Givhans Ferry State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Givhans Ferry 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	12% 6% 2 7% 5% 5% 5% 4 6% 8% 39%	127140
	Night	12% 6% 2 6% 4 4 4 4 6% 8% 44%	123890
Transparency	Day	40% 7% 12% 17% 16% 6%	130773
	Night	37% 7% 13% 18% 19% 7%	128326
Seeing	Day	14% 11% 26% 25% 17% 7%	17002
	Night	14% 9% 25% 31% 19% 3	27085

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% 4 1 5% 3 3 4 3 5% 6% 53%	4056
	11th to 20th	Day	14% 5% 2 6% 4 3 2 2 4 6% 52%	4060
	21st to end	Day	15% 8% 2 6% 4 3 3 3 5% 6% 44%	4466
February	1st to 10th	Day	16% 6% 3 5% 4 4 4 4 6% 7% 42%	1800
	11th to 20th	Day	19% 7% 2 5% 4 3 2 3 5% 6% 44%	1938
	21st to end	Day	14% 7% 2 7% 3 4 3 4 4 5% 47%	1775
March	1st to 10th	Day	21% 8% 3 6% 4 4 3 3 5% 5% 37%	4935
	11th to 20th	Day	9% 4 2 5% 4 3 4 3 5% 7% 54%	4980
	21st to end	Day	14% 6% 2 6% 4 4 4 3 4 5% 48%	5465
April	1st to 10th	Day	9% 5% 1 5% 4 4 4 4 6% 7% 51%	2200
	11th to 20th	Day	11% 4 2 6% 4 5% 4 3 5% 7% 49%	2374
	21st to end	Day	8% 4 1 4 4 5% 4 4 6% 8% 51%	2410
May	1st to 10th	Day	10% 6% 2 7% 5% 5% 6% 5% 7% 10% 37%	5862
	11th to 20th	Day	15% 6% 2 7% 5% 5% 5% 5% 7% 8% 34%	5861
	21st to end	Day	9% 5% 2 7% 5% 6% 5% 5% 7% 8% 41%	6433
June	1st to 10th	Day	11% 7% 2 8% 6% 8% 6% 5% 8% 9% 30%	2600
	11th to 20th	Day	8% 5% 2 6% 6% 6% 7% 6% 9% 10% 35%	2600
	21st to end	Day	6% 5% 3 7% 7% 7% 7% 7% 9% 10% 32%	2600
July	1st to 10th	Day	11% 8% 3 11% 7% 8% 8% 7% 8% 10% 19%	5900
	11th to 20th	Day	5% 4 2 8% 7% 8% 9% 8% 10% 14% 25%	5900
	21st to end	Day	6% 7% 3 9% 7% 8% 8% 6% 9% 12% 25%	6424
August	1st to 10th	Day	22% 7% 3 9% 6% 7% 7% 5% 8% 9% 18%	4234
	11th to 20th	Day	8% 6% 3 9% 7% 7% 7% 6% 8% 11% 28%	4094
	21st to end	Day	9% 7% 4 9% 7% 6% 6% 4 7% 10% 32%	4312
September	1st to 10th	Day	10% 6% 3 8% 6% 5% 6% 6% 8% 8% 35%	2245
	11th to 20th	Day	15% 7% 3 7% 5% 6% 6% 5% 6% 7% 35%	2200
	21st to end	Day	16% 6% 3 7% 5% 5% 5% 4 6% 7% 38%	2200
October	1st to 10th	Day	13% 6% 2 7% 5% 5% 4 4 5% 6% 43%	2056
	11th to 20th	Day	10% 4 2 5% 4 3 3 3 4 6% 56%	2000
	21st to end	Day	10% 5% 2 5% 3 3 4 3 5% 5% 56%	2200
November	1st to 10th	Day	11% 5% 1 5% 4 3 3 3 5% 6% 53%	2057
	11th to 20th	Day	13% 7% 2 5% 3 2 3 3 3 6% 51%	2091
	21st to end	Day	13% 6% 2 5% 3 3 3 3 4 7% 50%	1890
December	1st to 10th	Day	10% 4 2 6% 5% 4 4 4 5% 6% 52%	3020
	11th to 20th	Day	13% 6% 2 6% 3 2 4 3 5% 6% 48%	3436
	21st to end	Day	20% 9% 3 5% 3 3 3 3 4 6% 42%	4466
January	1st to 10th	Night	11% 6% 2 4 3 3 4 3 4 5% 56%	5889
	11th to 20th	Night	13% 7% 2 6% 4 4 4 4 6% 7% 44%	5900
	21st to end	Night	14% 8% 3 7% 4 3 4 3 4 6% 45%	6490
February	1st to 10th	Night	15% 7% 2 5% 4 4 4 4 5% 6% 44%	2600
	11th to 20th	Night	18% 7% 2 5% 4 4 4 3 5% 6% 43%	2344
	21st to end	Night	12% 7% 3 6% 4 4 4 3 6% 6% 45%	1854
March	1st to 10th	Night	19% 9% 3 7% 4 4 3 3 4 5% 38%	4918
