Leasburg Dam State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Leasburg Dam State Park clear sky chart from 2005-11-06 to 2026-04-17.

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	3 2 1 3 2 3 3 3 5% 7% 68%	139588
	Night	3 3 1 4 3 3 4 3 5% 7% 63%	140117
Transparency	Day	17% 3 7% 15% 29% 30%	134629
	Night	20% 3 6% 13% 28% 29%	136081
Seeing	Day	6% 7% 20% 29% 26% 13%	16159
	Night	4 4 22% 42% 25% 2	26598

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	3 5% 2 4 3 3 3 2 5% 7% 63%	5318
	11th to 20th	Day	1 1 1 1 1 1 2 4 6% 81%	5340
	21st to end	Day	6% 3 1 3 2 3 3 3 5% 6% 64%	5844
February	1st to 10th	Day	2 3 1 3 2 2 3 2 4 6% 70%	1950
	11th to 20th	Day	4 4 1 4 3 3 4 3 3 6% 65%	2049
	21st to end	Day	2 2 1 3 3 2 2 3 4 5% 72%	1760
March	1st to 10th	Day	2 3 1 3 2 2 3 3 5% 6% 69%	5064
	11th to 20th	Day	5% 3 1 3 3 3 4 3 5% 5% 66%	5110
	21st to end	Day	1 3 1 4 3 4 3 3 5% 8% 65%	5646
April	1st to 10th	Day	2 3 3 2 3 3 3 5% 6% 71%	2520
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 4 77%	2444
	21st to end	Day	1 2 2 2 1 1 2 3 4 81%	2400
May	1st to 10th	Day	1 1 1 1 1 2 2 3 4 83%	5440
	11th to 20th	Day	1 1 1 2 1 2 2 2 4 5% 79%	5405
	21st to end	Day	1 1 1 1 1 2 1 3 5% 85%	6375
June	1st to 10th	Day	2 3 1 3 2 2 3 3 5% 7% 71%	2600
	11th to 20th	Day	2 1 2 1 2 2 2 3 6% 77%	2600
	21st to end	Day	4 3 1 4 4 4 4 3 8% 8% 57%	2600
July	1st to 10th	Day	3 2 1 4 4 4 5% 5% 7% 9% 57%	5879
	11th to 20th	Day	1 1 1 3 3 4 4 5% 8% 11% 59%	5880
	21st to end	Day	3 3 2 6% 5% 6% 6% 6% 9% 11% 44%	6401
August	1st to 10th	Day	2 2 1 3 3 3 5% 5% 8% 12% 58%	5527
	11th to 20th	Day	2 2 1 3 3 4 5% 4 8% 11% 57%	5366
	21st to end	Day	2 2 1 4 4 4 4 4 8% 10% 56%	5984
September	1st to 10th	Day	7% 4 1 5% 4 4 4 4 7% 8% 53%	2400
	11th to 20th	Day	6% 2 2 4 3 4 4 3 6% 8% 59%	2400
	21st to end	Day	3 2 1 2 2 2 3 2 4 7% 71%	2140
October	1st to 10th	Day	2 2 1 2 2 2 2 2 3 4 80%	3270
	11th to 20th	Day	3 2 1 3 2 2 3 2 3 5% 73%	3250
	21st to end	Day	1 1 1 1 1 1 1 1 2 3 86%	3548
November	1st to 10th	Day	2 1 1 3 2 2 2 2 4 7% 74%	2059
	11th to 20th	Day	2 2 1 3 2 2 3 3 5% 7% 70%	2100
	21st to end	Day	6% 3 1 3 3 3 3 3 5% 7% 63%	1961
December	1st to 10th	Day	5% 4 1 4 2 3 3 3 4 6% 65%	2934
	11th to 20th	Day	2 3 2 5% 3 2 3 3 3 7% 67%	3415
	21st to end	Day	2 2 1 2 2 2 3 2 4 7% 71%	4609
January	1st to 10th	Night	4 6% 2 5% 4 3 4 3 5% 6% 58%	7605
	11th to 20th	Night	1 1 1 2 1 2 2 2 4 5% 80%	7650
	21st to end	Night	5% 4 2 4 3 4 4 3 6% 6% 58%	8370
February	1st to 10th	Night	2 3 1 3 3 3 3 3 5% 7% 67%	2667
	11th to 20th	Night	4 4 1 4 3 2 3 3 5% 5% 65%	2458
	21st to end	Night	2 3 1 3 3 3 3 2 5% 6% 69%	2042
March	1st to 10th	Night	2 3 1 2 2 2 3 3 5% 7% 69%	5050
	11th to 20th	Night	5% 4 1 3 2 3 4 3 4 6% 65%	5110
