Bad Creek Hydroelectric Dam
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bad Creek Hydroelectric Dam clear sky chart from 2005-11-06 to 2025-07-21.

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	15% 5% 2 6% 4 4 5% 4 6% 7% 42%	120296
	Night	16% 5% 2 5% 4 4 4 3 5% 7% 46%	118835
Transparency	Day	24% 42% 7% 11% 11% 5%	124062
	Night	23% 41% 7% 11% 13% 6%	123193
Seeing	Day	19% 13% 25% 23% 14% 7%	15930
	Night	18% 11% 22% 27% 18% 4	25981

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 2 2 2 2 4 5% 58%	4056
	11th to 20th	Day	12% 4 2 5% 3 3 2 2 2 3 62%	4060
	21st to end	Day	21% 4 2 5% 4 3 3 3 4 5% 48%	4466
February	1st to 10th	Day	16% 6% 2 6% 4 3 3 3 5% 6% 45%	1940
	11th to 20th	Day	21% 5% 2 5% 4 3 4 3 4 5% 43%	1948
	21st to end	Day	20% 6% 2 6% 4 4 4 3 4 5% 43%	1650
March	1st to 10th	Day	23% 6% 2 5% 3 4 3 3 5% 6% 42%	4788
	11th to 20th	Day	14% 4 2 4 3 3 3 2 3 6% 56%	4980
	21st to end	Day	20% 5% 2 5% 3 3 4 3 5% 5% 47%	5465
April	1st to 10th	Day	14% 5% 1 4 5% 3 5% 5% 6% 9% 45%	2200
	11th to 20th	Day	14% 5% 1 6% 4 4 4 3 6% 7% 45%	2387
	21st to end	Day	14% 4 2 5% 4 4 4 3 6% 7% 48%	2600
May	1st to 10th	Day	15% 7% 3 7% 5% 5% 5% 4 6% 8% 35%	5862
	11th to 20th	Day	21% 7% 2 6% 5% 6% 6% 5% 6% 7% 29%	5861
	21st to end	Day	14% 5% 2 6% 5% 5% 5% 4 6% 8% 41%	6433
June	1st to 10th	Day	13% 6% 2 6% 5% 6% 6% 6% 8% 10% 32%	2600
	11th to 20th	Day	7% 5% 2 5% 6% 6% 7% 6% 9% 10% 36%	2600
	21st to end	Day	8% 5% 2 5% 6% 7% 7% 6% 8% 11% 36%	2600
July	1st to 10th	Day	8% 4 2 8% 6% 7% 8% 6% 9% 11% 31%	4250
	11th to 20th	Day	9% 5% 2 7% 7% 7% 8% 5% 8% 10% 31%	4250
	21st to end	Day	12% 9% 4 11% 9% 8% 8% 6% 7% 7% 19%	4466
August	1st to 10th	Day	12% 7% 2 7% 5% 6% 7% 6% 8% 11% 29%	4104
	11th to 20th	Day	9% 5% 2 6% 5% 5% 7% 5% 8% 11% 36%	4044
	21st to end	Day	8% 4 2 6% 4 4 6% 4 7% 8% 47%	4122
September	1st to 10th	Day	12% 6% 2 7% 4 6% 6% 5% 8% 8% 37%	2090
	11th to 20th	Day	17% 7% 2 6% 6% 4 5% 5% 7% 8% 34%	2090
	21st to end	Day	19% 5% 2 7% 4 4 4 4 5% 6% 41%	2090
October	1st to 10th	Day	16% 4 1 4 3 3 3 2 4 6% 52%	2087
	11th to 20th	Day	13% 4 1 4 2 3 3 3 4 5% 58%	1900
	21st to end	Day	15% 4 1 3 2 3 3 2 4 5% 57%	2090
November	1st to 10th	Day	14% 5% 2 3 3 3 3 2 4 5% 56%	1848
	11th to 20th	Day	15% 5% 1 4 2 2 3 3 5% 6% 55%	1800
	21st to end	Day	16% 4 1 4 2 3 4 3 4 7% 52%	1800
December	1st to 10th	Day	17% 5% 2 4 3 3 3 3 4 5% 52%	2930
	11th to 20th	Day	18% 5% 2 5% 4 4 5% 4 5% 5% 45%	3373
	21st to end	Day	24% 4 1 3 2 3 2 2 4 6% 48%	4466
January	1st to 10th	Night	16% 4 1 3 2 3 3 2 4 4 59%	5889
	11th to 20th	Night	13% 5% 2 5% 3 2 3 2 3 5% 56%	5900
	21st to end	Night	19% 4 1 4 3 3 3 2 4 6% 51%	6490
February	1st to 10th	Night	15% 5% 2 4 3 4 3 3 5% 6% 49%	2455
	11th to 20th	Night	22% 5% 2 4 4 3 3 3 5% 4 45%	2338
	21st to end	Night	20% 5% 2 5% 3 4 3 3 4 7% 43%	1980
