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 2026-10-29.

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 6% 4 4 4 4 6% 8% 42%	149171
	Night	14% 7% 3 6% 4 4 4 3 5% 7% 43%	142854
Transparency	Day	39% 5% 13% 25% 15% 3	152745
	Night	40% 4 12% 24% 17% 3	147351
Seeing	Day	16% 5% 19% 31% 24% 6%	17798
	Night	17% 7% 23% 31% 19% 3	27098

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	12% 5% 2 5% 3 4 4 4 5% 7% 50%	4661
	11th to 20th	Day	13% 7% 2 6% 4 4 3 3 4 4 51%	5022
	21st to end	Day	12% 7% 3 8% 4 4 4 3 5% 6% 43%	5780
February	1st to 10th	Day	12% 7% 3 7% 5% 4 5% 4 6% 7% 39%	1905
	11th to 20th	Day	19% 8% 3 4 4 4 4 3 4 6% 41%	2048
	21st to end	Day	16% 10% 3 6% 4 3 4 4 5% 7% 39%	1730
March	1st to 10th	Day	17% 6% 2 6% 4 4 4 3 5% 7% 43%	4579
	11th to 20th	Day	9% 8% 3 6% 3 3 3 3 5% 6% 50%	5090
	21st to end	Day	14% 8% 2 6% 4 3 4 3 6% 6% 44%	5930
April	1st to 10th	Day	15% 6% 2 5% 5% 3 4 3 5% 8% 44%	2520
	11th to 20th	Day	11% 7% 2 5% 4 4 5% 3 5% 8% 48%	2494
	21st to end	Day	14% 7% 2 5% 4 4 4 4 5% 8% 43%	2520
May	1st to 10th	Day	17% 8% 3 7% 5% 5% 4 3 5% 7% 36%	7235
	11th to 20th	Day	16% 8% 3 7% 4 4 4 3 5% 7% 39%	8042
	21st to end	Day	20% 7% 3 7% 4 5% 4 3 5% 8% 34%	9045
June	1st to 10th	Day	11% 5% 2 5% 4 5% 4 5% 8% 10% 41%	2940
	11th to 20th	Day	10% 6% 2 5% 4 4 4 4 6% 10% 44%	2940
	21st to end	Day	7% 4 1 6% 5% 4 5% 4 7% 11% 45%	2940
July	1st to 10th	Day	7% 5% 2 6% 4 4 5% 4 6% 11% 46%	8280
	11th to 20th	Day	9% 7% 3 7% 5% 6% 6% 5% 9% 12% 32%	8280
	21st to end	Day	8% 4 2 7% 5% 5% 6% 5% 8% 11% 38%	8586
August	1st to 10th	Day	10% 7% 2 6% 4 5% 5% 5% 8% 12% 35%	5859
	11th to 20th	Day	8% 5% 2 7% 5% 5% 6% 5% 7% 9% 40%	5488
	21st to end	Day	10% 5% 2 5% 4 4 5% 4 7% 10% 44%	6080
September	1st to 10th	Day	13% 5% 2 5% 4 4 4 4 6% 8% 46%	2520
	11th to 20th	Day	10% 6% 2 6% 4 4 5% 4 6% 8% 47%	2473
	21st to end	Day	21% 8% 3 6% 5% 4 4 2 5% 7% 35%	2310
October	1st to 10th	Day	15% 5% 2 5% 4 3 3 4 6% 7% 46%	2132
	11th to 20th	Day	18% 5% 2 4 3 3 3 3 4 5% 49%	2100
	21st to end	Day	13% 5% 2 5% 4 3 4 2 4 7% 49%	2245
November	1st to 10th	Day	13% 6% 2 5% 4 3 5% 3 5% 6% 47%	1851
	11th to 20th	Day	12% 6% 3 5% 5% 4 4 3 4 7% 47%	1890
	21st to end	Day	14% 6% 2 5% 4 3 3 3 4 6% 49%	1858
December	1st to 10th	Day	10% 6% 2 5% 4 3 4 3 5% 6% 51%	2680
	11th to 20th	Day	17% 9% 3 6% 3 3 2 2 4 6% 45%	3070
	21st to end	Day	11% 6% 2 5% 4 4 4 4 5% 9% 46%	4048
January	1st to 10th	Night	11% 7% 2 4 3 4 4 3 5% 8% 49%	8233
	11th to 20th	Night	14% 7% 2 5% 3 3 3 2 3 4 54%	7920
	21st to end	Night	14% 8% 3 5% 4 3 4 3 4 5% 47%	8401
February	1st to 10th	Night	17% 8% 3 6% 3 4 3 4 6% 6% 41%	2714
	11th to 20th	Night	19% 7% 2 5% 4 4 4 3 5% 5% 42%	2458
	21st to end	Night	17% 7% 3 5% 3 4 4 2 5% 6% 45%	2076
March	1st to 10th	Night	18% 7% 2 6% 4 3 3 3 4 5% 45%	5476
