Greeley
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Greeley clear sky chart from 2005-11-05 to 2018-03-21.

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
59%
16778
26%
49226
20%
16739
64%
16739
39%
27807

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
56%
972
28%
2716
21%
970
62%
970
42%
1523
January16th to endNight
55%
913
31%
2785
24%
913
63%
913
41%
1518
February1st to 15thNight
48%
759
22%
2435
16%
758
57%
758
33%
1411
February16th to endNight
47%
684
28%
2050
17%
684
57%
684
35%
1182
March1st to 15thNight
55%
780
27%
2314
17%
780
63%
780
42%
1266
March16th to endNight
48%
690
23%
2076
15%
690
56%
690
35%
1226
April1st to 15thNight
44%
539
21%
1798
15%
539
54%
539
30%
1033
April16th to endNight
43%
540
19%
1800
17%
540
50%
540
26%
1092
May1st to 15thNight
51%
540
18%
1577
15%
540
55%
540
27%
1023
May16th to endNight
55%
561
17%
1498
13%
561
58%
561
32%
952
June1st to 15thNight
63%
540
18%
1440
13%
540
66%
540
43%
837
June16th to endNight
74%
540
26%
1440
21%
540
75%
540
53%
756
July1st to 15thNight
70%
510
17%
1360
15%
510
70%
510
38%
835
July16th to endNight
78%
564
26%
1416
22%
531
78%
531
43%
801
August1st to 15thNight
74%
539
19%
1660
19%
536
74%
536
37%
924
August16th to endNight
75%
573
27%
1910
30%
573
77%
573
38%
1007
September1st to 15thNight
66%
540
26%
1800
27%
540
71%
540
37%
960
September16th to endNight
72%
537
34%
1943
34%
537
77%
537
45%
882
October1st to 15thNight
59%
693
27%
2133
21%
693
63%
693
38%
1185
October16th to endNight
64%
824
35%
2360
24%
824
70%
824
47%
1240
November1st to 15thNight
62%
950
30%
2470
18%
950
67%
950
49%
1371
November16th to endNight
60%
975
34%
2603
22%
975
67%
975
49%
1428
December1st to 15thNight
56%
975
23%
2730
16%
975
61%
975
40%
1588
December16th to endNight
53%
1040
26%
2912
17%
1040
60%
1040
35%
1767

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
5%42332445%8%52%
49642
Night
6%5%2442345%7%55%
49398
Cloud CoverDay
6%42432445%8%52%
49640
Night
6%5%2442345%7%54%
49398
TransparencyDay
27%6%12%25%20%7%
49316
Night
28%5%12%25%20%6%
49226
SeeingDay
9%5%21%33%23%7%
6462
Night
8%222%47%17%1
16788

