Chesapeake Beach Veterans Memorial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chesapeake Beach Veterans Memorial Park clear sky chart from 2005-11-06 to 2025-05-11.

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 5% 4 4 4 4 6% 8% 44%	113833
	Night	14% 6% 2 6% 4 4 4 3 5% 7% 45%	115136
Transparency	Day	23% 42% 7% 15% 10% 3	117468
	Night	23% 40% 6% 15% 12% 3	119640
Seeing	Day	18% 13% 29% 25% 12% 3	15660
	Night	17% 13% 30% 27% 12% 1	25260

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	14% 3 2 5% 2 4 4 3 5% 6% 52%	3620
	11th to 20th	Day	13% 8% 3 6% 4 4 4 3 3 4 48%	4060
	21st to end	Day	15% 5% 2 6% 4 4 4 3 5% 6% 45%	4466
February	1st to 10th	Day	15% 7% 3 6% 4 5% 4 4 7% 7% 39%	1800
	11th to 20th	Day	19% 7% 2 4 3 3 3 3 5% 7% 42%	1857
	21st to end	Day	16% 9% 2 5% 5% 3 4 3 5% 6% 41%	1650
March	1st to 10th	Day	19% 5% 1 4 3 4 4 3 5% 8% 44%	4747
	11th to 20th	Day	11% 7% 2 4 3 3 3 3 4 7% 52%	4980
	21st to end	Day	17% 6% 2 6% 5% 4 4 3 5% 6% 42%	5638
April	1st to 10th	Day	13% 7% 2 4 4 5% 4 3 7% 8% 43%	2400
	11th to 20th	Day	12% 5% 2 5% 4 4 5% 3 5% 6% 48%	2374
	21st to end	Day	16% 6% 2 4 3 4 5% 4 5% 7% 44%	2400
May	1st to 10th	Day	23% 7% 3 6% 4 4 4 4 7% 9% 31%	4035
	11th to 20th	Day	21% 6% 2 5% 4 4 4 4 6% 8% 35%	4356
	21st to end	Day	10% 4 1 5% 4 4 4 4 7% 10% 47%	4823
June	1st to 10th	Day	10% 4 1 5% 4 4 5% 4 7% 10% 45%	2660
	11th to 20th	Day	10% 4 2 5% 3 5% 5% 4 7% 10% 44%	2660
	21st to end	Day	9% 3 1 4 4 4 6% 6% 7% 11% 45%	2660
July	1st to 10th	Day	5% 4 2 5% 4 5% 6% 6% 8% 11% 44%	4440
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 5% 8% 11% 40%	4383
	21st to end	Day	8% 6% 2 8% 5% 5% 6% 5% 8% 9% 37%	4466
August	1st to 10th	Day	15% 6% 2 6% 4 5% 5% 5% 8% 12% 34%	4104
	11th to 20th	Day	9% 5% 2 6% 4 5% 6% 4 7% 9% 42%	3795
	21st to end	Day	8% 4 2 5% 3 3 4 4 6% 10% 49%	4180
September	1st to 10th	Day	13% 4 2 5% 4 4 4 4 5% 8% 47%	2280
	11th to 20th	Day	12% 6% 2 4 4 4 3 3 5% 8% 49%	2280
	21st to end	Day	20% 8% 3 5% 3 4 4 3 6% 6% 38%	2024
October	1st to 10th	Day	17% 4 2 4 3 3 4 3 5% 7% 48%	1900
	11th to 20th	Day	18% 3 1 3 2 3 4 2 5% 7% 52%	1900
	21st to end	Day	13% 5% 1 6% 3 3 4 3 4 7% 50%	2090
November	1st to 10th	Day	13% 4 1 3 4 3 4 3 4 7% 53%	1815
	11th to 20th	Day	14% 6% 2 3 3 3 4 3 5% 7% 50%	1800
	21st to end	Day	13% 6% 1 5% 4 3 4 3 4 7% 50%	1640
December	1st to 10th	Day	11% 4 2 6% 4 3 3 4 5% 7% 51%	2600
	11th to 20th	Day	18% 8% 2 5% 3 3 3 3 4 6% 46%	2990
	21st to end	Day	13% 7% 2 6% 3 4 4 4 5% 7% 43%	3960
January	1st to 10th	Night	12% 7% 2 5% 3 3 4 3 4 6% 50%	6321
	11th to 20th	Night	13% 7% 2 5% 3 3 2 3 4 5% 53%	5900
	21st to end	Night	14% 8% 3 6% 4 3 3 3 4 5% 47%	6490
February	1st to 10th	Night	16% 7% 2 6% 4 4 4 4 5% 6% 42%	2600
	11th to 20th	Night	19% 7% 2 6% 3 3 3 3 5% 6% 44%	2429
	21st to end	Night	17% 8% 2 5% 3 3 3 3 5% 6% 44%	1980
