Wilmington
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wilmington clear sky chart from 2005-11-06 to 2024-03-08.

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
38%
23496
14%
80363
8%
23405
45%
23405
13%
59066

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
22%
750
19%
4339
7%
737
34%
737
7%
2816
January11th to 20thNight
25%
759
20%
4198
5%
740
35%
740
7%
2750
January21st to endNight
24%
830
10%
4477
6%
814
37%
814
8%
3184
February1st to 10thNight
26%
760
14%
2470
7%
760
35%
760
13%
1828
February11th to 20thNight
17%
743
13%
2270
3%
739
30%
739
12%
1740
February21st to endNight
21%
628
16%
1884
6%
628
33%
628
13%
1423
March1st to 10thNight
27%
751
16%
2225
7%
751
39%
751
17%
1606
March11th to 20thNight
25%
720
14%
1980
6%
720
32%
720
13%
1554
March21st to endNight
27%
792
16%
2066
7%
792
34%
792
15%
1620
April1st to 10thNight
23%
720
13%
1800
2%
720
30%
720
15%
1397
April11th to 20thNight
36%
711
16%
1775
6%
711
40%
711
17%
1376
April21st to endNight
33%
720
14%
1800
4%
720
37%
720
16%
1402
May1st to 10thNight
32%
612
12%
1692
5%
612
37%
612
13%
1333
May11th to 20thNight
38%
354
15%
1416
11%
354
44%
354
10%
1061
May21st to endNight
52%
388
11%
1551
12%
388
55%
388
11%
1143
June1st to 10thNight
52%
360
13%
1440
15%
360
55%
360
13%
1028
June11th to 20thNight
52%
360
11%
1440
12%
360
56%
360
12%
1056
June21st to endNight
61%
360
12%
1440
15%
360
64%
360
14%
1032
July1st to 10thNight
60%
350
9%
1400
12%
350
61%
350
11%
1056
July11th to 20thNight
68%
348
11%
1392
14%
348
69%
348
12%
999
July21st to endNight
61%
473
11%
1561
10%
447
64%
447
13%
1153
August1st to 10thNight
66%
537
12%
1600
9%
534
67%
534
16%
1205
August11th to 20thNight
59%
680
12%
1744
7%
680
60%
680
17%
1379
August21st to endNight
61%
792
9%
1980
4%
792
61%
792
15%
1577
September1st to 10thNight
54%
720
16%
1800
8%
720
57%
720
18%
1392
September11th to 20thNight
61%
720
22%
1816
15%
720
64%
720
23%
1328
September21st to endNight
48%
720
14%
1993
10%
720
52%
720
16%
1546
October1st to 10thNight
43%
720
12%
2160
9%
720
47%
720
16%
1614
October11th to 20thNight
45%
720
15%
2160
11%
720
52%
720
16%
1598
October21st to endNight
36%
792
16%
2413
10%
792
44%
792
15%
1806
November1st to 10thNight
40%
740
16%
2407
10%
740
49%
740
15%
1736
November11th to 20thNight
35%
760
16%
2470
11%
760
43%
760
13%
1862
November21st to endNight
34%
760
13%
2593
7%
760
42%
760
12%
1939
December1st to 10thNight
27%
760
13%
2660
5%
760
37%
760
11%
1994
December11th to 20thNight
28%
760
15%
3174
6%
759
38%
759
10%
2255
December21st to endNight
28%
826
9%
4777
5%
817
38%
817
7%
3278

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
15%6%25%5%35%5%6%7%41%
78531
Night
16%6%25%5%3445%7%43%
81018
TransparencyDay
27%35%9%16%11%2
78241
Night
29%34%8%16%11%2
80842
SeeingDay
17%9%26%26%16%6%
14052
Night
18%7%30%32%12%1
23524

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 10thDay
15%5%245%44445%47%
2517
11th to 20thDay
14%9%36%6%35%5%45%38%
