Rehoboth Beach
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rehoboth Beach clear sky chart from 2005-11-06 to 2024-01-12.

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
42%
23431
20%
74618
12%
23390
51%
23390
24%
46977

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
25%
759
23%
2649
9%
757
43%
757
21%
1589
January11th to 20thNight
28%
728
21%
2453
11%
728
42%
728
21%
1544
January21st to endNight
24%
792
25%
2574
10%
792
42%
792
23%
1559
February1st to 10thNight
24%
720
17%
2340
8%
720
37%
720
22%
1484
February11th to 20thNight
19%
702
20%
2098
7%
699
36%
699
21%
1368
February21st to endNight
25%
592
26%
1776
11%
592
44%
592
23%
1132
March1st to 10thNight
28%
720
22%
2156
10%
720
44%
720
27%
1311
March11th to 20thNight
30%
720
21%
1980
10%
720
41%
720
25%
1316
March21st to endNight
31%
792
20%
2050
9%
792
39%
792
24%
1428
April1st to 10thNight
30%
720
19%
1800
6%
720
38%
720
27%
1225
April11th to 20thNight
45%
711
21%
1775
9%
711
49%
711
33%
1156
April21st to endNight
40%
720
18%
1800
7%
720
45%
720
29%
1247
May1st to 10thNight
43%
644
17%
1724
8%
644
47%
644
26%
1200
May11th to 20thNight
44%
400
17%
1461
14%
400
49%
400
18%
977
May21st to endNight
58%
388
15%
1551
16%
388
61%
388
18%
1002
June1st to 10thNight
58%
360
17%
1440
19%
360
62%
360
21%
871
June11th to 20thNight
63%
360
15%
1440
17%
360
67%
360
21%
883
June21st to endNight
65%
360
14%
1440
18%
360
67%
360
22%
842
July1st to 10thNight
66%
350
15%
1400
19%
350
67%
350
20%
851
July11th to 20thNight
71%
348
18%
1392
24%
348
72%
348
25%
780
July21st to endNight
67%
490
18%
1577
18%
463
71%
463
27%
956
August1st to 10thNight
70%
559
15%
1622
12%
556
70%
556
28%
1050
August11th to 20thNight
68%
710
17%
1774
10%
710
69%
710
32%
1192
August21st to endNight
66%
792
16%
1980
10%
792
67%
792
33%
1336
September1st to 10thNight
60%
720
22%
1800
14%
720
62%
720
32%
1218
September11th to 20thNight
64%
720
26%
1836
19%
720
67%
720
37%
1157
September21st to endNight
46%
720
19%
1980
15%
720
51%
720
23%
1390
October1st to 10thNight
49%
720
18%
2137
17%
720
53%
720
26%
1375
October11th to 20thNight
46%
720
25%
2160
20%
720
55%
720
30%
1314
October21st to endNight
39%
792
24%
2412
16%
792
50%
792
27%
1493
November1st to 10thNight
41%
740
23%
2407
15%
740
54%
740
27%
1431
November11th to 20thNight
35%
760
24%
2470
15%
760
48%
760
23%
1530
November21st to endNight
37%
760
26%
2517
15%
760
53%
760
27%
1451
December1st to 10thNight
25%
760
19%
2660
8%
760
39%
760
19%
1692
December11th to 20thNight
27%
760
21%
3184
9%
759
43%
759
17%
1918
December21st to endNight
29%
822
15%
4803
11%
817
44%
817
14%
2709

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%
74730
Night
14%6%35%5%3445%7%43%
74991
TransparencyDay
38%7%14%24%15%3
74434
Night
40%6%12%23%16%3
74806
SeeingDay
16%7%22%30%20%5%
14000
Night
17%8%26%31%16%2
23448

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
14%7%35%4346%5%8%42%
1517
11th to 20thDay
17%6%35%435%447%42%
1544
