Lake Casa Blanca International State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Casa Blanca International 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	10% 5% 2 5% 4 4 4 3 5% 7% 51%	126969
	Night	11% 5% 2 4 3 3 3 3 5% 7% 54%	124346
Transparency	Day	31% 6% 11% 23% 18% 11%	130847
	Night	29% 6% 13% 22% 18% 12%	128529
Seeing	Day	9% 4 18% 35% 26% 8%	15901
	Night	11% 4 27% 44% 13% 1	25934

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	18% 5% 2 6% 3 3 3 2 3 6% 49%	4077
	11th to 20th	Day	16% 4 1 4 3 3 4 3 5% 7% 51%	4466
	21st to end	Day	20% 6% 2 5% 3 3 3 3 6% 6% 42%	4994
February	1st to 10th	Day	13% 8% 2 7% 5% 3 3 3 3 5% 47%	2000
	11th to 20th	Day	15% 7% 2 5% 3 3 4 3 3 5% 50%	1949
	21st to end	Day	13% 6% 1 4 4 3 2 3 5% 6% 53%	1650
March	1st to 10th	Day	10% 5% 2 4 3 3 4 3 6% 7% 53%	4733
	11th to 20th	Day	16% 6% 2 4 2 2 2 2 4 5% 55%	4980
	21st to end	Day	11% 5% 2 4 3 3 3 3 4 6% 57%	5462
April	1st to 10th	Day	11% 5% 1 5% 3 4 4 4 4 7% 52%	2200
	11th to 20th	Day	12% 5% 3 6% 4 3 3 4 5% 7% 48%	2260
	21st to end	Day	10% 6% 2 6% 4 4 3 4 6% 7% 48%	2400
May	1st to 10th	Day	16% 7% 3 6% 4 3 4 3 5% 8% 41%	5771
	11th to 20th	Day	7% 4 2 5% 3 3 4 3 5% 8% 56%	5862
	21st to end	Day	6% 5% 2 6% 4 5% 5% 4 7% 10% 47%	6434
June	1st to 10th	Day	3 2 1 4 3 4 4 3 5% 11% 59%	2600
	11th to 20th	Day	3 3 1 4 3 4 4 3 5% 9% 62%	2600
	21st to end	Day	5% 3 2 5% 5% 5% 6% 4 7% 10% 48%	2600
July	1st to 10th	Day	7% 5% 2 7% 6% 5% 5% 4 6% 9% 42%	5900
	11th to 20th	Day	4 5% 2 6% 4 5% 5% 4 7% 10% 48%	5900
	21st to end	Day	3 3 2 5% 4 4 5% 4 7% 10% 52%	6088
August	1st to 10th	Day	1 1 2 2 2 2 2 3 7% 79%	3905
	11th to 20th	Day	2 1 1 3 2 3 4 4 6% 10% 63%	3846
	21st to end	Day	4 2 1 4 4 4 5% 5% 6% 11% 55%	4218
September	1st to 10th	Day	9% 7% 3 8% 6% 5% 5% 4 5% 8% 42%	2200
	11th to 20th	Day	10% 5% 2 6% 5% 6% 5% 4 8% 8% 41%	2200
	21st to end	Day	7% 4 2 6% 4 5% 5% 3 6% 8% 51%	2200
October	1st to 10th	Day	6% 3 2 5% 3 4 4 3 5% 6% 59%	2200
	11th to 20th	Day	10% 5% 2 5% 3 4 4 3 5% 6% 54%	2200
	21st to end	Day	9% 3 1 3 4 3 3 2 3 5% 62%	2212
November	1st to 10th	Day	11% 6% 2 6% 4 3 4 3 5% 5% 52%	2058
	11th to 20th	Day	13% 6% 2 6% 3 3 2 3 3 5% 54%	1942
	21st to end	Day	17% 7% 3 5% 4 4 3 2 4 5% 47%	1890
December	1st to 10th	Day	32% 7% 2 4 3 3 3 2 4 4 34%	3030
	11th to 20th	Day	14% 8% 3 6% 4 4 4 4 5% 6% 44%	3454
	21st to end	Day	10% 6% 2 6% 3 3 3 3 5% 6% 54%	4488
January	1st to 10th	Night	20% 5% 2 4 2 2 2 2 4 5% 51%	5888
	11th to 20th	Night	14% 4 1 4 3 2 3 2 6% 8% 54%	5557
	21st to end	Night	24% 6% 2 5% 3 3 3 3 4 6% 41%	5984
February	1st to 10th	Night	11% 6% 1 5% 3 3 3 3 5% 6% 53%	2400
	11th to 20th	Night	17% 5% 2 5% 3 2 2 3 4 6% 50%	2338
	21st to end	Night	12% 6% 1 4 3 3 3 3 5% 6% 54%	1980
March	1st to 10th	Night	11% 5% 1 4 3 3 4 3 5% 6% 54%	5127
