Jones Gap State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jones Gap State Park clear sky chart from 2005-11-06 to 2025-12-18.

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% 5% 2 5% 4 4 5% 4 6% 8% 43%	127068
	Night	16% 5% 2 5% 4 4 4 3 5% 7% 45%	123981
Transparency	Day	38% 7% 12% 19% 18% 6%	130779
	Night	38% 6% 11% 18% 20% 7%	128339
Seeing	Day	18% 12% 25% 23% 15% 7%	16545
	Night	18% 9% 24% 27% 18% 3	26608

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% 4 2 4 3 3 3 2 4 5% 58%	4056
	11th to 20th	Day	12% 4 2 4 3 3 3 2 3 3 62%	4060
	21st to end	Day	20% 4 1 5% 4 4 3 3 3 5% 49%	4466
February	1st to 10th	Day	15% 6% 2 5% 4 4 4 3 6% 6% 46%	1903
	11th to 20th	Day	20% 6% 2 5% 4 3 3 4 4 5% 44%	1948
	21st to end	Day	19% 6% 2 6% 5% 4 4 4 4 5% 42%	1650
March	1st to 10th	Day	22% 6% 2 4 3 4 4 3 5% 6% 42%	4838
	11th to 20th	Day	13% 4 2 5% 3 3 3 3 4 6% 55%	4980
	21st to end	Day	20% 5% 2 4 3 3 3 3 5% 5% 46%	5465
April	1st to 10th	Day	13% 5% 2 5% 4 5% 4 4 6% 7% 46%	2200
	11th to 20th	Day	14% 5% 2 5% 4 4 4 4 6% 7% 46%	2376
	21st to end	Day	13% 5% 2 4 5% 4 4 4 5% 7% 48%	2600
May	1st to 10th	Day	13% 7% 3 7% 5% 5% 5% 4 6% 8% 37%	5862
	11th to 20th	Day	20% 7% 3 7% 5% 5% 6% 4 7% 8% 29%	5861
	21st to end	Day	13% 5% 2 6% 4 5% 5% 4 7% 9% 39%	6433
June	1st to 10th	Day	11% 6% 2 7% 6% 6% 6% 7% 9% 11% 30%	2600
	11th to 20th	Day	7% 5% 2 6% 6% 5% 7% 7% 9% 11% 36%	2600
	21st to end	Day	7% 5% 2 6% 7% 6% 6% 7% 8% 11% 36%	2600
July	1st to 10th	Day	8% 4 2 6% 5% 6% 7% 5% 8% 11% 38%	5900
	11th to 20th	Day	9% 4 2 8% 6% 6% 7% 6% 8% 12% 32%	5900
	21st to end	Day	10% 6% 3 8% 7% 8% 8% 7% 9% 10% 25%	6424
August	1st to 10th	Day	15% 7% 2 8% 5% 6% 6% 6% 7% 10% 28%	4234
	11th to 20th	Day	11% 4 2 6% 5% 5% 6% 6% 8% 11% 36%	4174
	21st to end	Day	8% 4 2 6% 4 4 5% 4 6% 8% 49%	4291
September	1st to 10th	Day	9% 5% 2 6% 5% 5% 6% 5% 7% 9% 40%	2200
	11th to 20th	Day	16% 6% 3 5% 5% 5% 6% 4 7% 7% 36%	2200
	21st to end	Day	17% 6% 2 5% 4 4 5% 4 6% 7% 41%	2200
October	1st to 10th	Day	14% 5% 1 4 3 3 4 3 4 7% 53%	2170
	11th to 20th	Day	13% 4 2 3 2 2 4 2 4 5% 60%	2000
	21st to end	Day	16% 3 1 3 3 2 3 2 4 5% 57%	2200
November	1st to 10th	Day	14% 5% 2 4 2 2 3 2 4 5% 56%	1975
	11th to 20th	Day	13% 4 1 3 2 2 3 3 4 6% 56%	1890
	21st to end	Day	15% 6% 1 4 2 3 3 3 5% 5% 53%	1890
December	1st to 10th	Day	17% 6% 2 5% 3 3 3 2 3 5% 52%	3020
	11th to 20th	Day	19% 5% 1 5% 3 3 4 3 5% 6% 46%	3436
	21st to end	Day	25% 4 1 3 2 3 3 2 4 6% 47%	4466
January	1st to 10th	Night	15% 3 1 4 3 2 3 2 3 4 60%	5889
	11th to 20th	Night	11% 5% 2 4 3 3 3 3 4 4 57%	5900
	21st to end	Night	19% 4 1 3 3 3 3 2 4 6% 50%	6490
February	1st to 10th	Night	15% 6% 2 5% 4 4 3 3 5% 5% 49%	2495
	11th to 20th	Night	20% 7% 2 4 3 3 3 3 5% 4 46%	2338
	21st to end	Night	18% 5% 2 5% 4 4 4 3 5% 6% 44%	1980
