Los Gatos B&B
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Los Gatos B&B clear sky chart from 2005-11-06 to 2026-06-01.

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	13% 10% 4 10% 6% 5% 5% 4 6% 7% 29%	132466
	Night	13% 11% 4 10% 6% 5% 5% 4 6% 7% 29%	130663
Transparency	Day	51% 8% 12% 19% 10% 1	136022
	Night	51% 8% 13% 18% 9% 1	135194
Seeing	Day	21% 17% 30% 20% 9% 3	16580
	Night	20% 16% 30% 24% 9% 1	25932

By Month

Percentage Cloud Cover NE (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	12% 19% 6% 18% 9% 6% 5% 3 4 3 15%	4661
	11th to 20th	Day	9% 16% 7% 17% 10% 8% 6% 4 5% 4 13%	4788
	21st to end	Day	10% 13% 7% 13% 12% 9% 8% 4 5% 5% 15%	5780
February	1st to 10th	Day	14% 16% 6% 12% 9% 6% 6% 4 4 4 19%	1890
	11th to 20th	Day	11% 17% 7% 17% 8% 6% 5% 3 4 4 18%	1843
	21st to end	Day	17% 15% 4 13% 8% 5% 4 3 4 6% 21%	1720
March	1st to 10th	Day	16% 13% 5% 11% 7% 4 4 3 4 5% 29%	4825
	11th to 20th	Day	9% 15% 5% 9% 5% 4 5% 3 5% 7% 33%	5090
	21st to end	Day	12% 11% 5% 13% 7% 6% 4 4 4 6% 27%	5743
April	1st to 10th	Day	15% 14% 4 8% 7% 5% 4 3 6% 6% 28%	2520
	11th to 20th	Day	16% 11% 4 8% 5% 4 4 4 5% 5% 32%	2494
	21st to end	Day	17% 10% 4 8% 5% 5% 4 4 5% 6% 32%	2604
May	1st to 10th	Day	25% 9% 3 7% 5% 5% 5% 3 5% 5% 28%	6249
	11th to 20th	Day	13% 10% 4 10% 6% 5% 5% 4 6% 7% 31%	6458
	21st to end	Day	17% 8% 3 8% 5% 5% 5% 4 6% 7% 32%	7103
June	1st to 10th	Day	15% 7% 3 7% 5% 5% 5% 5% 6% 8% 35%	2800
	11th to 20th	Day	13% 6% 2 7% 5% 6% 5% 5% 7% 8% 35%	2800
	21st to end	Day	11% 6% 2 7% 5% 6% 6% 5% 7% 9% 37%	2800
July	1st to 10th	Day	9% 5% 3 7% 5% 5% 6% 4 8% 10% 39%	6360
	11th to 20th	Day	6% 5% 2 7% 6% 5% 7% 6% 9% 11% 35%	6360
	21st to end	Day	9% 5% 2 7% 5% 5% 6% 4 7% 8% 43%	6791
August	1st to 10th	Day	15% 6% 3 7% 5% 5% 5% 4 6% 8% 35%	4234
	11th to 20th	Day	12% 8% 2 8% 6% 7% 7% 5% 8% 9% 29%	4123
	21st to end	Day	10% 6% 3 8% 5% 5% 5% 4 7% 9% 37%	4312
September	1st to 10th	Day	14% 6% 2 6% 4 5% 5% 4 6% 8% 40%	2400
	11th to 20th	Day	12% 6% 3 6% 4 5% 4 3 6% 7% 45%	2400
	21st to end	Day	17% 7% 2 7% 6% 4 6% 4 6% 7% 33%	2106
October	1st to 10th	Day	17% 6% 3 8% 4 4 4 4 7% 7% 37%	2000
	11th to 20th	Day	18% 9% 3 8% 5% 5% 5% 4 6% 7% 30%	2000
	21st to end	Day	21% 12% 4 9% 5% 5% 5% 3 5% 7% 26%	2170
November	1st to 10th	Day	12% 13% 3 9% 6% 6% 5% 4 4 6% 33%	1851
	11th to 20th	Day	11% 15% 4 10% 6% 6% 5% 4 6% 7% 26%	1717
	21st to end	Day	16% 15% 4 12% 6% 5% 5% 4 6% 6% 21%	1680
December	1st to 10th	Day	15% 19% 6% 14% 7% 5% 5% 5% 6% 5% 13%	2680
	11th to 20th	Day	17% 13% 6% 14% 7% 5% 4 3 5% 5% 21%	3066
	21st to end	Day	17% 17% 5% 14% 8% 6% 5% 3 5% 6% 13%	4048
January	1st to 10th	Night	12% 15% 6% 18% 8% 6% 5% 4 4 5% 16%	8234
	11th to 20th	Night	8% 18% 6% 15% 9% 6% 6% 5% 6% 6% 15%	8080
	21st to end	Night	11% 12% 4 11% 9% 7% 8% 4 7% 7% 20%	8401
February	1st to 10th	Night	13% 16% 5% 12% 7% 5% 5% 4 6% 4 22%	2730
