York
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the York clear sky chart from 2005-11-06 to 2024-03-01.

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%
24631
26%
79815
13%
24518
49%
24518
32%
44035

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
28%
943
28%
4020
10%
926
43%
926
22%
2348
January11th to 20thNight
29%
949
29%
3992
10%
930
43%
930
26%
1963
January21st to endNight
27%
1042
21%
4463
10%
1023
42%
1023
22%
2579
February1st to 10thNight
24%
886
23%
2406
7%
886
36%
886
27%
1520
February11th to 20thNight
25%
744
25%
2218
9%
740
38%
740
28%
1291
February21st to endNight
25%
628
30%
1884
9%
628
42%
628
31%
1035
March1st to 10thNight
28%
655
28%
2099
10%
655
44%
655
31%
1139
March11th to 20thNight
29%
540
24%
1980
14%
540
42%
540
27%
1071
March21st to endNight
23%
594
21%
2178
9%
594
40%
594
21%
1319
April1st to 10thNight
26%
540
24%
1943
11%
540
46%
540
30%
992
April11th to 20thNight
24%
533
23%
1701
10%
533
41%
533
23%
992
April21st to endNight
28%
540
25%
1620
13%
540
45%
540
27%
960
May1st to 10thNight
27%
540
20%
1620
12%
540
40%
540
25%
1026
May11th to 20thNight
39%
531
21%
1594
17%
531
48%
531
34%
908
May21st to endNight
37%
583
17%
1745
9%
582
47%
582
29%
1053
June1st to 10thNight
45%
540
21%
1620
13%
540
54%
540
43%
845
June11th to 20thNight
40%
540
22%
1620
9%
540
52%
540
41%
859
June21st to endNight
42%
540
24%
1620
12%
540
53%
540
47%
811
July1st to 10thNight
58%
525
20%
1575
14%
525
64%
525
42%
855
July11th to 20thNight
59%
522
26%
1566
19%
522
68%
522
54%
750
July21st to endNight
57%
591
23%
1673
19%
558
63%
558
38%
942
August1st to 10thNight
58%
537
24%
1601
19%
534
67%
534
42%
870
August11th to 20thNight
58%
534
28%
1600
26%
534
65%
534
40%
878
August21st to endNight
61%
594
29%
1919
26%
594
70%
594
44%
949
September1st to 10thNight
49%
540
26%
1951
22%
540
60%
540
37%
982
September11th to 20thNight
44%
540
29%
1980
20%
540
60%
540
34%
1031
September21st to endNight
45%
540
31%
1980
24%
540
57%
540
38%
959
October1st to 10thNight
42%
540
32%
1980
25%
540
54%
540
34%
997
October11th to 20thNight
34%
706
35%
2146
14%
706
51%
706
43%
1046
October21st to endNight
35%
828
32%
2412
14%
828
47%
828
39%
1292
November1st to 10thNight
39%
925
32%
2405
11%
925
53%
925
48%
1286
November11th to 20thNight
30%
950
35%
2470
10%
950
47%
950
44%
1349
November21st to endNight
36%
950
31%
2470
12%
950
48%
950
39%
1429
December1st to 10thNight
36%
950
30%
2470
13%
950
48%
950
39%
1422
December11th to 20thNight
25%
950
32%
2871
9%
948
41%
948
31%
1604
December21st to endNight
29%
1041
20%
4423
11%
1026
44%
1026
19%
2683

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
9%5%2442445%7%53%
78893
Night
9%5%2442445%7%55%
80581
TransparencyDay
31%6%12%26%20%5%
78618
Night
29%5%11%26%22%6%
80376
SeeingDay
12%14%33%28%11%2
14542
Night
11%13%36%30%9%1
24647

