Cachuma Lake Recreation Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cachuma Lake Recreation Area clear sky chart from 2005-11-06 to 2025-09-19.

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	4 2 1 3 2 2 2 2 4 5% 72%	134209
	Night	4 3 1 3 2 2 3 2 4 6% 70%	132324
Transparency	Day	10% 38% 4 12% 20% 16%	129289
	Night	11% 37% 4 10% 19% 18%	128218
Seeing	Day	8% 11% 26% 34% 17% 4	16790
	Night	6% 6% 20% 34% 28% 6%	26447

By Month

Percentage Cloud Cover SW (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	5% 2 1 3 2 2 3 3 5% 5% 70%	3848
	11th to 20th	Day	7% 3 1 3 2 2 3 2 4 6% 67%	4100
	21st to end	Day	9% 4 1 4 3 4 4 4 6% 8% 52%	4510
February	1st to 10th	Day	11% 6% 2 4 3 2 2 3 5% 5% 58%	1968
	11th to 20th	Day	8% 4 1 3 4 3 3 4 5% 8% 57%	1950
	21st to end	Day	10% 5% 2 4 4 3 4 3 5% 6% 55%	1650
March	1st to 10th	Day	13% 5% 2 4 3 3 4 3 5% 7% 51%	4535
	11th to 20th	Day	9% 4 1 5% 3 3 3 2 3 6% 61%	5000
	21st to end	Day	9% 5% 1 4 3 3 5% 4 7% 9% 50%	5808
April	1st to 10th	Day	6% 3 1 4 3 4 4 4 6% 8% 59%	2400
	11th to 20th	Day	4 4 1 4 3 3 2 3 4 6% 66%	2369
	21st to end	Day	4 3 1 3 3 3 3 3 5% 6% 66%	2400
May	1st to 10th	Day	2 2 1 2 2 2 2 2 4 5% 75%	5440
	11th to 20th	Day	1 2 1 2 3 2 3 3 4 7% 73%	5653
	21st to end	Day	1 1 1 2 2 2 2 2 4 6% 77%	6655
June	1st to 10th	Day	3 2 1 3 3 3 2 2 5% 7% 68%	2800
	11th to 20th	Day	1 2 2 1 1 1 2 3 5% 80%	2800
	21st to end	Day	1 1 1 2 1 2 2 2 3 5% 82%	2800
July	1st to 10th	Day	1 1 1 1 1 2 3 90%	6319
	11th to 20th	Day	1 1 1 2 2 2 2 3 4 82%	5968
	21st to end	Day	1 1 1 2 2 2 1 2 3 5% 82%	6369
August	1st to 10th	Day	1 1 2 1 2 2 2 4 4 81%	5346
	11th to 20th	Day	1 1 1 1 1 1 1 3 90%	5364
	21st to end	Day	1 1 1 1 1 1 2 3 88%	5984
September	1st to 10th	Day	2 1 1 1 2 2 2 3 6% 80%	2400
	11th to 20th	Day	1 1 2 2 2 1 1 3 4 82%	2335
	21st to end	Day	1 1 1 2 1 2 1 3 4 83%	2090
October	1st to 10th	Day	2 1 1 2 1 2 2 2 4 4 80%	3291
	11th to 20th	Day	2 1 2 2 3 2 2 4 4 79%	3161
	21st to end	Day	2 2 1 3 2 3 3 2 4 5% 73%	3448
November	1st to 10th	Day	4 2 1 3 2 3 3 3 3 5% 71%	1851
	11th to 20th	Day	3 4 1 3 3 3 3 3 4 6% 70%	1800
