Droop Mountain Battlefield State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Droop Mountain Battlefield State Park clear sky chart from 2005-11-06 to 2025-08-05.

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% 7% 3 7% 5% 5% 5% 4 6% 7% 35%	125025
	Night	14% 7% 3 7% 5% 4 5% 4 6% 7% 38%	123020
Transparency	Day	44% 8% 12% 20% 13% 3	128643
	Night	43% 8% 13% 21% 13% 3	127471
Seeing	Day	23% 16% 24% 21% 12% 5%	15974
	Night	21% 14% 21% 28% 15% 2	26295

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% 8% 5% 4 4 3 4 5% 37%	4056
	11th to 20th	Day	11% 10% 6% 14% 6% 5% 4 3 4 4 34%	4060
	21st to end	Day	16% 9% 3 8% 4 3 3 3 5% 6% 41%	4466
February	1st to 10th	Day	14% 9% 4 8% 5% 4 5% 3 4 7% 36%	1800
	11th to 20th	Day	17% 8% 3 9% 6% 5% 5% 4 5% 6% 32%	1795
	21st to end	Day	18% 10% 3 8% 4 4 4 4 5% 5% 35%	1701
March	1st to 10th	Day	17% 7% 4 7% 4 5% 5% 4 6% 6% 35%	4935
	11th to 20th	Day	13% 7% 3 6% 3 3 4 3 5% 8% 46%	4980
	21st to end	Day	13% 9% 3 7% 5% 5% 5% 4 5% 7% 36%	5465
April	1st to 10th	Day	13% 9% 3 8% 5% 4 4 3 6% 6% 39%	2270
	11th to 20th	Day	13% 7% 3 7% 4 4 6% 3 5% 6% 41%	2374
	21st to end	Day	18% 8% 3 7% 5% 5% 5% 4 5% 7% 35%	2583
May	1st to 10th	Day	15% 7% 3 9% 6% 7% 6% 5% 8% 8% 26%	5862
	11th to 20th	Day	21% 8% 3 7% 6% 5% 5% 4 7% 8% 27%	5861
	21st to end	Day	15% 6% 2 8% 6% 7% 6% 5% 6% 8% 31%	6433
June	1st to 10th	Day	13% 6% 2 6% 5% 5% 6% 5% 6% 9% 37%	2600
	11th to 20th	Day	11% 5% 2 8% 6% 6% 7% 5% 7% 9% 34%	2600
	21st to end	Day	10% 6% 2 6% 5% 6% 6% 5% 7% 9% 37%	2600
July	1st to 10th	Day	8% 5% 2 7% 6% 5% 6% 6% 7% 9% 40%	5900
	11th to 20th	Day	8% 5% 2 7% 6% 7% 8% 6% 9% 11% 30%	5900
	21st to end	Day	11% 8% 3 9% 7% 7% 6% 6% 8% 9% 27%	6424
August	1st to 10th	Day	13% 6% 2 8% 5% 6% 7% 5% 8% 10% 28%	4156
	11th to 20th	Day	10% 5% 2 8% 7% 6% 8% 5% 7% 8% 32%	4044
	21st to end	Day	7% 5% 2 6% 5% 5% 6% 4 7% 10% 44%	4258
September	1st to 10th	Day	14% 5% 2 7% 4 4 5% 5% 6% 8% 41%	2236
	11th to 20th	Day	14% 6% 3 6% 5% 5% 5% 4 6% 8% 39%	2090
	21st to end	Day	24% 6% 2 6% 4 4 5% 3 6% 6% 34%	2090
October	1st to 10th	Day	17% 5% 2 6% 4 4 4 2 5% 6% 45%	1919
	11th to 20th	Day	16% 7% 3 6% 4 4 3 3 4 5% 45%	1900
	21st to end	Day	15% 8% 2 6% 4 3 4 2 4 6% 45%	2090
November	1st to 10th	Day	11% 7% 3 5% 4 4 3 3 5% 6% 49%	1947
	11th to 20th	Day	14% 7% 2 7% 5% 5% 4 4 6% 6% 41%	1800
	21st to end	Day	13% 7% 3 6% 5% 4 5% 4 5% 6% 41%	1682
December	1st to 10th	Day	13% 10% 4 7% 4 4 4 3 5% 5% 40%	2600
	11th to 20th	Day	20% 11% 3 6% 4 4 3 4 4 6% 36%	3082
	21st to end	Day	20% 11% 3 8% 5% 4 4 3 6% 7% 28%	4466
January	1st to 10th	Night	11% 10% 6% 11% 5% 6% 6% 4 6% 6% 31%	5889
	11th to 20th	Night	12% 9% 4 11% 7% 4 4 3 4 4 38%	5900
	21st to end	Night	17% 8% 3 7% 4 4 3 3 4 5% 42%	6490
February	1st to 10th	Night	13% 8% 3 10% 5% 4 5% 5% 6% 8% 35%	2600
	11th to 20th	Night	18% 7% 2 9% 7% 5% 5% 4 6% 6% 31%	2488
