Point Richmond
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Point Richmond clear sky chart from 2005-11-06 to 2024-01-12.

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%
23653
23%
74779
20%
23604
60%
23604
31%
44247

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
51%
756
17%
2537
15%
756
55%
756
22%
1651
January11th to 20thNight
54%
726
21%
2358
18%
726
60%
726
25%
1468
January21st to endNight
54%
792
24%
2574
24%
792
58%
792
25%
1604
February1st to 10thNight
55%
720
26%
2340
24%
720
62%
720
29%
1376
February11th to 20thNight
51%
700
23%
2211
20%
700
58%
700
27%
1343
February21st to endNight
50%
592
25%
1776
19%
592
59%
592
31%
1058
March1st to 10thNight
43%
720
17%
2003
13%
720
47%
720
23%
1380
March11th to 20thNight
48%
720
23%
1980
18%
720
53%
720
28%
1308
March21st to endNight
45%
792
18%
2156
11%
792
52%
792
30%
1379
April1st to 10thNight
45%
720
22%
1800
11%
720
50%
720
31%
1172
April11th to 20thNight
44%
711
26%
1779
11%
711
51%
711
36%
1092
April21st to endNight
50%
720
27%
1800
11%
720
56%
720
43%
1048
May1st to 10thNight
51%
622
25%
1702
13%
622
57%
622
41%
970
May11th to 20thNight
55%
488
21%
1551
14%
488
61%
488
32%
885
May21st to endNight
46%
388
21%
1552
16%
388
56%
388
24%
859
June1st to 10thNight
51%
360
20%
1440
17%
360
61%
360
28%
767
June11th to 20thNight
60%
360
30%
1440
30%
360
69%
360
40%
632
June21st to endNight
61%
360
25%
1440
28%
360
67%
360
33%
701
July1st to 10thNight
62%
350
23%
1400
28%
350
67%
350
36%
666
July11th to 20thNight
60%
509
21%
1553
18%
509
63%
509
40%
819
July21st to endNight
44%
591
19%
1674
16%
558
47%
558
27%
1019
August1st to 10thNight
49%
537
19%
1602
14%
534
52%
534
27%
976
August11th to 20thNight
57%
626
22%
1694
13%
626
59%
626
38%
1010
August21st to endNight
61%
792
24%
1980
14%
792
62%
792
40%
1237
September1st to 10thNight
71%
720
34%
1800
23%
720
73%
720
54%
989
September11th to 20thNight
60%
720
29%
1800
19%
720
65%
720
39%
1133
September21st to endNight
68%
720
34%
2055
30%
720
74%
720
52%
1019
October1st to 10thNight
65%
720
29%
2160
26%
720
73%
720
44%
1126
October11th to 20thNight
63%
720
31%
2160
31%
720
69%
720
38%
1200
October21st to endNight
65%
792
33%
2376
33%
792
70%
792
39%
1296
November1st to 10thNight
63%
740
29%
2243
27%
740
68%
740
36%
1276
November11th to 20thNight
62%
760
26%
2470
27%
760
66%
760
33%
1403
November21st to endNight
63%
760
26%
2645
27%
760
67%
760
34%
1399
December1st to 10thNight
54%
760
21%
2660
20%
760
59%
760
25%
1607
December11th to 20thNight
49%
760
17%
3242
19%
759
54%
759
15%
2276
December21st to endNight
43%
829
12%
4826
16%
817
51%
817
12%
3103

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
8%5%24423448%55%
74677
Night
10%6%35%5%3445%7%49%
75047
TransparencyDay
28%5%9%20%23%15%
74397
Night
34%6%9%18%20%13%
74849
SeeingDay
9%10%27%34%16%3
14254
Night
10%5%18%37%25%4
23669

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
18%9%36%5%2445%8%35%
