Ocean City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ocean City clear sky chart from 2005-11-06 to 2024-03-18.

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 Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(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

By Month

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 Forecast	Data Points
Cloud Cover	Day	13% 6% 2 5% 5% 3 4 5% 6% 8% 43%	78669
	Night	15% 7% 3 5% 5% 3 4 4 5% 7% 43%	81103
Transparency	Day	39% 5% 13% 25% 15% 3	78374
	Night	41% 4 11% 24% 17% 3	80917
Seeing	Day	16% 5% 19% 30% 24% 6%	14279
	Night	17% 7% 23% 31% 18% 3	23778

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	15% 6% 2 5% 3 2 3 4 4 8% 48%	2517
	11th to 20th	Day	13% 9% 3 6% 6% 3 3 4 4 6% 43%	2694
	21st to end	Day	13% 10% 4 8% 6% 3 5% 5% 4 5% 36%	3124
February	1st to 10th	Day	12% 8% 3 7% 6% 3 4 6% 6% 7% 39%	1723
	11th to 20th	Day	19% 6% 2 3 4 3 4 4 4 7% 43%	1848
	21st to end	Day	16% 10% 3 5% 5% 3 4 5% 4 7% 38%	1570
March	1st to 10th	Day	16% 6% 3 4 4 3 4 3 4 6% 48%	1900
	11th to 20th	Day	17% 4 2 4 4 3 3 5% 5% 8% 45%	2058
	21st to end	Day	16% 7% 4 5% 5% 3 5% 5% 5% 7% 39%	2306
April	1st to 10th	Day	15% 6% 2 5% 5% 3 4 4 5% 7% 45%	2160
	11th to 20th	Day	11% 5% 2 4 4 2 5% 4 4 7% 49%	2134
	21st to end	Day	15% 6% 2 5% 4 3 4 5% 5% 8% 43%	2160
May	1st to 10th	Day	13% 7% 3 6% 5% 3 4 4 6% 8% 41%	2222
	11th to 20th	Day	16% 7% 3 5% 5% 3 4 5% 5% 8% 39%	2424
	21st to end	Day	13% 6% 2 4 4 3 5% 4 6% 9% 44%	2725
June	1st to 10th	Day	11% 4 2 4 5% 3 5% 6% 7% 11% 41%	2520
	11th to 20th	Day	11% 5% 3 5% 5% 3 4 6% 6% 10% 43%	2520
	21st to end	Day	7% 3 2 5% 5% 3 5% 6% 7% 12% 45%	2520
July	1st to 10th	Day	9% 5% 2 5% 5% 4 5% 5% 6% 10% 45%	2520
	11th to 20th	Day	6% 3 2 4 4 3 5% 6% 8% 12% 46%	2520
	21st to end	Day	8% 3 2 6% 6% 4 7% 7% 8% 12% 38%	2628
August	1st to 10th	Day	8% 5% 2 4 5% 4 5% 6% 8% 11% 41%	2272
	11th to 20th	Day	10% 4 2 5% 6% 4 6% 6% 7% 9% 41%	2126
	21st to end	Day	9% 5% 2 5% 5% 3 5% 5% 7% 10% 43%	2376
September	1st to 10th	Day	13% 5% 2 4 5% 3 5% 5% 6% 8% 44%	2160
	11th to 20th	Day	10% 5% 2 5% 5% 3 4 4 5% 7% 48%	2120
	21st to end	Day	18% 7% 3 5% 6% 3 4 3 4 8% 38%	1980
October	1st to 10th	Day	16% 5% 2 5% 5% 2 3 4 6% 7% 45%	1828
	11th to 20th	Day	18% 5% 2 4 3 3 3 4 4 6% 49%	1800
	21st to end	Day	14% 6% 2 5% 5% 2 4 4 4 7% 47%	1949
November	1st to 10th	Day	14% 5% 2 5% 4 2 6% 4 5% 7% 46%	1671
