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 2026-07-01.

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 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	14% 6% 2 6% 4 4 4 4 5% 8% 43%	137716
	Night	15% 7% 2 6% 4 4 4 3 5% 7% 43%	134626
Transparency	Day	40% 5% 12% 24% 16% 3	141271
	Night	41% 4 11% 23% 17% 4	139158
Seeing	Day	17% 5% 20% 32% 22% 5%	17239
	Night	18% 8% 25% 30% 16% 3	26507

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	13% 6% 2 6% 4 4 3 3 4 5% 51%	4661
	11th to 20th	Day	14% 6% 2 7% 4 4 3 3 3 4 50%	4752
	21st to end	Day	15% 7% 2 5% 4 4 4 4 5% 6% 46%	5780
February	1st to 10th	Day	14% 8% 2 6% 4 3 4 4 7% 8% 40%	1913
	11th to 20th	Day	17% 7% 3 6% 4 4 4 4 5% 6% 42%	2048
	21st to end	Day	17% 8% 3 6% 4 3 4 4 5% 6% 40%	1730
March	1st to 10th	Day	18% 6% 2 4 3 3 3 3 4 6% 48%	4576
	11th to 20th	Day	11% 10% 2 5% 3 3 3 3 5% 7% 47%	4990
	21st to end	Day	16% 7% 2 5% 4 4 4 4 5% 6% 45%	5998
April	1st to 10th	Day	16% 8% 3 5% 3 4 4 4 5% 6% 43%	2520
	11th to 20th	Day	13% 7% 2 5% 4 4 4 4 5% 7% 45%	2494
	21st to end	Day	15% 6% 2 6% 4 4 5% 4 5% 9% 41%	2520
May	1st to 10th	Day	20% 9% 3 8% 4 4 4 3 5% 6% 34%	7461
	11th to 20th	Day	19% 7% 2 6% 3 3 3 3 4 7% 41%	8059
	21st to end	Day	22% 8% 3 6% 4 4 4 3 6% 7% 33%	9060
June	1st to 10th	Day	12% 6% 1 5% 4 4 5% 4 8% 9% 40%	2940
	11th to 20th	Day	11% 5% 2 6% 5% 5% 5% 4 6% 9% 42%	2940
	21st to end	Day	9% 4 2 4 4 4 4 5% 9% 10% 44%	2940
July	1st to 10th	Day	8% 6% 2 6% 4 5% 5% 4 6% 11% 43%	6360
	11th to 20th	Day	11% 6% 3 6% 5% 5% 6% 6% 8% 11% 32%	6360
	21st to end	Day	8% 5% 2 7% 5% 5% 5% 4 7% 10% 42%	6846
August	1st to 10th	Day	14% 6% 2 6% 4 5% 5% 4 6% 10% 39%	4119
	11th to 20th	Day	11% 5% 2 7% 5% 4 5% 4 6% 9% 43%	3850
	21st to end	Day	8% 5% 2 5% 4 4 4 4 6% 8% 49%	4312
September	1st to 10th	Day	16% 5% 2 4 3 4 4 3 5% 8% 47%	2400
	11th to 20th	Day	12% 4 2 6% 4 4 3 3 5% 8% 48%	2333
	21st to end	Day	20% 6% 3 6% 5% 4 5% 3 4 7% 38%	2200
October	1st to 10th	Day	17% 5% 2 5% 4 4 4 3 4 6% 46%	2065
	11th to 20th	Day	16% 5% 2 4 3 3 3 3 4 5% 51%	2000
	21st to end	Day	15% 6% 2 5% 4 3 5% 3 5% 6% 47%	2106
November	1st to 10th	Day	14% 5% 2 5% 3 3 2 4 4 7% 51%	1851
	11th to 20th	Day	14% 5% 2 6% 4 4 3 4 5% 7% 48%	1890
	21st to end	Day	15% 5% 2 6% 5% 3 4 3 4 7% 48%	1848
December	1st to 10th	Day	12% 5% 2 5% 3 4 4 4 5% 7% 50%	2680
	11th to 20th	Day	19% 8% 2 5% 3 3 3 2 3 6% 46%	3066
	21st to end	Day	13% 7% 3 6% 4 2 4 4 5% 8% 45%	4048
January	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 5% 6% 50%	8234
	11th to 20th	Night	15% 7% 2 5% 3 3 3 3 4 5% 51%	8118
	21st to end	Night	14% 7% 2 6% 3 3 3 3 4 6% 47%	8401
February	1st to 10th	Night	17% 7% 2 6% 4 4 4 4 5% 6% 42%	2705
	11th to 20th	Night	20% 7% 2 5% 4 3 4 4 5% 5% 42%	2458
	21st to end	Night	16% 9% 2 5% 4 3 4 4 5% 6% 43%	2076