2648
21st to endDay
21%7%35%5%35%446%37%
3124
February1st to 10thDay
16%7%35%445%5%6%7%39%
1710
11th to 20thDay
17%6%25%4246%5%6%42%
1795
21st to endDay
18%9%45%5%3335%6%38%
1570
March1st to 10thDay
14%6%24444446%47%
1889
11th to 20thDay
17%5%345%35%5%6%6%40%
1980
21st to endDay
20%6%25%5%35%45%5%40%
2290
April1st to 10thDay
14%6%36%5%335%5%7%43%
2160
11th to 20thDay
14%6%245%35%45%8%44%
2134
21st to endDay
17%425%435%5%6%7%40%
2160
May1st to 10thDay
18%7%35%445%45%7%37%
2282
11th to 20thDay
19%6%35%6%35%5%6%8%36%
2478
21st to endDay
14%5%25%5%35%5%6%8%41%
2725
June1st to 10thDay
12%5%36%436%6%6%9%40%
2520
11th to 20thDay
12%6%36%6%36%5%7%9%38%
2520
21st to endDay
10%5%25%5%35%6%7%10%42%
2520
July1st to 10thDay
10%5%25%6%47%6%6%9%40%
2520
11th to 20thDay
6%425%6%36%7%8%10%43%
2520
21st to endDay
9%5%36%7%47%6%8%10%35%
2662
August1st to 10thDay
9%5%36%7%46%5%7%8%39%
2327
11th to 20thDay
10%435%5%46%6%7%11%38%
2137
21st to endDay
12%6%246%36%6%7%9%40%
2376
September1st to 10thDay
15%6%245%345%6%7%43%
2160
11th to 20thDay
12%5%2442445%8%50%
2143
21st to endDay
17%7%35%5%345%5%6%39%
1962
October1st to 10thDay
17%6%25%5%3445%7%43%
1800
11th to 20thDay
17%4245%2445%7%48%
1800
21st to endDay
18%6%24424446%45%
1941
November1st to 10thDay
13%6%24323446%53%
1671
11th to 20thDay
16%42432446%6%48%
1710
21st to endDay
15%4345%25%446%48%
1582
December1st to 10thDay
18%6%25%5%3445%8%40%
1520
11th to 20thDay
19%6%24425%45%6%44%
1906
21st to endDay
17%6%25%5%45%6%5%8%37%
2772
January1st to 10thNight
18%6%25%434446%45%
4429
11th to 20thNight
19%7%35%423445%44%
4308
21st to endNight
24%7%25%5%34345%38%
4532
February1st to 10thNight
16%8%35%43445%7%41%
2470
11th to 20thNight
19%6%34433446%42%
2270
21st to endNight
18%7%25%5%3446%6%42%
1884
March1st to 10thNight
15%5%24435%45%7%48%
2216
11th to 20thNight
16%7%35%5%33445%44%
1979
21st to endNight
17%6%35%5%3345%6%43%
2066
April1st to 10thNight
17%7%35%5%25%447%42%
1800
11th to 20thNight
15%5%35%5%35%45%7%45%
1775
21st to endNight
20%5%25%434447%43%
1800
May1st to 10thNight
18%7%37%6%3445%8%36%
1692
11th to 20thNight
18%7%25%5%25%5%5%9%37%
1415
21st to endNight
15%7%36%435%46%9%39%
1550
June1st to 10thNight
15%5%345%3445%9%44%
1440
11th to 20thNight
11%6%37%6%35%5%6%10%39%
1440
21st to endNight
10%5%246%347%7%11%43%
1440
July1st to 10thNight
9%6%26%7%5%6%5%6%10%38%
1440
11th to 20thNight
7%4247%36%7%8%10%43%
1440
21st to endNight
9%6%35%5%35%6%7%9%43%
1653
August1st to 10thNight
8%5%26%5%35%7%6%10%42%
1611
11th to 20thNight
12%5%26%7%45%5%6%7%40%
1744
21st to endNight
13%5%245%35%5%5%7%45%
1980
September1st to 10thNight
15%6%25%5%33447%45%
1800
11th to 20thNight
13%6%2331335%7%53%
1816
21st to endNight
18%6%15%43445%8%41%
1993
October1st to 10thNight
20%6%35%5%33346%43%
2160
11th to 20thNight
17%42433435%6%50%
2160
21st to endNight
17%5%26%323446%48%
2413
November1st to 10thNight
12%5%25%42435%6%52%
2407
11th to 20thNight
17%7%24323346%48%
2470
21st to endNight
13%434435%5%6%7%46%