March	1st to 10th	Night	22% 6% 2 5% 3 3 4 3 4 6% 43%	5063
	11th to 20th	Night	12% 4 1 3 3 3 4 3 5% 7% 56%	4980
	21st to end	Night	19% 4 1 5% 4 3 3 3 4 6% 46%	5467
April	1st to 10th	Night	15% 5% 2 4 3 3 3 4 4 6% 51%	2200
	11th to 20th	Night	15% 5% 1 4 3 3 2 2 5% 7% 53%	1977
	21st to end	Night	14% 4 2 4 3 3 4 3 5% 7% 51%	1800
May	1st to 10th	Night	15% 7% 2 7% 5% 4 5% 5% 6% 8% 37%	4033
	11th to 20th	Night	25% 6% 2 5% 4 4 4 4 5% 7% 33%	4032
	21st to end	Night	16% 5% 2 4 3 4 4 4 6% 9% 43%	4421
June	1st to 10th	Night	11% 6% 3 6% 4 5% 6% 5% 9% 11% 34%	1800
	11th to 20th	Night	10% 6% 2 5% 4 5% 5% 3 7% 10% 42%	1800
	21st to end	Night	9% 5% 2 5% 4 5% 5% 6% 9% 10% 42%	1800
July	1st to 10th	Night	12% 8% 3 7% 6% 6% 7% 5% 8% 9% 29%	2930
	11th to 20th	Night	8% 6% 2 7% 5% 6% 6% 6% 8% 12% 33%	2930
	21st to end	Night	15% 9% 4 9% 6% 6% 6% 6% 8% 9% 24%	3087
August	1st to 10th	Night	12% 7% 3 7% 5% 6% 5% 5% 7% 11% 32%	2825
	11th to 20th	Night	15% 8% 3 8% 5% 5% 5% 4 6% 9% 32%	2785
	21st to end	Night	9% 6% 2 5% 4 4 5% 4 6% 10% 44%	3497
September	1st to 10th	Night	14% 5% 2 6% 5% 4 5% 4 7% 8% 39%	2090
	11th to 20th	Night	19% 7% 3 6% 4 4 4 4 6% 7% 35%	2090
	21st to end	Night	19% 6% 1 5% 4 4 4 3 4 6% 44%	2090
October	1st to 10th	Night	17% 5% 1 4 3 4 3 2 4 5% 51%	2090
	11th to 20th	Night	15% 5% 2 4 3 3 2 3 3 5% 54%	2280
	21st to end	Night	16% 4 1 3 3 2 3 2 3 4 58%	2508
November	1st to 10th	Night	17% 4 2 5% 2 2 3 2 4 5% 54%	2446
	11th to 20th	Night	17% 5% 1 3 3 2 3 3 4 5% 53%	2600
	21st to end	Night	17% 4 2 4 3 4 4 4 5% 5% 50%	2600
December	1st to 10th	Night	16% 5% 2 5% 3 3 3 3 4 4 53%	4250
	11th to 20th	Night	20% 5% 2 5% 3 4 4 3 4 5% 46%	4822
	21st to end	Night	24% 4 1 3 3 3 3 3 4 6% 45%	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	22% 27% 2 12% 28% 10%	4057
	11th to 20th	Day	20% 26% 2 9% 30% 13%	4060
	21st to end	Day	28% 30% 4 11% 17% 11%	4466
February	1st to 10th	Day	15% 63% 3 8% 9% 2	1940
	11th to 20th	Day	19% 62% 3 6% 8% 3	1958
	21st to end	Day	19% 62% 1 4 10% 4	1650
March	1st to 10th	Day	35% 30% 4 9% 11% 11%	4788
	11th to 20th	Day	20% 29% 3 9% 21% 18%	4980
	21st to end	Day	28% 29% 4 20% 14% 5%	5465
April	1st to 10th	Day	16% 64% 5% 6% 7% 2	2200
	11th to 20th	Day	17% 64% 4 7% 5% 3	2387
	21st to end	Day	15% 63% 6% 9% 6% 1	2600
May	1st to 10th	Day	34% 34% 11% 14% 7% 1	5897
	11th to 20th	Day	39% 34% 9% 12% 6%	5865
	21st to end	Day	29% 32% 10% 13% 14% 2	6447
June	1st to 10th	Day	18% 66% 6% 7% 2 1	2600
	11th to 20th	Day	15% 67% 9% 6% 4	2600
	21st to end	Day	15% 64% 9% 8% 3	2600
July	1st to 10th	Day	24% 44% 15% 14% 3	4185
	11th to 20th	Day	28% 42% 19% 10% 1	4181
	21st to end	Day	45% 42% 7% 4 2	4324
August	1st to 10th	Day	29% 43% 13% 13% 2	4091
	11th to 20th	Day	20% 44% 19% 7% 7% 3	4083
	21st to end	Day	15% 41% 10% 23% 11%	4122