	11th to 20th	Night	16% 5% 2 5% 3 3 3 2 4 5% 54%	4980
	21st to end	Night	12% 4 1 3 2 2 3 3 5% 6% 59%	5467
April	1st to 10th	Night	10% 4 1 4 3 4 4 3 6% 8% 53%	2200
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 5% 7% 53%	2084
	21st to end	Night	12% 6% 2 5% 4 4 4 3 5% 6% 50%	2000
May	1st to 10th	Night	14% 6% 2 6% 3 3 4 3 5% 7% 46%	4127
	11th to 20th	Night	6% 4 1 3 2 3 4 3 6% 8% 59%	4053
	21st to end	Night	8% 5% 2 6% 4 4 4 4 6% 11% 46%	4443
June	1st to 10th	Night	2 2 1 3 3 2 3 3 6% 10% 65%	1800
	11th to 20th	Night	2 2 1 3 3 2 4 3 5% 9% 66%	1800
	21st to end	Night	3 3 1 3 3 5% 5% 5% 6% 11% 54%	1800
July	1st to 10th	Night	6% 5% 2 6% 5% 5% 5% 5% 7% 9% 45%	4078
	11th to 20th	Night	4 4 2 5% 4 4 4 4 6% 9% 54%	4077
	21st to end	Night	3 4 2 5% 4 3 4 4 6% 9% 57%	4763
August	1st to 10th	Night	1 1 1 1 1 1 1 3 5% 84%	3255
	11th to 20th	Night	1 2 1 3 3 3 5% 4 7% 12% 59%	3213
	21st to end	Night	2 2 1 4 3 3 3 3 5% 11% 62%	3687
September	1st to 10th	Night	8% 7% 2 6% 4 4 4 5% 7% 9% 44%	2200
	11th to 20th	Night	8% 5% 2 5% 4 4 4 5% 7% 10% 46%	2200
	21st to end	Night	7% 4 1 4 3 3 3 3 6% 8% 57%	2200
October	1st to 10th	Night	5% 3 2 4 3 2 4 3 4 6% 64%	2200
	11th to 20th	Night	10% 4 1 4 3 3 3 3 4 6% 59%	2200
	21st to end	Night	9% 4 1 3 2 2 3 2 2 4 69%	2605
November	1st to 10th	Night	11% 4 1 3 3 2 3 2 4 6% 59%	2460
	11th to 20th	Night	12% 4 2 4 3 3 3 3 4 6% 56%	2672
	21st to end	Night	16% 6% 1 4 4 3 3 3 3 5% 52%	2730
December	1st to 10th	Night	34% 8% 3 4 3 2 2 2 3 4 34%	4380
	11th to 20th	Night	14% 7% 2 5% 3 3 3 3 4 6% 50%	4908
	21st to end	Night	9% 5% 2 5% 3 3 3 3 4 6% 57%	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	39% 3 6% 16% 24% 13%	4078
	11th to 20th	Day	34% 3 5% 19% 25% 15%	4466
	21st to end	Day	43% 4 8% 16% 19% 10%	4994
February	1st to 10th	Day	40% 5% 8% 12% 18% 17%	2000
	11th to 20th	Day	38% 4 6% 19% 18% 15%	1959
	21st to end	Day	33% 5% 8% 17% 22% 14%	1650
March	1st to 10th	Day	29% 5% 11% 19% 13% 23%	4733
	11th to 20th	Day	33% 4 6% 9% 17% 31%	4980
	21st to end	Day	28% 4 9% 24% 21% 14%	5464
April	1st to 10th	Day	32% 6% 10% 17% 20% 15%	2200
	11th to 20th	Day	34% 7% 10% 16% 18% 15%	2260
	21st to end	Day	33% 6% 10% 19% 18% 14%	2400
May	1st to 10th	Day	40% 7% 10% 20% 17% 6%	5808
	11th to 20th	Day	25% 7% 14% 22% 21% 12%	5866
	21st to end	Day	29% 8% 10% 37% 14% 2	6447
June	1st to 10th	Day	19% 7% 13% 31% 25% 5%	2600
	11th to 20th	Day	20% 5% 11% 27% 29% 8%	2600
	21st to end	Day	30% 9% 16% 25% 18% 3	2600
July	1st to 10th	Day	37% 8% 17% 31% 7% 1	5836
	11th to 20th	Day	30% 8% 19% 31% 10% 2	5831
	21st to end	Day	24% 8% 20% 31% 17% 1	5916
August	1st to 10th	Day	9% 4 13% 42% 31% 2	3892
	11th to 20th	Day	15% 7% 22% 43% 12% 1	3882
	21st to end	Day	22% 8% 20% 29% 19% 2	4217
September	1st to 10th	Day	40% 9% 13% 18% 14% 6%	2200
