Divide
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Divide 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
42%
15794
26%
46505
13%
15749
55%
15749
34%
25911

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
33%
900
30%
2506
12%
895
50%
895
37%
1298
January16th to endNight
30%
783
33%
2511
14%
783
53%
783
38%
1215
February1st to 15thNight
24%
702
26%
2235
8%
699
44%
699
30%
1181
February16th to endNight
23%
632
34%
1894
7%
632
50%
632
33%
1001
March1st to 15thNight
32%
720
26%
2109
9%
720
47%
720
33%
1165
March16th to endNight
29%
681
27%
2025
10%
681
46%
681
31%
1146
April1st to 15thNight
30%
539
23%
1798
10%
539
48%
539
28%
967
April16th to endNight
29%
540
20%
1800
9%
540
46%
540
23%
1092
May1st to 15thNight
41%
540
18%
1648
12%
540
49%
540
24%
1052
May16th to endNight
41%
562
16%
1498
8%
561
49%
561
31%
943
June1st to 15thNight
58%
540
20%
1440
13%
540
64%
540
44%
788
June16th to endNight
68%
540
23%
1440
18%
540
72%
540
45%
802
July1st to 15thNight
67%
510
15%
1360
13%
510
68%
510
27%
915
July16th to endNight
74%
564
16%
1470
16%
531
74%
531
28%
957
August1st to 15thNight
67%
527
15%
1643
16%
524
68%
524
26%
1023
August16th to endNight
69%
525
20%
1750
21%
525
72%
525
30%
1029
September1st to 15thNight
62%
495
24%
1650
22%
495
68%
495
29%
957
September16th to endNight
59%
492
32%
1771
26%
492
71%
492
39%
863
October1st to 15thNight
48%
649
29%
1969
15%
649
60%
649
39%
1041
October16th to endNight
49%
718
34%
2126
17%
718
61%
718
43%
1105
November1st to 15thNight
44%
875
33%
2275
15%
875
55%
875
45%
1217
November16th to endNight
36%
900
35%
2379
13%
900
52%
900
46%
1236
December1st to 15thNight
27%
900
24%
2520
7%
900
42%
900
32%
1366
December16th to endNight
24%
960
26%
2688
8%
960
41%
960
28%
1552

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
46%35%5%35%5%5%7%47%
47479
Night
25%2442445%8%54%
46683
Cloud CoverDay
5%6%25%43446%7%48%
47477
Night
35%2432445%8%56%
46683
TransparencyDay
33%6%12%22%19%6%
47159
Night
26%5%13%26%20%6%
46505
SeeingDay
12%17%30%22%13%4
5670
Night
5%14%31%30%15%2
15797