	11th to 20th	Night	10% 5% 2 5% 3 3 3 3 6% 9% 52%	4980
	21st to end	Night	13% 5% 2 4 3 3 4 3 5% 7% 50%	5467
April	1st to 10th	Night	10% 5% 2 5% 4 5% 4 4 5% 7% 50%	2198
	11th to 20th	Night	11% 4 2 5% 3 3 3 3 6% 8% 52%	1975
	21st to end	Night	8% 4 1 5% 4 4 4 3 6% 7% 53%	2000
May	1st to 10th	Night	7% 6% 2 6% 4 4 5% 4 7% 9% 46%	4039
	11th to 20th	Night	15% 6% 2 5% 4 4 4 4 6% 10% 39%	4032
	21st to end	Night	10% 5% 2 6% 4 4 5% 4 6% 8% 45%	4421
June	1st to 10th	Night	9% 6% 3 7% 5% 5% 5% 5% 9% 11% 35%	1800
	11th to 20th	Night	7% 5% 2 5% 5% 5% 6% 5% 8% 11% 39%	1800
	21st to end	Night	6% 4 3 6% 6% 5% 6% 6% 10% 13% 37%	1800
July	1st to 10th	Night	10% 8% 3 9% 6% 6% 7% 5% 7% 10% 29%	4058
	11th to 20th	Night	5% 5% 3 7% 6% 6% 7% 6% 9% 14% 32%	4057
	21st to end	Night	7% 7% 3 9% 7% 7% 8% 6% 9% 10% 27%	4427
August	1st to 10th	Night	19% 8% 3 6% 4 5% 7% 5% 8% 12% 24%	2915
	11th to 20th	Night	8% 6% 2 7% 6% 6% 7% 5% 8% 11% 34%	2908
	21st to end	Night	7% 4 2 6% 5% 6% 5% 4 7% 10% 44%	3586
September	1st to 10th	Night	9% 5% 2 7% 6% 4 5% 4 7% 11% 40%	2150
	11th to 20th	Night	10% 6% 3 8% 6% 4 6% 5% 7% 7% 39%	2200
	21st to end	Night	16% 6% 2 6% 4 4 4 4 7% 8% 39%	2200
October	1st to 10th	Night	14% 5% 2 6% 3 4 4 3 5% 6% 48%	2342
	11th to 20th	Night	12% 4 1 3 3 3 3 3 5% 6% 58%	2400
	21st to end	Night	10% 6% 2 4 3 3 3 3 4 5% 56%	2640
November	1st to 10th	Night	11% 5% 2 5% 3 3 4 3 5% 5% 54%	2461
	11th to 20th	Night	14% 7% 2 5% 3 3 3 3 4 6% 52%	2525
	21st to end	Night	11% 5% 2 6% 4 5% 4 3 6% 7% 48%	2730
December	1st to 10th	Night	11% 6% 2 5% 3 3 3 3 4 5% 55%	4380
	11th to 20th	Night	16% 9% 3 6% 4 3 3 3 4 4 45%	4914
	21st to end	Night	18% 6% 2 6% 3 3 4 4 5% 6% 43%	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% 4 7% 16% 33% 9%	4057
	11th to 20th	Day	34% 3 5% 16% 31% 10%	4060
	21st to end	Day	41% 4 6% 19% 19% 12%	4466
February	1st to 10th	Day	40% 7% 8% 20% 20% 6%	1800
	11th to 20th	Day	42% 5% 7% 16% 22% 8%	1948
	21st to end	Day	39% 5% 9% 18% 19% 11%	1775
March	1st to 10th	Day	49% 5% 7% 11% 19% 10%	4935
	11th to 20th	Day	29% 4 9% 16% 23% 19%	4980
	21st to end	Day	39% 5% 8% 16% 21% 12%	5465
April	1st to 10th	Day	31% 6% 12% 21% 21% 9%	2200
	11th to 20th	Day	34% 5% 9% 21% 18% 12%	2374
	21st to end	Day	29% 6% 11% 28% 21% 5%	2410
May	1st to 10th	Day	39% 9% 16% 24% 10% 2	5897
	11th to 20th	Day	45% 7% 17% 19% 11% 1	5865
	21st to end	Day	37% 8% 14% 19% 20% 2	6447
June	1st to 10th	Day	47% 11% 15% 16% 11%	2600
	11th to 20th	Day	38% 12% 20% 21% 8% 1	2600
	21st to end	Day	40% 13% 21% 17% 8% 1	2600
July	1st to 10th	Day	54% 12% 17% 13% 3 1	5835
	11th to 20th	Day	43% 16% 30% 9% 2	5831
	21st to end	Day	46% 13% 18% 19% 4	6240
August	1st to 10th	Day	59% 10% 18% 10% 2	4221
	11th to 20th	Day	45% 12% 16% 19% 8%	4133
	21st to end	Day	45% 9% 13% 28% 5% 1	4312