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
8%7%27%6%34446%49%
2847
11th to 20thDay
7%7%36%5%35%5%5%7%47%
2850
21st to endDay
11%11%36%422436%50%
3135
February1st to 10thDay
7%10%36%5%34347%47%
1790
11th to 20thDay
6%6%36%43435%6%55%
1849
21st to endDay
6%7%2433445%6%57%
1570
March1st to 10thDay
7%6%2442446%8%53%
1866
11th to 20thDay
14%8%3432335%6%51%
1980
21st to endDay
13%8%35%42345%7%47%
2178
April1st to 10thDay
9%5%25%42335%8%53%
2015
11th to 20thDay
12%6%345%25%36%7%47%
2208
21st to endDay
16%5%245%3345%7%46%
2340
May1st to 10thDay
14%5%3443445%8%46%
2340
11th to 20thDay
11%6%244345%5%6%51%
2302
21st to endDay
11%5%26%6%445%6%8%43%
2531
June1st to 10thDay
5%4245%2435%9%57%
2340
11th to 20thDay
6%313435%5%6%7%58%
2340
21st to endDay
5%2234245%7%9%57%
2340
July1st to 10thDay
7%426%435%6%6%7%51%
2340
11th to 20thDay
3213435%6%7%8%59%
2340
21st to endDay
7%425%5%45%5%5%9%50%
2546
August1st to 10thDay
5%424435%5%6%9%50%
2328
11th to 20thDay
7%42442446%8%55%
2301
21st to endDay
5%41442445%7%60%
2433
September1st to 10thDay
10%32343445%6%57%
2008
11th to 20thDay
9%415%42335%6%57%
1980
21st to endDay
7%4235%23446%59%
1980
October1st to 10thDay
12%323422346%58%
1976
11th to 20thDay
10%312412335%65%
1800
21st to endDay
11%6%24323235%60%
1941
November1st to 10thDay
6%423314335%65%
1673
11th to 20thDay
7%5%23322447%61%
1710
21st to endDay
10%413324335%62%
1710
December1st to 10thDay
8%6%2442345%7%56%
1710
11th to 20thDay
8%7%345%23437%55%
2161
21st to endDay
9%11%46%6%44447%41%
3135
January1st to 10thNight
7%8%48%5%34445%48%
4108
11th to 20thNight
5%435%5%34446%57%
4120
21st to endNight
14%9%35%32233452%
4532
February1st to 10thNight
10%7%46%424345%49%
2406
11th to 20thNight
8%7%36%42345%6%51%
2218
21st to endNight
8%5%35%324445%58%
1884
March1st to 10thNight
7%5%25%425%448%55%
2099
11th to 20thNight
12%6%2342345%7%52%
1980
21st to endNight
13%7%25%435%45%6%45%
2178
April1st to 10thNight
8%5%2432346%8%55%
1943
11th to 20thNight
12%6%245%3445%7%50%
1701
21st to endNight
14%5%25%42336%7%50%
1620
May1st to 10thNight
14%6%35%43445%7%46%
1620
11th to 20thNight
12%31442446%8%52%
1593
21st to endNight
10%324426%6%7%12%44%
1745
June1st to 10thNight
5%32332347%9%59%
1620
11th to 20thNight
5%312335%5%7%10%55%
1620
21st to endNight
422332347%10%59%
1620
July1st to 10thNight
6%2135%345%5%11%55%
1620
11th to 20thNight
321242346%10%62%
1620
21st to endNight
7%3245%35%6%6%10%51%
1772
August1st to 10thNight
43235%35%5%6%12%53%
1611
11th to 20thNight
8%42442446%9%55%
1600
21st to endNight
421442445%7%63%
1919
September1st to 10thNight
8%422433446%60%
1951
11th to 20thNight
7%5%1442446%7%56%
1980
21st to endNight
6%32432345%6%62%
1980
October1st to 10thNight
10%414323346%60%
1980
11th to 20thNight
9%21222223470%
2146
21st to endNight
9%423323235%63%
2412
November1st to 10thNight
7%323322246%67%
2405
11th to 20thNight
6%423323347%63%
2470
21st to endNight
11%5%23323345%60%
2470
December1st to 10thNight
7%5%24423346%58%
2470
11th to 20thNight
8%5%24423346%57%
3036
21st to endNight
11%9%46%5%23447%44%
4532

