Laguna Niguel
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Laguna Niguel clear sky chart from 2005-11-06 to 2025-08-05.

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 4 1 4 3 3 3 3 5% 7% 63%	130222
	Night	6% 6% 2 5% 3 4 3 3 4 6% 57%	126907
Transparency	Day	20% 5% 8% 19% 26% 22%	129950
	Night	27% 5% 8% 17% 23% 22%	126694
Seeing	Day	6% 4 17% 36% 28% 8%	16846
	Night	8% 3 8% 30% 38% 13%	26755

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% 3 1 3 2 2 3 2 3 5% 70%	4098
	11th to 20th	Day	6% 4 2 4 2 2 3 3 4 5% 65%	4440
	21st to end	Day	10% 4 2 5% 4 4 4 3 5% 9% 50%	5016
February	1st to 10th	Day	10% 4 2 4 4 3 3 4 5% 6% 57%	2000
	11th to 20th	Day	8% 4 2 4 3 3 3 3 5% 8% 58%	1950
	21st to end	Day	9% 6% 2 4 3 3 4 4 5% 6% 55%	1650
March	1st to 10th	Day	8% 6% 2 5% 4 4 4 4 7% 8% 48%	4518
	11th to 20th	Day	8% 5% 1 5% 3 3 4 3 5% 8% 55%	4685
	21st to end	Day	9% 5% 1 4 3 3 4 4 6% 8% 54%	5925
April	1st to 10th	Day	5% 5% 2 3 3 3 4 3 5% 9% 59%	2400
	11th to 20th	Day	4 4 1 5% 3 3 3 3 4 6% 62%	2369
	21st to end	Day	5% 4 1 4 3 3 3 3 5% 8% 63%	2400
May	1st to 10th	Day	3 4 2 4 3 4 4 3 4 6% 64%	5615
	11th to 20th	Day	3 6% 2 6% 4 4 4 3 5% 8% 54%	5841
	21st to end	Day	4 5% 2 5% 4 3 4 3 5% 8% 57%	6423
June	1st to 10th	Day	5% 7% 3 6% 4 3 3 3 5% 8% 55%	2600
	11th to 20th	Day	3 5% 1 3 2 3 3 3 4 7% 66%	2631
	21st to end	Day	2 3 1 4 3 2 3 2 3 5% 71%	2800
July	1st to 10th	Day	1 1 1 2 2 4 3 2 3 5% 77%	6319
	11th to 20th	Day	1 3 1 5% 3 4 3 3 4 6% 67%	5890
	21st to end	Day	1 2 1 2 2 3 3 2 4 6% 74%	6013
August	1st to 10th	Day	1 1 1 2 2 2 2 2 3 6% 77%	3832
	11th to 20th	Day	1 1 1 1 1 2 2 1 3 5% 82%	3724
	21st to end	Day	1 1 1 3 2 2 3 2 3 5% 77%	4180
September	1st to 10th	Day	2 2 1 2 2 2 3 3 4 6% 74%	2280
	11th to 20th	Day	2 2 1 3 2 2 3 3 3 6% 72%	2113
	21st to end	Day	1 2 1 4 3 3 2 2 3 6% 73%	2090
October	1st to 10th	Day	2 2 1 2 2 2 3 2 5% 6% 74%	3490
	11th to 20th	Day	3 6% 3 4 2 3 3 2 4 8% 61%	3356
	21st to end	Day	3 2 1 3 2 3 3 4 5% 7% 66%	3341
November	1st to 10th	Day	4 3 1 2 4 3 2 3 4 6% 69%	1764
	11th to 20th	Day	4 2 1 3 3 3 3 3 5% 6% 68%	1800
	21st to end	Day	5% 4 2 4 3 4 3 4 6% 8% 58%	1800
December	1st to 10th	Day	4 3 1 3 2 4 4 3 6% 9% 62%	2950
	11th to 20th	Day	8% 5% 1 4 3 4 5% 5% 6% 7% 52%	3409
	21st to end	Day	8% 6% 2 7% 6% 6% 5% 4 6% 9% 41%	4510
January	1st to 10th	Night	5% 4 1 3 2 2 3 2 3 6% 68%	5867
	11th to 20th	Night	6% 6% 2 5% 3 3 3 3 3 5% 62%	5550
	21st to end	Night	11% 6% 2 4 3 4 4 3 5% 6% 52%	5984
February	1st to 10th	Night	9% 5% 2 5% 4 3 3 3 4 5% 58%	2400
	11th to 20th	Night	9% 5% 2 4 3 4 4 3 4 5% 57%	2338
	21st to end	Night	11% 5% 1 6% 4 3 4 2 4 5% 53%	1980
March	1st to 10th	Night	13% 8% 2 5% 4 3 4 3 5% 8% 45%	5376
	11th to 20th	Night	10% 7% 2 5% 3 4 4 4 4 7% 50%	5313
