Echo Bluff State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Echo Bluff State Park clear sky chart from 2005-11-06 to 2026-05-02.

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% 7% 2 6% 4 4 4 4 5% 7% 44%	131665
	Night	13% 7% 2 6% 4 4 4 3 5% 6% 46%	131076
Transparency	Day	37% 6% 11% 25% 17% 4	135263
	Night	37% 5% 11% 24% 19% 4	135557
Seeing	Day	18% 13% 26% 24% 15% 4	17480
	Night	18% 11% 28% 27% 14% 2	27403

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% 10% 3 8% 3 3 3 3 4 5% 44%	4931
	11th to 20th	Day	8% 7% 3 7% 4 4 4 3 4 5% 51%	5310
	21st to end	Day	18% 7% 3 6% 3 3 3 3 4 5% 45%	5812
February	1st to 10th	Day	17% 10% 3 6% 5% 4 4 4 4 5% 38%	1890
	11th to 20th	Day	17% 8% 2 7% 4 3 4 4 4 6% 41%	1995
	21st to end	Day	15% 10% 3 5% 4 4 4 4 5% 6% 39%	1730
March	1st to 10th	Day	17% 12% 2 6% 3 3 3 3 5% 5% 43%	4862
	11th to 20th	Day	11% 6% 2 5% 3 3 3 3 5% 6% 54%	5090
	21st to end	Day	15% 6% 2 6% 4 5% 5% 4 5% 7% 39%	5759
April	1st to 10th	Day	14% 7% 3 7% 4 3 3 4 5% 7% 45%	2520
	11th to 20th	Day	16% 8% 3 6% 5% 4 4 3 4 6% 40%	2494
	21st to end	Day	18% 8% 3 6% 6% 4 4 3 5% 6% 37%	2520
May	1st to 10th	Day	15% 7% 3 7% 6% 6% 6% 5% 7% 9% 29%	5417
	11th to 20th	Day	15% 8% 3 8% 5% 5% 5% 4 6% 7% 35%	6115
	21st to end	Day	19% 7% 2 6% 4 4 4 3 5% 7% 39%	6935
June	1st to 10th	Day	9% 5% 2 7% 6% 6% 5% 4 5% 8% 43%	2800
	11th to 20th	Day	6% 5% 2 5% 5% 5% 5% 4 7% 9% 49%	2800
	21st to end	Day	5% 3 2 4 5% 5% 6% 5% 8% 9% 49%	2800
July	1st to 10th	Day	9% 4 2 7% 5% 5% 5% 4 6% 8% 45%	6360
	11th to 20th	Day	5% 4 2 6% 5% 5% 6% 5% 7% 11% 44%	6069
	21st to end	Day	7% 5% 2 6% 5% 5% 6% 5% 7% 11% 42%	6422
August	1st to 10th	Day	4 3 2 4 4 4 5% 4 6% 9% 56%	4234
	11th to 20th	Day	11% 5% 2 6% 5% 5% 4 4 6% 7% 44%	3863
	21st to end	Day	7% 4 2 5% 4 4 4 4 6% 8% 53%	4312
September	1st to 10th	Day	11% 5% 2 5% 3 4 5% 4 6% 7% 49%	2400
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 6% 7% 47%	2400
	21st to end	Day	11% 5% 2 5% 4 3 3 3 5% 7% 52%	2135
October	1st to 10th	Day	8% 5% 2 5% 4 4 4 2 5% 5% 57%	2000
	11th to 20th	Day	14% 6% 2 4 3 3 3 2 3 5% 55%	2000
	21st to end	Day	19% 7% 3 5% 3 3 3 3 4 4 47%	2200
November	1st to 10th	Day	13% 6% 2 4 3 3 3 3 4 5% 53%	1948
	11th to 20th	Day	13% 7% 3 6% 3 3 3 3 4 7% 50%	1890
	21st to end	Day	19% 8% 2 5% 3 3 4 2 4 4 45%	1804
December	1st to 10th	Day	12% 9% 2 6% 3 3 3 2 4 5% 50%	2690
	11th to 20th	Day	14% 9% 3 8% 4 3 4 2 4 5% 42%	3088
	21st to end	Day	20% 18% 4 7% 4 4 4 3 4 4 29%	4070
January	1st to 10th	Night	14% 10% 4 8% 4 4 3 3 4 5% 41%	7974
	11th to 20th	Night	9% 7% 3 8% 4 4 3 3 4 5% 50%	7680
	21st to end	Night	16% 9% 2 7% 5% 4 3 3 4 5% 41%	8402
February	1st to 10th	Night	16% 10% 3 6% 3 3 3 3 5% 6% 42%	2730
	11th to 20th	Night	16% 7% 3 7% 4 3 3 3 4 6% 43%	2510
	21st to end	Night	17% 8% 2 6% 4 3 4 3 4 5% 44%	2076
