
42%
666
26%
1229
October16th to endNight
31%
906
27%
2442
9%
906
43%
906
30%
1437
November1st to 15thNight
26%
950
25%
2470
7%
950
38%
950
31%
1460
November16th to endNight
21%
975
27%
2672
6%
975
39%
975
30%
1523
December1st to 15thNight
19%
975
19%
2730
5%
975
32%
975
23%
1616
December16th to endNight
24%
1040
22%
2912
4%
1040
40%
1040
22%
1752

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
7%5%244245%6%8%48%
49257
Night
5%42442445%8%52%
48960
Cloud CoverDay
7%5%244245%5%8%49%
49267
Night
5%42442445%8%52%
48963
Cloud CoverDay
7%5%2442446%8%49%
49267
Night
6%42442445%8%52%
48965
Cloud CoverDay
6%5%244245%6%8%49%
49265
Night
5%4144245%6%8%51%
48965
TransparencyDay
31%7%17%25%13%3
48941
Night
28%7%17%26%15%3
48793
SeeingDay
14%18%34%21%8%1
6515
Night
12%20%32%25%8%
16805

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
1335%43446%9%53%
1552
16th to endDay
1325%4245%6%8%53%
1664
February1st to 15thDay
38%37%5%35%5%6%7%42%
1704
16th to endDay
17%48%5%25%5%6%9%43%
1580
March1st to 15thDay
25%35%4245%6%9%49%
1790
16th to endDay
8%8%36%5%2445%8%41%
2214
April1st to 15thDay
10%8%35%42445%9%39%
2150
16th to endDay
17%10%345%345%6%6%33%
2244
May1st to 15thDay
11%7%35%5%35%46%7%39%
2437
16th to endDay
17%6%25%5%25%46%9%32%
2616
June1st to 15thDay
11%5%245%25%5%7%8%41%
2520
16th to endDay
42123145%6%9%59%
2520
July1st to 15thDay
5%313415%5%6%9%52%
2520
16th to endDay
42133245%7%8%56%
2656
August1st to 15thDay
4314335%6%7%10%48%
2468
16th to endDay
6%2133145%5%6%59%
2292
September1st to 15thDay
9%414213345%58%
2160
16th to endDay
7%412212436%62%
1992
October1st to 15thDay
10%6%24423345%51%
1851
16th to endDay
5%5%2331335%8%55%
1770
November1st to 15thDay
342441445%9%55%
1718
16th to endDay
24243245%6%9%53%
1615
December1st to 15thDay
1435%426%5%6%10%49%
1560
16th to endDay
35%35%6%3446%9%46%
1664
January1st to 15thNight
12146%35%5%6%9%52%
2716
16th to endNight
24244346%6%9%53%
2912
February1st to 15thNight
26%36%435%5%5%8%47%
2432
16th to endNight
25%25%6%345%6%8%48%
1894
March1st to 15thNight
4425%5%2446%8%50%
2147
16th to endNight
8%7%35%43446%10%42%
2007
April1st to 15thNight
10%6%235%35%45%8%44%
1798
16th to endNight
15%7%24423447%42%
1715
May1st to 15thNight
9%6%14323348%51%
1512
16th to endNight
15%6%33323449%43%
1497
June1st to 15thNight
10%6%234245%5%9%45%
1440
16th to endNight
5%21342435%8%58%
1440
July1st to 15thNight
42132245%6%9%58%
1440
16th to endNight
21124136%6%9%59%
1512
August1st to 15thNight
32134235%6%8%57%
1489
16th to endNight
4212313447%64%
1910
September1st to 15thNight
7%4232345%7%58%
1800
16th to endNight
8%212313347%61%
1967
October1st to 15thNight
11%6%24312346%51%
2106
16th to endNight
6%5%2332445%8%54%
2442
November1st to 15thNight
431442445%8%53%
2470
16th to endNight
3324425%45%8%55%
2672
December1st to 15thNight
24244246%6%9%51%
2730
16th to endNight
25%244245%6%8%51%
2912

