South Lake Tahoe
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the South Lake Tahoe clear sky chart from 2005-11-06 to 2024-01-12.

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
54%
23397
31%
74567
22%
23355
64%
23355
43%
36040

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 10thNight
41%
757
25%
2646
16%
756
56%
756
29%
1374
January11th to 20thNight
49%
724
26%
2476
18%
724
62%
724
33%
1249
January21st to endNight
45%
792
28%
2574
20%
792
56%
792
31%
1433
February1st to 10thNight
47%
720
27%
2334
22%
720
57%
720
34%
1227
February11th to 20thNight
44%
700
30%
2099
20%
700
57%
700
38%
1088
February21st to endNight
42%
592
29%
1776
19%
592
57%
592
33%
968
March1st to 10thNight
37%
720
23%
2160
12%
720
51%
720
30%
1179
March11th to 20thNight
44%
720
25%
2004
16%
720
54%
720
37%
1091
March21st to endNight
39%
792
23%
2040
9%
792
50%
792
36%
1145
April1st to 10thNight
43%
720
25%
1800
10%
720
52%
720
38%
1054
April11th to 20thNight
44%
711
28%
1779
11%
711
51%
711
42%
966
April21st to endNight
49%
720
26%
1800
10%
720
56%
720
48%
968
May1st to 10thNight
50%
626
27%
1706
14%
626
56%
626
42%
898
May11th to 20thNight
56%
402
31%
1464
27%
402
66%
402
42%
653
May21st to endNight
56%
388
24%
1552
23%
388
64%
388
37%
716
June1st to 10thNight
60%
360
28%
1440
27%
360
72%
360
42%
611
June11th to 20thNight
61%
360
37%
1440
35%
360
78%
360
58%
489
June21st to endNight
66%
360
35%
1440
37%
360
78%
360
60%
496
July1st to 10thNight
71%
350
37%
1400
38%
350
84%
350
68%
452
July11th to 20thNight
64%
348
38%
1392
35%
348
77%
348
61%
482
July21st to endNight
68%
469
40%
1559
33%
443
79%
443
56%
637
August1st to 10thNight
71%
562
35%
1627
23%
559
77%
559
59%
762
August11th to 20thNight
69%
712
37%
1780
18%
712
75%
712
69%
859
August21st to endNight
68%
792
43%
1980
22%
792
74%
792
75%
908
September1st to 10thNight
73%
720
46%
1800
25%
720
80%
720
80%
799
September11th to 20thNight
68%
720
46%
1826
27%
720
78%
720
70%
840
September21st to endNight
64%
720
42%
1980
30%
720
76%
720
61%
905
October1st to 10thNight
60%
720
34%
2128
25%
720
73%
720
52%
1005
October11th to 20thNight
67%
720
41%
2160
36%
720
77%
720
61%
909
October21st to endNight
63%
792
41%
2412
34%
792
76%
792
58%
1024
November1st to 10thNight
58%
740
33%
2405
29%
740
68%
740
42%
1149
November11th to 20thNight
55%
760
34%
2470
26%
760
68%
760
46%
1123
November21st to endNight
52%
760
34%
2517
25%
760
67%
760
41%
1178
December1st to 10thNight
48%
760
25%
2660
19%
760
59%
760
34%
1315
December11th to 20thNight
44%
760
23%
3194
19%
759
55%
759
22%
1728
December21st to endNight
36%
828
16%
4747
17%
817
49%
817
16%
2360

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
232342445%7%63%
74766
Night
232442446%8%62%
74952
TransparencyDay
21%39%22%27%18%
74475
Night
21%411%24%26%14%
74764
SeeingDay
15%16%31%23%11%3
13942
Night
10%9%23%32%21%5%
23413