	11th to 20th	Night	13% 10% 3 5% 3 2 3 3 5% 7% 46%	5090
	21st to end	Night	15% 9% 3 6% 4 4 4 3 5% 5% 43%	5242
April	1st to 10th	Night	17% 8% 3 6% 4 3 4 4 5% 6% 40%	2100
	11th to 20th	Night	12% 7% 2 6% 4 4 4 3 4 6% 49%	2075
	21st to end	Night	14% 7% 2 5% 4 4 5% 4 6% 7% 41%	2100
May	1st to 10th	Night	13% 8% 3 8% 5% 4 4 4 6% 8% 37%	5604
	11th to 20th	Night	16% 9% 3 6% 4 4 3 3 5% 7% 40%	4859
	21st to end	Night	22% 10% 4 8% 4 4 3 3 4 6% 32%	5108
June	1st to 10th	Night	13% 7% 3 8% 4 3 5% 4 6% 8% 40%	1680
	11th to 20th	Night	10% 5% 2 5% 5% 6% 6% 4 7% 10% 39%	1680
	21st to end	Night	8% 6% 2 6% 5% 7% 5% 5% 7% 10% 41%	1680
July	1st to 10th	Night	9% 6% 3 7% 5% 6% 6% 5% 8% 11% 35%	4678
	11th to 20th	Night	9% 8% 3 8% 6% 6% 6% 5% 8% 10% 31%	4677
	21st to end	Night	12% 6% 3 7% 5% 5% 5% 4 7% 11% 35%	5473
August	1st to 10th	Night	13% 8% 3 8% 5% 6% 5% 4 6% 9% 32%	4229
	11th to 20th	Night	10% 6% 3 7% 5% 5% 5% 4 7% 9% 41%	4557
	21st to end	Night	8% 6% 2 7% 4 5% 5% 4 5% 7% 48%	5045
September	1st to 10th	Night	13% 7% 3 5% 3 4 3 3 5% 8% 44%	2100
	11th to 20th	Night	11% 5% 2 6% 4 3 4 4 5% 8% 46%	2145
	21st to end	Night	22% 8% 3 6% 4 4 4 4 5% 7% 34%	2310
October	1st to 10th	Night	17% 6% 2 5% 3 4 3 3 6% 7% 45%	2485
	11th to 20th	Night	18% 6% 2 5% 3 3 4 2 4 6% 49%	2520
	21st to end	Night	13% 7% 2 5% 3 3 4 3 4 7% 49%	2771
November	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 4 6% 49%	2667
	11th to 20th	Night	15% 7% 2 6% 4 4 4 3 5% 6% 46%	2730
	21st to end	Night	12% 6% 2 5% 4 3 4 3 5% 6% 51%	2756
December	1st to 10th	Night	11% 6% 2 5% 3 4 3 3 6% 7% 51%	4720
	11th to 20th	Night	19% 8% 3 7% 4 4 4 3 5% 6% 38%	5345
	21st to end	Night	12% 9% 3 6% 4 3 4 4 5% 7% 42%	7150

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	35% 3 7% 28% 23% 3	4662
	11th to 20th	Day	38% 2 7% 21% 25% 7%	5022
	21st to end	Day	43% 3 8% 31% 13% 1	5780
February	1st to 10th	Day	43% 3 13% 25% 13% 3	1905
	11th to 20th	Day	45% 2 9% 23% 16% 4	2057
	21st to end	Day	46% 3 11% 22% 14% 4	1730
March	1st to 10th	Day	42% 3 8% 20% 19% 7%	4579
	11th to 20th	Day	36% 3 10% 27% 19% 6%	5090
	21st to end	Day	41% 4 11% 18% 19% 7%	5930
April	1st to 10th	Day	40% 4 12% 21% 19% 5%	2520
	11th to 20th	Day	35% 3 12% 27% 18% 5%	2494
	21st to end	Day	39% 4 13% 22% 18% 4	2520
May	1st to 10th	Day	48% 5% 13% 22% 11% 2	7267
	11th to 20th	Day	44% 4 12% 25% 14% 1	8046
	21st to end	Day	49% 5% 11% 21% 13% 2	9061
June	1st to 10th	Day	36% 6% 16% 24% 15% 2	2940
	11th to 20th	Day	35% 6% 16% 27% 13% 2	2940
	21st to end	Day	31% 7% 16% 28% 16% 1	2940
July	1st to 10th	Day	32% 8% 23% 23% 12% 1	8210
	11th to 20th	Day	42% 9% 19% 23% 7% 1	8205
	21st to end	Day	37% 8% 15% 24% 16% 1	8397
August	1st to 10th	Day	40% 10% 24% 22% 5%	5846
	11th to 20th	Day	37% 7% 19% 28% 8%	5524
	21st to end	Day	34% 6% 15% 30% 15% 1	6080
