Truchas
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Truchas clear sky chart from 2005-11-06 to 2024-02-15.

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%
24376
27%
79691
18%
24275
61%
24275
34%
43990

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
49%
861
24%
4217
20%
844
61%
844
23%
2397
January11th to 20thNight
47%
757
24%
4040
24%
740
59%
740
19%
2399
January21st to endNight
48%
827
20%
4297
22%
814
59%
814
21%
2370
February1st to 10thNight
41%
760
27%
2437
19%
760
53%
760
34%
1359
February11th to 20thNight
36%
720
27%
2152
15%
718
48%
718
32%
1280
February21st to endNight
31%
592
33%
1776
15%
592
49%
592
32%
1037
March1st to 10thNight
36%
720
29%
2098
13%
720
50%
720
33%
1225
March11th to 20thNight
44%
720
28%
1980
15%
720
53%
720
35%
1180
March21st to endNight
35%
702
29%
2088
13%
702
50%
702
31%
1199
April1st to 10thNight
30%
540
31%
1800
13%
540
52%
540
34%
908
April11th to 20thNight
34%
533
28%
1777
15%
533
52%
533
29%
970
April21st to endNight
33%
540
28%
1800
13%
540
55%
540
30%
984
May1st to 10thNight
40%
540
28%
1800
18%
540
57%
540
36%
905
May11th to 20thNight
44%
531
22%
1622
14%
531
55%
531
31%
944
May21st to endNight
44%
584
31%
1552
14%
582
59%
582
43%
823
June1st to 10thNight
55%
540
27%
1440
15%
540
64%
540
46%
780
June11th to 20thNight
56%
540
32%
1440
21%
540
65%
540
54%
728
June21st to endNight
61%
540
25%
1440
18%
540
67%
540
43%
819
July1st to 10thNight
70%
525
19%
1400
16%
525
71%
525
33%
893
July11th to 20thNight
78%
522
17%
1519
15%
522
79%
522
35%
883
July21st to endNight
74%
591
11%
1674
10%
558
74%
558
26%
1072
August1st to 10thNight
78%
537
13%
1663
12%
534
79%
534
31%
992
August11th to 20thNight
69%
534
18%
1778
18%
534
72%
534
26%
1099
August21st to endNight
75%
594
23%
1980
24%
594
78%
594
33%
1101
September1st to 10thNight
69%
540
28%
1800
26%
540
75%
540
36%
965
September11th to 20thNight
73%
540
36%
1800
33%
540
80%
540
43%
887
September21st to endNight
61%
556
33%
1986
28%
556
70%
556
43%
921
October1st to 10thNight
54%
720
30%
2160
19%
720
63%
720
40%
1149
October11th to 20thNight
57%
720
41%
2160
21%
720
72%
720
56%
979
October21st to endNight
56%
792
38%
2376
22%
792
67%
792
47%
1164
November1st to 10thNight
58%
820
38%
2300
20%
820
70%
820
55%
1087
November11th to 20thNight
57%
950
38%
2470
20%
950
66%
950
56%
1251
November21st to endNight
49%
950
32%
2470
18%
950
57%
950
41%
1444
December1st to 10thNight
47%
950
30%
2622
17%
950
56%
950
39%
1500
December11th to 20thNight
44%
948
25%
3119
17%
948
51%
948
28%
1890
December21st to endNight
39%
1040
17%
4658
15%
1026
48%
1026
23%
2406

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
45%25%4345%6%7%54%
78523
Night
47%35%43445%7%56%
80617
TransparencyDay
26%9%9%22%24%9%
78242
Night
26%8%9%22%24%9%
80420
SeeingDay
9%18%28%28%14%3
14153
Night
7%11%26%37%17%2
24404