	11th to 20th	Day	38% 9% 15% 20% 15% 4	2200
	21st to end	Day	29% 7% 13% 23% 16% 12%	2200
October	1st to 10th	Day	19% 4 6% 11% 26% 34%	3590
	11th to 20th	Day	28% 6% 8% 18% 16% 24%	3568
	21st to end	Day	21% 3 7% 17% 37% 16%	3550
November	1st to 10th	Day	34% 5% 10% 17% 22% 13%	2058
	11th to 20th	Day	34% 4 7% 20% 20% 14%	1942
	21st to end	Day	40% 5% 7% 20% 14% 14%	1890
December	1st to 10th	Day	53% 4 8% 13% 14% 8%	3030
	11th to 20th	Day	39% 6% 9% 20% 11% 16%	3452
	21st to end	Day	30% 4 6% 20% 25% 15%	4488
January	1st to 10th	Night	36% 4 6% 15% 22% 18%	5888
	11th to 20th	Night	30% 3 6% 18% 23% 20%	5557
	21st to end	Night	45% 4 6% 15% 20% 10%	5984
February	1st to 10th	Night	32% 5% 7% 17% 17% 21%	2400
	11th to 20th	Night	35% 5% 9% 17% 18% 16%	2338
	21st to end	Night	30% 6% 10% 18% 21% 15%	1980
March	1st to 10th	Night	30% 6% 10% 23% 12% 19%	5127
	11th to 20th	Night	34% 5% 7% 9% 17% 27%	4980
	21st to end	Night	26% 4 10% 24% 23% 12%	5467
April	1st to 10th	Night	28% 6% 13% 21% 18% 14%	2200
	11th to 20th	Night	30% 7% 13% 18% 17% 15%	2084
	21st to end	Night	33% 7% 13% 18% 17% 12%	2000
May	1st to 10th	Night	36% 7% 13% 22% 15% 7%	4152
	11th to 20th	Night	22% 6% 16% 20% 22% 14%	4054
	21st to end	Night	30% 7% 15% 34% 12% 1	4452
June	1st to 10th	Night	14% 7% 20% 34% 23% 3	1800
	11th to 20th	Night	15% 7% 12% 31% 29% 5%	1800
	21st to end	Night	23% 9% 20% 29% 15% 3	1800
July	1st to 10th	Night	34% 8% 22% 30% 5% 1	4035
	11th to 20th	Night	26% 7% 26% 31% 8% 1	4026
	21st to end	Night	24% 6% 23% 33% 13% 1	4625
August	1st to 10th	Night	6% 3 16% 48% 27% 1	3244
	11th to 20th	Night	16% 7% 31% 36% 9% 1	3243
	21st to end	Night	17% 8% 26% 34% 13% 2	3687
September	1st to 10th	Night	33% 11% 19% 18% 14% 5%	2200
	11th to 20th	Night	31% 9% 18% 26% 13% 3	2200
	21st to end	Night	24% 7% 15% 29% 16% 9%	2200
October	1st to 10th	Night	18% 5% 7% 17% 21% 33%	3590
	11th to 20th	Night	21% 4 12% 19% 22% 22%	3570
	21st to end	Night	20% 4 8% 18% 32% 19%	4205
November	1st to 10th	Night	26% 5% 9% 20% 26% 14%	2460
	11th to 20th	Night	30% 4 10% 20% 20% 16%	2672
	21st to end	Night	36% 5% 8% 20% 19% 13%	2730
December	1st to 10th	Night	55% 4 7% 11% 14% 10%	4380
	11th to 20th	Night	35% 5% 8% 22% 15% 16%	4909
	21st to end	Night	28% 5% 7% 18% 21% 20%	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	22% 6% 23% 35% 12% 3	300
	11th to 20th	Day	16% 7% 25% 35% 15% 2	300
	21st to end	Day	20% 7% 32% 26% 14% 2	330
February	1st to 10th	Day	15% 8% 26% 26% 21% 3	300
	11th to 20th	Day	19% 9% 32% 27% 11% 2	300
	21st to end	Day	16% 9% 28% 36% 10%	249
March	1st to 10th	Day	18% 8% 33% 28% 12% 1	300
	11th to 20th	Day	12% 7% 37% 34% 9% 1	300
	21st to end	Day	9% 9% 37% 36% 8%	330
April	1st to 10th	Day	11% 9% 35% 35% 10%	300
	11th to 20th	Day	9% 11% 34% 34% 12% 1	378