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
37%5%11%25%20%2
2848
11th to 20thDay
35%7%16%22%14%6%
2850
21st to endDay
37%411%27%19%3
3135
February1st to 10thDay
38%5%12%23%16%6%
1790
11th to 20thDay
31%5%14%26%18%6%
1859
21st to endDay
28%410%25%23%9%
1570
March1st to 10thDay
30%413%22%22%9%
1866
11th to 20thDay
36%410%20%25%6%
1980
21st to endDay
37%6%12%28%13%4
2178
April1st to 10thDay
29%5%12%26%21%7%
2015
11th to 20thDay
37%6%11%26%16%5%
2208
21st to endDay
38%5%12%27%17%2
2340
May1st to 10thDay
38%7%11%21%19%4
2340
11th to 20thDay
32%8%15%30%15%1
2306
21st to endDay
38%8%15%25%11%2
2531
June1st to 10thDay
24%7%18%31%15%5%
2340
11th to 20thDay
25%6%14%27%21%6%
2340
21st to endDay
22%8%12%26%24%8%
2340
July1st to 10thDay
30%8%13%27%19%3
2276
11th to 20thDay
18%8%14%29%23%7%
2271
21st to endDay
30%7%13%27%21%2
2405
August1st to 10thDay
28%7%16%28%16%4
2314
11th to 20thDay
27%6%13%29%19%6%
2301
21st to endDay
24%6%12%26%23%9%
2433
September1st to 10thDay
28%6%9%26%21%10%
2008
11th to 20thDay
28%410%26%28%4
1980
21st to endDay
26%5%10%26%26%8%
1980
October1st to 10thDay
28%5%10%24%26%7%
1976
11th to 20thDay
24%38%25%29%11%
1800
21st to endDay
29%39%25%24%10%
1941
November1st to 10thDay
23%49%27%29%9%
1673
11th to 20thDay
25%310%27%27%8%
1710
21st to endDay
27%38%27%28%7%
1710
December1st to 10thDay
29%411%30%22%4
1710
11th to 20thDay
31%48%30%23%4
2159
21st to endDay
42%6%9%24%17%2
3135
January1st to 10thNight
37%5%9%29%16%3
4108
11th to 20thNight
27%5%15%25%23%4
4120
21st to endNight
38%410%24%22%2
4532
February1st to 10thNight
37%5%12%23%17%6%
2406
11th to 20thNight
33%5%11%25%20%6%
2218
21st to endNight
28%49%23%24%13%
1884
March1st to 10thNight
29%5%9%24%24%10%
2099
11th to 20thNight
32%5%11%24%22%7%
1980
21st to endNight
39%6%11%25%15%3
2178
April1st to 10thNight
28%412%24%25%8%
1943
11th to 20thNight
35%5%13%24%19%4
1701
21st to endNight
35%5%12%24%21%4
1620
May1st to 10thNight
38%7%12%21%19%4
1620
11th to 20thNight
29%7%18%29%16%2
1594
21st to endNight
31%10%20%26%10%2
1746
June1st to 10thNight
21%7%19%31%18%4
1620
11th to 20thNight
23%6%14%30%21%5%
1620
21st to endNight
20%5%14%30%22%9%
1620
July1st to 10thNight
26%5%14%29%22%4
1575
11th to 20thNight
17%414%29%28%7%
1566
21st to endNight
27%7%13%28%22%2
1673
August1st to 10thNight
24%7%17%32%16%4
1601
11th to 20thNight
27%6%12%30%21%5%
1600
21st to endNight
21%6%13%28%24%9%
1919
September1st to 10thNight
26%5%10%24%24%11%
1951
11th to 20thNight
27%6%9%23%28%6%
1980
21st to endNight
23%5%10%23%29%9%
1980
October1st to 10thNight
27%411%21%29%8%
1980
11th to 20thNight
20%38%24%33%12%
2146
21st to endNight
26%38%23%28%12%
2412
November1st to 10thNight
21%39%26%28%12%
2405
11th to 20thNight
23%37%29%30%8%
2470
21st to endNight
27%38%25%26%10%
2470
December1st to 10thNight
27%413%27%23%6%
2470
11th to 20thNight
29%38%34%21%5%
3037
21st to endNight
38%7%11%26%14%4
4532