March	1st to 10th	Night	18% 11% 3 6% 3 3 4 3 4 4 41%	5240
	11th to 20th	Night	11% 8% 2 6% 4 3 3 3 4 6% 49%	5090
	21st to end	Night	14% 8% 3 6% 4 4 4 4 5% 7% 40%	5410
April	1st to 10th	Night	11% 6% 1 4 4 3 3 3 5% 9% 50%	2100
	11th to 20th	Night	14% 7% 2 6% 4 4 3 3 5% 6% 45%	2075
	21st to end	Night	18% 7% 2 6% 4 3 4 3 5% 8% 40%	2100
May	1st to 10th	Night	17% 7% 2 6% 4 3 4 4 7% 8% 38%	4500
	11th to 20th	Night	14% 9% 2 7% 4 4 4 4 5% 8% 39%	3795
	21st to end	Night	20% 9% 2 6% 4 4 4 3 5% 6% 37%	3942
June	1st to 10th	Night	8% 4 2 6% 5% 4 3 4 6% 8% 50%	1600
	11th to 20th	Night	6% 3 1 3 2 3 3 4 6% 11% 58%	1600
	21st to end	Night	3 3 1 3 3 4 3 4 7% 11% 59%	1600
July	1st to 10th	Night	9% 4 2 6% 4 4 5% 4 6% 9% 46%	3618
	11th to 20th	Night	4 4 2 6% 4 4 4 4 6% 9% 54%	3890
	21st to end	Night	6% 4 2 6% 4 4 5% 4 6% 9% 48%	4449
August	1st to 10th	Night	3 2 1 4 3 3 4 4 6% 8% 61%	2926
	11th to 20th	Night	8% 5% 2 5% 5% 5% 5% 3 5% 7% 49%	3184
	21st to end	Night	5% 4 2 4 3 3 4 3 5% 8% 59%	3586
September	1st to 10th	Night	10% 4 2 4 3 3 4 3 5% 7% 54%	2000
	11th to 20th	Night	9% 5% 2 4 4 4 4 4 5% 7% 52%	2000
	21st to end	Night	9% 5% 2 6% 3 3 4 3 4 6% 54%	2239
October	1st to 10th	Night	7% 4 1 4 3 3 3 3 4 6% 62%	2400
	11th to 20th	Night	13% 6% 1 4 3 3 3 2 4 5% 57%	2400
	21st to end	Night	20% 6% 2 4 3 3 3 2 3 5% 49%	2640
November	1st to 10th	Night	12% 5% 2 5% 2 2 3 2 5% 5% 56%	2567
	11th to 20th	Night	14% 6% 2 5% 4 3 3 3 4 6% 50%	2730
	21st to end	Night	18% 9% 3 5% 3 3 3 2 4 5% 45%	2814
December	1st to 10th	Night	13% 8% 2 5% 3 4 4 3 5% 6% 48%	4720
	11th to 20th	Night	17% 8% 2 6% 3 4 3 2 4 5% 44%	5339
	21st to end	Night	25% 15% 3 7% 4 4 3 3 4 4 28%	7150

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	43% 3 11% 27% 14% 2	4932
	11th to 20th	Day	35% 3 7% 28% 21% 6%	5310
	21st to end	Day	43% 3 9% 19% 16% 10%	5812
February	1st to 10th	Day	49% 4 12% 21% 13% 1	1890
	11th to 20th	Day	45% 4 10% 21% 16% 4	2005
	21st to end	Day	46% 4 7% 21% 14% 7%	1730
March	1st to 10th	Day	44% 4 6% 21% 13% 11%	4862
	11th to 20th	Day	31% 4 8% 24% 22% 10%	5090
	21st to end	Day	42% 7% 13% 26% 12% 1	5761
April	1st to 10th	Day	38% 5% 13% 22% 19% 2	2520
	11th to 20th	Day	45% 5% 11% 20% 15% 4	2494
	21st to end	Day	46% 7% 11% 21% 14% 1	2520
May	1st to 10th	Day	46% 10% 13% 18% 12% 1	5452
	11th to 20th	Day	46% 9% 12% 20% 13% 1	6119
	21st to end	Day	44% 7% 9% 23% 15% 2	6949
June	1st to 10th	Day	37% 9% 13% 24% 16% 1	2800
	11th to 20th	Day	30% 8% 13% 28% 18% 3	2800
	21st to end	Day	26% 9% 20% 25% 16% 4	2800
July	1st to 10th	Day	35% 7% 12% 26% 18% 2	6291
	11th to 20th	Day	32% 9% 16% 30% 12% 2	5996
	21st to end	Day	33% 9% 16% 29% 12% 1	6240
August	1st to 10th	Day	23% 7% 17% 31% 21% 1	4220
	11th to 20th	Day	37% 7% 13% 25% 16% 2	3899
	21st to end	Day	28% 7% 15% 34% 13% 3	4311
