Estero Llano Grande State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Estero Llano Grande 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
Transparency	Day	35% 6% 15% 23% 14% 6%	130888
	Night	36% 6% 16% 22% 14% 7%	128475
Seeing	Day	10% 5% 23% 34% 21% 7%	15705
	Night	13% 5% 23% 37% 20% 2	25741

By Month

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	44% 5% 9% 18% 15% 9%	4078
	11th to 20th	Day	43% 5% 10% 21% 14% 7%	4282
	21st to end	Day	52% 6% 9% 14% 15% 5%	4994
February	1st to 10th	Day	42% 5% 9% 16% 17% 12%	2000
	11th to 20th	Day	37% 6% 11% 20% 17% 8%	1959
	21st to end	Day	36% 5% 11% 21% 19% 8%	1689
March	1st to 10th	Day	37% 4 11% 20% 11% 16%	4936
	11th to 20th	Day	39% 4 8% 10% 24% 15%	4980
	21st to end	Day	33% 4 9% 26% 16% 12%	5464
April	1st to 10th	Day	35% 6% 12% 21% 15% 10%	2200
	11th to 20th	Day	38% 7% 12% 21% 14% 8%	2176
	21st to end	Day	35% 7% 13% 21% 17% 7%	2260
May	1st to 10th	Day	37% 7% 17% 25% 10% 4	5900
	11th to 20th	Day	25% 6% 13% 28% 18% 9%	5866
	21st to end	Day	29% 6% 12% 35% 16% 1	6447
June	1st to 10th	Day	24% 7% 14% 32% 20% 3	2600
	11th to 20th	Day	28% 8% 13% 24% 24% 3	2600
	21st to end	Day	36% 11% 19% 25% 9% 1	2600
July	1st to 10th	Day	42% 8% 23% 23% 4	5836
	11th to 20th	Day	32% 8% 28% 24% 7%	5831
	21st to end	Day	32% 7% 25% 30% 6%	6207
August	1st to 10th	Day	13% 6% 23% 47% 11%	3892
	11th to 20th	Day	22% 11% 37% 25% 5%	3882
	21st to end	Day	28% 11% 24% 27% 10% 1	3967
September	1st to 10th	Day	44% 10% 15% 18% 11% 2	2200
	11th to 20th	Day	45% 12% 14% 17% 9% 2	2200
	21st to end	Day	36% 9% 15% 23% 12% 5%	2200
October	1st to 10th	Day	28% 5% 8% 14% 27% 18%	3590
	11th to 20th	Day	26% 6% 11% 18% 27% 11%	3417
	21st to end	Day	26% 5% 9% 22% 27% 11%	3538
November	1st to 10th	Day	34% 7% 9% 22% 20% 8%	2058
	11th to 20th	Day	41% 4 9% 19% 18% 8%	2100
	21st to end	Day	40% 4 11% 19% 17% 9%	1969
December	1st to 10th	Day	61% 3 9% 14% 10% 4	3030
	11th to 20th	Day	44% 6% 11% 17% 11% 11%	3452
	21st to end	Day	36% 4 8% 23% 19% 10%	4488
January	1st to 10th	Night	45% 4 10% 18% 14% 10%	5888
	11th to 20th	Night	45% 5% 9% 19% 15% 7%	5741
	21st to end	Night	55% 5% 10% 13% 12% 5%	5984
February	1st to 10th	Night	42% 5% 10% 16% 14% 13%	2400
	11th to 20th	Night	43% 5% 11% 18% 16% 7%	2338
	21st to end	Night	40% 5% 9% 19% 18% 9%	1939
March	1st to 10th	Night	42% 5% 11% 20% 11% 11%	4919
	11th to 20th	Night	42% 5% 10% 12% 16% 17%	4980
	21st to end	Night	35% 5% 11% 21% 20% 8%	5467
April	1st to 10th	Night	39% 6% 17% 21% 12% 7%	2200
	11th to 20th	Night	42% 6% 13% 17% 13% 8%	2173
	21st to end	Night	41% 8% 14% 17% 12% 7%	2129
May	1st to 10th	Night	49% 8% 16% 16% 9% 3	4080
	11th to 20th	Night	35% 7% 15% 23% 15% 5%	4054
	21st to end	Night	39% 8% 17% 29% 6%	4452
June	1st to 10th	Night	20% 7% 21% 32% 19% 2	1800
	11th to 20th	Night	24% 8% 14% 34% 18% 3	1800
	21st to end	Night	24% 11% 25% 29% 9% 1	1800
July	1st to 10th	Night	40% 9% 28% 20% 3	4035
	11th to 20th	Night	30% 9% 36% 22% 3	4026
	21st to end	Night	25% 7% 31% 30% 6%	4333
August	1st to 10th	Night	7% 5% 28% 52% 8%	3244
	11th to 20th	Night	18% 8% 43% 29% 2	3243
	21st to end	Night	15% 9% 34% 32% 9% 1	3917
September	1st to 10th	Night	30% 10% 24% 24% 9% 2	2200
	11th to 20th	Night	33% 11% 20% 25% 10% 2	2200
	21st to end	Night	26% 9% 17% 29% 13% 5%	2200
October	1st to 10th	Night	18% 4 9% 19% 28% 21%	3590
	11th to 20th	Night	23% 5% 11% 20% 25% 16%	3686
	21st to end	Night	24% 4 7% 24% 31% 9%	4252
November	1st to 10th	Night	27% 6% 12% 23% 23% 8%	2460
	11th to 20th	Night	35% 6% 12% 22% 17% 9%	2520