	21st to end	Night	2 4 2 4 3 3 4 3 5% 6% 64%	5569
April	1st to 10th	Night	1 2 1 3 3 3 4 3 5% 7% 68%	2100
	11th to 20th	Night	3 3 1 3 3 3 3 3 4 5% 69%	2037
	21st to end	Night	1 1 1 2 2 2 2 3 5% 5% 77%	2000
May	1st to 10th	Night	2 2 1 2 2 2 2 2 3 4 78%	4540
	11th to 20th	Night	2 3 2 3 3 3 3 3 5% 6% 68%	4510
	21st to end	Night	1 1 2 2 2 2 2 3 4 82%	4517
June	1st to 10th	Night	2 2 1 3 3 4 4 4 6% 7% 63%	1800
	11th to 20th	Night	3 1 3 3 3 3 4 5% 6% 69%	1800
	21st to end	Night	5% 4 1 4 5% 5% 5% 5% 9% 10% 46%	1800
July	1st to 10th	Night	3 2 2 6% 5% 5% 6% 5% 9% 11% 47%	4100
	11th to 20th	Night	2 2 2 6% 5% 6% 7% 6% 9% 11% 43%	4100
	21st to end	Night	4 5% 2 7% 7% 6% 8% 6% 9% 11% 34%	4472
August	1st to 10th	Night	2 3 1 5% 5% 5% 7% 6% 9% 13% 46%	4282
	11th to 20th	Night	3 3 1 5% 6% 6% 7% 6% 9% 14% 40%	4483
	21st to end	Night	3 4 2 7% 6% 6% 7% 6% 8% 9% 41%	4993
September	1st to 10th	Night	5% 4 2 6% 5% 5% 7% 5% 6% 9% 48%	2000
	11th to 20th	Night	5% 4 1 5% 3 4 4 4 6% 9% 55%	2000
	21st to end	Night	4 2 1 4 3 3 4 3 5% 7% 65%	2255
October	1st to 10th	Night	2 2 1 2 2 2 3 2 4 5% 75%	3920
	11th to 20th	Night	3 3 1 4 2 2 3 2 3 4 72%	3898
	21st to end	Night	2 1 2 1 1 2 2 3 4 81%	4252
November	1st to 10th	Night	3 1 1 2 2 2 2 3 3 6% 75%	2460
	11th to 20th	Night	2 2 1 3 2 2 3 3 4 6% 72%	2520
	21st to end	Night	5% 3 1 4 3 3 3 3 5% 5% 65%	2628
December	1st to 10th	Night	3 3 1 3 2 2 2 2 4 5% 73%	4472
	11th to 20th	Night	2 2 1 4 3 3 4 3 5% 7% 67%	5046
	21st to end	Night	3 3 1 3 2 2 2 3 4 6% 71%	6611

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	23% 2 5% 15% 38% 17%	5321
	11th to 20th	Day	8% 2 3 13% 48% 27%	5340
	21st to end	Day	22% 2 4 15% 31% 25%	5844
February	1st to 10th	Day	16% 2 6% 15% 27% 34%	1950
	11th to 20th	Day	22% 2 6% 15% 31% 25%	2059
	21st to end	Day	16% 2 4 8% 31% 39%	1760
March	1st to 10th	Day	16% 2 4 5% 30% 43%	5064
	11th to 20th	Day	18% 4 4 13% 28% 33%	5110
	21st to end	Day	18% 2 6% 9% 31% 34%	5646
April	1st to 10th	Day	14% 2 5% 10% 31% 39%	2520
	11th to 20th	Day	13% 1 3 6% 27% 50%	2447
	21st to end	Day	10% 1 4 8% 28% 50%	2400
May	1st to 10th	Day	7% 1 2 10% 30% 50%	5440
	11th to 20th	Day	8% 2 5% 9% 24% 52%	5408
	21st to end	Day	6% 1 3 8% 13% 68%	6376
June	1st to 10th	Day	14% 2 7% 12% 27% 40%	2600
	11th to 20th	Day	11% 2 5% 6% 21% 56%	2600
	21st to end	Day	22% 5% 11% 13% 20% 29%	2600
July	1st to 10th	Day	22% 6% 11% 19% 23% 19%	5816
	11th to 20th	Day	17% 5% 16% 30% 25% 7%	5811
	21st to end	Day	30% 7% 16% 25% 16% 5%	6217
August	1st to 10th	Day	21% 6% 12% 31% 24% 6%	4022
	11th to 20th	Day	18% 5% 12% 20% 34% 10%	3882
	21st to end	Day	23% 7% 14% 27% 22% 6%	4311
September	1st to 10th	Day	28% 5% 11% 18% 22% 17%	2400
	11th to 20th	Day	22% 5% 8% 16% 29% 20%	2400