March	1st to 10th	Night	20% 6% 2 5% 3 3 3 3 5% 6% 45%	5013
	11th to 20th	Night	12% 3 1 3 2 3 3 3 5% 7% 56%	4980
	21st to end	Night	19% 4 2 5% 3 3 4 3 5% 6% 47%	5467
April	1st to 10th	Night	15% 5% 2 4 3 3 3 4 4 7% 49%	2200
	11th to 20th	Night	14% 6% 1 5% 4 2 3 2 5% 7% 51%	1990
	21st to end	Night	13% 5% 2 5% 4 3 3 4 5% 7% 50%	1800
May	1st to 10th	Night	14% 6% 3 6% 5% 5% 5% 4 7% 8% 37%	4033
	11th to 20th	Night	24% 6% 2 5% 4 4 4 4 6% 8% 33%	4032
	21st to end	Night	16% 5% 2 5% 4 4 4 3 6% 10% 41%	4421
June	1st to 10th	Night	10% 7% 3 6% 5% 6% 6% 5% 9% 12% 32%	1800
	11th to 20th	Night	11% 5% 2 6% 5% 4 4 6% 8% 10% 39%	1800
	21st to end	Night	8% 6% 2 6% 5% 6% 5% 4 7% 11% 40%	1800
July	1st to 10th	Night	12% 5% 2 6% 6% 7% 6% 6% 7% 10% 33%	4058
	11th to 20th	Night	12% 5% 2 7% 5% 6% 6% 6% 9% 13% 30%	4057
	21st to end	Night	15% 6% 3 8% 5% 6% 6% 5% 8% 10% 27%	4427
August	1st to 10th	Night	15% 7% 3 7% 5% 6% 5% 5% 7% 9% 31%	2915
	11th to 20th	Night	17% 5% 3 8% 5% 5% 6% 5% 6% 9% 31%	2875
	21st to end	Night	9% 5% 2 6% 5% 4 5% 4 6% 8% 47%	3568
September	1st to 10th	Night	12% 6% 3 7% 5% 4 5% 4 6% 9% 40%	2200
	11th to 20th	Night	17% 7% 2 6% 5% 5% 5% 4 6% 8% 36%	2200
	21st to end	Night	18% 6% 2 5% 4 4 4 3 5% 7% 43%	2200
October	1st to 10th	Night	15% 4 2 5% 4 3 4 3 5% 5% 50%	2229
	11th to 20th	Night	15% 4 2 4 3 3 4 3 4 5% 54%	2400
	21st to end	Night	16% 4 1 4 2 3 3 3 4 4 57%	2640
November	1st to 10th	Night	15% 4 1 4 3 3 2 2 4 5% 56%	2540
	11th to 20th	Night	15% 5% 1 3 3 3 3 3 4 4 55%	2730
	21st to end	Night	16% 4 1 3 2 4 4 4 5% 6% 51%	2730
December	1st to 10th	Night	16% 6% 1 4 3 3 3 3 4 5% 54%	4380
	11th to 20th	Night	20% 5% 1 5% 3 3 4 3 4 5% 47%	4914
	21st to end	Night	23% 5% 1 3 2 3 3 3 5% 5% 47%	6490

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% 3 5% 20% 31% 10%	4057
	11th to 20th	Day	30% 3 4 13% 38% 12%	4060
	21st to end	Day	39% 2 5% 17% 25% 12%	4466
February	1st to 10th	Day	39% 4 9% 21% 20% 6%	1903
	11th to 20th	Day	43% 5% 9% 17% 20% 7%	1958
	21st to end	Day	44% 5% 7% 14% 21% 9%	1650
March	1st to 10th	Day	43% 4 7% 15% 17% 13%	4838
	11th to 20th	Day	33% 3 6% 13% 24% 21%	4980
	21st to end	Day	40% 4 7% 25% 18% 7%	5465
April	1st to 10th	Day	34% 6% 10% 20% 22% 6%	2200
	11th to 20th	Day	36% 6% 10% 20% 20% 9%	2376
	21st to end	Day	35% 7% 12% 26% 17% 3	2600
May	1st to 10th	Day	43% 8% 16% 19% 13% 2	5897
	11th to 20th	Day	50% 9% 14% 16% 9% 1	5865
	21st to end	Day	39% 9% 14% 18% 17% 3	6447
June	1st to 10th	Day	42% 11% 17% 20% 8% 1	2600
	11th to 20th	Day	36% 12% 20% 20% 10% 2	2600
	21st to end	Day	37% 12% 19% 18% 13% 2	2600
July	1st to 10th	Day	37% 12% 19% 22% 10% 1	5835
	11th to 20th	Day	41% 13% 29% 14% 3 1	5831
	21st to end	Day	47% 14% 17% 16% 6%	6240
August	1st to 10th	Day	48% 10% 16% 22% 5%	4221
	11th to 20th	Day	37% 11% 23% 16% 10% 3	4213
	21st to end	Day	31% 9% 14% 25% 20% 1	4291