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
26%5%8%5%3445%6%53%
2701
11th to 20thDay
311%45%423445%55%
2860
21st to endDay
38%38%7%3445%5%51%
3146
February1st to 10thDay
210%46%434446%52%
1740
11th to 20thDay
28%46%5%3445%7%53%
1789
21st to endDay
310%45%433448%52%
1480
March1st to 10thDay
49%34435%45%8%52%
1859
11th to 20thDay
48%46%43445%6%52%
1980
21st to endDay
48%36%4345%5%5%53%
2267
April1st to 10thDay
47%234235%5%8%57%
2160
11th to 20thDay
48%25%6%24346%56%
2131
21st to endDay
5%7%2433445%8%56%
2160
May1st to 10thDay
45%1443446%7%59%
2160
11th to 20thDay
5%5%24436%5%6%7%52%
2269
21st to endDay
33133345%5%7%62%
2724
June1st to 10thDay
2212335%6%7%9%59%
2520
11th to 20thDay
221222446%7%68%
2520
21st to endDay
5%3145%35%5%7%9%53%
2520
July1st to 10thDay
3425%6%46%7%9%10%43%
2520
11th to 20thDay
3425%6%47%8%10%12%41%
2386
21st to endDay
6%437%8%5%9%9%10%11%30%
2545
August1st to 10thDay
5%425%7%48%7%8%9%40%
2266
11th to 20thDay
44346%47%8%8%10%44%
2123
21st to endDay
5%4245%37%6%9%10%44%
2376
September1st to 10thDay
5%5%25%5%35%6%6%8%48%
2160
11th to 20thDay
5%424435%5%5%6%57%
2160
21st to endDay
32133235%5%5%66%
1969
October1st to 10thDay
6%425%5%345%5%6%56%
1800
11th to 20thDay
422222223474%
1800
21st to endDay
6%32332233470%
1980
November1st to 10thDay
2412323347%69%
1758
11th to 20thDay
441221335%6%69%
1710
21st to endDay
39%34323345%60%
1710
December1st to 10thDay
5%7%34322347%60%
1554
11th to 20thDay
37%36%6%3445%8%50%
1926
21st to endDay
38%35%423346%60%
2794
January1st to 10thNight
18%5%11%6%33435%50%
4283
11th to 20thNight
314%6%6%6%35%33447%
4110
21st to endNight
29%5%6%5%3446%6%50%
4521
February1st to 10thNight
211%47%423246%56%
2437
11th to 20thNight
411%35%433446%53%
2152
21st to endNight
411%36%332345%56%
1776
March1st to 10thNight
410%35%433347%55%
2098
11th to 20thNight
6%9%34424436%56%
1980
21st to endNight
6%8%34423336%56%
2088
April1st to 10thNight
45%2333445%7%60%
1800
11th to 20thNight
310%35%32445%5%56%
1777
21st to endNight
7%8%2432434458%
1800
May1st to 10thNight
5%42332445%6%62%
1800
11th to 20thNight
7%6%34425%46%8%51%
1622
21st to endNight
331233445%6%66%
1552
June1st to 10thNight
1213435%6%7%9%59%
1440
11th to 20thNight
31123235%5%6%68%
1440
21st to endNight
43235%35%6%6%9%56%
1440
July1st to 10thNight
4315%6%37%7%8%10%46%
1440
11th to 20thNight
22245%47%7%9%11%46%
1570
21st to endNight
4325%5%5%7%9%12%13%34%
1773
August1st to 10thNight
33135%46%7%9%14%45%
1672
11th to 20thNight
45%26%7%47%8%9%11%38%
1778
21st to endNight
32245%36%7%9%11%48%
1980
September1st to 10thNight
5%324436%6%7%9%52%
1800
11th to 20thNight
43144236%6%8%60%
1800
21st to endNight
6%313323446%66%
1986
October1st to 10thNight
6%31342445%6%63%
2160
11th to 20thNight
3212222335%76%
2160
21st to endNight
441322335%6%66%
2376
November1st to 10thNight
3212213346%73%
2300
11th to 20thNight
3312222246%72%
2470
21st to endNight
48%34423346%59%
2470
December1st to 10thNight
49%34323345%60%
2622
11th to 20thNight
48%37%5%3446%8%48%
3271
21st to endNight
310%37%423335%57%
4873

