Folsom Lake State Recration Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Folsom Lake State Recration Area clear sky chart from 2005-11-05 to

2017-09-12
.

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
71%
15212
28%
46828
26%
15177
73%
15177
42%
24849

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
64%
716
18%
2470
20%
716
66%
716
29%
1453
January16th to endNight
60%
768
24%
2496
25%
768
62%
768
27%
1543
February1st to 15thNight
60%
696
23%
2269
25%
696
63%
696
28%
1394
February16th to endNight
57%
632
25%
1895
24%
632
61%
632
30%
1188
March1st to 15thNight
57%
720
17%
2061
17%
720
58%
720
26%
1374
March16th to endNight
57%
768
20%
2055
16%
768
60%
768
31%
1341
April1st to 15thNight
58%
719
20%
1799
12%
719
61%
719
32%
1203
April16th to endNight
66%
720
25%
1800
13%
720
69%
720
49%
1032
May1st to 15thNight
71%
569
29%
1649
22%
569
74%
569
56%
783
May16th to endNight
77%
374
27%
1496
32%
374
80%
374
47%
611
June1st to 15thNight
74%
360
27%
1440
33%
360
79%
360
49%
579
June16th to endNight
87%
360
36%
1440
49%
360
90%
360
67%
473
July1st to 15thNight
94%
340
35%
1360
48%
340
95%
340
77%
408
July16th to endNight
92%
498
39%
1528
40%
466
92%
466
76%
560
August1st to 15thNight
90%
574
37%
1647
29%
571
90%
571
75%
677
August16th to endNight
94%
764
45%
1910
29%
764
94%
764
84%
837
September1st to 15thNight
92%
706
42%
1765
30%
706
93%
706
80%
797
September16th to endNight
85%
656
43%
1780
38%
656
88%
656
71%
803
October1st to 15thNight
75%
660
31%
1980
33%
660
78%
660
51%
970
October16th to endNight
77%
704
34%
2112
36%
704
79%
704
48%
1074
November1st to 15thNight
73%
700
28%
2250
31%
700
75%
700
42%
1174
November16th to endNight
66%
720
24%
2418
26%
720
69%
720
35%
1306
December1st to 15thNight
58%
720
19%
2520
19%
720
62%
720
25%
1531
December16th to endNight
50%
768
21%
2688
20%
768
55%
768
22%
1738

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
9%212212335%64%
47834
Night
11%312212335%61%
47013
TransparencyDay
24%48%19%24%19%
47516
Night
26%49%19%22%18%
46830
SeeingDay
10%416%29%29%8%
5850
Night
12%19%35%34%6%
15226