September	1st to 10th	Day	36% 12% 13% 19% 16% 3	2200
	11th to 20th	Day	43% 8% 14% 17% 16% 2	2200
	21st to end	Day	41% 7% 12% 19% 16% 6%	2200
October	1st to 10th	Day	27% 5% 8% 19% 32% 10%	3534
	11th to 20th	Day	20% 3 5% 17% 28% 27%	3240
	21st to end	Day	29% 4 5% 22% 23% 16%	3538
November	1st to 10th	Day	32% 4 8% 19% 27% 11%	1975
	11th to 20th	Day	30% 4 7% 24% 26% 9%	1890
	21st to end	Day	34% 4 7% 22% 25% 7%	1890
December	1st to 10th	Day	37% 4 4 18% 27% 10%	3020
	11th to 20th	Day	41% 5% 8% 16% 20% 10%	3433
	21st to end	Day	39% 3 9% 25% 20% 3	4466
January	1st to 10th	Night	29% 3 7% 18% 32% 11%	5889
	11th to 20th	Night	31% 5% 5% 13% 37% 10%	5900
	21st to end	Night	37% 2 6% 16% 26% 12%	6490
February	1st to 10th	Night	37% 4 10% 21% 21% 7%	2495
	11th to 20th	Night	43% 4 7% 17% 22% 7%	2339
	21st to end	Night	41% 5% 9% 15% 23% 8%	1980
March	1st to 10th	Night	40% 5% 7% 12% 26% 9%	5013
	11th to 20th	Night	27% 4 7% 16% 26% 19%	4980
	21st to end	Night	39% 4 6% 23% 19% 9%	5467
April	1st to 10th	Night	36% 4 10% 20% 25% 5%	2200
	11th to 20th	Night	34% 4 9% 23% 23% 7%	1990
	21st to end	Night	34% 6% 12% 24% 20% 4	1800
May	1st to 10th	Night	43% 9% 13% 22% 12% 1	4060
	11th to 20th	Night	49% 8% 16% 17% 10%	4033
	21st to end	Night	37% 8% 16% 23% 13% 3	4429
June	1st to 10th	Night	40% 13% 16% 21% 9% 2	1800
	11th to 20th	Night	38% 9% 19% 23% 10% 1	1800
	21st to end	Night	37% 12% 17% 16% 14% 4	1800
July	1st to 10th	Night	44% 12% 17% 20% 6% 1	4015
	11th to 20th	Night	42% 14% 27% 14% 2 1	4006
	21st to end	Night	50% 13% 16% 16% 5% 1	4297
August	1st to 10th	Night	48% 10% 21% 16% 5%	2904
	11th to 20th	Night	47% 11% 19% 12% 10% 1	2902
	21st to end	Night	34% 9% 14% 26% 15% 1	3568
September	1st to 10th	Night	40% 10% 14% 20% 14% 3	2200
	11th to 20th	Night	44% 9% 14% 16% 15% 2	2200
	21st to end	Night	41% 6% 12% 19% 17% 5%	2200
October	1st to 10th	Night	30% 6% 10% 16% 30% 8%	3645
	11th to 20th	Night	21% 4 5% 17% 30% 22%	3899
	21st to end	Night	33% 3 4 18% 25% 17%	4252
November	1st to 10th	Night	33% 5% 8% 19% 26% 10%	2540
	11th to 20th	Night	32% 4 7% 18% 28% 11%	2730
	21st to end	Night	34% 5% 7% 20% 26% 8%	2730
December	1st to 10th	Night	34% 4 7% 19% 27% 9%	4380
	11th to 20th	Night	42% 5% 8% 15% 19% 10%	4916
	21st to end	Night	40% 3 10% 21% 22% 3	6490

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	25% 27% 37% 9% 3	300
	11th to 20th	Day	30% 24% 30% 14% 2	300
	21st to end	Day	24% 24% 40% 10% 2	330
February	1st to 10th	Day	22% 27% 40% 9% 2	300
	11th to 20th	Day	36% 30% 26% 8%	300
	21st to end	Day	31% 27% 33% 8% 1	249
March	1st to 10th	Day	22% 22% 31% 17% 6% 1	451
	11th to 20th	Day	25% 22% 32% 16% 4 1	500
	21st to end	Day	27% 19% 33% 15% 5% 1	550
April	1st to 10th	Day	22% 21% 28% 20% 8% 1	500
	11th to 20th	Day	18% 18% 31% 21% 11% 1	492
	21st to end	Day	19% 13% 31% 22% 11% 4	500