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
1335%43436%8%54%
1553
16th to endDay
2425%5%2446%8%53%
1664
February1st to 15thDay
28%38%5%35%5%6%7%42%
1704
16th to endDay
27%38%4345%6%9%44%
1580
March1st to 15thDay
25%35%4245%6%9%49%
1800
16th to endDay
8%9%36%5%245%5%8%41%
2213
April1st to 15thDay
11%8%35%33446%8%39%
2150
16th to endDay
17%11%345%3446%6%33%
2244
May1st to 15thDay
11%7%35%5%35%5%5%7%40%
2437
16th to endDay
18%7%245%25%46%9%33%
2616
June1st to 15thDay
12%5%235%35%6%6%9%41%
2520
16th to endDay
421232345%10%59%
2520
July1st to 15thDay
5%313325%6%6%9%53%
2520
16th to endDay
5%2123245%6%8%57%
2656
August1st to 15thDay
5%314335%5%7%10%48%
2468
16th to endDay
6%21332445%6%60%
2292
September1st to 15thDay
9%413313336%58%
2160
16th to endDay
7%412212436%63%
1992
October1st to 15thDay
10%7%24423445%51%
1851
16th to endDay
5%5%2332345%7%56%
1770
November1st to 15thDay
342441446%8%55%
1718
16th to endDay
34233246%7%9%53%
1615
December1st to 15thDay
1425%435%6%6%10%49%
1560
16th to endDay
36%35%6%3446%8%47%
1664
January1st to 15thNight
13146%345%7%9%52%
2716
16th to endNight
24144245%6%8%54%
2912
February1st to 15thNight
26%36%435%5%5%8%47%
2425
16th to endNight
26%25%6%345%6%8%48%
1894
March1st to 15thNight
4425%5%25%46%8%51%
2160
16th to endNight
8%7%35%43446%9%42%
2004
April1st to 15thNight
10%6%235%25%46%7%45%
1798
16th to endNight
15%7%23424446%42%
1715
May1st to 15thNight
9%6%13423348%51%
1511
16th to endNight
16%6%32313449%43%
1498
June1st to 15thNight
11%5%134245%6%8%45%
1440
16th to endNight
5%21342345%8%58%
1440
July1st to 15thNight
42132245%6%8%58%
1440
16th to endNight
22124236%6%9%60%
1512
August1st to 15thNight
32134235%6%8%58%
1489
16th to endNight
4212213447%64%
1910
September1st to 15thNight
7%31242345%6%58%
1800
16th to endNight
8%312313346%61%
1967
October1st to 15thNight
11%7%24313346%50%
2106
16th to endNight
6%5%1332435%8%54%
2442
November1st to 15thNight
441442445%8%54%
2470
16th to endNight
3324425%448%56%
2672
December1st to 15thNight
24244236%7%8%52%
2730
16th to endNight
25%244245%6%8%52%
2912

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
2335%425%36%8%53%
1552
16th to endDay
2325%42446%8%53%
1664
February1st to 15thDay
38%47%5%35%5%7%7%41%
1704
16th to endDay
27%48%5%25%6%6%9%44%
1580
March1st to 15thDay
25%35%4345%6%9%49%
1800
16th to endDay
8%9%46%42445%8%41%
2214
April1st to 15thDay
11%8%45%32445%8%39%
2150
16th to endDay
17%11%25%5%2446%6%33%
2244
May1st to 15thDay
11%7%35%5%25%5%5%7%40%
2437
16th to endDay
18%7%245%35%47%9%33%
2616
June1st to 15thDay
12%5%235%35%5%6%9%41%
2520
16th to endDay
42232445%9%59%
2520
July1st to 15thDay
5%313325%5%6%9%54%
2520
16th to endDay
5%2123245%6%8%57%
2656
August1st to 15thDay
5%314425%5%8%9%48%
2468
16th to endDay
6%21322445%6%60%
2292
September1st to 15thDay
9%413323346%58%
2160
16th to endDay
7%322213435%62%
1992
October1st to 15thDay
10%7%23423345%51%
1851
16th to endDay
6%5%2332335%8%55%
1770
November1st to 15thDay
342441445%8%55%
1718
16th to endDay
25%143245%6%9%53%
1615
December1st to 15thDay
1425%436%5%7%9%49%
1560
16th to endDay
46%35%6%3446%8%47%
1664
January1st to 15thNight
12145%35%5%7%9%52%
2716
16th to endNight
2424425%5%6%9%53%
2912
February1st to 15thNight
26%36%435%5%5%8%47%
2425
16th to endNight
36%25%5%35%46%8%48%
1894
March1st to 15thNight
4425%5%3446%8%50%
2160
16th to endNight
8%7%3442446%9%42%
2007
April1st to 15thNight
10%5%245%35%46%7%44%
1798
16th to endNight
16%7%24425%346%42%
1715
May1st to 15thNight
9%6%13423248%51%
1511
16th to endNight
16%6%23323448%44%
1497
June1st to 15thNight
12%5%13325%46%9%45%
1440
16th to endNight
5%3242345%7%58%
1440
July1st to 15thNight
5%2132245%5%9%58%
1440
16th to endNight
21133235%6%9%60%
1512
August1st to 15thNight
321342346%8%57%
1489
16th to endNight
5%2222345%6%64%
1910
September1st to 15thNight
7%312323446%58%
1800
16th to endNight
8%212323336%61%
1967
October1st to 15thNight
11%7%14322346%51%
2106
16th to endNight
6%5%1332445%8%54%
2442
November1st to 15thNight
432442445%8%54%
2470
16th to endNight
3323425%45%9%55%
2672
December1st to 15thNight
24244245%7%8%52%
2730
16th to endNight
35%244245%6%8%52%
2912

