Point Richmond
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Point Richmond clear sky chart from 2005-11-05 to 2017-09-18.

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
50%
15372
23%
46926
17%
15336
57%
15336
28%
27607

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 15thNight
49%
716
18%
2377
14%
716
56%
716
22%
1443
January16th to endNight
46%
768
24%
2496
19%
768
55%
768
21%
1551
February1st to 15thNight
46%
700
22%
2288
20%
700
52%
700
21%
1441
February16th to endNight
42%
632
21%
1912
14%
632
53%
632
22%
1235
March1st to 15thNight
43%
720
17%
1995
13%
720
47%
720
22%
1337
March16th to endNight
42%
768
20%
2097
11%
768
50%
768
25%
1364
April1st to 15thNight
41%
719
22%
1799
11%
719
47%
719
28%
1177
April16th to endNight
44%
720
24%
1800
10%
720
50%
720
35%
1071
May1st to 15thNight
52%
593
23%
1673
14%
593
57%
593
37%
916
May16th to endNight
44%
402
21%
1525
14%
402
55%
402
24%
798
June1st to 15thNight
47%
360
20%
1440
17%
360
57%
360
26%
739
June16th to endNight
60%
360
30%
1440
26%
360
74%
360
37%
608
July1st to 15thNight
57%
387
23%
1407
24%
387
62%
387
35%
661
July16th to endNight
41%
564
20%
1593
14%
531
49%
531
24%
947
August1st to 15thNight
49%
540
21%
1613
15%
537
51%
537
26%
967
August16th to endNight
59%
764
25%
1910
12%
764
61%
764
37%
1188
September1st to 15thNight
65%
720
31%
1800
20%
720
67%
720
43%
1049
September16th to endNight
65%
667
34%
1835
25%
667
73%
667
47%
954
October1st to 15thNight
59%
660
28%
1980
26%
660
66%
660
38%
1067
October16th to endNight
57%
704
29%
2112
25%
704
67%
704
32%
1202
November1st to 15thNight
58%
700
27%
2175
26%
700
63%
700
34%
1214
November16th to endNight
48%
720
24%
2451
22%
720
56%
720
25%
1379
December1st to 15thNight
43%
720
20%
2520
15%
720
50%
720
18%
1603
December16th to endNight
40%
768
20%
2688
15%
768
49%
768
20%
1696

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%5%24323347%55%
47869
Night
9%6%25%423347%48%
47114
TransparencyDay
29%49%19%23%14%
47557
Night
34%49%18%20%12%
46927
SeeingDay
9%17%25%30%13%3
6027
Night
10%17%12%29%25%5%
15382

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 15thDay
15%6%34323446%43%
1558
16th to endDay
14%6%3443445%5%44%
1728
February1st to 15thDay
16%7%13424346%42%
1576
16th to endDay
16%7%35%32446%7%38%
1562
March1st to 15thDay
14%6%25%5%3345%8%40%
1962
16th to endDay
12%435%5%36%45%8%41%
2127
April1st to 15thDay
12%5%3432445%7%44%
2149
16th to endDay
5%314323348%59%
2160
May1st to 15thDay
3423123447%62%
2275
16th to endDay
5%5%24313348%57%
2587
June1st to 15thDay
5%423323348%59%
2520
16th to endDay
2212212338%69%
2520
July1st to 15thDay
15%23312339%64%
2466
16th to endDay
1423212349%62%
2468
August1st to 15thDay
15%24313248%61%
2337
16th to endDay
5%14312338%63%
2292
September1st to 15thDay
2423212237%66%
2160
16th to endDay
3313213226%69%
1847
October1st to 15thDay
6%424313446%60%
1650
16th to endDay
9%6%13312336%57%
1760
November1st to 15thDay
8%5%24423347%52%
1683
16th to endDay
12%8%34413345%47%
1506
December1st to 15thDay
16%8%35%224436%41%
1440
16th to endDay
19%7%23423446%41%
1536
January1st to 15thNight
14%6%2432445%7%45%
2377
16th to endNight
15%7%24323336%46%
2496
February1st to 15thNight
14%6%25%434435%44%
2276
16th to endNight
15%5%25%3245%6%8%41%
1912
March1st to 15thNight
15%6%25%5%24446%42%
1995
16th to endNight
13%5%24423336%47%
2097
April1st to 15thNight
10%5%3443335%8%47%
1799
16th to endNight
6%323323247%59%
1800
May1st to 15thNight
3435%323247%58%
1673
16th to endNight
46%24434348%53%
1524
June1st to 15thNight
36%26%42345%9%50%
1440
16th to endNight
1314322349%63%
1440
July1st to 15thNight
16%45%5%244412%47%
1491
16th to endNight
110%5%11%7%35%45%11%32%
1701
August1st to 15thNight
39%49%7%4447%12%33%
1622
16th to endNight
29%46%5%3445%11%41%
1910
September1st to 15thNight
25%35%42445%8%53%
1800
16th to endNight
25%15%412248%59%
1835
October1st to 15thNight
6%5%24312346%58%
1980
16th to endNight
7%41442335%6%53%
2112
November1st to 15thNight
8%5%23213347%56%
2175
16th to endNight
9%5%24422345%53%
2451
December1st to 15thNight
19%5%24323445%43%
2520
16th to endNight
17%5%25%324346%44%
2688