March	1st to 10th	Night	17% 8% 2 6% 3 3 3 2 4 5% 46%	5484
	11th to 20th	Night	12% 11% 3 5% 3 3 3 3 4 5% 46%	5187
	21st to end	Night	16% 8% 2 6% 4 3 4 4 4 5% 44%	5174
April	1st to 10th	Night	17% 8% 3 7% 3 3 4 3 5% 6% 41%	2100
	11th to 20th	Night	13% 7% 2 6% 5% 4 4 3 4 7% 45%	2075
	21st to end	Night	17% 6% 2 5% 4 5% 4 3 6% 7% 41%	2100
May	1st to 10th	Night	16% 8% 4 7% 4 4 5% 4 6% 9% 34%	5423
	11th to 20th	Night	18% 8% 3 7% 4 4 4 3 4 7% 39%	4843
	21st to end	Night	26% 10% 3 7% 4 4 4 3 4 6% 31%	5114
June	1st to 10th	Night	15% 7% 2 6% 5% 4 5% 3 6% 6% 42%	1680
	11th to 20th	Night	12% 6% 3 6% 5% 5% 4 4 7% 8% 40%	1680
	21st to end	Night	8% 6% 2 6% 5% 5% 5% 5% 7% 10% 41%	1680
July	1st to 10th	Night	9% 8% 2 8% 6% 6% 6% 4 7% 9% 35%	3600
	11th to 20th	Night	13% 7% 3 8% 5% 6% 5% 5% 7% 9% 31%	3600
	21st to end	Night	11% 7% 2 7% 5% 5% 6% 5% 6% 9% 38%	4002
August	1st to 10th	Night	16% 8% 3 8% 5% 5% 4 4 6% 8% 32%	2999
	11th to 20th	Night	10% 5% 2 6% 4 5% 6% 4 6% 8% 44%	3197
	21st to end	Night	9% 4 2 5% 4 4 4 4 6% 7% 53%	3586
September	1st to 10th	Night	14% 7% 2 6% 4 4 4 3 5% 8% 44%	2000
	11th to 20th	Night	13% 5% 2 5% 3 3 4 4 5% 8% 48%	2065
	21st to end	Night	21% 7% 3 7% 3 4 4 3 5% 6% 37%	2200
October	1st to 10th	Night	18% 5% 2 5% 4 5% 3 3 4 6% 44%	2332
	11th to 20th	Night	17% 5% 2 4 3 3 3 2 5% 5% 51%	2400
	21st to end	Night	15% 5% 2 5% 3 4 4 3 5% 6% 48%	2731
November	1st to 10th	Night	12% 5% 2 5% 3 3 4 3 5% 6% 52%	2667
	11th to 20th	Night	15% 7% 2 6% 5% 3 3 3 4 6% 48%	2730
	21st to end	Night	12% 6% 2 5% 4 3 4 3 5% 7% 48%	2767
December	1st to 10th	Night	12% 6% 2 5% 3 3 4 3 5% 7% 50%	4720
	11th to 20th	Night	21% 6% 2 5% 3 3 3 3 5% 7% 42%	5348
	21st to end	Night	14% 7% 3 6% 4 4 4 3 5% 7% 43%	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	38% 2 7% 27% 23% 3	4662
	11th to 20th	Day	40% 3 7% 23% 20% 8%	4782
	21st to end	Day	41% 3 9% 31% 13% 3	5780
February	1st to 10th	Day	42% 5% 13% 24% 13% 2	1913
	11th to 20th	Day	44% 4 9% 24% 16% 4	2057
	21st to end	Day	45% 4 9% 22% 15% 4	1730
March	1st to 10th	Day	39% 3 8% 24% 18% 8%	4579
	11th to 20th	Day	37% 4 9% 27% 18% 5%	4990
	21st to end	Day	41% 4 10% 16% 21% 7%	5998
April	1st to 10th	Day	42% 5% 12% 18% 18% 6%	2520
	11th to 20th	Day	38% 6% 13% 23% 17% 4	2494
	21st to end	Day	40% 6% 11% 20% 19% 4	2520
May	1st to 10th	Day	52% 4 12% 20% 11% 1	7471
	11th to 20th	Day	44% 4 10% 27% 13% 1	8063
	21st to end	Day	51% 4 10% 22% 13% 1	9061
June	1st to 10th	Day	36% 9% 13% 23% 16% 2	2940
	11th to 20th	Day	37% 8% 15% 26% 12% 2	2940
	21st to end	Day	32% 8% 16% 26% 18% 1	2940
July	1st to 10th	Day	36% 8% 19% 21% 14% 1	6290
	11th to 20th	Day	44% 7% 21% 21% 6% 1	6285
	21st to end	Day	36% 7% 12% 26% 19% 1	6649
August	1st to 10th	Day	40% 5% 19% 26% 9%	4106
	11th to 20th	Day	38% 5% 15% 31% 11% 1	3886
	21st to end	Day	32% 6% 11% 32% 17% 2	4312
