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 2005-11-05 to 2018-02-22.

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
55%
15693
24%
48925
21%
15659
60%
15659
32%
28243

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
45%
778
17%
2716
14%
776
52%
776
22%
1706
January16th to endNight
41%
832
21%
2707
19%
832
47%
832
22%
1756
February1st to 15thNight
43%
758
20%
2483
17%
757
50%
757
22%
1594
February16th to endNight
42%
660
19%
1997
15%
660
48%
660
21%
1360
March1st to 15thNight
39%
720
11%
2058
9%
720
42%
720
18%
1478
March16th to endNight
38%
768
15%
2061
10%
768
42%
768
21%
1434
April1st to 15thNight
37%
719
16%
1799
7%
719
41%
719
22%
1289
April16th to endNight
48%
720
20%
1800
9%
720
53%
720
36%
1116
May1st to 15thNight
51%
478
23%
1558
17%
478
58%
478
36%
814
May16th to endNight
56%
374
17%
1496
18%
374
60%
374
26%
837
June1st to 15thNight
61%
360
22%
1440
26%
360
68%
360
33%
706
June16th to endNight
76%
360
30%
1440
42%
360
81%
360
48%
576
July1st to 15thNight
89%
340
31%
1360
44%
340
90%
340
67%
450
July16th to endNight
89%
453
39%
1487
42%
425
91%
425
71%
535
August1st to 15thNight
87%
538
37%
1611
32%
535
88%
535
65%
696
August16th to endNight
85%
759
43%
1905
28%
759
86%
759
77%
872
September1st to 15thNight
84%
720
41%
1800
28%
720
86%
720
74%
843
September16th to endNight
73%
716
39%
1952
33%
716
78%
716
61%
915
October1st to 15thNight
61%
720
29%
2160
25%
720
70%
720
45%
1072
October16th to endNight
61%
768
31%
2304
30%
768
67%
768
39%
1259
November1st to 15thNight
51%
760
20%
2461
19%
760
57%
760
25%
1549
November16th to endNight
46%
780
18%
2688
17%
780
51%
780
23%
1659
December1st to 15thNight
44%
780
18%
2730
16%
780
50%
780
20%
1735
December16th to endNight
36%
832
20%
2912
15%
832
44%
832
17%
1992

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
48%35%423346%53%
49336
Night
47%36%5%24446%50%
49104
TransparencyDay
32%38%19%22%13%
49014
Night
33%49%19%20%12%
48926
SeeingDay
14%17%29%24%10%3
6261
Night
10%11%16%30%26%5%
15703

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
49%5%8%7%46%45%7%35%
1552
16th to endDay
6%13%49%5%3445%5%36%
1866
February1st to 15thDay
5%12%47%5%35%5%5%7%38%
1711
16th to endDay
5%16%9%9%5%34346%32%
1623
March1st to 15thDay
5%17%7%9%6%35%336%30%
1900
16th to endDay
6%17%5%7%425%45%7%31%
2163
April1st to 15thDay
7%16%5%8%6%45%447%30%
2149
16th to endDay
6%10%35%42435%5%47%
2160
May1st to 15thDay
5%7%24423348%52%
2388
16th to endDay
10%11%35%5%23336%45%
2615
June1st to 15thDay
7%7%24424335%52%
2520
16th to endDay
22221223474%
2520
July1st to 15thDay
11121233377%
2520
16th to endDay
11111112383%
2578
August1st to 15thDay
11111223477%
2340
16th to endDay
11121223282%
2296
September1st to 15thDay
111223245%74%
2160
16th to endDay
3313212338%66%
2006
October1st to 15thDay
5%424323236%61%
1800
16th to endDay
5%7%25%424346%52%
1920
November1st to 15thDay
8%7%35%6%5%5%45%8%38%
1726
16th to endDay
49%5%10%5%3445%7%39%
1599
December1st to 15thDay
5%11%410%5%35%45%6%36%
1560
16th to endDay
7%11%7%9%6%45%446%32%
1664
January1st to 15thNight
49%49%6%35%45%7%38%
2716
16th to endNight
411%5%9%5%34447%38%
2707
February1st to 15thNight
49%5%8%8%345%5%7%37%
2471
16th to endNight
5%14%6%8%6%3445%7%34%
1997
March1st to 15thNight
5%13%6%10%7%35%5%5%7%29%
2058
16th to endNight
413%49%4445%6%7%34%
2061
April1st to 15thNight
5%14%6%7%7%44447%33%
1799
16th to endNight
5%9%45%42345%8%47%
1800
May1st to 15thNight
5%5%13424447%56%
1558
16th to endNight
6%7%35%5%34347%47%
1496
June1st to 15thNight
6%6%2341335%7%56%
1440
16th to endNight
222422223372%
1440
July1st to 15thNight
1221112381%
1440
16th to endNight
1111111284%
1589
August1st to 15thNight
11221222378%
1620
16th to endNight
1111121483%
1905
September1st to 15thNight
111111122480%
1800
16th to endNight
113212236%72%
1952
October1st to 15thNight
5%413313335%64%
2160
16th to endNight
35%15%43445%6%54%
2304
November1st to 15thNight
7%6%36%6%46%6%6%6%40%
2461
16th to endNight
48%48%5%3447%7%38%
2688
December1st to 15thNight
5%8%411%6%3445%7%38%
2730
16th to endNight
6%13%5%9%7%45%5%47%30%
2912