September	1st to 10th	Day	36% 6% 16% 24% 16% 3	2520
	11th to 20th	Day	36% 5% 11% 26% 19% 2	2473
	21st to end	Day	49% 5% 9% 19% 14% 3	2310
October	1st to 10th	Day	32% 3 10% 28% 22% 5%	3405
	11th to 20th	Day	30% 3 6% 26% 29% 6%	3340
	21st to end	Day	26% 3 11% 29% 23% 9%	3559
November	1st to 10th	Day	38% 4 9% 30% 16% 4	1851
	11th to 20th	Day	39% 4 10% 22% 20% 4	1890
	21st to end	Day	38% 4 8% 30% 16% 3	1858
December	1st to 10th	Day	35% 3 14% 27% 17% 4	2680
	11th to 20th	Day	44% 2 12% 25% 14% 3	3066
	21st to end	Day	37% 3 17% 26% 17%	4048
January	1st to 10th	Night	36% 2 11% 25% 21% 5%	8234
	11th to 20th	Night	37% 2 6% 26% 23% 7%	7920
	21st to end	Night	41% 2 8% 29% 17% 3	8401
February	1st to 10th	Night	43% 4 11% 24% 15% 2	2714
	11th to 20th	Night	45% 3 8% 22% 18% 4	2460
	21st to end	Night	43% 3 8% 24% 19% 5%	2076
March	1st to 10th	Night	42% 3 8% 22% 16% 8%	5476
	11th to 20th	Night	39% 3 9% 24% 20% 6%	5090
	21st to end	Night	44% 3 9% 19% 19% 6%	5242
April	1st to 10th	Night	45% 3 9% 20% 17% 5%	2100
	11th to 20th	Night	37% 3 12% 22% 21% 6%	2075
	21st to end	Night	41% 4 11% 22% 19% 4	2100
May	1st to 10th	Night	44% 4 14% 25% 11% 1	5634
	11th to 20th	Night	44% 4 13% 25% 13% 1	4860
	21st to end	Night	55% 4 9% 17% 14% 1	5115
June	1st to 10th	Night	42% 5% 11% 22% 18% 2	1680
	11th to 20th	Night	39% 8% 13% 24% 15% 2	1680
	21st to end	Night	37% 7% 15% 24% 16% 2	1680
July	1st to 10th	Night	41% 8% 16% 20% 14% 1	4640
	11th to 20th	Night	46% 7% 17% 21% 8%	4632
	21st to end	Night	41% 6% 16% 22% 14%	5348
August	1st to 10th	Night	48% 8% 18% 20% 6%	4218
	11th to 20th	Night	39% 6% 18% 27% 10%	4587
	21st to end	Night	36% 5% 12% 26% 20% 1	5045
September	1st to 10th	Night	38% 5% 15% 22% 15% 4	2100
	11th to 20th	Night	36% 6% 10% 27% 20% 2	2145
	21st to end	Night	51% 6% 9% 18% 15% 2	2310
October	1st to 10th	Night	35% 3 9% 24% 26% 3	3992
	11th to 20th	Night	28% 3 9% 25% 30% 6%	4019
	21st to end	Night	25% 2 10% 30% 24% 9%	4407
November	1st to 10th	Night	37% 4 9% 25% 20% 5%	2667
	11th to 20th	Night	41% 3 10% 22% 20% 5%	2730
	21st to end	Night	35% 2 12% 27% 21% 3	2756
December	1st to 10th	Night	34% 3 14% 25% 21% 3	4720
	11th to 20th	Night	48% 3 11% 20% 14% 4	5348
	21st to end	Night	42% 3 16% 23% 15% 1	7150

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	20% 11% 32% 30% 7%	220
	11th to 20th	Day	14% 14% 40% 24% 8%	283
	21st to end	Day	17% 9% 30% 36% 7% 1	363
February	1st to 10th	Day	16% 10% 31% 33% 10%	345
	11th to 20th	Day	26% 9% 38% 23% 4	536
	21st to end	Day	21% 9% 35% 26% 9% 1	446
March	1st to 10th	Day	18% 10% 30% 31% 11%	540
	11th to 20th	Day	19% 7% 27% 36% 9% 1	540
	21st to end	Day	18% 7% 30% 36% 8% 1	594
April	1st to 10th	Day	17% 9% 27% 34% 11% 3	540
	11th to 20th	Day	14% 4 24% 38% 20% 1	532
	21st to end	Day	18% 4 20% 37% 19% 2	540
May	1st to 10th	Day	18% 4 20% 38% 17% 2	543
