Lassen National Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lassen National Park clear sky chart from 2005-11-06 to 2024-03-28.

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%
23471
24%
80706
21%
23379
60%
23379
30%
46333

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
37%
753
16%
4332
13%
736
45%
736
13%
2491
January11th to 20thNight
38%
753
17%
4245
14%
740
48%
740
13%
2732
January21st to endNight
37%
830
14%
4462
19%
814
46%
814
12%
3187
February1st to 10thNight
40%
760
22%
2470
16%
760
49%
760
24%
1529
February11th to 20thNight
39%
741
21%
2337
16%
740
49%
740
23%
1478
February21st to endNight
38%
628
18%
1884
13%
628
45%
628
22%
1252
March1st to 10thNight
32%
760
12%
2214
8%
760
37%
760
16%
1600
March11th to 20thNight
44%
760
19%
2090
14%
760
49%
760
24%
1401
March21st to endNight
33%
820
13%
2178
6%
820
39%
820
21%
1525
April1st to 10thNight
39%
720
19%
1800
9%
720
43%
720
26%
1243
April11th to 20thNight
41%
711
21%
1779
9%
711
47%
711
32%
1141
April21st to endNight
50%
720
20%
1800
9%
720
54%
720
38%
1113
May1st to 10thNight
46%
540
26%
1620
14%
540
55%
540
36%
882
May11th to 20thNight
56%
354
23%
1416
24%
354
62%
354
27%
761
May21st to endNight
54%
388
19%
1552
19%
388
60%
388
25%
867
June1st to 10thNight
61%
360
22%
1440
25%
360
67%
360
32%
714
June11th to 20thNight
62%
360
30%
1440
34%
360
73%
360
43%
598
June21st to endNight
76%
360
31%
1440
42%
360
81%
360
51%
556
July1st to 10thNight
88%
350
33%
1400
46%
350
90%
350
70%
449
July11th to 20thNight
87%
348
39%
1392
50%
348
91%
348
70%
444
July21st to endNight
90%
510
39%
1598
41%
482
91%
482
69%
616
August1st to 10thNight
86%
537
37%
1602
32%
534
87%
534
63%
702
August11th to 20thNight
85%
614
40%
1682
27%
614
87%
614
71%
745
August21st to endNight
86%
792
43%
1980
27%
792
87%
792
79%
895
September1st to 10thNight
81%
720
44%
1800
27%
720
85%
720
77%
823
September11th to 20thNight
76%
720
42%
1800
31%
720
79%
720
65%
891
September21st to endNight
71%
720
38%
2027
32%
720
78%
720
61%
926
October1st to 10thNight
61%
720
29%
2160
25%
720
70%
720
48%
1054
October11th to 20thNight
64%
720
36%
2160
33%
720
73%
720
49%
1046
October21st to endNight
59%
792
34%
2376
29%
792
68%
792
43%
1229
November1st to 10thNight
52%
740
24%
2391
22%
740
58%
740
27%
1452
November11th to 20thNight
47%
760
21%
2503
16%
760
56%
760
26%
1502
November21st to endNight
45%
760
23%
2660
20%
760
54%
760
28%
1492
December1st to 10thNight
43%
760
22%
2660
17%
760
51%
760
24%
1601
December11th to 20thNight
39%
760
17%
3222
15%
759
46%
759
14%
2309
December21st to endNight
33%
830
13%
4794
13%
817
42%
817
10%
3087

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
47%35%5%34446%54%
78836
Night
37%36%6%35%5%5%7%50%
81187
TransparencyDay
31%49%19%22%15%
78546
Night
34%5%10%19%20%13%
80998
SeeingDay
14%17%29%25%13%3
14142
Night
10%12%19%32%23%4
23501

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
312%7%10%8%45%5%5%6%35%