May	1st to 10th	Day	13% 16% 35% 21% 10% 5%	503
	11th to 20th	Day	20% 9% 25% 25% 15% 6%	527
	21st to end	Day	17% 9% 20% 25% 17% 12%	573
June	1st to 10th	Day	13% 6% 20% 33% 16% 11%	530
	11th to 20th	Day	11% 7% 20% 26% 25% 12%	530
	21st to end	Day	10% 3 19% 36% 20% 12%	530
July	1st to 10th	Day	8% 3 15% 25% 31% 18%	525
	11th to 20th	Day	8% 3 10% 28% 32% 19%	524
	21st to end	Day	8% 3 10% 31% 28% 20%	576
August	1st to 10th	Day	21% 5% 15% 25% 17% 17%	526
	11th to 20th	Day	14% 3 13% 29% 27% 14%	519
	21st to end	Day	15% 3 15% 25% 28% 15%	583
September	1st to 10th	Day	10% 4 17% 32% 24% 13%	530
	11th to 20th	Day	18% 4 15% 25% 28% 9%	530
	21st to end	Day	22% 7% 19% 26% 22% 3	530
October	1st to 10th	Day	19% 9% 22% 26% 17% 7%	530
	11th to 20th	Day	15% 11% 29% 28% 14% 3	530
	21st to end	Day	22% 9% 26% 29% 11% 3	583
November	1st to 10th	Day	22% 15% 27% 23% 9% 3	453
	11th to 20th	Day	18% 21% 38% 20% 3	330
	21st to end	Day	17% 19% 40% 18% 5% 1	330
December	1st to 10th	Day	29% 20% 36% 14% 2	330
	11th to 20th	Day	21% 18% 38% 19% 5%	321
	21st to end	Day	28% 17% 37% 14% 4 1	330
January	1st to 10th	Night	22% 16% 34% 23% 6%	800
	11th to 20th	Night	20% 15% 36% 24% 4	800
	21st to end	Night	19% 15% 40% 23% 3	880
February	1st to 10th	Night	19% 13% 35% 30% 4	800
	11th to 20th	Night	23% 17% 39% 20% 2	783
	21st to end	Night	20% 17% 38% 22% 3	660
March	1st to 10th	Night	20% 17% 33% 26% 5%	800
	11th to 20th	Night	21% 15% 33% 24% 7% 1	800
	21st to end	Night	22% 13% 34% 24% 7%	880
April	1st to 10th	Night	18% 17% 31% 26% 8%	800
	11th to 20th	Night	19% 14% 27% 26% 14% 1	701
	21st to end	Night	15% 8% 26% 35% 16% 1	600
May	1st to 10th	Night	14% 8% 30% 30% 18% 1	600
	11th to 20th	Night	20% 6% 20% 29% 22% 2	591
	21st to end	Night	16% 4 14% 28% 31% 7%	650
June	1st to 10th	Night	11% 3 16% 33% 33% 5%	600
	11th to 20th	Night	11% 3 13% 30% 33% 10%	600
	21st to end	Night	8% 2 10% 34% 39% 7%	600
July	1st to 10th	Night	13% 2 10% 21% 44% 10%	585
	11th to 20th	Night	9% 2 7% 24% 48% 11%	582
	21st to end	Night	8% 2 8% 27% 45% 10%	657
August	1st to 10th	Night	19% 4 9% 21% 38% 9%	597
	11th to 20th	Night	18% 2 8% 26% 37% 9%	594
	21st to end	Night	15% 3 10% 24% 39% 10%	719
September	1st to 10th	Night	15% 3 14% 27% 33% 8%	800
	11th to 20th	Night	20% 4 14% 24% 32% 7%	800
	21st to end	Night	22% 3 16% 32% 24% 3	800
October	1st to 10th	Night	17% 7% 20% 26% 23% 7%	800
	11th to 20th	Night	18% 8% 25% 30% 17% 3	800
	21st to end	Night	18% 8% 23% 34% 15% 3	880
November	1st to 10th	Night	17% 8% 24% 32% 16% 3	820
	11th to 20th	Night	17% 11% 29% 30% 12% 1	840
	21st to end	Night	16% 13% 28% 30% 12% 1	840
December	1st to 10th	Night	23% 15% 28% 27% 8%	840
	11th to 20th	Night	20% 8% 33% 32% 7%	829
	21st to end	Night	27% 10% 28% 28% 6%	880

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