	21st to end	Day	5% 3 2 4 3 3 4 3 5% 7% 61%	1800
December	1st to 10th	Day	5% 3 1 5% 3 3 3 3 5% 6% 63%	2950
	11th to 20th	Day	15% 4 2 5% 3 3 4 3 5% 5% 52%	3043
	21st to end	Day	11% 5% 1 4 4 3 3 3 7% 10% 50%	4004
January	1st to 10th	Night	6% 3 1 4 3 2 3 3 4 6% 65%	6090
	11th to 20th	Night	6% 4 2 4 2 2 3 2 3 6% 66%	5880
	21st to end	Night	10% 5% 1 4 3 3 4 4 5% 8% 54%	6468
February	1st to 10th	Night	10% 6% 2 4 3 2 3 2 4 5% 59%	2429
	11th to 20th	Night	8% 4 1 4 3 3 3 3 6% 7% 59%	2338
	21st to end	Night	9% 4 2 4 4 4 3 3 4 4 59%	1980
March	1st to 10th	Night	9% 6% 2 5% 4 3 5% 4 6% 7% 48%	5343
	11th to 20th	Night	7% 4 2 5% 3 4 3 3 4 6% 59%	5000
	21st to end	Night	10% 4 2 4 3 4 3 3 5% 7% 56%	5165
April	1st to 10th	Night	5% 4 1 3 3 3 3 3 5% 6% 64%	2000
	11th to 20th	Night	4 3 1 3 2 2 2 3 5% 4 70%	1979
	21st to end	Night	2 2 1 3 3 3 2 3 4 8% 70%	2000
May	1st to 10th	Night	1 2 1 2 2 2 2 3 4 5% 76%	4560
	11th to 20th	Night	1 1 1 3 3 2 2 2 3 5% 77%	4268
	21st to end	Night	1 1 1 1 1 1 1 1 2 4 86%	4212
June	1st to 10th	Night	2 1 3 3 4 3 4 5% 8% 68%	1600
	11th to 20th	Night	1 3 2 2 1 2 2 4 5% 80%	1600
	21st to end	Night	1 1 1 2 1 1 1 2 2 4 85%	1600
July	1st to 10th	Night	1 1 1 1 1 2 3 90%	3640
	11th to 20th	Night	1 2 2 4 2 3 4 81%	4002
	21st to end	Night	1 1 2 2 2 1 3 4 83%	4489
August	1st to 10th	Night	1 1 1 1 1 1 3 5% 85%	4486
	11th to 20th	Night	1 1 1 1 1 2 3 91%	4506
	21st to end	Night	1 1 1 1 1 2 2 90%	5015
September	1st to 10th	Night	1 1 2 2 2 2 2 2 3 82%	2000
	11th to 20th	Night	1 1 1 2 1 1 2 1 3 3 83%	2020
	21st to end	Night	1 1 1 1 1 2 3 4 84%	2090
October	1st to 10th	Night	2 1 1 1 1 1 1 2 2 3 85%	3672
	11th to 20th	Night	1 1 1 2 2 2 2 3 3 5% 78%	3777
	21st to end	Night	2 2 1 2 2 1 2 1 3 5% 79%	4121
November	1st to 10th	Night	3 3 1 3 2 2 3 2 4 6% 71%	2445
	11th to 20th	Night	3 3 1 3 2 2 3 3 4 6% 70%	2600
	21st to end	Night	5% 4 1 3 3 4 4 3 5% 7% 61%	2600
December	1st to 10th	Night	4 3 1 3 3 3 4 3 5% 6% 64%	4240
	11th to 20th	Night	13% 4 2 3 3 3 5% 4 6% 8% 50%	5157
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 7% 11% 44%	6952

