Richmond
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Richmond clear sky chart from 2005-11-05 to 2018-02-22.

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
39%
16052
22%
48943
12%
16016
49%
16016
25%
30696

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
25%
776
24%
2545
10%
776
42%
776
20%
1548
January16th to endNight
21%
832
24%
2704
8%
832
39%
832
23%
1650
February1st to 15thNight
24%
761
20%
2482
9%
761
40%
761
22%
1516
February16th to endNight
21%
659
27%
1991
9%
659
42%
659
23%
1216
March1st to 15thNight
26%
720
24%
1980
11%
720
39%
720
25%
1266
March16th to endNight
26%
768
21%
2103
9%
768
37%
768
23%
1418
April1st to 15thNight
26%
718
22%
1796
5%
718
37%
718
30%
1172
April16th to endNight
35%
720
20%
1800
7%
720
41%
720
32%
1183
May1st to 15thNight
36%
600
16%
1680
7%
600
42%
600
25%
1142
May16th to endNight
54%
422
19%
1544
15%
422
61%
422
25%
913
June1st to 15thNight
58%
360
16%
1440
17%
360
62%
360
24%
840
June16th to endNight
59%
360
17%
1440
17%
360
65%
360
24%
837
July1st to 15thNight
57%
409
14%
1429
14%
409
59%
409
23%
917
July16th to endNight
68%
564
17%
1595
12%
531
72%
531
32%
991
August1st to 15thNight
63%
542
17%
1612
12%
539
64%
539
28%
1059
August16th to endNight
60%
764
18%
1910
12%
764
61%
764
30%
1304
September1st to 15thNight
60%
720
23%
1800
16%
720
62%
720
31%
1213
September16th to endNight
49%
717
20%
1981
16%
717
52%
717
25%
1351
October1st to 15thNight
47%
720
24%
2160
20%
720
54%
720
26%
1372
October16th to endNight
39%
768
32%
2304
21%
768
55%
768
31%
1346
November1st to 15thNight
40%
760
24%
2359
15%
760
52%
760
28%
1431
November16th to endNight
37%
780
26%
2646
17%
780
51%
780
25%
1527
December1st to 15thNight
31%
780
20%
2730
11%
780
43%
780
21%
1683
December16th to endNight
29%
832
23%
2912
12%
832
44%
832
19%
1801

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
13%5%25%43445%7%42%
49291
Night
14%5%2442445%7%44%
49133
Cloud CoverDay
13%5%25%43445%7%42%
49301
Night
14%5%2442445%7%44%
49137
TransparencyDay
39%5%11%22%17%3
48998
Night
39%5%10%22%18%4
48944
SeeingDay
18%8%25%25%16%6%
6222
Night
17%10%27%30%13%1
16060

By Month

Percentage Cloud Cover NE (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%245%23445%44%
1720
16th to endDay
16%6%23422346%46%
1872
February1st to 15thDay
16%6%25%423445%41%
1710
16th to endDay
15%5%245%35%36%6%41%
1626
March1st to 15thDay
15%424424348%46%
1969
16th to endDay
18%5%26%424346%41%
2121
April1st to 15thDay
11%424424337%51%
2152
16th to endDay
15%5%25%423446%44%
2160
May1st to 15thDay
16%5%25%43446%7%37%
2280
16th to endDay
13%4245%3446%8%41%
2570
June1st to 15thDay
12%314435%6%6%10%41%
2520
16th to endDay
7%425%5%35%6%6%11%40%
2520
July1st to 15thDay
8%5%26%6%37%6%6%10%35%
2442
16th to endDay
5%315%7%47%6%8%10%38%
2465
August1st to 15thDay
11%6%27%6%35%5%7%9%33%
2324
16th to endDay
11%425%5%45%6%7%9%37%
2292
September1st to 15thDay
12%5%245%35%46%6%44%
2160
16th to endDay
17%6%26%5%3345%7%38%
1974
October1st to 15thDay
18%5%2442333448%
1800
16th to endDay
13%414323335%54%
1920
November1st to 15thDay
16%415%324335%47%
1829
16th to endDay
13%424323345%53%
1641
December1st to 15thDay
16%5%143225%5%6%44%
1560
16th to endDay
18%6%26%423335%41%
1664
January1st to 15thNight
16%5%23324446%46%
2545
16th to endNight
17%6%2332344446%
2704
February1st to 15thNight
16%5%24423446%44%
2480
16th to endNight
14%5%25%5%23346%47%
1991
March1st to 15thNight
14%5%1442435%6%46%
1968
16th to endNight
18%5%25%424346%41%
2103
April1st to 15thNight
11%5%35%5%33348%47%
1796
16th to endNight
14%6%24424347%46%
1800
May1st to 15thNight
16%6%3443445%8%39%
1680
16th to endNight
13%4135%3346%7%45%
1543
June1st to 15thNight
8%3345%35%5%7%10%40%
1440
16th to endNight
8%325%5%35%5%6%9%43%
1440
July1st to 15thNight
8%426%6%46%45%7%41%
1515
16th to endNight
5%4245%36%6%9%9%41%
1703
August1st to 15thNight
8%426%7%35%5%7%9%37%
1623
16th to endNight
11%5%25%5%35%6%6%9%37%
1910
September1st to 15thNight
13%425%4345%6%6%43%
1800
16th to endNight
17%6%25%42435%6%39%
1981
October1st to 15thNight
17%425%5%23336%45%
2160
16th to endNight
15%413322345%52%
2304
November1st to 15thNight
15%6%14323335%49%
2359
16th to endNight
14%423324445%49%
2646
December1st to 15thNight
16%6%24424346%42%
2730
16th to endNight
17%6%25%323346%42%
2912

