Ocean City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ocean City clear sky chart from 2005-11-05 to 2024-10-14.

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% 7% 2 6% 4 4 4 4 6% 8% 41%	101004
	Night	16% 7% 2 6% 4 4 4 3 5% 7% 42%	97535
Transparency	Day	41% 6% 13% 24% 15% 2	100761
	Night	43% 5% 11% 23% 16% 3	97402
Seeing	Day	17% 5% 20% 31% 22% 5%	15052
	Night	18% 7% 25% 30% 16% 3	24289

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	15% 8% 2 6% 3 3 3 3 4 6% 48%	2517
	11th to 20th	Day	15% 8% 2 7% 5% 4 4 3 5% 5% 42%	2566
	21st to end	Day	19% 10% 3 7% 4 4 4 3 4 4 37%	3124
February	1st to 10th	Day	15% 8% 2 6% 4 3 4 3 7% 8% 39%	1730
	11th to 20th	Day	17% 7% 2 6% 3 3 4 4 5% 6% 43%	1848
	21st to end	Day	18% 9% 3 7% 4 3 4 4 5% 6% 39%	1570
March	1st to 10th	Day	24% 8% 3 4 3 3 3 3 4 6% 40%	3116
	11th to 20th	Day	10% 4 1 5% 3 3 4 3 6% 9% 51%	3410
	21st to end	Day	19% 9% 2 5% 4 3 4 3 4 5% 42%	4092
April	1st to 10th	Day	15% 7% 3 5% 4 4 4 4 5% 6% 43%	2280
	11th to 20th	Day	13% 7% 2 4 4 4 4 3 5% 7% 46%	2254
	21st to end	Day	15% 6% 2 5% 4 4 5% 4 5% 8% 41%	2280
May	1st to 10th	Day	22% 12% 4 9% 5% 5% 4 3 5% 6% 26%	4011
	11th to 20th	Day	24% 9% 3 7% 4 3 4 3 4 6% 33%	4319
	21st to end	Day	10% 7% 2 7% 5% 4 5% 5% 7% 10% 39%	4837
June	1st to 10th	Day	12% 6% 1 4 4 4 5% 5% 9% 9% 39%	2660
	11th to 20th	Day	11% 5% 2 6% 5% 5% 5% 4 7% 9% 42%	2660
	21st to end	Day	9% 4 2 4 4 4 4 5% 9% 10% 44%	2660
July	1st to 10th	Day	7% 7% 2 6% 4 5% 6% 4 7% 11% 39%	4440
	11th to 20th	Day	10% 5% 2 6% 4 4 6% 5% 8% 11% 39%	4440
	21st to end	Day	9% 5% 2 8% 6% 6% 5% 5% 9% 10% 35%	4762
August	1st to 10th	Day	14% 6% 2 6% 4 5% 5% 4 6% 11% 38%	3992
	11th to 20th	Day	10% 5% 2 7% 5% 4 5% 4 6% 9% 43%	3730
	21st to end	Day	8% 5% 2 5% 4 4 5% 4 6% 8% 48%	4180
September	1st to 10th	Day	16% 5% 2 4 3 4 4 3 5% 8% 47%	2280
	11th to 20th	Day	11% 4 2 6% 4 4 3 3 5% 8% 48%	2217
	21st to end	Day	20% 6% 3 6% 5% 4 5% 3 4 7% 38%	2090
October	1st to 10th	Day	17% 6% 2 5% 4 4 4 3 4 6% 45%	1962
	11th to 20th	Day	16% 4 2 4 3 3 3 3 4 6% 51%	1830
	21st to end	Day	16% 6% 2 6% 4 3 5% 3 4 6% 45%	1896
November	1st to 10th	Day	15% 5% 2 5% 3 3 2 4 4 7% 50%	1671
	11th to 20th	Day	14% 5% 2 6% 4 4 3 3 5% 7% 47%	1710
	21st to end	Day	14% 5% 1 6% 5% 4 4 3 3 7% 48%	1672
December	1st to 10th	Day	17% 7% 2 5% 4 4 4 4 5% 7% 40%	1520
	11th to 20th	Day	16% 8% 3 5% 4 3 3 2 4 6% 46%	1906
	21st to end	Day	15% 7% 3 6% 4 2 4 4 5% 8% 41%	2772
January	1st to 10th	Night	16% 6% 2 5% 3 4 3 3 5% 6% 47%	4429
	11th to 20th	Night	20% 8% 2 5% 3 3 3 2 4 5% 45%	4379
	21st to end	Night	19% 10% 3 7% 4 4 3 3 4 5% 37%	4532
February	1st to 10th	Night	17% 7% 2 6% 4 3 4 4 5% 6% 42%	2448
	11th to 20th	Night	19% 8% 2 5% 4 4 4 4 5% 5% 42%	2218
	21st to end	Night	17% 8% 2 5% 3 3 4 3 5% 6% 44%	1884
March	1st to 10th	Night	22% 10% 3 7% 4 3 3 2 4 5% 38%	3724