	11th to 20th	Night	11% 12% 6% 14% 9% 7% 6% 4 5% 6% 21%	2663
	21st to end	Night	14% 12% 4 14% 6% 5% 6% 4 6% 6% 22%	2085
March	1st to 10th	Night	14% 9% 5% 11% 7% 6% 5% 4 6% 7% 28%	5231
	11th to 20th	Night	13% 14% 5% 9% 5% 4 4 3 4 7% 33%	5089
	21st to end	Night	15% 11% 5% 10% 6% 5% 6% 4 5% 6% 27%	5430
April	1st to 10th	Night	17% 12% 4 7% 5% 5% 5% 4 5% 7% 29%	2100
	11th to 20th	Night	17% 11% 3 7% 4 4 4 3 5% 6% 35%	2075
	21st to end	Night	15% 8% 3 8% 5% 4 4 4 6% 7% 36%	2032
May	1st to 10th	Night	28% 10% 3 7% 4 4 4 3 5% 6% 25%	3909
	11th to 20th	Night	13% 9% 3 7% 5% 4 5% 4 7% 8% 36%	3655
	21st to end	Night	16% 7% 3 7% 5% 4 5% 4 6% 8% 35%	4014
June	1st to 10th	Night	14% 7% 3 7% 4 4 6% 3 6% 9% 38%	1600
	11th to 20th	Night	9% 6% 2 7% 5% 4 5% 5% 6% 9% 42%	1600
	21st to end	Night	9% 6% 2 6% 5% 4 5% 5% 6% 9% 43%	1600
July	1st to 10th	Night	6% 7% 3 7% 5% 5% 5% 4 6% 11% 40%	3600
	11th to 20th	Night	8% 4 2 6% 5% 4 5% 5% 6% 9% 45%	3600
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 6% 8% 48%	4056
August	1st to 10th	Night	14% 6% 3 7% 3 5% 4 4 7% 8% 39%	2915
	11th to 20th	Night	14% 6% 2 7% 5% 4 5% 4 5% 8% 41%	2893
	21st to end	Night	8% 4 2 6% 5% 4 5% 4 7% 9% 45%	3586
September	1st to 10th	Night	12% 6% 2 5% 4 4 5% 3 5% 8% 46%	2000
	11th to 20th	Night	12% 4 3 7% 4 4 5% 4 5% 6% 47%	2000
	21st to end	Night	14% 9% 2 5% 5% 4 5% 5% 6% 7% 37%	2290
October	1st to 10th	Night	15% 8% 3 7% 5% 4 4 3 6% 6% 39%	2400
	11th to 20th	Night	17% 9% 3 6% 5% 4 4 4 6% 7% 35%	2400
	21st to end	Night	22% 9% 3 8% 5% 5% 4 3 5% 6% 29%	2669
November	1st to 10th	Night	13% 11% 3 7% 6% 4 5% 4 5% 6% 36%	2667
	11th to 20th	Night	15% 11% 4 8% 6% 5% 5% 4 6% 7% 29%	2901
	21st to end	Night	14% 13% 4 9% 6% 6% 6% 4 6% 7% 24%	2940
December	1st to 10th	Night	11% 15% 6% 15% 8% 7% 6% 4 6% 7% 16%	4720
	11th to 20th	Night	16% 15% 5% 11% 6% 5% 5% 3 5% 5% 23%	5348
	21st to end	Night	20% 18% 5% 11% 7% 5% 4 3 5% 5% 16%	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	71% 6% 10% 11% 3	4662
	11th to 20th	Day	68% 8% 8% 9% 5% 1	4818
	21st to end	Day	68% 7% 10% 12% 4	5780
February	1st to 10th	Day	68% 6% 9% 12% 4	1890
	11th to 20th	Day	69% 5% 7% 14% 4	1852
	21st to end	Day	64% 5% 10% 15% 6% 1	1720
March	1st to 10th	Day	57% 5% 11% 18% 9%	4828
	11th to 20th	Day	50% 7% 18% 16% 9% 1	5090
	21st to end	Day	56% 7% 7% 20% 9% 1	5743
April	1st to 10th	Day	56% 5% 10% 18% 9% 2	2520
	11th to 20th	Day	52% 7% 10% 17% 13% 1	2494
	21st to end	Day	51% 6% 9% 19% 13% 2	2604
May	1st to 10th	Day	56% 7% 9% 15% 11% 2	6258
	11th to 20th	Day	50% 9% 10% 19% 11% 1	6462
	21st to end	Day	48% 9% 11% 21% 10% 2	7103
June	1st to 10th	Day	45% 8% 11% 20% 15% 1	2800
	11th to 20th	Day	42% 9% 15% 22% 11% 1	2800
	21st to end	Day	41% 9% 14% 21% 14% 1	2800
July	1st to 10th	Day	37% 9% 13% 27% 13% 1	6290
	11th to 20th	Day	35% 11% 17% 23% 13% 1	6285
	21st to end	Day	36% 9% 12% 26% 15%	6596