March	1st to 10th	Night	15% 6% 2 6% 4 3 3 3 4 5% 49%	5103
	11th to 20th	Night	11% 7% 2 4 3 3 3 4 5% 7% 51%	4980
	21st to end	Night	14% 7% 2 7% 4 4 4 3 4 6% 45%	5294
April	1st to 10th	Night	17% 7% 1 5% 5% 4 4 4 6% 6% 41%	2000
	11th to 20th	Night	13% 5% 2 6% 4 3 4 4 5% 7% 47%	1975
	21st to end	Night	17% 5% 2 5% 3 3 4 4 6% 7% 44%	2000
May	1st to 10th	Night	20% 8% 3 7% 5% 4 4 4 5% 7% 32%	3109
	11th to 20th	Night	24% 7% 2 6% 4 4 4 3 5% 7% 31%	2543
	21st to end	Night	11% 5% 2 5% 5% 4 5% 3 6% 10% 44%	2732
June	1st to 10th	Night	11% 4 2 6% 5% 4 4 4 6% 10% 43%	1520
	11th to 20th	Night	11% 6% 2 6% 4 5% 4 4 6% 11% 41%	1520
	21st to end	Night	9% 5% 2 5% 5% 4 6% 4 7% 12% 40%	1520
July	1st to 10th	Night	6% 6% 2 6% 6% 5% 6% 6% 8% 11% 39%	2520
	11th to 20th	Night	9% 6% 2 7% 5% 5% 6% 5% 7% 11% 38%	2574
	21st to end	Night	10% 8% 3 9% 6% 5% 6% 5% 6% 7% 36%	3087
August	1st to 10th	Night	15% 5% 3 8% 5% 5% 6% 4 7% 11% 33%	2825
	11th to 20th	Night	11% 6% 3 8% 6% 6% 6% 5% 7% 9% 34%	3001
	21st to end	Night	10% 5% 2 6% 3 3 4 4 6% 8% 50%	3476
September	1st to 10th	Night	14% 5% 2 6% 5% 3 4 3 6% 6% 45%	1900
	11th to 20th	Night	11% 5% 1 5% 4 4 4 3 6% 8% 48%	1900
	21st to end	Night	21% 8% 2 6% 4 3 4 3 6% 6% 37%	2152
October	1st to 10th	Night	18% 5% 2 5% 3 3 4 4 5% 6% 45%	2280
	11th to 20th	Night	16% 5% 2 4 3 3 3 3 3 6% 52%	2280
	21st to end	Night	15% 4 2 5% 3 4 4 3 5% 6% 50%	2508
November	1st to 10th	Night	12% 6% 2 5% 3 3 4 3 4 6% 53%	2481
	11th to 20th	Night	17% 6% 2 4 3 3 4 2 4 6% 48%	2600
	21st to end	Night	12% 5% 2 4 4 3 4 4 6% 6% 50%	2755
December	1st to 10th	Night	10% 5% 2 5% 3 3 4 3 5% 7% 53%	4580
	11th to 20th	Night	19% 6% 2 6% 4 4 5% 3 5% 6% 40%	5205
	21st to end	Night	15% 7% 2 6% 4 4 4 4 6% 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	25% 26% 3 20% 20% 5%	3621
	11th to 20th	Day	29% 27% 4 16% 17% 7%	4060
	21st to end	Day	30% 29% 8% 20% 10% 2	4466
February	1st to 10th	Day	18% 63% 6% 9% 4	1800
	11th to 20th	Day	18% 61% 4 9% 7% 2	1866
	21st to end	Day	18% 62% 5% 8% 7% 1	1650
March	1st to 10th	Day	32% 30% 5% 14% 12% 7%	4747
	11th to 20th	Day	22% 29% 7% 20% 17% 4	4980
	21st to end	Day	31% 29% 6% 13% 14% 6%	5638
April	1st to 10th	Day	17% 63% 4 7% 7% 1	2400
	11th to 20th	Day	14% 64% 4 9% 7% 2	2374
	21st to end	Day	15% 63% 4 11% 6% 1	2400
May	1st to 10th	Day	35% 43% 6% 12% 4 1	4070
	11th to 20th	Day	30% 43% 10% 14% 3	4360
	21st to end	Day	17% 44% 9% 16% 12% 2	4837
June	1st to 10th	Day	13% 67% 4 10% 5% 1	2660
	11th to 20th	Day	10% 67% 5% 9% 8% 1	2660
	21st to end	Day	10% 66% 7% 10% 7% 1	2660
July	1st to 10th	Day	21% 38% 19% 11% 7% 4	4370
	11th to 20th	Day	27% 37% 13% 18% 4 1	4308
	21st to end	Day	30% 37% 8% 14% 11% 1	4324
August	1st to 10th	Day	31% 38% 12% 16% 3	4091
	11th to 20th	Day	25% 37% 8% 22% 7% 1	3833
