Pfeiffer Big Sur State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pfeiffer Big Sur State Park clear sky chart from 2005-11-06 to 2026-03-03.

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	7% 4 1 3 2 2 2 2 4 6% 66%	139515
	Night	8% 5% 1 4 2 2 3 2 4 7% 61%	139165
Transparency	Day	19% 5% 6% 17% 26% 27%	134487
	Night	22% 4 6% 15% 24% 28%	135178
Seeing	Day	10% 9% 23% 32% 21% 5%	17247
	Night	9% 6% 17% 31% 28% 10%	26804

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	17% 6% 2 5% 3 2 3 3 4 6% 48%	5219
	11th to 20th	Day	10% 4 1 5% 3 3 3 3 4 5% 60%	5340
	21st to end	Day	12% 8% 3 6% 4 4 4 3 5% 7% 44%	5843
February	1st to 10th	Day	19% 8% 2 4 2 3 4 3 3 5% 48%	1890
	11th to 20th	Day	16% 7% 3 5% 4 4 4 4 4 6% 44%	2000
	21st to end	Day	13% 8% 2 7% 4 4 3 3 5% 6% 43%	1730
March	1st to 10th	Day	13% 10% 4 10% 4 5% 5% 4 6% 7% 33%	4879
	11th to 20th	Day	14% 6% 2 6% 3 3 3 2 4 6% 50%	5000
	21st to end	Day	14% 8% 3 6% 3 4 4 4 7% 9% 37%	5603
April	1st to 10th	Day	12% 8% 2 5% 3 3 4 4 5% 7% 48%	2400
	11th to 20th	Day	8% 5% 2 3 3 3 3 4 6% 8% 54%	2369
	21st to end	Day	6% 4 2 4 3 3 3 4 6% 8% 58%	2400
May	1st to 10th	Day	4 2 1 2 1 1 1 2 3 7% 74%	5440
	11th to 20th	Day	2 1 1 2 1 1 2 2 7% 7% 74%	5807
	21st to end	Day	2 2 1 1 1 1 2 4 5% 79%	6902
June	1st to 10th	Day	3 2 1 3 2 2 2 3 4 9% 69%	2800
	11th to 20th	Day	1 1 1 1 1 1 2 5% 6% 79%	2800
	21st to end	Day	2 1 1 1 1 1 2 2 3 86%	2800
July	1st to 10th	Day	1 1 2 5% 90%	6173
	11th to 20th	Day	1 1 1 1 1 1 3 10% 82%	5880
	21st to end	Day	1 1 1 2 2 3 5% 84%	6402
August	1st to 10th	Day	1 1 1 1 1 2 2 3 3 86%	5777
	11th to 20th	Day	1 1 1 1 2 92%	5371
	21st to end	Day	1 1 1 1 1 1 2 5% 87%	5984
September	1st to 10th	Day	1 1 1 1 1 1 1 2 4 87%	2400
	11th to 20th	Day	2 2 1 2 1 1 2 2 4 6% 78%	2400
	21st to end	Day	3 2 1 2 1 2 1 2 4 5% 77%	2140
October	1st to 10th	Day	2 2 1 3 2 2 2 2 4 6% 74%	3280
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 4 78%	3261
	21st to end	Day	5% 3 1 4 2 3 3 3 6% 6% 64%	3558
November	1st to 10th	Day	9% 5% 1 4 3 2 3 2 6% 6% 60%	2050
	11th to 20th	Day	11% 4 1 4 3 3 3 3 5% 8% 54%	1890
	21st to end	Day	12% 5% 1 4 3 3 3 3 5% 5% 56%	1827
December	1st to 10th	Day	9% 6% 2 4 3 3 3 3 6% 8% 53%	2700
	11th to 20th	Day	24% 7% 2 4 3 3 4 3 4 7% 39%	3108
	21st to end	Day	23% 10% 2 6% 3 4 4 4 6% 7% 32%	4092
January	1st to 10th	Night	17% 7% 2 6% 2 2 3 2 4 8% 46%	7684
	11th to 20th	Night	11% 5% 1 4 2 2 3 3 5% 7% 57%	7650
	21st to end	Night	13% 8% 3 7% 3 3 3 3 5% 6% 46%	8371
February	1st to 10th	Night	17% 7% 2 5% 3 4 3 3 4 5% 48%	2730
	11th to 20th	Night	15% 7% 2 4 4 3 4 3 5% 8% 44%	2506
	21st to end	Night	12% 9% 2 6% 4 3 3 3 4 7% 47%	2076