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	10% 26% 4 23% 25% 13%	3848
	11th to 20th	Day	15% 28% 7% 9% 18% 23%	4100
	21st to end	Day	19% 29% 6% 14% 20% 12%	4510
February	1st to 10th	Day	14% 61% 4 8% 8% 6%	1968
	11th to 20th	Day	10% 61% 3 8% 11% 7%	1960
	21st to end	Day	10% 62% 2 7% 12% 6%	1650
March	1st to 10th	Day	24% 29% 7% 14% 20% 6%	4535
	11th to 20th	Day	19% 28% 8% 21% 18% 7%	5000
	21st to end	Day	20% 32% 9% 23% 14% 1	5808
April	1st to 10th	Day	9% 63% 4 9% 11% 4	2400
	11th to 20th	Day	7% 63% 3 9% 14% 4	2372
	21st to end	Day	7% 62% 5% 11% 12% 3	2400
May	1st to 10th	Day	8% 29% 5% 22% 24% 10%	5440
	11th to 20th	Day	6% 33% 8% 17% 28% 7%	5656
	21st to end	Day	5% 30% 5% 28% 26% 6%	6656
June	1st to 10th	Day	5% 63% 3 12% 13% 4	2800
	11th to 20th	Day	4 61% 1 9% 15% 11%	2800
	21st to end	Day	6% 59% 2 5% 15% 14%	2800
July	1st to 10th	Day	3 24% 1 5% 15% 52%	6251
	11th to 20th	Day	7% 24% 4 4 24% 38%	5897
	21st to end	Day	4 24% 3 14% 31% 24%	6184
August	1st to 10th	Day	5% 34% 2 8% 30% 21%	3890
	11th to 20th	Day	2 35% 1 3 24% 35%	3880
	21st to end	Day	3 34% 1 7% 22% 32%	4311
September	1st to 10th	Day	6% 57% 2 4 17% 14%	2400
	11th to 20th	Day	6% 57% 2 8% 19% 9%	2335
	21st to end	Day	3 59% 2 7% 18% 11%	2090
October	1st to 10th	Day	4 35% 1 5% 13% 41%	3291
	11th to 20th	Day	5% 37% 3 14% 26% 14%	3161
	21st to end	Day	11% 35% 2 4 29% 19%	3448
November	1st to 10th	Day	4 55% 1 8% 16% 15%	1851
	11th to 20th	Day	9% 58% 3 8% 10% 12%	1800
	21st to end	Day	11% 57% 4 8% 10% 10%	1800
December	1st to 10th	Day	15% 35% 2 9% 22% 18%	2950
	11th to 20th	Day	24% 31% 5% 11% 17% 12%	3043
	21st to end	Day	21% 28% 9% 21% 16% 5%	4004
January	1st to 10th	Night	14% 27% 4 16% 24% 15%	6090
	11th to 20th	Night	16% 29% 4 9% 16% 25%	5880
	21st to end	Night	20% 30% 5% 11% 20% 14%	6468
February	1st to 10th	Night	14% 62% 3 6% 8% 7%	2429
	11th to 20th	Night	9% 61% 3 6% 13% 8%	2339
	21st to end	Night	9% 61% 2 7% 13% 8%	1980
March	1st to 10th	Night	24% 31% 6% 13% 21% 5%	5343
	11th to 20th	Night	18% 30% 8% 18% 18% 8%	5000
	21st to end	Night	21% 30% 10% 19% 18% 2	5165
April	1st to 10th	Night	9% 63% 4 11% 10% 4	2000
	11th to 20th	Night	7% 63% 4 7% 14% 5%	1979
	21st to end	Night	5% 62% 5% 12% 11% 4	2000
May	1st to 10th	Night	8% 30% 9% 16% 24% 14%	4557
	11th to 20th	Night	6% 30% 7% 17% 25% 15%	4269
	21st to end	Night	2 30% 5% 17% 32% 13%	4212
June	1st to 10th	Night	7% 62% 4 8% 13% 6%	1600
	11th to 20th	Night	4 61% 1 4 16% 14%	1600
	21st to end	Night	6% 59% 2 4 12% 18%	1600
July	1st to 10th	Night	2 24% 1 4 11% 58%	3600
	11th to 20th	Night	5% 24% 7% 3 19% 42%	3951
	21st to end	Night	4 24% 3 11% 25% 33%	4362
August	1st to 10th	Night	5% 34% 1 8% 25% 26%	3256
	11th to 20th	Night	2 34% 1 2 17% 44%	3256
	21st to end	Night	2 34% 1 4 19% 39%	3608
September	1st to 10th	Night	6% 56% 2 4 15% 18%	2000
	11th to 20th	Night	5% 57% 2 6% 17% 13%	2020
	21st to end	Night	3 59% 2 4 19% 13%	2090
October	1st to 10th	Night	2 35% 1 4 14% 44%	3672
	11th to 20th	Night	4 36% 3 11% 24% 21%	3777
	21st to end	Night	7% 35% 2 5% 29% 22%	4121
November	1st to 10th	Night	4 55% 2 7% 16% 17%	2445
	11th to 20th	Night	8% 57% 3 6% 11% 14%	2600
	21st to end	Night	12% 57% 4 9% 8% 10%	2600
December	1st to 10th	Night	12% 35% 3 10% 21% 18%	4240
	11th to 20th	Night	21% 32% 6% 11% 18% 12%	5157
	21st to end	Night	25% 29% 9% 18% 17% 3	6952

