Cache Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cache Creek clear sky chart from 2005-11-06 to 2024-02-05.

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
40%
23000
10%
80895
7%
22893
43%
22893
14%
59201

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
20%
839
4%
4711
2%
816
24%
816
3%
3944
January11th to 20thNight
24%
839
11%
4665
2%
820
27%
820
4%
3460
January21st to endNight
27%
831
4%
4880
5%
816
32%
816
5%
4195
February1st to 10thNight
27%
738
9%
2499
6%
738
31%
738
10%
1966
February11th to 20thNight
38%
700
12%
2274
9%
700
44%
700
16%
1641
February21st to endNight
35%
592
11%
1870
9%
592
39%
592
14%
1403
March1st to 10thNight
35%
720
11%
2160
7%
720
39%
720
16%
1568
March11th to 20thNight
39%
720
14%
2005
8%
720
44%
720
22%
1386
March21st to endNight
40%
792
11%
2062
6%
792
42%
792
19%
1540
April1st to 10thNight
46%
720
10%
1800
4%
720
48%
720
21%
1328
April11th to 20thNight
40%
664
12%
1732
6%
664
43%
664
20%
1254
April21st to endNight
41%
388
12%
1468
12%
388
46%
388
18%
967
May1st to 10thNight
41%
360
10%
1440
13%
360
46%
360
15%
974
May11th to 20thNight
57%
354
9%
1416
15%
354
59%
354
17%
936
May21st to endNight
52%
388
5%
1494
5%
388
53%
388
15%
1037
June1st to 10thNight
43%
360
3%
1131
0%
360
43%
360
18%
809
June11th to 20thNight
43%
360
1%
1080
0%
360
43%
360
18%
783
June21st to endNight
53%
360
2%
1096
0%
360
53%
360
26%
710
July1st to 10thNight
58%
350
3%
1225
0%
350
58%
350
23%
775
July11th to 20thNight
57%
348
9%
1218
6%
348
58%
348
26%
714
July21st to endNight
70%
394
12%
1442
19%
372
73%
372
34%
737
August1st to 10thNight
72%
358
15%
1424
22%
356
74%
356
29%
742
August11th to 20thNight
70%
418
23%
1486
26%
418
74%
418
35%
784
August21st to endNight
57%
684
16%
1872
12%
684
59%
684
29%
1221
September1st to 10thNight
58%
720
18%
1800
10%
720
59%
720
35%
1144
September11th to 20thNight
59%
720
20%
1800
11%
720
61%
720
31%
1192
September21st to endNight
48%
720
17%
2038
11%
720
53%
720
26%
1333
October1st to 10thNight
50%
720
14%
2160
12%
720
53%
720
21%
1475
October11th to 20thNight
43%
720
13%
2164
10%
720
48%
720
20%
1505
October21st to endNight
34%
792
12%
2578
8%
792
40%
792
17%
1807
November1st to 10thNight
29%
740
9%
2590
5%
740
36%
740
11%
1961
November11th to 20thNight
31%
760
10%
2660
6%
760
37%
760
12%
1972
November21st to endNight
28%
783
7%
2683
4%
783
32%
783
9%
2130
December1st to 10thNight
33%
964
9%
2879
6%
964
36%
964
12%
2311
December11th to 20thNight
23%
1040
3%
3747
2%
1039
25%
1039
7%
3283
December21st to endNight
24%
1044
5%
5346
4%
1019
29%
1019
5%
4214

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
7%9%49%8%46%6%7%8%32%
77606
Night
7%11%5%9%8%46%6%6%7%30%
81175
TransparencyDay
48%11%15%17%8%1
77315
Night
51%11%14%16%7%1
81046
SeeingDay
11%16%31%26%13%3
14554
Night
11%8%30%32%17%2
23040

