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 2024-11-02.

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% 7% 2 6% 4 4 4 4 6% 8% 41%	101086
	Night	15% 7% 3 6% 4 4 4 3 5% 7% 42%	97793
Transparency	Day	40% 5% 14% 25% 14% 3	100876
	Night	43% 4 11% 24% 16% 3	97673
Seeing	Day	16% 5% 18% 31% 24% 6%	15192
	Night	17% 7% 23% 31% 19% 3	24528

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 3 3 3 4 8% 48%	2517
	11th to 20th	Day	13% 9% 3 7% 4 4 3 3 4 6% 43%	2694
	21st to end	Day	13% 11% 4 10% 5% 4 5% 3 5% 5% 36%	3124
February	1st to 10th	Day	12% 8% 3 7% 5% 4 5% 4 7% 7% 38%	1723
	11th to 20th	Day	18% 7% 2 4 4 4 4 3 5% 7% 43%	1848
	21st to end	Day	16% 10% 3 6% 4 4 4 4 5% 7% 38%	1570
March	1st to 10th	Day	23% 7% 3 6% 4 4 3 2 4 6% 38%	3119
	11th to 20th	Day	10% 3 2 4 3 3 3 3 6% 8% 54%	3480
	21st to end	Day	18% 10% 3 5% 4 3 3 3 5% 6% 40%	4054
April	1st to 10th	Day	15% 6% 2 6% 5% 3 4 3 5% 7% 44%	2280
	11th to 20th	Day	11% 7% 2 5% 4 3 4 3 5% 8% 48%	2254
	21st to end	Day	14% 6% 2 5% 4 4 4 4 5% 8% 43%	2280
May	1st to 10th	Day	18% 10% 4 9% 6% 6% 5% 3 6% 6% 27%	3883
	11th to 20th	Day	20% 10% 3 7% 5% 5% 4 4 5% 7% 29%	4302
	21st to end	Day	10% 6% 3 6% 5% 6% 5% 4 6% 11% 38%	4823
June	1st to 10th	Day	11% 5% 2 5% 4 5% 5% 5% 8% 10% 41%	2660
	11th to 20th	Day	10% 6% 2 6% 4 4 4 4 6% 10% 44%	2660
	21st to end	Day	6% 4 2 6% 5% 5% 5% 4 7% 11% 45%	2660
July	1st to 10th	Day	6% 5% 2 5% 4 4 5% 5% 7% 11% 45%	4440
	11th to 20th	Day	9% 6% 3 6% 5% 5% 5% 5% 8% 11% 38%	4440
	21st to end	Day	9% 5% 2 8% 6% 6% 6% 6% 9% 11% 34%	4603
August	1st to 10th	Day	12% 7% 3 6% 4 5% 5% 5% 8% 11% 35%	3994
	11th to 20th	Day	8% 5% 2 7% 5% 5% 6% 4 7% 8% 43%	3730
	21st to end	Day	9% 4 2 5% 3 4 5% 4 7% 11% 48%	4180
September	1st to 10th	Day	13% 5% 2 5% 4 4 5% 4 6% 7% 44%	2280
	11th to 20th	Day	10% 6% 2 6% 4 4 5% 3 5% 7% 47%	2237
	21st to end	Day	18% 7% 3 6% 5% 4 4 2 5% 7% 37%	2090
October	1st to 10th	Day	15% 5% 2 5% 4 3 3 4 6% 7% 46%	1929
	11th to 20th	Day	17% 5% 2 4 3 4 3 3 4 5% 50%	1900
	21st to end	Day	13% 6% 2 6% 4 3 4 2 4 7% 48%	2057
November	1st to 10th	Day	14% 5% 2 5% 4 3 5% 3 6% 7% 46%	1681
	11th to 20th	Day	13% 6% 3 5% 6% 4 4 3 4 6% 46%	1710
	21st to end	Day	15% 6% 2 5% 4 3 3 3 4 6% 48%	1682
December	1st to 10th	Day	15% 6% 2 6% 4 4 5% 4 6% 7% 40%	1520
	11th to 20th	Day	14% 8% 3 6% 4 3 3 2 5% 6% 46%	1910
	21st to end	Day	14% 6% 2 5% 4 4 4 3 6% 9% 44%	2772
January	1st to 10th	Night	14% 7% 2 5% 3 4 4 3 5% 7% 47%	4429
	11th to 20th	Night	17% 8% 3 6% 4 3 4 2 3 5% 45%	4248
	21st to end	Night	17% 10% 4 7% 4 4 3 3 4 5% 40%	4532
February	1st to 10th	Night	17% 8% 3 6% 3 3 3 3 5% 6% 42%	2456
	11th to 20th	Night	18% 8% 3 5% 4 4 4 3 5% 5% 42%	2218
	21st to end	Night	18% 7% 2 5% 4 3 4 2 4 6% 45%	1884
March	1st to 10th	Night	23% 9% 3 6% 4 3 4 3 4 6% 36%	3716
	11th to 20th	Night	15% 6% 2 5% 3 3 4 3 6% 8% 47%	3480
	21st to end	Night	18% 11% 3 6% 3 3 3 2 4 4 42%	3576
April	1st to 10th	Night	17% 8% 3 6% 5% 3 4 4 5% 6% 40%	1900
	11th to 20th	Night	12% 7% 2 6% 4 4 4 3 4 6% 48%	1875
	21st to end	Night	15% 7% 2 5% 4 4 5% 4 6% 7% 40%	1900