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
2325%5%35%35%10%53%
1552
16th to endDay
23244346%6%9%51%
1664
February1st to 15thDay
38%37%5%445%7%8%41%
1704
16th to endDay
16%37%5%25%5%7%8%44%
1580
March1st to 15thDay
25%345%25%5%6%9%49%
1800
16th to endDay
8%8%36%43445%9%41%
2212
April1st to 15thDay
10%8%344245%5%9%40%
2150
16th to endDay
16%8%35%5%35%5%6%7%33%
2244
May1st to 15thDay
10%6%36%4345%5%8%40%
2437
16th to endDay
16%7%25%4345%6%9%34%
2616
June1st to 15thDay
11%414435%5%7%8%42%
2520
16th to endDay
42222446%8%60%
2520
July1st to 15thDay
4213425%5%5%9%54%
2520
16th to endDay
42123235%8%8%57%
2656
August1st to 15thDay
43144347%7%9%49%
2468
16th to endDay
5%21332345%6%61%
2292
September1st to 15thDay
8%313323346%59%
2160
16th to endDay
8%412112346%62%
1992
October1st to 15thDay
10%6%2442335%5%52%
1851
16th to endDay
5%5%1332335%8%55%
1770
November1st to 15thDay
35%1432346%8%55%
1718
16th to endDay
2424425%46%9%52%
1615
December1st to 15thDay
1324436%5%7%9%50%
1560
16th to endDay
46%25%5%35%5%5%8%47%
1664
January1st to 15thNight
12146%25%6%7%10%50%
2716
16th to endNight
2424435%5%6%9%51%
2912
February1st to 15thNight
36%36%425%46%9%47%
2425
16th to endNight
36%25%6%345%6%8%46%
1894
March1st to 15thNight
4415%5%345%6%9%48%
2160
16th to endNight
9%7%2343346%9%43%
2007
April1st to 15thNight
9%6%345%35%5%5%7%44%
1798
16th to endNight
15%7%1442445%6%43%
1715
May1st to 15thNight
8%5%14423348%52%
1511
16th to endNight
16%42342345%8%43%
1497
June1st to 15thNight
11%5%2342447%9%44%
1440
16th to endNight
42133235%5%8%57%
1440
July1st to 15thNight
31133245%5%8%59%
1440
16th to endNight
21242447%9%60%
1512
August1st to 15thNight
321332447%9%55%
1489
16th to endNight
4213213446%64%
1910
September1st to 15thNight
6%31332345%6%59%
1800
16th to endNight
8%312313346%62%
1967
October1st to 15thNight
10%6%24323347%50%
2106
16th to endNight
6%41342345%8%54%
2442
November1st to 15thNight
441442446%7%54%
2470
16th to endNight
33234345%5%8%54%
2672
December1st to 15thNight
2425%4246%7%10%49%
2730
16th to endNight
35%144235%7%8%50%
2912

