Windsor Castle Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Windsor Castle Park clear sky chart from 2005-11-05 to 2019-06-02.

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
41%
17745
21%
53857
13%
17709
50%
17709
26%
33982

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
27%
836
24%
2769
10%
836
44%
836
23%
1685
January16th to endNight
25%
896
23%
2912
11%
896
41%
896
24%
1803
February1st to 15thNight
23%
821
20%
2650
9%
821
37%
821
22%
1648
February16th to endNight
23%
735
26%
2205
11%
735
41%
735
25%
1382
March1st to 15thNight
29%
840
22%
2349
10%
840
42%
840
26%
1521
March16th to endNight
28%
896
20%
2423
11%
896
37%
896
25%
1615
April1st to 15thNight
28%
838
22%
2096
6%
838
39%
838
30%
1401
April16th to endNight
36%
831
19%
2077
7%
831
40%
831
31%
1375
May1st to 15thNight
40%
772
16%
2032
6%
772
45%
772
27%
1386
May16th to endNight
58%
458
19%
1772
18%
458
62%
458
25%
1027
June1st to 15thNight
62%
392
17%
1569
18%
392
66%
392
23%
908
June16th to endNight
63%
390
16%
1560
18%
390
66%
390
23%
920
July1st to 15thNight
66%
412
17%
1522
18%
412
68%
412
25%
896
July16th to endNight
67%
612
17%
1739
13%
579
71%
579
30%
1116
August1st to 15thNight
64%
623
12%
1763
9%
620
65%
620
28%
1191
August16th to endNight
65%
828
17%
2070
10%
828
66%
828
31%
1389
September1st to 15thNight
60%
780
22%
1950
15%
780
63%
780
31%
1317
September16th to endNight
49%
777
19%
2122
15%
777
52%
777
24%
1473
October1st to 15thNight
50%
780
24%
2340
22%
780
57%
780
26%
1502
October16th to endNight
43%
832
31%
2496
21%
832
57%
832
34%
1434
November1st to 15thNight
39%
820
23%
2580
15%
820
51%
820
27%
1579
November16th to endNight
41%
840
25%
2785
18%
840
52%
840
28%
1623
December1st to 15thNight
32%
840
20%
2940
12%
840
44%
840
20%
1859
December16th to endNight
29%
896
22%
3136
13%
896
43%
896
22%
1932

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%2442445%7%42%
54463
Night
14%5%2442445%7%43%
54045
Cloud CoverDay
13%5%245%3445%8%42%
54473
Night
13%5%25%42445%7%43%
54049
TransparencyDay
40%5%11%22%16%3
54168
Night
39%5%11%22%17%3
53858
SeeingDay
17%8%25%24%17%6%
8007
Night
16%7%27%31%14%1
17753

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
16%6%345%24346%43%
1826
16th to endDay
15%6%24323446%47%
2016
February1st to 15thDay
14%7%2443435%6%42%
1869
16th to endDay
15%5%245%25%5%5%6%41%
1840
March1st to 15thDay
15%5%24423436%48%
2259
16th to endDay
17%6%23433336%44%
2503
April1st to 15thDay
12%5%23424446%49%
2512
16th to endDay
12%425%5%2445%7%44%
2488
May1st to 15thDay
14%6%25%425%45%7%40%
2590
16th to endDay
11%5%14425%5%5%8%44%
3045
June1st to 15thDay
10%413435%5%7%10%41%
2744
16th to endDay
7%4245%36%5%6%12%40%
2730
July1st to 15thDay
7%425%5%35%7%8%10%39%
2681
16th to endDay
6%425%5%47%6%7%12%35%
2673
August1st to 15thDay
11%5%26%6%35%6%7%8%35%
2424
16th to endDay
10%5%25%6%35%5%6%10%37%
2484
September1st to 15thDay
14%5%245%345%6%8%40%
2340
16th to endDay
19%7%36%6%3445%6%33%
2165
October1st to 15thDay
18%6%1442345%6%43%
1950
16th to endDay
11%325%42333454%
2080
November1st to 15thDay
18%6%24323435%45%
1938
16th to endDay
12%423323335%55%
1834
December1st to 15thDay
15%6%15%5%2235%6%43%
1680
16th to endDay
18%6%2442434442%
1792
January1st to 15thNight
14%5%24324347%45%
2769
16th to endNight
16%6%24422445%44%
2912
February1st to 15thNight
16%7%24423347%43%
2649
16th to endNight
15%7%24323336%46%
2205
March1st to 15thNight
15%424424446%46%
2337
16th to endNight
17%5%25%5%2335%5%42%
2423
April1st to 15thNight
11%6%2443446%6%44%
2096
16th to endNight
15%5%2442335%7%44%
2077
May1st to 15thNight
12%5%25%5%35%5%5%9%38%
2032
16th to endNight
12%42443345%9%46%
1771
June1st to 15thNight
10%414435%5%6%10%42%
1569
16th to endNight
6%425%7%35%5%6%10%41%
1560
July1st to 15thNight
7%315%5%26%5%6%10%43%
1605
16th to endNight
6%4245%37%6%8%11%38%
1847
August1st to 15thNight
7%426%6%46%6%7%9%37%
1774
16th to endNight
9%425%4446%7%11%39%
2070
September1st to 15thNight
13%5%145%245%6%8%42%
1950
16th to endNight
17%6%26%5%24447%37%
2122
October1st to 15thNight
16%5%24424445%45%
2340
16th to endNight
13%323323345%54%
2496
November1st to 15thNight
17%5%25%313345%47%
2580
16th to endNight
13%414424446%49%
2785
December1st to 15thNight
16%5%25%5%2445%5%40%
2940
16th to endNight
16%6%34423346%43%
3136