	21st to end	Day	18% 37% 10% 21% 13% 1	4180
September	1st to 10th	Day	15% 62% 6% 10% 6% 2	2280
	11th to 20th	Day	15% 61% 5% 10% 8% 2	2280
	21st to end	Day	23% 60% 3 10% 3 1	2024
October	1st to 10th	Day	24% 36% 4 11% 21% 4	3160
	11th to 20th	Day	13% 36% 3 19% 20% 9%	3140
	21st to end	Day	8% 36% 7% 21% 18% 9%	3428
November	1st to 10th	Day	17% 57% 6% 10% 8% 3	1815
	11th to 20th	Day	14% 56% 4 12% 12% 2	1800
	21st to end	Day	15% 57% 3 15% 9% 1	1640
December	1st to 10th	Day	23% 36% 8% 17% 13% 4	2600
	11th to 20th	Day	29% 31% 9% 20% 9% 2	2986
	21st to end	Day	29% 30% 10% 18% 12% 1	3960
January	1st to 10th	Night	27% 27% 4 17% 21% 5%	6321
	11th to 20th	Night	24% 26% 4 21% 19% 6%	5900
	21st to end	Night	30% 28% 5% 20% 14% 2	6490
February	1st to 10th	Night	17% 63% 6% 9% 4 1	2600
	11th to 20th	Night	18% 60% 3 8% 10% 2	2431
	21st to end	Night	16% 61% 4 10% 6% 3	1980
March	1st to 10th	Night	30% 29% 4 16% 12% 8%	5103
	11th to 20th	Night	21% 30% 8% 19% 16% 6%	4980
	21st to end	Night	30% 29% 5% 15% 16% 5%	5294
April	1st to 10th	Night	18% 62% 3 8% 8% 1	2000
	11th to 20th	Night	15% 62% 4 10% 6% 2	1975
	21st to end	Night	16% 63% 4 8% 8% 1	2000
May	1st to 10th	Night	35% 42% 6% 11% 5% 1	3139
	11th to 20th	Night	33% 44% 7% 13% 2	2544
	21st to end	Night	19% 44% 10% 15% 10% 2	2739
June	1st to 10th	Night	14% 66% 4 8% 7%	1520
	11th to 20th	Night	13% 66% 5% 9% 6% 1	1520
	21st to end	Night	12% 65% 5% 10% 7% 1	1520
July	1st to 10th	Night	25% 40% 17% 10% 7% 1	2480
	11th to 20th	Night	28% 36% 15% 16% 4	2526
	21st to end	Night	34% 36% 9% 13% 8%	2988
August	1st to 10th	Night	34% 38% 11% 13% 4	2814
	11th to 20th	Night	29% 38% 8% 18% 7%	3029
	21st to end	Night	18% 37% 5% 21% 18%	3476
September	1st to 10th	Night	15% 62% 6% 11% 5% 2	1900
	11th to 20th	Night	14% 60% 5% 11% 9% 2	1900
	21st to end	Night	23% 61% 4 8% 4	2152
October	1st to 10th	Night	28% 36% 7% 12% 13% 5%	3800
	11th to 20th	Night	11% 36% 7% 12% 27% 7%	3779
	21st to end	Night	9% 36% 6% 23% 17% 8%	4120
November	1st to 10th	Night	17% 57% 4 11% 8% 3	2481
	11th to 20th	Night	16% 56% 3 10% 11% 4	2600
	21st to end	Night	13% 57% 5% 13% 10% 1	2755
December	1st to 10th	Night	20% 35% 8% 19% 15% 3	4580
	11th to 20th	Night	33% 31% 8% 14% 10% 4	5208
	21st to end	Night	30% 30% 10% 18% 12%	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	28% 20% 34% 13% 4	205
	11th to 20th	Day	25% 26% 34% 14% 1	300
	21st to end	Day	21% 22% 40% 15% 1 1	330
February	1st to 10th	Day	22% 22% 40% 11% 4	300
	11th to 20th	Day	31% 24% 34% 10% 1	404
	21st to end	Day	26% 22% 35% 15% 2	414
March	1st to 10th	Day	22% 23% 37% 16% 3 1	500
	11th to 20th	Day	22% 22% 36% 14% 6% 1	500
	21st to end	Day	21% 22% 37% 17% 3 1	550
April	1st to 10th	Day	20% 21% 39% 16% 5%	500
	11th to 20th	Day	15% 20% 33% 24% 6% 2	492
	21st to end	Day	20% 17% 34% 22% 7%	500