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
5%24424347%59%
1432
16th to endDay
5%25%412347%60%
1724
February1st to 15thDay
5%37%42246%8%52%
1624
16th to endDay
6%36%42345%8%54%
1580
March1st to 15thDay
27%46%6%2445%8%47%
1850
16th to endDay
39%46%4245%6%9%44%
2198
April1st to 15thDay
49%26%5%35%45%7%44%
2150
16th to endDay
6%12%47%7%25%45%6%37%
2160
May1st to 15thDay
8%10%47%6%35%5%6%7%34%
2301
16th to endDay
6%7%36%5%37%5%6%7%40%
2616
June1st to 15thDay
5%5%25%435%6%6%8%45%
2520
16th to endDay
3325%436%6%6%8%49%
2520
July1st to 15thDay
8%5%26%6%5%7%6%6%9%35%
2520
16th to endDay
7%7%36%7%47%7%7%8%32%
2594
August1st to 15thDay
9%7%37%5%5%7%6%6%7%34%
2221
16th to endDay
7%6%25%6%35%5%7%9%39%
2100
September1st to 15thDay
8%6%25%6%35%5%6%6%44%
1980
16th to endDay
5%413323445%60%
1859
October1st to 15thDay
5%32433446%7%55%
1658
16th to endDay
46%23213435%61%
1733
November1st to 15thDay
15%2422335%8%60%
1583
16th to endDay
424313347%62%
1580
December1st to 15thDay
425%423449%57%
1440
16th to endDay
1435%5%335%5%9%52%
1536
January1st to 15thNight
314323447%63%
2506
16th to endNight
425%313237%65%
2511
February1st to 15thNight
5%36%5%23348%57%
2225
16th to endNight
5%25%41345%6%60%
1894
March1st to 15thNight
2425%32446%8%55%
2109
16th to endNight
36%34413348%55%
2025
April1st to 15thNight
38%23424446%55%
1798
16th to endNight
5%11%46%412338%47%
1800
May1st to 15thNight
6%8%36%5%345%6%8%41%
1647
16th to endNight
46%245%245%6%9%47%
1497
June1st to 15thNight
3313315%5%7%9%57%
1440
16th to endNight
1212325%7%7%8%57%
1440
July1st to 15thNight
5%5%36%6%36%6%6%9%39%
1440
16th to endNight
6%5%136%5%6%7%8%10%37%
1571
August1st to 15thNight
6%425%5%46%5%7%9%42%
1652
16th to endNight
6%424435%6%7%10%44%
1750
September1st to 15thNight
6%4245%35%6%6%9%45%
1650
16th to endNight
341332345%5%62%
1771
October1st to 15thNight
431231345%7%61%
1969
16th to endNight
341332345%6%60%
2126
November1st to 15thNight
423314348%62%
2275
16th to endNight
1423313337%65%
2379
December1st to 15thNight
1315%42445%10%56%
2520
16th to endNight
15%35%5%2435%8%53%
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
15%24423348%60%
1432
16th to endDay
1426%22225%7%60%
1724
February1st to 15thDay
15%36%42335%9%53%
1624
16th to endDay
6%35%32345%7%56%
1580
March1st to 15thDay
37%35%5%2445%6%50%
1850
16th to endDay
48%35%42446%9%45%
2196
April1st to 15thDay
49%244345%5%7%46%
2150
16th to endDay
6%12%5%6%5%2445%6%39%
2160
May1st to 15thDay
8%10%37%5%35%5%6%7%36%
2301
16th to endDay
7%7%25%435%6%6%8%41%
2616
June1st to 15thDay
6%4145%345%7%9%47%
2520
16th to endDay
43145%35%6%6%8%51%
2520
July1st to 15thDay
9%5%25%5%5%6%7%6%8%37%
2520
16th to endDay
9%6%26%7%37%6%7%8%34%
2594
August1st to 15thDay
11%5%26%6%36%6%6%7%35%
2221
16th to endDay
8%5%25%5%35%5%7%9%41%
2100
September1st to 15thDay
9%5%245%345%6%6%46%
1980
16th to endDay
6%413323345%61%
1859
October1st to 15thDay
5%32243436%6%57%
1658
16th to endDay
46%13213445%62%
1733
November1st to 15thDay
15%1431335%7%62%
1583
16th to endDay
5%2331335%6%63%
1580
December1st to 15thDay
435%423449%57%
1440
16th to endDay
5%26%42446%8%53%
1536
January1st to 15thNight
31431245%7%64%
2506
16th to endNight
1324313236%66%
2511
February1st to 15thNight
5%35%423438%58%
2225
16th to endNight
5%3431345%6%62%
1894
March1st to 15thNight
242432445%8%56%
2109
16th to endNight
37%24423347%57%
2025
April1st to 15thNight
38%23313347%56%
1798
16th to endNight
6%11%35%412246%49%
1800
May1st to 15thNight
7%8%25%435%5%5%8%43%
1647
16th to endNight
5%5%2442446%9%49%
1497
June1st to 15thNight
32122245%6%8%60%
1440
16th to endNight
2212235%5%6%9%58%
1440
July1st to 15thNight
5%426%437%6%7%8%42%
1440
16th to endNight
7%3235%47%7%7%10%40%
1571
August1st to 15thNight
6%5%145%35%5%7%8%45%
1652
16th to endNight
7%4245%245%8%10%46%
1750
September1st to 15thNight
6%424325%7%6%9%47%
1650
16th to endNight
331322335%6%63%
1771
October1st to 15thNight
431221435%7%63%
1969
16th to endNight
341321345%6%61%
2126
November1st to 15thNight
42322335%7%64%
2275
16th to endNight
1414313246%66%