21st to endDay
16%7%26%5%2445%7%42%
1782
February1st to 10thDay
15%8%36%5%35%5%6%8%37%
1620
11th to 20thDay
18%6%25%3235%47%44%
1746
21st to endDay
18%9%35%43445%6%38%
1480
March1st to 10thDay
15%425%434446%50%
1800
11th to 20thDay
17%5%35%42446%7%44%
1980
21st to endDay
15%8%37%5%35%5%5%6%40%
2304
April1st to 10thDay
13%6%36%42346%7%45%
2160
11th to 20thDay
11%5%25%43445%8%49%
2134
21st to endDay
15%5%35%43446%8%43%
2160
May1st to 10thDay
14%6%35%5%3446%9%41%
2232
11th to 20thDay
16%6%246%345%6%8%40%
2446
21st to endDay
12%5%25%5%445%5%9%43%
2725
June1st to 10thDay
12%5%245%35%6%7%10%42%
2520
11th to 20thDay
11%425%5%35%5%7%9%42%
2520
21st to endDay
8%4235%35%6%7%11%45%
2520
July1st to 10thDay
8%5%27%5%35%5%7%9%44%
2520
11th to 20thDay
5%334436%7%8%13%45%
2520
21st to endDay
9%4246%46%8%8%12%37%
2645
August1st to 10thDay
8%5%25%6%36%6%8%10%41%
2288
11th to 20thDay
9%5%26%6%46%6%7%9%40%
2126
21st to endDay
9%5%346%45%6%7%9%43%
2376
September1st to 10thDay
14%4244346%7%8%45%
2160
11th to 20thDay
11%6%36%42345%7%49%
2124
21st to endDay
17%7%36%4345%47%40%
1980
October1st to 10thDay
16%5%245%3445%7%45%
1819
11th to 20thDay
17%6%2432435%6%49%
1800
21st to endDay
14%6%245%3445%7%45%
1941
November1st to 10thDay
14%5%2442345%7%51%
1671
11th to 20thDay
13%6%35%5%34448%45%
1710
21st to endDay
14%424425%447%48%
1658
December1st to 10thDay
15%7%35%5%36%5%5%9%39%
1520
11th to 20thDay
15%8%36%423345%47%
1910
21st to endDay
15%7%35%4345%5%7%43%
2772
January1st to 10thNight
15%6%35%43446%9%42%
2649
11th to 20thNight
16%6%35%5%345%6%7%41%
2453
21st to endNight
15%6%245%3445%7%45%
2574
February1st to 10thNight
18%7%36%42445%7%40%
2340
11th to 20thNight
18%6%35%5%2445%7%41%
2098
21st to endNight
19%5%35%433347%44%
1776
March1st to 10thNight
14%5%35%433347%48%
2156
11th to 20thNight
18%7%25%6%24346%43%
1980
21st to endNight
18%7%46%5%3345%5%40%
2050
April1st to 10thNight
17%7%26%5%25%45%6%41%
1800
11th to 20thNight
11%6%35%5%34348%47%
1775
21st to endNight
18%5%35%6%35%5%5%7%40%
1800
May1st to 10thNight
16%7%36%5%35%46%7%39%
1724
11th to 20thNight
17%8%36%5%25%6%5%6%37%
1461
21st to endNight
13%9%35%5%35%5%48%39%
1550
June1st to 10thNight
14%6%24435%5%6%8%42%
1440
11th to 20thNight
11%425%5%46%7%6%10%40%
1440
21st to endNight
8%5%25%6%46%6%7%12%39%
1440
July1st to 10thNight
7%7%35%7%5%5%46%10%41%
1440
11th to 20thNight
6%5%25%6%35%6%7%9%46%
1440
21st to endNight
6%436%6%47%7%6%10%41%
1670
August1st to 10thNight
8%426%7%36%6%7%10%40%
1633
11th to 20thNight
9%425%6%46%6%7%10%42%
1774
21st to endNight
8%6%36%6%345%7%9%43%
1980
September1st to 10thNight
14%6%25%5%35%45%8%43%
1800
11th to 20thNight
10%5%244345%5%9%48%
1836
21st to endNight
19%7%26%5%35%5%47%37%
1980
October1st to 10thNight
18%5%25%5%24446%44%
2137
11th to 20thNight
17%424423446%50%
2160
21st to endNight
15%7%34325%45%6%46%
2412
November1st to 10thNight
13%5%25%424445%50%
2407
11th to 20thNight
15%6%35%434346%47%
2470
21st to endNight
12%425%43445%7%50%
