Fort Meade Recreation Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Meade Recreation Area clear sky chart from 2005-11-06 to 2025-10-04.

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	6% 5% 2 5% 4 4 4 4 6% 8% 51%	135436
	Night	5% 5% 2 6% 4 4 4 4 6% 8% 51%	131360
Transparency	Day	29% 7% 14% 28% 19% 4	130187
	Night	29% 7% 13% 27% 19% 4	127616
Seeing	Day	13% 12% 30% 28% 14% 3	17234
	Night	10% 13% 31% 34% 11% 1	27115

By Month

Percentage Cloud Cover SW (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	1 5% 3 10% 5% 5% 6% 5% 7% 10% 43%	3638
	11th to 20th	Day	1 4 4 8% 7% 5% 5% 3 5% 8% 49%	3640
	21st to end	Day	1 3 2 7% 4 4 5% 4 6% 7% 57%	4004
February	1st to 10th	Day	3 10% 4 7% 5% 7% 5% 5% 7% 8% 39%	1784
	11th to 20th	Day	3 7% 3 11% 5% 4 5% 4 6% 8% 43%	1897
	21st to end	Day	3 6% 3 8% 6% 5% 5% 4 6% 10% 45%	1650
March	1st to 10th	Day	4 8% 3 5% 3 4 4 4 5% 7% 54%	4500
	11th to 20th	Day	6% 6% 2 5% 3 3 3 3 5% 9% 56%	4666
	21st to end	Day	10% 12% 3 7% 4 4 4 3 6% 8% 38%	5969
April	1st to 10th	Day	10% 10% 3 6% 3 3 4 4 6% 8% 44%	2400
	11th to 20th	Day	10% 8% 3 7% 5% 5% 5% 5% 6% 8% 38%	2371
	21st to end	Day	12% 8% 2 6% 5% 5% 4 4 7% 7% 39%	2550
May	1st to 10th	Day	9% 7% 3 6% 5% 4 5% 4 5% 7% 46%	6076
	11th to 20th	Day	12% 9% 2 6% 4 4 4 4 6% 8% 41%	6298
	21st to end	Day	15% 6% 2 5% 4 4 4 4 6% 8% 43%	6925
June	1st to 10th	Day	7% 4 2 4 4 4 5% 6% 7% 9% 48%	2800
	11th to 20th	Day	7% 4 2 4 4 4 5% 5% 7% 10% 48%	2800
	21st to end	Day	3 4 2 3 2 3 4 3 7% 8% 61%	2800
July	1st to 10th	Day	3 3 1 5% 4 4 5% 5% 8% 10% 53%	6339
	11th to 20th	Day	8% 3 1 3 2 3 4 4 6% 7% 59%	6340
	21st to end	Day	5% 3 1 3 3 4 5% 4 7% 9% 55%	6903
August	1st to 10th	Day	4 3 1 5% 3 4 5% 5% 8% 11% 50%	6232
	11th to 20th	Day	4 3 1 4 3 4 4 4 7% 9% 57%	5637
	21st to end	Day	8% 3 1 4 3 3 4 3 5% 7% 58%	5984
September	1st to 10th	Day	6% 4 1 3 3 3 3 3 5% 7% 63%	2400
	11th to 20th	Day	7% 4 1 3 3 3 3 4 5% 6% 61%	2320
	21st to end	Day	8% 4 1 4 3 3 3 3 4 7% 60%	2200
October	1st to 10th	Day	5% 3 1 3 2 2 3 2 3 5% 71%	3337
	11th to 20th	Day	9% 3 1 3 2 2 3 3 4 6% 63%	3090
	21st to end	Day	7% 6% 2 4 2 3 3 4 7% 9% 53%	3091
November	1st to 10th	Day	5% 5% 2 4 3 3 4 5% 6% 8% 56%	1763
	11th to 20th	Day	3 5% 2 5% 4 3 4 4 6% 8% 55%	1782
	21st to end	Day	3 5% 2 5% 5% 4 4 4 6% 9% 53%	1600
December	1st to 10th	Day	1 4 2 7% 5% 5% 6% 6% 6% 8% 50%	2620
	11th to 20th	Day	1 3 2 8% 4 5% 5% 4 6% 10% 52%	3026
	21st to end	Day	5% 7% 3 7% 4 4 5% 3 5% 8% 49%	4004
January	1st to 10th	Night	3 8% 4 8% 6% 5% 5% 5% 6% 6% 44%	6327
	11th to 20th	Night	1 4 3 10% 6% 6% 6% 4 6% 7% 47%	6340
	21st to end	Night	1 3 1 6% 4 4 4 4 6% 8% 59%	6974
February	1st to 10th	Night	4 9% 3 9% 5% 5% 6% 5% 7% 8% 40%	2635
	11th to 20th	Night	2 8% 3 8% 5% 5% 5% 4 7% 8% 43%	2389
	21st to end	Night	3 7% 3 6% 5% 5% 5% 5% 7% 8% 48%	1980