By Month

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
38%24323348%55%
1552
16th to endDay
25%25%32445%7%55%
1804
February1st to 15thDay
37%45%42445%8%48%
1757
16th to endDay
26%3432445%6%55%
1710
March1st to 15thDay
34235%25%35%7%56%
1976
16th to endDay
7%5%25%32446%8%48%
2275
April1st to 15thDay
9%5%2432336%7%50%
2150
16th to endDay
13%6%2442445%8%43%
2160
May1st to 15thDay
12%6%24425%5%6%9%41%
2369
16th to endDay
9%5%24435%5%6%9%43%
2616
June1st to 15thDay
6%4133345%6%10%50%
2520
16th to endDay
322315%6%7%9%57%
2520
July1st to 15thDay
6%313335%5%6%9%49%
2520
16th to endDay
3213425%6%7%10%50%
2656
August1st to 15thDay
4313436%6%8%10%44%
2289
16th to endDay
42123245%8%8%55%
2292
September1st to 15thDay
7%213314447%58%
2160
16th to endDay
5%312422335%64%
2016
October1st to 15thDay
8%42322335%7%56%
1824
16th to endDay
6%413212337%63%
1851
November1st to 15thDay
26%2433445%7%56%
1718
16th to endDay
342332235%9%59%
1683
December1st to 15thDay
28%2442445%7%53%
1560
16th to endDay
5%6%34433347%51%
1664
January1st to 15thNight
25%35%423346%58%
2716
16th to endNight
36%24422446%57%
2785
February1st to 15thNight
47%36%424347%51%
2425
16th to endNight
49%35%42334455%
2050
March1st to 15thNight
342442335%6%57%
2314
16th to endNight
7%5%34424446%51%
2076
April1st to 15thNight
8%6%245%24447%50%
1798
16th to endNight
15%7%24423336%46%
1800
May1st to 15thNight
14%5%2342445%7%44%
1576
16th to endNight
11%424325%5%5%8%47%
1497
June1st to 15thNight
6%21242445%9%55%
1440
16th to endNight
31233235%8%63%
1440
July1st to 15thNight
7%3245%2346%9%49%
1440
16th to endNight
3214335%5%7%8%55%
1512
August1st to 15thNight
43134346%6%11%49%
1668
16th to endNight
5%312425%5%5%8%55%
1910
September1st to 15thNight
8%31432345%8%53%
1800
16th to endNight
6%2231345%5%64%
1943
October1st to 15thNight
10%413323346%56%
2133
16th to endNight
7%413212336%62%
2360
November1st to 15thNight
432431335%6%60%
2470
16th to endNight
45%23322347%60%
2603
December1st to 15thNight
46%24423447%54%
2730
16th to endNight
5%8%245%2335%8%49%
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
37%25%323338%55%
1552
16th to endDay
26%25%32445%6%55%
1804
February1st to 15thDay
37%46%43346%8%48%
1757
16th to endDay
26%35%32435%6%54%
1710
March1st to 15thDay
3423425%45%6%56%
1976
16th to endDay
7%6%3443446%8%48%
2273
April1st to 15thDay
8%6%25%32445%7%50%
2150
16th to endDay
12%7%2442445%8%43%
2160
May1st to 15thDay
12%5%24425%46%9%41%
2369
16th to endDay
9%424435%5%6%9%43%
2616
June1st to 15thDay
7%31333446%11%50%
2520
16th to endDay
32123246%6%9%58%
2520
July1st to 15thDay
6%314435%5%6%9%49%
2520
16th to endDay
3213435%6%7%10%50%
2656
August1st to 15thDay
5%314436%6%8%11%44%
2289
16th to endDay
4213325%5%6%9%55%
2292
September1st to 15thDay
7%31331435%7%58%
2160
16th to endDay
6%33312346%63%
2016
October1st to 15thDay
8%42331345%7%56%
1824
16th to endDay
6%413212236%63%
1851
November1st to 15thDay
26%2442445%6%56%
1718
16th to endDay
342332236%9%58%
1683
December1st to 15thDay
37%344235%48%52%
1560
16th to endDay
5%6%35%434446%51%
1664
January1st to 15thNight
25%25%423346%58%
2716
16th to endNight
36%24422446%58%
2785
February1st to 15thNight
47%36%424346%51%
2425
16th to endNight
48%35%423345%54%
2050
March1st to 15thNight
3415%32335%7%57%
2314
16th to endNight
8%435%424446%51%
2076
April1st to 15thNight
7%7%235%24447%50%
1798
16th to endNight
14%8%24424246%45%
1800
May1st to 15thNight
14%6%14425%45%8%44%
1576
16th to endNight
10%424335%45%8%46%
1497
June1st to 15thNight
7%21242445%9%55%
1440
16th to endNight
31232345%8%63%
1440
July1st to 15thNight
6%4235%2347%9%49%
1440
16th to endNight
3214325%5%6%9%54%
1512
August1st to 15thNight
42234346%6%10%50%
1668
16th to endNight
5%3134245%5%8%54%
1910
September1st to 15thNight
8%31442345%8%54%
1800
16th to endNight
5%22313445%64%
1943
October1st to 15thNight
10%413323346%56%
2133
16th to endNight
8%413212246%61%
2360
November1st to 15thNight
432431335%7%60%
2470
16th to endNight
4423323347%61%
2603
December1st to 15thNight