	11th to 20th	Night	13% 5% 2 5% 4 4 4 4 5% 6% 47%	3547
	21st to end	Night	19% 10% 3 6% 4 3 3 3 3 4 43%	3538
April	1st to 10th	Night	17% 9% 3 7% 3 3 4 3 5% 6% 41%	1900
	11th to 20th	Night	13% 7% 2 6% 6% 4 5% 3 4 6% 45%	1875
	21st to end	Night	18% 6% 2 5% 4 5% 4 3 5% 7% 40%	1900
May	1st to 10th	Night	19% 11% 5% 9% 5% 5% 4 3 5% 7% 28%	2914
	11th to 20th	Night	25% 8% 3 7% 6% 4 4 3 4 5% 30%	2603
	21st to end	Night	13% 9% 3 8% 4 4 4 3 6% 8% 36%	2738
June	1st to 10th	Night	15% 7% 2 6% 5% 4 5% 3 6% 7% 41%	1520
	11th to 20th	Night	11% 6% 3 7% 5% 5% 4 4 7% 8% 42%	1520
	21st to end	Night	8% 5% 2 6% 5% 5% 5% 5% 7% 10% 42%	1520
July	1st to 10th	Night	8% 8% 3 8% 5% 6% 6% 4 7% 9% 37%	2520
	11th to 20th	Night	10% 6% 3 7% 5% 5% 5% 4 7% 10% 40%	2520
	21st to end	Night	14% 9% 3 8% 6% 5% 6% 5% 6% 8% 32%	2787
August	1st to 10th	Night	16% 8% 3 8% 5% 5% 4 4 6% 8% 32%	2907
	11th to 20th	Night	10% 5% 2 7% 4 5% 6% 4 6% 8% 44%	3097
	21st to end	Night	9% 4 2 5% 4 4 4 4 6% 7% 53%	3476
September	1st to 10th	Night	14% 8% 2 5% 4 4 4 3 5% 8% 43%	1900
	11th to 20th	Night	12% 5% 2 5% 3 4 4 4 5% 9% 48%	1962
	21st to end	Night	21% 7% 3 7% 3 3 4 3 5% 6% 37%	2090
October	1st to 10th	Night	19% 6% 2 5% 4 5% 3 3 4 6% 43%	2215
	11th to 20th	Night	17% 5% 2 5% 2 3 3 2 5% 6% 51%	2203
	21st to end	Night	16% 6% 2 6% 3 4 4 3 5% 6% 46%	2457
November	1st to 10th	Night	13% 5% 3 5% 3 3 4 3 5% 6% 51%	2407
	11th to 20th	Night	15% 7% 2 6% 5% 3 3 3 3 6% 48%	2470
	21st to end	Night	12% 6% 2 4 4 3 5% 3 5% 7% 48%	2503
December	1st to 10th	Night	18% 8% 3 5% 3 4 4 3 5% 6% 40%	2660
	11th to 20th	Night	18% 5% 2 5% 4 4 4 3 6% 7% 43%	3288
	21st to end	Night	14% 7% 3 7% 5% 4 5% 3 5% 7% 39%	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	39% 3 10% 28% 16% 3	2518
	11th to 20th	Day	44% 4 12% 22% 14% 5%	2566
	21st to end	Day	49% 6% 10% 21% 12% 3	3124
February	1st to 10th	Day	42% 6% 13% 25% 13% 1	1730
	11th to 20th	Day	42% 4 9% 26% 15% 4	1857
	21st to end	Day	45% 5% 10% 21% 14% 5%	1570
March	1st to 10th	Day	46% 4 8% 27% 12% 4	3119
	11th to 20th	Day	28% 5% 11% 32% 20% 3	3410
	21st to end	Day	44% 4 9% 17% 20% 5%	4092
April	1st to 10th	Day	41% 5% 12% 19% 17% 6%	2280
	11th to 20th	Day	37% 6% 13% 23% 17% 4	2254
	21st to end	Day	40% 7% 11% 19% 19% 5%	2280
May	1st to 10th	Day	59% 6% 9% 17% 8% 2	4024
	11th to 20th	Day	52% 6% 14% 19% 8% 1	4323
	21st to end	Day	39% 7% 14% 23% 17% 1	4837
June	1st to 10th	Day	36% 10% 14% 22% 15% 2	2660
	11th to 20th	Day	36% 9% 15% 27% 12% 2	2660
	21st to end	Day	31% 8% 16% 26% 18% 1	2660
July	1st to 10th	Day	38% 10% 19% 20% 12% 2	4370
	11th to 20th	Day	38% 7% 20% 26% 9% 1	4365
	21st to end	Day	41% 8% 15% 22% 13% 1	4610
August	1st to 10th	Day	41% 5% 19% 26% 9%	3979
	11th to 20th	Day	38% 5% 15% 31% 11% 1	3766
	21st to end	Day	32% 6% 12% 32% 17% 2	4180