May	1st to 10th	Night	16% 10% 5% 10% 6% 5% 4 3 6% 6% 30%	3011
	11th to 20th	Night	23% 10% 4 7% 4 4 3 3 5% 7% 31%	2605
	21st to end	Night	11% 10% 4 9% 4 5% 4 3 6% 7% 37%	2732
June	1st to 10th	Night	13% 7% 3 8% 4 4 5% 3 6% 9% 39%	1520
	11th to 20th	Night	10% 5% 2 5% 5% 6% 6% 4 7% 10% 40%	1520
	21st to end	Night	7% 6% 2 6% 5% 7% 5% 5% 7% 9% 40%	1520
July	1st to 10th	Night	8% 6% 3 6% 5% 6% 5% 6% 8% 12% 35%	2520
	11th to 20th	Night	8% 7% 2 6% 6% 5% 6% 4 7% 10% 39%	2520
	21st to end	Night	13% 8% 3 8% 6% 5% 5% 4 7% 10% 31%	2947
August	1st to 10th	Night	14% 9% 3 8% 5% 5% 5% 3 6% 9% 32%	2889
	11th to 20th	Night	9% 6% 3 7% 5% 5% 5% 4 7% 8% 41%	3097
	21st to end	Night	8% 5% 2 5% 4 4 4 3 5% 7% 53%	3476
September	1st to 10th	Night	13% 7% 3 6% 3 4 4 3 5% 8% 44%	1900
	11th to 20th	Night	11% 5% 2 7% 5% 3 4 4 5% 8% 46%	1941
	21st to end	Night	21% 7% 3 6% 4 4 5% 3 5% 7% 36%	2090
October	1st to 10th	Night	17% 7% 2 5% 3 4 3 3 6% 7% 44%	2248
	11th to 20th	Night	17% 5% 2 5% 3 3 4 2 4 6% 50%	2280
	21st to end	Night	14% 7% 2 5% 3 4 4 3 4 7% 47%	2540
November	1st to 10th	Night	14% 6% 2 5% 4 3 4 3 5% 6% 48%	2431
	11th to 20th	Night	16% 6% 2 6% 4 4 4 3 5% 6% 46%	2470
	21st to end	Night	12% 6% 2 4 4 3 4 3 5% 6% 50%	2493
December	1st to 10th	Night	16% 8% 3 6% 4 4 4 3 6% 6% 39%	2660
	11th to 20th	Night	18% 6% 2 6% 4 4 4 2 5% 7% 42%	3285
	21st to end	Night	13% 8% 3 6% 5% 4 4 4 6% 7% 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	49% 3 8% 21% 15% 4	3119
	11th to 20th	Day	28% 4 11% 32% 21% 4	3480
	21st to end	Day	46% 3 10% 19% 18% 4	4054
April	1st to 10th	Day	40% 4 11% 22% 19% 5%	2280
	11th to 20th	Day	35% 3 11% 26% 19% 5%	2254
	21st to end	Day	39% 5% 13% 21% 18% 4	2280
May	1st to 10th	Day	56% 4 11% 19% 7% 2	3918
	11th to 20th	Day	55% 3 14% 19% 8% 2	4306
	21st to end	Day	39% 7% 15% 22% 16% 2	4837
June	1st to 10th	Day	36% 6% 17% 25% 14% 2	2660
	11th to 20th	Day	35% 6% 16% 27% 13% 3	2660
	21st to end	Day	31% 7% 17% 28% 15% 2	2660
July	1st to 10th	Day	33% 8% 24% 21% 12% 2	4370
	11th to 20th	Day	38% 6% 22% 26% 6% 1	4365
	21st to end	Day	39% 10% 17% 21% 13% 1	4456
August	1st to 10th	Day	40% 7% 21% 25% 6%	3981
	11th to 20th	Day	37% 6% 15% 31% 10% 1	3766
	21st to end	Day	30% 5% 14% 31% 18% 2	4180
September	1st to 10th	Day	38% 6% 15% 21% 17% 3	2280
	11th to 20th	Day	36% 4 11% 27% 20% 2	2237
	21st to end	Day	47% 5% 9% 21% 16% 3	2090
October	1st to 10th	Day	37% 4 12% 27% 17% 4	1929
	11th to 20th	Day	37% 3 7% 28% 21% 3	1900
	21st to end	Day	37% 3 8% 27% 20% 4	2057
November	1st to 10th	Day	39% 4 9% 29% 16% 4	1681
	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	51% 3 9% 23% 13% 2	3716
	11th to 20th	Night	36% 3 8% 28% 21% 4	3480
	21st to end	Night	48% 2 7% 20% 18% 5%	3576
April	1st to 10th	Night	46% 3 9% 20% 18% 5%	1900
	11th to 20th	Night	38% 3 11% 21% 20% 6%	1875
	21st to end	Night	42% 4 11% 22% 18% 3	1900
May	1st to 10th	Night	55% 3 12% 20% 9% 1	3041
	11th to 20th	Night	55% 3 12% 20% 8% 1	2606
	21st to end	Night	47% 5% 14% 18% 15% 2	2739
June	1st to 10th	Night	43% 5% 11% 23% 16% 1	1520
