Rocky Gap State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rocky Gap State Park clear sky chart from 2005-11-06 to 2026-10-14.

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	14% 8% 3 7% 5% 5% 5% 4 6% 8% 36%	149223
	Night	14% 8% 3 8% 5% 4 4 4 5% 7% 38%	142470
Transparency	Day	44% 7% 13% 22% 13% 2	152824
	Night	43% 7% 13% 22% 13% 2	146940
Seeing	Day	23% 15% 27% 20% 11% 4	17366
	Night	20% 14% 25% 28% 12% 1	26925

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% 12% 5% 14% 6% 4 3 3 5% 6% 30%	5039
	11th to 20th	Day	10% 12% 6% 12% 7% 6% 5% 4 5% 6% 27%	5280
	21st to end	Day	13% 9% 3 10% 6% 5% 5% 4 5% 7% 33%	5780
February	1st to 10th	Day	13% 13% 3 9% 5% 4 5% 3 5% 6% 34%	1890
	11th to 20th	Day	14% 10% 4 10% 5% 6% 5% 4 5% 6% 32%	1843
	21st to end	Day	16% 9% 4 11% 5% 4 3 3 5% 6% 36%	1741
March	1st to 10th	Day	16% 11% 3 7% 4 4 4 3 4 5% 39%	5045
	11th to 20th	Day	12% 7% 3 6% 4 4 4 4 6% 8% 43%	5090
	21st to end	Day	13% 10% 3 8% 5% 4 5% 4 5% 6% 38%	5586
April	1st to 10th	Day	14% 10% 3 7% 6% 4 5% 4 5% 7% 35%	2487
	11th to 20th	Day	12% 8% 3 6% 6% 5% 4 3 5% 7% 40%	2494
	21st to end	Day	19% 7% 2 6% 4 4 5% 4 6% 7% 37%	2625
May	1st to 10th	Day	19% 7% 3 7% 5% 6% 5% 4 7% 7% 30%	7616
	11th to 20th	Day	20% 7% 2 6% 4 5% 5% 4 7% 8% 32%	7721
	21st to end	Day	23% 6% 2 6% 4 4 4 3 5% 7% 34%	9045
June	1st to 10th	Day	12% 5% 2 5% 5% 4 5% 4 7% 8% 41%	2940
	11th to 20th	Day	11% 5% 2 7% 5% 5% 7% 6% 7% 9% 36%	2940
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 5% 7% 11% 40%	2940
July	1st to 10th	Day	10% 5% 2 7% 5% 5% 6% 4 6% 8% 43%	8280
	11th to 20th	Day	7% 6% 3 8% 6% 6% 6% 5% 8% 11% 35%	7706
	21st to end	Day	9% 6% 3 7% 5% 5% 6% 5% 7% 9% 38%	8340
August	1st to 10th	Day	15% 7% 3 8% 5% 6% 6% 5% 8% 9% 28%	6014
	11th to 20th	Day	12% 6% 2 6% 5% 5% 6% 5% 7% 9% 36%	5933
	21st to end	Day	9% 4 1 5% 4 5% 5% 5% 7% 10% 45%	6080
September	1st to 10th	Day	14% 5% 2 5% 4 4 4 3 6% 7% 46%	2520
	11th to 20th	Day	13% 5% 2 6% 3 3 4 3 5% 6% 48%	2432
	21st to end	Day	21% 7% 3 6% 4 4 5% 4 6% 6% 35%	2240
October	1st to 10th	Day	16% 5% 2 5% 3 4 4 3 6% 6% 46%	2100
	11th to 20th	Day	15% 7% 2 7% 5% 4 4 3 5% 6% 42%	2030
	21st to end	Day	14% 7% 3 6% 4 5% 4 4 5% 7% 42%	2200
November	1st to 10th	Day	9% 6% 3 5% 3 4 4 3 5% 7% 50%	2041
	11th to 20th	Day	14% 10% 2 6% 4 4 4 4 6% 6% 40%	1727
	21st to end	Day	15% 10% 2 7% 5% 4 5% 3 6% 6% 36%	1680
December	1st to 10th	Day	13% 8% 4 10% 6% 5% 5% 4 4 6% 35%	2680
	11th to 20th	Day	20% 12% 3 7% 4 4 3 3 5% 6% 32%	3070
	21st to end	Day	17% 11% 5% 10% 5% 6% 6% 4 6% 7% 23%	4048
January	1st to 10th	Night	10% 11% 4 13% 6% 5% 5% 4 5% 6% 30%	7836
	11th to 20th	Night	9% 10% 5% 12% 5% 4 4 3 5% 6% 35%	7680
	21st to end	Night	13% 9% 3 8% 5% 4 4 3 5% 6% 39%	8401
February	1st to 10th	Night	14% 9% 3 7% 5% 6% 4 4 6% 6% 37%	2730
	11th to 20th	Night	15% 10% 4 8% 5% 5% 5% 4 5% 6% 33%	2663
