Velveeta Valley Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Velveeta Valley Observatory clear sky chart from 2005-11-06 to 2024-01-13.

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
36%
24660
17%
74683
10%
24605
43%
24605
23%
50096

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
23%
950
14%
2648
5%
946
31%
946
19%
1912
January11th to 20thNight
19%
915
12%
2561
4%
915
25%
915
15%
1976
January21st to endNight
21%
990
11%
2671
4%
990
27%
990
15%
2050
February1st to 10thNight
20%
900
12%
2340
3%
900
25%
900
18%
1750
February11th to 20thNight
23%
744
17%
2143
7%
744
31%
744
20%
1474
February21st to endNight
20%
592
17%
1776
5%
592
32%
592
18%
1236
March1st to 10thNight
25%
720
13%
2160
6%
720
31%
720
19%
1493
March11th to 20thNight
32%
626
19%
2066
10%
626
43%
626
22%
1325
March21st to endNight
25%
594
14%
2008
9%
594
32%
594
15%
1448
April1st to 10thNight
24%
540
15%
1800
8%
540
34%
540
19%
1210
April11th to 20thNight
30%
533
20%
1775
14%
533
41%
533
20%
1171
April21st to endNight
33%
540
15%
1756
8%
540
43%
540
21%
1181
May1st to 10thNight
35%
540
14%
1571
8%
540
41%
540
22%
1089
May11th to 20thNight
38%
531
18%
1417
10%
531
45%
531
26%
979
May21st to endNight
46%
584
16%
1551
8%
582
52%
582
29%
1022
June1st to 10thNight
55%
540
16%
1440
9%
540
59%
540
37%
883
June11th to 20thNight
51%
540
20%
1440
12%
540
57%
540
35%
910
June21st to endNight
52%
540
18%
1440
10%
540
56%
540
32%
925
July1st to 10thNight
71%
525
17%
1400
12%
525
72%
525
43%
820
July11th to 20thNight
64%
522
21%
1392
14%
522
67%
522
44%
804
July21st to endNight
66%
591
22%
1487
17%
558
69%
558
43%
862
August1st to 10thNight
70%
537
23%
1476
21%
534
72%
534
41%
850
August11th to 20thNight
68%
534
22%
1742
23%
534
71%
534
38%
942
August21st to endNight
66%
594
22%
1980
23%
594
71%
594
36%
1084
September1st to 10thNight
58%
540
25%
1800
24%
540
64%
540
33%
1003
September11th to 20thNight
57%
583
32%
1843
28%
583
64%
583
35%
1039
September21st to endNight
47%
720
24%
1980
14%
720
54%
720
32%
1208
October1st to 10thNight
45%
720
23%
2110
16%
720
51%
720
31%
1286
October11th to 20thNight
32%
720
22%
2160
10%
720
44%
720
24%
1389
October21st to endNight
29%
792
16%
2533
9%
792
37%
792
20%
1704
November1st to 10thNight
29%
740
26%
2406
15%
740
43%
740
28%
1418
November11th to 20thNight
24%
760
18%
2470
9%
760
36%
760
18%
1667
November21st to endNight
25%
926
17%
2636
8%
926
34%
926
21%
1823
December1st to 10thNight
21%
950
12%
2660
4%
950
28%
950
17%
1965
December11th to 20thNight
22%
949
14%
3205
4%
948
31%
948
14%
2295
December21st to endNight
16%
1038
6%
4840
3%
1026
22%
1026
7%
3903

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
14%8%46%5%35%5%5%7%37%
74784
Night
14%8%46%5%3445%7%40%
74984
TransparencyDay
46%6%13%22%12%1
74485
Night
45%6%12%22%14%2
74804
SeeingDay
17%10%29%25%14%5%
14681
Night
17%9%31%30%12%1
24671

