Fort Collins
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Collins 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
56%
15864
26%
46497
18%
15824
64%
15824
40%
25596

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
46%
897
29%
2506
17%
895
57%
895
41%
1341
January16th to endNight
42%
831
32%
2559
18%
831
59%
831
40%
1330
February1st to 15thNight
39%
700
24%
2260
11%
699
55%
699
34%
1234
February16th to endNight
42%
632
30%
1894
17%
632
55%
632
37%
1061
March1st to 15thNight
47%
720
27%
2118
14%
720
59%
720
42%
1149
March16th to endNight
47%
678
24%
2022
15%
678
56%
678
37%
1139
April1st to 15thNight
45%
539
22%
1798
16%
539
56%
539
32%
999
April16th to endNight
42%
540
22%
1800
17%
540
52%
540
27%
1080
May1st to 15thNight
49%
540
19%
1566
14%
540
54%
540
28%
1009
May16th to endNight
60%
562
18%
1498
12%
561
64%
561
35%
928
June1st to 15thNight
66%
540
18%
1440
13%
540
68%
540
42%
838
June16th to endNight
78%
540
27%
1440
21%
540
80%
540
58%
720
July1st to 15thNight
74%
510
19%
1360
17%
510
75%
510
42%
800
July16th to endNight
80%
564
25%
1419
22%
531
80%
531
45%
782
August1st to 15thNight
77%
527
21%
1614
22%
524
78%
524
40%
870
August16th to endNight
78%
525
26%
1750
30%
525
79%
525
41%
894
September1st to 15thNight
67%
495
28%
1650
27%
495
74%
495
38%
881
September16th to endNight
77%
492
36%
1771
37%
492
82%
492
51%
767
October1st to 15thNight
58%
652
27%
1972
20%
652
63%
652
37%
1115
October16th to endNight
58%
745
33%
2153
19%
745
66%
745
45%
1137
November1st to 15thNight
59%
875
31%
2275
18%
875
65%
875
49%
1241
November16th to endNight
55%
900
34%
2424
19%
900
64%
900
50%
1269
December1st to 15thNight
44%
900
24%
2520
11%
900
55%
900
39%
1456
December16th to endNight
48%
960
27%
2688
14%
960
58%
960
37%
1556

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%4244245%6%8%51%
47489
Night
5%42332345%7%57%
46670
Cloud CoverDay
6%4244245%6%8%52%
47487
Night
5%42332345%7%57%
46670
TransparencyDay
28%6%13%25%19%7%
47164
Night
25%5%13%26%21%7%
46497
SeeingDay
9%6%27%32%17%5%
5754
Night
7%5%24%42%17%2
15872