September	1st to 10th	Day	32% 8% 12% 27% 16% 6%	2400
	11th to 20th	Day	34% 7% 9% 24% 25% 1	2400
	21st to end	Day	31% 5% 9% 25% 26% 3	2135
October	1st to 10th	Day	18% 4 5% 17% 44% 12%	3260
	11th to 20th	Day	23% 3 6% 21% 41% 8%	3240
	21st to end	Day	31% 3 6% 31% 24% 4	3538
November	1st to 10th	Day	34% 4 9% 25% 22% 6%	1948
	11th to 20th	Day	36% 4 8% 24% 22% 7%	1890
	21st to end	Day	43% 5% 8% 25% 18% 2	1804
December	1st to 10th	Day	36% 4 9% 35% 15% 2	2690
	11th to 20th	Day	44% 4 7% 24% 19% 1	3085
	21st to end	Day	58% 5% 11% 14% 10% 2	4070
January	1st to 10th	Night	45% 4 12% 25% 12% 1	7975
	11th to 20th	Night	36% 4 7% 24% 25% 4	7680
	21st to end	Night	45% 4 8% 21% 18% 4	8402
February	1st to 10th	Night	44% 4 12% 23% 15% 2	2730
	11th to 20th	Night	42% 4 12% 21% 17% 3	2511
	21st to end	Night	42% 4 8% 22% 19% 5%	2076
March	1st to 10th	Night	46% 4 6% 20% 15% 7%	5240
	11th to 20th	Night	36% 5% 8% 23% 18% 10%	5090
	21st to end	Night	40% 7% 13% 25% 14% 1	5410
April	1st to 10th	Night	31% 6% 14% 24% 21% 4	2100
	11th to 20th	Night	39% 6% 11% 23% 16% 5%	2075
	21st to end	Night	43% 6% 10% 24% 15% 2	2100
May	1st to 10th	Night	41% 9% 16% 21% 12% 1	4530
	11th to 20th	Night	41% 9% 12% 23% 12% 3	3796
	21st to end	Night	46% 8% 10% 21% 12% 3	3950
June	1st to 10th	Night	30% 8% 16% 24% 19% 2	1600
	11th to 20th	Night	21% 6% 14% 35% 20% 4	1600
	21st to end	Night	18% 8% 19% 29% 18% 8%	1600
July	1st to 10th	Night	33% 7% 14% 22% 21% 2	3580
	11th to 20th	Night	26% 8% 16% 34% 15% 2	3844
	21st to end	Night	29% 9% 20% 29% 13% 1	4320
August	1st to 10th	Night	18% 7% 18% 34% 22% 1	2916
	11th to 20th	Night	33% 7% 17% 25% 15% 3	3214
	21st to end	Night	22% 6% 15% 36% 18% 3	3586
September	1st to 10th	Night	29% 7% 12% 28% 20% 5%	2000
	11th to 20th	Night	30% 7% 11% 26% 24% 2	2000
	21st to end	Night	30% 6% 10% 23% 29% 3	2239
October	1st to 10th	Night	14% 3 7% 17% 45% 14%	3920
	11th to 20th	Night	22% 3 6% 20% 34% 14%	3899
	21st to end	Night	31% 4 7% 26% 29% 4	4252
November	1st to 10th	Night	30% 4 11% 28% 23% 5%	2567
	11th to 20th	Night	34% 5% 8% 24% 23% 7%	2730
	21st to end	Night	42% 4 7% 24% 21% 2	2814
December	1st to 10th	Night	37% 4 9% 32% 16% 1	4720
	11th to 20th	Night	43% 4 8% 23% 20% 2	5341
	21st to end	Night	58% 5% 11% 17% 7% 1	7150

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% 25% 32% 15% 2	330
	11th to 20th	Day	30% 26% 32% 10% 2	330
	21st to end	Day	23% 32% 33% 10% 2	363
February	1st to 10th	Day	27% 25% 35% 10% 4	330
	11th to 20th	Day	35% 23% 30% 9% 2 1	330
	21st to end	Day	31% 22% 34% 11% 1	273
March	1st to 10th	Day	28% 22% 35% 12% 2	330
	11th to 20th	Day	33% 23% 32% 10% 2	330
	21st to end	Day	30% 22% 35% 10% 3	436
April	1st to 10th	Day	25% 19% 33% 18% 6%	540
	11th to 20th	Day	26% 23% 30% 14% 6% 1	532
	21st to end	Day	23% 17% 34% 18% 6% 1	540