	21st to end	Day	14% 3 6% 19% 32% 25%	2140
October	1st to 10th	Day	11% 3 4 8% 27% 47%	3270
	11th to 20th	Day	16% 2 4 13% 30% 35%	3250
	21st to end	Day	8% 1 2 11% 34% 45%	3548
November	1st to 10th	Day	12% 3 6% 15% 35% 30%	2059
	11th to 20th	Day	16% 2 5% 17% 29% 31%	2100
	21st to end	Day	21% 2 6% 17% 32% 22%	1961
December	1st to 10th	Day	21% 3 4 20% 32% 19%	2934
	11th to 20th	Day	21% 3 3 14% 39% 20%	3414
	21st to end	Day	14% 2 6% 18% 39% 21%	4609
January	1st to 10th	Night	27% 2 4 14% 38% 14%	7605
	11th to 20th	Night	10% 2 3 12% 46% 27%	7650
	21st to end	Night	27% 2 4 13% 28% 25%	8370
February	1st to 10th	Night	17% 3 6% 16% 24% 35%	2667
	11th to 20th	Night	21% 2 7% 12% 31% 28%	2458
	21st to end	Night	16% 3 4 9% 29% 39%	2042
March	1st to 10th	Night	15% 2 4 5% 32% 42%	5050
	11th to 20th	Night	20% 3 6% 10% 30% 31%	5110
	21st to end	Night	20% 2 6% 10% 31% 31%	5569
April	1st to 10th	Night	15% 3 6% 9% 32% 36%	2100
	11th to 20th	Night	16% 2 6% 9% 23% 43%	2037
	21st to end	Night	10% 2 6% 10% 27% 45%	2000
May	1st to 10th	Night	12% 1 3 14% 19% 51%	4537
	11th to 20th	Night	17% 3 5% 9% 20% 47%	4511
	21st to end	Night	10% 2 4 6% 12% 67%	4517
June	1st to 10th	Night	18% 5% 5% 12% 21% 38%	1800
	11th to 20th	Night	14% 3 6% 7% 17% 52%	1800
	21st to end	Night	28% 7% 10% 15% 15% 25%	1800
July	1st to 10th	Night	28% 6% 15% 20% 18% 13%	4055
	11th to 20th	Night	30% 6% 16% 20% 21% 6%	4046
	21st to end	Night	39% 7% 17% 20% 10% 6%	4344
August	1st to 10th	Night	31% 7% 11% 28% 17% 5%	3111
	11th to 20th	Night	23% 8% 10% 17% 30% 11%	3243
	21st to end	Night	40% 8% 11% 20% 16% 5%	3597
September	1st to 10th	Night	31% 6% 11% 16% 19% 17%	2000
	11th to 20th	Night	25% 5% 9% 17% 22% 22%	2000
	21st to end	Night	19% 4 7% 15% 31% 24%	2255
October	1st to 10th	Night	13% 3 5% 8% 22% 48%	3920
	11th to 20th	Night	19% 2 4 11% 23% 42%	3898
	21st to end	Night	9% 1 2 8% 30% 49%	4252
November	1st to 10th	Night	12% 2 6% 13% 32% 35%	2460
	11th to 20th	Night	14% 2 4 15% 32% 32%	2520
	21st to end	Night	22% 3 6% 15% 32% 24%	2628
December	1st to 10th	Night	16% 3 3 20% 38% 20%	4472
	11th to 20th	Night	19% 2 4 13% 36% 26%	5046
	21st to end	Night	16% 2 4 15% 40% 22%	6611

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	10% 8% 25% 40% 15% 3	330
	11th to 20th	Day	7% 6% 22% 37% 21% 6%	330
	21st to end	Day	6% 8% 29% 33% 19% 6%	363
February	1st to 10th	Day	5% 9% 23% 37% 18% 8%	330
	11th to 20th	Day	15% 10% 25% 35% 14% 2	330
	21st to end	Day	10% 17% 29% 31% 11% 3	303
March	1st to 10th	Day	9% 17% 32% 29% 11% 1	540
	11th to 20th	Day	13% 14% 24% 28% 17% 4	540
	21st to end	Day	7% 21% 32% 25% 12% 3	594
April	1st to 10th	Day	8% 13% 32% 28% 14% 5%	540
	11th to 20th	Day	7% 21% 32% 26% 13% 2	517
	21st to end	Day	5% 18% 32% 28% 14% 3	500