	21st to end	Night	14% 9% 4 8% 6% 4 4 5% 6% 7% 33%	2059
March	1st to 10th	Night	17% 9% 2 6% 4 3 3 3 5% 6% 41%	5028
	11th to 20th	Night	11% 8% 2 6% 4 3 3 3 4 7% 48%	5090
	21st to end	Night	12% 7% 3 8% 5% 4 4 3 5% 5% 44%	5588
April	1st to 10th	Night	17% 9% 3 7% 5% 4 5% 4 6% 5% 37%	2132
	11th to 20th	Night	14% 7% 2 5% 5% 4 5% 4 6% 8% 41%	2075
	21st to end	Night	16% 5% 2 5% 4 4 4 4 5% 8% 43%	2012
May	1st to 10th	Night	19% 9% 3 7% 4 4 5% 3 6% 8% 31%	5237
	11th to 20th	Night	20% 7% 2 6% 4 4 4 4 6% 8% 34%	5121
	21st to end	Night	25% 7% 3 6% 4 4 4 3 4 6% 34%	5108
June	1st to 10th	Night	11% 5% 1 4 4 4 6% 4 5% 8% 47%	1680
	11th to 20th	Night	12% 4 2 6% 5% 4 5% 4 7% 9% 41%	1680
	21st to end	Night	9% 5% 2 6% 5% 4 4 4 9% 9% 43%	1680
July	1st to 10th	Night	11% 6% 2 6% 5% 5% 5% 4 6% 8% 42%	4678
	11th to 20th	Night	8% 7% 3 8% 6% 5% 5% 4 7% 9% 36%	5232
	21st to end	Night	9% 6% 2 7% 5% 5% 5% 5% 7% 9% 39%	5736
August	1st to 10th	Night	14% 7% 3 9% 6% 5% 6% 5% 7% 9% 29%	4135
	11th to 20th	Night	12% 7% 3 8% 5% 5% 5% 5% 6% 7% 38%	4095
	21st to end	Night	12% 4 2 6% 4 5% 5% 3 5% 8% 44%	5015
September	1st to 10th	Night	14% 4 2 5% 4 4 4 3 4 7% 49%	2100
	11th to 20th	Night	12% 6% 2 5% 4 4 3 4 5% 6% 50%	2184
	21st to end	Night	22% 6% 2 5% 3 4 4 3 5% 6% 39%	2379
October	1st to 10th	Night	17% 5% 2 5% 4 4 3 3 5% 6% 46%	2520
	11th to 20th	Night	15% 6% 1 5% 3 4 4 3 4 7% 48%	2437
	21st to end	Night	16% 5% 1 6% 4 4 4 4 5% 6% 45%	2640
November	1st to 10th	Night	9% 7% 3 6% 4 4 4 3 4 6% 50%	2476
	11th to 20th	Night	14% 10% 2 6% 5% 4 4 4 5% 6% 39%	2888
	21st to end	Night	14% 8% 3 8% 5% 5% 5% 4 5% 6% 37%	2940
December	1st to 10th	Night	10% 9% 4 10% 4 5% 5% 4 5% 6% 38%	4720
	11th to 20th	Night	18% 10% 3 8% 5% 5% 4 4 5% 5% 32%	5345
	21st to end	Night	16% 11% 4 10% 6% 6% 5% 4 6% 7% 25%	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	54% 6% 12% 20% 6% 2	5040
	11th to 20th	Day	53% 8% 9% 14% 12% 4	5280
	21st to end	Day	48% 7% 12% 24% 8% 1	5780
February	1st to 10th	Day	50% 6% 13% 20% 10% 1	1890
	11th to 20th	Day	51% 6% 14% 19% 10% 1	1852
	21st to end	Day	50% 5% 14% 18% 11% 2	1741
March	1st to 10th	Day	46% 6% 10% 21% 12% 5%	5045
	11th to 20th	Day	36% 6% 14% 27% 13% 3	5090
	21st to end	Day	45% 7% 10% 20% 16% 3	5586
April	1st to 10th	Day	47% 8% 12% 17% 13% 3	2487
	11th to 20th	Day	42% 7% 12% 19% 17% 3	2494
	21st to end	Day	44% 7% 11% 24% 12% 2	2625
May	1st to 10th	Day	50% 7% 10% 20% 11% 2	7651
	11th to 20th	Day	46% 7% 12% 26% 8% 1	7725
	21st to end	Day	48% 8% 11% 16% 15% 3	9061
June	1st to 10th	Day	38% 10% 14% 21% 16% 1	2940
	11th to 20th	Day	39% 12% 14% 21% 13% 1	2940
	21st to end	Day	35% 10% 17% 23% 14% 1	2940
July	1st to 10th	Day	39% 8% 13% 24% 14% 2	8210
	11th to 20th	Day	39% 9% 15% 26% 10% 1	7636
	21st to end	Day	40% 6% 11% 24% 18% 1	8156
August	1st to 10th	Day	49% 9% 16% 18% 8%	6001
