Forestville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Forestville clear sky chart from 2005-11-06 to 2024-01-14.

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
57%
23584
25%
74827
21%
23535
63%
23535
32%
43076

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
48%
756
16%
2529
15%
756
53%
756
20%
1670
January11th to 20thNight
51%
734
19%
2384
17%
734
56%
734
23%
1520
January21st to endNight
55%
792
24%
2574
24%
792
59%
792
27%
1577
February1st to 10thNight
53%
720
25%
2340
23%
720
60%
720
27%
1405
February11th to 20thNight
47%
701
23%
2250
19%
700
55%
700
26%
1379
February21st to endNight
47%
592
26%
1772
18%
592
56%
592
31%
1029
March1st to 10thNight
42%
720
16%
1980
11%
720
46%
720
20%
1408
March11th to 20thNight
48%
720
21%
1980
17%
720
53%
720
27%
1296
March21st to endNight
42%
792
20%
2177
12%
792
49%
792
30%
1381
April1st to 10thNight
40%
720
22%
1800
9%
720
47%
720
30%
1177
April11th to 20thNight
43%
711
27%
1779
11%
711
50%
711
36%
1085
April21st to endNight
47%
720
28%
1800
10%
720
55%
720
43%
1035
May1st to 10thNight
50%
560
28%
1640
15%
560
58%
560
39%
893
May11th to 20thNight
56%
501
26%
1564
18%
501
63%
501
41%
809
May21st to endNight
53%
388
25%
1552
21%
388
64%
388
30%
751
June1st to 10thNight
57%
360
24%
1440
21%
360
67%
360
34%
688
June11th to 20thNight
62%
360
33%
1440
34%
360
73%
360
46%
571
June21st to endNight
71%
360
31%
1440
37%
360
76%
360
46%
591
July1st to 10thNight
74%
350
30%
1400
35%
350
81%
350
50%
551
July11th to 20thNight
79%
522
28%
1566
26%
522
80%
522
53%
729
July21st to endNight
70%
591
29%
1674
26%
558
70%
558
38%
883
August1st to 10thNight
66%
537
29%
1602
24%
534
68%
534
43%
813
August11th to 20thNight
71%
585
31%
1653
21%
585
74%
585
47%
864
August21st to endNight
72%
792
31%
1980
20%
792
73%
792
50%
1113
September1st to 10thNight
78%
720
39%
1800
25%
720
80%
720
63%
909
September11th to 20thNight
67%
720
34%
1818
23%
720
72%
720
46%
1057
September21st to endNight
69%
720
36%
2056
32%
720
75%
720
53%
1022
October1st to 10thNight
66%
720
29%
2160
28%
720
73%
720
46%
1094
October11th to 20thNight
65%
720
32%
2160
32%
720
71%
720
39%
1178
October21st to endNight
66%
792
34%
2376
33%
792
71%
792
40%
1305
November1st to 10thNight
60%
740
29%
2224
25%
740
66%
740
35%
1283
November11th to 20thNight
62%
760
23%
2516
23%
760
65%
760
31%
1441
November21st to endNight
59%
760
25%
2660
25%
760
65%
760
32%
1425
December1st to 10thNight
50%
760
21%
2660
19%
760
56%
760
23%
1674
December11th to 20thNight
48%
760
16%
3252
18%
759
53%
759
15%
2307
December21st to endNight
43%
828
14%
4829
18%
817
50%
817
11%
3163

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
9%5%24323346%58%
74681
Night
11%5%24423447%53%
75083
TransparencyDay
29%5%10%20%23%14%
74402
Night
33%5%9%19%21%14%
74884
SeeingDay
11%11%24%29%19%6%
14243
Night
12%6%16%31%29%6%
23600

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
22%7%35%5%33446%38%
