Lake Almanor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Almanor clear sky chart from 2005-11-05 to 2019-06-10.

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
61%
17336
26%
53904
22%
17305
66%
17305
36%
29943

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
55%
837
18%
2926
17%
836
59%
836
25%
1795
January16th to endNight
49%
896
21%
2923
20%
896
53%
896
24%
1866
February1st to 15thNight
50%
816
21%
2678
20%
816
56%
816
24%
1679
February16th to endNight
49%
736
21%
2210
18%
736
54%
736
24%
1439
March1st to 15thNight
45%
840
14%
2416
11%
840
49%
840
21%
1675
March16th to endNight
46%
896
17%
2394
11%
896
50%
896
24%
1614
April1st to 15thNight
44%
839
17%
2099
8%
839
48%
839
26%
1454
April16th to endNight
56%
832
22%
2080
11%
832
60%
832
41%
1240
May1st to 15thNight
59%
578
26%
1838
19%
578
66%
578
42%
925
May16th to endNight
58%
438
16%
1752
18%
438
61%
438
24%
990
June1st to 15thNight
69%
408
26%
1632
31%
408
75%
408
39%
728
June16th to endNight
81%
390
31%
1560
42%
390
85%
390
54%
586
July1st to 15thNight
90%
370
32%
1480
46%
370
92%
370
68%
482
July16th to endNight
92%
482
39%
1613
44%
455
93%
455
76%
550
August1st to 15thNight
89%
586
38%
1731
33%
583
90%
583
70%
727
August16th to endNight
89%
828
42%
2070
28%
828
89%
828
81%
934
September1st to 15thNight
85%
780
42%
1950
29%
780
87%
780
75%
902
September16th to endNight
79%
776
41%
2105
34%
776
84%
776
67%
957
October1st to 15thNight
63%
780
31%
2340
28%
780
72%
780
46%
1160
October16th to endNight
70%
832
32%
2496
32%
832
76%
832
48%
1251
November1st to 15thNight
60%
820
25%
2665
23%
820
67%
820
32%
1510
November16th to endNight
53%
840
20%
2870
19%
840
58%
840
29%
1640
December1st to 15thNight
51%
840
21%
2940
18%
840
57%
840
23%
1827
December16th to endNight
42%
896
21%
3136
16%
896
51%
896
20%
2012

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
7%6%23313345%58%
54618
Night
7%6%23323346%56%
54082
TransparencyDay
28%49%20%22%15%
54296
Night
29%5%10%21%20%12%
53905
SeeingDay
15%14%27%23%14%4
7954
Night
12%6%15%33%28%4
17349

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
8%9%36%43246%7%43%
1672
16th to endDay
11%12%25%41445%7%40%
2002
February1st to 15thDay
12%10%2432345%7%43%
1846
16th to endDay
8%16%45%42445%5%38%
1836
March1st to 15thDay
13%14%45%423447%34%
2202
16th to endDay
11%15%35%322346%40%
2534
April1st to 15thDay
12%12%34424447%38%
2509
16th to endDay
8%5%23323346%54%
2485
May1st to 15thDay
5%322213346%63%
2770
16th to endDay
10%5%26%5%23345%47%
3063
June1st to 15thDay
5%323323336%61%
2857
16th to endDay
21211122480%
2730
July1st to 15thDay
1111122482%
2730
16th to endDay
11112483%
2804
August1st to 15thDay
111112482%
2471
16th to endDay
111387%
2484
September1st to 15thDay
11111233478%
2340
16th to endDay
311112235%75%
2180
October1st to 15thDay
7%21322333466%
1950
16th to endDay
7%413313346%59%
2080
November1st to 15thDay
9%5%1433445%8%49%
1854
16th to endDay
10%7%24424446%47%
1747
December1st to 15thDay
11%9%45%42345%7%40%
1680
16th to endDay
12%11%344245%5%7%38%
1792
January1st to 15thNight
8%9%35%434347%45%
2926
16th to endNight
10%11%24323446%44%
2923
February1st to 15thNight
10%10%24324447%44%
2666
16th to endNight
9%14%34313346%44%
2210
March1st to 15thNight
11%14%35%325%348%36%
2416
16th to endNight
10%12%25%42435%6%43%
2394
April1st to 15thNight
10%10%244345%5%7%41%
2099
16th to endNight
7%6%22323337%58%
2080
May1st to 15thNight
6%213213336%64%
1838
16th to endNight
10%5%245%23445%50%
1752
June1st to 15thNight
4322213337%65%
1632
16th to endNight
31111233278%
1560
July1st to 15thNight
11121113382%
1560
16th to endNight
11122385%
1714
August1st to 15thNight
11111122479%
1740
16th to endNight
111113384%
2070
September1st to 15thNight
111122481%
1950
16th to endNight
21111222478%
2105
October1st to 15thNight
6%21321223468%
2340
16th to endNight
5%31221335%6%63%
2496
November1st to 15thNight
9%5%2332345%8%51%
2665
16th to endNight
9%6%2432445%8%48%
2870
December1st to 15thNight
13%8%34323448%44%
2940
16th to endNight
12%13%3442335%7%40%
3136

