Lake Arrowhead State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Arrowhead State Park clear sky chart from 2005-11-05 to 2017-09-19.

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
51%
15654
31%
46960
21%
15609
62%
15609
44%
24493

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
43%
899
33%
2327
15%
895
56%
895
46%
1293
January16th to endNight
44%
960
37%
2496
16%
960
57%
960
48%
1379
February1st to 15thNight
38%
704
29%
2112
15%
700
50%
700
39%
1152
February16th to endNight
30%
632
33%
1894
12%
632
48%
632
40%
999
March1st to 15thNight
35%
591
31%
2031
16%
591
52%
591
34%
1095
March16th to endNight
36%
576
27%
2112
18%
576
50%
576
35%
1065
April1st to 15thNight
28%
539
25%
1951
13%
539
47%
539
35%
970
April16th to endNight
35%
540
30%
1669
17%
540
54%
540
42%
871
May1st to 15thNight
37%
540
26%
1620
15%
540
54%
540
39%
900
May16th to endNight
52%
562
29%
1684
24%
561
65%
561
45%
869
June1st to 15thNight
60%
540
24%
1620
20%
540
69%
540
50%
804
June16th to endNight
71%
540
27%
1620
28%
540
74%
540
51%
795
July1st to 15thNight
75%
510
23%
1530
25%
510
78%
510
47%
785
July16th to endNight
86%
564
34%
1594
39%
531
88%
531
59%
729
August1st to 15thNight
88%
539
35%
1610
41%
536
88%
536
55%
773
August16th to endNight
84%
573
31%
1908
37%
573
85%
573
46%
928
September1st to 15thNight
69%
540
25%
1980
28%
540
72%
540
34%
1061
September16th to endNight
71%
504
35%
1857
34%
504
77%
504
38%
904
October1st to 15thNight
59%
520
36%
1840
31%
520
66%
520
42%
889
October16th to endNight
54%
704
38%
2112
21%
704
65%
704
52%
1010
November1st to 15thNight
52%
817
33%
2217
15%
817
62%
817
53%
1129
November16th to endNight
43%
900
36%
2340
16%
900
55%
900
46%
1309
December1st to 15thNight
45%
900
35%
2340
16%
900
57%
900
45%
1306
December16th to endNight
39%
960
32%
2496
14%
960
50%
960
40%
1478

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
8%313323446%57%
47853
Night
7%313313346%60%
47156
Cloud CoverDay
8%313323346%57%
47851
Night
7%313313346%60%
47156
TransparencyDay
27%39%24%25%9%
47551
Night
24%38%22%27%12%
46961
SeeingDay
8%320%31%26%9%
5630
Night
9%5%29%38%16%1
15656

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
10%413222336%59%
1611
16th to endDay
10%223313335%60%
1737
February1st to 15thDay
10%423312235%60%
1750
16th to endDay
12%6%2321122459%
1580
March1st to 15thDay
13%41432435%6%51%
1929
16th to endDay
11%5%23323245%54%
2112
April1st to 15thDay
10%413213346%58%
1994
16th to endDay
9%423313336%58%
2289
May1st to 15thDay
10%5%24423345%52%
2331
16th to endDay
8%425%435%45%8%47%
2430
June1st to 15thDay
6%3123145%5%8%57%
2340
16th to endDay
5%212323448%60%
2340
July1st to 15thDay
7%313425%5%7%9%49%
2340
16th to endDay
31123246%6%9%58%
2466
August1st to 15thDay
321443446%7%58%
2340
16th to endDay
5%313335%5%6%8%52%
2291
September1st to 15thDay
12%31432445%6%52%
1980
16th to endDay
7%31342446%6%56%
1848
October1st to 15thDay
9%32323436%59%
1779
16th to endDay
5%21231233469%
1760
November1st to 15thDay
6%213311335%66%
1638
16th to endDay
9%21221323465%
1620
December1st to 15thDay
10%6%24313335%56%
1620
16th to endDay
12%5%23312336%54%
1728
January1st to 15thNight
8%412213346%62%
2327
16th to endNight
8%323213235%63%
2496
February1st to 15thNight
11%41321233459%
2102
16th to endNight
11%322212235%61%
1894
March1st to 15thNight
11%413322345%56%
2031
16th to endNight
8%42341335%7%57%
2112
April1st to 15thNight
8%323313347%57%
1951
16th to endNight
8%313222347%60%
1669
May1st to 15thNight
9%31331345%7%56%
1619
16th to endNight
5%21322435%8%60%
1683
June1st to 15thNight
421221345%11%58%
1620
16th to endNight
322331325%9%62%
1620
July1st to 15thNight
42125%2446%9%57%
1620
16th to endNight
12221235%9%65%
1702
August1st to 15thNight
21232346%9%62%
1620
16th to endNight
321232446%10%56%
1908
September1st to 15thNight
10%423324437%53%
1980
16th to endNight
5%313424446%58%
1857
October1st to 15thNight
9%31221235%5%62%
1840
16th to endNight
6%21221223370%
2112
November1st to 15thNight
5%33212445%66%
2217
16th to endNight
9%41221233463%
2340
December1st to 15thNight
11%312312345%60%
2340
16th to endNight
10%5%23323345%55%
2496