1623
11th to 20thDay
14%5%3444446%6%48%
1630
21st to endDay
12%8%35%5%345%5%7%42%
1782
February1st to 10thDay
16%7%1443445%6%47%
1620
11th to 20thDay
12%6%25%435%46%9%44%
1638
21st to endDay
13%6%35%43435%6%49%
1480
March1st to 10thDay
15%6%35%5%3446%8%41%
1954
11th to 20thDay
15%7%35%5%35%45%8%39%
1980
21st to endDay
11%4345%35%46%9%47%
2200
April1st to 10thDay
13%5%35%425%45%8%45%
2160
11th to 20thDay
8%5%24323448%57%
2129
21st to endDay
432332445%10%59%
2160
May1st to 10thDay
45%24323446%62%
2255
11th to 20thDay
5%324324349%62%
2343
21st to endDay
46%2442445%8%58%
2723
June1st to 10thDay
5%5%2332345%9%58%
2520
11th to 20thDay
1323213348%70%
2520
21st to endDay
2324323338%68%
2520
July1st to 10thDay
15%233223410%65%
2520
11th to 20thDay
14244233410%61%
2350
21st to endDay
142332335%10%64%
2546
August1st to 10thDay
26%35%3233410%59%
2328
11th to 20thDay
1424423448%65%
2205
21st to endDay
16%25%423349%62%
2376
September1st to 10thDay
1323322247%71%
2160
11th to 20thDay
35%25%323349%61%
2160
21st to endDay
3312222237%73%
1900
October1st to 10thDay
4423323446%66%
1800
11th to 20thDay
6%5%24423436%61%
1800
21st to endDay
8%6%24312347%60%
1980
November1st to 10thDay
8%42442345%8%55%
1833
11th to 20thDay
10%7%36%5%3335%7%47%
1710
21st to endDay
10%5%2342346%6%53%
1530
December1st to 10thDay
14%7%35%3345%47%45%
1520
11th to 20thDay
27%9%36%5%23445%32%
1928
21st to endDay
20%9%35%5%345%5%8%33%
2794
January1st to 10thNight
17%7%35%5%35%5%5%7%39%
2537
11th to 20thNight
13%6%36%43445%6%46%
2358
21st to endNight
14%7%25%424447%46%
2574
February1st to 10thNight
15%6%24434446%50%
2340
11th to 20thNight
11%6%36%4345%5%8%47%
2209
21st to endNight
12%5%15%42445%6%52%
1776
March1st to 10thNight
17%7%35%5%34446%41%
2003
11th to 20thNight
15%6%345%345%5%7%43%
1980
21st to endNight
13%6%24423436%52%
2156
April1st to 10thNight
9%6%45%5%4345%8%49%
1800
11th to 20thNight
9%6%24423347%56%
1779
21st to endNight
433432335%8%61%
1800
May1st to 10thNight
46%37%42435%7%56%
1702
11th to 20thNight
45%345%34349%57%
1550
21st to endNight
5%7%36%5%34447%53%
1552
June1st to 10thNight
48%26%5%2445%10%50%
1440
11th to 20thNight
1435%433448%62%
1440
21st to endNight
27%26%5%23349%58%
1440
July1st to 10thNight
18%46%5%233410%54%
1440
11th to 20thNight
29%47%6%35%45%11%44%
1606
21st to endNight
111%6%11%9%46%45%10%33%
1773
August1st to 10thNight
311%5%9%7%45%45%9%39%
1611
11th to 20thNight
17%47%7%447%8%10%39%
1694
21st to endNight
29%46%5%3445%11%46%
1980
September1st to 10thNight
1435%42335%7%63%
1800
11th to 20thNight
47%36%6%34448%52%
1800
21st to endNight
26%25%323348%63%
2055
October1st to 10thNight
5%5%24323346%63%
2160
11th to 20thNight
6%6%3442345%7%57%
2160
21st to endNight
7%425%5%24347%57%
2376
November1st to 10thNight
7%6%35%323348%55%
2243
11th to 20thNight
10%6%25%42345%7%51%
2470
21st to endNight
9%42442345%6%57%
2645
December1st to 10thNight
16%6%26%423446%47%
2660
11th to 20thNight