By Month

Percentage Cloud Cover NW (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
8%13%7%17%12%5%7%6%6%5%11%
2219
11th to 20thDay
10%11%6%12%9%46%5%6%9%23%
2199
21st to endDay
10%21%8%12%7%5%5%5%5%6%15%
2775
February1st to 10thDay
8%13%6%10%8%5%7%6%7%8%22%
1553
11th to 20thDay
6%11%49%7%46%7%8%8%30%
1575
21st to endDay
311%5%11%10%6%7%7%7%8%24%
1386
March1st to 10thDay
49%5%9%8%6%8%7%8%9%29%
1800
11th to 20thDay
37%48%9%5%8%7%9%10%30%
1952
21st to endDay
411%5%10%9%5%8%7%8%8%25%
2294
April1st to 10thDay
5%11%5%10%10%5%6%7%8%8%24%
2160
11th to 20thDay
7%11%5%9%9%5%7%6%7%8%25%
2177
21st to endDay
7%11%5%10%8%5%6%6%7%8%28%
2492
May1st to 10thDay
8%11%49%8%46%7%6%7%30%
2520
11th to 20thDay
7%9%37%9%47%6%8%10%30%
2477
21st to endDay
13%11%48%8%5%7%7%7%6%25%
2778
June1st to 10thDay
13%9%5%8%8%47%7%6%7%28%
2826
11th to 20thDay
15%9%48%9%5%8%6%6%6%23%
2880
21st to endDay
7%8%37%8%47%6%7%8%35%
2859
July1st to 10thDay
6%6%26%7%46%6%7%7%42%
2700
11th to 20thDay
7%425%5%46%6%7%9%46%
2700
21st to endDay
5%4245%35%5%6%9%53%
2787
August1st to 10thDay
6%425%5%35%6%7%8%50%
2507
11th to 20thDay
4425%435%6%7%7%54%
2411
21st to endDay
7%7%36%6%5%6%7%6%8%40%
2484
September1st to 10thDay
7%6%35%6%345%6%7%49%
2160
11th to 20thDay
10%7%37%6%35%5%5%8%41%
2160
21st to endDay
9%7%37%6%46%6%5%7%39%
1918
October1st to 10thDay
8%9%37%7%36%5%5%7%41%
1800
11th to 20thDay
8%7%46%7%46%7%8%9%35%
1795
21st to endDay
8%11%49%7%45%6%6%8%31%
1777
November1st to 10thDay
9%12%5%11%8%46%6%6%8%27%
1488
11th to 20thDay
5%9%5%8%7%46%5%7%8%35%
1520
21st to endDay
6%11%7%11%10%5%5%7%8%7%22%
1474
December1st to 10thDay
5%14%6%12%9%7%8%6%5%7%21%
1297
11th to 20thDay
6%19%8%15%10%45%5%46%17%
1442
21st to endDay
5%11%6%14%11%7%7%7%6%7%18%
2264
January1st to 10thNight
8%19%8%14%9%5%7%6%6%6%12%
4726
11th to 20thNight
9%16%7%12%8%5%5%49%6%20%
4699
21st to endNight
9%18%8%16%9%5%7%5%45%14%
4880
February1st to 10thNight
10%12%5%11%10%5%6%6%6%7%22%
2499
11th to 20thNight
7%11%48%8%5%6%5%6%8%32%
2272
21st to endNight
412%6%12%8%47%5%9%8%25%
1870
March1st to 10thNight
410%5%10%8%46%7%8%8%29%
2160
11th to 20thNight
27%48%7%46%7%8%10%37%
2005
21st to endNight
38%47%9%47%8%8%10%32%
2062
April1st to 10thNight
39%47%8%5%8%7%7%9%35%
1800
11th to 20thNight
38%48%9%47%7%8%9%33%
1732
21st to endNight
6%8%48%6%46%6%6%11%35%
1468
May1st to 10thNight
9%9%5%8%7%35%5%5%7%36%
1440
11th to 20thNight
7%6%36%6%5%6%7%8%11%34%
1416
21st to endNight
14%7%37%6%46%5%7%10%32%
1494
June1st to 10thNight
12%8%47%6%48%6%6%9%32%
1131
11th to 20thNight
10%8%37%8%5%7%5%9%10%28%
1080
21st to endNight
6%7%36%7%36%5%7%9%42%
1096
July1st to 10thNight
8%7%25%6%36%6%6%8%43%
1260
11th to 20thNight
5%5%247%46%6%7%8%47%
1260
21st to endNight
43145%35%6%6%8%55%
1527
August1st to 10thNight
4315%5%35%6%5%9%53%
1432
11th to 20thNight
5%4245%245%5%9%55%
1486
21st to endNight
8%6%26%6%46%6%6%9%43%
1872
September1st to 10thNight
5%5%26%5%35%5%47%52%
1800
11th to 20thNight
8%6%25%5%45%47%8%46%
1800
21st to endNight
8%8%36%5%35%5%5%8%45%
2038
October1st to 10thNight
7%8%37%7%46%5%5%8%41%
2160
11th to 20thNight
9%9%37%6%35%6%6%7%39%
2164
21st to endNight
7%11%49%7%35%5%5%7%36%
2578
November1st to 10thNight
10%13%48%8%46%6%7%7%27%
2590
11th to 20thNight
6%10%6%8%8%46%6%7%7%30%
2660
21st to endNight
9%14%8%10%8%5%5%6%7%7%22%
2683
December1st to 10thNight
6%14%8%10%10%5%7%5%6%6%24%
2879
11th to 20thNight
12%19%7%15%9%45%5%5%5%14%
3750
21st to endNight
7%13%7%12%11%6%9%6%6%6%17%
5406