	21st to end	Night	11% 11% 3 5% 3 3 4 3 4 5% 48%	5033
April	1st to 10th	Night	8% 8% 2 4 4 4 3 3 5% 7% 52%	2000
	11th to 20th	Night	6% 6% 3 5% 4 3 3 2 4 6% 58%	1979
	21st to end	Night	7% 8% 3 6% 3 3 3 3 5% 6% 53%	2000
May	1st to 10th	Night	7% 12% 3 6% 3 4 3 2 3 5% 54%	4376
	11th to 20th	Night	6% 18% 4 7% 5% 5% 3 3 4 6% 40%	4074
	21st to end	Night	6% 12% 2 7% 4 3 3 3 3 6% 50%	4474
June	1st to 10th	Night	5% 14% 5% 9% 5% 6% 4 4 4 7% 38%	1800
	11th to 20th	Night	2 10% 3 5% 4 5% 4 3 4 8% 51%	1757
	21st to end	Night	2 6% 2 8% 5% 4 4 4 4 7% 54%	1600
July	1st to 10th	Night	1 3 2 5% 3 4 4 3 6% 5% 64%	3640
	11th to 20th	Night	1 6% 2 7% 4 5% 4 3 5% 6% 58%	4072
	21st to end	Night	1 5% 2 3 3 4 3 4 6% 5% 65%	4874
August	1st to 10th	Night	2 2 1 3 2 4 3 2 5% 6% 71%	3206
	11th to 20th	Night	1 2 1 3 3 3 3 2 4 7% 71%	3126
	21st to end	Night	1 3 1 4 3 3 3 2 4 6% 69%	3498
September	1st to 10th	Night	4 4 1 4 2 4 4 2 4 7% 65%	1900
	11th to 20th	Night	3 4 1 3 3 3 2 3 3 4 71%	2066
	21st to end	Night	2 3 2 4 2 5% 3 2 2 5% 71%	2090
October	1st to 10th	Night	2 2 1 2 2 3 4 3 5% 4 72%	3490
	11th to 20th	Night	5% 10% 2 6% 3 4 3 2 3 5% 58%	3579
	21st to end	Night	3 3 1 3 2 3 3 2 4 5% 71%	4211
November	1st to 10th	Night	4 3 1 3 4 3 3 2 3 6% 66%	2535
	11th to 20th	Night	4 3 2 4 3 3 3 2 3 6% 68%	2600
	21st to end	Night	6% 5% 2 5% 4 3 4 3 6% 8% 54%	2600
December	1st to 10th	Night	5% 3 1 4 4 4 3 3 5% 6% 62%	4240
	11th to 20th	Night	8% 6% 2 5% 4 4 4 4 6% 7% 51%	4811
	21st to end	Night	8% 6% 2 6% 5% 5% 5% 4 6% 9% 43%	6468

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	17% 4 5% 23% 28% 24%	4099
	11th to 20th	Day	21% 5% 12% 16% 18% 29%	4440
	21st to end	Day	29% 5% 5% 18% 23% 21%	5016
February	1st to 10th	Day	29% 4 5% 15% 24% 23%	2000
	11th to 20th	Day	25% 4 7% 19% 26% 19%	1960
	21st to end	Day	28% 4 7% 19% 24% 18%	1650
March	1st to 10th	Day	28% 7% 9% 20% 23% 13%	4518
	11th to 20th	Day	25% 6% 11% 29% 20% 10%	4685
	21st to end	Day	27% 5% 13% 30% 17% 7%	5925
April	1st to 10th	Day	23% 5% 11% 27% 23% 12%	2400
	11th to 20th	Day	22% 4 8% 23% 25% 17%	2372
	21st to end	Day	21% 4 12% 27% 26% 10%	2400
May	1st to 10th	Day	19% 7% 11% 25% 29% 10%	5615
	11th to 20th	Day	28% 5% 8% 22% 29% 7%	5844
	21st to end	Day	24% 6% 10% 25% 27% 8%	6424
June	1st to 10th	Day	30% 6% 8% 21% 25% 10%	2600
	11th to 20th	Day	20% 4 5% 17% 29% 24%	2631
	21st to end	Day	20% 2 4 12% 25% 37%	2800
July	1st to 10th	Day	9% 3 6% 11% 18% 53%	6251
	11th to 20th	Day	15% 8% 6% 13% 40% 17%	5820
	21st to end	Day	12% 4 6% 22% 28% 29%	5840
August	1st to 10th	Day	11% 3 4 22% 38% 23%	3819
	11th to 20th	Day	8% 2 4 18% 28% 41%	3760
	21st to end	Day	10% 4 4 12% 32% 38%	4179
September	1st to 10th	Day	14% 3 5% 12% 34% 32%	2280
	11th to 20th	Day	17% 2 4 15% 33% 29%	2113
