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 2026-09-14.

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	13% 6% 2 6% 4 4 4 4 6% 8% 43%	148918
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 43%	142179
Transparency	Day	28% 33% 8% 17% 12% 2	152510
	Night	28% 33% 8% 16% 12% 3	146658
Seeing	Day	18% 13% 29% 25% 12% 3	17472
	Night	18% 13% 30% 27% 12% 1	26894

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% 4 2 6% 3 4 5% 3 5% 6% 48%	4698
	11th to 20th	Day	14% 8% 3 6% 3 3 3 2 3 4 51%	5280
	21st to end	Day	13% 5% 2 6% 4 4 4 3 5% 6% 47%	5780
February	1st to 10th	Day	14% 6% 3 6% 4 5% 4 4 7% 7% 40%	1890
	11th to 20th	Day	19% 7% 2 5% 3 3 3 3 5% 7% 42%	1952
	21st to end	Day	16% 9% 2 6% 5% 3 4 4 5% 6% 41%	1730
March	1st to 10th	Day	19% 5% 1 4 3 4 4 3 5% 8% 44%	4853
	11th to 20th	Day	11% 7% 2 4 3 3 3 3 5% 7% 51%	5090
	21st to end	Day	16% 6% 2 6% 5% 4 4 3 5% 6% 43%	5762
April	1st to 10th	Day	13% 7% 2 4 4 4 4 3 7% 8% 44%	2520
	11th to 20th	Day	12% 5% 1 5% 4 4 5% 3 6% 7% 48%	2494
	21st to end	Day	16% 6% 2 4 3 4 4 4 5% 7% 44%	2520
May	1st to 10th	Day	18% 6% 3 6% 4 4 4 4 6% 9% 37%	7277
	11th to 20th	Day	17% 5% 2 5% 4 4 4 4 6% 9% 41%	8139
	21st to end	Day	21% 6% 2 6% 4 4 4 3 5% 7% 39%	9045
June	1st to 10th	Day	9% 5% 2 5% 4 4 5% 4 7% 10% 45%	2940
	11th to 20th	Day	10% 4 2 5% 4 5% 5% 4 7% 10% 45%	2940
	21st to end	Day	9% 3 1 4 4 4 5% 5% 7% 11% 46%	2940
July	1st to 10th	Day	8% 5% 2 6% 4 4 5% 5% 7% 10% 44%	8280
	11th to 20th	Day	8% 6% 3 7% 5% 5% 6% 6% 9% 12% 33%	8167
	21st to end	Day	7% 5% 2 7% 5% 5% 5% 5% 7% 10% 41%	8340
August	1st to 10th	Day	12% 6% 2 7% 5% 6% 6% 6% 8% 12% 31%	6014
	11th to 20th	Day	9% 5% 2 7% 5% 5% 6% 5% 7% 10% 39%	5583
	21st to end	Day	8% 4 1 5% 4 4 5% 5% 7% 10% 46%	6080
September	1st to 10th	Day	13% 4 2 5% 4 3 4 4 5% 8% 48%	2520
	11th to 20th	Day	13% 6% 2 4 4 4 3 3 5% 8% 48%	2436
	21st to end	Day	20% 9% 2 5% 3 4 4 3 6% 6% 38%	2130
October	1st to 10th	Day	17% 4 2 4 3 3 4 3 5% 7% 49%	2000
	11th to 20th	Day	18% 3 1 3 2 3 3 2 4 6% 52%	2000
	21st to end	Day	13% 5% 2 6% 3 3 4 3 4 7% 50%	2200
November	1st to 10th	Day	13% 5% 1 3 4 3 4 3 4 7% 53%	1908
	11th to 20th	Day	14% 6% 2 4 3 3 4 3 5% 7% 50%	1890
	21st to end	Day	14% 6% 1 5% 4 3 4 3 4 7% 50%	1722
December	1st to 10th	Day	11% 5% 2 6% 4 3 3 4 5% 7% 50%	2680
	11th to 20th	Day	17% 8% 2 5% 3 3 3 3 4 6% 46%	3070
	21st to end	Day	13% 7% 2 6% 3 4 4 4 5% 7% 43%	4048
January	1st to 10th	Night	11% 7% 2 6% 4 4 5% 4 6% 7% 46%	8191
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 4 5% 52%	7680
	21st to end	Night	13% 7% 2 6% 4 3 3 3 5% 5% 48%	8401
February	1st to 10th	Night	16% 7% 2 6% 4 4 4 4 5% 6% 43%	2730
	11th to 20th	Night	19% 7% 2 6% 3 3 3 3 5% 6% 44%	2553
	21st to end	Night	16% 8% 3 5% 3 3 3 3 5% 6% 44%	2076
March	1st to 10th	Night	15% 6% 2 6% 4 3 3 3 4 5% 48%	5217
