York River State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the York River State Park clear sky chart from 2005-11-06 to 2024-01-16.

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
36%
23727
14%
74684
7%
23680
43%
23680
13%
55935

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
19%
757
15%
2550
5%
757
32%
757
10%
1898
January11th to 20thNight
22%
744
13%
2417
4%
744
33%
744
9%
1893
January21st to endNight
22%
792
17%
2574
6%
792
35%
792
11%
1915
February1st to 10thNight
18%
720
13%
2340
5%
720
30%
720
11%
1760
February11th to 20thNight
13%
700
13%
2166
3%
700
26%
700
10%
1644
February21st to endNight
18%
592
17%
1776
6%
592
31%
592
11%
1345
March1st to 10thNight
23%
720
17%
2028
6%
720
35%
720
16%
1480
March11th to 20thNight
21%
720
12%
1980
5%
720
29%
720
11%
1562
March21st to endNight
20%
792
13%
2129
5%
792
27%
792
12%
1680
April1st to 10thNight
19%
720
14%
1800
2%
720
28%
720
15%
1392
April11th to 20thNight
28%
711
18%
1775
5%
711
35%
711
19%
1322
April21st to endNight
31%
720
15%
1800
6%
720
35%
720
17%
1382
May1st to 10thNight
26%
698
11%
1778
3%
698
31%
698
13%
1408
May11th to 20thNight
38%
456
13%
1517
7%
456
43%
456
10%
1200
May21st to endNight
52%
388
14%
1551
14%
388
55%
388
12%
1138
June1st to 10thNight
53%
360
13%
1440
14%
360
57%
360
12%
1039
June11th to 20thNight
52%
360
11%
1440
11%
360
56%
360
11%
1074
June21st to endNight
54%
360
12%
1440
13%
360
57%
360
11%
1067
July1st to 10thNight
57%
350
11%
1400
13%
350
58%
350
11%
1054
July11th to 20thNight
68%
474
11%
1518
9%
474
69%
474
16%
1120
July21st to endNight
57%
591
10%
1672
7%
558
60%
558
14%
1315
August1st to 10thNight
60%
537
10%
1600
7%
534
61%
534
15%
1226
August11th to 20thNight
56%
674
11%
1738
7%
674
57%
674
15%
1407
August21st to endNight
59%
792
8%
1980
4%
792
60%
792
15%
1594
September1st to 10thNight
57%
720
17%
1800
10%
720
60%
720
20%
1379
September11th to 20thNight
57%
720
19%
1800
13%
720
60%
720
20%
1379
September21st to endNight
39%
720
11%
2042
8%
720
43%
720
14%
1598
October1st to 10thNight
46%
720
15%
2160
12%
720
52%
720
16%
1618
October11th to 20thNight
39%
720
17%
2160
11%
720
48%
720
14%
1631
October21st to endNight
35%
792
18%
2376
11%
792
44%
792
15%
1759
November1st to 10thNight
39%
740
16%
2297
9%
740
48%
740
16%
1654
November11th to 20thNight
34%
760
15%
2470
10%
760
43%
760
12%
1853
November21st to endNight
37%
760
15%
2570
10%
760
45%
760
12%
1904
December1st to 10thNight
24%
760
15%
2660
5%
760
37%
760
10%
1985
December11th to 20thNight
26%
760
16%
3178
7%
759
38%
759
10%
2264
December21st to endNight
29%
827
11%
4762
6%
817
40%
817
7%
2996

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%6%25%5%35%5%6%8%43%
74705
Night
14%6%25%5%3445%7%44%
75111
TransparencyDay
25%38%8%15%11%2
74418
Night
26%37%8%15%12%2
74917
SeeingDay
19%13%29%23%11%4
14055
Night
18%11%29%29%12%2
23743