2517
December1st to 10thNight
17%8%36%5%34447%40%
2660
11th to 20thNight
18%6%25%5%34446%43%
3285
21st to endNight
14%7%36%5%345%5%8%41%
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
40%5%12%26%14%3
1518
11th to 20thDay
42%5%15%22%15%2
1544
21st to endDay
41%5%10%26%15%3
1782
February1st to 10thDay
43%6%13%24%11%2
1620
11th to 20thDay
41%5%10%26%16%2
1755
21st to endDay
47%5%11%19%14%5%
1480
March1st to 10thDay
37%5%12%26%18%3
1800
11th to 20thDay
40%6%10%21%19%4
1980
21st to endDay
45%6%9%22%15%3
2304
April1st to 10thDay
37%6%13%21%17%6%
2160
11th to 20thDay
33%6%12%24%19%6%
2134
21st to endDay
38%7%14%19%18%4
2160
May1st to 10thDay
39%7%15%22%13%3
2232
11th to 20thDay
41%8%14%20%13%3
2450
21st to endDay
37%9%16%27%11%1
2725
June1st to 10thDay
36%10%16%22%14%2
2520
11th to 20thDay
35%10%17%22%14%3
2520
21st to endDay
30%10%16%24%18%1
2520
July1st to 10thDay
36%9%16%22%16%2
2450
11th to 20thDay
28%10%19%29%11%3
2445
21st to endDay
35%11%15%24%13%2
2497
August1st to 10thDay
35%10%16%26%12%1
2275
11th to 20thDay
38%11%15%23%12%2
2126
21st to endDay
35%8%15%23%15%4
2376
September1st to 10thDay
35%8%16%21%16%3
2160
11th to 20thDay
35%5%11%24%21%3
2124
21st to endDay
44%7%9%20%17%3
1980
October1st to 10thDay
40%5%13%22%16%4
1819
11th to 20thDay
37%5%9%28%20%3
1800
21st to endDay
38%5%9%26%20%3
1941
November1st to 10thDay
34%412%30%16%4
1671
11th to 20thDay
39%6%9%22%20%4
1710
21st to endDay
37%5%10%30%16%3
1658
December1st to 10thDay
42%5%17%22%12%3
1520
11th to 20thDay
41%410%30%12%3
1906
21st to endDay
39%6%19%22%14%
2772
January1st to 10thNight
39%5%11%24%18%3
2649
11th to 20thNight
42%5%12%25%14%1
2453
21st to endNight
39%49%27%17%3
2574
February1st to 10thNight
43%413%24%14%2
2340
11th to 20thNight
43%410%21%17%4
2100
21st to endNight
42%39%23%18%4
1776
March1st to 10thNight
37%411%27%19%3
2156
11th to 20thNight
42%5%10%21%18%4
1980
21st to endNight
46%5%8%18%18%5%
2050
April1st to 10thNight
43%5%10%19%18%5%
1800
11th to 20thNight
37%5%12%19%20%6%
1775
21st to endNight
43%5%10%20%18%4
1800
May1st to 10thNight
44%7%10%22%15%2
1724
11th to 20thNight
47%7%11%16%17%2
1462
21st to endNight
43%9%13%21%12%1
1551
June1st to 10thNight
39%8%12%21%18%1
1440
11th to 20thNight
37%10%13%22%15%2
1440
21st to endNight
36%9%15%23%15%2
1440
July1st to 10thNight
39%9%16%21%13%2
1400
11th to 20thNight
32%10%17%27%13%2
1392
21st to endNight
35%9%16%24%15%1
1577
August1st to 10thNight
36%10%17%23%14%
1622
11th to 20thNight
36%10%17%21%16%1
1774
21st to endNight
36%9%16%20%16%3
1980
September1st to 10thNight
39%6%13%23%15%4
1800
11th to 20thNight
32%7%12%24%21%3
1836
21st to endNight
46%7%8%19%17%2
1980
October1st to 10thNight
41%5%10%22%19%3
2137
11th to 20thNight
37%411%25%20%3
2160
21st to endNight
39%410%25%18%3
2412
November1st to 10thNight
36%5%10%26%18%5%
2407
11th to 20thNight
41%5%9%20%21%5%
2470
21st to endNight
34%5%12%27%20%3
2517
December1st to 10thNight
45%5%13%23%12%3
2660
11th to 20thNight