September	1st to 10th	Day	17% 63% 5% 8% 7% 1	2090
	11th to 20th	Day	19% 63% 5% 6% 6%	2090
	21st to end	Day	18% 62% 7% 9% 4	2090
October	1st to 10th	Day	15% 38% 5% 12% 22% 7%	3464
	11th to 20th	Day	9% 38% 3 8% 19% 24%	3140
	21st to end	Day	17% 39% 4 15% 14% 12%	3428
November	1st to 10th	Day	18% 57% 3 9% 9% 4	1848
	11th to 20th	Day	14% 57% 3 9% 13% 5%	1800
	21st to end	Day	13% 58% 4 9% 14% 3	1800
December	1st to 10th	Day	21% 36% 3 10% 19% 11%	2930
	11th to 20th	Day	28% 33% 5% 10% 15% 9%	3370
	21st to end	Day	28% 27% 7% 21% 15% 2	4466
January	1st to 10th	Night	21% 27% 3 11% 25% 13%	5889
	11th to 20th	Night	21% 28% 3 8% 26% 14%	5900
	21st to end	Night	25% 29% 4 10% 20% 11%	6490
February	1st to 10th	Night	14% 62% 5% 10% 7% 2	2455
	11th to 20th	Night	19% 61% 3 6% 8% 3	2339
	21st to end	Night	17% 62% 2 6% 8% 5%	1980
March	1st to 10th	Night	32% 32% 5% 9% 17% 5%	5063
	11th to 20th	Night	18% 29% 4 12% 20% 17%	4980
	21st to end	Night	28% 29% 5% 17% 12% 8%	5467
April	1st to 10th	Night	16% 62% 4 6% 10% 2	2200
	11th to 20th	Night	16% 63% 4 8% 7% 3	1977
	21st to end	Night	14% 63% 6% 10% 7% 1	1800
May	1st to 10th	Night	33% 33% 10% 17% 6% 1	4060
	11th to 20th	Night	38% 32% 12% 12% 6%	4033
	21st to end	Night	25% 33% 12% 19% 10% 1	4429
June	1st to 10th	Night	17% 64% 7% 8% 3 1	1800
	11th to 20th	Night	15% 65% 9% 8% 4	1800
	21st to end	Night	13% 64% 9% 10% 5%	1800
July	1st to 10th	Night	29% 43% 14% 12% 2	2885
	11th to 20th	Night	24% 43% 19% 13% 1	2876
	21st to end	Night	40% 42% 10% 6% 2	2988
August	1st to 10th	Night	29% 42% 17% 10% 2	2814
	11th to 20th	Night	29% 43% 11% 9% 7%	2812
	21st to end	Night	15% 40% 12% 24% 8% 1	3497
September	1st to 10th	Night	16% 63% 6% 8% 6% 1	2090
	11th to 20th	Night	19% 63% 5% 6% 5% 1	2090
	21st to end	Night	19% 61% 5% 9% 5% 1	2090
October	1st to 10th	Night	16% 41% 8% 9% 20% 6%	3480
	11th to 20th	Night	8% 37% 3 9% 21% 22%	3779
	21st to end	Night	19% 37% 3 11% 17% 12%	4120
November	1st to 10th	Night	20% 56% 4 8% 8% 4	2446
	11th to 20th	Night	15% 58% 2 8% 11% 6%	2600
	21st to end	Night	14% 58% 3 8% 12% 4	2600
December	1st to 10th	Night	21% 37% 3 12% 18% 9%	4250
	11th to 20th	Night	29% 33% 4 11% 16% 7%	4824
	21st to end	Night	31% 28% 7% 16% 15% 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	26% 27% 34% 12% 1	300
	11th to 20th	Day	29% 27% 28% 14% 1	300
	21st to end	Day	30% 28% 32% 7% 2	330
February	1st to 10th	Day	23% 27% 39% 10% 2	300
	11th to 20th	Day	38% 29% 27% 6%	300
	21st to end	Day	35% 32% 26% 6% 1	249
March	1st to 10th	Day	29% 21% 29% 14% 6%	426
	11th to 20th	Day	25% 24% 30% 16% 3 1	500
	21st to end	Day	27% 22% 29% 16% 5% 1	550
April	1st to 10th	Day	25% 19% 29% 19% 7% 1	500
	11th to 20th	Day	17% 23% 29% 21% 10% 1	492
	21st to end	Day	19% 16% 28% 22% 11% 4	500
May	1st to 10th	Day	16% 20% 32% 19% 8% 5%	503