March	1st to 10th	Night	4 7% 3 6% 3 4 4 3 6% 7% 53%	5374
	11th to 20th	Night	5% 6% 2 5% 4 4 4 4 6% 10% 51%	5300
	21st to end	Night	9% 10% 3 8% 5% 5% 6% 4 7% 9% 33%	4984
April	1st to 10th	Night	10% 8% 2 5% 5% 5% 4 5% 6% 8% 44%	2000
	11th to 20th	Night	10% 7% 3 6% 4 4 5% 4 5% 7% 46%	1977
	21st to end	Night	10% 7% 2 5% 4 4 5% 3 6% 7% 45%	1850
May	1st to 10th	Night	8% 6% 2 6% 4 4 4 4 5% 7% 50%	3889
	11th to 20th	Night	11% 6% 2 5% 4 4 4 4 6% 8% 46%	3617
	21st to end	Night	16% 8% 2 6% 4 3 3 3 5% 7% 42%	3972
June	1st to 10th	Night	7% 5% 2 3 4 4 4 4 7% 10% 51%	1600
	11th to 20th	Night	8% 5% 1 4 4 5% 4 4 9% 9% 48%	1600
	21st to end	Night	7% 3 2 4 3 3 4 4 6% 8% 57%	1600
July	1st to 10th	Night	4 3 2 4 3 3 4 4 7% 10% 57%	3640
	11th to 20th	Night	6% 2 1 3 3 3 5% 4 7% 9% 57%	3640
	21st to end	Night	9% 4 2 4 3 3 4 4 7% 9% 51%	3970
August	1st to 10th	Night	6% 4 1 5% 3 4 5% 4 7% 9% 52%	3580
	11th to 20th	Night	4 3 1 4 3 3 4 4 6% 11% 56%	4208
	21st to end	Night	6% 4 2 5% 4 4 4 3 5% 6% 57%	4993
September	1st to 10th	Night	5% 2 1 3 3 3 4 3 5% 7% 63%	2000
	11th to 20th	Night	7% 3 2 4 3 3 4 3 6% 7% 58%	2080
	21st to end	Night	9% 3 1 3 3 3 3 3 4 6% 62%	2200
October	1st to 10th	Night	6% 4 1 3 2 2 2 2 3 5% 71%	3693
	11th to 20th	Night	7% 4 1 4 2 3 3 5% 5% 7% 59%	3806
	21st to end	Night	7% 6% 2 4 3 3 4 3 5% 8% 54%	4467
November	1st to 10th	Night	5% 6% 2 6% 4 4 5% 4 6% 8% 50%	2535
	11th to 20th	Night	3 5% 2 5% 4 4 5% 4 7% 7% 54%	2615
	21st to end	Night	3 5% 2 4 4 4 4 3 7% 8% 55%	2800
December	1st to 10th	Night	2 4 2 6% 5% 4 5% 4 7% 9% 52%	4570
	11th to 20th	Night	2 4 2 6% 6% 5% 6% 4 6% 10% 48%	5181
	21st to end	Night	5% 8% 2 6% 4 4 5% 4 6% 8% 47%	6974

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	33% 10% 19% 26% 12% 1	3639
	11th to 20th	Day	31% 9% 16% 26% 15% 4	3640
	21st to end	Day	22% 9% 17% 34% 15% 3	4004
February	1st to 10th	Day	40% 9% 14% 21% 14% 2	1784
	11th to 20th	Day	38% 7% 15% 21% 15% 4	1907
	21st to end	Day	34% 6% 16% 26% 14% 4	1650
March	1st to 10th	Day	29% 5% 9% 27% 27% 3	4500
	11th to 20th	Day	25% 6% 15% 33% 20% 1	4666
	21st to end	Day	43% 8% 16% 23% 9%	5969
April	1st to 10th	Day	38% 5% 18% 25% 12% 3	2400
	11th to 20th	Day	40% 7% 14% 24% 12% 2	2374
	21st to end	Day	40% 7% 17% 26% 9% 1	2550
May	1st to 10th	Day	34% 7% 12% 27% 18% 2	6076
	11th to 20th	Day	38% 7% 13% 23% 14% 4	6302
	21st to end	Day	37% 7% 14% 26% 16% 1	6926
June	1st to 10th	Day	29% 10% 20% 26% 14% 2	2800
	11th to 20th	Day	29% 6% 20% 25% 16% 3	2800
	21st to end	Day	20% 6% 16% 31% 23% 5%	2800
July	1st to 10th	Day	22% 7% 13% 32% 23% 2	6271
	11th to 20th	Day	23% 6% 12% 30% 23% 7%	6265
	21st to end	Day	23% 7% 13% 25% 24% 8%	6705
August	1st to 10th	Day	25% 7% 16% 23% 18% 10%	4536
	11th to 20th	Day	24% 7% 16% 28% 21% 4	4081
	21st to end	Day	17% 5% 11% 27% 29% 11%	4311
September	1st to 10th	Day	21% 4 9% 29% 27% 9%	2400
