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 2025-06-10.

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% 42%	119328
	Night	14% 7% 3 6% 4 4 4 3 5% 7% 43%	118870
Transparency	Day	39% 5% 13% 24% 16% 3	122943
	Night	40% 4 11% 24% 18% 4	123392
Seeing	Day	16% 5% 19% 31% 24% 6%	15924
	Night	17% 7% 23% 31% 18% 3	25346

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	13% 5% 1 4 3 3 3 3 4 7% 54%	3597
	11th to 20th	Day	12% 8% 2 7% 4 4 3 3 4 5% 49%	3858
	21st to end	Day	12% 8% 4 9% 5% 4 5% 3 5% 6% 41%	4466
February	1st to 10th	Day	13% 8% 3 7% 5% 4 5% 4 7% 7% 38%	1814
	11th to 20th	Day	19% 7% 2 4 4 4 4 3 4 6% 42%	1948
	21st to end	Day	16% 10% 3 6% 4 3 4 4 5% 7% 39%	1650
March	1st to 10th	Day	17% 6% 2 5% 4 3 4 3 5% 7% 44%	4479
	11th to 20th	Day	9% 8% 3 6% 3 3 3 3 5% 6% 50%	4980
	21st to end	Day	14% 8% 2 6% 4 3 4 3 6% 6% 44%	5802
April	1st to 10th	Day	15% 7% 2 6% 5% 3 4 3 5% 7% 44%	2400
	11th to 20th	Day	11% 7% 2 5% 4 3 5% 3 5% 7% 48%	2374
	21st to end	Day	14% 7% 2 5% 4 4 4 4 5% 9% 43%	2400
May	1st to 10th	Day	16% 9% 3 8% 6% 5% 5% 4 6% 7% 31%	5579
	11th to 20th	Day	18% 10% 3 8% 5% 4 4 4 5% 8% 31%	6180
	21st to end	Day	15% 6% 3 7% 5% 5% 5% 4 6% 10% 35%	6934
June	1st to 10th	Day	11% 5% 2 5% 4 5% 4 5% 7% 10% 41%	2786
	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	13% 5% 2 5% 4 3 5% 3 6% 7% 46%	1761
	11th to 20th	Day	12% 7% 3 5% 6% 4 4 3 4 7% 46%	1800
	21st to end	Day	15% 6% 2 5% 4 3 3 3 4 6% 49%	1770
December	1st to 10th	Day	10% 5% 2 5% 4 3 4 3 5% 6% 52%	2600
	11th to 20th	Day	17% 9% 3 6% 3 3 2 2 4 6% 45%	2990
	21st to end	Day	11% 6% 2 5% 4 4 4 4 5% 9% 46%	3960
January	1st to 10th	Night	12% 6% 2 4 3 4 3 3 4 6% 52%	6349
	11th to 20th	Night	13% 7% 2 6% 3 3 3 2 3 4 52%	6084
	21st to end	Night	14% 8% 3 6% 4 3 3 3 4 5% 46%	6490
February	1st to 10th	Night	17% 8% 3 6% 3 3 3 3 5% 6% 41%	2585
	11th to 20th	Night	19% 8% 2 5% 4 4 4 3 5% 5% 42%	2338
	21st to end	Night	17% 7% 2 5% 3 4 4 2 5% 6% 45%	1980
March	1st to 10th	Night	18% 7% 2 5% 3 3 3 3 4 5% 46%	5356
	11th to 20th	Night	13% 10% 3 4 3 3 3 3 5% 7% 46%	4980
	21st to end	Night	15% 9% 3 6% 4 3 4 3 5% 5% 43%	5128
April	1st to 10th	Night	17% 8% 3 6% 5% 3 4 4 5% 6% 39%	2000
	11th to 20th	Night	12% 7% 2 6% 4 4 4 3 4 6% 48%	1975
	21st to end	Night	15% 7% 2 5% 4 4 5% 4 6% 7% 41%	2000
May	1st to 10th	Night	14% 10% 4 9% 5% 4 4 4 7% 8% 31%	4315
	11th to 20th	Night	20% 11% 4 7% 4 4 3 3 5% 7% 32%	3741
	21st to end	Night	17% 9% 4 9% 5% 4 4 3 5% 7% 34%	3920
June	1st to 10th	Night	13% 7% 3 7% 4 4 5% 3 6% 9% 40%	1598
	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 4 4 3 5% 6% 48%	2537
	11th to 20th	Night	16% 6% 2 6% 4 4 4 3 5% 5% 46%	2600
	21st to end	Night	12% 6% 2 4 4 3 4 3 5% 6% 51%	2625
December	1st to 10th	Night	10% 6% 2 5% 3 4 3 3 6% 6% 51%	4580
	11th to 20th	Night	19% 8% 3 7% 4 4 4 3 5% 6% 37%	5205
	21st to end	Night	12% 9% 3 6% 4 3 4 4 5% 7% 42%	6996