	11th to 20th	Night	37% 9% 12% 25% 16% 2	1520
	21st to end	Night	37% 7% 15% 24% 15% 2	1520
July	1st to 10th	Night	40% 9% 18% 21% 11% 1	2480
	11th to 20th	Night	39% 6% 21% 26% 8%	2472
	21st to end	Night	46% 7% 17% 17% 12%	2853
August	1st to 10th	Night	49% 6% 15% 22% 7%	2878
	11th to 20th	Night	39% 6% 15% 28% 12% 1	3127
	21st to end	Night	31% 5% 11% 27% 25% 1	3476
September	1st to 10th	Night	39% 5% 15% 20% 16% 4	1900
	11th to 20th	Night	36% 6% 10% 26% 20% 2	1941
	21st to end	Night	48% 6% 9% 19% 16% 2	2090
October	1st to 10th	Night	41% 3 9% 24% 19% 3	2248
	11th to 20th	Night	38% 3 9% 26% 22% 4	2280
	21st to end	Night	38% 3 8% 27% 19% 5%	2540
November	1st to 10th	Night	38% 4 9% 26% 18% 5%	2431
	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	19% 8% 27% 36% 8% 2	460
	21st to end	Day	20% 8% 27% 35% 9% 1	506
April	1st to 10th	Day	17% 9% 28% 33% 11% 2	460
	11th to 20th	Day	13% 4 23% 38% 20% 2	452
	21st to end	Day	18% 4 22% 37% 17% 2	460
May	1st to 10th	Day	19% 4 20% 36% 20% 3	463
	11th to 20th	Day	21% 2 15% 38% 20% 4	487
	21st to end	Day	17% 2 9% 30% 32% 10%	529
June	1st to 10th	Day	14% 2 11% 32% 33% 8%	490
	11th to 20th	Day	11% 1 10% 32% 36% 10%	490
	21st to end	Day	9% 1 9% 35% 38% 8%	490
July	1st to 10th	Day	11% 3 5% 28% 40% 14%	485
	11th to 20th	Day	6% 1 4 25% 52% 12%	484
	21st to end	Day	8% 3 6% 31% 40% 11%	532
August	1st to 10th	Day	11% 2 6% 30% 40% 12%	486
	11th to 20th	Day	9% 2 4 27% 45% 13%	479
	21st to end	Day	8% 2 8% 28% 37% 17%	539
September	1st to 10th	Day	15% 1 10% 27% 30% 17%	490
	11th to 20th	Day	12% 2 7% 34% 34% 11%	490
	21st to end	Day	24% 2 16% 31% 23% 4	490
October	1st to 10th	Day	21% 1 14% 27% 27% 10%	490
	11th to 20th	Day	16% 6% 19% 31% 23% 5%	490
	21st to end	Day	13% 8% 24% 28% 20% 6%	522
November	1st to 10th	Day	17% 6% 25% 26% 20% 5%	369
	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	20% 7% 32% 30% 8% 3	760
	21st to end	Night	20% 8% 28% 36% 8% 1	836
April	1st to 10th	Night	22% 7% 32% 30% 8% 1	760
	11th to 20th	Night	14% 5% 26% 38% 15% 1	751
	21st to end	Night	19% 3 22% 39% 14% 2	760
May	1st to 10th	Night	19% 4 22% 39% 13% 2	693
	11th to 20th	Night	20% 3 18% 39% 18% 2	445
	21st to end	Night	17% 3 9% 34% 29% 8%	411
June	1st to 10th	Night	18% 3 11% 36% 31% 2	380
	11th to 20th	Night	11% 3 8% 39% 33% 6%	380
	21st to end	Night	8% 3 9% 43% 36% 3	380
July	1st to 10th	Night	8% 4 6% 34% 38% 9%	370
	11th to 20th	Night	7% 2 4 27% 49% 11%	368
	21st to end	Night	8% 2 7% 34% 43% 6%	536
August	1st to 10th	Night	10% 2 5% 36% 42% 6%	605
	11th to 20th	Night	10% 1 7% 31% 42% 8%	750
	21st to end	Night	11% 2 6% 32% 39% 11%	836
September	1st to 10th	Night	15% 1 9% 28% 37% 10%	760
	11th to 20th	Night	13% 3 9% 29% 38% 8%	760
	21st to end	Night	22% 4 14% 29% 25% 5%	760
October	1st to 10th	Night	19% 5% 16% 28% 23% 9%	760
	11th to 20th	Night	19% 6% 21% 31% 21% 2	760
	21st to end	Night	17% 7% 26% 29% 17% 4	836
November	1st to 10th	Night	18% 8% 23% 31% 16% 4	748
	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 2024-10-30 13:19:22. Version ac07

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