By Month

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 10thDay
15%6%25%5%3345%5%46%
1612
11th to 20thDay
15%7%35%434446%44%
1671
21st to endDay
15%7%35%42335%5%47%
1782
February1st to 10thDay
13%9%35%436%5%5%8%39%
1620
11th to 20thDay
20%5%34423435%46%
1682
21st to endDay
17%8%26%6%36%5%5%6%37%
1480
March1st to 10thDay
14%5%25%423446%51%
1930
11th to 20thDay
17%6%25%5%335%5%6%44%
1980
21st to endDay
16%6%26%5%45%45%6%41%
2226
April1st to 10thDay
12%5%34424448%51%
2160
11th to 20thDay
11%6%35%5%35%447%48%
2134
21st to endDay
14%5%35%5%35%45%7%44%
2160
May1st to 10thDay
13%7%35%5%45%5%48%42%
2197
11th to 20thDay
16%6%25%5%35%5%6%7%40%
2375
21st to endDay
14%5%24435%5%6%9%42%
2725
June1st to 10thDay
10%425%5%36%6%6%11%42%
2520
11th to 20thDay
11%5%25%5%45%5%7%9%41%
2520
21st to endDay
8%425%6%46%6%8%12%39%
2520
July1st to 10thDay
7%5%26%7%46%6%9%10%38%
2520
11th to 20thDay
6%325%6%47%8%8%12%39%
2387
21st to endDay
7%326%7%5%7%9%8%12%34%
2547
August1st to 10thDay
10%6%25%6%5%6%7%9%9%34%
2327
11th to 20thDay
12%5%35%6%47%7%7%9%35%
2143
21st to endDay
11%436%6%35%5%7%10%39%
2376
September1st to 10thDay
13%5%25%5%35%5%6%8%42%
2160
11th to 20thDay
12%6%36%6%345%5%7%41%
2160
21st to endDay
19%7%35%5%45%45%6%37%
1913
October1st to 10thDay
16%7%25%43445%7%44%
1800
11th to 20thDay
15%5%24423446%50%
1800
21st to endDay
13%5%25%5%33445%52%
1980
November1st to 10thDay
13%5%35%323447%52%
1780
11th to 20thDay
14%6%25%323346%51%
1710
21st to endDay
15%4145%2335%6%52%
1606
December1st to 10thDay
17%7%245%2445%7%43%
1520
11th to 20thDay
16%6%24413245%53%
1910
21st to endDay
16%8%24434446%44%
2772
January1st to 10thNight
15%6%35%5%24446%47%
2550
11th to 20thNight
16%7%36%5%35%45%6%39%
2417
21st to endNight
16%6%3442345%5%48%
2574
February1st to 10thNight
17%8%35%43445%6%41%
2340
11th to 20thNight
20%6%34434446%41%
2164
21st to endNight
18%7%25%422346%46%
1776
March1st to 10thNight
14%5%35%424446%50%
2028
11th to 20thNight
17%7%25%435%5%6%7%39%
1980
21st to endNight
15%6%36%6%3445%6%42%
2129
April1st to 10thNight
14%7%35%5%4346%8%42%
1800
11th to 20thNight
12%6%2442335%9%48%
1775
21st to endNight
15%6%244235%6%8%44%
1800
May1st to 10thNight
13%7%36%6%45%5%5%8%39%
1778
11th to 20thNight
14%7%26%5%45%6%5%8%39%
1517
21st to endNight
15%435%5%35%45%9%43%
1550
June1st to 10thNight
12%425%5%36%6%8%10%40%
1440
11th to 20thNight
10%6%25%5%46%6%6%11%39%
1440
21st to endNight
8%6%36%6%46%5%5%11%41%
1440
July1st to 10thNight
9%5%248%5%5%6%7%10%40%
1440
11th to 20thNight
5%425%5%35%7%8%12%44%
1569
21st to endNight
6%5%25%6%46%7%9%11%38%
1771
August1st to 10thNight
7%5%27%7%5%6%6%8%11%37%
1611
11th to 20thNight
9%7%47%7%45%5%6%10%37%
1738
21st to endNight
9%5%25%6%46%6%8%11%39%
1980
September1st to 10thNight
12%425%6%35%5%6%8%44%
1800
11th to 20thNight
11%6%26%5%35%5%5%7%46%
1800
21st to endNight
20%8%25%5%2446%6%37%
2042
October1st to 10thNight
15%5%25%43445%7%46%
2160
11th to 20thNight
14%6%25%5%23446%49%
2160
21st to endNight
15%5%24433346%51%
2376
November1st to 10thNight
14%5%35%434435%50%
2297
11th to 20thNight
15%5%3443435%6%49%
2470
21st to endNight
13%425%43445%6%50%
2570
December1st to 10thNight
17%7%35%5%34436%42%
2660
11th to 20thNight
17%6%34423447%46%
3285
21st to endNight
14%7%35%5%3445%6%43%
4884