By Month

Percentage Cloud Cover SE (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
13%11%6%9%6%35%5%5%7%29%
1517
11th to 20thDay
14%14%7%12%6%345%6%6%23%
1461
21st to endDay
14%15%7%12%6%3445%5%24%
1683
February1st to 10thDay
13%13%7%7%7%36%5%47%28%
1620
11th to 20thDay
14%9%48%7%44447%35%
1703
21st to endDay
15%14%5%8%7%34346%31%
1480
March1st to 10thDay
15%11%5%8%5%44448%33%
1800
11th to 20thDay
13%9%38%5%2435%8%39%
1908
21st to endDay
20%10%47%6%45%5%5%6%27%
2346
April1st to 10thDay
18%9%5%7%6%35%45%6%32%
2160
11th to 20thDay
17%8%37%6%45%45%7%34%
2134
21st to endDay
20%10%36%6%3445%6%33%
2204
May1st to 10thDay
18%8%47%6%35%5%6%7%30%
2386
11th to 20thDay
20%7%35%5%35%5%6%7%35%
2479
21st to endDay
15%7%35%6%45%5%6%7%37%
2725
June1st to 10thDay
11%425%6%46%5%7%7%43%
2520
11th to 20thDay
11%5%245%35%5%5%10%46%
2520
21st to endDay
12%6%36%5%35%6%7%9%38%
2520
July1st to 10thDay
8%4245%35%5%7%9%47%
2520
11th to 20thDay
8%424436%6%7%10%46%
2520
21st to endDay
7%5%25%5%45%5%7%10%45%
2743
August1st to 10thDay
7%425%6%36%6%8%11%42%
2451
11th to 20thDay
11%425%5%35%5%6%8%46%
2156
21st to endDay
11%5%245%3446%7%49%
2376
September1st to 10thDay
14%6%245%35%447%45%
2160
11th to 20thDay
13%41342446%7%52%
2098
21st to endDay
12%6%36%435%45%7%45%
1980
October1st to 10thDay
15%7%25%424446%48%
1846
11th to 20thDay
21%8%35%6%4345%6%36%
1800
21st to endDay
20%9%35%5%33346%38%
1823
November1st to 10thDay
12%8%45%5%2445%6%45%
1672
11th to 20thDay
14%11%5%6%6%35%45%6%33%
1710
21st to endDay
16%13%37%423446%37%
1542
December1st to 10thDay
15%12%49%6%345%46%32%
1520
11th to 20thDay
14%13%49%6%35%5%5%6%30%
1918
21st to endDay
21%19%10%11%7%3443415%
2783
January1st to 10thNight
13%12%5%8%6%34445%36%
2648
11th to 20thNight
15%13%7%10%7%34345%28%
2561
21st to endNight
16%11%6%10%7%4445%7%26%
2671
February1st to 10thNight
14%13%7%8%6%44345%33%
2340
11th to 20thNight
13%10%47%6%35%45%6%38%
2142
21st to endNight
19%11%46%5%24446%35%
1776
March1st to 10thNight
17%9%46%6%345%6%5%36%
2160
11th to 20thNight
12%8%36%5%35%5%5%7%42%
2066
21st to endNight
21%10%47%6%34447%31%
2008
April1st to 10thNight
17%9%45%5%35%45%6%39%
1800
11th to 20thNight
19%8%37%5%23346%39%
1775
21st to endNight
17%8%36%5%35%5%6%8%35%
1756
May1st to 10thNight
15%8%36%6%35%5%6%8%37%
1571
11th to 20thNight
18%7%26%4345%6%8%37%
1416
21st to endNight
12%6%35%5%35%5%5%10%42%
1551
June1st to 10thNight
8%4235%346%7%9%47%
1440
11th to 20thNight
11%5%25%43446%10%46%
1440
21st to endNight
9%5%26%445%5%6%8%46%
1440
July1st to 10thNight
6%3145%2445%11%53%
1440
11th to 20thNight
7%32433445%9%56%
1440
21st to endNight
7%3244346%7%10%50%
1575
August1st to 10thNight
5%325%6%3445%8%54%
1485
11th to 20thNight
9%3244235%5%8%55%
1742
21st to endNight
9%4235%34447%54%
1980
September1st to 10thNight
10%6%25%33335%6%55%
1800
11th to 20thNight
11%424434447%53%
1843
21st to endNight
11%5%2443445%6%50%
1980
October1st to 10thNight
12%6%25%42445%5%50%
2110
11th to 20thNight
18%6%245%33346%44%
2160
21st to endNight
19%9%25%5%3445%6%38%
2533
November1st to 10thNight
12%8%26%423436%51%
2406
11th to 20thNight
15%10%47%5%2445%6%37%
2470
21st to endNight
18%8%46%5%34446%38%
2636
December1st to 10thNight
15%12%5%8%6%45%45%7%31%
2660
11th to 20thNight
15%12%48%6%34446%32%
3279
21st to endNight
22%15%6%10%6%45%5%45%19%
4884