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
25%14%7%28%22%5%
2702
11th to 20thDay
24%12%11%32%17%4
2860
21st to endDay
34%8%7%23%22%6%
3146
February1st to 10thDay
32%8%9%21%23%8%
1740
11th to 20thDay
31%5%6%25%24%9%
1799
21st to endDay
31%7%5%17%28%12%
1480
March1st to 10thDay
30%8%6%20%26%10%
1859
11th to 20thDay
32%7%422%29%6%
1980
21st to endDay
31%8%6%24%26%5%
2267
April1st to 10thDay
24%8%6%25%26%11%
2160
11th to 20thDay
29%8%420%30%9%
2134
21st to endDay
26%9%5%25%28%6%
2160
May1st to 10thDay
23%7%6%23%31%10%
2160
11th to 20thDay
29%9%11%22%23%7%
2273
21st to endDay
19%7%8%21%28%17%
2724
June1st to 10thDay
17%8%12%24%24%15%
2520
11th to 20thDay
14%7%6%17%27%29%
2520
21st to endDay
26%8%9%20%23%15%
2520
July1st to 10thDay
31%13%15%15%17%10%
2451
11th to 20thDay
29%13%20%21%11%6%
2314
21st to endDay
40%17%22%17%41
2404
August1st to 10thDay
35%15%15%16%13%6%
2251
11th to 20thDay
30%13%14%20%17%5%
2123
21st to endDay
29%14%13%24%16%4
2376
September1st to 10thDay
30%12%11%22%19%6%
2160
11th to 20thDay
26%8%9%19%26%12%
2160
21st to endDay
17%9%6%25%33%9%
1969
October1st to 10thDay
28%9%6%21%25%12%
1800
11th to 20thDay
15%4319%43%16%
1800
21st to endDay
20%5%6%25%36%9%
1980
November1st to 10thDay
16%6%8%25%35%11%
1758
11th to 20thDay
17%5%7%27%34%9%
1710
21st to endDay
26%6%5%22%28%14%
1710
December1st to 10thDay
23%8%12%27%23%7%
1554
11th to 20thDay
32%7%8%18%27%8%
1924
21st to endDay
25%6%7%20%28%14%
2794
January1st to 10thNight
34%9%8%21%22%7%
4283
11th to 20thNight
27%20%7%26%17%4
4110
21st to endNight
32%9%7%24%21%7%
4521
February1st to 10thNight
30%5%10%23%22%9%
2437
11th to 20thNight
32%7%7%25%20%9%
2152
21st to endNight
31%6%320%29%11%
1776
March1st to 10thNight
29%7%5%24%25%10%
2098
11th to 20thNight
28%8%6%24%27%6%
1980
21st to endNight
29%8%7%22%29%6%
2088
April1st to 10thNight
23%6%7%27%27%10%
1800
11th to 20thNight
28%7%5%22%28%10%
1777
21st to endNight
28%7%7%24%27%8%
1800
May1st to 10thNight
23%6%8%21%32%10%
1800
11th to 20thNight
31%7%11%21%22%8%
1623
21st to endNight
19%7%9%21%28%15%
1552
June1st to 10thNight
21%7%13%22%21%15%
1440
11th to 20thNight
16%5%6%16%28%29%
1440
21st to endNight
23%8%11%18%23%17%
1440
July1st to 10thNight
30%12%15%16%12%14%
1400
11th to 20thNight
25%13%22%22%10%9%
1519
21st to endNight
32%15%31%18%4
1674
August1st to 10thNight
25%15%24%15%12%9%
1663
11th to 20thNight
34%12%18%20%12%4
1778
21st to endNight
25%11%19%25%15%4
1980
September1st to 10thNight
26%8%16%26%16%8%
1800
11th to 20thNight
20%7%14%18%26%14%
1800
21st to endNight
19%6%9%23%33%10%
1986
October1st to 10thNight
23%6%10%22%26%12%
2160
11th to 20thNight
12%5%421%42%15%
2160
21st to endNight
18%6%6%27%35%9%
2376
November1st to 10thNight
13%5%7%26%38%10%
2300
11th to 20thNight
16%46%30%34%10%
2470
21st to endNight
26%6%5%21%29%14%
2470
December1st to 10thNight
27%6%9%28%24%6%
2622
11th to 20thNight
32%8%7%19%24%10%
3272
21st to endNight
30%7%7%19%27%10%
4873