	21st to end	Night	16% 8% 3 9% 5% 3 5% 5% 6% 7% 35%	1927
March	1st to 10th	Night	18% 10% 4 7% 4 4 4 4 5% 5% 37%	4918
	11th to 20th	Night	10% 4 3 7% 4 4 4 3 5% 8% 47%	4980
	21st to end	Night	14% 7% 3 5% 5% 4 5% 4 7% 7% 39%	5467
April	1st to 10th	Night	14% 9% 2 7% 6% 4 4 4 5% 7% 37%	2130
	11th to 20th	Night	12% 6% 3 6% 4 5% 4 4 6% 9% 40%	1975
	21st to end	Night	14% 7% 2 6% 4 4 5% 4 6% 8% 41%	1834
May	1st to 10th	Night	18% 9% 3 7% 5% 4 5% 4 6% 8% 31%	4033
	11th to 20th	Night	22% 10% 2 7% 5% 4 4 3 6% 7% 29%	4032
	21st to end	Night	17% 7% 2 7% 6% 5% 5% 4 7% 8% 31%	4421
June	1st to 10th	Night	9% 6% 2 6% 4 5% 4 5% 7% 10% 43%	1800
	11th to 20th	Night	12% 6% 2 6% 4 4 4 4 7% 9% 43%	1800
	21st to end	Night	9% 5% 1 5% 4 4 4 5% 7% 10% 45%	1800
July	1st to 10th	Night	9% 5% 2 7% 4 4 5% 5% 6% 9% 42%	4058
	11th to 20th	Night	10% 7% 3 8% 6% 5% 5% 5% 6% 10% 36%	4057
	21st to end	Night	10% 8% 3 9% 5% 6% 6% 4 7% 10% 31%	4427
August	1st to 10th	Night	14% 7% 2 7% 5% 5% 5% 5% 6% 8% 36%	2861
	11th to 20th	Night	12% 5% 2 7% 6% 6% 6% 4 7% 8% 36%	2785
	21st to end	Night	8% 5% 2 5% 4 4 4 3 6% 8% 52%	3364
September	1st to 10th	Night	13% 5% 2 6% 4 4 5% 4 6% 7% 46%	1940
	11th to 20th	Night	15% 5% 2 5% 3 3 4 4 4 7% 46%	2090
	21st to end	Night	21% 7% 2 5% 4 4 4 4 5% 5% 39%	2090
October	1st to 10th	Night	15% 6% 2 5% 4 5% 4 3 5% 6% 47%	2259
	11th to 20th	Night	13% 8% 2 6% 5% 4 4 3 4 6% 45%	2280
	21st to end	Night	14% 6% 1 6% 4 4 5% 3 6% 6% 45%	2508
November	1st to 10th	Night	11% 7% 3 6% 4 3 4 4 5% 7% 45%	2346
	11th to 20th	Night	14% 6% 3 6% 3 5% 5% 5% 7% 7% 40%	2600
	21st to end	Night	13% 7% 3 7% 4 5% 5% 4 6% 7% 39%	2711
December	1st to 10th	Night	12% 7% 4 9% 5% 4 5% 4 6% 7% 39%	4580
	11th to 20th	Night	19% 9% 4 8% 6% 4 5% 3 4 5% 33%	5090
	21st to end	Night	18% 7% 5% 7% 5% 5% 6% 4 7% 7% 29%	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	48% 4 7% 19% 19% 2	4057
	11th to 20th	Day	51% 5% 9% 13% 14% 7%	4060
	21st to end	Day	46% 4 11% 23% 14% 3	4466
February	1st to 10th	Day	49% 5% 10% 21% 12% 2	1800
	11th to 20th	Day	53% 5% 10% 18% 12% 2	1804
	21st to end	Day	50% 7% 9% 17% 13% 4	1701
March	1st to 10th	Day	45% 8% 10% 20% 12% 6%	4935
	11th to 20th	Day	36% 5% 10% 22% 21% 6%	4980
	21st to end	Day	47% 6% 9% 18% 16% 3	5465
April	1st to 10th	Day	46% 6% 10% 20% 14% 4	2270
	11th to 20th	Day	43% 6% 10% 21% 16% 3	2374
	21st to end	Day	48% 6% 12% 20% 11% 2	2583
May	1st to 10th	Day	50% 11% 12% 17% 8% 2	5897
	11th to 20th	Day	52% 9% 12% 18% 8% 1	5865
	21st to end	Day	44% 11% 14% 18% 9% 3	6447
June	1st to 10th	Day	42% 10% 13% 21% 14%	2600
	11th to 20th	Day	45% 9% 14% 17% 14%	2600
	21st to end	Day	40% 11% 14% 22% 11% 2	2600
July	1st to 10th	Day	37% 12% 16% 21% 10% 4	5835
	11th to 20th	Day	41% 15% 16% 20% 7%	5831
	21st to end	Day	47% 12% 14% 19% 8%	6240
August	1st to 10th	Day	45% 12% 17% 18% 7%	4143
	11th to 20th	Day	43% 12% 14% 20% 11%	4083
