Grand Canyon (North Rim)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grand Canyon (North Rim) clear sky chart from 2005-11-05 to 2017-09-18.

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
64%
15577
33%
46929
25%
15540
71%
15540
48%
22845

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
66%
716
31%
2327
29%
716
72%
716
46%
1113
January16th to endNight
62%
768
34%
2496
32%
768
70%
768
42%
1236
February1st to 15thNight
61%
698
28%
2238
28%
698
67%
698
44%
1111
February16th to endNight
50%
632
34%
1895
25%
632
64%
632
42%
989
March1st to 15thNight
57%
720
35%
2001
24%
720
68%
720
48%
1017
March16th to endNight
56%
768
34%
2112
20%
768
68%
768
48%
1096
April1st to 15thNight
45%
685
27%
1944
13%
685
56%
685
42%
998
April16th to endNight
47%
540
39%
1623
20%
540
63%
540
47%
749
May1st to 15thNight
52%
540
33%
1619
22%
539
60%
539
52%
760
May16th to endNight
56%
561
31%
1685
19%
561
67%
561
50%
776
June1st to 15thNight
60%
540
28%
1620
23%
540
66%
540
58%
723
June16th to endNight
71%
540
33%
1620
29%
540
74%
540
70%
654
July1st to 15thNight
71%
510
22%
1530
19%
510
74%
510
46%
778
July16th to endNight
72%
564
23%
1593
20%
531
72%
531
35%
924
August1st to 15thNight
78%
539
30%
1611
24%
536
79%
536
46%
826
August16th to endNight
77%
597
37%
1780
30%
597
81%
597
46%
911
September1st to 15thNight
78%
720
31%
1980
25%
720
82%
720
53%
1020
September16th to endNight
77%
667
42%
1847
29%
667
85%
667
68%
821
October1st to 15thNight
68%
660
36%
1900
27%
660
75%
660
54%
912
October16th to endNight
69%
704
39%
2112
31%
704
77%
704
56%
960
November1st to 15thNight
70%
700
35%
2220
30%
700
78%
700
54%
992
November16th to endNight
68%
720
39%
2340
35%
720
77%
720
55%
1001
December1st to 15thNight
64%
720
31%
2340
26%
720
73%
720
46%
1118
December16th to endNight
56%
768
29%
2496
24%
768
64%
768
35%
1360

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
331332445%7%60%
47866
Night
221332345%7%63%
47124
TransparencyDay
22%47%19%27%18%
47561
Night
19%38%21%29%17%
46930
SeeingDay
9%13%27%30%15%3
5397
Night
5%6%18%34%28%6%
15589

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
23133245%7%9%56%
1611
16th to endDay
342433445%7%56%
1728
February1st to 15thDay
332331347%10%57%
1624
16th to endDay
43245%2345%8%55%
1579
March1st to 15thDay
132222435%7%64%
1959
16th to endDay
3323323449%59%
2112
April1st to 15thDay
342342335%7%58%
2003
16th to endDay
2314423347%62%
2334
May1st to 15thDay
331442345%7%59%
2331
16th to endDay
3212324447%62%
2429
June1st to 15thDay
111322222474%
2340
16th to endDay
11111123479%
2340
July1st to 15thDay
2315%6%36%6%5%7%50%
2340
16th to endDay
5%4346%47%7%8%9%37%
2467
August1st to 15thDay
44145%36%7%7%9%45%
2340
16th to endDay
43143345%6%6%55%
2417
September1st to 15thDay
4314435%45%8%54%
1980
16th to endDay
2213212245%70%
1838
October1st to 15thDay
3113224445%66%
1729
16th to endDay
222222235%71%
1760
November1st to 15thDay
1112213346%72%
1637
16th to endDay
2412213336%67%
1620
December1st to 15thDay
25%1441345%7%59%
1620
16th to endDay
3426%4345%7%9%48%
1728
January1st to 15thNight
2312323447%63%
2327
16th to endNight
3313323347%61%
2496
February1st to 15thNight
2213423447%62%
2227
16th to endNight
241442345%7%58%
1895
March1st to 15thNight
131222445%8%62%
2001
16th to endNight
1212425%45%8%62%
2112
April1st to 15thNight
121442445%7%61%
1944
16th to endNight
2212322347%66%
1623
May1st to 15thNight
2212214447%65%
1619
16th to endNight
1112323448%66%
1684
June1st to 15thNight
1212212345%72%
1620
16th to endNight
1212123478%
1620
July1st to 15thNight
12245%2446%8%57%
1620
16th to endNight
24246%46%7%7%11%42%
1701
August1st to 15thNight
21134345%6%7%58%
1620
16th to endNight
2233445%6%7%58%
1780
September1st to 15thNight
331232436%8%60%
1980
16th to endNight
1112124478%
1847
October1st to 15thNight
3212312236%69%
1900
16th to endNight
3212212345%70%
2112
November1st to 15thNight
1113323447%67%
2220
16th to endNight
2212122235%72%
2340
December1st to 15thNight
3312323448%62%
2340
16th to endNight
35%25%42445%9%52%
2496