	21st to end	Day	8% 8% 40% 34% 8% 1	500
May	1st to 10th	Day	10% 7% 34% 37% 11% 1	663
	11th to 20th	Day	11% 3 32% 40% 12% 1	725
	21st to end	Day	7% 4 27% 47% 15% 1	789
June	1st to 10th	Day	3 1 11% 51% 30% 4	730
	11th to 20th	Day	3 1 12% 54% 26% 3	730
	21st to end	Day	6% 1 10% 42% 32% 9%	730
July	1st to 10th	Day	7% 2 8% 37% 35% 10%	721
	11th to 20th	Day	3 6% 38% 45% 7%	718
	21st to end	Day	3 1 4 41% 39% 12%	652
August	1st to 10th	Day	1 4 35% 46% 14%	527
	11th to 20th	Day	3 1 2 32% 45% 18%	517
	21st to end	Day	4 2 3 26% 35% 31%	528
September	1st to 10th	Day	10% 1 5% 18% 43% 23%	330
	11th to 20th	Day	5% 2 4 15% 34% 41%	330
	21st to end	Day	5% 6% 16% 47% 27%	330
October	1st to 10th	Day	8% 2 6% 19% 40% 25%	330
	11th to 20th	Day	12% 2 7% 29% 33% 17%	330
	21st to end	Day	11% 6% 17% 29% 26% 11%	363
November	1st to 10th	Day	12% 5% 13% 34% 27% 10%	330
	11th to 20th	Day	18% 4 14% 26% 32% 7%	330
	21st to end	Day	20% 7% 22% 27% 19% 5%	330
December	1st to 10th	Day	18% 5% 22% 25% 23% 7%	330
	11th to 20th	Day	19% 9% 19% 26% 22% 4	321
	21st to end	Day	16% 5% 20% 32% 22% 5%	330
January	1st to 10th	Night	19% 5% 23% 41% 12% 1	1000
	11th to 20th	Night	19% 4 29% 40% 7%	852
	21st to end	Night	18% 7% 26% 41% 7%	880
February	1st to 10th	Night	14% 7% 33% 40% 6% 1	800
	11th to 20th	Night	20% 7% 36% 33% 5%	784
	21st to end	Night	17% 6% 41% 32% 3	660
March	1st to 10th	Night	14% 11% 42% 30% 4	696
	11th to 20th	Night	12% 11% 45% 30% 3	600
	21st to end	Night	11% 8% 52% 28% 2	660
April	1st to 10th	Night	9% 8% 50% 32% 2	600
	11th to 20th	Night	11% 8% 49% 30% 2	593
	21st to end	Night	10% 10% 51% 26% 3	600
May	1st to 10th	Night	9% 9% 49% 31% 3	600
	11th to 20th	Night	8% 6% 47% 37% 3	591
	21st to end	Night	6% 4 47% 38% 5%	650
June	1st to 10th	Night	2 2 27% 60% 9%	600
	11th to 20th	Night	3 1 36% 54% 7% 1	600
	21st to end	Night	4 1 24% 56% 14% 1	600
July	1st to 10th	Night	7% 2 16% 60% 14% 2	585
	11th to 20th	Night	2 2 12% 71% 14%	582
	21st to end	Night	4 1 14% 66% 15%	657
August	1st to 10th	Night	2 1 13% 65% 19% 1	597
	11th to 20th	Night	3 1 11% 67% 17% 1	594
	21st to end	Night	4 1 5% 61% 26% 3	660
September	1st to 10th	Night	10% 2 9% 49% 27% 4	600
	11th to 20th	Night	9% 1 8% 44% 35% 4	600
	21st to end	Night	8% 1 9% 47% 31% 4	600
October	1st to 10th	Night	5% 1 11% 51% 31% 1	600
	11th to 20th	Night	11% 1 15% 49% 23% 1	600
	21st to end	Night	9% 4 23% 43% 20% 1	845
November	1st to 10th	Night	10% 4 22% 42% 22% 1	820
	11th to 20th	Night	13% 3 19% 44% 19% 2	992
	21st to end	Night	17% 5% 22% 38% 16% 1	1050
December	1st to 10th	Night	20% 4 20% 42% 13% 1	1050
	11th to 20th	Night	20% 5% 23% 40% 10%	1036
	21st to end	Night	15% 4 26% 42% 13%	1100

Page generated at 2025-12-15 00:13:52. Version ac07

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