	21st to end	Night	38% 4 14% 20% 14% 9%	2646
December	1st to 10th	Night	61% 3 7% 12% 12% 4	4380
	11th to 20th	Night	37% 6% 11% 23% 12% 11%	4909
	21st to end	Night	37% 4 10% 18% 17% 14%	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	20% 12% 29% 26% 10% 4	300
	11th to 20th	Day	22% 8% 32% 29% 8% 1	300
	21st to end	Day	22% 10% 36% 20% 10% 2	330
February	1st to 10th	Day	17% 11% 34% 25% 13% 1	300
	11th to 20th	Day	20% 10% 40% 23% 7%	300
	21st to end	Day	16% 10% 46% 22% 6%	249
March	1st to 10th	Day	20% 9% 37% 29% 5%	300
	11th to 20th	Day	19% 10% 37% 29% 5% 1	300
	21st to end	Day	10% 12% 50% 25% 3	330
April	1st to 10th	Day	13% 11% 42% 25% 7% 1	300
	11th to 20th	Day	11% 12% 40% 27% 7% 1	294
	21st to end	Day	10% 9% 45% 28% 6% 1	360
May	1st to 10th	Day	10% 8% 47% 25% 10% 1	703
	11th to 20th	Day	8% 7% 43% 32% 9% 1	725
	21st to end	Day	6% 3 35% 42% 13% 1	789
June	1st to 10th	Day	3 2 19% 42% 26% 8%	730
	11th to 20th	Day	5% 2 16% 52% 21% 4	730
	21st to end	Day	7% 2 13% 41% 28% 9%	730
July	1st to 10th	Day	10% 2 12% 39% 30% 7%	721
	11th to 20th	Day	5% 1 6% 42% 36% 10%	718
	21st to end	Day	6% 1 5% 42% 36% 10%	786
August	1st to 10th	Day	1 6% 51% 28% 14%	527
	11th to 20th	Day	2 6% 47% 32% 12%	517
	21st to end	Day	2 1 8% 22% 40% 28%	382
September	1st to 10th	Day	12% 2 4 28% 35% 19%	330
	11th to 20th	Day	9% 1 3 26% 32% 28%	330
	21st to end	Day	4 1 8% 23% 41% 22%	330
October	1st to 10th	Day	7% 1 8% 29% 36% 19%	330
	11th to 20th	Day	7% 12% 27% 36% 18%	330
	21st to end	Day	10% 5% 20% 33% 25% 8%	363
November	1st to 10th	Day	12% 3 16% 34% 30% 5%	330
	11th to 20th	Day	22% 4 16% 25% 22% 10%	330
	21st to end	Day	23% 8% 29% 19% 14% 6%	330
December	1st to 10th	Day	25% 4 21% 28% 17% 6%	330
	11th to 20th	Day	18% 9% 24% 28% 17% 4	321
	21st to end	Day	19% 8% 26% 31% 12% 3	330
January	1st to 10th	Night	23% 7% 26% 32% 12% 1	1000
	11th to 20th	Night	23% 7% 28% 34% 7%	932
	21st to end	Night	24% 6% 26% 34% 9%	880
February	1st to 10th	Night	22% 6% 33% 33% 7% 1	800
	11th to 20th	Night	22% 9% 33% 32% 5%	784
	21st to end	Night	20% 8% 39% 27% 6%	619
March	1st to 10th	Night	18% 10% 35% 32% 5%	600
	11th to 20th	Night	16% 10% 41% 30% 4	600
	21st to end	Night	13% 9% 47% 27% 4	660
April	1st to 10th	Night	14% 8% 45% 29% 5%	600
	11th to 20th	Night	15% 8% 40% 31% 6%	593
	21st to end	Night	16% 7% 44% 29% 5%	600
May	1st to 10th	Night	12% 7% 49% 27% 6%	600
	11th to 20th	Night	11% 5% 39% 39% 6%	591
	21st to end	Night	6% 4 34% 43% 12% 1	650
June	1st to 10th	Night	4 1 15% 54% 25% 1	600
	11th to 20th	Night	3 2 18% 56% 21% 1	600
	21st to end	Night	5% 2 16% 45% 31% 3	600
July	1st to 10th	Night	9% 1 9% 52% 26% 3	585
	11th to 20th	Night	5% 1 7% 51% 34% 2	582
	21st to end	Night	5% 1 5% 52% 36% 2	657
August	1st to 10th	Night	1 5% 49% 42% 3	597
	11th to 20th	Night	3 5% 44% 44% 4	594
	21st to end	Night	5% 3 31% 53% 8%	660
September	1st to 10th	Night	7% 1 4 31% 50% 9%	600
	11th to 20th	Night	11% 1 5% 23% 52% 9%	600
	21st to end	Night	7% 1 6% 31% 46% 9%	600
October	1st to 10th	Night	4 2 6% 34% 48% 7%	600
	11th to 20th	Night	10% 2 10% 40% 35% 3	665
	21st to end	Night	8% 4 22% 42% 22% 2	880
November	1st to 10th	Night	11% 4 18% 43% 23% 2	820
	11th to 20th	Night	17% 3 19% 39% 21% 2	840
	21st to end	Night	19% 4 26% 35% 14% 1	966
December	1st to 10th	Night	22% 4 23% 35% 13% 2	1050
	11th to 20th	Night	20% 6% 25% 34% 14% 1	1036
	21st to end	Night	19% 6% 27% 36% 12%	1100

Page generated at 2025-12-15 00:13:51. Version ac07

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