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
24%40%6%18%11%1
1613
11th to 20thDay
26%40%6%13%12%2
1671
21st to endDay
26%37%6%15%13%2
1782
February1st to 10thDay
28%36%7%16%10%2
1620
11th to 20thDay
26%36%5%16%14%3
1691
21st to endDay
30%37%7%12%11%3
1480
March1st to 10thDay
21%36%7%17%15%3
1930
11th to 20thDay
26%37%8%15%10%4
1980
21st to endDay
30%38%7%13%10%2
2226
April1st to 10thDay
22%36%8%14%14%6%
2160
11th to 20thDay
24%36%7%13%15%5%
2134
21st to endDay
27%37%7%13%12%4
2160
May1st to 10thDay
27%39%10%12%11%1
2197
11th to 20thDay
29%38%8%15%8%2
2379
21st to endDay
24%39%9%17%10%
2725
June1st to 10thDay
23%39%11%17%8%1
2520
11th to 20thDay
26%40%10%15%9%1
2520
21st to endDay
25%39%11%14%10%1
2520
July1st to 10thDay
24%41%10%14%9%2
2450
11th to 20thDay
22%43%12%16%6%1
2315
21st to endDay
24%42%14%12%7%
2405
August1st to 10thDay
26%40%10%16%7%
2314
11th to 20thDay
30%39%9%13%8%1
2143
21st to endDay
28%40%10%12%8%2
2376
September1st to 10thDay
25%38%8%10%15%4
2160
11th to 20thDay
26%37%6%16%13%2
2160
21st to endDay
30%38%6%11%13%3
1913
October1st to 10thDay
25%35%6%14%17%3
1800
11th to 20thDay
25%36%6%14%15%3
1800
21st to endDay
24%38%415%16%3
1980
November1st to 10thDay
18%40%5%18%16%2
1780
11th to 20thDay
21%39%8%15%14%3
1710
21st to endDay
22%39%7%15%14%3
1606
December1st to 10thDay
21%41%7%17%12%1
1520
11th to 20thDay
26%31%5%20%12%6%
1906
21st to endDay
30%25%8%24%12%1
2772
January1st to 10thNight
24%40%6%15%13%2
2550
11th to 20thNight
28%41%7%13%10%2
2417
21st to endNight
27%37%5%16%13%2
2574
February1st to 10thNight
28%36%6%15%12%3
2340
11th to 20thNight
28%36%5%14%13%4
2166
21st to endNight
28%36%6%13%14%4
1776
March1st to 10thNight
23%35%7%17%16%2
2028
11th to 20thNight
30%38%7%14%10%3
1980
21st to endNight
29%37%6%14%10%3
2129
April1st to 10thNight
26%37%8%11%15%4
1800
11th to 20thNight
22%35%8%14%15%5%
1775
21st to endNight
24%38%8%16%12%3
1800
May1st to 10thNight
27%39%10%13%9%2
1778
11th to 20thNight
30%40%7%12%10%1
1518
21st to endNight
25%39%9%18%8%1
1551
June1st to 10thNight
23%40%12%15%10%
1440
11th to 20thNight
25%41%10%15%8%1
1440
21st to endNight
26%39%9%15%9%2
1440
July1st to 10thNight
25%42%10%15%7%2
1400
11th to 20thNight
19%43%14%16%7%1
1518
21st to endNight
24%43%11%15%7%
1672
August1st to 10thNight
24%41%12%17%6%
1600
11th to 20thNight
29%39%10%12%10%
1738
21st to endNight
28%40%13%12%6%1
1980
September1st to 10thNight
23%38%9%12%14%4
1800
11th to 20thNight
23%38%7%15%15%1
1800
21st to endNight
30%37%7%9%14%3
2042
October1st to 10thNight
25%37%6%13%16%3
2160
11th to 20thNight
27%36%6%15%14%3
2160
21st to endNight
24%37%415%16%3
2376
November1st to 10thNight
19%40%7%15%16%3
2297
11th to 20thNight
24%40%6%13%13%4
2470
21st to endNight
23%40%5%16%13%3
2570
December1st to 10thNight
24%40%6%14%14%2
2660
11th to 20thNight
28%33%7%13%15%5%
3288
21st to endNight
29%27%11%20%13%1
4884