	21st to end	Day	16% 2 4 16% 33% 28%	2090
October	1st to 10th	Day	12% 3 6% 13% 24% 43%	3490
	11th to 20th	Day	20% 6% 5% 14% 29% 26%	3356
	21st to end	Day	16% 4 4 11% 33% 32%	3341
November	1st to 10th	Day	19% 3 5% 19% 22% 32%	1764
	11th to 20th	Day	18% 3 7% 17% 20% 34%	1800
	21st to end	Day	22% 4 9% 14% 23% 27%	1800
December	1st to 10th	Day	17% 5% 8% 23% 20% 27%	2950
	11th to 20th	Day	29% 5% 9% 17% 27% 14%	3408
	21st to end	Day	36% 9% 12% 22% 14% 7%	4510
January	1st to 10th	Night	18% 4 6% 17% 30% 25%	5867
	11th to 20th	Night	24% 5% 9% 17% 16% 28%	5550
	21st to end	Night	31% 4 7% 13% 22% 23%	5984
February	1st to 10th	Night	28% 4 7% 14% 22% 25%	2400
	11th to 20th	Night	30% 5% 6% 15% 21% 23%	2339
	21st to end	Night	34% 3 5% 14% 22% 22%	1980
March	1st to 10th	Night	33% 7% 11% 18% 21% 11%	5376
	11th to 20th	Night	32% 6% 10% 26% 17% 10%	5313
	21st to end	Night	35% 8% 11% 20% 20% 6%	5033
April	1st to 10th	Night	33% 3 9% 21% 20% 13%	2000
	11th to 20th	Night	29% 4 8% 20% 23% 17%	1979
	21st to end	Night	35% 3 10% 20% 21% 10%	2000
May	1st to 10th	Night	34% 5% 10% 16% 26% 9%	4373
	11th to 20th	Night	43% 6% 9% 16% 20% 5%	4075
	21st to end	Night	36% 4 11% 20% 19% 9%	4474
June	1st to 10th	Night	51% 4 8% 10% 18% 9%	1800
	11th to 20th	Night	34% 4 5% 13% 26% 17%	1757
	21st to end	Night	34% 3 6% 10% 19% 29%	1600
July	1st to 10th	Night	16% 3 5% 16% 13% 47%	3600
	11th to 20th	Night	20% 8% 7% 14% 33% 18%	4019
	21st to end	Night	16% 5% 8% 22% 26% 23%	4735
August	1st to 10th	Night	15% 3 5% 23% 36% 19%	3196
	11th to 20th	Night	14% 3 5% 18% 25% 36%	3156
	21st to end	Night	16% 4 5% 10% 32% 34%	3498
September	1st to 10th	Night	23% 4 5% 10% 29% 30%	1900
	11th to 20th	Night	21% 3 4 10% 30% 32%	2066
	21st to end	Night	20% 2 4 13% 33% 28%	2090
October	1st to 10th	Night	12% 4 6% 14% 23% 40%	3490
	11th to 20th	Night	27% 6% 4 10% 26% 26%	3579
	21st to end	Night	17% 3 3 11% 33% 33%	4211
November	1st to 10th	Night	21% 3 5% 16% 21% 35%	2535
	11th to 20th	Night	21% 2 5% 16% 19% 37%	2600
	21st to end	Night	27% 4 8% 16% 17% 28%	2600
December	1st to 10th	Night	20% 7% 6% 16% 23% 28%	4240
	11th to 20th	Night	32% 4 9% 13% 26% 17%	4811
	21st to end	Night	32% 8% 14% 25% 13% 9%	6468

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	13% 6% 16% 37% 23% 5%	300
	11th to 20th	Day	11% 4 19% 39% 21% 5%	445
	21st to end	Day	9% 9% 22% 33% 23% 4	550
February	1st to 10th	Day	12% 8% 21% 32% 22% 6%	500
	11th to 20th	Day	9% 9% 26% 34% 19% 2	495
	21st to end	Day	8% 9% 29% 34% 17% 2	414
March	1st to 10th	Day	10% 10% 31% 31% 13% 4	500
	11th to 20th	Day	11% 7% 25% 34% 20% 3	500
	21st to end	Day	7% 9% 31% 34% 17% 3	550
April	1st to 10th	Day	7% 6% 25% 36% 20% 6%	500
	11th to 20th	Day	3 9% 29% 36% 18% 5%	492
	21st to end	Day	4 6% 26% 34% 22% 8%	500