42%5%11%22%18%3
3288
21st to endNight
41%5%17%25%10%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
15%13%37%29%6%
180
11th to 20thDay
16%18%38%21%7%
204
21st to endDay
19%14%35%23%9%
264
February1st to 10thDay
22%10%37%23%8%
240
11th to 20thDay
25%13%39%20%4
414
21st to endDay
25%10%38%21%5%
346
March1st to 10thDay
16%12%38%27%7%
420
11th to 20thDay
20%10%34%28%6%2
420
21st to endDay
21%10%32%29%8%
462
April1st to 10thDay
16%14%32%29%7%2
420
11th to 20thDay
12%9%25%40%13%1
412
21st to endDay
19%8%26%33%13%1
420
May1st to 10thDay
19%8%28%29%13%2
423
11th to 20thDay
20%423%36%15%2
447
21st to endDay
17%316%30%25%9%
485
June1st to 10thDay
14%315%36%26%6%
450
11th to 20thDay
12%313%35%30%7%
450
21st to endDay
10%114%38%31%7%
450
July1st to 10thDay
11%29%28%38%12%
445
11th to 20thDay
226%32%44%13%
444
21st to endDay
10%29%35%35%9%
488
August1st to 10thDay
10%26%38%33%10%
446
11th to 20thDay
10%27%31%36%13%
439
21st to endDay
9%39%32%34%13%
495
September1st to 10thDay
15%214%28%24%17%
450
11th to 20thDay
13%313%31%31%10%
450
21st to endDay
22%5%16%32%20%4
450
October1st to 10thDay
21%317%28%22%9%
450
11th to 20thDay
17%6%22%28%23%3
450
21st to endDay
17%8%28%28%16%2
475
November1st to 10thDay
17%9%24%25%21%4
365
11th to 20thDay
13%14%35%24%13%1
370
21st to endDay
14%14%27%29%14%2
318
December1st to 10thDay
20%11%37%22%9%1
180
11th to 20thDay
21%12%33%25%9%
180
21st to endDay
19%12%27%32%11%
198
January1st to 10thNight
19%16%37%24%5%
760
11th to 20thNight
19%12%35%27%6%
728
21st to endNight
18%14%39%26%2
792
February1st to 10thNight
21%11%37%26%5%
720
11th to 20thNight
22%14%39%23%2
703
21st to endNight
21%13%36%25%4
592
March1st to 10thNight
16%13%38%25%7%
720
11th to 20thNight
22%9%34%26%7%2
720
21st to endNight
20%8%33%31%7%1
792
April1st to 10thNight
19%10%35%28%8%1
720
11th to 20thNight
14%6%30%38%12%1
711
21st to endNight
21%6%28%34%10%1
720
May1st to 10thNight
17%7%27%37%11%2
644
11th to 20thNight
20%6%23%36%14%1
400
21st to endNight
16%312%36%28%5%
389
June1st to 10thNight
16%415%39%24%3
360
11th to 20thNight
13%114%39%31%3
360
21st to endNight
10%112%44%30%3
360
July1st to 10thNight
8%111%40%36%3
350
11th to 20thNight
5%110%32%46%5%
348
21st to endNight
6%211%38%39%4
490
August1st to 10thNight
10%16%43%35%4
559
11th to 20thNight
10%210%35%37%7%
710
21st to endNight
10%39%35%33%10%
792
September1st to 10thNight
17%213%29%31%8%
720
11th to 20thNight
13%213%31%34%7%
720
21st to endNight
22%418%29%24%3
720
October1st to 10thNight
21%418%30%22%5%
720
11th to 20thNight
19%7%22%33%18%1
720
21st to endNight
17%9%30%28%14%2
792
November1st to 10thNight
15%8%28%29%15%4
740
11th to 20thNight
19%10%31%29%11%1
760
21st to endNight
13%14%31%28%12%1
760
December1st to 10thNight
22%12%34%21%9%2
760
11th to 20thNight
18%12%38%26%6%
760
21st to endNight
18%10%36%31%5%
836
Page generated at 2024-01-09 16:24:21. Version ac07

Copyright 2024 Attilla Danko


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