September	1st to 10th	Day	36% 5% 16% 23% 18% 2	2400
	11th to 20th	Day	35% 4 10% 26% 21% 3	2333
	21st to end	Day	47% 5% 11% 18% 16% 3	2200
October	1st to 10th	Day	33% 3 9% 25% 25% 5%	3364
	11th to 20th	Day	27% 3 7% 27% 29% 7%	3240
	21st to end	Day	27% 2 12% 28% 23% 6%	3383
November	1st to 10th	Day	35% 4 12% 28% 16% 4	1851
	11th to 20th	Day	38% 3 10% 23% 23% 3	1890
	21st to end	Day	39% 3 11% 30% 15% 3	1848
December	1st to 10th	Day	35% 4 20% 23% 16% 3	2680
	11th to 20th	Day	43% 3 10% 28% 13% 3	3066
	21st to end	Day	38% 6% 13% 23% 19% 1	4048
January	1st to 10th	Night	37% 2 11% 25% 19% 5%	8234
	11th to 20th	Night	38% 2 8% 24% 20% 9%	8163
	21st to end	Night	40% 2 9% 28% 18% 3	8401
February	1st to 10th	Night	44% 3 13% 24% 14% 2	2705
	11th to 20th	Night	44% 4 9% 20% 18% 5%	2460
	21st to end	Night	43% 3 9% 23% 18% 5%	2076
March	1st to 10th	Night	42% 3 9% 22% 14% 10%	5494
	11th to 20th	Night	41% 4 11% 23% 15% 6%	5188
	21st to end	Night	44% 3 9% 16% 24% 4	5174
April	1st to 10th	Night	44% 4 9% 19% 18% 5%	2100
	11th to 20th	Night	41% 4 10% 20% 20% 5%	2075
	21st to end	Night	43% 5% 9% 18% 19% 5%	2100
May	1st to 10th	Night	48% 4 12% 23% 11% 2	5429
	11th to 20th	Night	47% 4 10% 24% 14% 1	4844
	21st to end	Night	55% 4 9% 17% 13% 1	5115
June	1st to 10th	Night	42% 6% 11% 21% 19% 2	1680
	11th to 20th	Night	40% 8% 11% 25% 14% 2	1680
	21st to end	Night	38% 5% 14% 26% 14% 3	1680
July	1st to 10th	Night	45% 7% 14% 21% 12% 1	3560
	11th to 20th	Night	50% 5% 18% 21% 5% 1	3552
	21st to end	Night	43% 5% 14% 21% 17%	3884
August	1st to 10th	Night	49% 6% 17% 20% 8%	2988
	11th to 20th	Night	37% 6% 13% 32% 11% 1	3227
	21st to end	Night	31% 5% 10% 30% 22% 2	3586
September	1st to 10th	Night	41% 5% 11% 23% 17% 4	2000
	11th to 20th	Night	34% 5% 11% 26% 21% 3	2065
	21st to end	Night	49% 6% 7% 19% 17% 2	2200
October	1st to 10th	Night	39% 4 9% 24% 22% 2	3813
	11th to 20th	Night	25% 3 11% 25% 29% 6%	3899
	21st to end	Night	26% 2 12% 31% 24% 5%	4404
November	1st to 10th	Night	34% 3 10% 26% 21% 5%	2667
	11th to 20th	Night	40% 4 9% 21% 21% 5%	2730
	21st to end	Night	36% 4 12% 26% 20% 2	2767
December	1st to 10th	Night	36% 3 14% 26% 18% 4	4720
	11th to 20th	Night	44% 3 12% 21% 16% 4	5348
	21st to end	Night	42% 4 14% 21% 18% 2	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	15% 14% 29% 32% 8% 2	220
	11th to 20th	Day	16% 13% 36% 28% 6%	239
	21st to end	Day	19% 7% 36% 27% 11% 1	363
February	1st to 10th	Day	18% 8% 31% 32% 10% 1	353
	11th to 20th	Day	25% 11% 36% 24% 5%	536
	21st to end	Day	24% 9% 32% 28% 8%	446
March	1st to 10th	Day	18% 8% 35% 30% 8% 1	540
	11th to 20th	Day	18% 8% 33% 31% 8% 2	540
	21st to end	Day	18% 7% 32% 33% 9% 1	594
April	1st to 10th	Day	19% 8% 30% 31% 10% 2	540
	11th to 20th	Day	15% 8% 26% 37% 13% 1	532
	21st to end	Day	20% 5% 22% 38% 14% 1	540
May	1st to 10th	Day	23% 4 23% 35% 13% 2	543