May	1st to 10th	Day	6% 5% 26% 35% 22% 5%	503
	11th to 20th	Day	5% 6% 21% 41% 22% 5%	528
	21st to end	Day	7% 7% 22% 39% 22% 4	573
June	1st to 10th	Day	6% 3 16% 37% 33% 6%	530
	11th to 20th	Day	5% 2 17% 37% 30% 9%	530
	21st to end	Day	3 2 10% 37% 38% 10%	530
July	1st to 10th	Day	2 1 5% 33% 46% 13%	526
	11th to 20th	Day	3 1 2 29% 46% 19%	524
	21st to end	Day	3 1 3 33% 43% 18%	575
August	1st to 10th	Day	3 1 5% 34% 41% 16%	504
	11th to 20th	Day	3 6% 30% 44% 17%	477
	21st to end	Day	2 4 36% 42% 15%	539
September	1st to 10th	Day	3 1 6% 42% 34% 13%	490
	11th to 20th	Day	3 3 16% 40% 31% 8%	490
	21st to end	Day	2 1 18% 38% 31% 10%	490
October	1st to 10th	Day	3 2 16% 38% 32% 8%	490
	11th to 20th	Day	5% 2 16% 39% 28% 10%	490
	21st to end	Day	4 4 16% 36% 29% 12%	481
November	1st to 10th	Day	3 5% 17% 31% 33% 10%	300
	11th to 20th	Day	4 3 16% 39% 28% 10%	300
	21st to end	Day	5% 5% 19% 38% 25% 8%	300
December	1st to 10th	Day	8% 5% 13% 38% 30% 6%	300
	11th to 20th	Day	7% 4 16% 35% 29% 10%	300
	21st to end	Day	12% 8% 22% 35% 19% 5%	330
January	1st to 10th	Night	11% 2 11% 38% 27% 10%	800
	11th to 20th	Night	9% 3 11% 37% 31% 10%	800
	21st to end	Night	11% 4 13% 37% 30% 6%	880
February	1st to 10th	Night	11% 3 11% 35% 30% 10%	800
	11th to 20th	Night	10% 3 13% 38% 27% 8%	784
	21st to end	Night	12% 4 12% 41% 26% 5%	660
March	1st to 10th	Night	11% 3 14% 43% 24% 6%	800
	11th to 20th	Night	10% 5% 11% 35% 30% 9%	800
	21st to end	Night	9% 4 11% 36% 34% 6%	880
April	1st to 10th	Night	11% 4 9% 37% 33% 6%	800
	11th to 20th	Night	8% 5% 12% 36% 32% 8%	791
	21st to end	Night	10% 5% 8% 30% 38% 9%	800
May	1st to 10th	Night	11% 4 8% 34% 35% 8%	720
	11th to 20th	Night	12% 4 9% 29% 38% 8%	591
	21st to end	Night	10% 4 9% 31% 38% 8%	650
June	1st to 10th	Night	15% 4 9% 30% 35% 8%	600
	11th to 20th	Night	8% 2 6% 29% 47% 8%	557
	21st to end	Night	12% 1 2 18% 53% 14%	400
July	1st to 10th	Night	8% 2 3 7% 53% 27%	390
	11th to 20th	Night	5% 1 2 10% 55% 28%	568
	21st to end	Night	5% 1 2 10% 54% 29%	828
August	1st to 10th	Night	5% 2 2 13% 53% 26%	772
	11th to 20th	Night	5% 1 1 9% 52% 33%	752
	21st to end	Night	5% 1 1 11% 54% 29%	836
September	1st to 10th	Night	7% 1 3 13% 51% 26%	760
	11th to 20th	Night	5% 3 3 20% 53% 16%	760
	21st to end	Night	4 1 4 27% 48% 17%	760
October	1st to 10th	Night	4 2 4 34% 45% 12%	760
	11th to 20th	Night	8% 2 5% 29% 40% 15%	760
	21st to end	Night	7% 1 7% 29% 39% 17%	836
November	1st to 10th	Night	5% 2 8% 33% 39% 14%	780
	11th to 20th	Night	4 2 5% 36% 39% 14%	800
	21st to end	Night	7% 3 9% 40% 32% 10%	800
December	1st to 10th	Night	10% 2 8% 41% 31% 9%	800
	11th to 20th	Night	13% 4 9% 37% 31% 7%	800
	21st to end	Night	11% 6% 13% 35% 26% 9%	880

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