	11th to 20th	Night	11% 7% 2 4 3 3 3 4 5% 7% 51%	5090
	21st to end	Night	14% 7% 2 7% 4 4 4 3 4 6% 45%	5412
April	1st to 10th	Night	16% 8% 2 5% 4 4 4 4 5% 6% 42%	2100
	11th to 20th	Night	12% 5% 2 6% 4 3 4 4 5% 7% 47%	2075
	21st to end	Night	17% 5% 2 5% 3 3 4 4 6% 7% 44%	2100
May	1st to 10th	Night	16% 7% 2 7% 5% 5% 5% 5% 6% 8% 33%	5619
	11th to 20th	Night	19% 6% 2 6% 4 4 4 4 5% 9% 37%	4721
	21st to end	Night	23% 7% 2 6% 5% 4 4 3 5% 7% 34%	5108
June	1st to 10th	Night	10% 4 2 6% 5% 5% 4 4 6% 10% 44%	1680
	11th to 20th	Night	12% 6% 2 6% 4 5% 4 4 6% 10% 40%	1680
	21st to end	Night	9% 5% 2 6% 5% 4 6% 4 7% 12% 40%	1680
July	1st to 10th	Night	11% 6% 2 7% 5% 4 5% 5% 7% 10% 38%	4678
	11th to 20th	Night	10% 7% 3 8% 6% 5% 6% 5% 8% 11% 31%	4773
	21st to end	Night	9% 6% 3 8% 5% 5% 6% 5% 7% 9% 38%	5736
August	1st to 10th	Night	14% 7% 3 9% 6% 5% 6% 4 7% 11% 28%	4135
	11th to 20th	Night	11% 6% 3 9% 6% 6% 6% 5% 7% 9% 33%	4416
	21st to end	Night	10% 5% 2 7% 4 4 5% 4 6% 8% 44%	5045
September	1st to 10th	Night	14% 4 2 6% 4 3 4 3 6% 7% 46%	2100
	11th to 20th	Night	12% 5% 1 6% 4 4 4 3 6% 8% 47%	2031
	21st to end	Night	21% 8% 2 6% 4 3 4 4 6% 6% 36%	2266
October	1st to 10th	Night	18% 5% 2 5% 3 3 4 4 4 6% 46%	2400
	11th to 20th	Night	17% 5% 2 4 3 3 3 3 3 6% 51%	2400
	21st to end	Night	15% 4 2 5% 3 4 4 3 5% 6% 49%	2640
November	1st to 10th	Night	12% 5% 2 5% 3 3 4 3 4 6% 53%	2608
	11th to 20th	Night	16% 7% 2 4 3 3 4 2 4 5% 48%	2730
	21st to end	Night	12% 5% 2 4 4 3 4 4 6% 6% 49%	2893
December	1st to 10th	Night	10% 5% 2 5% 3 3 4 3 5% 7% 53%	4720
	11th to 20th	Night	19% 6% 2 6% 4 4 5% 3 5% 6% 40%	5345
	21st to end	Night	15% 7% 2 6% 4 4 4 4 6% 7% 42%	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	31% 21% 5% 21% 18% 4	4699
	11th to 20th	Day	30% 21% 3 16% 22% 8%	5280
	21st to end	Day	31% 23% 7% 27% 11% 2	5780
February	1st to 10th	Day	18% 60% 6% 10% 5% 1	1890
	11th to 20th	Day	20% 58% 4 9% 7% 2	1961
	21st to end	Day	19% 59% 5% 9% 7% 1	1730
March	1st to 10th	Day	32% 29% 5% 14% 12% 7%	4853
	11th to 20th	Day	23% 29% 7% 20% 17% 4	5090
	21st to end	Day	31% 29% 7% 14% 14% 6%	5762
April	1st to 10th	Day	18% 60% 5% 8% 8% 1	2520
	11th to 20th	Day	15% 61% 5% 11% 7% 2	2494
	21st to end	Day	17% 60% 5% 12% 6% 1	2520
May	1st to 10th	Day	37% 24% 9% 16% 12% 1	7309
	11th to 20th	Day	33% 24% 9% 22% 12%	8143
	21st to end	Day	38% 24% 7% 15% 14% 2	9061
June	1st to 10th	Day	15% 61% 4 11% 8% 1	2940
	11th to 20th	Day	13% 60% 6% 10% 9% 1	2940
	21st to end	Day	13% 60% 7% 11% 9% 1	2940
July	1st to 10th	Day	30% 22% 18% 17% 10% 2	8210
	11th to 20th	Day	37% 22% 14% 20% 6%	8092
	21st to end	Day	34% 20% 9% 20% 17% 1	8156
August	1st to 10th	Day	36% 28% 17% 16% 3	6001
	11th to 20th	Day	32% 27% 13% 21% 7%	5621
	21st to end	Day	25% 26% 13% 22% 14%	6080