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	32% 2 5% 29% 28% 4	3598
	11th to 20th	Day	40% 2 8% 21% 23% 6%	3858
	21st to end	Day	46% 3 9% 29% 12% 2	4466
February	1st to 10th	Day	44% 3 13% 25% 12% 2	1814
	11th to 20th	Day	45% 2 9% 24% 16% 4	1957
	21st to end	Day	45% 3 12% 22% 14% 4	1650
March	1st to 10th	Day	41% 3 8% 21% 20% 7%	4479
	11th to 20th	Day	36% 3 10% 27% 19% 6%	4980
	21st to end	Day	42% 4 10% 18% 19% 8%	5802
April	1st to 10th	Day	41% 4 11% 21% 18% 5%	2400
	11th to 20th	Day	36% 3 12% 25% 19% 5%	2374
	21st to end	Day	38% 5% 13% 21% 19% 4	2400
May	1st to 10th	Day	52% 5% 15% 19% 8% 1	5611
	11th to 20th	Day	52% 4 12% 22% 9% 1	6184
	21st to end	Day	44% 6% 14% 22% 13% 1	6949
June	1st to 10th	Day	37% 6% 16% 25% 15% 2	2786
	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	31% 3 10% 28% 22% 5%	3202
	11th to 20th	Day	29% 3 6% 27% 29% 6%	3140
	21st to end	Day	26% 3 11% 30% 22% 9%	3371
November	1st to 10th	Day	38% 4 9% 30% 16% 4	1761
	11th to 20th	Day	40% 4 10% 22% 20% 5%	1800
	21st to end	Day	38% 4 8% 30% 16% 3	1770
December	1st to 10th	Day	35% 3 14% 27% 18% 4	2600
	11th to 20th	Day	44% 2 12% 24% 14% 3	2986
	21st to end	Day	36% 3 18% 26% 17%	3960
January	1st to 10th	Night	35% 2 6% 25% 26% 6%	6349
	11th to 20th	Night	37% 2 7% 26% 23% 5%	6084
	21st to end	Night	42% 2 8% 29% 17% 2	6490
February	1st to 10th	Night	43% 4 12% 25% 15% 2	2585
	11th to 20th	Night	45% 3 8% 22% 19% 4	2340
	21st to end	Night	42% 3 8% 23% 19% 5%	1980
March	1st to 10th	Night	42% 3 8% 23% 16% 8%	5356
	11th to 20th	Night	39% 3 9% 24% 20% 6%	4980
	21st to end	Night	44% 3 9% 19% 19% 6%	5128
April	1st to 10th	Night	46% 3 9% 20% 17% 5%	2000
	11th to 20th	Night	38% 3 11% 21% 21% 6%	1975
	21st to end	Night	41% 4 11% 21% 19% 4	2000
May	1st to 10th	Night	50% 4 15% 21% 9% 2	4345
	11th to 20th	Night	53% 4 11% 20% 11% 1	3742
	21st to end	Night	51% 4 12% 19% 13% 1	3927
June	1st to 10th	Night	43% 5% 11% 24% 16% 2	1598
	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	36% 3 9% 25% 25% 3	3755
	11th to 20th	Night	27% 3 9% 26% 30% 6%	3779
	21st to end	Night	25% 2 10% 31% 24% 8%	4176
November	1st to 10th	Night	38% 4 9% 26% 19% 5%	2537
	11th to 20th	Night	41% 3 10% 22% 19% 5%	2600
	21st to end	Night	35% 3 12% 26% 21% 3	2625
December	1st to 10th	Night	33% 3 14% 25% 21% 3	4580
	11th to 20th	Night	49% 3 11% 20% 13% 3	5208
	21st to end	Night	42% 3 16% 23% 15% 1	6996