March	1st to 10th	Night	18% 10% 3 10% 5% 4 4 3 4 6% 32%	5056
	11th to 20th	Night	13% 7% 2 5% 3 3 3 3 4 7% 49%	5000
	21st to end	Night	17% 12% 2 7% 3 2 3 3 4 8% 38%	5370
April	1st to 10th	Night	10% 7% 2 6% 4 3 4 4 5% 7% 49%	2000
	11th to 20th	Night	8% 6% 2 5% 3 3 2 3 5% 7% 56%	1979
	21st to end	Night	6% 4 2 4 3 2 3 3 6% 10% 57%	2000
May	1st to 10th	Night	2 3 1 4 2 1 2 2 4 6% 73%	4560
	11th to 20th	Night	1 1 1 3 1 2 2 2 8% 8% 71%	4087
	21st to end	Night	1 2 1 1 1 1 1 2 3 5% 82%	3972
June	1st to 10th	Night	2 2 1 2 1 2 3 3 5% 9% 70%	1600
	11th to 20th	Night	1 1 1 2 1 2 1 2 4 8% 77%	1600
	21st to end	Night	1 1 1 1 1 2 4 5% 85%	1600
July	1st to 10th	Night	1 4 5% 90%	3774
	11th to 20th	Night	1 1 1 1 1 5% 14% 76%	4100
	21st to end	Night	1 1 1 2 2 4 5% 82%	4472
August	1st to 10th	Night	1 1 1 1 1 1 2 3 5% 85%	4035
	11th to 20th	Night	1 1 1 3 93%	4497
	21st to end	Night	1 1 1 1 1 1 1 3 5% 85%	5015
September	1st to 10th	Night	1 1 1 1 1 1 2 5% 85%	2000
	11th to 20th	Night	3 2 1 2 2 1 1 2 3 5% 79%	2000
	21st to end	Night	3 1 1 2 2 1 1 2 3 5% 80%	2256
October	1st to 10th	Night	3 2 1 3 1 2 2 2 4 6% 75%	3920
	11th to 20th	Night	2 2 1 2 2 2 2 2 3 5% 76%	3897
	21st to end	Night	5% 4 1 3 2 2 3 2 5% 7% 66%	4253
November	1st to 10th	Night	8% 4 1 4 3 2 2 3 5% 7% 62%	2465
	11th to 20th	Night	10% 5% 2 4 3 3 3 3 5% 8% 55%	2730
	21st to end	Night	9% 5% 2 4 3 3 4 3 5% 5% 56%	2788
December	1st to 10th	Night	9% 4 1 4 3 3 4 3 5% 6% 58%	4700
	11th to 20th	Night	21% 8% 2 5% 3 4 5% 4 6% 7% 36%	5316
	21st to end	Night	19% 10% 3 8% 4 4 4 4 5% 7% 31%	7106

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	34% 6% 10% 23% 20% 7%	5220
	11th to 20th	Day	25% 5% 6% 11% 18% 36%	5340
	21st to end	Day	36% 6% 6% 16% 22% 14%	5843
February	1st to 10th	Day	37% 5% 6% 16% 20% 16%	1890
	11th to 20th	Day	37% 5% 8% 18% 21% 10%	2010
	21st to end	Day	37% 8% 7% 21% 18% 8%	1730
March	1st to 10th	Day	40% 11% 10% 12% 22% 5%	4879
	11th to 20th	Day	32% 7% 8% 28% 15% 10%	5000
	21st to end	Day	36% 10% 12% 25% 14% 3	5603
April	1st to 10th	Day	32% 6% 11% 23% 21% 8%	2400
	11th to 20th	Day	24% 7% 11% 25% 23% 9%	2372
	21st to end	Day	21% 7% 8% 30% 27% 7%	2400
May	1st to 10th	Day	11% 3 5% 23% 41% 17%	5440
	11th to 20th	Day	8% 8% 6% 32% 35% 11%	5810
	21st to end	Day	8% 3 5% 25% 41% 17%	6904
June	1st to 10th	Day	12% 6% 8% 24% 34% 16%	2800
	11th to 20th	Day	6% 4 5% 18% 35% 32%	2800
	21st to end	Day	6% 2 2 12% 32% 45%	2800
July	1st to 10th	Day	2 1 2 3 18% 74%	6108
	11th to 20th	Day	4 2 2 4 18% 71%	5811
	21st to end	Day	4 2 3 14% 31% 46%	6217
August	1st to 10th	Day	8% 2 3 7% 26% 54%	4206
	11th to 20th	Day	3 1 2 7% 28% 59%	3887