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
11%21%35%23%9%1
270
11th to 20thDay
18%21%26%28%6%2
270
21st to endDay
5%25%35%24%10%1
297
February1st to 10thDay
10%30%33%23%5%
270
11th to 20thDay
11%29%38%18%4
252
21st to endDay
19%36%26%17%3
198
March1st to 10thDay
14%27%31%23%4
299
11th to 20thDay
15%30%26%21%6%1
420
21st to endDay
17%39%27%13%3
462
April1st to 10thDay
13%30%36%15%41
420
11th to 20thDay
17%35%32%11%4
412
21st to endDay
15%37%33%13%2
420
May1st to 10thDay
7%34%41%13%31
423
11th to 20thDay
7%20%36%26%9%2
535
21st to endDay
7%21%32%28%11%1
679
June1st to 10thDay
310%31%37%18%2
630
11th to 20thDay
412%35%30%17%3
630
21st to endDay
6%8%27%34%21%5%
630
July1st to 10thDay
5%418%40%29%5%
621
11th to 20thDay
5%211%42%31%10%
487
21st to endDay
5%49%34%40%8%
487
August1st to 10thDay
5%6%18%38%26%6%
447
11th to 20thDay
36%19%42%24%5%
437
21st to endDay
6%420%40%23%7%
495
September1st to 10thDay
6%5%23%38%23%4
450
11th to 20thDay
5%8%32%38%13%4
450
21st to endDay
314%28%35%16%5%
278
October1st to 10thDay
6%25%21%29%13%5%
270
11th to 20thDay
8%16%31%29%12%4
270
21st to endDay
14%15%28%28%12%3
297
November1st to 10thDay
8%20%33%29%9%1
270
11th to 20thDay
7%15%34%30%14%1
270
21st to endDay
9%25%31%21%13%1
270
December1st to 10thDay
13%20%32%24%10%1
270
11th to 20thDay
10%20%36%28%6%1
270
21st to endDay
16%28%32%20%22
297
January1st to 10thNight
7%11%27%40%12%2
868
11th to 20thNight
11%10%26%38%11%3
760
21st to endNight
6%14%28%38%12%2
836
February1st to 10thNight
9%14%32%35%9%1
760
11th to 20thNight
9%16%36%30%8%1
722
21st to endNight
14%17%36%29%3
592
March1st to 10thNight
9%21%32%30%7%1
720
11th to 20thNight
10%15%28%32%15%1
720
21st to endNight
11%18%33%32%6%
702
April1st to 10thNight
9%17%42%27%5%
540
11th to 20thNight
10%21%32%29%7%1
533
21st to endNight
11%19%34%29%8%
540
May1st to 10thNight
6%15%36%33%10%1
540
11th to 20thNight
10%12%28%33%15%1
531
21st to endNight
6%13%32%36%12%
584
June1st to 10thNight
25%29%43%20%1
540
11th to 20thNight
28%30%43%16%1
540
21st to endNight
3325%42%25%2
540
July1st to 10thNight
428%47%34%4
525
11th to 20thNight
317%41%42%6%
522
21st to endNight
5%37%31%45%10%
591
August1st to 10thNight
328%36%41%11%
537
11th to 20thNight
4312%44%33%4
534
21st to endNight
2310%41%37%7%
594
September1st to 10thNight
6%217%42%30%4
540
11th to 20thNight
4315%48%27%3
540
21st to endNight
5%8%21%42%22%1
556
October1st to 10thNight
6%10%24%43%16%2
720
11th to 20thNight
5%9%27%39%18%3
720
21st to endNight
7%10%23%35%19%4
792
November1st to 10thNight
5%11%24%41%17%2
820
11th to 20thNight
412%25%42%14%3
950
21st to endNight
8%15%24%33%17%2
950
December1st to 10thNight
9%13%29%38%9%1
950
11th to 20thNight
11%15%27%37%10%1
950
21st to endNight
10%16%30%35%7%1
1045
Page generated at 2024-02-12 04:35:32. Version ac07

Copyright 2024 Attilla Danko


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