Blue River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blue River clear sky chart from 2005-11-05 to 2017-11-30.

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
32%
15245
6%
47641
4%
15212
33%
15212
10%
38829

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
16%
852
4%
2787
3%
847
17%
847
5%
2492
January16th to endNight
19%
773
6%
2721
4%
773
22%
773
5%
2379
February1st to 15thNight
20%
701
5%
2429
5%
697
21%
697
7%
2062
February16th to endNight
34%
632
7%
1984
7%
632
36%
632
12%
1585
March1st to 15thNight
19%
720
5%
2160
3%
720
21%
720
7%
1882
March16th to endNight
28%
768
4%
2007
2%
768
29%
768
10%
1718
April1st to 15thNight
37%
719
5%
1799
3%
719
37%
719
13%
1488
April16th to endNight
36%
440
7%
1520
6%
440
38%
440
10%
1205
May1st to 15thNight
47%
359
6%
1440
8%
359
47%
359
12%
1054
May16th to endNight
49%
374
2%
1339
1%
374
49%
374
11%
1021
June1st to 15thNight
45%
360
0%
1080
0%
360
45%
360
13%
845
June16th to endNight
46%
360
0%
1080
0%
360
46%
360
13%
854
July1st to 15thNight
56%
340
0%
1022
0%
340
56%
340
21%
707
July16th to endNight
62%
376
5%
1350
5%
354
64%
354
21%
843
August1st to 15thNight
67%
360
10%
1432
14%
358
69%
358
22%
859
August16th to endNight
57%
562
14%
1708
14%
562
57%
562
24%
1122
September1st to 15thNight
54%
720
13%
1800
8%
720
54%
720
25%
1280
September16th to endNight
45%
716
14%
1944
9%
716
46%
716
19%
1440
October1st to 15thNight
39%
720
8%
2163
7%
720
40%
720
15%
1642
October16th to endNight
25%
768
5%
2496
3%
768
28%
768
7%
2127
November1st to 15thNight
15%
760
3%
2633
3%
760
17%
760
4%
2355
November16th to endNight
16%
962
3%
2912
1%
962
18%
962
5%
2611
December1st to 15thNight
17%
911
6%
2763
4%
911
20%
911
6%
2433
December16th to endNight
14%
992
3%
3072
1%
992
15%
992
4%
2825

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
18%14%5%8%7%35%445%22%
48806
Night
18%17%5%7%6%34445%21%
47786
TransparencyDay
64%7%11%11%4
48455
Night
65%6%11%11%4
47641
SeeingDay
23%11%26%24%12%2
6736
Night
28%6%23%25%14%1
15250

By Month

Percentage Cloud Cover NW (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
21%26%7%10%5%4232212%
1161
16th to endDay
16%24%6%11%5%3334415%
1500
February1st to 15thDay
18%21%7%8%6%3433318%
1433
16th to endDay
10%17%7%10%7%44345%23%
1490
March1st to 15thDay
15%27%6%8%7%3444414%
1800
16th to endDay
14%22%7%10%6%35%445%14%
2217
April1st to 15thDay
13%20%6%10%9%45%45%415%
2149
16th to endDay
16%18%5%7%6%45%446%18%
2439
May1st to 15thDay
17%14%46%6%35%5%35%25%
2511
16th to endDay
20%11%48%7%46%5%46%19%
2769
June1st to 15thDay
27%9%49%7%45%44419%
2880
16th to endDay
23%9%5%9%8%46%45%418%
2880
July1st to 15thDay
15%7%46%6%36%5%5%7%31%
2877
16th to endDay
13%5%36%7%45%5%5%7%35%
2724
August1st to 15thDay
11%5%27%7%35%6%5%8%35%
2520
16th to endDay
17%7%36%6%35%45%7%32%
2494
September1st to 15thDay
17%8%35%5%34445%37%
2160
16th to endDay
26%8%26%5%24445%28%
2013
October1st to 15thDay
20%13%37%6%34445%25%
1797
16th to endDay
26%19%37%5%24445%15%
1728
November1st to 15thDay
24%23%6%9%7%3332312%
1554
16th to endDay
17%24%6%10%7%3433414%
1361
December1st to 15thDay
17%21%6%11%8%3423316%
1197
16th to endDay
17%27%6%10%7%3433312%
1152
January1st to 15thNight
24%23%8%9%6%3322410%
2787
16th to endNight
17%23%8%9%7%35%445%10%
2721
February1st to 15thNight
18%25%6%9%6%22335%15%
2417
16th to endNight
9%19%6%8%6%35%5%6%7%20%
1984
March1st to 15thNight
16%26%7%8%6%2443415%
2160
16th to endNight
14%20%5%8%6%4445%5%18%
2003
April1st to 15thNight
12%19%6%7%6%34446%22%
1799
16th to endNight
14%16%48%6%45%5%5%5%23%
1520
May1st to 15thNight
17%9%37%6%345%37%30%
1439
16th to endNight
15%8%37%7%37%6%7%8%23%
1339
June1st to 15thNight
23%7%35%6%35%5%5%7%24%
1080
16th to endNight
17%7%46%6%5%7%5%5%7%25%
1080
July1st to 15thNight
15%5%25%425%45%7%40%
1082
16th to endNight
11%5%26%5%35%5%5%8%41%
1444
August1st to 15thNight
9%4245%346%5%8%44%
1440
16th to endNight
12%6%145%35%5%5%9%40%
1708
September1st to 15thNight
15%6%25%6%34345%42%
1800
16th to endNight
23%8%24425%45%7%32%
1944
October1st to 15thNight
19%10%47%5%3435%5%29%
2163
16th to endNight
27%16%38%5%24446%15%
2496
November1st to 15thNight
29%23%5%7%5%3432310%
2633
16th to endNight
21%23%6%10%7%35%3349%
2912
December1st to 15thNight
19%24%6%9%7%3443412%
2763
16th to endNight
18%30%8%10%6%344247%
3072