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
54%7%13%16%10%
1518
11th to 20thDay
61%6%13%14%6%
1461
21st to endDay
63%5%10%13%8%1
1683
February1st to 10thDay
57%5%12%17%9%1
1620
11th to 20thDay
50%6%12%22%9%2
1713
21st to endDay
55%5%9%20%10%1
1480
March1st to 10thDay
51%5%15%19%8%1
1800
11th to 20thDay
44%6%13%23%12%1
1908
21st to endDay
57%6%11%18%7%1
2346
April1st to 10thDay
53%6%11%21%9%
2160
11th to 20thDay
50%6%10%21%11%2
2134
21st to endDay
51%6%12%18%12%2
2204
May1st to 10thDay
51%8%13%21%6%
2386
11th to 20thDay
49%7%12%21%11%
2483
21st to endDay
45%8%12%19%14%2
2725
June1st to 10thDay
37%8%13%25%16%1
2520
11th to 20thDay
35%7%13%24%19%2
2520
21st to endDay
40%7%16%23%13%1
2520
July1st to 10thDay
32%7%16%29%13%3
2451
11th to 20thDay
31%8%17%26%16%2
2445
21st to endDay
33%7%17%25%15%3
2591
August1st to 10thDay
33%8%18%28%12%1
2436
11th to 20thDay
35%6%15%28%15%1
2156
21st to endDay
33%6%12%27%19%2
2376
September1st to 10thDay
38%6%10%25%19%2
2160
11th to 20thDay
30%7%11%32%18%3
2098
21st to endDay
38%5%11%28%17%1
1980
October1st to 10thDay
38%6%11%28%16%1
1846
11th to 20thDay
49%5%11%21%13%1
1800
21st to endDay
48%5%10%23%12%1
1823
November1st to 10thDay
40%415%25%15%2
1672
11th to 20thDay
52%5%13%20%10%1
1710
21st to endDay
50%5%14%22%8%1
1542
December1st to 10thDay
54%6%14%17%8%1
1520
11th to 20thDay
56%416%15%8%2
1915
21st to endDay
75%5%8%8%4
2783
January1st to 10thNight
51%5%11%19%12%1
2648
11th to 20thNight
59%5%12%15%9%
2561
21st to endNight
59%5%11%15%9%1
2671
February1st to 10thNight
56%410%19%11%1
2340
11th to 20thNight
48%412%21%13%1
2143
21st to endNight
51%412%19%11%3
1776
March1st to 10thNight
48%6%15%20%10%1
2160
11th to 20thNight
42%6%12%20%17%2
2066
21st to endNight
56%5%11%18%10%1
2008
April1st to 10thNight
47%6%12%21%13%2
1800
11th to 20thNight
47%37%21%17%4
1775
21st to endNight
45%7%13%22%11%2
1756
May1st to 10thNight
45%8%14%21%11%
1571
11th to 20thNight
44%6%14%21%14%1
1417
21st to endNight
37%9%14%21%17%2
1552
June1st to 10thNight
31%7%15%26%19%2
1440
11th to 20thNight
34%7%9%24%24%3
1440
21st to endNight
36%8%14%22%17%3
1440
July1st to 10thNight
26%7%17%29%17%4
1400
11th to 20thNight
26%6%14%31%21%3
1392
21st to endNight
25%8%18%26%19%5%
1487
August1st to 10thNight
28%6%17%33%14%3
1476
11th to 20thNight
27%6%16%30%20%1
1742
21st to endNight
29%6%13%27%21%4
1980
September1st to 10thNight
31%6%11%26%23%3
1800
11th to 20thNight
31%5%10%32%19%3
1843
21st to endNight
34%6%11%29%19%2
1980
October1st to 10thNight
35%6%9%27%21%2
2110
11th to 20thNight
41%5%10%24%18%2
2160
21st to endNight
48%5%11%24%11%1
2533
November1st to 10thNight
36%5%10%27%19%3
2406
11th to 20thNight
47%6%12%21%12%1
2470
21st to endNight
48%5%13%23%11%1
2636
December1st to 10thNight
55%5%11%20%8%1
2660
11th to 20thNight
53%5%13%19%8%1
3281
21st to endNight
67%6%9%13%5%
4884