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
18%5%2242335%5%46%
1467
16th to endDay
20%5%24323335%43%
1728
February1st to 15thDay
20%424323336%45%
1592
16th to endDay
20%5%24322345%44%
1579
March1st to 15thDay
19%5%24425%446%41%
1897
16th to endDay
16%424424446%43%
2168
April1st to 15thDay
16%6%23414446%44%
2149
16th to endDay
10%212212345%62%
2160
May1st to 15thDay
5%21213235%71%
2296
16th to endDay
5%213312345%64%
2615
June1st to 15thDay
5%212212335%68%
2520
16th to endDay
21112484%
2520
July1st to 15thDay
11112287%
2520
16th to endDay
111112286%
2533
August1st to 15thDay
1112287%
2303
16th to endDay
111388%
2292
September1st to 15thDay
1112385%
2114
16th to endDay
31121122379%
1846
October1st to 15thDay
5%12113336%68%
1650
16th to endDay
8%31331233462%
1760
November1st to 15thDay
10%21332335%7%56%
1609
16th to endDay
15%313315%345%51%
1540
December1st to 15thDay
20%5%3432433444%
1440
16th to endDay
23%6%2331245%6%40%
1536
January1st to 15thNight
17%313323447%47%
2470
16th to endNight
18%5%14324345%47%
2496
February1st to 15thNight
18%423333347%44%
2259
16th to endNight
20%313312345%48%
1895
March1st to 15thNight
19%5%24424345%43%
2061
16th to endNight
18%413224336%48%
2055
April1st to 15thNight
14%315%43445%6%45%
1799
16th to endNight
9%313111446%62%
1800
May1st to 15thNight
5%212212245%71%
1649
16th to endNight
5%21212348%66%
1496
June1st to 15thNight
4212212235%71%
1440
16th to endNight
1211111383%
1440
July1st to 15thNight
11112188%
1440
16th to endNight
11111386%
1634
August1st to 15thNight
1111113382%
1656
16th to endNight
112386%
1910
September1st to 15thNight
111112386%
1765
16th to endNight
11111223379%
1780
October1st to 15thNight
7%22212335%68%
1980
16th to endNight
6%213322236%64%
2112
November1st to 15thNight
11%212213346%59%
2250
16th to endNight
13%313312346%55%
2418
December1st to 15thNight
21%423222336%46%
2520
16th to endNight
23%5%24312335%43%
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
39%5%11%18%18%5%
1467
16th to endDay
44%5%8%15%15%10%
1728
February1st to 15thDay
42%5%9%19%17%5%
1592
16th to endDay
41%6%11%25%11%3
1579
March1st to 15thDay
43%6%10%18%15%5%
1897
16th to endDay
41%7%12%18%17%2
2168
April1st to 15thDay
39%6%10%24%14%4
2149
16th to endDay
23%5%12%25%25%6%
2160
May1st to 15thDay
17%39%28%31%9%
2296
16th to endDay
21%5%12%28%24%8%
2619
June1st to 15thDay
18%410%22%23%20%
2520
16th to endDay
7%1315%37%34%
2520
July1st to 15thDay
6%1210%25%53%
2371
16th to endDay
7%49%23%53%
2376
August1st to 15thDay
6%311%30%47%
2287
16th to endDay
5%212%38%40%
2292
September1st to 15thDay
6%1312%35%40%
2114
16th to endDay
12%25%20%34%24%
1846
October1st to 15thDay
16%49%23%27%18%
1650
16th to endDay
25%48%22%25%13%
1760
November1st to 15thDay
27%5%14%26%19%6%
1609
16th to endDay
35%7%10%21%19%5%
1540
December1st to 15thDay
45%411%17%16%3
1440
16th to endDay
44%7%10%17%16%4
1536
January1st to 15thNight
35%5%12%19%16%9%
2470
16th to endNight
39%48%14%16%15%
2496
February1st to 15thNight
39%310%20%17%7%
2270
16th to endNight
37%5%9%25%18%4
1895
March1st to 15thNight
42%5%10%18%17%5%
2061
16th to endNight
38%6%10%18%19%7%
2055
April1st to 15thNight
38%6%12%20%14%6%
1799
16th to endNight
23%5%14%23%24%8%
1800
May1st to 15thNight
16%411%25%28%14%
1650
16th to endNight
16%416%32%19%10%
1496
June1st to 15thNight
16%411%25%22%19%
1440
16th to endNight
9%1414%32%38%
1440
July1st to 15thNight
5%138%27%54%
1360
16th to endNight
7%1310%23%53%
1528
August1st to 15thNight
8%1413%27%45%
1647
16th to endNight
5%211%35%43%
1910
September1st to 15thNight
6%1411%36%39%
1765
16th to endNight
10%26%19%32%29%
1780
October1st to 15thNight
20%36%22%27%20%
1980
16th to endNight
21%47%22%26%17%
2112
November1st to 15thNight
25%413%25%19%10%
2250
16th to endNight
31%39%23%23%8%
2418
December1st to 15thNight
39%5%12%16%19%7%
2520
16th to endNight
44%6%9%15%18%7%
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
33%5%10%26%18%5%
95
16th to endDay
25%316%25%20%8%
256
February1st to 15thDay
23%5%15%24%22%7%
239
16th to endDay
25%6%19%24%18%5%
238
March1st to 15thDay
21%12%19%20%20%5%
270
16th to endDay
18%10%19%27%19%4
288
April1st to 15thDay
20%11%25%20%16%5%
269
16th to endDay
11%10%25%27%17%6%
270
May1st to 15thDay
6%6%26%30%22%8%
288
16th to endDay
7%5%20%24%30%11%
330
June1st to 15thDay
6%5%22%31%26%6%
315
16th to endDay
1113%33%41%8%
315
July1st to 15thDay
6%36%48%7%
305
16th to endDay
11%36%39%12%
327
August1st to 15thDay
311%39%38%6%
315
16th to endDay
9%30%44%14%
332
September1st to 15thDay
218%37%38%12%
300
16th to endDay
4118%30%32%13%
255
October1st to 15thDay
6%418%32%24%12%
255
16th to endDay
14%313%29%29%10%
272
November1st to 15thDay
12%29%26%34%14%
115
16th to endDay
14%315%32%33%
77
December1st to 15thDay
30%8%20%30%11%
60
16th to endDay
17%6%14%29%23%9%
64
January1st to 15thNight
17%28%33%28%9%
720
16th to endNight
20%28%33%26%9%
768
February1st to 15thNight
21%29%34%26%5%
704
16th to endNight
21%214%34%21%5%
632
March1st to 15thNight
20%311%30%27%5%
720
16th to endNight
19%214%33%25%3
768
April1st to 15thNight
13%415%35%26%3
719
16th to endNight
9%315%34%30%6%
720
May1st to 15thNight
6%117%37%32%4
570
16th to endNight
6%19%37%41%2
375
June1st to 15thNight
5%13%42%35%1
360
16th to endNight
25%42%46%1
360
July1st to 15thNight
144%50%2
340
16th to endNight
1235%55%5%
498
August1st to 15thNight
2343%47%3
574
16th to endNight
1238%53%4
764
September1st to 15thNight
2331%56%7%
706
16th to endNight
29%32%41%13%
656
October1st to 15thNight
8%110%35%34%10%
660
16th to endNight
7%9%33%35%12%
704
November1st to 15thNight
12%9%35%33%9%
700
16th to endNight
14%112%35%26%9%
720
December1st to 15thNight
22%29%34%23%7%
720
16th to endNight
26%313%29%21%4
768
Page generated at 2017-09-13 04:39:04. Version ac04

Copyright 2017 A. Danko


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