	11th to 20th	Day	23% 6% 10% 30% 24% 7%	2320
	21st to end	Day	24% 4 9% 33% 26% 4	2200
October	1st to 10th	Day	18% 3 9% 21% 33% 16%	3337
	11th to 20th	Day	23% 4 12% 33% 25% 4	3090
	21st to end	Day	27% 6% 15% 31% 17% 4	3091
November	1st to 10th	Day	24% 6% 14% 27% 23% 5%	1763
	11th to 20th	Day	26% 5% 12% 29% 23% 5%	1782
	21st to end	Day	28% 6% 14% 32% 17% 3	1600
December	1st to 10th	Day	29% 8% 17% 28% 17% 1	2620
	11th to 20th	Day	26% 8% 19% 35% 11% 1	3024
	21st to end	Day	34% 4 9% 35% 17% 1	4004
January	1st to 10th	Night	38% 8% 12% 28% 13% 2	6327
	11th to 20th	Night	35% 8% 14% 23% 17% 3	6340
	21st to end	Night	20% 10% 14% 31% 20% 5%	6974
February	1st to 10th	Night	39% 10% 14% 20% 14% 2	2635
	11th to 20th	Night	36% 7% 14% 25% 16% 3	2389
	21st to end	Night	33% 6% 13% 27% 15% 6%	1980
March	1st to 10th	Night	29% 7% 8% 28% 24% 4	5374
	11th to 20th	Night	26% 7% 18% 27% 21% 1	5300
	21st to end	Night	43% 10% 17% 20% 10% 1	4984
April	1st to 10th	Night	38% 7% 14% 24% 14% 3	2000
	11th to 20th	Night	36% 6% 12% 26% 17% 2	1977
	21st to end	Night	35% 8% 14% 28% 13% 1	1850
May	1st to 10th	Night	32% 7% 10% 28% 22% 1	3889
	11th to 20th	Night	34% 8% 15% 27% 13% 2	3618
	21st to end	Night	40% 8% 10% 26% 16% 1	3972
June	1st to 10th	Night	28% 8% 19% 29% 14% 3	1600
	11th to 20th	Night	30% 9% 21% 23% 15% 3	1600
	21st to end	Night	24% 7% 16% 26% 22% 5%	1600
July	1st to 10th	Night	22% 6% 16% 30% 24% 3	3600
	11th to 20th	Night	22% 6% 12% 31% 22% 6%	3592
	21st to end	Night	28% 5% 15% 26% 21% 6%	3856
August	1st to 10th	Night	30% 7% 14% 21% 20% 9%	2600
	11th to 20th	Night	23% 6% 20% 25% 22% 5%	3040
	21st to end	Night	19% 5% 12% 25% 30% 9%	3597
September	1st to 10th	Night	20% 5% 7% 30% 27% 10%	2000
	11th to 20th	Night	25% 6% 10% 26% 24% 8%	2080
	21st to end	Night	24% 4 8% 29% 27% 8%	2200
October	1st to 10th	Night	19% 3 9% 23% 31% 16%	3693
	11th to 20th	Night	24% 6% 10% 30% 26% 5%	3806
	21st to end	Night	28% 4 13% 29% 18% 8%	4467
November	1st to 10th	Night	31% 6% 14% 24% 20% 6%	2535
	11th to 20th	Night	27% 6% 11% 28% 23% 5%	2615
	21st to end	Night	26% 6% 15% 30% 19% 4	2800
December	1st to 10th	Night	27% 7% 17% 30% 17% 3	4570
	11th to 20th	Night	30% 8% 17% 32% 12% 1	5182
	21st to end	Night	35% 6% 9% 33% 15% 2	6974

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	8% 13% 32% 26% 14% 7%	300
	11th to 20th	Day	17% 15% 29% 24% 11% 4	300
	21st to end	Day	14% 26% 30% 20% 8% 2	330
February	1st to 10th	Day	15% 21% 39% 19% 5% 1	300
	11th to 20th	Day	12% 17% 39% 25% 7%	300
	21st to end	Day	11% 20% 38% 24% 4 2	249
March	1st to 10th	Day	12% 18% 38% 20% 10% 3	300
	11th to 20th	Day	13% 14% 38% 21% 13% 3	340
	21st to end	Day	22% 14% 31% 22% 9% 2	550
April	1st to 10th	Day	21% 16% 34% 24% 5% 1	500
	11th to 20th	Day	23% 19% 35% 18% 3 1	492
	21st to end	Day	20% 13% 28% 26% 11% 2	650