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
15%2441335%9%57%
1432
16th to endDay
15%25%32235%7%61%
1674
February1st to 15thDay
26%2432445%10%53%
1600
16th to endDay
16%2432236%7%57%
1580
March1st to 15thDay
3424424449%54%
1839
16th to endDay
5%6%24325%45%9%49%
2202
April1st to 15thDay
7%5%2333435%9%51%
2150
16th to endDay
12%6%245%245%6%8%40%
2160
May1st to 15thDay
13%6%25%425%6%6%7%39%
2381
16th to endDay
10%5%245%36%6%6%8%39%
2616
June1st to 15thDay
6%313425%6%8%9%47%
2520
16th to endDay
2212335%5%7%9%56%
2520
July1st to 15thDay
6%314436%6%8%8%46%
2520
16th to endDay
3213436%7%8%10%47%
2651
August1st to 15thDay
4425%5%37%6%9%9%41%
2249
16th to endDay
33144346%6%8%52%
2100
September1st to 15thDay
8%3132245%6%7%54%
1980
16th to endDay
4313223446%64%
1859
October1st to 15thDay
6%6%1331345%7%56%
1656
16th to endDay
6%31231235%6%63%
1708
November1st to 15thDay
3413423347%59%
1583
16th to endDay
142432345%9%59%
1533
December1st to 15thDay
26%244245%5%9%52%
1440
16th to endDay
35%3442345%7%54%
1536
January1st to 15thNight
131432345%7%61%
2506
16th to endNight
2424323445%61%
2559
February1st to 15thNight
27%36%323348%55%
2250
16th to endNight
27%35%423246%57%
1894
March1st to 15thNight
25%1442435%7%57%
2118
16th to endNight
6%5%235%1335%8%53%
2022
April1st to 15thNight
6%5%24334448%53%
1798
16th to endNight
14%6%13323347%48%
1800
May1st to 15thNight
15%5%2432445%6%45%
1565
16th to endNight
10%31332445%8%49%
1497
June1st to 15thNight
5%21332345%9%55%
1440
16th to endNight
211221245%9%65%
1440
July1st to 15thNight
6%2223245%7%9%52%
1440
16th to endNight
3213425%5%7%9%55%
1515
August1st to 15thNight
33134145%7%8%54%
1623
16th to endNight
431332445%7%57%
1750
September1st to 15thNight
9%223224346%57%
1650
16th to endNight
411323346%68%
1771
October1st to 15thNight
8%5%1432335%5%57%
1972
16th to endNight
6%5%12213335%63%
2153
November1st to 15thNight
231441245%6%63%
2275
16th to endNight
241321335%6%63%
2424
December1st to 15thNight
36%25%5%23348%56%
2520
16th to endNight
36%35%32345%7%54%
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
26%24322448%57%
1432
16th to endDay
15%1441245%6%61%
1674
February1st to 15thDay
26%3432345%9%53%
1600
16th to endDay
17%25%33335%7%57%
1580
March1st to 15thDay
3425%32435%8%55%
1839
16th to endDay
5%7%2342445%8%50%
2200
April1st to 15thDay
8%42433445%8%51%
2150
16th to endDay
13%6%24435%45%8%40%
2160
May1st to 15thDay
14%6%24335%6%6%8%39%
2381
16th to endDay
11%5%24436%5%7%7%40%
2616
June1st to 15thDay
7%313435%6%7%9%48%
2520
16th to endDay
3212325%5%6%8%58%
2520
July1st to 15thDay
7%313445%6%6%8%47%
2520
16th to endDay
4213436%6%8%8%49%
2651
August1st to 15thDay
5%325%5%35%8%8%9%42%
2249
16th to endDay
5%313425%46%8%53%
2100
September1st to 15thDay
9%31222446%7%55%
1980
16th to endDay
4312323435%65%
1859
October1st to 15thDay
7%6%1332335%7%56%
1656
16th to endDay
6%313212347%63%
1708
November1st to 15thDay
3414423448%59%
1583
16th to endDay
2424323448%60%
1533
December1st to 15thDay
26%25%5%23448%52%
1440
16th to endDay
45%3442345%6%55%
1536
January1st to 15thNight
232332335%7%61%
2506
16th to endNight
25%24313345%61%
2559
February1st to 15thNight
27%36%313347%56%
2250
16th to endNight
38%44413246%56%
1894
March1st to 15thNight
25%2442335%7%57%
2118
16th to endNight
6%5%2442345%7%53%
2022
April1st to 15thNight
6%6%2442345%7%53%
1798
16th to endNight
15%5%24313447%47%
1800
May1st to 15thNight
16%4133245%47%45%
1565
16th to endNight
10%313335%45%8%49%
1497
June1st to 15thNight
7%21332436%9%56%
1440
16th to endNight
3121125%48%66%
1440
July1st to 15thNight
7%21332448%9%52%
1440
16th to endNight
32134145%7%8%56%
1515
August1st to 15thNight
4313425%5%6%9%53%
1623
16th to endNight
5%31332446%7%57%
1750
September1st to 15thNight
9%312314446%57%
1650
16th to endNight
4211224336%68%
1771
October1st to 15thNight
9%413313346%56%
1972
16th to endNight
6%5%12213236%63%
2153
November1st to 15thNight
3414323336%64%
2275
16th to endNight
241331335%6%63%
2424
December1st to 15thNight