September	1st to 10th	Day	36% 6% 16% 22% 19% 2	2280
	11th to 20th	Day	35% 5% 10% 25% 22% 3	2217
	21st to end	Day	47% 5% 10% 19% 17% 3	2090
October	1st to 10th	Day	40% 5% 11% 24% 17% 3	1962
	11th to 20th	Day	36% 4 10% 26% 22% 2	1831
	21st to end	Day	41% 4 10% 23% 20% 2	1896
November	1st to 10th	Day	36% 4 12% 28% 16% 4	1671
	11th to 20th	Day	39% 3 10% 22% 23% 3	1710
	21st to end	Day	38% 3 11% 30% 15% 3	1672
December	1st to 10th	Day	43% 5% 15% 21% 14% 2	1520
	11th to 20th	Day	41% 4 10% 28% 15% 3	1906
	21st to end	Day	40% 7% 14% 24% 14% 1	2772
January	1st to 10th	Night	38% 3 10% 29% 16% 4	4429
	11th to 20th	Night	44% 3 11% 25% 15% 2	4379
	21st to end	Night	49% 4 8% 25% 13% 2	4532
February	1st to 10th	Night	43% 3 13% 24% 14% 2	2448
	11th to 20th	Night	44% 4 9% 20% 19% 5%	2220
	21st to end	Night	42% 4 9% 22% 18% 5%	1884
March	1st to 10th	Night	49% 4 9% 22% 14% 2	3734
	11th to 20th	Night	37% 5% 11% 26% 16% 5%	3548
	21st to end	Night	48% 3 7% 16% 22% 5%	3538
April	1st to 10th	Night	44% 5% 8% 20% 18% 5%	1900
	11th to 20th	Night	41% 4 10% 20% 19% 5%	1875
	21st to end	Night	43% 6% 9% 18% 19% 5%	1900
May	1st to 10th	Night	56% 6% 8% 19% 10% 1	2920
	11th to 20th	Night	57% 5% 9% 17% 10% 1	2604
	21st to end	Night	45% 6% 15% 17% 15% 2	2739
June	1st to 10th	Night	42% 7% 11% 21% 18% 1	1520
	11th to 20th	Night	39% 8% 11% 27% 14% 2	1520
	21st to end	Night	37% 6% 14% 26% 14% 3	1520
July	1st to 10th	Night	43% 8% 16% 21% 10% 1	2480
	11th to 20th	Night	39% 5% 21% 26% 7% 1	2472
	21st to end	Night	50% 5% 15% 16% 14% 1	2698
August	1st to 10th	Night	49% 6% 17% 19% 8%	2896
	11th to 20th	Night	37% 6% 13% 33% 11% 1	3127
	21st to end	Night	31% 5% 10% 30% 22% 2	3476
September	1st to 10th	Night	41% 5% 12% 22% 17% 4	1900
	11th to 20th	Night	34% 5% 11% 25% 22% 3	1962
	21st to end	Night	48% 6% 7% 19% 18% 2	2090
October	1st to 10th	Night	43% 5% 10% 21% 19% 2	2215
	11th to 20th	Night	36% 4 10% 28% 19% 3	2207
	21st to end	Night	41% 4 10% 25% 18% 3	2457
November	1st to 10th	Night	35% 4 11% 26% 19% 5%	2407
	11th to 20th	Night	40% 4 10% 21% 20% 5%	2470
	21st to end	Night	36% 4 12% 26% 19% 2	2503
December	1st to 10th	Night	45% 4 12% 22% 13% 2	2660
	11th to 20th	Night	41% 4 12% 21% 19% 3	3288
	21st to end	Night	43% 5% 16% 25% 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	15% 14% 28% 33% 8% 2	180
	11th to 20th	Day	16% 14% 34% 28% 7% 1	195
	21st to end	Day	21% 7% 33% 26% 13% 1	297
February	1st to 10th	Day	20% 9% 29% 32% 9% 1	290
	11th to 20th	Day	24% 11% 36% 24% 5%	456
	21st to end	Day	24% 10% 32% 25% 8% 1	382
March	1st to 10th	Day	17% 9% 36% 30% 8% 1	460
	11th to 20th	Day	17% 8% 33% 31% 8% 2	460
	21st to end	Day	19% 8% 30% 32% 9% 1	506
April	1st to 10th	Day	18% 8% 31% 31% 10% 1	460
	11th to 20th	Day	14% 9% 26% 38% 11% 1	452
	21st to end	Day	21% 6% 24% 36% 12% 1	460
May	1st to 10th	Day	24% 4 22% 34% 13% 2	463