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 15thDay
15%6%245%23445%44%
1720
16th to endDay
16%6%23412446%45%
1872
February1st to 15thDay
16%6%25%43335%6%41%
1710
16th to endDay
15%5%235%35%46%6%41%
1626
March1st to 15thDay
14%42442335%7%46%
1980
16th to endDay
18%6%26%5%23346%41%
2120
April1st to 15thDay
11%4245%23336%51%
2152
16th to endDay
15%5%26%423346%44%
2160
May1st to 15thDay
16%6%25%435%46%6%37%
2280
16th to endDay
13%4245%35%5%6%9%41%
2570
June1st to 15thDay
12%3145%35%6%6%10%41%
2520
16th to endDay
7%426%5%35%6%6%10%40%
2520
July1st to 15thDay
8%5%26%6%46%6%6%10%35%
2442
16th to endDay
5%325%7%46%6%8%11%38%
2465
August1st to 15thDay
11%6%27%6%45%6%7%9%33%
2324
16th to endDay
11%416%6%35%6%8%9%36%
2292
September1st to 15thDay
12%5%24435%46%6%44%
2160
16th to endDay
17%6%26%5%33447%38%
1974
October1st to 15thDay
18%5%2432332448%
1800
16th to endDay
13%414323335%54%
1920
November1st to 15thDay
16%5%14314335%48%
1829
16th to endDay
12%424323245%53%
1641
December1st to 15thDay
16%6%143225%5%6%45%
1560
16th to endDay
18%6%25%433335%41%
1664
January1st to 15thNight
16%5%23324446%45%
2545
16th to endNight
17%6%2432344446%
2704
February1st to 15thNight
16%5%24424445%44%
2473
16th to endNight
14%425%5%23246%47%
1991
March1st to 15thNight
14%5%1442445%6%46%
1980
16th to endNight
18%5%25%5%24346%41%
2103
April1st to 15thNight
11%5%25%5%23348%46%
1796
16th to endNight
15%5%24424347%46%
1800
May1st to 15thNight
16%6%25%434448%38%
1679
16th to endNight
13%4145%345%5%8%45%
1543
June1st to 15thNight
9%3245%35%6%7%10%40%
1440
16th to endNight
8%325%5%35%5%7%9%43%
1440
July1st to 15thNight
8%426%6%36%5%5%8%41%
1515
16th to endNight
5%4245%27%6%8%9%41%
1703
August1st to 15thNight
8%436%6%35%6%7%9%37%
1623
16th to endNight
11%6%25%435%5%7%9%37%
1910
September1st to 15thNight
12%5%25%5%345%6%6%43%
1800
16th to endNight
17%7%25%42435%6%39%
1981
October1st to 15thNight
17%425%5%23336%45%
2160
16th to endNight
15%413312345%52%
2304
November1st to 15thNight
15%6%24424335%49%
2359
16th to endNight
14%423324446%49%
2646
December1st to 15thNight
15%6%24424346%42%
2730
16th to endNight
17%6%35%323346%42%
2912