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 15thDay
40%5%13%16%16%7%
1558
16th to endDay
44%49%11%18%11%
1728
February1st to 15thDay
43%49%18%20%3
1576
16th to endDay
44%5%10%23%12%3
1562
March1st to 15thDay
43%5%12%19%13%5%
1962
16th to endDay
42%6%13%19%15%3
2127
April1st to 15thDay
40%5%14%18%18%2
2149
16th to endDay
26%413%26%22%6%
2160
May1st to 15thDay
21%39%30%26%8%
2275
16th to endDay
27%5%12%27%21%6%
2591
June1st to 15thDay
25%5%9%22%23%13%
2520
16th to endDay
14%25%18%34%24%
2520
July1st to 15thDay
17%2411%24%39%
2321
16th to endDay
17%2411%25%38%
2313
August1st to 15thDay
20%2411%32%28%
2321
16th to endDay
17%1318%36%22%
2292
September1st to 15thDay
18%2415%30%28%
2160
16th to endDay
18%25%24%29%19%
1847
October1st to 15thDay
25%28%20%27%15%
1650
16th to endDay
28%38%24%22%12%
1760
November1st to 15thDay
32%412%29%13%7%
1683
16th to endDay
38%49%18%22%5%
1506
December1st to 15thDay
44%5%9%18%18%4
1440
16th to endDay
44%5%11%17%15%5%
1536
January1st to 15thNight
38%5%12%19%15%8%
2377
16th to endNight
40%48%14%16%15%
2496
February1st to 15thNight
42%410%18%17%7%
2288
16th to endNight
41%5%12%23%14%2
1912
March1st to 15thNight
43%411%19%14%5%
1995
16th to endNight
40%5%11%19%18%4
2097
April1st to 15thNight
36%5%14%19%19%3
1799
16th to endNight
27%412%25%21%8%
1800
May1st to 15thNight
26%49%23%25%11%
1674
16th to endNight
30%5%12%24%20%6%
1525
June1st to 15thNight
28%6%10%18%22%13%
1440
16th to endNight
20%2315%33%24%
1440
July1st to 15thNight
24%338%25%35%
1407
16th to endNight
39%25%8%16%27%
1593
August1st to 15thNight
40%2310%22%21%
1613
16th to endNight
34%2310%27%22%
1910
September1st to 15thNight
27%249%27%28%
1800
16th to endNight
21%35%22%27%20%
1835
October1st to 15thNight
26%37%21%22%17%
1980
16th to endNight
30%46%22%20%14%
2112
November1st to 15thNight
30%412%28%16%7%
2175
16th to endNight
33%49%23%21%8%
2451
December1st to 15thNight
43%5%8%16%18%6%
2520
16th to endNight
42%5%11%15%17%7%
2688

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 15thDay
24%16%22%20%16%
186
16th to endDay
17%21%16%27%13%2
256
February1st to 15thDay
19%22%21%20%14%1
236
16th to endDay
18%20%22%22%13%1
235
March1st to 15thDay
18%25%24%14%12%4
270
16th to endDay
14%27%27%20%8%1
288
April1st to 15thDay
15%30%25%19%7%1
269
16th to endDay
11%34%22%23%5%2
270
May1st to 15thDay
6%26%33%27%6%
288
16th to endDay
10%22%24%29%11%2
330
June1st to 15thDay
8%21%33%27%6%2
315
16th to endDay
213%28%38%13%2
315
July1st to 15thDay
28%23%47%16%
305
16th to endDay
111%24%44%13%5%
327
August1st to 15thDay
39%26%43%14%2
315
16th to endDay
6%23%45%18%4
332
September1st to 15thDay
37%22%41%18%6%
315
16th to endDay
314%23%29%22%7%
264
October1st to 15thDay
7%14%24%32%14%6%
255
16th to endDay
13%14%27%25%17%2
272
November1st to 15thDay
7%13%20%21%31%4
189
16th to endDay
15%12%26%30%14%
71
December1st to 15thDay
23%15%36%13%10%1
60
16th to endDay
10%20%23%25%18%1
64
January1st to 15thNight
14%18%8%28%22%7%
720
16th to endNight
18%19%9%24%22%6%
768
February1st to 15thNight
15%20%10%28%20%4
704
16th to endNight
15%19%16%25%19%4
632
March1st to 15thNight
15%22%12%21%23%3
720
16th to endNight
13%21%16%27%18%1
768
April1st to 15thNight
10%23%18%26%17%2
719
16th to endNight
7%23%19%25%19%3
720
May1st to 15thNight
5%18%15%37%21%2
594
16th to endNight
6%21%19%31%17%3
403
June1st to 15thNight
418%17%38%18%2
360
16th to endNight
216%12%42%24%
360
July1st to 15thNight
311%8%36%36%3
387
16th to endNight
317%6%30%36%4
564
August1st to 15thNight
6%10%11%32%35%4
540
16th to endNight
6%8%8%38%32%5%
764
September1st to 15thNight
5%9%8%30%38%7%
720
16th to endNight
49%9%32%35%8%
667
October1st to 15thNight
8%12%11%27%32%7%
660
16th to endNight
9%12%10%26%30%11%
704
November1st to 15thNight
8%15%12%25%30%8%
700
16th to endNight
11%20%10%26%24%6%
720
December1st to 15thNight
18%21%11%27%18%3
720
16th to endNight
15%21%16%26%18%1
768
Page generated at 2017-09-19 04:32:33. Version ac04

Copyright 2017 A. Danko


Point Richmond Clear Sky Chart | Charts Home