	11th to 20th	Day	13% 6% 3 5% 6% 3 4 4 4 6% 46%	1710
	21st to end	Day	15% 5% 3 5% 4 2 4 4 4 6% 48%	1682
December	1st to 10th	Day	16% 6% 3 6% 5% 3 5% 5% 5% 8% 40%	1520
	11th to 20th	Day	15% 7% 3 5% 4 2 3 3 4 6% 46%	1910
	21st to end	Day	14% 6% 2 4 4 3 4 4 5% 9% 44%	2772
January	1st to 10th	Night	14% 6% 2 4 4 3 4 4 5% 7% 47%	4429
	11th to 20th	Night	17% 8% 3 5% 4 2 4 3 3 5% 45%	4248
	21st to end	Night	17% 10% 4 6% 5% 3 4 4 4 5% 40%	4532
February	1st to 10th	Night	17% 8% 3 5% 4 2 4 4 5% 6% 42%	2456
	11th to 20th	Night	18% 7% 3 5% 4 3 4 4 5% 6% 43%	2218
	21st to end	Night	18% 6% 3 5% 4 3 4 3 4 6% 45%	1884
March	1st to 10th	Night	16% 6% 2 5% 5% 2 4 4 4 6% 47%	2275
	11th to 20th	Night	18% 7% 2 5% 4 2 3 4 4 7% 43%	2068
	21st to end	Night	17% 7% 4 6% 5% 3 4 4 4 6% 41%	2048
April	1st to 10th	Night	17% 8% 3 5% 6% 3 3 5% 5% 6% 40%	1800
	11th to 20th	Night	12% 6% 2 5% 4 3 5% 4 4 6% 48%	1775
	21st to end	Night	16% 6% 3 5% 5% 3 6% 5% 6% 7% 39%	1800
May	1st to 10th	Night	16% 7% 3 7% 6% 2 4 4 6% 8% 38%	1737
	11th to 20th	Night	17% 7% 4 5% 5% 3 4 5% 5% 8% 38%	1483
	21st to end	Night	13% 9% 3 6% 5% 3 5% 4 5% 7% 40%	1550
June	1st to 10th	Night	15% 6% 3 6% 4 3 4 5% 5% 8% 40%	1440
	11th to 20th	Night	10% 5% 3 5% 5% 5% 6% 5% 7% 10% 39%	1440
	21st to end	Night	8% 6% 2 5% 6% 5% 6% 6% 7% 10% 39%	1440
July	1st to 10th	Night	8% 5% 3 5% 6% 4 5% 6% 8% 11% 39%	1440
	11th to 20th	Night	5% 6% 3 4 6% 3 6% 6% 8% 9% 46%	1440
	21st to end	Night	7% 5% 3 6% 6% 4 6% 6% 7% 12% 39%	1687
August	1st to 10th	Night	8% 5% 2 5% 7% 4 7% 6% 8% 11% 37%	1647
	11th to 20th	Night	9% 6% 3 6% 5% 4 5% 6% 7% 9% 42%	1774
	21st to end	Night	9% 5% 3 5% 6% 4 5% 6% 6% 8% 44%	1980
September	1st to 10th	Night	14% 6% 3 5% 4 3 4 4 5% 8% 43%	1800
	11th to 20th	Night	11% 4 2 6% 6% 2 4 5% 5% 8% 48%	1838
	21st to end	Night	20% 7% 2 5% 5% 3 4 5% 5% 7% 37%	1980
October	1st to 10th	Night	17% 7% 2 4 4 3 4 3 5% 7% 43%	2129
	11th to 20th	Night	18% 5% 2 4 4 2 4 3 4 6% 49%	2160
	21st to end	Night	15% 7% 2 4 4 2 4 4 4 7% 46%	2406
November	1st to 10th	Night	15% 5% 2 4 4 3 4 4 4 6% 49%	2407
	11th to 20th	Night	16% 6% 3 5% 4 3 4 3 4 6% 46%	2470
	21st to end	Night	12% 6% 2 4 3 2 4 4 5% 6% 50%	2493
December	1st to 10th	Night	17% 8% 3 5% 5% 3 4 4 6% 6% 39%	2660
	11th to 20th	Night	18% 5% 2 5% 5% 3 4 4 5% 6% 42%	3285
	21st to end	Night	13% 8% 3 5% 5% 3 4 5% 5% 8% 41%	4884