September	1st to 10th	Day	16% 56% 7% 13% 7% 2	2520
	11th to 20th	Day	17% 57% 5% 10% 8% 2	2436
	21st to end	Day	25% 57% 4 10% 3 1	2130
October	1st to 10th	Day	24% 35% 4 12% 21% 4	3260
	11th to 20th	Day	14% 35% 3 19% 20% 9%	3240
	21st to end	Day	9% 35% 7% 20% 19% 10%	3538
November	1st to 10th	Day	17% 54% 6% 12% 9% 3	1908
	11th to 20th	Day	15% 54% 4 13% 13% 2	1890
	21st to end	Day	17% 54% 3 16% 9% 1	1722
December	1st to 10th	Day	24% 35% 9% 17% 12% 4	2680
	11th to 20th	Day	29% 30% 9% 21% 9% 2	3066
	21st to end	Day	29% 30% 10% 18% 12% 1	4048
January	1st to 10th	Night	31% 21% 8% 19% 17% 3	8192
	11th to 20th	Night	28% 20% 4 20% 20% 8%	7680
	21st to end	Night	32% 22% 5% 23% 16% 3	8401
February	1st to 10th	Night	18% 60% 5% 10% 5% 1	2730
	11th to 20th	Night	19% 57% 3 8% 10% 2	2555
	21st to end	Night	18% 58% 4 11% 6% 3	2076
March	1st to 10th	Night	31% 29% 5% 16% 12% 8%	5217
	11th to 20th	Night	21% 29% 8% 20% 16% 6%	5090
	21st to end	Night	30% 28% 5% 16% 16% 5%	5412
April	1st to 10th	Night	19% 59% 4 9% 8% 1	2100
	11th to 20th	Night	16% 59% 5% 11% 7% 2	2075
	21st to end	Night	17% 60% 4 10% 8% 1	2100
May	1st to 10th	Night	39% 24% 10% 17% 9% 1	5649
	11th to 20th	Night	35% 24% 10% 20% 10%	4722
	21st to end	Night	42% 24% 8% 13% 12% 1	5115
June	1st to 10th	Night	17% 60% 4 9% 10%	1680
	11th to 20th	Night	16% 60% 6% 11% 6% 1	1680
	21st to end	Night	15% 59% 6% 11% 9% 1	1680
July	1st to 10th	Night	35% 24% 13% 17% 10% 1	4640
	11th to 20th	Night	41% 22% 15% 16% 6%	4728
	21st to end	Night	36% 20% 12% 18% 13%	5606
August	1st to 10th	Night	42% 28% 14% 12% 4	4124
	11th to 20th	Night	35% 27% 13% 18% 8%	4444
	21st to end	Night	29% 26% 8% 21% 16%	5045
September	1st to 10th	Night	17% 56% 6% 14% 5% 2	2100
	11th to 20th	Night	16% 57% 5% 12% 9% 2	2031
	21st to end	Night	25% 58% 5% 8% 4	2266
October	1st to 10th	Night	28% 35% 7% 12% 14% 5%	3920
	11th to 20th	Night	12% 35% 7% 13% 27% 7%	3899
	21st to end	Night	10% 35% 6% 23% 18% 8%	4252
November	1st to 10th	Night	18% 54% 4 11% 9% 3	2608
	11th to 20th	Night	17% 53% 3 10% 12% 4	2730
	21st to end	Night	15% 54% 6% 14% 11% 1	2893
December	1st to 10th	Night	21% 34% 9% 19% 15% 3	4720
	11th to 20th	Night	33% 31% 8% 14% 11% 4	5348
	21st to end	Night	30% 29% 10% 18% 12% 1	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	27% 20% 34% 14% 4	226
	11th to 20th	Day	26% 28% 32% 13% 1	330
	21st to end	Day	21% 25% 39% 14% 1 1	363
February	1st to 10th	Day	23% 23% 39% 12% 3	330
	11th to 20th	Day	31% 24% 34% 10% 1	439
	21st to end	Day	26% 22% 35% 15% 2	446
March	1st to 10th	Day	23% 22% 36% 16% 3 1	540
	11th to 20th	Day	23% 22% 35% 14% 5% 1	540
	21st to end	Day	21% 22% 37% 16% 2 1	594
April	1st to 10th	Day	20% 20% 38% 16% 5%	540
	11th to 20th	Day	15% 20% 34% 23% 6% 2	532
	21st to end	Day	21% 16% 33% 22% 7%	540
May	1st to 10th	Day	23% 16% 33% 19% 8%	543