	21st to end	Day	33% 10% 16% 27% 11% 1	4258
September	1st to 10th	Day	40% 8% 11% 19% 17% 4	2236
	11th to 20th	Day	43% 7% 9% 22% 18% 2	2090
	21st to end	Day	50% 7% 10% 17% 15% 2	2090
October	1st to 10th	Day	28% 7% 11% 20% 26% 8%	3192
	11th to 20th	Day	30% 6% 11% 24% 14% 15%	3140
	21st to end	Day	28% 4 10% 31% 14% 12%	3428
November	1st to 10th	Day	36% 6% 11% 22% 21% 4	1947
	11th to 20th	Day	42% 5% 11% 18% 19% 4	1800
	21st to end	Day	43% 5% 15% 20% 15% 2	1682
December	1st to 10th	Day	44% 7% 9% 20% 18% 2	2600
	11th to 20th	Day	51% 4 11% 18% 15% 1	3078
	21st to end	Day	55% 6% 11% 18% 9% 1	4466
January	1st to 10th	Night	49% 7% 10% 17% 14% 3	5889
	11th to 20th	Night	47% 6% 9% 18% 14% 6%	5900
	21st to end	Night	45% 4 12% 23% 14% 2	6490
February	1st to 10th	Night	46% 7% 15% 19% 12% 1	2600
	11th to 20th	Night	53% 5% 12% 16% 11% 2	2490
	21st to end	Night	48% 7% 13% 20% 9% 4	1927
March	1st to 10th	Night	45% 8% 8% 19% 15% 5%	4918
	11th to 20th	Night	35% 5% 10% 26% 20% 4	4980
	21st to end	Night	41% 8% 12% 19% 15% 3	5467
April	1st to 10th	Night	47% 7% 12% 18% 13% 2	2130
	11th to 20th	Night	40% 7% 14% 20% 14% 4	1975
	21st to end	Night	41% 7% 15% 25% 12% 1	1834
May	1st to 10th	Night	49% 10% 14% 17% 8% 1	4060
	11th to 20th	Night	53% 10% 14% 17% 6%	4033
	21st to end	Night	47% 13% 16% 18% 4 3	4429
June	1st to 10th	Night	35% 12% 16% 22% 14%	1800
	11th to 20th	Night	37% 10% 19% 22% 11% 1	1800
	21st to end	Night	31% 13% 18% 25% 12% 1	1800
July	1st to 10th	Night	37% 12% 17% 23% 10% 2	4015
	11th to 20th	Night	42% 13% 17% 22% 6% 1	4006
	21st to end	Night	44% 14% 15% 19% 8%	4297
August	1st to 10th	Night	43% 11% 17% 23% 5%	2850
	11th to 20th	Night	40% 12% 16% 21% 11% 1	2812
	21st to end	Night	29% 9% 16% 32% 13% 1	3364
September	1st to 10th	Night	37% 8% 15% 19% 17% 4	1940
	11th to 20th	Night	37% 7% 11% 24% 19% 2	2090
	21st to end	Night	46% 8% 11% 22% 13% 1	2090
October	1st to 10th	Night	33% 6% 9% 24% 24% 4	3766
	11th to 20th	Night	31% 9% 10% 19% 19% 12%	3779
	21st to end	Night	26% 4 12% 28% 19% 11%	4120
November	1st to 10th	Night	39% 6% 12% 19% 19% 5%	2346
	11th to 20th	Night	41% 6% 12% 20% 17% 4	2600
	21st to end	Night	44% 6% 13% 20% 14% 3	2711
December	1st to 10th	Night	41% 7% 11% 24% 15% 1	4580
	11th to 20th	Night	54% 5% 13% 17% 11% 1	5093
	21st to end	Night	51% 8% 13% 19% 9%	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	40% 28% 21% 8% 3 1	300
	11th to 20th	Day	40% 26% 25% 8% 1	300
	21st to end	Day	40% 24% 24% 9% 3	330
February	1st to 10th	Day	35% 27% 25% 10% 2	300
	11th to 20th	Day	50% 24% 19% 7% 1	300
	21st to end	Day	39% 26% 25% 9% 1	300
March	1st to 10th	Day	33% 25% 21% 16% 4 1	500
	11th to 20th	Day	31% 26% 23% 15% 4 1	500
	21st to end	Day	27% 26% 26% 15% 5%	550
April	1st to 10th	Day	30% 26% 22% 14% 7% 1	500
	11th to 20th	Day	22% 22% 29% 17% 8% 2	492
	21st to end	Day	27% 19% 28% 14% 9% 2	500