September	1st to 10th	Day	43% 10% 15% 14% 14% 4	2245
	11th to 20th	Day	46% 9% 10% 18% 13% 3	2200
	21st to end	Day	45% 7% 12% 18% 14% 4	2200
October	1st to 10th	Day	42% 4 9% 11% 27% 7%	3342
	11th to 20th	Day	19% 3 6% 13% 32% 28%	3240
	21st to end	Day	26% 3 6% 16% 36% 13%	3538
November	1st to 10th	Day	31% 5% 10% 17% 25% 13%	2057
	11th to 20th	Day	36% 3 7% 17% 24% 12%	2091
	21st to end	Day	34% 4 9% 22% 23% 9%	1890
December	1st to 10th	Day	33% 4 9% 18% 23% 13%	3020
	11th to 20th	Day	37% 5% 9% 22% 22% 5%	3433
	21st to end	Day	44% 3 6% 22% 21% 3	4466
January	1st to 10th	Night	29% 5% 6% 15% 36% 9%	5889
	11th to 20th	Night	39% 4 6% 16% 28% 7%	5900
	21st to end	Night	41% 5% 7% 11% 25% 11%	6490
February	1st to 10th	Night	41% 5% 9% 19% 20% 8%	2600
	11th to 20th	Night	43% 5% 8% 14% 20% 10%	2345
	21st to end	Night	38% 6% 11% 18% 16% 12%	1854
March	1st to 10th	Night	48% 5% 7% 12% 19% 9%	4918
	11th to 20th	Night	29% 5% 9% 12% 27% 17%	4980
	21st to end	Night	33% 5% 11% 19% 20% 12%	5467
April	1st to 10th	Night	33% 6% 12% 20% 20% 9%	2198
	11th to 20th	Night	30% 6% 9% 23% 21% 11%	1975
	21st to end	Night	28% 7% 13% 26% 21% 5%	2000
May	1st to 10th	Night	32% 9% 20% 27% 10% 2	4066
	11th to 20th	Night	39% 8% 21% 20% 12% 1	4033
	21st to end	Night	35% 8% 15% 24% 17% 1	4429
June	1st to 10th	Night	37% 12% 21% 20% 10%	1800
	11th to 20th	Night	35% 11% 22% 24% 7% 1	1800
	21st to end	Night	33% 14% 25% 22% 5% 1	1800
July	1st to 10th	Night	47% 11% 23% 16% 3 1	4015
	11th to 20th	Night	38% 15% 35% 9% 3	4006
	21st to end	Night	45% 14% 19% 19% 3	4297
August	1st to 10th	Night	50% 13% 23% 12% 2	2904
	11th to 20th	Night	40% 12% 21% 20% 6%	2935
	21st to end	Night	34% 10% 16% 35% 5%	3586
September	1st to 10th	Night	37% 11% 18% 20% 10% 4	2150
	11th to 20th	Night	39% 11% 14% 20% 13% 2	2200
	21st to end	Night	42% 8% 15% 19% 14% 2	2200
October	1st to 10th	Night	37% 4 9% 18% 25% 6%	3836
	11th to 20th	Night	17% 3 6% 13% 25% 35%	3899
	21st to end	Night	26% 3 7% 19% 29% 16%	4252
November	1st to 10th	Night	32% 4 8% 16% 25% 14%	2461
	11th to 20th	Night	35% 4 7% 17% 25% 12%	2525
	21st to end	Night	36% 4 9% 17% 23% 10%	2730
December	1st to 10th	Night	33% 4 8% 14% 30% 11%	4380
	11th to 20th	Night	44% 4 9% 15% 20% 8%	4916
	21st to end	Night	41% 5% 7% 20% 23% 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	17% 25% 44% 11% 2 1	300
	11th to 20th	Day	18% 19% 39% 16% 6% 1	300
	21st to end	Day	27% 26% 36% 9% 2	330
February	1st to 10th	Day	20% 22% 40% 15% 3 1	300
	11th to 20th	Day	31% 23% 36% 8% 1	300
	21st to end	Day	19% 19% 43% 16% 3	374
March	1st to 10th	Day	23% 17% 32% 21% 6%	500
	11th to 20th	Day	15% 24% 36% 18% 6% 1	500
	21st to end	Day	17% 18% 39% 16% 8% 1	550
April	1st to 10th	Day	17% 19% 35% 19% 8% 1	500
	11th to 20th	Day	12% 16% 32% 21% 14% 5%	492
	21st to end	Day	8% 12% 31% 26% 16% 8%	500