2593
December1st to 10thNight
19%6%35%434446%41%
2660
11th to 20thNight
18%5%35%43445%6%43%
3288
21st to endNight
17%7%35%435%5%6%7%38%
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
28%25%10%24%11%2
2518
11th to 20thDay
40%24%7%15%11%2
2648
21st to endDay
40%22%12%17%8%1
3124
February1st to 10thDay
28%34%7%20%10%1
1710
11th to 20thDay
29%34%6%18%10%2
1804
21st to endDay
31%33%7%15%10%3
1570
March1st to 10thDay
25%34%8%21%10%1
1892
11th to 20thDay
27%36%7%15%10%4
1980
21st to endDay
31%36%5%15%11%2
2290
April1st to 10thDay
26%36%9%13%12%5%
2160
11th to 20thDay
26%35%7%15%13%4
2134
21st to endDay
26%37%7%12%13%4
2160
May1st to 10thDay
27%37%8%13%12%2
2282
11th to 20thDay
29%37%8%13%10%3
2482
21st to endDay
24%38%9%17%10%2
2725
June1st to 10thDay
24%38%11%16%10%1
2520
11th to 20thDay
26%37%12%16%7%2
2520
21st to endDay
23%38%11%16%11%1
2520
July1st to 10thDay
25%37%9%16%10%2
2450
11th to 20thDay
20%38%9%19%12%2
2445
21st to endDay
24%40%9%14%11%1
2513
August1st to 10thDay
26%38%11%17%9%1
2314
11th to 20thDay
25%36%9%15%12%2
2137
21st to endDay
28%38%9%13%9%3
2376
September1st to 10thDay
26%37%7%13%14%3
2160
11th to 20thDay
20%36%7%16%18%3
2143
21st to endDay
29%36%5%12%15%2
1962
October1st to 10thDay
26%35%7%17%14%1
1800
11th to 20thDay
25%35%8%16%14%2
1800
21st to endDay
28%36%5%16%13%2
1941
November1st to 10thDay
19%39%7%20%14%1
1671
11th to 20thDay
24%39%8%16%12%2
1710
21st to endDay
26%38%7%18%9%1
1582
December1st to 10thDay
24%40%11%17%8%
1520
11th to 20thDay
30%32%7%21%8%2
1906
21st to endDay
34%25%14%17%10%
2772
January1st to 10thNight
33%25%8%23%10%2
4429
11th to 20thNight
34%24%7%20%12%2
4308
21st to endNight
41%22%6%22%8%
4532
February1st to 10thNight
29%33%7%18%11%1
2470
11th to 20thNight
31%35%6%15%11%3
2272
21st to endNight
30%33%7%15%11%4
1884
March1st to 10thNight
23%34%9%19%13%1
2226
11th to 20thNight
30%37%7%14%10%3
1980
21st to endNight
29%36%5%14%12%4
2066
April1st to 10thNight
28%36%8%12%13%4
1800
11th to 20thNight
27%35%7%13%14%4
1775
21st to endNight
28%36%6%14%12%5%
1800
May1st to 10thNight
31%36%7%11%12%2
1692
11th to 20thNight
29%38%8%10%13%2
1416
21st to endNight
26%39%10%14%10%2
1551
June1st to 10thNight
25%37%9%16%11%1
1440
11th to 20thNight
27%37%11%15%8%1
1440
21st to endNight
24%38%10%17%10%1
1440
July1st to 10thNight
28%39%11%13%8%1
1400
11th to 20thNight
22%40%11%15%9%2
1392
21st to endNight
23%41%10%14%11%1
1561
August1st to 10thNight
26%37%11%17%8%1
1600
11th to 20thNight
30%35%9%13%11%2
1744
21st to endNight
29%38%10%12%9%2
1980
September1st to 10thNight
26%36%6%13%15%3
1800
11th to 20thNight
20%36%6%17%18%3
1816
21st to endNight
28%36%5%13%14%3
1993
October1st to 10thNight
26%36%7%16%13%1
2160
11th to 20thNight
25%36%8%18%11%2
2160
21st to endNight
26%36%6%17%13%1
2413
November1st to 10thNight
20%41%6%17%15%3
2407
11th to 20thNight
25%39%6%15%11%3
2470
21st to endNight
25%39%8%16%11%1
2593
December1st to 10thNight
27%38%8%16%10%1
2660
11th to 20thNight