	11th to 20th	Day	22% 10% 23% 25% 13% 7%	527
	21st to end	Day	21% 9% 20% 26% 14% 11%	573
June	1st to 10th	Day	14% 8% 22% 30% 16% 10%	530
	11th to 20th	Day	12% 5% 23% 25% 22% 13%	530
	21st to end	Day	11% 4 22% 32% 18% 12%	530
July	1st to 10th	Day	8% 5% 14% 29% 26% 17%	525
	11th to 20th	Day	8% 2 12% 31% 26% 20%	524
	21st to end	Day	10% 4 14% 30% 24% 19%	532
August	1st to 10th	Day	18% 4 19% 23% 21% 15%	486
	11th to 20th	Day	11% 4 15% 30% 26% 13%	479
	21st to end	Day	14% 3 12% 27% 30% 14%	539
September	1st to 10th	Day	11% 5% 16% 30% 28% 10%	490
	11th to 20th	Day	18% 5% 15% 28% 26% 9%	490
	21st to end	Day	22% 6% 17% 29% 20% 6%	490
October	1st to 10th	Day	20% 6% 23% 27% 17% 8%	490
	11th to 20th	Day	13% 13% 27% 30% 14% 3	490
	21st to end	Day	19% 10% 27% 31% 10% 3	539
November	1st to 10th	Day	21% 11% 30% 23% 12% 2	386
	11th to 20th	Day	21% 21% 34% 20% 4	300
	21st to end	Day	15% 17% 44% 17% 6% 1	300
December	1st to 10th	Day	27% 26% 32% 13% 2	300
	11th to 20th	Day	24% 18% 40% 13% 4	300
	21st to end	Day	31% 17% 36% 11% 3 1	330
January	1st to 10th	Night	22% 19% 32% 22% 5%	800
	11th to 20th	Night	19% 20% 31% 24% 6%	800
	21st to end	Night	20% 18% 36% 23% 3	880
February	1st to 10th	Night	18% 17% 30% 31% 4	800
	11th to 20th	Night	24% 19% 34% 20% 2	783
	21st to end	Night	23% 21% 32% 22% 3	660
March	1st to 10th	Night	20% 17% 31% 27% 6%	800
	11th to 20th	Night	20% 17% 32% 23% 7% 1	800
	21st to end	Night	21% 16% 31% 23% 9%	880
April	1st to 10th	Night	19% 19% 28% 26% 8% 1	800
	11th to 20th	Night	19% 14% 25% 26% 14% 1	659
	21st to end	Night	15% 10% 23% 32% 19% 1	600
May	1st to 10th	Night	16% 12% 24% 26% 20% 2	600
	11th to 20th	Night	21% 7% 19% 27% 23% 3	591
	21st to end	Night	16% 5% 14% 26% 31% 8%	650
June	1st to 10th	Night	14% 4 13% 35% 29% 7%	600
	11th to 20th	Night	10% 4 14% 27% 32% 12%	600
	21st to end	Night	8% 3 11% 33% 38% 7%	600
July	1st to 10th	Night	12% 2 10% 24% 43% 9%	585
	11th to 20th	Night	11% 2 7% 25% 42% 13%	582
	21st to end	Night	9% 3 8% 29% 40% 11%	624
August	1st to 10th	Night	15% 2 10% 24% 37% 11%	567
	11th to 20th	Night	15% 3 11% 25% 37% 9%	564
	21st to end	Night	14% 3 8% 25% 39% 10%	660
September	1st to 10th	Night	15% 4 10% 27% 35% 9%	760
	11th to 20th	Night	22% 3 13% 23% 33% 6%	760
	21st to end	Night	21% 5% 13% 34% 23% 4	760
October	1st to 10th	Night	17% 8% 19% 24% 25% 8%	760
	11th to 20th	Night	18% 10% 19% 30% 20% 3	760
	21st to end	Night	18% 10% 19% 34% 16% 3	836
November	1st to 10th	Night	18% 7% 20% 33% 19% 3	780
	11th to 20th	Night	17% 14% 24% 31% 12% 2	800
	21st to end	Night	18% 14% 22% 32% 12% 2	800
December	1st to 10th	Night	24% 15% 24% 30% 7%	800
	11th to 20th	Night	20% 13% 27% 31% 8% 1	800
	21st to end	Night	29% 13% 24% 28% 6%	880

Page generated at 2025-07-18 01:09:58. Version ac07

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