May	1st to 10th	Day	9% 17% 33% 23% 13% 5%	503
	11th to 20th	Day	13% 7% 29% 25% 19% 7%	527
	21st to end	Day	10% 6% 23% 30% 19% 12%	573
June	1st to 10th	Day	12% 6% 22% 31% 21% 9%	530
	11th to 20th	Day	10% 5% 18% 28% 26% 13%	530
	21st to end	Day	7% 4 16% 32% 27% 14%	530
July	1st to 10th	Day	7% 3 10% 29% 33% 18%	525
	11th to 20th	Day	6% 2 7% 31% 34% 19%	524
	21st to end	Day	6% 3 12% 34% 32% 13%	576
August	1st to 10th	Day	16% 3 13% 26% 26% 16%	526
	11th to 20th	Day	10% 2 9% 29% 33% 17%	519
	21st to end	Day	13% 4 13% 28% 26% 15%	583
September	1st to 10th	Day	11% 4 17% 29% 27% 13%	530
	11th to 20th	Day	16% 4 16% 34% 21% 8%	530
	21st to end	Day	18% 2 21% 28% 22% 9%	530
October	1st to 10th	Day	16% 5% 27% 28% 15% 8%	530
	11th to 20th	Day	11% 7% 24% 33% 18% 7%	530
	21st to end	Day	15% 8% 26% 30% 17% 4	583
November	1st to 10th	Day	17% 10% 30% 24% 17% 2	535
	11th to 20th	Day	17% 15% 36% 21% 10% 2	531
	21st to end	Day	14% 17% 37% 25% 7%	330
December	1st to 10th	Day	21% 18% 35% 22% 4	330
	11th to 20th	Day	18% 17% 39% 17% 6% 2	321
	21st to end	Day	27% 18% 31% 17% 7% 1	330
January	1st to 10th	Night	15% 16% 35% 27% 7%	800
	11th to 20th	Night	17% 14% 32% 28% 8%	800
	21st to end	Night	19% 15% 39% 24% 3	880
February	1st to 10th	Night	18% 14% 33% 30% 5%	800
	11th to 20th	Night	20% 17% 33% 25% 4	783
	21st to end	Night	17% 14% 38% 25% 5%	660
March	1st to 10th	Night	15% 14% 36% 29% 7%	800
	11th to 20th	Night	15% 14% 38% 27% 7%	800
	21st to end	Night	14% 15% 35% 29% 8%	880
April	1st to 10th	Night	13% 15% 37% 28% 7% 1	800
	11th to 20th	Night	13% 10% 34% 28% 13% 1	791
	21st to end	Night	10% 10% 30% 36% 13%	800
May	1st to 10th	Night	6% 9% 30% 39% 16%	606
	11th to 20th	Night	11% 5% 26% 36% 19% 2	591
	21st to end	Night	11% 2 17% 37% 30% 4	650
June	1st to 10th	Night	11% 3 17% 42% 23% 4	600
	11th to 20th	Night	9% 3 11% 39% 30% 8%	600
	21st to end	Night	6% 2 16% 36% 34% 7%	600
July	1st to 10th	Night	8% 2 10% 39% 36% 6%	585
	11th to 20th	Night	9% 1 6% 33% 42% 9%	582
	21st to end	Night	5% 3 7% 38% 40% 7%	657
August	1st to 10th	Night	11% 4 6% 32% 39% 9%	597
	11th to 20th	Night	8% 3 8% 30% 40% 11%	614
	21st to end	Night	12% 3 12% 30% 33% 11%	880
September	1st to 10th	Night	8% 2 13% 32% 38% 7%	800
	11th to 20th	Night	12% 4 13% 35% 31% 5%	800
	21st to end	Night	19% 3 14% 32% 28% 5%	800
October	1st to 10th	Night	16% 4 20% 33% 22% 5%	800
	11th to 20th	Night	14% 5% 23% 33% 23% 3	800
	21st to end	Night	12% 8% 25% 31% 23% 2	880
November	1st to 10th	Night	13% 8% 25% 35% 17% 2	820
	11th to 20th	Night	16% 10% 29% 30% 14% 1	840
	21st to end	Night	13% 10% 32% 29% 16% 1	840
December	1st to 10th	Night	19% 10% 30% 30% 10%	840
	11th to 20th	Night	19% 10% 28% 29% 12% 1	829
	21st to end	Night	20% 13% 31% 27% 8%	880

Page generated at 2025-12-15 01:13:52. Version ac07

Copyright © 2025 Attilla Danko.