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
44%6%10%19%14%4
1552
16th to endDay
46%5%7%16%13%9%
1866
February1st to 15thDay
42%411%21%15%3
1711
16th to endDay
52%311%21%8%1
1623
March1st to 15thDay
54%48%16%12%4
1900
16th to endDay
49%5%15%17%9%3
2163
April1st to 15thDay
51%410%19%13%
2149
16th to endDay
37%313%26%15%3
2160
May1st to 15thDay
28%311%29%21%4
2388
16th to endDay
40%310%25%16%3
2619
June1st to 15thDay
33%39%19%25%9%
2520
16th to endDay
14%2421%39%17%
2520
July1st to 15thDay
11%2412%33%35%
2371
16th to endDay
9%1212%27%46%
2417
August1st to 15thDay
11%2318%27%35%
2324
16th to endDay
9%1216%36%34%
2296
September1st to 15thDay
12%2313%36%31%
2160
16th to endDay
17%37%26%30%15%
2006
October1st to 15thDay
24%36%23%28%13%
1800
16th to endDay
31%49%19%22%12%
1920
November1st to 15thDay
41%411%21%12%7%
1726
16th to endDay
42%411%20%17%4
1599
December1st to 15thDay
45%5%8%18%18%3
1560
16th to endDay
50%39%14%16%5%
1664
January1st to 15thNight
42%5%14%18%15%4
2716
16th to endNight
44%48%15%16%10%
2707
February1st to 15thNight
43%410%20%15%5%
2483
16th to endNight
48%311%20%13%3
1997
March1st to 15thNight
51%5%12%13%11%5%
2058
16th to endNight
45%6%15%18%10%2
2061
April1st to 15thNight
48%5%12%22%9%1
1799
16th to endNight
32%416%27%16%3
1800
May1st to 15thNight
26%5%11%29%21%5%
1559
16th to endNight
35%414%26%14%3
1496
June1st to 15thNight
26%5%11%24%24%7%
1440
16th to endNight
17%25%20%37%16%
1440
July1st to 15thNight
9%1414%30%40%
1360
16th to endNight
8%1310%26%50%
1487
August1st to 15thNight
12%2315%30%35%
1611
16th to endNight
8%1215%35%36%
1905
September1st to 15thNight
9%2313%36%35%
1800
16th to endNight
14%27%25%31%18%
1952
October1st to 15thNight
21%27%24%28%15%
2160
16th to endNight
26%5%10%23%22%12%
2304
November1st to 15thNight
39%6%13%21%13%5%
2461
16th to endNight
40%5%10%21%15%6%
2688
December1st to 15thNight
44%48%16%19%6%
2730
16th to endNight
51%47%13%17%5%
2912

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
22%21%30%21%32
90
16th to endDay
21%20%28%17%11%1
298
February1st to 15thDay
23%19%24%24%7%
281
16th to endDay
24%21%26%21%6%
260
March1st to 15thDay
30%25%22%12%7%1
270
16th to endDay
25%30%24%15%4
288
April1st to 15thDay
26%24%26%17%41
269
16th to endDay
22%24%31%15%5%
270
May1st to 15thDay
15%20%38%18%5%1
288
16th to endDay
23%12%25%22%11%3
330
June1st to 15thDay
18%15%29%22%10%1
315
16th to endDay
416%33%27%13%4
315
July1st to 15thDay
36%37%34%12%5%
305
16th to endDay
19%34%36%11%7%
327
August1st to 15thDay
39%33%34%8%9%
315
16th to endDay
110%33%30%17%6%
332
September1st to 15thDay
110%30%35%19%2
315
16th to endDay
9%13%31%30%13%1
315
October1st to 15thDay
11%19%31%23%12%1
315
16th to endDay
19%17%21%26%13%2
336
November1st to 15thDay
19%11%21%22%23%
142
16th to endDay
9%26%31%22%9%2
99
December1st to 15thDay
18%24%20%12%13%11%
90
16th to endDay
13%15%21%26%20%2
96
January1st to 15thNight
10%13%23%32%16%4
780
16th to endNight
13%14%23%25%17%4
832
February1st to 15thNight
14%15%18%32%17%2
764
16th to endNight
17%14%18%31%15%3
660
March1st to 15thNight
17%17%18%25%15%4
720
16th to endNight
15%21%18%24%16%2
768
April1st to 15thNight
13%17%22%30%14%1
719
16th to endNight
12%13%20%30%18%5%
720
May1st to 15thNight
9%8%24%31%21%3
479
16th to endNight
11%8%16%27%33%3
375
June1st to 15thNight
10%6%18%30%31%3
360
16th to endNight
35%10%35%42%3
360
July1st to 15thNight
1327%62%3
340
16th to endNight
15%30%55%7%
453
August1st to 15thNight
2327%55%9%
538
16th to endNight
118%37%44%6%
759
September1st to 15thNight
139%32%43%9%
720
16th to endNight
46%11%32%33%11%
716
October1st to 15thNight
8%10%14%32%27%6%
720
16th to endNight
8%9%14%28%29%9%
768
November1st to 15thNight
11%10%19%33%19%5%
760
16th to endNight
11%17%19%27%18%5%
780
December1st to 15thNight
12%15%21%27%18%4
780
16th to endNight
18%16%21%28%13%1
832
Page generated at 2018-02-23 08:21:35. Version ac04

Copyright 2018 A. Danko


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