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	18% 14% 31% 23% 12% 2	292
	11th to 20th	Day	16% 15% 27% 28% 12% 2	400
	21st to end	Day	13% 14% 35% 25% 10% 2	440
February	1st to 10th	Day	15% 16% 27% 24% 15% 4	485
	11th to 20th	Day	18% 17% 29% 25% 9% 2	495
	21st to end	Day	13% 18% 33% 26% 8% 2	414
March	1st to 10th	Day	22% 20% 31% 21% 6% 1	500
	11th to 20th	Day	16% 21% 32% 24% 6% 1	500
	21st to end	Day	17% 22% 33% 22% 6% 1	550
April	1st to 10th	Day	12% 18% 31% 25% 12% 2	500
	11th to 20th	Day	10% 20% 36% 24% 8% 2	492
	21st to end	Day	7% 18% 33% 26% 13% 3	500
May	1st to 10th	Day	11% 15% 32% 27% 11% 3	503
	11th to 20th	Day	6% 14% 34% 30% 14% 2	528
	21st to end	Day	8% 12% 32% 33% 12% 2	573
June	1st to 10th	Day	5% 8% 27% 37% 21% 2	530
	11th to 20th	Day	4 8% 29% 36% 18% 5%	530
	21st to end	Day	2 4 22% 43% 23% 5%	530
July	1st to 10th	Day	1 1 18% 47% 26% 7%	526
	11th to 20th	Day	2 1 11% 44% 32% 10%	524
	21st to end	Day	1 1 14% 46% 28% 11%	575
August	1st to 10th	Day	2 2 20% 46% 24% 6%	527
	11th to 20th	Day	2 1 15% 45% 30% 7%	517
	21st to end	Day	1 2 15% 48% 27% 6%	583
September	1st to 10th	Day	3 3 20% 45% 22% 7%	530
	11th to 20th	Day	3 6% 29% 43% 14% 4	523
	21st to end	Day	1 7% 24% 42% 22% 4	490
October	1st to 10th	Day	4 10% 24% 38% 23% 2	490
	11th to 20th	Day	4 8% 29% 38% 18% 4	490
	21st to end	Day	6% 9% 27% 35% 20% 4	539
November	1st to 10th	Day	7% 10% 26% 33% 21% 4	387
	11th to 20th	Day	8% 8% 26% 38% 15% 4	300
	21st to end	Day	8% 10% 25% 34% 19% 3	300
December	1st to 10th	Day	10% 10% 27% 33% 17% 3	300
	11th to 20th	Day	13% 14% 23% 29% 16% 6%	207
	21st to end	Day	20% 15% 32% 21% 9% 2	220
January	1st to 10th	Night	12% 8% 25% 30% 16% 9%	800
	11th to 20th	Night	8% 6% 26% 33% 19% 8%	800
	21st to end	Night	10% 9% 27% 33% 15% 5%	880
February	1st to 10th	Night	13% 6% 24% 31% 21% 5%	800
	11th to 20th	Night	10% 11% 26% 31% 17% 6%	784
	21st to end	Night	10% 10% 28% 33% 17% 2	660
March	1st to 10th	Night	12% 11% 25% 35% 14% 2	800
	11th to 20th	Night	10% 9% 24% 33% 20% 3	800
	21st to end	Night	10% 11% 28% 33% 16% 2	880
April	1st to 10th	Night	9% 8% 30% 32% 18% 2	800
	11th to 20th	Night	6% 10% 28% 33% 19% 4	791
	21st to end	Night	3 10% 30% 31% 21% 6%	800
May	1st to 10th	Night	5% 8% 22% 36% 25% 4	800
	11th to 20th	Night	4 7% 21% 36% 28% 3	681
	21st to end	Night	3 8% 26% 35% 26% 2	544
June	1st to 10th	Night	1 5% 15% 38% 40% 3	400
	11th to 20th	Night	2 2 14% 40% 38% 5%	400
	21st to end	Night	1 1 12% 34% 46% 6%	400
July	1st to 10th	Night	8% 30% 52% 10%	390
	11th to 20th	Night	1 2 22% 58% 17%	539
	21st to end	Night	1 4 24% 54% 17%	662
August	1st to 10th	Night	2 8% 35% 46% 9%	796
	11th to 20th	Night	1 5% 29% 54% 11%	792
	21st to end	Night	1 1 5% 31% 51% 11%	880
September	1st to 10th	Night	2 2 8% 34% 45% 9%	800
	11th to 20th	Night	2 3 14% 39% 34% 8%	792
	21st to end	Night	1 2 12% 38% 39% 8%	760
October	1st to 10th	Night	3 3 14% 41% 34% 4	760
	11th to 20th	Night	4 4 17% 40% 29% 7%	760
	21st to end	Night	3 4 20% 35% 29% 9%	836
November	1st to 10th	Night	5% 5% 21% 36% 25% 9%	780
	11th to 20th	Night	6% 5% 20% 39% 25% 6%	800
	21st to end	Night	6% 6% 23% 38% 20% 7%	800
December	1st to 10th	Night	9% 6% 21% 34% 24% 6%	800
	11th to 20th	Night	11% 7% 24% 36% 18% 4	800
	21st to end	Night	10% 12% 25% 34% 15% 5%	880

Page generated at 2025-09-15 22:49:12. Version ac07

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