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 10thDay
1423437%7%8%11%51%
1519
11th to 20thDay
1324445%6%8%9%56%
1502
21st to endDay
27%35%6%45%7%6%11%44%
1782
February1st to 10thDay
1425%4346%6%10%55%
1624
11th to 20thDay
1346%6%35%5%6%9%53%
1750
21st to endDay
15%26%6%35%5%7%10%51%
1480
March1st to 10thDay
15%37%6%46%7%8%10%42%
1800
11th to 20thDay
15%45%5%35%6%7%12%47%
1952
21st to endDay
1425%5%36%6%7%10%51%
2314
April1st to 10thDay
3425%5%35%46%10%52%
2160
11th to 20thDay
23145%25%5%6%9%57%
2129
21st to endDay
25%2332445%9%61%
2160
May1st to 10thDay
35%2443435%9%59%
2253
11th to 20thDay
342343445%7%60%
2426
21st to endDay
6%6%25%5%3446%7%52%
2723
June1st to 10thDay
231332446%7%63%
2520
11th to 20thDay
1212212345%78%
2520
21st to endDay
2112223345%75%
2520
July1st to 10thDay
11212233481%
2520
11th to 20thDay
2112213345%78%
2520
21st to endDay
221222444473%
2663
August1st to 10thDay
221332334474%
2301
11th to 20thDay
121223235%78%
2122
21st to endDay
111121222385%
2376
September1st to 10thDay
11121233481%
2160
11th to 20thDay
2112322346%74%
2134
21st to endDay
321321223477%
1980
October1st to 10thDay
3414323345%67%
1828
11th to 20thDay
221331335%6%73%
1800
21st to endDay
1213323447%71%
1944
November1st to 10thDay
1323435%5%6%8%59%
1674
11th to 20thDay
221233447%10%63%
1710
21st to endDay
13244345%7%11%57%
1658
December1st to 10thDay
24334346%7%10%55%
1520
11th to 20thDay
27%46%8%5%6%7%8%10%38%
1928
21st to endDay
15%37%5%35%6%7%13%44%
2794
January1st to 10thNight
2425%5%45%5%8%13%47%
2646
11th to 20thNight
1325%5%35%6%8%11%51%
2476
21st to endNight
26%36%5%36%6%8%10%46%
2574
February1st to 10thNight
1326%5%345%7%9%55%
2334
11th to 20thNight
1435%425%6%8%11%52%
2098
21st to endNight
426%5%25%5%9%11%51%
1776
March1st to 10thNight
15%35%5%347%9%11%48%
2160
11th to 20thNight
1424426%6%8%11%52%
2004
21st to endNight
1423435%5%7%11%55%
2040
April1st to 10thNight
25%245%35%7%7%10%51%
1800
11th to 20thNight
132433348%10%59%
1779
21st to endNight
341322446%8%63%
1800
May1st to 10thNight
342333345%6%63%
1706
11th to 20thNight
242332436%9%62%
1464
21st to endNight
46%2342335%8%59%
1552
June1st to 10thNight
3312333445%68%
1440
11th to 20thNight
111223235%81%
1440
21st to endNight
221221233479%
1440
July1st to 10thNight
11111233483%
1440
11th to 20thNight
121231223379%
1440
21st to endNight
221331334474%
1651
August1st to 10thNight
321232344373%
1636
11th to 20thNight
211221223479%
1780
21st to endNight
12111122484%
1980
September1st to 10thNight
11111112486%
1800
11th to 20thNight
1112112325%81%
1826
21st to endNight
221321324476%
1980
October1st to 10thNight
4313423245%71%
2128
11th to 20thNight
2212212345%76%
2160
21st to endNight
1212312348%73%
2412
November1st to 10thNight
23133245%7%10%61%
2405
11th to 20thNight
13122245%7%10%63%
2470
21st to endNight
232432346%9%62%
2517
December1st to 10thNight
2323435%47%11%56%
2660
11th to 20thNight
35%35%5%45%7%8%12%44%
3276
21st to endNight
5%37%7%46%7%8%10%42%
4862