29%9%3442345%6%32%
3276
21st to endNight
18%6%27%6%45%5%6%6%35%
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%7%14%17%10%4
1623
11th to 20thDay
39%5%11%16%18%12%
1630
21st to endDay
43%6%10%14%20%7%
1782
February1st to 10thDay
39%49%18%21%9%
1620
11th to 20thDay
38%5%10%19%22%6%
1647
21st to endDay
37%5%8%24%18%7%
1480
March1st to 10thDay
43%6%12%20%16%3
1954
11th to 20thDay
45%5%10%21%15%4
1980
21st to endDay
37%8%13%21%17%4
2200
April1st to 10thDay
39%6%13%19%19%4
2160
11th to 20thDay
29%5%15%23%21%6%
2132
21st to endDay
24%5%13%29%25%4
2160
May1st to 10thDay
23%5%10%27%28%7%
2255
11th to 20thDay
23%6%8%32%23%9%
2346
21st to endDay
27%6%15%26%23%4
2724
June1st to 10thDay
25%6%10%26%25%8%
2520
11th to 20thDay
13%410%22%34%16%
2520
21st to endDay
17%5%415%32%28%
2520
July1st to 10thDay
15%4411%26%40%
2451
11th to 20thDay
16%5%7%14%23%36%
2280
21st to endDay
14%3413%27%39%
2405
August1st to 10thDay
21%46%13%30%26%
2312
11th to 20thDay
16%3413%33%31%
2205
21st to endDay
18%2417%33%26%
2376
September1st to 10thDay
14%2311%30%39%
2160
11th to 20thDay
23%46%22%29%15%
2160
21st to endDay
15%26%22%32%23%
1900
October1st to 10thDay
20%37%17%31%23%
1800
11th to 20thDay
24%49%19%22%22%
1800
21st to endDay
25%49%21%23%18%
1980
November1st to 10thDay
28%5%10%27%19%12%
1833
11th to 20thDay
37%410%22%20%6%
1710
21st to endDay
31%411%19%24%11%
1530
December1st to 10thDay
38%6%10%20%17%8%
1520
11th to 20thDay
55%5%9%12%15%4
1928
21st to endDay
48%6%13%20%10%3
2794
January1st to 10thNight
44%5%13%20%11%5%
2537
11th to 20thNight
39%6%11%17%14%13%
2358
21st to endNight
41%5%11%14%18%11%
2574
February1st to 10thNight
38%39%19%20%11%
2340
11th to 20thNight
37%5%10%18%21%9%
2211
21st to endNight
34%5%11%27%19%5%
1776
March1st to 10thNight
45%6%10%17%16%4
2003
11th to 20thNight
42%5%8%22%18%6%
1980
21st to endNight
38%6%13%21%18%5%
2156
April1st to 10thNight
37%6%13%19%20%5%
1800
11th to 20thNight
30%5%12%24%19%8%
1779
21st to endNight
24%6%12%29%22%6%
1800
May1st to 10thNight
29%48%25%24%11%
1702
11th to 20thNight
29%9%9%22%23%7%
1551
21st to endNight
33%8%12%21%22%4
1552
June1st to 10thNight
30%8%10%19%26%8%
1440
11th to 20thNight
21%48%19%32%16%
1440
21st to endNight
23%9%5%12%26%25%
1440
July1st to 10thNight
23%8%46%25%34%
1400
11th to 20thNight
25%6%9%11%18%30%
1553
21st to endNight
39%5%7%7%15%27%
1674
August1st to 10thNight
39%5%7%9%20%19%
1602
11th to 20thNight
31%5%6%9%22%26%
1694
21st to endNight
32%5%6%10%24%23%
1980
September1st to 10thNight
21%46%6%27%36%
1800
11th to 20thNight
30%8%6%18%23%15%
1800
21st to endNight
19%45%20%29%23%
2055
October1st to 10thNight
23%5%7%17%24%24%
2160
11th to 20thNight
28%5%6%18%19%24%
2160
21st to endNight
27%5%7%20%21%20%
2376
November1st to 10thNight
30%5%10%25%17%13%
2243
11th to 20thNight
33%5%11%25%19%8%
2470
21st to endNight
29%5%10%21%23%13%
2645
December1st to 10thNight
39%5%10%17%17%11%
2660
11th to 20thNight
53%5%9%14%15%4
3276