36%25%423347%55%
2520
16th to endNight
36%25%42335%7%54%
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
24%413%35%18%3
1433
16th to endDay
23%312%33%20%6%
1674
February1st to 15thDay
27%5%16%34%12%3
1601
16th to endDay
24%412%32%20%4
1580
March1st to 15thDay
27%413%26%21%5%
1839
16th to endDay
31%6%14%25%17%4
2202
April1st to 15thDay
29%6%13%24%17%7%
2150
16th to endDay
39%7%12%22%15%3
2160
May1st to 15thDay
39%8%12%22%14%1
2381
16th to endDay
38%9%15%20%12%3
2620
June1st to 15thDay
28%8%17%20%18%7%
2520
16th to endDay
20%7%11%24%24%12%
2520
July1st to 15thDay
30%9%12%19%15%12%
2371
16th to endDay
26%9%13%24%17%8%
2484
August1st to 15thDay
31%10%12%19%15%10%
2234
16th to endDay
26%7%11%23%22%8%
2100
September1st to 15thDay
26%6%9%22%21%13%
1980
16th to endDay
20%48%25%35%6%
1859
October1st to 15thDay
26%5%12%23%25%6%
1656
16th to endDay
21%410%27%26%9%
1708
November1st to 15thDay
23%413%24%24%10%
1583
16th to endDay
21%5%9%28%28%7%
1533
December1st to 15thDay
27%6%15%32%15%1
1440
16th to endDay
28%5%16%25%18%4
1536
January1st to 15thNight
21%6%14%29%23%4
2506
16th to endNight
24%312%28%25%6%
2559
February1st to 15thNight
28%5%14%32%15%4
2260
16th to endNight
28%49%28%21%6%
1894
March1st to 15thNight
25%411%27%24%5%
2118
16th to endNight
28%5%15%27%20%4
2022
April1st to 15thNight
29%6%13%27%17%6%
1798
16th to endNight
36%6%10%25%17%3
1800
May1st to 15thNight
37%8%13%21%16%2
1566
16th to endNight
30%8%19%22%12%5%
1498
June1st to 15thNight
24%8%18%23%13%10%
1440
16th to endNight
14%6%12%26%25%14%
1440
July1st to 15thNight
25%8%13%25%16%10%
1360
16th to endNight
21%8%14%28%17%9%
1419
August1st to 15thNight
23%8%17%21%19%9%
1614
16th to endNight
24%6%11%25%22%10%
1750
September1st to 15thNight
26%5%12%20%17%16%
1650
16th to endNight
17%39%29%31%8%
1771
October1st to 15thNight
28%5%12%18%26%8%
1972
16th to endNight
24%310%27%25%8%
2153
November1st to 15thNight
21%411%24%26%11%
2275
16th to endNight
19%410%28%27%8%
2424
December1st to 15thNight
27%5%15%29%17%4
2520
16th to endNight
29%5%15%29%18%2
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
5%7%25%35%12%13%
90
16th to endDay
27%42%29%14%4
96
February1st to 15thDay
415%44%30%5%
90
16th to endDay
312%43%28%9%2
81
March1st to 15thDay
7%16%29%34%8%3
129
16th to endDay
10%15%43%25%4
288
April1st to 15thDay
13%18%37%23%5%1
269
16th to endDay
22%17%32%18%6%1
270
May1st to 15thDay
17%8%26%30%12%4
440
16th to endDay
16%5%24%28%18%5%
517
June1st to 15thDay
7%5%23%32%24%6%
495
16th to endDay
3228%32%24%8%
495
July1st to 15thDay
11%117%32%25%12%
475
16th to endDay
4116%32%33%10%
510
August1st to 15thDay
8%325%43%15%4
300
16th to endDay
6%322%41%21%5%
268
September1st to 15thDay
10%434%33%15%1
255
16th to endDay
5%223%34%26%7%
134
October1st to 15thDay
7%421%41%16%8%
90
16th to endDay
9%327%35%17%7%
96
November1st to 15thDay
1416%38%21%17%
90
16th to endDay
16%13%23%41%5%
90
December1st to 15thDay
8%8%37%37%6%
90
16th to endDay
45%28%52%8%2
96
January1st to 15thNight
411%32%37%12%2
900
16th to endNight
5%10%35%38%8%
831
February1st to 15thNight
6%6%40%39%7%
704
16th to endNight
6%10%33%43%6%
632
March1st to 15thNight
5%5%35%42%10%1
720
16th to endNight
8%8%31%41%9%
678
April1st to 15thNight
8%9%30%41%8%
539
16th to endNight
18%5%28%34%11%
540
May1st to 15thNight
17%5%21%35%17%2
540
16th to endNight
11%120%38%25%2
563
June1st to 15thNight
8%217%48%20%1
540
16th to endNight
312%53%28%1
540
July1st to 15thNight
7%9%38%39%4
510
16th to endNight
5%5%39%45%3
564
August1st to 15thNight
5%19%41%37%4
527
16th to endNight
48%42%39%4
525
September1st to 15thNight
11%114%40%25%5%
495
16th to endNight
3213%44%32%3
492
October1st to 15thNight
12%320%39%19%3
652
16th to endNight
10%423%42%16%2
745
November1st to 15thNight
5%7%22%48%14%2
875
16th to endNight
5%7%28%46%12%1
900
December1st to 15thNight
6%7%33%44%7%1
900
16th to endNight
7%7%29%45%9%
960
Page generated at 2017-08-13 12:16:15. Version ac04

Copyright 2017 A. Danko


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