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 10thDay
26%5%17%30%18%3
1519
11th to 20thDay
25%415%27%20%9%
1502
21st to endDay
34%411%24%23%4
1782
February1st to 10thDay
26%413%27%22%7%
1624
11th to 20thDay
30%211%28%24%6%
1760
21st to endDay
29%415%29%18%5%
1480
March1st to 10thDay
36%314%26%18%2
1800
11th to 20thDay
30%5%17%21%21%5%
1952
21st to endDay
28%5%22%28%14%3
2314
April1st to 10thDay
29%418%24%21%5%
2160
11th to 20thDay
25%314%28%23%7%
2132
21st to endDay
22%216%31%24%4
2160
May1st to 10thDay
25%28%32%27%5%
2253
11th to 20thDay
25%39%29%28%7%
2429
21st to endDay
32%210%28%22%6%
2724
June1st to 10thDay
21%310%23%32%10%
2520
11th to 20thDay
12%26%24%36%21%
2520
21st to endDay
13%2314%34%34%
2520
July1st to 10thDay
10%229%26%52%
2451
11th to 20thDay
11%2213%25%47%
2445
21st to endDay
16%2310%26%43%
2515
August1st to 10thDay
15%2211%27%43%
2285
11th to 20thDay
11%219%33%43%
2122
21st to endDay
9%1110%36%43%
2376
September1st to 10thDay
9%229%35%43%
2160
11th to 20thDay
14%2319%39%23%
2134
21st to endDay
14%1320%39%23%
1980
October1st to 10thDay
21%25%18%31%22%
1828
11th to 20thDay
15%15%27%33%19%
1800
21st to endDay
16%18%27%32%16%
1944
November1st to 10thDay
22%410%24%29%10%
1674
11th to 20thDay
18%316%23%32%8%
1710
21st to endDay
21%312%28%27%9%
1658
December1st to 10thDay
25%5%13%27%24%6%
1520
11th to 20thDay
40%5%13%20%17%5%
1928
21st to endDay
30%6%17%23%21%3
2794
January1st to 10thNight
28%5%15%29%20%3
2646
11th to 20thNight
26%416%28%19%8%
2476
21st to endNight
32%412%23%23%5%
2574
February1st to 10thNight
26%5%12%27%21%9%
2334
11th to 20thNight
24%314%30%23%5%
2099
21st to endNight
26%6%14%30%19%5%
1776
March1st to 10thNight
27%5%18%27%20%4
2160
11th to 20thNight
24%5%18%25%22%6%
2004
21st to endNight
23%5%23%28%17%4
2040
April1st to 10thNight
26%419%27%18%5%
1800
11th to 20thNight
21%418%30%21%7%
1779
21st to endNight
19%418%36%21%3
1800
May1st to 10thNight
22%412%30%28%5%
1706
11th to 20thNight
20%211%34%26%6%
1464
21st to endNight
25%315%30%23%4
1552
June1st to 10thNight
19%410%25%32%9%
1440
11th to 20thNight
10%25%26%35%21%
1440
21st to endNight
11%2316%35%32%
1440
July1st to 10thNight
8%2110%32%48%
1400
11th to 20thNight
12%1213%26%46%
1392
21st to endNight
15%2210%26%44%
1559
August1st to 10thNight
16%2313%27%39%
1627
11th to 20thNight
12%2112%33%40%
1780
21st to endNight
9%1111%35%44%
1980
September1st to 10thNight
6%1110%37%44%
1800
11th to 20thNight
9%25%23%38%23%
1826
21st to endNight
13%2322%36%24%
1980
October1st to 10thNight
19%27%21%31%20%
2128
11th to 20thNight
12%17%26%36%19%
2160
21st to endNight
12%28%27%38%13%
2412
November1st to 10thNight
18%5%10%27%28%12%
2405
11th to 20thNight
15%6%12%28%30%8%
2470
21st to endNight
20%411%29%27%9%
2517
December1st to 10thNight
24%5%15%25%25%7%
2660
11th to 20thNight
32%6%17%22%17%5%
3276
21st to endNight
32%6%17%22%19%4
4862