1633
11th to 20thDay
16%6%346%24346%46%
1648
21st to endDay
14%7%345%35%46%7%43%
1782
February1st to 10thDay
17%5%35%44444448%
1620
11th to 20thDay
13%6%35%425%45%8%46%
1597
21st to endDay
16%6%24423445%49%
1482
March1st to 10thDay
17%8%36%5%4445%6%37%
1980
11th to 20thDay
18%6%25%435%46%8%39%
1980
21st to endDay
15%5%3443445%7%46%
2178
April1st to 10thDay
14%6%36%5%35%35%8%42%
2160
11th to 20thDay
9%6%2442445%7%54%
2129
21st to endDay
6%424323449%58%
2160
May1st to 10thDay
7%423313348%61%
2316
11th to 20thDay
6%5%1332335%7%62%
2325
21st to endDay
6%6%24422347%60%
2723
June1st to 10thDay
6%6%24313348%59%
2520
11th to 20thDay
2311212336%74%
2520
21st to endDay
242322223475%
2520
July1st to 10thDay
242321224474%
2516
11th to 20thDay
1423212347%71%
2340
21st to endDay
1424312335%72%
2546
August1st to 10thDay
15%23323337%68%
2328
11th to 20thDay
1423222246%72%
2244
21st to endDay
27%34322236%67%
2376
September1st to 10thDay
1313221236%75%
2160
11th to 20thDay
45%15%313347%64%
2138
21st to endDay
4312112336%73%
1904
October1st to 10thDay
6%312323345%68%
1800
11th to 20thDay
8%424323346%63%
1800
21st to endDay
11%423223347%60%
1980
November1st to 10thDay
10%42343335%7%55%
1852
11th to 20thDay
12%5%25%5%3435%7%50%
1662
21st to endDay
11%5%233335%5%6%54%
1520
December1st to 10thDay
18%6%3443345%6%45%
1520
11th to 20thDay
33%8%25%42335%5%30%
1928
21st to endDay
24%7%35%43335%7%36%
2794
January1st to 10thNight
19%7%35%42445%9%37%
2529
11th to 20thNight
18%6%245%23446%44%
2384
21st to endNight
16%5%24325%447%48%
2574
February1st to 10thNight
17%5%24423446%49%
2340
11th to 20thNight
12%7%35%435%45%8%45%
2248
21st to endNight
15%5%23223446%54%
1772
March1st to 10thNight
18%8%46%425%5%5%5%38%
1980
11th to 20thNight
15%7%35%4245%6%7%43%
1980
21st to endNight
15%6%25%424345%51%
2177
April1st to 10thNight
11%5%36%5%2345%6%50%
1800
11th to 20thNight
8%5%25%424336%56%
1779
21st to endNight
6%423323448%62%
1800
May1st to 10thNight
5%6%24323347%60%
1640
11th to 20thNight
45%15%42445%8%59%
1563
21st to endNight
5%5%35%322447%61%
1552
June1st to 10thNight
5%5%3442445%9%58%
1440
11th to 20thNight
2313323336%71%
1440
21st to endNight
342432224470%
1440
July1st to 10thNight
1423222336%72%
1440
11th to 20thNight
142332335%7%66%
1620
21st to endNight
16%37%42346%9%54%
1773
August1st to 10thNight
27%35%423347%61%
1611
11th to 20thNight
15%27%4235%5%8%59%
1653
21st to endNight
16%35%423347%62%
1980
September1st to 10thNight
414323338%69%
1800
11th to 20thNight
5%6%25%32435%7%59%
1818
21st to endNight
35%24312235%70%
2056
October1st to 10thNight
5%5%2442335%5%64%
2160
11th to 20thNight
7%435%42335%6%58%
2160
21st to endNight
9%424323446%58%
2376
November1st to 10thNight
10%4245%2335%8%53%
2224
11th to 20thNight
12%5%3432445%8%49%
2516
21st to endNight
10%424433447%56%
2660
December1st to 10thNight
20%6%34423346%45%
2660
11th to 20thNight
32%6%23423446%32%
3276
21st to endNight
24%7%25%5%24446%37%