2539
11th to 20thDay
311%411%9%5%6%5%5%7%34%
2677
21st to endDay
414%6%10%8%45%5%5%7%34%
3146
February1st to 10thDay
49%5%7%6%45%5%6%6%41%
1710
11th to 20thDay
212%7%8%6%345%5%8%40%
1731
21st to endDay
412%7%8%7%45%5%47%38%
1570
March1st to 10thDay
415%6%11%8%45%5%47%32%
1964
11th to 20thDay
5%13%7%7%5%35%5%5%9%37%
2090
21st to endDay
5%15%5%7%7%46%6%47%33%
2333
April1st to 10thDay
6%12%47%7%46%5%6%9%35%
2160
11th to 20thDay
6%12%47%4345%5%7%43%
2129
21st to endDay
6%10%34435%35%8%50%
2160
May1st to 10thDay
5%8%245%33448%54%
2333
11th to 20thDay
5%8%35%5%3435%8%51%
2477
21st to endDay
10%10%35%5%25%447%45%
2723
June1st to 10thDay
6%6%25%5%35%5%5%6%52%
2520
11th to 20thDay
3413223446%68%
2520
21st to endDay
211232333476%
2520
July1st to 10thDay
1111222335%79%
2520
11th to 20thDay
111221222383%
2520
21st to endDay
1112213335%78%
2623
August1st to 10thDay
221221334476%
2328
11th to 20thDay
111122223481%
2216
21st to endDay
11111232385%
2376
September1st to 10thDay
11122323482%
2160
11th to 20thDay
331342345%8%66%
2160
21st to endDay
3312312346%71%
1931
October1st to 10thDay
5%5%14423335%65%
1800
11th to 20thDay
4423424446%63%
1800
21st to endDay
46%2443435%7%59%
1980
November1st to 10thDay
7%8%25%6%35%5%5%9%44%
1686
11th to 20thDay
47%35%6%47%7%8%8%42%
1672
21st to endDay
36%47%435%6%6%8%48%
1520
December1st to 10thDay
49%37%6%47%6%5%7%41%
1520
11th to 20thDay
5%14%6%11%8%6%5%6%6%6%26%
1928
21st to endDay
311%5%9%7%45%6%7%9%35%
2794
January1st to 10thNight
27%410%8%5%7%7%8%8%34%
4406
11th to 20thNight
311%49%9%45%6%6%8%36%
4282
21st to endNight
413%7%12%9%5%6%6%5%6%29%
4521
February1st to 10thNight
47%38%7%45%5%6%9%41%
2470
11th to 20thNight
28%5%9%8%36%5%5%7%41%
2335
21st to endNight
411%5%9%6%35%5%5%7%39%
1884
March1st to 10thNight
412%5%10%8%47%6%5%7%34%
2214
11th to 20thNight
310%5%7%7%45%5%6%10%37%
2090
21st to endNight
312%5%8%6%36%5%6%8%37%
2178
April1st to 10thNight
411%5%6%7%5%46%5%7%40%
1800
11th to 20thNight
410%46%5%2446%9%46%
1779
21st to endNight
410%4443445%8%51%
1800
May1st to 10thNight
5%7%24424346%58%
1620
11th to 20thNight
5%7%245%46%5%6%6%50%
1416
21st to endNight
10%7%345%35%447%48%
1552
June1st to 10thNight
5%7%3443436%8%54%
1440
11th to 20thNight
4323323347%68%
1440
21st to endNight
221232333376%
1440
July1st to 10thNight
11221223483%
1440
11th to 20thNight
121121222286%
1440
21st to endNight
111221223382%
1692
August1st to 10thNight
221221233477%
1611
11th to 20thNight
111221133480%
1682
21st to endNight
11121212386%
1980
September1st to 10thNight
211111122484%
1800
11th to 20thNight
2112212436%75%
1800
21st to endNight
2212223346%72%
2027
October1st to 10thNight
5%42232233468%
2160
11th to 20thNight
3414323346%65%
2160
21st to endNight
342343445%8%60%
2376
November1st to 10thNight
6%7%47%6%45%5%6%7%44%
2391
11th to 20thNight
46%36%6%36%7%8%8%42%
2503
21st to endNight
26%5%6%5%346%7%9%47%
2660
December1st to 10thNight
47%36%6%35%6%6%9%44%
2660
11th to 20thNight