May	1st to 10th	Day	24% 15% 32% 20% 9%	503
	11th to 20th	Day	22% 10% 34% 25% 9% 1	487
	21st to end	Day	18% 5% 24% 31% 18% 4	529
June	1st to 10th	Day	11% 6% 29% 29% 21% 4	490
	11th to 20th	Day	11% 7% 28% 33% 17% 4	490
	21st to end	Day	9% 5% 29% 37% 16% 4	490
July	1st to 10th	Day	10% 3 19% 36% 25% 7%	485
	11th to 20th	Day	5% 1 15% 44% 28% 8%	484
	21st to end	Day	12% 3 20% 37% 23% 6%	532
August	1st to 10th	Day	14% 4 21% 32% 23% 7%	486
	11th to 20th	Day	13% 3 17% 38% 21% 9%	479
	21st to end	Day	9% 4 21% 34% 23% 10%	539
September	1st to 10th	Day	15% 5% 20% 29% 19% 12%	490
	11th to 20th	Day	15% 5% 21% 30% 21% 7%	490
	21st to end	Day	28% 9% 23% 27% 11% 2	490
October	1st to 10th	Day	20% 9% 23% 25% 18% 4	490
	11th to 20th	Day	18% 14% 25% 28% 14% 2	490
	21st to end	Day	14% 13% 35% 27% 8% 3	539
November	1st to 10th	Day	17% 13% 30% 25% 11% 4	422
	11th to 20th	Day	19% 17% 36% 20% 9% 1	400
	21st to end	Day	21% 22% 29% 19% 9%	240
December	1st to 10th	Day	21% 19% 43% 14% 4 1	200
	11th to 20th	Day	25% 18% 33% 19% 6%	200
	21st to end	Day	22% 16% 33% 24% 5%	220
January	1st to 10th	Night	20% 25% 35% 17% 4	800
	11th to 20th	Night	22% 18% 34% 21% 5%	800
	21st to end	Night	19% 22% 37% 20% 2	880
February	1st to 10th	Night	19% 18% 37% 23% 3	800
	11th to 20th	Night	24% 25% 35% 14% 1	783
	21st to end	Night	22% 21% 36% 18% 2	660
March	1st to 10th	Night	19% 20% 37% 22% 3	800
	11th to 20th	Night	22% 17% 36% 19% 6% 1	800
	21st to end	Night	20% 16% 41% 19% 4	880
April	1st to 10th	Night	20% 21% 36% 19% 3	800
	11th to 20th	Night	16% 13% 36% 28% 7%	791
	21st to end	Night	21% 11% 32% 27% 8%	800
May	1st to 10th	Night	19% 8% 36% 27% 9% 1	731
	11th to 20th	Night	17% 8% 32% 33% 10%	405
	21st to end	Night	13% 4 24% 37% 20% 2	411
June	1st to 10th	Night	12% 3 26% 39% 19% 2	380
	11th to 20th	Night	11% 6% 19% 47% 16% 1	380
	21st to end	Night	10% 3 24% 46% 15% 2	380
July	1st to 10th	Night	9% 4 18% 39% 27% 3	370
	11th to 20th	Night	7% 1 14% 44% 31% 3	396
	21st to end	Night	9% 2 21% 40% 25% 4	624
August	1st to 10th	Night	10% 2 15% 44% 27% 3	567
	11th to 20th	Night	11% 3 18% 39% 27% 2	690
	21st to end	Night	12% 3 17% 33% 30% 5%	836
September	1st to 10th	Night	16% 3 19% 33% 25% 4	760
	11th to 20th	Night	12% 4 17% 37% 26% 4	760
	21st to end	Night	25% 6% 23% 28% 18% 1	760
October	1st to 10th	Night	20% 8% 20% 31% 17% 5%	760
	11th to 20th	Night	17% 13% 27% 27% 16% 1	760
	21st to end	Night	18% 12% 30% 26% 13% 1	836
November	1st to 10th	Night	14% 12% 34% 25% 12% 2	780
	11th to 20th	Night	19% 19% 31% 23% 8% 1	800
	21st to end	Night	16% 19% 31% 25% 9% 1	800
December	1st to 10th	Night	21% 19% 32% 19% 8% 1	800
	11th to 20th	Night	19% 16% 39% 21% 6%	800
	21st to end	Night	19% 17% 32% 29% 4	880

Page generated at 2025-05-08 09:34:00. Version ac07

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