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	38% 3 7% 32% 18% 2	2518
	11th to 20th	Day	43% 2 10% 20% 19% 5%	2694
	21st to end	Day	51% 3 9% 23% 12% 2	3124
February	1st to 10th	Day	44% 3 13% 25% 12% 2	1723
	11th to 20th	Day	43% 2 9% 25% 16% 4	1857
	21st to end	Day	47% 3 12% 20% 14% 4	1570
March	1st to 10th	Day	40% 3 11% 24% 19% 2	1900
	11th to 20th	Day	38% 4 12% 21% 19% 4	2058
	21st to end	Day	44% 5% 10% 22% 15% 3	2306
April	1st to 10th	Day	40% 4 11% 22% 19% 5%	2160
	11th to 20th	Day	35% 3 12% 26% 19% 5%	2134
	21st to end	Day	39% 5% 14% 21% 18% 4	2160
May	1st to 10th	Day	41% 5% 14% 25% 12% 3	2222
	11th to 20th	Day	44% 4 14% 21% 13% 3	2428
	21st to end	Day	38% 5% 18% 27% 11% 1	2725
June	1st to 10th	Day	36% 6% 17% 25% 14% 1	2520
	11th to 20th	Day	36% 6% 17% 25% 13% 3	2520
	21st to end	Day	31% 7% 17% 28% 16% 1	2520
July	1st to 10th	Day	34% 7% 17% 25% 14% 2	2450
	11th to 20th	Day	28% 7% 21% 32% 10% 1	2445
	21st to end	Day	33% 9% 16% 27% 14% 1	2481
August	1st to 10th	Day	34% 8% 19% 28% 11%	2259
	11th to 20th	Day	38% 8% 16% 24% 13% 1	2126
	21st to end	Day	35% 6% 16% 26% 14% 3	2376
September	1st to 10th	Day	38% 6% 16% 22% 16% 3	2160
	11th to 20th	Day	35% 4 11% 27% 20% 2	2120
	21st to end	Day	46% 5% 9% 21% 17% 3	1980
October	1st to 10th	Day	37% 4 12% 27% 16% 4	1828
	11th to 20th	Day	39% 4 8% 28% 19% 3	1800
	21st to end	Day	38% 3 8% 27% 20% 3	1949
November	1st to 10th	Day	39% 4 9% 29% 16% 4	1671
	11th to 20th	Day	40% 4 10% 21% 20% 5%	1710
	21st to end	Day	39% 4 8% 31% 15% 4	1682
December	1st to 10th	Day	44% 4 13% 25% 12% 2	1520
	11th to 20th	Day	41% 3 9% 31% 14% 3	1906
	21st to end	Day	39% 3 18% 24% 15%	2772
January	1st to 10th	Night	39% 3 8% 29% 18% 4	4429
	11th to 20th	Night	44% 3 9% 26% 17% 2	4248
	21st to end	Night	49% 3 6% 25% 16% 2	4532
February	1st to 10th	Night	43% 4 12% 25% 15% 2	2456
	11th to 20th	Night	45% 3 7% 22% 19% 4	2220
	21st to end	Night	43% 3 8% 23% 19% 4	1884
March	1st to 10th	Night	40% 4 11% 25% 17% 3	2275
	11th to 20th	Night	42% 3 10% 23% 19% 3	2068
	21st to end	Night	46% 3 9% 20% 18% 5%	2048
April	1st to 10th	Night	45% 3 9% 20% 17% 5%	1800
	11th to 20th	Night	37% 4 11% 21% 21% 6%	1775
	21st to end	Night	42% 4 11% 21% 18% 4	1800
May	1st to 10th	Night	45% 4 12% 21% 15% 2	1737
	11th to 20th	Night	45% 4 14% 20% 15% 3	1484
	21st to end	Night	45% 5% 15% 21% 12% 1	1551
June	1st to 10th	Night	42% 6% 11% 23% 16% 1	1440
	11th to 20th	Night	38% 9% 13% 23% 15% 2	1440
	21st to end	Night	39% 7% 15% 23% 15% 2	1440
July	1st to 10th	Night	37% 7% 19% 23% 12% 2	1400
	11th to 20th	Night	31% 7% 19% 28% 14%	1392
	21st to end	Night	35% 8% 17% 25% 14% 1	1593
August	1st to 10th	Night	39% 9% 17% 23% 13%	1636
	11th to 20th	Night	37% 7% 18% 24% 14% 1	1774
	21st to end	Night	38% 7% 16% 22% 14% 3	1980
September	1st to 10th	Night	39% 6% 16% 21% 14% 4	1800
	11th to 20th	Night	35% 6% 10% 25% 21% 2	1838
	21st to end	Night	47% 6% 9% 19% 17% 2	1980
October	1st to 10th	Night	42% 3 9% 24% 19% 3	2129
	11th to 20th	Night	39% 3 9% 25% 21% 3	2160
	21st to end	Night	40% 4 8% 26% 18% 4	2406
November	1st to 10th	Night	38% 4 9% 26% 18% 5%	2407
	11th to 20th	Night	41% 3 10% 21% 19% 5%	2470
	21st to end	Night	36% 3 12% 26% 21% 3	2493
December	1st to 10th	Night	45% 4 12% 23% 13% 3	2660
	11th to 20th	Night	44% 3 10% 22% 19% 3	3288
	21st to end	Night	42% 3 16% 26% 11% 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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	22% 11% 31% 28% 8% 1	180