28%33%8%14%14%3
3288
21st to endNight
35%26%12%18%8%
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
18%19%33%22%7%1
180
11th to 20thDay
19%31%30%17%3
216
21st to endDay
21%15%36%21%6%2
297
February1st to 10thDay
22%19%34%19%7%
270
11th to 20thDay
22%18%40%18%2
403
21st to endDay
21%18%35%21%5%1
382
March1st to 10thDay
17%19%35%22%7%1
448
11th to 20thDay
20%17%32%23%5%2
420
21st to endDay
24%13%31%23%8%2
462
April1st to 10thDay
19%15%36%21%7%1
420
11th to 20thDay
16%14%32%24%12%3
412
21st to endDay
22%15%30%25%8%1
420
May1st to 10thDay
29%12%25%20%12%2
423
11th to 20thDay
22%8%25%29%14%2
447
21st to endDay
18%5%19%26%23%10%
485
June1st to 10thDay
13%6%21%33%20%7%
450
11th to 20thDay
16%425%30%19%6%
450
21st to endDay
11%5%21%34%19%9%
450
July1st to 10thDay
13%315%27%29%14%
445
11th to 20thDay
7%110%35%32%15%
444
21st to endDay
10%316%33%29%9%
488
August1st to 10thDay
9%415%32%28%12%
446
11th to 20thDay
12%313%30%30%13%
439
21st to endDay
11%220%29%23%15%
495
September1st to 10thDay
17%420%23%23%13%
450
11th to 20thDay
15%220%27%20%15%
450
21st to endDay
23%6%21%28%16%6%
450
October1st to 10thDay
24%5%17%27%16%10%
450
11th to 20thDay
14%10%26%26%22%3
450
21st to endDay
20%6%32%27%11%4
475
November1st to 10thDay
16%7%30%26%17%3
365
11th to 20thDay
16%13%33%26%12%
370
21st to endDay
14%10%36%29%10%1
242
December1st to 10thDay
22%15%33%21%8%1
180
11th to 20thDay
25%17%35%16%8%
180
21st to endDay
24%15%28%21%11%2
198
January1st to 10thNight
20%10%42%24%4
760
11th to 20thNight
22%11%36%26%5%
760
21st to endNight
19%11%42%27%2
836
February1st to 10thNight
20%10%40%28%2
760
11th to 20thNight
23%13%43%20%1
743
21st to endNight
21%13%42%21%3
628
March1st to 10thNight
17%13%38%26%5%
751
11th to 20thNight
19%11%40%23%7%1
720
21st to endNight
19%7%41%27%6%
792
April1st to 10thNight
20%13%39%22%6%
720
11th to 20thNight
15%10%33%35%7%
711
21st to endNight
21%8%32%32%7%
720
May1st to 10thNight
20%7%33%31%8%
612
11th to 20thNight
18%434%36%8%
354
21st to endNight
17%218%39%22%2
389
June1st to 10thNight
16%322%41%19%
360
11th to 20thNight
11%423%46%16%1
360
21st to endNight
10%118%52%19%
360
July1st to 10thNight
12%218%40%26%2
350
11th to 20thNight
5%311%49%29%2
348
21st to endNight
9%216%45%27%2
473
August1st to 10thNight
11%211%46%27%3
537
11th to 20thNight
14%311%39%30%3
680
21st to endNight
14%214%38%28%3
792
September1st to 10thNight
16%317%37%24%3
720
11th to 20thNight
15%312%38%28%5%
720
21st to endNight
20%321%33%22%1
720
October1st to 10thNight
22%5%22%28%18%4
720
11th to 20thNight
18%5%26%37%13%1
720
21st to endNight
20%7%32%31%10%1
792
November1st to 10thNight
14%6%33%34%13%1
740
11th to 20thNight
20%8%31%31%8%1
760
21st to endNight
14%9%38%29%9%
760
December1st to 10thNight
23%11%33%25%7%1
760
11th to 20thNight
18%8%38%30%6%
760
21st to endNight
20%9%37%32%2
836
Page generated at 2024-03-05 07:24:03. Version ac07

Copyright © 2024 Attilla Danko.


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