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
11%27%38%16%7%1
270
11th to 20thDay
19%25%39%15%2
270
21st to endDay
12%26%44%15%3
297
February1st to 10thDay
16%31%39%11%2
270
11th to 20thDay
16%25%40%15%4
270
21st to endDay
15%33%39%10%2
225
March1st to 10thDay
12%25%48%11%3
240
11th to 20thDay
25%21%36%13%41
240
21st to endDay
25%27%38%9%1
264
April1st to 10thDay
15%23%46%14%2
275
11th to 20thDay
15%24%43%16%2
486
21st to endDay
22%22%32%19%5%1
600
May1st to 10thDay
15%16%41%21%6%
603
11th to 20thDay
16%15%31%27%10%1
625
21st to endDay
15%12%34%27%10%2
679
June1st to 10thDay
7%7%31%34%16%5%
630
11th to 20thDay
7%8%39%33%13%1
630
21st to endDay
6%5%41%35%11%2
630
July1st to 10thDay
9%218%45%22%4
621
11th to 20thDay
4322%45%22%4
618
21st to endDay
8%119%45%22%5%
684
August1st to 10thDay
6%323%43%22%2
626
11th to 20thDay
10%223%44%20%2
615
21st to endDay
6%326%42%21%2
552
September1st to 10thDay
12%322%44%17%2
298
11th to 20thDay
5%439%37%13%2
270
21st to endDay
14%10%37%23%13%2
270
October1st to 10thDay
15%17%31%22%13%2
270
11th to 20thDay
11%23%39%23%31
270
21st to endDay
23%16%37%15%7%2
297
November1st to 10thDay
15%20%37%20%6%1
270
11th to 20thDay
17%17%43%16%7%1
270
21st to endDay
19%21%33%18%7%2
270
December1st to 10thDay
11%26%32%23%8%
270
11th to 20thDay
14%24%38%20%4
270
21st to endDay
20%30%35%13%2
297
January1st to 10thNight
9%15%40%29%6%
950
11th to 20thNight
10%18%37%28%6%1
950
21st to endNight
10%17%42%25%6%
1045
February1st to 10thNight
15%18%38%24%4
886
11th to 20thNight
14%19%39%26%3
744
21st to endNight
13%20%39%24%4
628
March1st to 10thNight
10%21%38%27%4
655
11th to 20thNight
15%15%38%23%9%
540
21st to endNight
18%15%41%22%4
594
April1st to 10thNight
13%16%42%22%6%
540
11th to 20thNight
14%25%32%25%4
533
21st to endNight
19%16%35%24%6%
540
May1st to 10thNight
17%15%36%24%8%
540
11th to 20thNight
15%9%33%31%11%1
531
21st to endNight
12%10%36%28%12%1
584
June1st to 10thNight
8%6%36%34%15%1
540
11th to 20thNight
6%8%42%34%10%
540
21st to endNight
6%6%41%36%10%1
540
July1st to 10thNight
6%125%47%19%1
525
11th to 20thNight
5%130%45%17%2
522
21st to endNight
7%226%41%23%1
591
August1st to 10thNight
4227%46%20%1
537
11th to 20thNight
10%322%46%18%
534
21st to endNight
5%326%42%23%1
594
September1st to 10thNight
10%331%38%16%1
540
11th to 20thNight
10%437%34%13%2
540
21st to endNight
8%8%35%35%13%1
540
October1st to 10thNight
14%9%33%30%14%1
540
11th to 20thNight
11%14%38%29%8%
706
21st to endNight
13%14%37%26%10%1
828
November1st to 10thNight
10%11%37%31%11%1
925
11th to 20thNight
8%15%43%26%7%
950
21st to endNight
13%15%33%32%7%
950
December1st to 10thNight
10%14%35%33%7%
950
11th to 20thNight
15%16%40%26%3
950
21st to endNight
13%21%33%27%6%
1045
Page generated at 2024-02-27 05:30:13. Version ac07

Copyright © 2024 Attilla Danko.


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