August	1st to 10th	Day	44% 8% 14% 21% 12% 1	4221
	11th to 20th	Day	45% 10% 15% 24% 6%	4162
	21st to end	Day	40% 7% 12% 32% 7% 1	4312
September	1st to 10th	Day	40% 8% 12% 27% 12% 1	2400
	11th to 20th	Day	37% 6% 12% 28% 16% 1	2400
	21st to end	Day	47% 8% 12% 20% 11% 1	2106
October	1st to 10th	Day	37% 7% 14% 27% 15% 1	3260
	11th to 20th	Day	46% 6% 13% 20% 15%	3240
	21st to end	Day	43% 6% 15% 26% 9% 1	3484
November	1st to 10th	Day	51% 8% 12% 17% 10% 2	1851
	11th to 20th	Day	55% 8% 13% 16% 7% 2	1717
	21st to end	Day	61% 8% 15% 14% 3	1680
December	1st to 10th	Day	67% 9% 11% 10% 2	2680
	11th to 20th	Day	63% 7% 13% 11% 6%	3066
	21st to end	Day	69% 8% 12% 9% 2	4048
January	1st to 10th	Night	66% 9% 10% 11% 5%	8234
	11th to 20th	Night	64% 8% 10% 11% 6% 1	8125
	21st to end	Night	58% 8% 10% 14% 9% 1	8401
February	1st to 10th	Night	62% 7% 12% 14% 5%	2730
	11th to 20th	Night	63% 6% 12% 14% 5% 1	2665
	21st to end	Night	59% 8% 12% 13% 8% 1	2085
March	1st to 10th	Night	53% 7% 15% 17% 8%	5241
	11th to 20th	Night	50% 7% 17% 17% 6% 3	5090
	21st to end	Night	53% 8% 10% 18% 10% 1	5430
April	1st to 10th	Night	53% 6% 12% 18% 9% 1	2100
	11th to 20th	Night	50% 7% 11% 18% 13% 1	2075
	21st to end	Night	45% 6% 12% 21% 13% 3	2032
May	1st to 10th	Night	59% 7% 9% 15% 8% 3	3916
	11th to 20th	Night	44% 10% 14% 20% 11% 1	3656
	21st to end	Night	43% 10% 14% 18% 13% 2	4015
June	1st to 10th	Night	42% 7% 11% 24% 14% 1	1600
	11th to 20th	Night	36% 10% 15% 23% 13% 2	1600
	21st to end	Night	36% 10% 13% 25% 15% 2	1600
July	1st to 10th	Night	36% 8% 15% 25% 13% 1	3560
	11th to 20th	Night	32% 10% 15% 27% 15% 1	3552
	21st to end	Night	32% 8% 12% 27% 19% 2	3937
August	1st to 10th	Night	40% 9% 14% 25% 11% 1	2904
	11th to 20th	Night	41% 8% 15% 28% 9%	2920
	21st to end	Night	32% 9% 14% 33% 11% 1	3586
September	1st to 10th	Night	34% 9% 16% 26% 13% 2	2000
	11th to 20th	Night	34% 7% 13% 29% 16% 1	2000
	21st to end	Night	44% 8% 14% 21% 12% 1	2290
October	1st to 10th	Night	42% 7% 12% 25% 13% 1	3920
	11th to 20th	Night	41% 7% 14% 22% 13% 3	3899
	21st to end	Night	41% 6% 15% 27% 10% 1	4305
November	1st to 10th	Night	47% 8% 11% 22% 10% 2	2667
	11th to 20th	Night	51% 8% 14% 18% 8% 2	2901
	21st to end	Night	57% 9% 16% 15% 4	2940
December	1st to 10th	Night	65% 9% 14% 11% 2	4720
	11th to 20th	Night	61% 6% 10% 14% 8%	5348
	21st to end	Night	68% 8% 9% 11% 4	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	27% 25% 33% 10% 4	220
	11th to 20th	Day	31% 27% 33% 7% 1	245
	21st to end	Day	26% 26% 36% 9% 2	363
February	1st to 10th	Day	32% 29% 28% 9% 2	330
	11th to 20th	Day	33% 27% 34% 6%	330
	21st to end	Day	32% 24% 32% 12%	436
March	1st to 10th	Day	27% 24% 29% 15% 3	540
	11th to 20th	Day	29% 25% 30% 13% 4	540
	21st to end	Day	31% 21% 31% 12% 5% 1	594
April	1st to 10th	Day	30% 23% 29% 13% 4 1	540
	11th to 20th	Day	27% 25% 28% 12% 7% 2	532