May	1st to 10th	Day	27% 19% 30% 13% 9% 3	503
	11th to 20th	Day	24% 15% 28% 18% 11% 4	527
	21st to end	Day	20% 12% 22% 25% 14% 7%	573
June	1st to 10th	Day	15% 12% 28% 23% 14% 7%	530
	11th to 20th	Day	11% 12% 29% 26% 14% 7%	530
	21st to end	Day	10% 12% 31% 25% 15% 8%	530
July	1st to 10th	Day	13% 7% 21% 26% 20% 13%	525
	11th to 20th	Day	5% 6% 25% 34% 18% 11%	524
	21st to end	Day	13% 6% 25% 29% 17% 10%	576
August	1st to 10th	Day	18% 6% 22% 26% 18% 10%	502
	11th to 20th	Day	14% 8% 20% 27% 19% 12%	479
	21st to end	Day	10% 5% 21% 27% 22% 15%	539
September	1st to 10th	Day	14% 7% 20% 27% 20% 12%	490
	11th to 20th	Day	16% 5% 17% 30% 24% 9%	490
	21st to end	Day	24% 14% 21% 23% 14% 4	490
October	1st to 10th	Day	19% 9% 24% 26% 18% 4	490
	11th to 20th	Day	22% 14% 24% 24% 13% 3	490
	21st to end	Day	25% 16% 24% 22% 12% 2	539
November	1st to 10th	Day	19% 16% 28% 24% 11% 2	485
	11th to 20th	Day	34% 16% 28% 17% 5%	300
	21st to end	Day	30% 20% 30% 15% 4 1	240
December	1st to 10th	Day	34% 26% 24% 11% 4 2	200
	11th to 20th	Day	31% 24% 23% 17% 5%	220
	21st to end	Day	32% 24% 22% 16% 4 1	330
January	1st to 10th	Night	31% 25% 25% 16% 3	800
	11th to 20th	Night	29% 21% 28% 19% 3	800
	21st to end	Night	28% 22% 29% 19% 1	880
February	1st to 10th	Night	26% 20% 28% 24% 3	800
	11th to 20th	Night	30% 27% 27% 15% 1	783
	21st to end	Night	28% 22% 30% 19% 1	660
March	1st to 10th	Night	24% 22% 28% 23% 3	800
	11th to 20th	Night	27% 21% 25% 21% 6%	800
	21st to end	Night	23% 20% 29% 22% 6%	880
April	1st to 10th	Night	23% 21% 27% 24% 5%	800
	11th to 20th	Night	19% 16% 25% 28% 11% 1	791
	21st to end	Night	20% 13% 25% 33% 8% 1	634
May	1st to 10th	Night	20% 12% 24% 31% 12% 1	600
	11th to 20th	Night	23% 10% 20% 33% 14%	591
	21st to end	Night	17% 6% 16% 31% 27% 3	650
June	1st to 10th	Night	10% 6% 17% 38% 26% 2	600
	11th to 20th	Night	13% 6% 14% 36% 29% 2	600
	21st to end	Night	9% 4 16% 39% 29% 3	600
July	1st to 10th	Night	11% 3 10% 37% 33% 5%	585
	11th to 20th	Night	7% 3 10% 35% 39% 6%	582
	21st to end	Night	7% 6% 10% 37% 36% 4	657
August	1st to 10th	Night	16% 3 9% 37% 32% 3	579
	11th to 20th	Night	13% 4 9% 36% 34% 4	564
	21st to end	Night	13% 3 9% 36% 34% 6%	763
September	1st to 10th	Night	14% 4 11% 36% 29% 6%	760
	11th to 20th	Night	17% 6% 11% 32% 30% 4	760
	21st to end	Night	24% 7% 16% 29% 22% 2	760
October	1st to 10th	Night	18% 9% 16% 31% 23% 3	760
	11th to 20th	Night	18% 16% 20% 28% 16% 1	760
	21st to end	Night	20% 14% 20% 32% 13% 1	836
November	1st to 10th	Night	17% 12% 23% 34% 13% 1	780
	11th to 20th	Night	25% 13% 22% 30% 9% 1	800
	21st to end	Night	22% 17% 24% 30% 6% 1	800
December	1st to 10th	Night	26% 22% 27% 20% 5%	800
	11th to 20th	Night	23% 20% 27% 26% 4	800
	21st to end	Night	28% 14% 26% 27% 4	880

Page generated at 2025-08-02 01:32:22. Version ac07

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