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
48%6%12%20%9%6%
1633
11th to 20thDay
41%5%9%16%15%13%
1648
21st to endDay
43%5%9%16%19%8%
1782
February1st to 10thDay
42%47%19%20%8%
1620
11th to 20thDay
38%6%9%20%19%7%
1606
21st to endDay
38%5%11%25%15%7%
1482
March1st to 10thDay
46%8%12%16%15%3
1980
11th to 20thDay
44%6%10%21%13%5%
1980
21st to endDay
39%8%14%20%17%3
2178
April1st to 10thDay
42%6%13%20%15%4
2160
11th to 20thDay
31%6%15%23%20%5%
2132
21st to endDay
24%6%15%30%21%4
2160
May1st to 10thDay
24%6%10%28%26%7%
2316
11th to 20thDay
22%6%11%32%22%7%
2328
21st to endDay
26%6%18%28%20%3
2724
June1st to 10thDay
25%5%12%28%25%6%
2520
11th to 20thDay
14%411%21%36%15%
2520
21st to endDay
15%36%17%36%24%
2520
July1st to 10thDay
15%3414%29%35%
2447
11th to 20thDay
16%46%15%28%32%
2271
21st to endDay
17%2411%28%37%
2405
August1st to 10thDay
19%37%18%30%24%
2312
11th to 20thDay
16%26%15%35%26%
2244
21st to endDay
21%25%16%33%23%
2376
September1st to 10thDay
13%3413%31%36%
2160
11th to 20thDay
22%49%25%31%10%
2138
21st to endDay
15%37%25%28%22%
1904
October1st to 10thDay
21%36%18%30%22%
1800
11th to 20thDay
23%6%9%19%23%20%
1800
21st to endDay
26%5%9%20%24%16%
1980
November1st to 10thDay
30%6%9%27%18%10%
1852
11th to 20thDay
36%6%12%23%15%8%
1662
21st to endDay
31%6%12%20%19%13%
1520
December1st to 10thDay
40%6%11%16%18%9%
1520
11th to 20thDay
57%5%7%12%14%5%
1928
21st to endDay
48%6%12%20%9%4
2794
January1st to 10thNight
45%7%13%19%10%5%
2529
11th to 20thNight
42%6%10%16%13%13%
2384
21st to endNight
38%6%12%14%21%10%
2574
February1st to 10thNight
38%5%8%20%18%11%
2340
11th to 20thNight
38%6%10%20%19%7%
2250
21st to endNight
32%5%13%24%20%6%
1772
March1st to 10thNight
47%8%11%14%17%4
1980
11th to 20thNight
41%5%10%21%18%5%
1980
21st to endNight
37%6%12%23%16%5%
2177
April1st to 10thNight
35%8%13%20%20%5%
1800
11th to 20thNight
30%5%13%24%19%9%
1779
21st to endNight
24%5%10%30%24%6%
1800
May1st to 10thNight
26%5%8%22%29%10%
1640
11th to 20thNight
24%6%10%27%25%8%
1564
21st to endNight
26%6%13%28%23%5%
1552
June1st to 10thNight
25%5%10%21%30%8%
1440
11th to 20thNight
16%49%21%32%19%
1440
21st to endNight
18%4415%30%29%
1440
July1st to 10thNight
17%3411%30%36%
1400
11th to 20thNight
19%26%13%28%31%
1566
21st to endNight
30%2410%19%34%
1674
August1st to 10thNight
27%25%15%25%26%
1602
11th to 20thNight
24%35%13%27%28%
1653
21st to endNight
25%35%16%25%27%
1980
September1st to 10thNight
15%3412%32%34%
1800
11th to 20thNight
27%46%21%29%14%
1818
21st to endNight
19%35%22%26%25%
2056
October1st to 10thNight
22%48%16%27%23%
2160
11th to 20thNight
28%47%19%21%22%
2160
21st to endNight
27%48%18%24%18%
2376
November1st to 10thNight
32%411%25%18%10%
2224
11th to 20thNight
33%6%13%24%16%8%
2516
21st to endNight
30%5%10%20%22%13%
2660
December1st to 10thNight
42%6%7%17%18%10%
2660
11th to 20thNight
53%6%9%13%14%4
3276
21st to endNight
48%8%12%17%12%3