21st to endNight
48%7%15%16%11%4
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
25%9%30%20%14%2
284
11th to 20thDay
18%10%20%35%13%3
344
21st to endDay
14%9%27%30%18%3
374
February1st to 10thDay
20%11%18%30%19%2
340
11th to 20thDay
18%16%26%25%14%2
363
21st to endDay
13%15%26%30%15%1
346
March1st to 10thDay
21%16%30%20%10%3
420
11th to 20thDay
17%17%27%20%15%4
420
21st to endDay
13%17%31%27%10%1
462
April1st to 10thDay
18%14%32%23%10%3
420
11th to 20thDay
14%18%33%24%8%4
412
21st to endDay
7%20%29%29%11%5%
420
May1st to 10thDay
9%17%30%31%11%1
423
11th to 20thDay
9%15%33%31%12%1
448
21st to endDay
7%12%32%34%12%2
485
June1st to 10thDay
8%12%33%32%13%3
450
11th to 20thDay
413%35%37%10%2
450
21st to endDay
16%34%43%14%1
450
July1st to 10thDay
2432%48%13%
446
11th to 20thDay
223%55%18%2
444
21st to endDay
1130%48%16%3
487
August1st to 10thDay
25%30%48%13%3
447
11th to 20thDay
2328%46%17%5%
437
21st to endDay
2224%49%20%3
495
September1st to 10thDay
2421%46%20%7%
450
11th to 20thDay
49%26%39%16%7%
450
21st to endDay
38%25%33%26%6%
450
October1st to 10thDay
47%27%32%21%8%
450
11th to 20thDay
6%9%21%29%27%8%
450
21st to endDay
9%7%23%28%26%6%
495
November1st to 10thDay
11%9%19%24%32%5%
429
11th to 20thDay
7%10%17%35%26%5%
270
21st to endDay
12%8%26%34%18%2
185
December1st to 10thDay
17%14%22%27%16%5%
180
11th to 20thDay
17%13%26%29%14%1
180
21st to endDay
19%10%30%28%12%1
198
January1st to 10thNight
19%5%15%31%24%5%
760
11th to 20thNight
14%6%16%36%23%4
726
21st to endNight
17%5%14%36%24%4
792
February1st to 10thNight
17%6%14%37%23%4
720
11th to 20thNight
13%9%18%34%22%4
704
21st to endNight
15%9%20%32%22%2
592
March1st to 10thNight
19%8%22%28%20%3
720
11th to 20thNight
16%7%20%31%22%3
720
21st to endNight
16%7%27%32%17%1
792
April1st to 10thNight
13%8%25%35%17%3
720
11th to 20thNight
10%13%26%29%19%3
711
21st to endNight
6%9%29%32%21%3
720
May1st to 10thNight
7%5%26%39%21%2
622
11th to 20thNight
6%224%39%25%3
488
21st to endNight
6%8%29%37%18%3
389
June1st to 10thNight
4429%44%18%1
360
11th to 20thNight
1424%53%16%1
360
21st to endNight
4323%44%26%1
360
July1st to 10thNight
318%51%27%1
350
11th to 20thNight
3113%51%28%5%
509
21st to endNight
3216%44%32%3
591
August1st to 10thNight
6%219%42%28%4
537
11th to 20thNight
3119%45%28%4
626
21st to endNight
5%114%47%30%4
792
September1st to 10thNight
2114%41%35%8%
720
11th to 20thNight
6%217%41%30%4
720
21st to endNight
4315%37%34%7%
720
October1st to 10thNight
7%316%36%31%7%
720
11th to 20thNight
8%5%14%33%34%7%
720
21st to endNight
8%412%32%34%10%
792
November1st to 10thNight
8%5%14%31%34%8%
740
11th to 20thNight
12%314%35%30%6%
760
21st to endNight
10%6%13%39%27%5%
760
December1st to 10thNight
16%6%16%34%24%5%
760
11th to 20thNight
23%6%16%32%20%3
760
21st to endNight
20%8%22%30%19%1
836
Page generated at 2024-01-09 04:14:45. Version ac07

Copyright 2024 Attilla Danko


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