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 10thDay
33%18%23%17%8%1
180
11th to 20thDay
27%12%28%20%8%4
216
21st to endDay
19%18%28%19%12%3
374
February1st to 10thDay
23%19%29%19%8%2
342
11th to 20thDay
24%19%29%21%7%
415
21st to endDay
25%18%33%17%6%1
346
March1st to 10thDay
30%22%26%15%6%
420
11th to 20thDay
25%25%24%16%9%1
420
21st to endDay
27%25%25%19%4
462
April1st to 10thDay
23%22%29%17%8%1
420
11th to 20thDay
24%26%28%14%6%1
412
21st to endDay
19%21%31%19%7%3
420
May1st to 10thDay
19%22%31%18%7%3
423
11th to 20thDay
20%19%32%19%7%4
448
21st to endDay
18%14%28%23%12%5%
485
June1st to 10thDay
11%19%33%24%8%5%
450
11th to 20thDay
15%18%35%20%8%4
450
21st to endDay
6%14%39%25%9%6%
450
July1st to 10thDay
213%43%26%13%3
446
11th to 20thDay
310%38%29%16%4
444
21st to endDay
49%36%33%14%5%
487
August1st to 10thDay
7%13%30%32%13%4
447
11th to 20thDay
5%11%35%31%14%5%
437
21st to endDay
310%40%30%13%3
495
September1st to 10thDay
411%39%28%17%2
450
11th to 20thDay
9%14%32%30%11%3
450
21st to endDay
9%14%36%30%10%2
450
October1st to 10thDay
10%20%26%27%16%1
450
11th to 20thDay
12%12%25%33%15%3
450
21st to endDay
14%15%26%27%15%4
459
November1st to 10thDay
20%13%22%20%20%4
270
11th to 20thDay
15%11%28%26%14%6%
270
21st to endDay
16%15%26%25%13%5%
246
December1st to 10thDay
23%16%26%14%14%7%
180
11th to 20thDay
23%17%29%16%10%5%
180
21st to endDay
29%8%27%21%13%2
198
January1st to 10thNight
15%10%27%23%17%8%
760
11th to 20thNight
12%9%25%33%14%6%
724
21st to endNight
11%9%28%28%18%7%
792
February1st to 10thNight
12%9%28%30%18%4
720
11th to 20thNight
12%13%25%26%19%5%
704
21st to endNight
17%13%23%30%13%3
592
March1st to 10thNight
14%17%27%25%13%4
720
11th to 20thNight
12%14%26%23%20%4
720
21st to endNight
14%16%27%28%13%2
792
April1st to 10thNight
11%12%28%29%18%2
720
11th to 20thNight
14%15%24%26%16%5%
711
21st to endNight
11%12%25%28%19%5%
720
May1st to 10thNight
10%14%23%30%19%5%
626
11th to 20thNight
8%7%24%36%21%3
402
21st to endNight
9%5%22%33%29%2
389
June1st to 10thNight
8%6%23%37%24%3
360
11th to 20thNight
47%25%33%29%2
360
21st to endNight
3324%41%25%3
360
July1st to 10thNight
2321%45%26%3
350
11th to 20thNight
2226%41%27%1
348
21st to endNight
4219%36%33%7%
469
August1st to 10thNight
4217%41%30%5%
562
11th to 20thNight
3321%40%28%5%
712
21st to endNight
3322%41%27%4
792
September1st to 10thNight
2420%37%32%6%
720
11th to 20thNight
46%19%33%30%8%
720
21st to endNight
5%6%21%29%30%8%
720
October1st to 10thNight
9%7%19%36%23%7%
720
11th to 20thNight
10%5%15%39%26%6%
720
21st to endNight
8%8%19%30%22%13%
792
November1st to 10thNight
12%10%18%30%22%8%
740
11th to 20thNight
10%9%24%34%17%6%
760
21st to endNight
12%11%20%31%20%6%
760
December1st to 10thNight
15%9%23%33%14%5%
760
11th to 20thNight
14%12%24%31%13%6%
760
21st to endNight
15%13%29%27%13%3
836
Page generated at 2024-01-08 19:31:27. Version ac07

Copyright 2024 Attilla Danko


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