Elk Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elk Creek clear sky chart from 2005-11-06 to 2024-01-16.

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
38%
24186
20%
74516
11%
24134
48%
24134
21%
48243

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 10thNight
15%
759
20%
2459
5%
757
32%
757
14%
1582
January11th to 20thNight
19%
744
21%
2417
8%
744
35%
744
13%
1631
January21st to endNight
17%
792
23%
2574
6%
792
37%
792
15%
1606
February1st to 10thNight
21%
720
20%
2340
9%
720
36%
720
15%
1495
February11th to 20thNight
10%
700
18%
2143
3%
699
26%
699
10%
1447
February21st to endNight
12%
592
22%
1759
5%
592
29%
592
15%
1231
March1st to 10thNight
20%
720
23%
1980
9%
720
33%
720
21%
1297
March11th to 20thNight
23%
720
16%
1980
6%
720
31%
720
16%
1397
March21st to endNight
24%
792
16%
2178
7%
792
31%
792
19%
1493
April1st to 10thNight
26%
720
18%
1977
7%
720
37%
720
21%
1283
April11th to 20thNight
31%
707
21%
1771
7%
707
40%
707
25%
1159
April21st to endNight
37%
540
23%
1620
12%
540
46%
540
24%
1027
May1st to 10thNight
37%
540
15%
1620
6%
540
44%
540
22%
1062
May11th to 20thNight
43%
531
15%
1593
8%
531
49%
531
21%
1087
May21st to endNight
54%
582
13%
1745
10%
582
56%
582
24%
1164
June1st to 10thNight
60%
540
14%
1620
12%
540
62%
540
28%
1050
June11th to 20thNight
60%
540
14%
1620
11%
540
63%
540
29%
1027
June21st to endNight
60%
540
18%
1620
13%
540
64%
540
29%
1014
July1st to 10thNight
66%
525
14%
1575
12%
525
68%
525
28%
1026
July11th to 20thNight
75%
522
13%
1566
12%
522
76%
522
30%
990
July21st to endNight
70%
591
14%
1672
11%
558
72%
558
29%
1058
August1st to 10thNight
61%
537
13%
1600
10%
534
62%
534
25%
1090
August11th to 20thNight
63%
534
18%
1598
16%
534
63%
534
24%
1102
August21st to endNight
65%
697
18%
1885
15%
697
66%
697
29%
1254
September1st to 10thNight
62%
720
21%
1939
15%
720
65%
720
30%
1262
September11th to 20thNight
56%
720
22%
1980
18%
720
58%
720
29%
1297
September21st to endNight
48%
720
20%
1980
14%
720
54%
720
24%
1358
October1st to 10thNight
47%
720
23%
2088
18%
720
54%
720
28%
1324
October11th to 20thNight
41%
720
26%
2160
18%
720
53%
720
27%
1338
October21st to endNight
39%
792
30%
2376
20%
792
53%
792
28%
1404
November1st to 10thNight
41%
740
27%
2240
18%
740
53%
740
27%
1345
November11th to 20thNight
36%
760
26%
2470
17%
760
50%
760
25%
1419
November21st to endNight
33%
760
26%
2470
14%
760
47%
760
22%
1472
December1st to 10thNight
22%
760
21%
2470
8%
760
38%
760
15%
1659
December11th to 20thNight
23%
760
22%
2980
10%
759
41%
759
13%
1920
December21st to endNight
22%
829
13%
4451
7%
817
35%
817
8%
2873

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%6%45%5%6%8%36%
74947
Night
12%7%36%5%35%5%6%8%41%
74866
TransparencyDay
45%7%11%20%14%3
74670
Night
41%7%12%22%16%3
74662
SeeingDay
23%15%24%20%13%6%
14052
Night
20%13%22%26%16%3
24199