	21st to end	Day	5% 2 2 10% 32% 49%	4311
September	1st to 10th	Day	5% 2 4 9% 31% 49%	2400
	11th to 20th	Day	9% 4 4 17% 39% 27%	2400
	21st to end	Day	10% 3 3 18% 39% 26%	2140
October	1st to 10th	Day	12% 3 5% 12% 25% 43%	3280
	11th to 20th	Day	12% 3 3 22% 34% 25%	3261
	21st to end	Day	19% 3 5% 16% 36% 21%	3558
November	1st to 10th	Day	23% 4 7% 21% 28% 17%	2050
	11th to 20th	Day	26% 4 10% 20% 25% 15%	1890
	21st to end	Day	29% 3 8% 19% 25% 17%	1827
December	1st to 10th	Day	28% 4 6% 16% 30% 16%	2700
	11th to 20th	Day	43% 5% 9% 15% 15% 12%	3108
	21st to end	Day	45% 8% 10% 19% 12% 6%	4092
January	1st to 10th	Night	34% 6% 12% 20% 20% 8%	7684
	11th to 20th	Night	25% 4 5% 10% 18% 37%	7650
	21st to end	Night	34% 5% 7% 12% 22% 20%	8371
February	1st to 10th	Night	36% 4 7% 15% 20% 17%	2730
	11th to 20th	Night	34% 6% 7% 19% 24% 10%	2507
	21st to end	Night	35% 4 8% 22% 20% 10%	2076
March	1st to 10th	Night	45% 9% 8% 12% 18% 8%	5056
	11th to 20th	Night	31% 7% 9% 20% 21% 12%	5000
	21st to end	Night	37% 8% 10% 22% 18% 5%	5370
April	1st to 10th	Night	30% 5% 11% 21% 22% 10%	2000
	11th to 20th	Night	25% 5% 9% 25% 24% 13%	1979
	21st to end	Night	18% 6% 10% 25% 30% 10%	2000
May	1st to 10th	Night	9% 3 6% 19% 39% 23%	4557
	11th to 20th	Night	10% 6% 5% 22% 36% 21%	4088
	21st to end	Night	6% 3 4 19% 34% 33%	3972
June	1st to 10th	Night	9% 5% 10% 17% 34% 24%	1600
	11th to 20th	Night	8% 3 4 15% 26% 43%	1600
	21st to end	Night	3 2 3 8% 30% 54%	1600
July	1st to 10th	Night	1 2 2 13% 82%	3732
	11th to 20th	Night	3 1 2 3 17% 74%	4046
	21st to end	Night	4 2 4 9% 28% 53%	4345
August	1st to 10th	Night	7% 2 2 5% 21% 64%	2929
	11th to 20th	Night	3 1 1 4 22% 69%	3247
	21st to end	Night	5% 1 2 7% 30% 54%	3608
September	1st to 10th	Night	4 2 3 6% 26% 59%	2000
	11th to 20th	Night	8% 2 3 14% 32% 40%	2000
	21st to end	Night	9% 2 3 16% 36% 33%	2256
October	1st to 10th	Night	11% 3 4 13% 18% 52%	3920
	11th to 20th	Night	12% 2 5% 16% 38% 28%	3897
	21st to end	Night	16% 3 5% 14% 33% 29%	4253
November	1st to 10th	Night	20% 4 6% 20% 28% 22%	2465
	11th to 20th	Night	25% 4 10% 19% 24% 17%	2730
	21st to end	Night	28% 4 8% 16% 25% 19%	2788
December	1st to 10th	Night	26% 4 5% 16% 26% 22%	4700
	11th to 20th	Night	44% 5% 9% 12% 17% 12%	5316
	21st to end	Night	47% 7% 10% 18% 12% 6%	7106

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	31% 11% 26% 19% 11% 3	393
	11th to 20th	Day	15% 10% 22% 28% 21% 4	430
	21st to end	Day	14% 13% 26% 24% 18% 5%	473
February	1st to 10th	Day	24% 13% 21% 18% 17% 7%	430
	11th to 20th	Day	26% 13% 27% 20% 13% 2	510
	21st to end	Day	14% 16% 30% 28% 11% 1	446
March	1st to 10th	Day	22% 14% 32% 21% 9% 1	509