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
19%14%31%29%7%1
270
11th to 20thDay
21%14%38%21%42
248
21st to endDay
23%10%41%20%5%1
264
February1st to 10thDay
19%20%39%17%5%
240
11th to 20thDay
23%22%29%23%3
240
21st to endDay
26%19%41%12%2
198
March1st to 10thDay
19%22%39%16%4
240
11th to 20thDay
22%19%35%15%8%1
240
21st to endDay
30%14%29%19%7%2
432
April1st to 10thDay
25%14%32%23%6%
420
11th to 20thDay
22%20%27%20%9%3
412
21st to endDay
24%13%29%23%10%2
420
May1st to 10thDay
21%14%31%24%7%3
469
11th to 20thDay
23%10%29%23%12%3
625
21st to endDay
17%9%27%22%17%8%
679
June1st to 10thDay
9%6%29%31%19%6%
630
11th to 20thDay
13%7%32%28%15%5%
630
21st to endDay
15%6%28%31%16%5%
630
July1st to 10thDay
9%216%33%26%14%
621
11th to 20thDay
9%5%26%31%20%9%
618
21st to endDay
7%325%36%22%6%
684
August1st to 10thDay
6%222%33%26%10%
626
11th to 20thDay
11%6%17%27%22%16%
470
21st to endDay
12%419%31%24%10%
495
September1st to 10thDay
17%6%21%28%21%7%
450
11th to 20thDay
12%420%30%23%11%
450
21st to endDay
15%12%24%24%17%7%
450
October1st to 10thDay
17%9%27%27%17%3
316
11th to 20thDay
25%22%32%14%7%
270
21st to endDay
29%16%29%19%7%
297
November1st to 10thDay
16%18%35%20%9%3
270
11th to 20thDay
20%17%39%17%6%1
270
21st to endDay
26%13%36%21%4
270
December1st to 10thDay
19%15%43%17%5%2
270
11th to 20thDay
20%11%40%21%8%1
270
21st to endDay
26%16%40%16%2
297
January1st to 10thNight
19%14%37%25%5%1
950
11th to 20thNight
20%11%38%25%5%1
915
21st to endNight
20%11%37%26%5%
990
February1st to 10thNight
21%12%38%23%5%
900
11th to 20thNight
18%14%38%24%5%
747
21st to endNight
25%14%37%20%4
592
March1st to 10thNight
22%11%36%25%6%
720
11th to 20thNight
16%12%35%29%8%
626
21st to endNight
25%10%33%26%6%1
594
April1st to 10thNight
21%12%37%25%5%
540
11th to 20thNight
22%13%28%29%7%
533
21st to endNight
21%9%33%28%10%1
540
May1st to 10thNight
18%8%34%30%9%1
540
11th to 20thNight
20%6%32%31%11%
531
21st to endNight
13%5%31%34%16%1
584
June1st to 10thNight
9%5%25%43%17%1
540
11th to 20thNight
13%427%42%13%
540
21st to endNight
9%428%40%18%1
540
July1st to 10thNight
7%214%42%31%4
525
11th to 20thNight
8%221%43%24%2
522
21st to endNight
9%217%45%26%1
591
August1st to 10thNight
5%215%46%29%3
537
11th to 20thNight
7%214%39%32%6%
534
21st to endNight
10%217%41%28%3
594
September1st to 10thNight
11%422%35%24%5%
540
11th to 20thNight
11%323%34%25%4
583
21st to endNight
13%9%26%31%20%2
720
October1st to 10thNight
15%7%29%31%17%1
720
11th to 20thNight
21%12%31%27%10%
720
21st to endNight
23%11%34%24%8%1
792
November1st to 10thNight
15%9%42%23%10%1
740
11th to 20thNight
19%14%36%25%6%
760
21st to endNight
22%12%35%25%7%
926
December1st to 10thNight
21%12%39%22%6%
950
11th to 20thNight
22%11%35%26%5%1
950
21st to endNight
27%13%36%22%3
1045
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