By Month

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 10thDay
12%10%36%5%35%35%7%40%
1706
11th to 20thDay
15%10%5%7%6%35%5%5%5%36%
1665
21st to endDay
12%8%47%435%446%42%
1782
February1st to 10thDay
11%10%48%7%445%5%6%36%
1620
11th to 20thDay
15%9%48%5%35%347%36%
1699
21st to endDay
16%7%5%7%7%3345%6%37%
1495
March1st to 10thDay
11%7%25%5%345%5%6%46%
1980
11th to 20thDay
16%9%37%6%345%5%6%35%
1980
21st to endDay
16%9%46%5%35%35%6%36%
2178
April1st to 10thDay
11%6%36%6%345%5%8%43%
1981
11th to 20thDay
15%7%35%5%35%45%7%41%
2152
21st to endDay
15%6%26%7%36%5%5%7%37%
2340
May1st to 10thDay
13%7%37%6%46%5%7%7%34%
2340
11th to 20thDay
16%8%37%7%46%6%6%7%29%
2301
21st to endDay
15%6%36%7%46%5%9%9%30%
2531
June1st to 10thDay
12%6%25%7%5%7%6%7%9%33%
2340
11th to 20thDay
9%5%27%8%47%7%7%9%34%
2340
21st to endDay
9%5%37%7%47%7%8%10%33%
2340
July1st to 10thDay
9%7%37%8%5%7%8%7%10%29%
2340
11th to 20thDay
10%6%37%8%5%8%8%8%11%27%
2340
21st to endDay
12%6%49%8%5%8%7%7%8%26%
2547
August1st to 10thDay
12%7%38%8%5%7%7%8%10%25%
2327
11th to 20thDay
12%7%38%8%5%8%7%8%9%25%
2303
21st to endDay
11%6%46%7%46%6%8%9%33%
2452
September1st to 10thDay
14%6%37%6%45%6%6%6%38%
2016
11th to 20thDay
15%8%37%7%345%6%8%34%
1980
21st to endDay
21%7%35%5%35%5%47%35%
1980
October1st to 10thDay
17%5%35%5%3445%5%44%
1871
11th to 20thDay
14%6%35%5%3445%7%45%
1800
21st to endDay
13%6%26%5%34347%47%
1980
November1st to 10thDay
10%7%24424346%53%
1834
11th to 20thDay
11%6%25%435%5%5%7%47%
1710
21st to endDay
13%6%26%5%3345%6%46%
1710
December1st to 10thDay
14%11%5%6%6%335%5%8%34%
1710
11th to 20thDay
13%7%36%42445%8%44%
2153
21st to endDay
16%10%46%5%346%7%7%34%
3124
January1st to 10thNight
11%7%47%5%46%5%5%8%39%
2459
11th to 20thNight
13%8%46%7%35%5%7%6%36%
2417
21st to endNight
12%8%35%6%35%5%6%6%41%
2574
February1st to 10thNight
12%8%35%6%45%5%6%7%39%
2340
11th to 20thNight
15%9%36%5%45%5%6%6%36%
2143
21st to endNight
12%9%38%6%45%6%5%7%36%
1759
March1st to 10thNight
11%6%35%5%346%6%7%44%
1980
11th to 20thNight
14%7%37%7%5%5%5%6%7%34%
1980
21st to endNight
12%7%46%5%35%5%7%8%38%
2178
April1st to 10thNight
10%6%36%5%45%5%6%8%42%
1977
11th to 20thNight
12%6%25%5%346%6%8%44%
1771
21st to endNight
13%5%36%435%46%7%43%
1620
May1st to 10thNight
12%8%346%346%6%8%40%
1620
11th to 20thNight
12%7%36%6%35%5%6%9%38%
1592
21st to endNight
14%6%35%5%345%7%11%37%
1744
June1st to 10thNight
9%4246%46%6%7%11%40%
1620
11th to 20thNight
9%424436%6%7%11%43%
1620
21st to endNight
6%426%6%35%5%8%11%43%
1620
July1st to 10thNight
8%425%5%36%5%7%11%42%
1620
11th to 20thNight
6%4235%36%6%9%13%43%
1620
21st to endNight
6%425%6%37%7%9%12%38%
1771
August1st to 10thNight
10%7%36%6%46%6%8%10%36%
1611
11th to 20thNight
12%5%25%7%45%6%8%8%37%
1598
21st to endNight
10%6%25%5%35%5%7%10%41%
1885
September1st to 10thNight
11%6%35%435%5%6%7%46%
1939
11th to 20thNight
15%6%25%43445%8%43%
1980
21st to endNight
16%7%26%5%35%446%42%
1980
October1st to 10thNight
16%6%24423447%47%
2088
11th to 20thNight
13%7%25%434446%48%
2160
21st to endNight
12%7%25%424347%50%
2376
November1st to 10thNight
11%7%25%43445%5%51%
2240
11th to 20thNight
11%6%25%42445%7%49%
2470
21st to endNight
11%8%344345%6%7%46%
2470
December1st to 10thNight
14%9%47%5%35%5%5%7%36%
2470
11th to 20thNight
14%8%39%6%35%45%6%38%
3042
21st to endNight
16%9%5%6%6%35%5%6%7%31%
4532