5%13%5%11%9%5%7%7%5%8%28%
3276
21st to endNight
412%5%9%8%5%7%6%5%7%32%
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
49%6%12%19%12%2
2539
11th to 20thDay
50%6%13%13%12%6%
2677
21st to endDay
53%412%16%11%4
3146
February1st to 10thDay
42%6%11%21%13%8%
1710
11th to 20thDay
45%5%8%20%18%5%
1740
21st to endDay
46%6%10%20%13%5%
1570
March1st to 10thDay
53%6%8%17%12%4
1964
11th to 20thDay
46%411%17%18%4
2090
21st to endDay
50%6%12%19%10%3
2333
April1st to 10thDay
46%6%12%18%16%3
2160
11th to 20thDay
40%5%10%23%17%5%
2132
21st to endDay
33%5%14%28%16%3
2160
May1st to 10thDay
29%412%27%24%5%
2333
11th to 20thDay
32%5%10%28%20%5%
2480
21st to endDay
38%6%11%27%16%2
2724
June1st to 10thDay
32%410%26%24%5%
2520
11th to 20thDay
17%49%24%33%13%
2520
21st to endDay
12%3420%36%25%
2520
July1st to 10thDay
10%3413%31%39%
2451
11th to 20thDay
8%2413%29%44%
2445
21st to endDay
11%3211%25%47%
2477
August1st to 10thDay
13%3417%28%35%
2312
11th to 20thDay
8%3315%38%34%
2216
21st to endDay
7%2216%36%37%
2376
September1st to 10thDay
9%2210%32%44%
2160
11th to 20thDay
18%46%20%32%21%
2160
21st to endDay
16%36%22%32%21%
1931
October1st to 10thDay
23%36%21%30%17%
1800
11th to 20thDay
24%47%18%30%17%
1800
21st to endDay
26%49%20%24%17%
1980
November1st to 10thDay
38%49%18%17%12%
1686
11th to 20thDay
36%5%12%20%18%8%
1672
21st to endDay
35%410%20%22%9%
1520
December1st to 10thDay
43%6%8%18%20%6%
1520
11th to 20thDay
58%5%9%13%12%3
1928
21st to endDay
46%6%14%15%14%4
2794
January1st to 10thNight
42%6%17%21%11%3
4406
11th to 20thNight
48%6%12%12%15%7%
4282
21st to endNight
57%48%15%11%5%
4521
February1st to 10thNight
40%5%9%21%17%8%
2470
11th to 20thNight
41%5%10%19%19%6%
2337
21st to endNight
43%6%11%19%15%5%
1884
March1st to 10thNight
50%8%11%15%11%5%
2214
11th to 20thNight
42%6%11%18%18%5%
2090
21st to endNight
44%9%15%19%11%2
2178
April1st to 10thNight
42%7%12%22%12%4
1800
11th to 20thNight
36%5%14%23%17%6%
1779
21st to endNight
31%5%17%27%18%3
1800
May1st to 10thNight
27%6%11%29%25%3
1620
11th to 20thNight
33%5%14%29%15%5%
1416
21st to endNight
35%5%14%27%16%2
1552
June1st to 10thNight
28%5%12%30%21%3
1440
11th to 20thNight
17%5%10%26%33%10%
1440
21st to endNight
15%45%19%33%25%
1440
July1st to 10thNight
8%2414%30%42%
1400
11th to 20thNight
8%1412%26%49%
1392
21st to endNight
10%228%27%51%
1598
August1st to 10thNight
13%3414%30%35%
1602
11th to 20thNight
9%3215%34%37%
1682
21st to endNight
8%1314%34%40%
1980
September1st to 10thNight
7%229%32%47%
1800
11th to 20thNight
13%37%21%32%24%
1800
21st to endNight
14%27%23%32%22%
2027
October1st to 10thNight
21%27%20%30%20%
2160
11th to 20thNight
20%37%23%29%19%
2160
21st to endNight
22%5%10%22%25%15%
2376
November1st to 10thNight
38%6%11%17%18%10%
2391
11th to 20thNight
36%6%11%21%18%7%
2503
21st to endNight
34%5%10%22%20%11%
2660
December1st to 10thNight
39%6%9%16%21%9%
2660
11th to 20thNight
56%46%13%17%4
3276
21st to endNight
49%7%11%15%14%5%