46%24423448%53%
2730
16th to endNight
5%8%35%42435%7%49%
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%413%32%18%3
1553
16th to endDay
26%413%30%20%5%
1804
February1st to 15thDay
32%6%15%32%10%3
1758
16th to endDay
28%5%8%31%22%4
1710
March1st to 15thDay
26%412%26%23%6%
1976
16th to endDay
31%5%15%25%16%4
2275
April1st to 15thDay
31%6%12%24%17%7%
2150
16th to endDay
37%7%13%22%16%3
2160
May1st to 15thDay
38%7%12%25%14%2
2369
16th to endDay
34%8%16%21%13%4
2620
June1st to 15thDay
27%7%16%19%20%7%
2520
16th to endDay
19%6%11%22%26%13%
2520
July1st to 15thDay
28%8%11%21%16%13%
2371
16th to endDay
24%8%12%24%20%8%
2489
August1st to 15thDay
28%8%15%19%15%11%
2273
16th to endDay
21%7%11%23%25%9%
2292
September1st to 15thDay
24%49%23%21%16%
2160
16th to endDay
22%46%23%33%8%
2016
October1st to 15thDay
26%5%12%21%26%7%
1824
16th to endDay
22%38%28%26%10%
1851
November1st to 15thDay
25%411%24%23%9%
1718
16th to endDay
21%310%26%29%6%
1683
December1st to 15thDay
28%6%12%33%15%3
1560
16th to endDay
32%5%14%26%16%3
1664
January1st to 15thNight
26%412%30%21%3
2716
16th to endNight
27%49%28%23%5%
2785
February1st to 15thNight
32%5%14%28%14%3
2435
16th to endNight
32%38%27%21%6%
2050
March1st to 15thNight
26%5%10%24%26%6%
2314
16th to endNight
32%5%14%23%20%4
2076
April1st to 15thNight
33%5%11%26%16%6%
1798
16th to endNight
39%412%23%16%3
1800
May1st to 15thNight
38%7%14%21%14%2
1577
16th to endNight
34%8%19%20%11%6%
1498
June1st to 15thNight
25%7%19%25%12%9%
1440
16th to endNight
18%5%12%27%25%9%
1440
July1st to 15thNight
31%6%13%23%16%9%
1360
16th to endNight
23%8%14%26%18%8%
1416
August1st to 15thNight
26%7%18%22%16%8%
1660
16th to endNight
26%6%11%25%21%9%
1910
September1st to 15thNight
27%5%12%20%18%14%
1800
16th to endNight
20%410%27%28%8%
1943
October1st to 15thNight
28%5%13%18%23%10%
2133
16th to endNight
23%39%27%25%10%
2360
November1st to 15thNight
23%410%25%25%10%
2470
16th to endNight
23%39%29%26%7%
2603
December1st to 15thNight
28%5%14%28%17%5%
2730
16th to endNight
33%5%14%29%16%1
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%312%45%21%6%
135
16th to endDay
7%219%45%18%6%
144
February1st to 15thDay
5%6%30%46%10%
135
16th to endDay
7%332%39%13%4
120
March1st to 15thDay
47%21%43%18%4
161
16th to endDay
10%12%40%27%7%1
311
April1st to 15thDay
13%15%34%22%9%4
269
16th to endDay
21%16%31%20%8%2
270
May1st to 15thDay
14%7%23%30%19%4
450
16th to endDay
15%6%18%29%23%6%
517
June1st to 15thDay
7%318%34%26%8%
495
16th to endDay
4219%35%29%8%
495
July1st to 15thDay
10%114%30%31%10%
475
16th to endDay
4111%28%40%12%
515
August1st to 15thDay
6%222%34%25%8%
324
16th to endDay
6%118%33%30%9%
332
September1st to 15thDay
6%322%33%23%10%
315
16th to endDay
9%222%22%29%13%
171
October1st to 15thDay
9%5%12%33%28%11%
135
16th to endDay
6%322%32%21%13%
144
November1st to 15thDay
2214%40%22%18%
135
16th to endDay
9%8%19%43%17%1
135
December1st to 15thDay
7%5%24%46%14%2
135
16th to endDay
2124%61%9%1
144
January1st to 15thNight
5%327%49%12%1
975
16th to endNight
7%227%51%10%
913
February1st to 15thNight
7%330%50%8%
764
16th to endNight
8%333%47%6%
684
March1st to 15thNight
4331%48%11%
780
16th to endNight
8%431%44%10%
690
April1st to 15thNight
11%434%43%5%
539
16th to endNight
18%5%26%36%12%
540
May1st to 15thNight
16%322%41%15%
540
16th to endNight
12%322%38%21%1
563
June1st to 15thNight
7%221%49%18%
540
16th to endNight
416%55%22%
540
July1st to 15thNight
7%11%42%35%1
510
16th to endNight
47%43%42%2
564
August1st to 15thNight
5%11%47%34%1
539
16th to endNight
6%10%44%36%1
573
September1st to 15thNight
9%115%41%27%4
540
16th to endNight
5%115%49%26%1
537
October1st to 15thNight
13%220%41%19%2
693
16th to endNight
10%218%47%19%1
824
November1st to 15thNight
5%221%53%15%1
950
16th to endNight
6%324%52%12%
975
December1st to 15thNight
8%324%54%8%
975
16th to endNight
8%323%53%9%
1040
Page generated at 2018-03-22 09:34:24. Version ac04

Copyright 2018 A. Danko


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