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
67%13%9%9%1
2219
11th to 20thDay
57%9%14%12%36%
2220
21st to endDay
68%11%9%9%2
2775
February1st to 10thDay
58%11%13%11%7%1
1553
11th to 20thDay
49%12%17%16%7%
1584
21st to endDay
55%12%14%14%5%1
1386
March1st to 10thDay
47%14%18%13%8%1
1800
11th to 20thDay
45%15%17%17%5%1
1952
21st to endDay
52%14%18%14%3
2294
April1st to 10thDay
53%13%16%14%4
2160
11th to 20thDay
53%12%13%13%8%1
2177
21st to endDay
50%12%15%16%7%
2492
May1st to 10thDay
51%10%16%14%9%
2520
11th to 20thDay
45%12%16%19%7%
2480
21st to endDay
54%11%13%16%5%1
2779
June1st to 10thDay
53%11%12%13%8%3
2826
11th to 20thDay
58%12%13%11%5%
2880
21st to endDay
44%11%16%17%10%2
2859
July1st to 10thDay
36%10%15%21%15%3
2626
11th to 20thDay
32%11%17%25%13%2
2619
21st to endDay
25%9%15%29%19%2
2632
August1st to 10thDay
29%10%17%26%17%2
2490
11th to 20thDay
26%11%17%28%16%2
2411
21st to endDay
38%11%17%24%8%2
2484
September1st to 10thDay
33%9%17%27%11%3
2160
11th to 20thDay
41%9%13%22%13%2
2160
21st to endDay
43%10%19%17%9%1
1918
October1st to 10thDay
42%10%16%25%7%
1800
11th to 20thDay
43%13%18%20%6%
1795
21st to endDay
50%12%14%19%4
1777
November1st to 10thDay
54%12%13%15%6%
1488
11th to 20thDay
47%15%14%17%7%
1520
21st to endDay
57%12%15%12%4
1474
December1st to 10thDay
64%9%13%11%2
1297
11th to 20thDay
69%10%10%8%3
1444
21st to endDay
58%15%12%12%3
2264
January1st to 10thNight
69%11%11%7%2
4726
11th to 20thNight
63%7%12%10%35%
4740
21st to endNight
70%11%9%6%3
4880
February1st to 10thNight
59%10%12%12%5%1
2499
11th to 20thNight
51%8%15%17%8%
2274
21st to endNight
53%11%16%15%6%
1870
March1st to 10thNight
47%12%17%15%8%
2160
11th to 20thNight
39%13%19%22%6%1
2006
21st to endNight
44%15%19%17%5%
2062
April1st to 10thNight
44%13%18%19%6%
1800
11th to 20thNight
45%12%16%18%10%
1732
21st to endNight
42%12%17%20%10%
1468
May1st to 10thNight
47%10%15%19%9%1
1440
11th to 20thNight
42%13%18%21%7%
1416
21st to endNight
47%12%17%18%7%1
1494
June1st to 10thNight
48%10%13%17%8%3
1131
11th to 20thNight
47%12%19%14%7%1
1080
21st to endNight
37%10%20%20%10%3
1096
July1st to 10thNight
38%10%14%20%14%3
1225
11th to 20thNight
31%11%18%25%12%3
1218
21st to endNight
24%9%15%27%20%4
1442
August1st to 10thNight
26%10%16%24%19%3
1424
11th to 20thNight
26%8%16%30%16%3
1486
21st to endNight
36%10%18%24%11%1
1872
September1st to 10thNight
31%9%15%29%14%3
1800
11th to 20thNight
36%9%15%22%15%3
1800
21st to endNight
37%10%20%20%11%2
2038
October1st to 10thNight
42%11%14%25%8%
2160
11th to 20thNight
43%11%17%21%7%
2164
21st to endNight
48%9%17%20%6%
2578
November1st to 10thNight
55%11%14%13%6%1
2590
11th to 20thNight
50%14%14%15%6%1
2660
21st to endNight
60%11%14%11%4
2683
December1st to 10thNight
60%10%13%13%4
2879
11th to 20thNight
72%9%9%8%2
3747
21st to endNight
60%13%11%11%4
5406