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
32%21%23%16%7%1
180
11th to 20thDay
20%27%23%20%8%2
265
21st to endDay
18%21%29%18%12%1
407
February1st to 10thDay
24%21%27%18%9%1
370
11th to 20thDay
27%20%27%18%7%1
396
21st to endDay
20%24%29%22%5%
382
March1st to 10thDay
30%30%23%13%41
460
11th to 20thDay
25%19%27%18%9%2
460
21st to endDay
22%30%27%15%5%
491
April1st to 10thDay
21%26%28%19%5%1
420
11th to 20thDay
25%23%24%18%9%1
412
21st to endDay
18%20%30%20%10%2
420
May1st to 10thDay
15%22%33%20%9%2
423
11th to 20thDay
19%17%33%19%10%4
448
21st to endDay
18%17%24%26%13%4
485
June1st to 10thDay
11%18%27%25%15%4
450
11th to 20thDay
9%21%31%24%11%2
450
21st to endDay
312%31%33%16%5%
450
July1st to 10thDay
27%41%29%16%5%
446
11th to 20thDay
26%35%34%15%9%
444
21st to endDay
15%32%36%18%8%
487
August1st to 10thDay
38%27%36%17%9%
447
11th to 20thDay
19%29%32%19%10%
437
21st to endDay
28%30%35%19%5%
495
September1st to 10thDay
210%33%34%19%3
450
11th to 20thDay
6%14%29%29%19%3
450
21st to endDay
7%13%33%33%12%2
450
October1st to 10thDay
7%17%31%26%18%1
450
11th to 20thDay
13%15%23%29%18%1
450
21st to endDay
14%18%25%26%14%3
495
November1st to 10thDay
17%13%23%26%19%3
282
11th to 20thDay
11%17%27%23%19%4
252
21st to endDay
14%17%29%23%12%4
180
December1st to 10thDay
24%16%24%17%14%6%
180
11th to 20thDay
19%21%23%18%14%5%
180
21st to endDay
21%19%25%22%13%1
198
January1st to 10thNight
14%17%25%28%12%4
760
11th to 20thNight
13%18%25%29%13%3
760
21st to endNight
13%14%27%27%16%3
836
February1st to 10thNight
14%16%24%29%14%2
760
11th to 20thNight
13%17%22%30%15%3
744
21st to endNight
16%14%25%32%11%1
628
March1st to 10thNight
19%21%22%24%11%3
760
11th to 20thNight
16%16%19%26%21%3
760
21st to endNight
14%22%24%25%13%2
820
April1st to 10thNight
11%18%24%33%13%1
720
11th to 20thNight
13%16%24%29%14%3
711
21st to endNight
11%11%23%32%20%3
720
May1st to 10thNight
10%11%28%30%18%3
540
11th to 20thNight
10%8%18%34%26%4
354
21st to endNight
13%8%16%28%31%3
389
June1st to 10thNight
8%6%17%36%30%3
360
11th to 20thNight
411%19%34%29%3
360
21st to endNight
3412%41%38%3
360
July1st to 10thNight
117%40%49%3
350
11th to 20thNight
217%42%45%3
348
21st to endNight
2439%50%5%
510
August1st to 10thNight
316%34%50%7%
537
11th to 20thNight
128%41%42%6%
614
21st to endNight
218%41%44%4
792
September1st to 10thNight
2312%42%36%5%
720
11th to 20thNight
26%12%35%37%9%
720
21st to endNight
5%6%15%36%29%9%
720
October1st to 10thNight
7%9%17%34%28%5%
720
11th to 20thNight
9%8%15%33%30%5%
720
21st to endNight
8%12%17%31%24%7%
792
November1st to 10thNight
12%11%18%32%22%5%
740
11th to 20thNight
10%15%23%33%16%3
760
21st to endNight
8%16%24%30%18%4
760
December1st to 10thNight
13%16%23%29%16%3
760
11th to 20thNight
16%15%23%29%15%3
760
21st to endNight
19%18%25%28%9%1
836
Page generated at 2024-03-24 20:37:00. Version ac07

Copyright © 2024 Attilla Danko.


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