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%49%22%17%5%
1721
16th to endDay
39%310%23%17%5%
1872
February1st to 15thDay
43%38%23%17%3
1712
16th to endDay
42%49%22%18%3
1626
March1st to 15thDay
37%410%23%17%5%
1980
16th to endDay
44%49%19%17%4
2121
April1st to 15thDay
34%310%24%20%6%
2152
16th to endDay
40%310%18%17%8%
2160
May1st to 15thDay
44%5%13%19%14%1
2280
16th to endDay
38%6%15%25%13%1
2574
June1st to 15thDay
35%8%15%25%13%1
2520
16th to endDay
35%8%16%21%16%2
2520
July1st to 15thDay
40%8%15%18%12%3
2299
16th to endDay
36%9%15%21%15%1
2310
August1st to 15thDay
43%8%13%20%12%1
2311
16th to endDay
40%7%15%22%12%1
2292
September1st to 15thDay
38%7%12%17%20%3
2160
16th to endDay
45%5%8%20%18%1
1974
October1st to 15thDay
41%46%23%19%3
1800
16th to endDay
32%36%26%24%5%
1920
November1st to 15thDay
39%38%22%20%6%
1829
16th to endDay
33%37%24%25%4
1641
December1st to 15thDay
38%49%25%15%5%
1560
16th to endDay
45%48%23%15%1
1664
January1st to 15thNight
39%49%19%19%7%
2545
16th to endNight
40%39%24%17%4
2704
February1st to 15thNight
40%38%24%18%4
2482
16th to endNight
38%38%25%19%5%
1991
March1st to 15thNight
38%5%7%27%18%3
1980
16th to endNight
44%47%22%17%3
2103
April1st to 15thNight
37%49%21%21%5%
1796
16th to endNight
38%411%19%18%7%
1800
May1st to 15thNight
43%5%14%20%13%2
1680
16th to endNight
36%7%14%26%13%1
1545
June1st to 15thNight
35%8%16%22%15%1
1440
16th to endNight
34%8%15%18%19%3
1440
July1st to 15thNight
41%8%14%19%13%3
1429
16th to endNight
32%9%17%24%14%1
1595
August1st to 15thNight
38%8%15%21%14%
1612
16th to endNight
39%8%14%22%13%1
1910
September1st to 15thNight
38%7%13%19%17%4
1800
16th to endNight
44%5%9%17%19%3
1981
October1st to 15thNight
41%48%22%19%4
2160
16th to endNight
33%37%24%25%5%
2304
November1st to 15thNight
38%38%18%23%7%
2359
16th to endNight
35%46%23%23%6%
2646
December1st to 15thNight
42%39%21%17%3
2730
16th to endNight
43%310%23%15%3
2912

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
22%24%36%10%5%
129
16th to endDay
27%22%34%11%2
144
February1st to 15thDay
32%27%34%5%
135
16th to endDay
19%14%39%23%2
247
March1st to 15thDay
20%18%30%24%6%
270
16th to endDay
20%15%36%18%7%2
288
April1st to 15thDay
17%11%31%26%11%2
270
16th to endDay
23%8%27%26%9%4
270
May1st to 15thDay
25%12%28%19%9%4
288
16th to endDay
20%421%26%21%5%
331
June1st to 15thDay
13%6%22%28%20%9%
315
16th to endDay
11%5%24%36%17%4
315
July1st to 15thDay
11%119%37%23%6%
305
16th to endDay
7%18%30%30%12%
326
August1st to 15thDay
16%215%25%31%8%
313
16th to endDay
10%112%34%25%15%
332
September1st to 15thDay
15%419%24%22%13%
315
16th to endDay
26%318%22%18%10%
314
October1st to 15thDay
26%417%25%19%7%
315
16th to endDay
12%9%29%26%16%5%
336
November1st to 15thDay
21%7%24%25%16%3
307
16th to endDay
14%12%35%22%12%1
171
December1st to 15thDay
23%11%38%13%12%1
90
16th to endDay
25%17%35%18%3
96
January1st to 15thNight
20%17%32%23%5%
780
16th to endNight
21%14%36%24%1
832
February1st to 15thNight
21%14%35%26%1
764
16th to endNight
18%20%35%22%2
659
March1st to 15thNight
19%16%35%24%4
720
16th to endNight
20%13%34%24%6%
768
April1st to 15thNight
14%17%38%24%4
718
16th to endNight
19%8%34%26%11%
720
May1st to 15thNight
18%9%32%30%9%
600
16th to endNight
14%419%40%18%2
423
June1st to 15thNight
10%319%40%24%2
360
16th to endNight
7%421%44%22%
360
July1st to 15thNight
9%219%38%27%1
409
16th to endNight
7%114%39%29%7%
564
August1st to 15thNight
9%112%45%28%3
542
16th to endNight
13%212%36%31%4
764
September1st to 15thNight
15%114%36%28%3
720
16th to endNight
20%317%31%24%2
717
October1st to 15thNight
20%6%20%27%21%3
720
16th to endNight
17%11%28%25%15%1
768
November1st to 15thNight
18%8%27%30%13%2
760
16th to endNight
16%13%28%30%10%
780
December1st to 15thNight
19%11%32%25%9%
780
16th to endNight
20%14%31%30%4
832
Page generated at 2018-02-23 11:21:35. Version ac04

Copyright 2018 A. Danko


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