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
9%413212336%59%
1611
16th to endDay
10%223324235%60%
1737
February1st to 15thDay
9%423212335%60%
1750
16th to endDay
12%7%2321222459%
1580
March1st to 15thDay
13%41432335%6%52%
1929
16th to endDay
11%5%23314245%54%
2110
April1st to 15thDay
10%312223246%58%
1994
16th to endDay
9%323323346%58%
2289
May1st to 15thDay
10%5%24423345%52%
2331
16th to endDay
8%42443445%8%47%
2430
June1st to 15thDay
6%31331445%8%56%
2340
16th to endDay
5%21332345%8%59%
2340
July1st to 15thDay
7%313435%47%9%49%
2340
16th to endDay
3112325%5%6%9%58%
2466
August1st to 15thDay
321443445%7%59%
2340
16th to endDay
5%313335%5%7%8%52%
2291
September1st to 15thDay
12%314323446%52%
1980
16th to endDay
7%3133245%5%5%56%
1848
October1st to 15thDay
9%312223335%59%
1779
16th to endDay
5%21221233469%
1760
November1st to 15thDay
6%212312335%67%
1638
16th to endDay
9%212223225%65%
1620
December1st to 15thDay
10%6%24313235%55%
1620
16th to endDay
12%5%23312336%54%
1728
January1st to 15thNight
8%312212346%62%
2327
16th to endNight
8%322213235%63%
2496
February1st to 15thNight
11%5%13213335%59%
2102
16th to endNight
11%322212245%61%
1894
March1st to 15thNight
11%413322335%56%
2031
16th to endNight
8%41332325%7%57%
2112
April1st to 15thNight
8%313323347%57%
1951
16th to endNight
8%213312346%59%
1669
May1st to 15thNight
9%31321345%7%56%
1619
16th to endNight
5%21322445%9%59%
1683
June1st to 15thNight
32122135%5%11%58%
1620
16th to endNight
321321325%10%62%
1620
July1st to 15thNight
421242446%8%57%
1620
16th to endNight
211221236%9%65%
1702
August1st to 15thNight
21332346%8%62%
1620
16th to endNight
42133245%7%10%56%
1908
September1st to 15thNight
10%323323347%53%
1980
16th to endNight
5%3243235%46%58%
1857
October1st to 15thNight
9%31221234462%
1840
16th to endNight
6%21221223470%
2112
November1st to 15thNight
5%21321245%5%66%
2217
16th to endNight
9%41231233463%
2340
December1st to 15thNight
11%312213235%60%
2340
16th to endNight
10%5%23223445%55%
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
28%16%22%31%9%
1612
16th to endDay
28%1422%32%9%
1737
February1st to 15thDay
28%25%23%30%10%
1751
16th to endDay
31%15%19%29%12%
1580
March1st to 15thDay
32%47%21%24%9%
1929
16th to endDay
33%37%24%21%9%
2112
April1st to 15thDay
26%210%25%19%14%
1994
16th to endDay
28%39%22%25%10%
2289
May1st to 15thDay
34%49%18%23%9%
2331
16th to endDay
33%5%12%22%21%4
2434
June1st to 15thDay
24%5%12%26%25%5%
2340
16th to endDay
22%5%12%27%24%7%
2340
July1st to 15thDay
29%5%14%26%21%2
2201
16th to endDay
19%5%12%30%27%3
2311
August1st to 15thDay
22%412%27%26%6%
2326
16th to endDay
26%5%12%28%21%5%
2291
September1st to 15thDay
32%410%21%22%9%
1980
16th to endDay
27%48%24%23%12%
1848
October1st to 15thDay
26%28%24%26%11%
1779
16th to endDay
18%26%21%32%17%
1760
November1st to 15thDay
21%28%26%28%13%
1638
16th to endDay
24%2421%31%15%
1620
December1st to 15thDay
32%16%25%27%5%
1620
16th to endDay