May	1st to 10th	Day	17% 13% 29% 23% 13% 3	703
	11th to 20th	Day	22% 10% 24% 25% 14% 5%	725
	21st to end	Day	18% 11% 32% 23% 11% 5%	789
June	1st to 10th	Day	10% 9% 27% 31% 19% 5%	730
	11th to 20th	Day	12% 12% 33% 30% 12% 2	730
	21st to end	Day	8% 10% 29% 32% 18% 3	730
July	1st to 10th	Day	5% 4 26% 40% 22% 3	721
	11th to 20th	Day	5% 7% 30% 37% 18% 3	718
	21st to end	Day	6% 6% 26% 36% 22% 4	794
August	1st to 10th	Day	6% 6% 29% 39% 17% 3	726
	11th to 20th	Day	6% 7% 28% 38% 17% 5%	595
	21st to end	Day	6% 10% 27% 34% 18% 5%	583
September	1st to 10th	Day	8% 8% 28% 36% 16% 5%	530
	11th to 20th	Day	9% 7% 30% 32% 17% 6%	450
	21st to end	Day	14% 11% 29% 27% 13% 7%	330
October	1st to 10th	Day	17% 11% 23% 27% 16% 6%	309
	11th to 20th	Day	20% 15% 27% 21% 13% 5%	300
	21st to end	Day	13% 22% 27% 23% 13% 2	330
November	1st to 10th	Day	15% 16% 34% 18% 12% 4	300
	11th to 20th	Day	15% 16% 34% 21% 12% 3	300
	21st to end	Day	12% 20% 26% 27% 13% 2	300
December	1st to 10th	Day	15% 18% 33% 23% 8% 2	300
	11th to 20th	Day	13% 16% 38% 24% 9%	300
	21st to end	Day	12% 16% 35% 27% 9% 1	330
January	1st to 10th	Night	8% 18% 32% 29% 12% 1	1000
	11th to 20th	Night	11% 22% 32% 25% 9% 2	1000
	21st to end	Night	9% 22% 34% 27% 7% 1	1100
February	1st to 10th	Night	11% 19% 35% 27% 7% 1	835
	11th to 20th	Night	8% 18% 36% 28% 9% 1	784
	21st to end	Night	9% 12% 38% 30% 9% 1	660
March	1st to 10th	Night	11% 13% 35% 32% 8% 1	800
	11th to 20th	Night	9% 10% 35% 35% 9% 1	790
	21st to end	Night	16% 11% 29% 35% 9% 1	660
April	1st to 10th	Night	15% 11% 32% 34% 8%	600
	11th to 20th	Night	18% 13% 35% 28% 6% 1	593
	21st to end	Night	14% 12% 29% 33% 11% 1	600
May	1st to 10th	Night	13% 9% 27% 35% 14% 2	600
	11th to 20th	Night	17% 8% 23% 36% 14% 2	591
	21st to end	Night	19% 8% 34% 28% 10% 1	650
June	1st to 10th	Night	11% 7% 28% 39% 15% 1	600
	11th to 20th	Night	12% 7% 39% 34% 9%	600
	21st to end	Night	9% 6% 28% 45% 12%	600
July	1st to 10th	Night	6% 3 25% 45% 19% 1	585
	11th to 20th	Night	5% 4 27% 50% 14%	582
	21st to end	Night	4 3 24% 52% 18%	657
August	1st to 10th	Night	5% 4 23% 53% 16% 1	597
	11th to 20th	Night	5% 4 25% 45% 20% 1	594
	21st to end	Night	5% 5% 23% 45% 22% 2	660
September	1st to 10th	Night	6% 4 21% 47% 19% 3	600
	11th to 20th	Night	10% 6% 22% 43% 18% 2	600
	21st to end	Night	12% 8% 26% 38% 16% 1	600
October	1st to 10th	Night	14% 10% 24% 34% 16% 1	681
	11th to 20th	Night	13% 12% 29% 31% 12% 1	776
	21st to end	Night	13% 16% 31% 28% 10% 2	1045
November	1st to 10th	Night	9% 15% 34% 32% 9% 2	975
	11th to 20th	Night	11% 17% 31% 30% 9% 1	1000
	21st to end	Night	8% 20% 33% 31% 8% 1	1000
December	1st to 10th	Night	9% 20% 34% 28% 9% 1	1000
	11th to 20th	Night	8% 16% 35% 31% 9% 1	1000
	21st to end	Night	13% 18% 32% 27% 9% 1	1100

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