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
8%17%39%22%8%6%
180
11th to 20thDay
9%15%31%32%11%3
180
21st to endDay
14%12%37%28%8%1
198
February1st to 10thDay
10%19%49%18%3
249
11th to 20thDay
11%13%42%26%8%1
335
21st to endDay
7%17%43%22%9%1
304
March1st to 10thDay
11%21%34%22%11%1
420
11th to 20thDay
10%24%34%18%12%2
420
21st to endDay
13%26%31%19%10%1
462
April1st to 10thDay
15%21%32%23%8%1
420
11th to 20thDay
18%22%27%18%11%3
412
21st to endDay
12%23%31%22%9%2
420
May1st to 10thDay
13%20%30%25%10%2
423
11th to 20thDay
13%11%29%29%13%4
448
21st to endDay
14%13%29%29%12%3
540
June1st to 10thDay
15%19%33%23%10%1
756
11th to 20thDay
16%15%29%27%13%1
810
21st to endDay
10%11%28%30%19%2
789
July1st to 10thDay
9%12%31%30%17%2
621
11th to 20thDay
7%13%30%29%17%4
618
21st to endDay
38%24%36%25%4
533
August1st to 10thDay
6%7%23%32%27%5%
447
11th to 20thDay
6%11%23%34%22%5%
437
21st to endDay
8%12%29%30%15%5%
495
September1st to 10thDay
9%16%30%30%12%3
450
11th to 20thDay
15%14%25%26%16%4
450
21st to endDay
15%18%32%22%11%2
450
October1st to 10thDay
15%16%28%24%13%4
450
11th to 20thDay
14%23%29%20%13%2
445
21st to endDay
17%14%37%20%11%
294
November1st to 10thDay
14%22%33%21%10%1
180
11th to 20thDay
11%11%42%23%10%3
180
21st to endDay
11%13%37%27%7%6%
180
December1st to 10thDay
8%9%36%23%19%4
180
11th to 20thDay
9%11%39%25%11%5%
180
21st to endDay
11%10%37%30%10%1
198
January1st to 10thNight
16%11%38%24%9%2
850
11th to 20thNight
13%8%35%32%10%1
850
21st to endNight
10%8%37%30%13%2
839
February1st to 10thNight
14%9%36%30%10%1
738
11th to 20thNight
12%7%33%37%11%1
704
21st to endNight
7%9%37%29%16%2
592
March1st to 10thNight
10%9%34%30%15%1
720
11th to 20thNight
5%14%35%31%14%2
720
21st to endNight
8%10%32%32%16%2
792
April1st to 10thNight
7%10%26%35%20%2
720
11th to 20thNight
6%9%34%33%16%1
664
21st to endNight
9%8%36%30%17%1
388
May1st to 10thNight
11%9%30%31%18%2
360
11th to 20thNight
9%6%21%41%21%3
354
21st to endNight
18%419%35%21%2
389
June1st to 10thNight
13%7%28%33%18%2
360
11th to 20thNight
13%6%26%37%15%3
360
21st to endNight
9%424%36%25%1
360
July1st to 10thNight
7%5%23%39%24%2
350
11th to 20thNight
8%5%22%39%25%2
348
21st to endNight
5%314%40%35%3
394
August1st to 10thNight
5%313%34%39%5%
358
11th to 20thNight
5%416%36%33%6%
418
21st to endNight
9%5%21%35%28%2
684
September1st to 10thNight
8%6%19%40%24%3
720
11th to 20thNight
11%5%18%29%30%7%
720
21st to endNight
13%12%23%30%19%3
720
October1st to 10thNight
12%10%22%32%22%3
720
11th to 20thNight
14%10%27%30%17%3
720
21st to endNight
16%9%32%29%11%3
792
November1st to 10thNight
17%11%33%30%8%1
740
11th to 20thNight
13%10%34%30%11%2
760
21st to endNight
15%11%34%27%9%3
783
December1st to 10thNight
12%8%33%33%13%2
964
11th to 20thNight
16%9%36%29%8%
1040
21st to endNight
13%11%36%30%9%1
1049
Page generated at 2024-02-02 02:20:32. Version ac07

Copyright 2024 Attilla Danko


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