33%26%25%25%7%
1728
January1st to 15thNight
24%27%19%31%14%
2327
16th to endNight
25%16%18%32%15%
2496
February1st to 15thNight
29%27%19%26%14%
2112
16th to endNight
27%15%22%26%16%
1894
March1st to 15thNight
31%26%19%24%15%
2031
16th to endNight
27%411%24%23%9%
2112
April1st to 15thNight
27%211%19%21%16%
1951
16th to endNight
25%311%20%26%12%
1669
May1st to 15thNight
26%5%12%17%23%13%
1620
16th to endNight
22%5%16%24%24%6%
1685
June1st to 15thNight
20%313%32%23%6%
1620
16th to endNight
19%411%25%29%9%
1620
July1st to 15thNight
22%5%11%31%23%5%
1530
16th to endNight
15%311%29%35%4
1594
August1st to 15thNight
18%310%27%28%11%
1610
16th to endNight
21%413%25%26%8%
1908
September1st to 15thNight
32%39%21%24%10%
1980
16th to endNight
25%36%21%26%15%
1857
October1st to 15thNight
24%39%23%22%16%
1840
16th to endNight
19%2420%31%21%
2112
November1st to 15thNight
18%37%24%27%18%
2217
16th to endNight
25%2417%32%17%
2340
December1st to 15thNight
27%16%24%28%10%
2340
16th to endNight
31%25%22%26%11%
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
17%5%33%32%7%3
90
16th to endDay
5%6%44%28%13%2
96
February1st to 15thDay
47%38%41%7%
90
16th to endDay
12%339%33%11%
81
March1st to 15thDay
14%10%38%31%5%
90
16th to endDay
6%5%42%28%13%4
96
April1st to 15thDay
15%11%25%30%15%
113
16th to endDay
11%10%40%26%8%2
399
May1st to 15thDay
10%6%40%28%10%2
468
16th to endDay
12%5%31%30%16%3
517
June1st to 15thDay
6%116%44%24%7%
495
16th to endDay
6%19%38%32%11%
495
July1st to 15thDay
6%6%39%36%10%
475
16th to endDay
3323%48%20%
515
August1st to 15thDay
4226%48%16%
493
16th to endDay
6%27%32%36%15%
331
September1st to 15thDay
1119%42%35%
135
16th to endDay
1327%39%29%
99
October1st to 15thDay
5%28%41%31%11%
90
16th to endDay
9%17%38%31%3
96
November1st to 15thDay
14%417%34%25%3
90
16th to endDay
18%12%34%24%6%3
90
December1st to 15thDay
11%438%27%14%3
90
16th to endDay
9%7%42%27%13%
96
January1st to 15thNight
10%7%34%38%8%
900
16th to endNight
9%6%35%39%7%
960
February1st to 15thNight
13%8%36%34%6%
704
16th to endNight
13%10%43%29%3
632
March1st to 15thNight
13%8%39%33%4
591
16th to endNight
9%8%42%32%6%
576
April1st to 15thNight
9%10%48%27%4
539
16th to endNight
9%7%46%29%7%
540
May1st to 15thNight
10%5%42%30%9%1
540
16th to endNight
5%332%38%17%1
563
June1st to 15thNight
5%27%43%21%
540
16th to endNight
4115%53%22%2
540
July1st to 15thNight
411%47%32%2
510
16th to endNight
2342%47%3
564
August1st to 15thNight
2345%45%2
539
16th to endNight
4443%43%3
573
September1st to 15thNight
12%19%41%32%2
540
16th to endNight
6%14%43%31%2
504
October1st to 15thNight
10%224%40%21%1
520
16th to endNight
7%431%38%17%
704
November1st to 15thNight
6%432%38%15%1
817
16th to endNight
11%6%35%32%11%
900
December1st to 15thNight
14%6%32%40%6%
900
16th to endNight
13%6%36%35%7%
960
Page generated at 2017-09-20 03:49:46. Version ac04

Copyright 2017 A. Danko


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