	21st to end	Day	26% 18% 30% 18% 6% 1	540
May	1st to 10th	Day	26% 19% 30% 15% 8% 2	543
	11th to 20th	Day	17% 16% 32% 23% 10% 2	567
	21st to end	Day	17% 13% 30% 23% 13% 3	617
June	1st to 10th	Day	18% 14% 31% 23% 11% 2	530
	11th to 20th	Day	13% 13% 30% 30% 12% 3	530
	21st to end	Day	13% 14% 34% 27% 8% 3	530
July	1st to 10th	Day	10% 7% 29% 33% 16% 5%	525
	11th to 20th	Day	10% 7% 25% 32% 20% 5%	524
	21st to end	Day	11% 7% 31% 33% 13% 4	576
August	1st to 10th	Day	10% 7% 24% 31% 20% 8%	526
	11th to 20th	Day	13% 7% 29% 26% 17% 8%	519
	21st to end	Day	11% 10% 28% 26% 15% 10%	583
September	1st to 10th	Day	17% 11% 23% 23% 16% 9%	530
	11th to 20th	Day	10% 8% 22% 27% 21% 12%	530
	21st to end	Day	19% 13% 27% 22% 15% 4	530
October	1st to 10th	Day	19% 11% 30% 20% 14% 6%	530
	11th to 20th	Day	25% 18% 28% 21% 7% 2	530
	21st to end	Day	27% 19% 32% 19% 4	566
November	1st to 10th	Day	23% 21% 30% 17% 8% 1	425
	11th to 20th	Day	24% 26% 30% 16% 3 1	257
	21st to end	Day	28% 31% 30% 10% 1	220
December	1st to 10th	Day	32% 18% 35% 11% 3 1	220
	11th to 20th	Day	34% 26% 29% 10%	220
	21st to end	Day	31% 20% 35% 12% 1	242
January	1st to 10th	Night	23% 26% 33% 15% 2	840
	11th to 20th	Night	24% 24% 32% 17% 3 1	840
	21st to end	Night	19% 24% 36% 18% 3	924
February	1st to 10th	Night	24% 22% 33% 19% 1	840
	11th to 20th	Night	23% 24% 36% 16% 2	823
	21st to end	Night	26% 23% 33% 17% 2	692
March	1st to 10th	Night	23% 20% 35% 19% 3	840
	11th to 20th	Night	25% 22% 30% 20% 3	840
	21st to end	Night	24% 20% 31% 19% 6%	924
April	1st to 10th	Night	25% 20% 31% 21% 3	840
	11th to 20th	Night	24% 15% 32% 22% 6% 1	831
	21st to end	Night	19% 13% 32% 28% 8%	772
May	1st to 10th	Night	22% 12% 24% 32% 10% 1	526
	11th to 20th	Night	14% 9% 34% 34% 8% 1	414
	21st to end	Night	13% 7% 31% 33% 16%	455
June	1st to 10th	Night	16% 6% 30% 31% 16% 1	400
	11th to 20th	Night	11% 10% 26% 39% 15%	400
	21st to end	Night	11% 9% 26% 41% 12% 1	400
July	1st to 10th	Night	8% 4 22% 44% 20% 2	390
	11th to 20th	Night	10% 2 24% 41% 22% 1	388
	21st to end	Night	10% 4 22% 44% 17% 2	493
August	1st to 10th	Night	10% 3 22% 39% 22% 3	597
	11th to 20th	Night	11% 5% 20% 35% 26% 3	599
	21st to end	Night	11% 6% 22% 37% 23% 2	880
September	1st to 10th	Night	13% 9% 23% 33% 20% 3	800
	11th to 20th	Night	13% 7% 20% 29% 27% 5%	800
	21st to end	Night	16% 10% 26% 27% 17% 3	800
October	1st to 10th	Night	18% 12% 29% 21% 18% 2	800
	11th to 20th	Night	21% 16% 30% 26% 8% 1	800
	21st to end	Night	29% 14% 32% 23% 3	880
November	1st to 10th	Night	23% 16% 31% 23% 7%	820
	11th to 20th	Night	24% 20% 31% 19% 5% 2	840
	21st to end	Night	22% 23% 29% 21% 4	840
December	1st to 10th	Night	26% 22% 33% 16% 3	840
	11th to 20th	Night	25% 23% 32% 17% 3	840
	21st to end	Night	27% 22% 34% 15% 2	924

Page generated at 2026-05-29 01:53:29. Version ac07

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