	11th to 20th	Day	43% 7% 15% 23% 12%	5972
	21st to end	Day	32% 7% 19% 28% 13% 1	6080
September	1st to 10th	Day	37% 8% 12% 20% 19% 3	2520
	11th to 20th	Day	36% 6% 11% 27% 17% 2	2432
	21st to end	Day	47% 8% 11% 17% 15% 2	2240
October	1st to 10th	Day	32% 5% 10% 25% 23% 4	3360
	11th to 20th	Day	35% 5% 12% 26% 16% 6%	3270
	21st to end	Day	27% 5% 14% 30% 22% 2	3538
November	1st to 10th	Day	34% 6% 13% 23% 20% 4	2041
	11th to 20th	Day	42% 6% 13% 19% 17% 2	1727
	21st to end	Day	46% 8% 14% 22% 10% 1	1680
December	1st to 10th	Day	50% 6% 14% 23% 5% 3	2680
	11th to 20th	Day	52% 5% 14% 20% 7% 1	3066
	21st to end	Day	56% 9% 14% 11% 9%	4048
January	1st to 10th	Night	51% 7% 11% 21% 10% 1	7837
	11th to 20th	Night	47% 6% 10% 18% 14% 5%	7680
	21st to end	Night	43% 6% 11% 27% 11% 2	8401
February	1st to 10th	Night	44% 8% 13% 22% 11% 1	2730
	11th to 20th	Night	50% 7% 11% 19% 12% 1	2665
	21st to end	Night	48% 8% 12% 19% 10% 3	2059
March	1st to 10th	Night	42% 7% 11% 24% 11% 5%	5028
	11th to 20th	Night	34% 8% 14% 31% 10% 4	5090
	21st to end	Night	40% 6% 12% 22% 16% 3	5588
April	1st to 10th	Night	46% 8% 12% 17% 15% 2	2132
	11th to 20th	Night	40% 8% 13% 21% 15% 4	2075
	21st to end	Night	38% 8% 13% 26% 11% 3	2012
May	1st to 10th	Night	50% 7% 13% 17% 11% 3	5264
	11th to 20th	Night	45% 8% 14% 24% 9% 1	5122
	21st to end	Night	49% 7% 12% 19% 11% 2	5115
June	1st to 10th	Night	34% 9% 11% 26% 17% 2	1680
	11th to 20th	Night	37% 10% 15% 24% 13% 1	1680
	21st to end	Night	33% 8% 18% 24% 16% 1	1680
July	1st to 10th	Night	39% 7% 14% 22% 14% 3	4640
	11th to 20th	Night	42% 8% 15% 22% 12% 1	5182
	21st to end	Night	38% 8% 13% 21% 19% 1	5606
August	1st to 10th	Night	50% 8% 15% 19% 9%	4124
	11th to 20th	Night	43% 7% 14% 22% 13% 1	4122
	21st to end	Night	37% 6% 16% 28% 12% 1	5015
September	1st to 10th	Night	36% 7% 14% 22% 18% 3	2100
	11th to 20th	Night	34% 6% 12% 27% 19% 2	2184
	21st to end	Night	45% 7% 12% 19% 16% 1	2379
October	1st to 10th	Night	35% 4 10% 27% 23% 1	4040
	11th to 20th	Night	29% 5% 11% 25% 24% 6%	3936
	21st to end	Night	27% 5% 11% 31% 24% 2	4252
November	1st to 10th	Night	35% 6% 13% 23% 20% 4	2476
	11th to 20th	Night	43% 7% 10% 23% 14% 4	2888
	21st to end	Night	46% 7% 13% 21% 11% 2	2940
December	1st to 10th	Night	46% 5% 15% 27% 7%	4720
	11th to 20th	Night	51% 6% 14% 20% 9%	5348
	21st to end	Night	54% 10% 14% 15% 7%	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	35% 25% 27% 10% 3	289
	11th to 20th	Day	41% 24% 26% 7% 2	330
	21st to end	Day	34% 28% 25% 10% 2	363
February	1st to 10th	Day	32% 25% 32% 10% 2	330
	11th to 20th	Day	41% 27% 26% 4 1	330
	21st to end	Day	31% 26% 30% 12% 2	399
March	1st to 10th	Day	32% 22% 27% 16% 3	540
	11th to 20th	Day	31% 25% 26% 12% 4 1	540
	21st to end	Day	29% 23% 29% 13% 4 1	594
April	1st to 10th	Day	32% 22% 24% 17% 5% 1	540
	11th to 20th	Day	23% 22% 28% 17% 7% 4	532