	11th to 20th	Day	22% 3 17% 37% 19% 2	567
	21st to end	Day	21% 2 13% 30% 28% 6%	617
June	1st to 10th	Day	17% 1 11% 36% 29% 6%	570
	11th to 20th	Day	14% 2 14% 37% 29% 5%	570
	21st to end	Day	11% 2 9% 38% 35% 5%	570
July	1st to 10th	Day	11% 1 7% 31% 38% 13%	525
	11th to 20th	Day	8% 2 5% 31% 45% 10%	524
	21st to end	Day	10% 2 7% 36% 38% 7%	576
August	1st to 10th	Day	11% 2 7% 36% 36% 7%	526
	11th to 20th	Day	12% 2 7% 28% 40% 11%	519
	21st to end	Day	11% 2 8% 34% 34% 12%	583
September	1st to 10th	Day	18% 2 13% 24% 32% 11%	530
	11th to 20th	Day	15% 3 10% 29% 35% 8%	530
	21st to end	Day	25% 4 14% 33% 21% 3	530
October	1st to 10th	Day	22% 3 14% 26% 26% 9%	530
	11th to 20th	Day	18% 5% 19% 30% 21% 6%	530
	21st to end	Day	16% 7% 25% 30% 16% 6%	531
November	1st to 10th	Day	16% 5% 25% 32% 19% 3	425
	11th to 20th	Day	12% 14% 33% 27% 13% 1	430
	21st to end	Day	16% 13% 28% 27% 14% 2	388
December	1st to 10th	Day	22% 11% 28% 26% 12%	220
	11th to 20th	Day	20% 10% 30% 29% 11%	220
	21st to end	Day	19% 9% 30% 26% 14% 1	242
January	1st to 10th	Night	19% 18% 35% 22% 7%	840
	11th to 20th	Night	21% 15% 33% 25% 6%	840
	21st to end	Night	18% 14% 39% 26% 3	924
February	1st to 10th	Night	21% 11% 36% 27% 5%	840
	11th to 20th	Night	24% 12% 40% 22% 2	823
	21st to end	Night	19% 12% 35% 29% 5% 1	692
March	1st to 10th	Night	19% 9% 37% 29% 5% 1	840
	11th to 20th	Night	20% 10% 32% 29% 8% 2	840
	21st to end	Night	21% 6% 33% 32% 7% 1	924
April	1st to 10th	Night	21% 8% 34% 29% 8% 1	840
	11th to 20th	Night	17% 4 28% 39% 12%	831
	21st to end	Night	20% 4 26% 35% 13% 1	840
May	1st to 10th	Night	19% 5% 25% 36% 13% 2	690
	11th to 20th	Night	20% 3 23% 37% 16% 2	490
	21st to end	Night	21% 2 13% 31% 27% 6%	455
June	1st to 10th	Night	20% 2 11% 38% 26% 3	420
	11th to 20th	Night	15% 1 14% 39% 30% 2	420
	21st to end	Night	10% 2 10% 43% 30% 4	420
July	1st to 10th	Night	12% 1 9% 39% 32% 6%	390
	11th to 20th	Night	8% 2 7% 34% 43% 6%	388
	21st to end	Night	9% 2 9% 38% 37% 5%	464
August	1st to 10th	Night	12% 2 7% 35% 38% 5%	642
	11th to 20th	Night	13% 1 10% 34% 34% 8%	790
	21st to end	Night	12% 2 8% 34% 36% 8%	880
September	1st to 10th	Night	18% 2 13% 30% 29% 9%	800
	11th to 20th	Night	16% 2 11% 31% 32% 8%	800
	21st to end	Night	25% 3 17% 29% 24% 3	800
October	1st to 10th	Night	21% 3 18% 27% 22% 9%	800
	11th to 20th	Night	20% 8% 22% 32% 18% 2	800
	21st to end	Night	19% 8% 30% 28% 14% 2	880
November	1st to 10th	Night	15% 10% 25% 32% 15% 3	820
	11th to 20th	Night	18% 12% 32% 27% 11% 1	840
	21st to end	Night	14% 14% 32% 29% 10% 1	840
December	1st to 10th	Night	20% 13% 36% 21% 9% 2	840
	11th to 20th	Night	20% 13% 36% 25% 7%	840
	21st to end	Night	19% 12% 33% 30% 6%	924

Page generated at 2026-06-28 02:10:44. Version ac07

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