May	1st to 10th	Day	3 14% 33% 30% 15% 5%	503
	11th to 20th	Day	4 9% 31% 30% 21% 5%	528
	21st to end	Day	1 8% 32% 35% 21% 3	573
June	1st to 10th	Day	4 6% 17% 35% 27% 11%	530
	11th to 20th	Day	3 5% 19% 33% 30% 10%	530
	21st to end	Day	4 2 12% 28% 32% 22%	530
July	1st to 10th	Day	3 1 6% 24% 36% 30%	526
	11th to 20th	Day	4 3 19% 41% 33%	524
	21st to end	Day	3 1 3 18% 36% 39%	575
August	1st to 10th	Day	3 2 13% 39% 42%	527
	11th to 20th	Day	3 2 7% 20% 42% 27%	517
	21st to end	Day	4 1 3 19% 37% 36%	583
September	1st to 10th	Day	6% 2 8% 24% 38% 22%	530
	11th to 20th	Day	3 1 9% 29% 39% 18%	530
	21st to end	Day	5% 3 11% 27% 36% 18%	400
October	1st to 10th	Day	3 3 15% 29% 30% 19%	330
	11th to 20th	Day	9% 4 16% 24% 35% 11%	330
	21st to end	Day	5% 5% 18% 27% 30% 15%	363
November	1st to 10th	Day	6% 4 23% 31% 28% 8%	330
	11th to 20th	Day	2 6% 16% 33% 34% 8%	330
	21st to end	Day	9% 7% 25% 38% 16% 5%	330
December	1st to 10th	Day	8% 7% 22% 38% 21% 5%	330
	11th to 20th	Day	4 8% 28% 36% 20% 5%	330
	21st to end	Day	9% 6% 25% 40% 17% 2	363
January	1st to 10th	Night	7% 4 24% 46% 16% 2	840
	11th to 20th	Night	4 3 29% 47% 17% 1	840
	21st to end	Night	6% 5% 28% 44% 15% 1	924
February	1st to 10th	Night	2 5% 29% 44% 18% 1	840
	11th to 20th	Night	7% 7% 35% 40% 11%	824
	21st to end	Night	4 8% 42% 37% 8% 1	692
March	1st to 10th	Night	7% 9% 32% 42% 9%	840
	11th to 20th	Night	5% 10% 28% 42% 14% 1	840
	21st to end	Night	3 9% 35% 39% 13%	908
April	1st to 10th	Night	3 9% 40% 37% 10%	630
	11th to 20th	Night	4 9% 40% 36% 10% 1	611
	21st to end	Night	2 10% 37% 41% 9% 1	600
May	1st to 10th	Night	4 6% 36% 46% 8%	600
	11th to 20th	Night	2 4 29% 50% 14% 1	591
	21st to end	Night	2 5% 30% 50% 12%	650
June	1st to 10th	Night	3 3 21% 50% 23% 1	600
	11th to 20th	Night	2 2 20% 55% 22%	600
	21st to end	Night	4 2 13% 46% 35% 2	600
July	1st to 10th	Night	4 1 8% 37% 47% 4	585
	11th to 20th	Night	4 1 4 29% 56% 6%	582
	21st to end	Night	4 1 4 26% 56% 9%	657
August	1st to 10th	Night	3 1 4 26% 55% 10%	597
	11th to 20th	Night	4 2 6% 25% 54% 10%	594
	21st to end	Night	4 5% 28% 54% 8%	660
September	1st to 10th	Night	6% 1 6% 34% 49% 4	600
	11th to 20th	Night	7% 1 6% 42% 43% 2	600
	21st to end	Night	5% 1 9% 47% 36% 2	725
October	1st to 10th	Night	5% 2 13% 49% 28% 2	800
	11th to 20th	Night	6% 2 17% 48% 26% 2	800
	21st to end	Night	3 3 17% 42% 30% 5%	880
November	1st to 10th	Night	4 2 16% 46% 29% 3	820
	11th to 20th	Night	3 3 20% 45% 27% 2	840
	21st to end	Night	6% 5% 24% 43% 20% 2	948
December	1st to 10th	Night	6% 5% 22% 45% 20% 1	1050
	11th to 20th	Night	5% 4 25% 49% 16% 1	906
	21st to end	Night	4 5% 28% 46% 16% 1	924

Page generated at 2026-04-14 00:44:28. Version ac07

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