	11th to 20th	Day	23% 10% 34% 23% 9% 1	567
	21st to end	Day	21% 7% 24% 29% 16% 3	617
June	1st to 10th	Day	11% 8% 30% 29% 19% 4	570
	11th to 20th	Day	13% 8% 29% 32% 15% 4	570
	21st to end	Day	11% 5% 28% 36% 15% 4	570
July	1st to 10th	Day	11% 3 19% 36% 24% 7%	565
	11th to 20th	Day	6% 1 16% 44% 26% 7%	564
	21st to end	Day	12% 3 21% 36% 22% 6%	620
August	1st to 10th	Day	15% 4 22% 33% 21% 6%	566
	11th to 20th	Day	13% 3 18% 39% 19% 8%	559
	21st to end	Day	9% 4 25% 33% 21% 9%	627
September	1st to 10th	Day	14% 5% 23% 30% 17% 11%	570
	11th to 20th	Day	17% 5% 21% 30% 20% 7%	542
	21st to end	Day	28% 8% 24% 27% 11% 2	530
October	1st to 10th	Day	18% 9% 24% 25% 18% 5%	530
	11th to 20th	Day	20% 14% 25% 26% 13% 2	530
	21st to end	Day	15% 15% 34% 26% 7% 3	583
November	1st to 10th	Day	18% 13% 31% 24% 10% 3	455
	11th to 20th	Day	20% 17% 34% 20% 8% 1	430
	21st to end	Day	23% 21% 28% 19% 8%	262
December	1st to 10th	Day	22% 18% 43% 13% 4	220
	11th to 20th	Day	25% 19% 33% 18% 5%	220
	21st to end	Day	24% 18% 32% 23% 4	242
January	1st to 10th	Night	19% 24% 36% 17% 4	840
	11th to 20th	Night	23% 18% 34% 20% 5%	840
	21st to end	Night	20% 21% 37% 20% 2	924
February	1st to 10th	Night	19% 18% 37% 23% 3	840
	11th to 20th	Night	24% 25% 35% 14% 1	823
	21st to end	Night	22% 21% 36% 19% 2	692
March	1st to 10th	Night	19% 20% 37% 22% 3	840
	11th to 20th	Night	22% 17% 36% 18% 6% 1	840
	21st to end	Night	20% 17% 41% 19% 4	924
April	1st to 10th	Night	20% 21% 36% 20% 3	840
	11th to 20th	Night	15% 13% 37% 28% 6%	831
	21st to end	Night	21% 11% 33% 26% 8%	840
May	1st to 10th	Night	19% 10% 36% 26% 9% 1	768
	11th to 20th	Night	17% 8% 33% 32% 10%	446
	21st to end	Night	16% 5% 24% 34% 18% 2	455
June	1st to 10th	Night	11% 3 27% 39% 18% 1	420
	11th to 20th	Night	12% 8% 19% 45% 15% 1	420
	21st to end	Night	10% 3 24% 46% 15% 2	420
July	1st to 10th	Night	10% 4 18% 41% 26% 3	410
	11th to 20th	Night	7% 1 15% 44% 30% 3	439
	21st to end	Night	9% 2 21% 40% 25% 3	690
August	1st to 10th	Night	10% 2 16% 43% 26% 3	627
	11th to 20th	Night	11% 3 18% 39% 26% 2	764
	21st to end	Night	13% 3 19% 33% 28% 5%	924
September	1st to 10th	Night	15% 3 20% 34% 24% 4	840
	11th to 20th	Night	14% 4 16% 37% 25% 4	813
	21st to end	Night	25% 6% 23% 28% 17% 1	800
October	1st to 10th	Night	20% 8% 20% 30% 17% 5%	800
	11th to 20th	Night	18% 13% 27% 26% 15% 1	800
	21st to end	Night	18% 13% 30% 26% 12% 1	880
November	1st to 10th	Night	15% 13% 34% 25% 11% 2	820
	11th to 20th	Night	20% 19% 31% 23% 8%	840
	21st to end	Night	16% 19% 31% 25% 8% 1	840
December	1st to 10th	Night	20% 20% 32% 19% 8% 1	840
	11th to 20th	Night	20% 16% 38% 20% 5%	840
	21st to end	Night	19% 18% 32% 28% 4	924

Page generated at 2026-09-11 04:11:51. Version ac07

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