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
26%28%31%12%3
225
11th to 20thDay
27%30%32%11%1
257
21st to endDay
26%26%39%8%1
264
February1st to 10thDay
25%26%38%7%3
240
11th to 20thDay
32%26%31%11%1
350
21st to endDay
33%19%32%12%4
346
March1st to 10thDay
24%27%32%13%3
420
11th to 20thDay
27%24%32%12%41
420
21st to endDay
22%23%36%14%4
462
April1st to 10thDay
22%26%30%15%5%1
420
11th to 20thDay
17%18%35%20%6%4
412
21st to endDay
20%15%40%18%5%1
420
May1st to 10thDay
19%17%40%17%6%1
423
11th to 20thDay
21%13%37%19%9%2
447
21st to endDay
21%6%26%29%15%3
485
June1st to 10thDay
14%7%30%31%14%3
450
11th to 20thDay
15%8%25%32%15%4
450
21st to endDay
10%5%29%38%15%4
450
July1st to 10thDay
11%321%37%23%5%
445
11th to 20thDay
6%319%41%25%6%
444
21st to endDay
10%227%35%19%7%
488
August1st to 10thDay
11%5%24%34%20%7%
446
11th to 20thDay
13%5%19%33%23%6%
439
21st to endDay
11%324%29%23%11%
495
September1st to 10thDay
15%424%27%17%13%
450
11th to 20thDay
13%6%25%30%16%10%
450
21st to endDay
28%9%26%23%10%4
450
October1st to 10thDay
20%7%25%26%15%7%
450
11th to 20thDay
19%12%24%29%12%2
450
21st to endDay
17%15%34%21%10%3
495
November1st to 10thDay
19%11%32%22%11%4
418
11th to 20thDay
21%18%30%20%10%1
370
21st to endDay
23%17%29%19%12%1
266
December1st to 10thDay
26%23%32%14%5%
180
11th to 20thDay
25%22%28%20%4
180
21st to endDay
25%22%28%16%8%
198
January1st to 10thNight
21%20%35%21%3
760
11th to 20thNight
23%18%32%22%5%
744
21st to endNight
22%17%35%24%2
792
February1st to 10thNight
22%16%40%19%3
720
11th to 20thNight
28%20%35%15%2
703
21st to endNight
26%18%35%18%3
592
March1st to 10thNight
21%16%36%23%4
720
11th to 20thNight
24%17%34%20%5%1
720
21st to endNight
20%15%40%20%4
792
April1st to 10thNight
19%19%39%19%3
720
11th to 20thNight
17%12%40%24%7%1
711
21st to endNight
19%12%34%29%6%
720
May1st to 10thNight
18%14%37%24%7%1
698
11th to 20thNight
16%7%29%37%10%1
456
21st to endNight
16%320%42%17%2
389
June1st to 10thNight
12%225%43%16%3
360
11th to 20thNight
11%424%40%19%2
360
21st to endNight
8%423%43%20%3
360
July1st to 10thNight
10%321%41%24%1
350
11th to 20thNight
5%216%45%28%4
474
21st to endNight
7%222%39%27%3
591
August1st to 10thNight
9%315%43%27%4
537
11th to 20thNight
12%215%41%27%3
674
21st to endNight
10%416%34%29%6%
792
September1st to 10thNight
14%417%37%25%4
720
11th to 20thNight
14%317%36%25%4
720
21st to endNight
24%5%22%30%17%2
720
October1st to 10thNight
17%6%22%30%21%4
720
11th to 20thNight
19%10%27%28%14%2
720
21st to endNight
19%12%29%26%12%2
792
November1st to 10thNight
18%9%28%30%14%2
740
11th to 20thNight
19%13%31%28%8%1
760
21st to endNight
16%14%29%30%9%1
760
December1st to 10thNight
23%13%33%21%8%2
760
11th to 20thNight
19%12%38%25%5%
760
21st to endNight
21%15%29%29%6%
836
Page generated at 2024-01-13 19:28:27. Version ac07

Copyright 2024 Attilla Danko


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