	11th to 20th	Day	19% 2 16% 38% 21% 4	567
	21st to end	Day	19% 3 10% 31% 28% 9%	617
June	1st to 10th	Day	13% 3 11% 33% 33% 8%	570
	11th to 20th	Day	12% 2 11% 31% 35% 9%	570
	21st to end	Day	9% 1 9% 34% 37% 10%	570
July	1st to 10th	Day	10% 3 5% 27% 42% 14%	565
	11th to 20th	Day	6% 1 4 25% 52% 12%	564
	21st to end	Day	7% 3 7% 30% 40% 12%	620
August	1st to 10th	Day	11% 2 6% 30% 40% 12%	566
	11th to 20th	Day	10% 2 4 26% 46% 13%	559
	21st to end	Day	8% 2 8% 31% 35% 16%	627
September	1st to 10th	Day	15% 1 9% 29% 31% 15%	570
	11th to 20th	Day	13% 2 7% 32% 36% 11%	570
	21st to end	Day	27% 3 14% 29% 22% 5%	570
October	1st to 10th	Day	20% 2 12% 29% 27% 10%	570
	11th to 20th	Day	18% 6% 19% 31% 21% 5%	570
	21st to end	Day	13% 8% 23% 29% 21% 6%	596
November	1st to 10th	Day	16% 6% 25% 28% 19% 5%	425
	11th to 20th	Day	17% 10% 30% 29% 13% 1	430
	21st to end	Day	18% 11% 26% 26% 16% 3	398
December	1st to 10th	Day	19% 8% 35% 29% 10% 1	220
	11th to 20th	Day	20% 8% 30% 30% 11%	220
	21st to end	Day	17% 7% 30% 30% 15%	242
January	1st to 10th	Night	17% 16% 35% 23% 8%	840
	11th to 20th	Night	18% 14% 34% 27% 6%	840
	21st to end	Night	18% 13% 37% 28% 3	924
February	1st to 10th	Night	21% 10% 35% 30% 4	840
	11th to 20th	Night	24% 12% 37% 25% 3	823
	21st to end	Night	20% 12% 31% 31% 6%	692
March	1st to 10th	Night	20% 10% 33% 28% 9%	840
	11th to 20th	Night	20% 8% 32% 31% 8% 2	840
	21st to end	Night	19% 8% 29% 36% 7% 1	924
April	1st to 10th	Night	21% 7% 32% 30% 9% 1	840
	11th to 20th	Night	14% 5% 26% 39% 15% 1	831
	21st to end	Night	18% 3 22% 40% 15% 1	840
May	1st to 10th	Night	18% 4 23% 40% 12% 2	765
	11th to 20th	Night	18% 3 19% 39% 19% 2	493
	21st to end	Night	19% 3 10% 33% 27% 7%	455
June	1st to 10th	Night	16% 3 11% 37% 30% 2	420
	11th to 20th	Night	12% 3 9% 38% 33% 6%	420
	21st to end	Night	8% 3 9% 40% 36% 4	420
July	1st to 10th	Night	8% 4 6% 32% 40% 9%	410
	11th to 20th	Night	7% 2 4 27% 49% 11%	408
	21st to end	Night	9% 2 7% 33% 43% 6%	593
August	1st to 10th	Night	11% 2 5% 35% 42% 6%	669
	11th to 20th	Night	11% 1 7% 30% 42% 8%	830
	21st to end	Night	11% 2 6% 33% 38% 10%	924
September	1st to 10th	Night	15% 2 9% 29% 36% 9%	840
	11th to 20th	Night	13% 2 9% 29% 39% 8%	840
	21st to end	Night	25% 4 13% 28% 25% 5%	840
October	1st to 10th	Night	19% 5% 15% 28% 24% 9%	840
	11th to 20th	Night	20% 6% 21% 31% 19% 2	840
	21st to end	Night	17% 7% 26% 29% 18% 4	913
November	1st to 10th	Night	17% 8% 23% 31% 17% 4	820
	11th to 20th	Night	18% 12% 29% 30% 11% 1	840
	21st to end	Night	15% 13% 27% 30% 14% 1	840
December	1st to 10th	Night	21% 10% 35% 22% 10% 2	840
	11th to 20th	Night	19% 11% 37% 26% 8%	840
	21st to end	Night	18% 10% 32% 31% 8%	924

Page generated at 2026-10-26 04:37:52. Version ac07

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