	21st to end	Day	30% 18% 29% 14% 7% 2	540
May	1st to 10th	Day	30% 18% 27% 14% 8% 3	543
	11th to 20th	Day	25% 17% 28% 18% 9% 3	567
	21st to end	Day	26% 11% 22% 22% 12% 7%	617
June	1st to 10th	Day	18% 14% 29% 21% 15% 5%	570
	11th to 20th	Day	19% 11% 30% 23% 12% 5%	570
	21st to end	Day	13% 12% 30% 25% 16% 5%	570
July	1st to 10th	Day	13% 6% 24% 29% 19% 10%	565
	11th to 20th	Day	7% 6% 27% 32% 20% 8%	564
	21st to end	Day	14% 6% 29% 29% 18% 5%	620
August	1st to 10th	Day	15% 8% 22% 27% 19% 8%	566
	11th to 20th	Day	15% 4 26% 27% 19% 8%	559
	21st to end	Day	14% 5% 26% 25% 21% 10%	627
September	1st to 10th	Day	17% 8% 22% 24% 21% 8%	570
	11th to 20th	Day	17% 5% 19% 30% 21% 8%	570
	21st to end	Day	30% 10% 24% 20% 13% 3	570
October	1st to 10th	Day	21% 9% 25% 24% 18% 4	570
	11th to 20th	Day	21% 16% 28% 23% 11% 2	542
	21st to end	Day	20% 20% 28% 21% 9% 2	583
November	1st to 10th	Day	17% 17% 31% 24% 10% 2	527
	11th to 20th	Day	27% 19% 29% 19% 4	267
	21st to end	Day	29% 21% 29% 17% 3	220
December	1st to 10th	Day	29% 28% 28% 10% 5%	220
	11th to 20th	Day	29% 26% 23% 18% 4	220
	21st to end	Day	33% 18% 24% 21% 4	242
January	1st to 10th	Night	23% 25% 31% 18% 3	840
	11th to 20th	Night	26% 21% 31% 21% 2	840
	21st to end	Night	23% 24% 31% 19% 2	924
February	1st to 10th	Night	22% 21% 31% 24% 2	840
	11th to 20th	Night	27% 25% 31% 16% 1	823
	21st to end	Night	26% 20% 31% 21% 2	692
March	1st to 10th	Night	25% 19% 32% 21% 4	840
	11th to 20th	Night	27% 21% 26% 21% 5%	840
	21st to end	Night	23% 18% 34% 20% 5% 1	924
April	1st to 10th	Night	26% 20% 28% 22% 4	840
	11th to 20th	Night	20% 17% 27% 27% 8%	831
	21st to end	Night	20% 14% 26% 32% 8%	752
May	1st to 10th	Night	22% 11% 26% 28% 12% 1	630
	11th to 20th	Night	24% 9% 23% 33% 11%	586
	21st to end	Night	18% 8% 18% 31% 23% 2	455
June	1st to 10th	Night	13% 5% 25% 35% 22%	420
	11th to 20th	Night	14% 7% 21% 38% 19%	420
	21st to end	Night	10% 4 21% 40% 23% 1	420
July	1st to 10th	Night	11% 4 15% 40% 27% 3	410
	11th to 20th	Night	8% 3 13% 37% 35% 4	594
	21st to end	Night	9% 3 19% 37% 30% 2	690
August	1st to 10th	Night	11% 3 14% 40% 30% 3	627
	11th to 20th	Night	11% 4 14% 40% 28% 4	624
	21st to end	Night	14% 3 17% 34% 28% 4	906
September	1st to 10th	Night	17% 4 17% 34% 25% 4	840
	11th to 20th	Night	16% 4 13% 33% 29% 4	840
	21st to end	Night	26% 7% 17% 29% 18% 3	840
October	1st to 10th	Night	20% 6% 21% 30% 22% 2	840
	11th to 20th	Night	18% 14% 26% 30% 12% 1	813
	21st to end	Night	21% 14% 24% 30% 10% 1	880
November	1st to 10th	Night	15% 12% 26% 35% 11%	820
	11th to 20th	Night	23% 19% 23% 27% 7% 1	840
	21st to end	Night	23% 17% 27% 26% 6%	840
December	1st to 10th	Night	24% 19% 29% 22% 5%	840
	11th to 20th	Night	24% 18% 30% 26% 3	840
	21st to end	Night	22% 18% 28% 30% 2	924

Page generated at 2026-10-11 05:06:30. Version ac07

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