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	21% 12% 34% 26% 8% 1	200
	11th to 20th	Day	14% 14% 39% 23% 9%	257
	21st to end	Day	17% 9% 29% 36% 8% 1	330
February	1st to 10th	Day	17% 10% 30% 33% 10%	314
	11th to 20th	Day	27% 9% 38% 22% 5%	496
	21st to end	Day	20% 8% 37% 25% 8% 1	414
March	1st to 10th	Day	18% 11% 31% 31% 9%	500
	11th to 20th	Day	19% 8% 27% 35% 10% 2	500
	21st to end	Day	19% 7% 30% 35% 8% 1	550
April	1st to 10th	Day	17% 9% 28% 33% 11% 2	500
	11th to 20th	Day	14% 4 24% 38% 18% 1	492
	21st to end	Day	18% 3 21% 37% 19% 2	500
May	1st to 10th	Day	18% 4 20% 38% 18% 2	503
	11th to 20th	Day	20% 2 16% 38% 20% 4	527
	21st to end	Day	17% 2 10% 31% 30% 9%	573
June	1st to 10th	Day	14% 2 11% 32% 33% 8%	526
	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	16% 6% 25% 28% 21% 5%	395
	11th to 20th	Day	18% 9% 29% 29% 15% 1	400
	21st to end	Day	19% 12% 25% 25% 16% 3	370
December	1st to 10th	Day	17% 8% 36% 29% 11% 1	200
	11th to 20th	Day	22% 7% 30% 29% 12% 1	200
	21st to end	Day	18% 7% 28% 30% 17%	220
January	1st to 10th	Night	17% 17% 35% 23% 8%	800
	11th to 20th	Night	19% 14% 33% 28% 7%	800
	21st to end	Night	19% 12% 37% 29% 3	880
February	1st to 10th	Night	21% 9% 35% 30% 4	800
	11th to 20th	Night	24% 12% 37% 24% 3	783
	21st to end	Night	20% 12% 30% 32% 6%	660
March	1st to 10th	Night	20% 10% 34% 28% 8%	800
	11th to 20th	Night	21% 8% 31% 30% 8% 2	800
	21st to end	Night	20% 7% 29% 36% 8% 1	880
April	1st to 10th	Night	22% 7% 32% 30% 9% 1	800
	11th to 20th	Night	15% 5% 27% 38% 14% 1	791
	21st to end	Night	19% 3 23% 39% 15% 2	800
May	1st to 10th	Night	19% 4 22% 40% 13% 2	729
	11th to 20th	Night	19% 3 18% 39% 19% 2	469
	21st to end	Night	18% 3 10% 34% 28% 7%	433
June	1st to 10th	Night	17% 4 10% 37% 30% 2	400
	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% 22% 31% 17% 4	780
	11th to 20th	Night	19% 11% 28% 31% 11% 1	800
	21st to end	Night	15% 14% 27% 29% 14% 1	800
December	1st to 10th	Night	21% 11% 34% 23% 10% 2	800
	11th to 20th	Night	19% 10% 37% 26% 7%	800
	21st to end	Night	18% 10% 32% 31% 8%	880

Page generated at 2025-06-07 10:28:20. Version ac07

Copyright © 2025 Attilla Danko.