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
29%15%24%17%11%4
294
11th to 20thDay
22%11%24%24%15%3
350
21st to endDay
15%14%23%29%17%3
374
February1st to 10thDay
19%12%21%24%19%5%
340
11th to 20thDay
18%18%26%24%13%1
345
21st to endDay
19%16%26%25%13%1
346
March1st to 10thDay
25%18%28%20%8%2
420
11th to 20thDay
24%15%28%19%10%4
420
21st to endDay
16%19%34%22%8%1
462
April1st to 10thDay
17%20%29%21%10%2
420
11th to 20thDay
16%20%29%23%8%4
412
21st to endDay
8%21%31%24%11%5%
420
May1st to 10thDay
12%18%30%26%12%3
423
11th to 20thDay
11%17%32%24%13%4
448
21st to endDay
12%13%25%27%19%5%
485
June1st to 10thDay
9%14%27%30%13%7%
450
11th to 20thDay
6%13%30%34%13%3
450
21st to endDay
25%28%35%25%6%
450
July1st to 10thDay
5%5%22%42%22%4
446
11th to 20thDay
2218%43%28%7%
444
21st to endDay
2213%48%28%7%
487
August1st to 10thDay
3421%44%21%7%
447
11th to 20thDay
4320%38%27%9%
437
21st to endDay
5%220%39%27%6%
495
September1st to 10thDay
25%18%39%26%10%
450
11th to 20thDay
5%9%24%32%23%8%
450
21st to endDay
5%9%21%32%25%8%
450
October1st to 10thDay
6%10%25%25%23%11%
450
11th to 20thDay
9%9%18%27%27%10%
450
21st to endDay
14%8%18%28%25%8%
495
November1st to 10thDay
12%11%17%26%27%6%
448
11th to 20thDay
11%10%15%24%25%15%
247
21st to endDay
10%9%23%28%18%12%
180
December1st to 10thDay
20%16%13%23%18%10%
180
11th to 20thDay
26%11%21%18%16%8%
180
21st to endDay
22%13%20%25%16%4
198
January1st to 10thNight
21%8%15%29%23%5%
760
11th to 20thNight
22%7%14%32%21%5%
734
21st to endNight
19%5%14%33%25%4
792
February1st to 10thNight
19%7%14%33%24%3
720
11th to 20thNight
16%9%18%31%21%4
704
21st to endNight
17%10%22%31%18%2
592
March1st to 10thNight
22%12%17%27%20%4
720
11th to 20thNight
19%8%18%32%21%3
720
21st to endNight
17%8%26%29%16%3
792
April1st to 10thNight
13%9%29%28%18%3
720
11th to 20thNight
11%13%24%28%19%5%
711
21st to endNight
8%12%27%24%23%5%
720
May1st to 10thNight
9%7%24%29%27%4
560
11th to 20thNight
7%323%31%33%3
501
21st to endNight
7%11%21%30%26%4
389
June1st to 10thNight
8%6%23%34%27%2
360
11th to 20thNight
47%21%42%24%3
360
21st to endNight
4117%37%39%2
360
July1st to 10thNight
3115%34%41%6%
350
11th to 20thNight
317%31%48%11%
522
21st to endNight
46%34%45%11%
591
August1st to 10thNight
4113%33%39%10%
537
11th to 20thNight
219%35%45%9%
585
21st to endNight
5%17%34%46%7%
792
September1st to 10thNight
219%30%48%10%
720
11th to 20thNight
7%311%34%35%9%
720
21st to endNight
5%414%30%36%12%
720
October1st to 10thNight
7%415%30%33%11%
720
11th to 20thNight
10%312%28%40%8%
720
21st to endNight
11%411%26%35%12%
792
November1st to 10thNight
11%416%26%33%9%
740
11th to 20thNight
14%412%34%30%6%
760
21st to endNight
11%6%16%34%26%6%
760
December1st to 10thNight
23%5%15%29%23%6%
760
11th to 20thNight
26%7%14%29%20%4
760
21st to endNight
24%7%19%30%17%2
836
Page generated at 2024-01-11 01:22:39. Version ac07

Copyright 2024 Attilla Danko


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