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
27%8%25%25%8%4
1553
16th to endDay
26%9%24%25%11%2
1664
February1st to 15thDay
40%8%18%21%8%2
1705
16th to endDay
34%9%20%20%10%4
1580
March1st to 15thDay
29%8%21%27%12%1
1800
16th to endDay
41%7%15%27%7%
2214
April1st to 15thDay
40%7%20%23%6%1
2150
16th to endDay
50%6%15%19%7%
2244
May1st to 15thDay
41%6%18%25%7%
2437
16th to endDay
46%9%19%18%5%1
2620
June1st to 15thDay
37%9%16%24%9%1
2520
16th to endDay
19%7%17%32%16%5%
2520
July1st to 15thDay
26%7%14%25%18%6%
2371
16th to endDay
22%6%14%26%21%10%
2489
August1st to 15thDay
26%9%16%25%14%6%
2452
16th to endDay
23%411%29%21%9%
2292
September1st to 15thDay
27%313%25%22%7%
2160
16th to endDay
24%410%35%22%2
1992
October1st to 15thDay
34%5%13%24%18%3
1851
16th to endDay
26%5%20%26%16%5%
1770
November1st to 15thDay
25%7%17%25%19%4
1718
16th to endDay
24%8%18%31%14%1
1615
December1st to 15thDay
28%10%23%22%15%
1560
16th to endDay
34%8%17%23%13%2
1664
January1st to 15thNight
25%11%23%24%10%4
2716
16th to endNight
25%10%21%24%14%2
2912
February1st to 15thNight
33%8%21%23%10%2
2435
16th to endNight
31%8%18%24%12%4
1894
March1st to 15thNight
29%7%19%26%13%3
2160
16th to endNight
36%6%20%25%10%
2007
April1st to 15thNight
37%7%17%25%10%1
1798
16th to endNight
41%6%16%23%11%
1715
May1st to 15thNight
32%7%19%28%12%
1512
16th to endNight
38%8%18%25%9%
1498
June1st to 15thNight
35%8%21%24%9%
1440
16th to endNight
23%6%18%28%18%3
1440
July1st to 15thNight
22%6%15%29%20%5%
1360
16th to endNight
18%7%14%29%24%6%
1416
August1st to 15thNight
21%8%14%28%18%7%
1481
16th to endNight
19%5%10%30%26%8%
1910
September1st to 15thNight
25%5%11%26%24%8%
1800
16th to endNight
23%411%32%22%5%
1967
October1st to 15thNight
33%5%13%24%18%4
2106
16th to endNight
27%6%17%23%18%5%
2442
November1st to 15thNight
27%6%18%23%19%4
2470
16th to endNight
25%6%18%28%16%3
2672
December1st to 15thNight
26%10%21%26%12%2
2730
16th to endNight
28%9%18%26%14%2
2912

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
10%22%33%20%9%2
135
16th to endDay
18%25%28%15%8%3
144
February1st to 15thDay
19%30%41%7%1
126
16th to endDay
22%37%20%13%41
81
March1st to 15thDay
12%33%40%6%5%2
90
16th to endDay
21%23%36%12%5%
255
April1st to 15thDay
21%31%39%6%
269
16th to endDay
30%20%27%13%5%
354
May1st to 15thDay
22%22%26%17%9%2
468
16th to endDay
23%18%30%16%6%2
517
June1st to 15thDay
15%17%32%24%9%1
495
16th to endDay
7%19%40%23%7%1
495
July1st to 15thDay
6%11%36%30%12%2
475
16th to endDay
410%38%28%15%1
515
August1st to 15thDay
6%9%40%30%11%2
474
16th to endDay
7%12%36%30%8%4
332
September1st to 15thDay
12%15%34%26%8%2
315
16th to endDay
18%18%32%17%11%1
147
October1st to 15thDay
20%25%33%11%5%3
135
16th to endDay
17%18%37%16%5%4
144
November1st to 15thDay
5%20%35%24%9%4
135
16th to endDay
20%25%35%14%3
135
December1st to 15thDay
21%29%30%16%2
135
16th to endDay
18%22%40%15%2
144
January1st to 15thNight
14%28%31%18%6%
975
16th to endNight
14%31%33%14%41
1040
February1st to 15thNight
13%29%32%17%6%
768
16th to endNight
11%26%33%19%8%1
632
March1st to 15thNight
10%21%37%23%5%1
720
16th to endNight
14%17%36%24%7%
633
April1st to 15thNight
16%17%38%23%3
539
16th to endNight
22%18%25%24%7%1
540
May1st to 15thNight
14%16%29%26%11%
540
16th to endNight
20%14%33%21%9%
563
June1st to 15thNight
15%14%33%27%8%
540
16th to endNight
5%12%40%33%7%
540
July1st to 15thNight
5%6%30%40%16%1
510
16th to endNight
3431%45%14%
564
August1st to 15thNight
5%6%29%42%15%
539
16th to endNight
6%7%23%40%19%1
573
September1st to 15thNight
9%9%27%36%15%1
540
16th to endNight
12%11%28%32%12%2
537
October1st to 15thNight
18%16%31%23%8%1
666
16th to endNight
15%19%30%24%8%1
906
November1st to 15thNight
11%25%35%19%6%2
950
16th to endNight
10%26%38%19%3
975
December1st to 15thNight
13%28%34%17%4
975
16th to endNight
13%28%31%21%5%
1040
Page generated at 2018-02-13 18:46:10. Version ac04

Copyright 2018 A. Danko


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