2379
December1st to 15thNight
131441345%10%58%
2520
16th to endNight
15%45%424448%55%
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%316%29%20%4
1433
16th to endDay
22%414%32%19%7%
1724
February1st to 15thDay
27%416%29%16%4
1625
16th to endDay
27%49%28%24%5%
1580
March1st to 15thDay
33%410%24%21%5%
1850
16th to endDay
34%6%10%25%18%3
2198
April1st to 15thDay
37%5%11%23%15%6%
2150
16th to endDay
46%5%10%19%16%3
2160
May1st to 15thDay
47%8%11%18%14%1
2301
16th to endDay
39%9%13%19%13%5%
2620
June1st to 15thDay
32%8%13%16%19%10%
2520
16th to endDay
28%7%10%19%23%10%
2520
July1st to 15thDay
42%7%11%16%14%7%
2371
16th to endDay
45%8%15%18%9%2
2432
August1st to 15thDay
46%8%12%13%13%5%
2206
16th to endDay
38%7%13%20%16%3
2100
September1st to 15thDay
39%5%10%17%18%8%
1980
16th to endDay
25%49%23%30%6%
1859
October1st to 15thDay
26%5%10%24%26%6%
1658
16th to endDay
24%48%25%29%7%
1733
November1st to 15thDay
22%311%23%26%12%
1583
16th to endDay
20%37%28%29%9%
1580
December1st to 15thDay
25%5%17%27%20%4
1440
16th to endDay
27%7%15%25%17%6%
1536
January1st to 15thNight
19%416%31%23%4
2506
16th to endNight
20%312%30%23%8%
2511
February1st to 15thNight
26%414%34%15%3
2235
16th to endNight
23%49%29%25%7%
1894
March1st to 15thNight
26%5%11%27%25%4
2109
16th to endNight
28%5%10%29%21%4
2025
April1st to 15thNight
28%5%12%28%19%5%
1798
16th to endNight
38%5%12%25%14%3
1800
May1st to 15thNight
40%6%13%23%13%2
1648
16th to endNight
33%7%17%22%13%5%
1498
June1st to 15thNight
21%7%19%22%15%14%
1440
16th to endNight
21%8%13%22%21%12%
1440
July1st to 15thNight
39%8%14%18%11%6%
1360
16th to endNight
35%10%19%22%10%1
1470
August1st to 15thNight
36%9%16%18%12%5%
1643
16th to endNight
32%8%17%24%13%3
1750
September1st to 15thNight
32%7%14%20%16%7%
1650
16th to endNight
23%410%29%26%5%
1771
October1st to 15thNight
21%7%13%22%27%7%
1969
16th to endNight
21%5%9%28%29%6%
2126
November1st to 15thNight
19%411%26%23%13%
2275
16th to endNight
19%310%27%29%9%
2379
December1st to 15thNight
22%6%18%28%18%4
2520
16th to endNight
29%416%23%20%5%
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
15%20%27%17%18%
90
16th to endDay
419%38%27%10%
96
February1st to 15thDay
8%47%33%7%2
90
16th to endDay
11%28%32%19%6%2
81
March1st to 15thDay
17%24%37%15%4
140
16th to endDay
19%32%35%10%1
288
April1st to 15thDay
15%37%29%11%41
269
16th to endDay
29%33%23%10%2
270
May1st to 15thDay
13%19%35%23%6%1
402
16th to endDay
12%17%31%23%12%2
517
June1st to 15thDay
8%14%28%25%19%4
495
16th to endDay
49%31%26%21%6%
495
July1st to 15thDay
11%422%27%24%9%
475
16th to endDay
11%319%30%26%9%
453
August1st to 15thDay
17%9%27%30%11%4
300
16th to endDay
14%5%36%25%14%2
268
September1st to 15thDay
9%19%36%26%5%1
255
16th to endDay
6%11%39%21%14%5%
134
October1st to 15thDay
117%24%31%15%10%
90
16th to endDay
9%17%27%29%12%4
96
November1st to 15thDay
6%12%26%21%26%6%
90
16th to endDay
12%26%42%11%7%
90
December1st to 15thDay
10%36%38%11%3
90
16th to endDay
6%27%39%21%41
96
January1st to 15thNight
5%22%35%23%11%2
900
16th to endNight
319%41%26%7%1
783
February1st to 15thNight
421%44%25%4
704
16th to endNight
323%44%23%4
632
March1st to 15thNight
418%40%27%8%
720
16th to endNight
7%17%41%26%7%
681
April1st to 15thNight
7%23%34%26%6%
539
16th to endNight
11%17%35%26%8%1
540
May1st to 15thNight
10%8%34%32%11%1
540
16th to endNight
7%9%32%33%15%1
563
June1st to 15thNight
5%5%25%41%17%3
540
16th to endNight
2120%46%24%3
540
July1st to 15thNight
7%112%37%37%4
510
16th to endNight
7%18%32%44%6%
564
August1st to 15thNight
9%112%36%33%6%
527
16th to endNight
8%110%34%37%6%
525
September1st to 15thNight
7%119%38%27%5%
495
16th to endNight
45%23%36%23%5%
492
October1st to 15thNight
5%12%30%31%15%4
649
16th to endNight
5%9%30%32%17%4
718
November1st to 15thNight
414%33%31%13%2
875
16th to endNight
417%38%28%9%1
900
December1st to 15thNight
326%39%22%6%1
900
16th to endNight
5%23%39%22%7%
960
Page generated at 2017-08-13 12:16:33. Version ac04

Copyright 2017 A. Danko


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