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
80%5%7%41
1161
16th to endDay
74%48%6%5%1
1500
February1st to 15thDay
70%7%9%7%3
1433
16th to endDay
65%6%13%9%5%
1490
March1st to 15thDay
76%7%9%5%1
1800
16th to endDay
73%7%12%5%1
2217
April1st to 15thDay
73%7%10%8%
2149
16th to endDay
68%7%12%8%1
2439
May1st to 15thDay
60%7%12%14%3
2511
16th to endDay
64%8%12%11%2
2773
June1st to 15thDay
69%6%9%10%4
2880
16th to endDay
68%8%10%9%3
2880
July1st to 15thDay
53%8%12%16%9%
2708
16th to endDay
47%9%15%20%5%1
2555
August1st to 15thDay
45%11%17%18%7%
2503
16th to endDay
51%8%15%18%5%
2494
September1st to 15thDay
49%6%14%21%6%
2160
16th to endDay
59%8%12%12%6%
2013
October1st to 15thDay
61%8%13%13%2
1797
16th to endDay
72%7%11%7%1
1728
November1st to 15thDay
80%5%5%421
1554
16th to endDay
75%7%5%5%5%
1361
December1st to 15thDay
74%6%6%7%4
1197
16th to endDay
79%5%5%6%2
1152
January1st to 15thNight
81%36%43
2787
16th to endNight
75%6%6%5%31
2721
February1st to 15thNight
73%49%6%41
2429
16th to endNight
63%7%13%9%5%
1984
March1st to 15thNight
74%5%9%6%2
2160
16th to endNight
69%7%14%6%1
2007
April1st to 15thNight
64%6%13%11%3
1799
16th to endNight
62%8%13%11%4
1520
May1st to 15thNight
54%9%14%15%6%
1440
16th to endNight
56%11%14%14%2
1339
June1st to 15thNight
57%9%12%14%4
1080
16th to endNight
57%11%15%11%4
1080
July1st to 15thNight
44%9%15%20%9%
1022
16th to endNight
39%9%17%23%8%
1350
August1st to 15thNight
36%10%20%24%7%
1432
16th to endNight
39%10%19%23%7%
1708
September1st to 15thNight
44%8%15%21%9%1
1800
16th to endNight
52%6%14%16%8%1
1944
October1st to 15thNight
57%6%13%17%4
2163
16th to endNight
70%7%11%8%1
2496
November1st to 15thNight
79%5%5%5%3
2633
16th to endNight
79%5%6%43
2912
December1st to 15thNight
77%45%8%3
2763
16th to endNight
82%5%442
3072

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
11%5%28%30%16%8%
60
16th to endDay
37%6%25%23%6%1
64
February1st to 15thDay
25%12%35%17%8%
93
16th to endDay
19%17%30%23%8%
223
March1st to 15thDay
37%23%27%10%1
270
16th to endDay
25%20%34%13%5%
288
April1st to 15thDay
23%20%27%21%7%1
269
16th to endDay
25%17%28%17%8%2
270
May1st to 15thDay
26%10%24%27%10%1
288
16th to endDay
20%7%22%24%17%6%
484
June1st to 15thDay
27%5%23%27%14%1
675
16th to endDay
23%5%24%28%15%2
675
July1st to 15thDay
17%6%21%31%18%3
642
16th to endDay
13%9%27%32%13%2
393
August1st to 15thDay
11%6%26%34%17%3
315
16th to endDay
15%14%32%28%8%1
332
September1st to 15thDay
25%13%24%21%13%1
315
16th to endDay
32%11%26%20%9%
315
October1st to 15thDay
30%13%27%18%7%2
312
16th to endDay
35%11%27%15%9%
144
November1st to 15thDay
30%18%31%12%6%1
96
16th to endDay
37%15%17%17%37%
89
December1st to 15thDay
26%6%23%20%20%3
60
16th to endDay
14%9%37%20%17%1
64
January1st to 15thNight
37%9%25%20%5%1
852
16th to endNight
30%7%30%23%7%
773
February1st to 15thNight
36%7%23%21%10%
704
16th to endNight
19%6%27%30%14%
632
March1st to 15thNight
31%11%30%20%6%
720
16th to endNight
25%8%26%25%11%1
768
April1st to 15thNight
21%6%22%28%17%2
719
16th to endNight
22%7%23%27%17%1
440
May1st to 15thNight
19%5%18%31%23%1
360
16th to endNight
20%218%31%23%3
375
June1st to 15thNight
24%417%32%19%2
360
16th to endNight
22%319%27%21%5%
360
July1st to 15thNight
17%215%29%31%2
340
16th to endNight
11%5%11%37%31%2
376
August1st to 15thNight
10%115%30%39%4
360
16th to endNight
16%217%36%24%1
562
September1st to 15thNight
19%315%30%26%5%
720
16th to endNight
29%416%27%19%2
716
October1st to 15thNight
27%5%20%30%13%2
720
16th to endNight
39%5%21%23%9%1
768
November1st to 15thNight
43%10%23%17%5%
760
16th to endNight
35%9%28%18%6%1
962
December1st to 15thNight
35%7%30%19%6%
911
16th to endNight
33%8%31%20%5%
992
Page generated at 2017-12-01 09:13:40. Version ac04

Copyright 2017 A. Danko


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