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
20%7%12%33%23%2
1612
16th to endDay
24%5%10%29%25%4
1728
February1st to 15thDay
22%413%27%25%7%
1624
16th to endDay
25%48%21%33%6%
1579
March1st to 15thDay
19%3428%36%8%
1959
16th to endDay
22%37%25%31%10%
2112
April1st to 15thDay
24%36%20%30%14%
2003
16th to endDay
22%3421%33%15%
2334
May1st to 15thDay
23%36%16%35%14%
2331
16th to endDay
20%37%15%32%20%
2432
June1st to 15thDay
14%127%29%43%
2340
16th to endDay
9%12420%60%
2340
July1st to 15thDay
30%39%11%13%31%
2201
16th to endDay
36%7%11%15%14%14%
2312
August1st to 15thDay
30%6%11%13%17%21%
2325
16th to endDay
26%47%14%26%20%
2417
September1st to 15thDay
26%5%6%12%18%29%
1980
16th to endDay
17%26%13%29%30%
1838
October1st to 15thDay
19%3417%33%21%
1729
16th to endDay
16%25%20%38%15%
1760
November1st to 15thDay
13%27%28%34%13%
1637
16th to endDay
18%26%28%32%10%
1620
December1st to 15thDay
23%415%31%23%2
1620
16th to endDay
28%8%14%27%18%3
1728
January1st to 15thNight
20%313%30%29%2
2327
16th to endNight
22%49%28%27%7%
2496
February1st to 15thNight
21%410%27%27%8%
2238
16th to endNight
23%47%24%32%7%
1895
March1st to 15thNight
17%46%27%36%7%
2001
16th to endNight
19%47%29%28%10%
2112
April1st to 15thNight
20%37%20%31%16%
1944
16th to endNight
16%2422%38%14%
1623
May1st to 15thNight
16%36%20%37%15%
1620
16th to endNight
15%45%19%34%20%
1685
June1st to 15thNight
14%236%28%44%
1620
16th to endNight
9%115%18%63%
1620
July1st to 15thNight
23%310%13%14%33%
1530
16th to endNight
30%6%12%19%13%17%
1593
August1st to 15thNight
22%49%16%23%24%
1611
16th to endNight
22%47%14%26%24%
1780
September1st to 15thNight
20%38%16%21%30%
1980
16th to endNight
10%25%16%31%33%
1847
October1st to 15thNight
17%36%16%36%21%
1900
16th to endNight
15%27%14%41%18%
2112
November1st to 15thNight
16%28%24%33%13%
2220
16th to endNight
14%25%24%38%14%
2340
December1st to 15thNight
19%413%31%27%2
2340
16th to endNight
27%6%13%28%21%2
2496

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
18%16%16%32%12%3
90
16th to endDay
14%5%15%35%25%4
96
February1st to 15thDay
7%12%20%33%21%4
139
16th to endDay
15%26%28%21%6%1
238
March1st to 15thDay
12%21%26%21%17%
270
16th to endDay
11%22%31%25%7%1
288
April1st to 15thDay
16%28%25%18%8%3
269
16th to endDay
17%26%27%20%7%1
270
May1st to 15thDay
8%23%36%22%5%2
288
16th to endDay
11%16%32%21%14%2
330
June1st to 15thDay
414%39%26%11%3
315
16th to endDay
27%30%34%21%3
315
July1st to 15thDay
5%5%26%40%18%3
305
16th to endDay
8%322%38%22%5%
327
August1st to 15thDay
8%221%39%20%6%
315
16th to endDay
10%424%34%18%8%
332
September1st to 15thDay
6%428%36%18%5%
315
16th to endDay
8%9%23%33%20%4
264
October1st to 15thDay
11%17%26%24%15%4
169
16th to endDay
7%11%28%37%12%3
96
November1st to 15thDay
5%7%24%28%30%3
90
16th to endDay
15%17%18%40%7%
90
December1st to 15thDay
411%23%41%20%
90
16th to endDay
15%13%16%29%22%2
96
January1st to 15thNight
8%6%13%35%27%8%
720
16th to endNight
7%6%17%35%27%5%
768
February1st to 15thNight
5%7%19%38%23%5%
704
16th to endNight
6%10%26%34%18%2
632
March1st to 15thNight
411%22%33%24%3
720
16th to endNight
39%25%35%21%3
768
April1st to 15thNight
316%27%31%16%3
685
16th to endNight
6%14%28%29%16%4
540
May1st to 15thNight
47%32%33%18%3
540
16th to endNight
39%26%33%22%4
563
June1st to 15thNight
4427%41%19%2
540
16th to endNight
1222%42%29%2
540
July1st to 15thNight
414%37%37%5%
510
16th to endNight
6%9%35%38%9%
564
August1st to 15thNight
47%35%45%5%
539
16th to endNight
310%30%42%12%
597
September1st to 15thNight
6%7%29%43%12%
720
16th to endNight
3312%28%36%15%
667
October1st to 15thNight
35%17%37%24%10%
660
16th to endNight
4416%31%30%12%
704
November1st to 15thNight
3416%34%32%8%
700
16th to endNight
47%16%33%29%10%
720
December1st to 15thNight
7%6%16%38%25%5%
720
16th to endNight
8%7%20%35%24%4
768
Page generated at 2017-09-19 04:32:29. Version ac04

Copyright 2017 A. Danko


Grand Canyon (North Rim) Clear Sky Chart | Charts Home