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
16%6%345%23346%43%
1826
16th to endDay
15%5%23323345%47%
2016
February1st to 15thDay
15%6%2442445%7%42%
1869
16th to endDay
15%6%24425%5%5%6%41%
1840
March1st to 15thDay
14%5%25%433335%48%
2270
16th to endDay
17%6%23324336%44%
2502
April1st to 15thDay
12%5%24423446%49%
2512
16th to endDay
12%5%2443445%7%44%
2488
May1st to 15thDay
14%6%25%5%2445%7%40%
2590
16th to endDay
11%5%244345%5%8%43%
3045
June1st to 15thDay
10%4135%45%5%7%10%41%
2744
16th to endDay
7%4245%36%5%7%12%39%
2730
July1st to 15thDay
7%315%5%35%7%8%11%38%
2681
16th to endDay
6%425%7%47%6%7%12%35%
2673
August1st to 15thDay
10%5%26%7%45%6%7%8%34%
2424
16th to endDay
10%5%25%6%46%5%7%10%35%
2484
September1st to 15thDay
13%5%25%5%345%6%9%39%
2340
16th to endDay
19%7%36%6%34446%33%
2165
October1st to 15thDay
19%424413346%43%
1950
16th to endDay
11%424433335%54%
2080
November1st to 15thDay
18%6%24314335%45%
1938
16th to endDay
12%324323335%54%
1834
December1st to 15thDay
15%5%25%43335%7%43%
1680
16th to endDay
18%7%15%42435%442%
1792
January1st to 15thNight
14%5%25%324346%45%
2769
16th to endNight
16%5%24423445%44%
2912
February1st to 15thNight
16%6%24423347%43%
2642
16th to endNight
15%6%24323336%47%
2205
March1st to 15thNight
15%5%14425%445%45%
2349
16th to endNight
16%5%25%5%24446%42%
2423
April1st to 15thNight
11%6%245%25%45%6%45%
2096
16th to endNight
14%5%34423347%44%
2077
May1st to 15thNight
13%5%25%5%35%5%6%9%38%
2031
16th to endNight
11%5%2342445%9%45%
1771
June1st to 15thNight
10%424425%5%7%10%41%
1569
16th to endNight
6%425%6%35%6%6%10%40%
1560
July1st to 15thNight
7%315%5%35%5%6%10%43%
1605
16th to endNight
7%425%5%35%8%8%11%37%
1847
August1st to 15thNight
7%426%6%46%6%6%10%37%
1774
16th to endNight
9%5%15%6%345%6%11%39%
2070
September1st to 15thNight
12%5%25%5%335%5%8%42%
1950
16th to endNight
17%5%26%5%24447%36%
2122
October1st to 15thNight
16%424424445%45%
2340
16th to endNight
13%313323445%54%
2496
November1st to 15thNight
17%6%25%313345%46%
2580
16th to endNight
13%424324346%49%
2785
December1st to 15thNight
16%5%26%42445%5%40%
2940
16th to endNight
16%7%24323446%43%
3136