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
41%8%13%23%11%2
1672
16th to endDay
44%6%10%18%12%6%
2002
February1st to 15thDay
40%412%24%14%2
1846
16th to endDay
46%5%10%25%10%1
1836
March1st to 15thDay
50%5%9%19%13%2
2202
16th to endDay
44%6%15%19%10%3
2534
April1st to 15thDay
45%6%13%20%13%
2509
16th to endDay
30%6%13%26%20%3
2485
May1st to 15thDay
22%412%29%26%5%
2770
16th to endDay
38%5%11%23%17%4
3067
June1st to 15thDay
25%49%22%27%11%
2857
16th to endDay
11%25%17%38%24%
2730
July1st to 15thDay
8%2411%29%44%
2581
16th to endDay
7%2312%26%47%
2643
August1st to 15thDay
8%1414%29%41%
2455
16th to endDay
5%214%34%42%
2484
September1st to 15thDay
10%2311%33%38%
2340
16th to endDay
12%27%25%30%21%
2180
October1st to 15thDay
23%36%24%27%14%
1950
16th to endDay
26%411%21%24%12%
2080
November1st to 15thDay
33%6%13%22%17%6%
1854
16th to endDay
38%5%12%21%17%3
1747
December1st to 15thDay
42%6%11%20%17%1
1680
16th to endDay
45%6%11%20%14%1
1792
January1st to 15thNight
38%6%15%23%13%2
2926
16th to endNight
42%5%10%17%16%7%
2923
February1st to 15thNight
39%6%11%24%14%3
2678
16th to endNight
41%5%11%26%11%2
2210
March1st to 15thNight
47%5%13%17%12%3
2416
16th to endNight
41%7%15%21%11%2
2394
April1st to 15thNight
41%8%15%22%10%2
2099
16th to endNight
26%5%15%30%18%3
2080
May1st to 15thNight
22%414%28%24%5%
1839
16th to endNight
34%6%15%23%15%3
1752
June1st to 15thNight
20%5%13%24%25%10%
1632
16th to endNight
13%35%17%37%22%
1560
July1st to 15thNight
8%1412%27%45%
1480
16th to endNight
6%1312%26%48%
1613
August1st to 15thNight
10%1413%28%40%
1731
16th to endNight
6%1315%32%40%
2070
September1st to 15thNight
9%1412%33%37%
1950
16th to endNight
11%26%25%32%21%
2105
October1st to 15thNight
20%36%25%27%16%
2340
16th to endNight
20%411%24%27%10%
2496
November1st to 15thNight
30%6%14%24%16%6%
2665
16th to endNight
34%5%14%24%16%4
2870
December1st to 15thNight
39%6%10%21%18%3
2940
16th to endNight
44%5%9%19%18%2
3136

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
30%7%27%24%10%
120
16th to endDay
23%14%21%24%12%2
338
February1st to 15thDay
26%15%22%25%8%1
326
16th to endDay
27%17%27%20%7%
341
March1st to 15thDay
33%19%22%13%8%2
390
16th to endDay
25%22%26%15%9%
416
April1st to 15thDay
29%20%27%16%41
389
16th to endDay
19%22%24%17%13%3
378
May1st to 15thDay
15%20%29%20%10%4
408
16th to endDay
20%14%27%18%12%6%
458
June1st to 15thDay
12%16%29%23%12%5%
412
16th to endDay
416%31%25%15%6%
375
July1st to 15thDay
25%36%33%15%6%
365
16th to endDay
18%34%28%17%10%
391
August1st to 15thDay
210%31%30%14%11%
359
16th to endDay
111%28%29%18%11%
396
September1st to 15thDay
112%27%32%20%5%
375
16th to endDay
6%15%29%26%19%3
375
October1st to 15thDay
12%15%31%22%16%2
375
16th to endDay
14%11%23%24%20%5%
400
November1st to 15thDay
16%6%20%22%27%6%
180
16th to endDay
17%14%19%25%17%5%
139
December1st to 15thDay
24%12%18%23%15%6%
120
16th to endDay
17%12%20%25%21%3
128
January1st to 15thNight
13%5%18%41%16%4
840
16th to endNight
18%421%33%18%3
896
February1st to 15thNight
17%7%17%33%20%2
824
16th to endNight
19%10%16%36%15%2
736
March1st to 15thNight
21%9%18%28%17%3
840
16th to endNight
19%12%16%29%19%1
896
April1st to 15thNight
17%10%21%32%15%1
839
16th to endNight
12%10%17%31%24%4
832
May1st to 15thNight
8%7%19%34%27%2
579
16th to endNight
13%6%14%25%35%4
439
June1st to 15thNight
5%416%30%38%3
408
16th to endNight
3210%38%43%2
390
July1st to 15thNight
1332%60%2
370
16th to endNight
429%60%4
482
August1st to 15thNight
2430%55%6%
586
16th to endNight
16%42%44%5%
828
September1st to 15thNight
217%33%46%8%
780
16th to endNight
4310%36%35%10%
776
October1st to 15thNight
8%8%13%32%29%6%
780
16th to endNight
9%312%33%32%7%
832
November1st to 15thNight
11%6%17%36%24%4
820
16th to endNight
15%8%17%31%22%4
840
December1st to 15thNight
18%6%17%35%19%3
840
16th to endNight
22%9%21%32%11%1
896
Page generated at 2019-06-10 16:29:48. Version ac04

Copyright 2019 A. Danko


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