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 10thDay
44%410%21%16%5%
1707
11th to 20thDay
50%47%21%14%4
1665
21st to endDay
43%39%23%18%3
1782
February1st to 10thDay
48%410%19%16%3
1620
11th to 20thDay
50%48%19%15%4
1709
21st to endDay
48%411%15%15%6%
1495
March1st to 10thDay
38%49%23%20%5%
1980
11th to 20thDay
50%5%9%17%15%4
1980
21st to endDay
49%5%10%22%11%3
2178
April1st to 10thDay
40%411%23%17%5%
1981
11th to 20thDay
42%5%10%19%18%5%
2152
21st to endDay
46%5%11%22%12%2
2340
May1st to 10thDay
48%7%14%18%11%2
2340
11th to 20thDay
52%8%13%19%7%2
2305
21st to endDay
47%8%14%23%7%
2531
June1st to 10thDay
45%10%14%20%10%1
2340
11th to 20thDay
44%11%14%16%14%2
2340
21st to endDay
42%10%14%19%13%1
2340
July1st to 10thDay
47%11%13%17%9%2
2275
11th to 20thDay
47%12%16%14%10%2
2271
21st to endDay
51%10%14%17%7%1
2405
August1st to 10thDay
51%10%15%18%6%
2314
11th to 20thDay
51%11%14%16%8%
2303
21st to endDay
45%8%16%17%11%3
2452
September1st to 10thDay
45%7%12%18%14%4
2016
11th to 20thDay
47%7%8%20%17%2
1980
21st to endDay
49%5%8%19%16%3
1980
October1st to 10thDay
42%5%8%23%17%5%
1871
11th to 20thDay
39%49%24%19%5%
1800
21st to endDay
39%37%26%19%7%
1980
November1st to 10thDay
34%49%20%26%7%
1834
11th to 20thDay
36%38%21%25%6%
1710
21st to endDay
40%48%21%24%4
1710
December1st to 10thDay
49%5%10%18%15%4
1710
11th to 20thDay
39%49%19%24%6%
2150
21st to endDay
47%5%8%20%17%3
3124
January1st to 10thNight
43%5%11%17%17%6%
2459
11th to 20thNight
48%5%8%17%16%5%
2417
21st to endNight
42%311%22%19%3
2574
February1st to 10thNight
43%411%24%16%2
2340
11th to 20thNight
48%49%20%15%5%
2144
21st to endNight
47%7%9%21%11%5%
1759
March1st to 10thNight
38%7%9%20%21%5%
1980
11th to 20thNight
49%5%10%22%13%1
1980
21st to endNight
43%7%12%22%13%3
2178
April1st to 10thNight
39%6%13%23%16%4
1977
11th to 20thNight
36%6%12%21%19%5%
1771
21st to endNight
40%5%15%26%13%2
1620
May1st to 10thNight
41%8%16%24%11%1
1620
11th to 20thNight
42%9%16%24%7%1
1593
21st to endNight
40%9%19%25%6%1
1745
June1st to 10thNight
36%10%20%22%11%1
1620
11th to 20thNight
33%11%20%23%11%1
1620
21st to endNight
33%10%18%24%12%2
1620
July1st to 10thNight
36%11%17%23%11%2
1575
11th to 20thNight
30%13%22%21%10%3
1566
21st to endNight
33%11%24%23%9%1
1672
August1st to 10thNight
41%10%19%21%9%
1600
11th to 20thNight
42%10%17%21%10%1
1598
21st to endNight
37%10%17%25%9%2
1885
September1st to 10thNight
36%9%16%20%16%3
1939
11th to 20thNight
40%6%12%23%18%1
1980
21st to endNight
44%7%8%24%15%2
1980
October1st to 10thNight
38%6%9%24%20%3
2088
11th to 20thNight
38%48%26%18%5%
2160
21st to endNight
36%37%24%22%8%
2376
November1st to 10thNight
35%5%9%19%24%7%
2240
11th to 20thNight
35%49%21%24%8%
2470
21st to endNight
38%48%24%21%5%
2470
December1st to 10thNight
47%5%9%20%15%4
2470
11th to 20thNight
46%5%7%16%22%4
3044
21st to endNight
50%6%10%17%16%2
4532