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
42%38%21%18%5%
1827
16th to endDay
38%39%25%18%5%
2016
February1st to 15thDay
42%38%24%17%4
1872
16th to endDay
42%310%20%18%4
1840
March1st to 15thDay
39%310%20%20%4
2270
16th to endDay
43%39%20%19%3
2503
April1st to 15thDay
35%410%25%19%5%
2512
16th to endDay
38%5%11%20%16%7%
2488
May1st to 15thDay
42%6%12%23%12%1
2590
16th to endDay
37%7%13%25%14%1
3049
June1st to 15thDay
35%8%15%25%14%1
2744
16th to endDay
36%7%16%21%15%2
2730
July1st to 15thDay
35%10%15%23%11%3
2535
16th to endDay
39%8%15%20%13%1
2518
August1st to 15thDay
44%7%13%21%11%
2411
16th to endDay
40%8%14%20%13%2
2484
September1st to 15thDay
41%6%15%17%16%3
2340
16th to endDay
51%6%7%17%17%
2165
October1st to 15thDay
41%48%24%18%3
1950
16th to endDay
34%25%25%25%6%
2080
November1st to 15thDay
41%39%20%19%4
1938
16th to endDay
33%38%26%22%5%
1834
December1st to 15thDay
41%310%23%16%3
1680
16th to endDay
44%39%24%14%3
1792
January1st to 15thNight
40%49%20%19%6%
2769
16th to endNight
41%38%22%17%5%
2912
February1st to 15thNight
42%38%23%18%4
2650
16th to endNight
39%37%24%19%5%
2205
March1st to 15thNight
40%49%22%18%4
2349
16th to endNight
42%5%8%22%17%4
2423
April1st to 15thNight
38%5%11%20%19%4
2096
16th to endNight
39%310%21%17%6%
2077
May1st to 15thNight
41%7%13%23%12%2
2032
16th to endNight
35%7%15%26%13%1
1773
June1st to 15thNight
36%7%16%23%14%1
1569
16th to endNight
37%7%16%20%15%2
1560
July1st to 15thNight
35%8%14%27%11%2
1522
16th to endNight
34%10%16%25%12%1
1739
August1st to 15thNight
40%8%18%20%11%
1763
16th to endNight
38%7%16%22%12%1
2070
September1st to 15thNight
38%7%15%18%15%3
1950
16th to endNight
47%410%17%18%2
2122
October1st to 15thNight
41%47%23%19%3
2340
16th to endNight
32%37%23%26%6%
2496
November1st to 15thNight
40%210%19%20%5%
2580
16th to endNight
36%38%23%21%6%
2785
December1st to 15thNight
44%49%21%15%3
2940
16th to endNight
42%410%23%15%3
3136

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
26%17%39%12%4
164
16th to endDay
24%19%35%17%2
192
February1st to 15thDay
20%24%35%14%4
206
16th to endDay
21%16%37%20%3
343
March1st to 15thDay
20%18%35%20%5%
390
16th to endDay
22%11%35%21%6%2
416
April1st to 15thDay
21%11%38%15%9%3
390
16th to endDay
15%10%34%24%11%3
379
May1st to 15thDay
18%9%32%22%13%3
408
16th to endDay
18%223%26%24%5%
459
June1st to 15thDay
14%316%29%28%7%
379
16th to endDay
10%418%34%23%8%
375
July1st to 15thDay
10%114%33%30%9%
365
16th to endDay
10%110%33%30%14%
390
August1st to 15thDay
14%115%27%28%12%
358
16th to endDay
11%110%29%30%16%
396
September1st to 15thDay
17%316%23%18%20%
375
16th to endDay
25%214%26%18%12%
374
October1st to 15thDay
23%219%22%22%9%
375
16th to endDay
13%10%31%24%17%4
400
November1st to 15thDay
23%9%29%20%14%2
351
16th to endDay
15%14%27%25%13%2
274
December1st to 15thDay
23%12%40%15%7%
120
16th to endDay
25%19%33%18%3
128
January1st to 15thNight
18%12%36%26%6%
840
16th to endNight
19%11%36%29%2
896
February1st to 15thNight
20%12%39%23%3
824
16th to endNight
17%15%40%23%2
735
March1st to 15thNight
18%12%35%27%5%
840
16th to endNight
20%10%34%26%8%
896
April1st to 15thNight
15%12%40%25%6%
838
16th to endNight
18%7%33%30%9%
831
May1st to 15thNight
16%6%31%36%8%
772
16th to endNight
13%117%45%19%1
459
June1st to 15thNight
9%218%42%24%2
392
16th to endNight
7%217%47%25%1
390
July1st to 15thNight
10%13%44%27%3
412
16th to endNight
8%212%41%31%4
612
August1st to 15thNight
9%111%42%30%4
623
16th to endNight
12%19%37%32%6%
828
September1st to 15thNight
15%112%36%28%6%
780
16th to endNight
22%214%32%25%3
777
October1st to 15thNight
20%318%31%21%5%
780
16th to endNight
15%7%30%25%18%2
832
November1st to 15thNight
20%6%26%28%14%2
820
16th to endNight
16%9%29%29%14%
840
December1st to 15thNight
20%7%32%28%9%
840
16th to endNight
19%9%35%29%5%
896
Page generated at 2019-06-02 19:43:08. Version ac04

Copyright 2019 A. Danko


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