	11th to 20th	Day	23% 3 17% 37% 17% 2	487
	21st to end	Day	17% 2 12% 31% 30% 7%	529
June	1st to 10th	Day	17% 1 12% 36% 28% 5%	490
	11th to 20th	Day	13% 2 13% 36% 30% 6%	490
	21st to end	Day	10% 2 10% 41% 33% 4	490
July	1st to 10th	Day	10% 1 7% 31% 37% 13%	485
	11th to 20th	Day	7% 1 5% 32% 45% 10%	484
	21st to end	Day	10% 2 8% 38% 36% 6%	532
August	1st to 10th	Day	11% 2 7% 35% 37% 7%	486
	11th to 20th	Day	11% 2 7% 30% 39% 11%	479
	21st to end	Day	11% 2 7% 33% 33% 13%	539
September	1st to 10th	Day	18% 2 13% 23% 32% 12%	490
	11th to 20th	Day	15% 3 11% 29% 34% 8%	490
	21st to end	Day	25% 4 15% 33% 20% 3	490
October	1st to 10th	Day	23% 3 14% 27% 26% 7%	490
	11th to 20th	Day	17% 5% 18% 30% 24% 6%	462
	21st to end	Day	18% 8% 26% 28% 15% 5%	453
November	1st to 10th	Day	17% 6% 24% 30% 21% 3	365
	11th to 20th	Day	12% 12% 34% 26% 15% 1	370
	21st to end	Day	15% 14% 26% 27% 16% 2	332
December	1st to 10th	Day	23% 11% 29% 24% 13% 1	180
	11th to 20th	Day	21% 9% 30% 28% 12%	180
	21st to end	Day	20% 11% 28% 25% 15% 2	198
January	1st to 10th	Night	20% 17% 34% 21% 7%	760
	11th to 20th	Night	21% 15% 32% 26% 6%	760
	21st to end	Night	19% 14% 37% 27% 3	836
February	1st to 10th	Night	21% 11% 35% 28% 5%	760
	11th to 20th	Night	23% 12% 42% 21% 2	743
	21st to end	Night	20% 12% 35% 27% 5% 1	628
March	1st to 10th	Night	19% 9% 37% 29% 5% 1	760
	11th to 20th	Night	21% 10% 33% 28% 7% 2	760
	21st to end	Night	22% 6% 33% 31% 7% 1	836
April	1st to 10th	Night	21% 8% 35% 28% 8% 1	760
	11th to 20th	Night	16% 5% 28% 38% 13%	751
	21st to end	Night	21% 4 28% 34% 12% 1	760
May	1st to 10th	Night	19% 5% 24% 36% 13% 3	624
	11th to 20th	Night	21% 3 24% 35% 16% 2	443
	21st to end	Night	18% 2 12% 32% 29% 7%	411
June	1st to 10th	Night	21% 2 12% 36% 26% 3	380
	11th to 20th	Night	14% 1 13% 39% 31% 2	380
	21st to end	Night	9% 2 11% 45% 29% 4	380
July	1st to 10th	Night	12% 1 10% 39% 32% 6%	370
	11th to 20th	Night	7% 2 7% 35% 44% 6%	368
	21st to end	Night	10% 2 9% 38% 36% 5%	440
August	1st to 10th	Night	12% 2 8% 34% 39% 5%	610
	11th to 20th	Night	12% 1 11% 35% 33% 8%	750
	21st to end	Night	12% 1 8% 33% 37% 8%	836
September	1st to 10th	Night	18% 2 13% 29% 29% 9%	760
	11th to 20th	Night	15% 2 12% 31% 32% 9%	760
	21st to end	Night	25% 3 17% 29% 23% 3	760
October	1st to 10th	Night	22% 4 18% 27% 21% 8%	760
	11th to 20th	Night	20% 7% 21% 33% 19% 1	735
	21st to end	Night	20% 8% 30% 27% 13% 2	792
November	1st to 10th	Night	16% 10% 25% 30% 15% 4	740
	11th to 20th	Night	18% 12% 30% 28% 12% 1	760
	21st to end	Night	15% 13% 31% 29% 10% 2	760
December	1st to 10th	Night	21% 13% 34% 21% 9% 2	760
	11th to 20th	Night	19% 12% 37% 25% 6% 1	760
	21st to end	Night	19% 12% 33% 30% 6%	836

Page generated at 2024-10-11 10:49:57. Version ac07

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