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 10thDay
40%26%22%9%31
270
11th to 20thDay
41%22%29%6%1
255
21st to endDay
42%25%23%7%2
264
February1st to 10thDay
38%30%23%6%2
240
11th to 20thDay
50%24%21%4
240
21st to endDay
43%30%21%6%
213
March1st to 10thDay
31%23%25%17%4
420
11th to 20thDay
36%25%23%11%41
420
21st to endDay
29%26%23%15%5%1
462
April1st to 10thDay
29%22%25%15%8%1
420
11th to 20thDay
27%18%25%16%11%3
412
21st to endDay
26%20%25%16%10%3
420
May1st to 10thDay
24%19%31%13%9%4
423
11th to 20thDay
20%14%27%21%10%7%
447
21st to endDay
20%9%22%21%18%10%
485
June1st to 10thDay
14%8%29%25%16%8%
450
11th to 20thDay
10%10%27%25%19%10%
450
21st to endDay
15%10%30%23%14%8%
450
July1st to 10thDay
12%5%20%27%23%14%
445
11th to 20thDay
8%5%16%35%24%12%
444
21st to endDay
11%319%29%22%15%
488
August1st to 10thDay
16%6%21%23%20%14%
446
11th to 20thDay
11%421%23%25%16%
439
21st to endDay
13%418%26%21%18%
495
September1st to 10thDay
14%419%25%25%14%
450
11th to 20thDay
16%417%25%24%14%
450
21st to endDay
26%9%18%24%18%5%
450
October1st to 10thDay
21%11%18%24%21%5%
450
11th to 20thDay
20%16%24%22%14%3
450
21st to endDay
22%15%27%22%11%3
495
November1st to 10thDay
20%16%26%24%10%3
432
11th to 20thDay
29%20%28%18%41
270
21st to endDay
24%23%28%18%5%1
270
December1st to 10thDay
34%22%32%9%3
270
11th to 20thDay
31%22%28%15%31
270
21st to endDay
33%22%28%11%5%1
297
January1st to 10thNight
28%24%27%17%41
760
11th to 20thNight
28%22%26%21%2
744
21st to endNight
27%23%29%18%2
792
February1st to 10thNight
27%21%27%23%2
720
11th to 20thNight
35%27%25%13%
703
21st to endNight
27%25%33%13%2
592
March1st to 10thNight
24%21%32%20%3
720
11th to 20thNight
29%20%26%18%7%1
720
21st to endNight
22%17%32%22%7%
792
April1st to 10thNight
24%19%27%24%6%
720
11th to 20thNight
20%18%25%26%9%1
707
21st to endNight
19%13%25%34%8%1
540
May1st to 10thNight
18%12%27%26%14%2
540
11th to 20thNight
15%10%22%31%19%3
531
21st to endNight
17%417%27%28%6%
584
June1st to 10thNight
11%318%38%27%4
540
11th to 20thNight
9%419%30%33%4
540
21st to endNight
8%419%34%32%4
540
July1st to 10thNight
10%113%28%40%7%
525
11th to 20thNight
6%29%35%42%7%
522
21st to endNight
7%211%36%38%7%
591
August1st to 10thNight
13%312%28%39%5%
537
11th to 20thNight
15%110%31%35%7%
534
21st to endNight
12%210%29%39%9%
697
September1st to 10thNight
13%313%27%37%7%
720
11th to 20thNight
17%315%27%33%6%
720
21st to endNight
20%6%18%28%25%2
720
October1st to 10thNight
17%10%20%23%25%5%
720
11th to 20thNight
20%11%22%29%15%3
720
21st to endNight
21%13%22%30%11%2
792
November1st to 10thNight
18%13%23%30%14%2
740
11th to 20thNight
24%13%23%29%9%1
760
21st to endNight
24%17%23%27%9%1
760
December1st to 10thNight
26%22%25%22%5%
760
11th to 20thNight
24%18%27%25%5%1
760
21st to endNight
28%18%26%24%5%
836
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