	11th to 20th	Day	14% 15% 38% 24% 9%	231
	21st to end	Day	18% 10% 28% 34% 9% 1	297
February	1st to 10th	Day	16% 10% 28% 35% 11%	283
	11th to 20th	Day	25% 9% 38% 23% 5%	456
	21st to end	Day	21% 9% 37% 24% 8% 1	382
March	1st to 10th	Day	19% 11% 29% 31% 10%	460
	11th to 20th	Day	20% 8% 26% 37% 8% 2	449
	21st to end	Day	20% 8% 26% 35% 10% 2	462
April	1st to 10th	Day	17% 9% 28% 32% 11% 2	420
	11th to 20th	Day	13% 4 23% 38% 20% 2	412
	21st to end	Day	19% 4 22% 36% 16% 2	420
May	1st to 10th	Day	18% 4 21% 35% 20% 2	423
	11th to 20th	Day	22% 2 15% 38% 19% 4	447
	21st to end	Day	18% 3 9% 29% 32% 10%	485
June	1st to 10th	Day	15% 2 11% 32% 32% 8%	450
	11th to 20th	Day	12% 2 10% 33% 35% 8%	450
	21st to end	Day	9% 1 9% 34% 39% 8%	450
July	1st to 10th	Day	11% 3 4 28% 39% 14%	445
	11th to 20th	Day	5% 1 3 24% 53% 13%	444
	21st to end	Day	9% 2 6% 30% 40% 12%	488
August	1st to 10th	Day	10% 1 6% 29% 42% 12%	446
	11th to 20th	Day	10% 2 5% 26% 45% 13%	439
	21st to end	Day	8% 2 8% 29% 35% 18%	495
September	1st to 10th	Day	15% 1 10% 26% 30% 19%	450
	11th to 20th	Day	12% 1 7% 34% 34% 12%	450
	21st to end	Day	22% 3 16% 30% 24% 5%	450
October	1st to 10th	Day	21% 2 14% 27% 26% 10%	450
	11th to 20th	Day	18% 6% 17% 32% 24% 4	450
	21st to end	Day	15% 9% 25% 29% 18% 5%	480
November	1st to 10th	Day	17% 6% 24% 26% 21% 5%	365
	11th to 20th	Day	18% 9% 30% 27% 15% 1	370
	21st to end	Day	19% 12% 23% 25% 17% 3	342
December	1st to 10th	Day	19% 7% 37% 26% 11% 1	180
	11th to 20th	Day	21% 7% 31% 28% 12% 1	180
	21st to end	Day	19% 7% 29% 28% 16% 1	198
January	1st to 10th	Night	17% 16% 35% 24% 8%	760
	11th to 20th	Night	19% 13% 33% 29% 6%	760
	21st to end	Night	19% 13% 36% 29% 3	836
February	1st to 10th	Night	21% 10% 34% 31% 4	760
	11th to 20th	Night	23% 12% 38% 24% 3	743
	21st to end	Night	21% 12% 30% 32% 5%	628
March	1st to 10th	Night	20% 10% 33% 28% 8%	760
	11th to 20th	Night	21% 7% 32% 30% 8% 3	752
	21st to end	Night	20% 7% 28% 36% 8% 1	792
April	1st to 10th	Night	22% 7% 31% 30% 9% 1	720
	11th to 20th	Night	14% 5% 25% 39% 15% 1	711
	21st to end	Night	20% 3 22% 39% 14% 2	720
May	1st to 10th	Night	19% 4 22% 39% 13% 2	657
	11th to 20th	Night	19% 3 19% 38% 18% 2	422
	21st to end	Night	18% 3 9% 33% 30% 7%	389
June	1st to 10th	Night	19% 3 10% 36% 30% 2	360
	11th to 20th	Night	11% 3 9% 40% 31% 6%	360
	21st to end	Night	8% 3 9% 42% 36% 3	360
July	1st to 10th	Night	8% 5% 7% 35% 37% 9%	350
	11th to 20th	Night	6% 2 4 27% 50% 11%	348
	21st to end	Night	8% 1 7% 34% 44% 6%	507
August	1st to 10th	Night	9% 2 4 36% 43% 6%	573
	11th to 20th	Night	11% 1 7% 29% 43% 9%	710
	21st to end	Night	11% 2 6% 32% 38% 12%	792
September	1st to 10th	Night	15% 2 8% 28% 37% 10%	720
	11th to 20th	Night	13% 3 10% 29% 38% 8%	720
	21st to end	Night	22% 4 15% 29% 25% 5%	720
October	1st to 10th	Night	20% 5% 16% 27% 23% 9%	720
	11th to 20th	Night	21% 6% 19% 32% 21% 2	720
	21st to end	Night	18% 7% 27% 28% 16% 4	792
November	1st to 10th	Night	18% 8% 23% 31% 16% 4	740
	11th to 20th	Night	19% 11% 27% 30% 12% 1	760
	21st to end	Night	15% 13% 27% 29% 15% 1	760
December	1st to 10th	Night	22% 10% 34% 22% 11% 2	760
	11th to 20th	Night	19% 10% 38% 26% 7%	760
	21st to end	Night	19% 10% 32% 31% 8%	836

Page generated at 2024-03-15 14:01:41. Version ac07

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