May	1st to 10th	Day	20% 22% 33% 19% 7% 1	507
	11th to 20th	Day	19% 14% 30% 22% 11% 3	715
	21st to end	Day	16% 9% 33% 25% 13% 4	789
June	1st to 10th	Day	11% 7% 24% 30% 22% 6%	730
	11th to 20th	Day	8% 4 21% 40% 22% 5%	730
	21st to end	Day	5% 6% 28% 38% 19% 4	730
July	1st to 10th	Day	11% 4 16% 31% 30% 9%	721
	11th to 20th	Day	5% 4 21% 35% 29% 7%	718
	21st to end	Day	10% 3 13% 34% 30% 10%	794
August	1st to 10th	Day	9% 2 16% 40% 26% 7%	726
	11th to 20th	Day	16% 2 17% 30% 27% 9%	533
	21st to end	Day	11% 2 13% 29% 31% 13%	583
September	1st to 10th	Day	11% 4 17% 32% 29% 7%	530
	11th to 20th	Day	10% 4 17% 29% 28% 13%	530
	21st to end	Day	15% 9% 24% 26% 19% 8%	444
October	1st to 10th	Day	12% 9% 28% 33% 12% 6%	330
	11th to 20th	Day	20% 16% 33% 22% 8% 1	330
	21st to end	Day	28% 21% 29% 19% 3	363
November	1st to 10th	Day	20% 13% 34% 26% 5% 2	330
	11th to 20th	Day	21% 18% 35% 17% 8% 1	330
	21st to end	Day	33% 15% 30% 15% 6% 1	330
December	1st to 10th	Day	21% 24% 33% 16% 5% 2	330
	11th to 20th	Day	25% 22% 32% 15% 6%	330
	21st to end	Day	31% 21% 33% 11% 3	363
January	1st to 10th	Night	23% 20% 33% 20% 4	1050
	11th to 20th	Night	23% 23% 34% 16% 3	1050
	21st to end	Night	20% 19% 38% 21% 2	1155
February	1st to 10th	Night	24% 17% 37% 20% 1	1050
	11th to 20th	Night	24% 20% 38% 17% 2	875
	21st to end	Night	24% 20% 36% 18% 1	692
March	1st to 10th	Night	25% 16% 35% 22% 2	730
	11th to 20th	Night	26% 15% 32% 23% 4	630
	21st to end	Night	24% 17% 34% 21% 5%	693
April	1st to 10th	Night	17% 17% 37% 25% 4	630
	11th to 20th	Night	19% 17% 33% 24% 7%	623
	21st to end	Night	21% 11% 39% 21% 8%	630
May	1st to 10th	Night	16% 8% 36% 31% 9%	603
	11th to 20th	Night	18% 7% 32% 27% 15% 2	591
	21st to end	Night	14% 6% 26% 34% 15% 4	650
June	1st to 10th	Night	9% 5% 19% 36% 29% 2	600
	11th to 20th	Night	8% 2 19% 44% 25% 2	600
	21st to end	Night	5% 2 21% 39% 32% 2	600
July	1st to 10th	Night	10% 1 13% 33% 34% 9%	585
	11th to 20th	Night	5% 2 12% 40% 36% 6%	582
	21st to end	Night	5% 1 14% 38% 36% 6%	657
August	1st to 10th	Night	6% 2 10% 41% 37% 4	597
	11th to 20th	Night	8% 1 13% 37% 37% 3	594
	21st to end	Night	9% 2 10% 35% 38% 7%	660
September	1st to 10th	Night	11% 2 12% 38% 33% 4	600
	11th to 20th	Night	12% 2 13% 31% 36% 5%	600
	21st to end	Night	11% 6% 22% 30% 28% 3	757
October	1st to 10th	Night	9% 5% 24% 34% 26% 3	800
	11th to 20th	Night	17% 11% 29% 29% 14%	800
	21st to end	Night	24% 13% 28% 27% 8%	880
November	1st to 10th	Night	15% 10% 35% 30% 10%	820
	11th to 20th	Night	18% 14% 32% 27% 8%	840
	21st to end	Night	24% 13% 31% 23% 7%	924
December	1st to 10th	Night	23% 15% 33% 24% 5%	1050
	11th to 20th	Night	26% 14% 31% 24% 5%	1050
	21st to end	Night	29% 16% 31% 21% 3	1155

Page generated at 2026-04-29 01:21:46. Version ac07

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