	11th to 20th	Day	23% 15% 25% 23% 12% 2	500
	21st to end	Day	19% 17% 31% 23% 9% 1	550
April	1st to 10th	Day	17% 14% 32% 21% 14% 2	500
	11th to 20th	Day	12% 16% 28% 31% 12% 2	492
	21st to end	Day	8% 13% 33% 29% 13% 4	500
May	1st to 10th	Day	8% 14% 31% 30% 14% 3	503
	11th to 20th	Day	8% 10% 29% 30% 17% 4	528
	21st to end	Day	6% 10% 25% 34% 20% 5%	573
June	1st to 10th	Day	4 6% 28% 36% 22% 5%	530
	11th to 20th	Day	2 9% 28% 41% 15% 5%	530
	21st to end	Day	2 3 22% 42% 26% 6%	530
July	1st to 10th	Day	1 1 20% 45% 26% 7%	526
	11th to 20th	Day	1 1 10% 45% 34% 9%	524
	21st to end	Day	1 11% 47% 31% 10%	575
August	1st to 10th	Day	2 4 17% 46% 26% 6%	527
	11th to 20th	Day	2 18% 43% 30% 8%	517
	21st to end	Day	1 1 13% 46% 31% 8%	583
September	1st to 10th	Day	2 4 17% 44% 28% 5%	530
	11th to 20th	Day	4 6% 22% 38% 26% 4	530
	21st to end	Day	5% 6% 17% 37% 28% 7%	530
October	1st to 10th	Day	4 6% 25% 33% 27% 5%	530
	11th to 20th	Day	6% 9% 19% 31% 28% 8%	530
	21st to end	Day	8% 6% 23% 32% 24% 7%	583
November	1st to 10th	Day	9% 10% 20% 27% 28% 7%	526
	11th to 20th	Day	15% 10% 22% 25% 21% 8%	330
	21st to end	Day	13% 10% 23% 28% 21% 5%	297
December	1st to 10th	Day	15% 10% 23% 30% 18% 5%	220
	11th to 20th	Day	16% 13% 20% 22% 21% 7%	220
	21st to end	Day	24% 17% 23% 19% 12% 5%	242
January	1st to 10th	Night	21% 7% 17% 27% 20% 8%	840
	11th to 20th	Night	14% 6% 18% 30% 25% 7%	840
	21st to end	Night	16% 7% 18% 33% 21% 5%	924
February	1st to 10th	Night	20% 7% 18% 29% 21% 5%	840
	11th to 20th	Night	18% 9% 18% 27% 20% 6%	824
	21st to end	Night	13% 12% 24% 30% 17% 2	692
March	1st to 10th	Night	19% 10% 20% 30% 19% 4	808
	11th to 20th	Night	15% 11% 19% 29% 21% 7%	800
	21st to end	Night	14% 11% 22% 30% 20% 3	880
April	1st to 10th	Night	12% 8% 25% 31% 21% 2	800
	11th to 20th	Night	9% 10% 24% 29% 21% 6%	791
	21st to end	Night	5% 8% 29% 27% 21% 10%	800
May	1st to 10th	Night	4 8% 25% 32% 24% 8%	800
	11th to 20th	Night	4 4 18% 37% 26% 10%	605
	21st to end	Night	3 6% 20% 32% 29% 9%	433
June	1st to 10th	Night	3 5% 18% 35% 29% 10%	400
	11th to 20th	Night	1 5% 18% 34% 33% 10%	400
	21st to end	Night	1 2 12% 36% 37% 13%	400
July	1st to 10th	Night	11% 30% 44% 15%	444
	11th to 20th	Night	1 3 24% 48% 24%	582
	21st to end	Night	4 21% 50% 24%	657
August	1st to 10th	Night	1 1 9% 31% 43% 15%	597
	11th to 20th	Night	1 1 11% 31% 41% 15%	783
	21st to end	Night	1 1 6% 26% 50% 16%	880
September	1st to 10th	Night	1 1 8% 34% 42% 15%	800
	11th to 20th	Night	2 2 14% 35% 36% 11%	800
	21st to end	Night	3 2 13% 28% 39% 15%	800
October	1st to 10th	Night	4 4 13% 35% 33% 10%	800
	11th to 20th	Night	5% 4 13% 32% 33% 13%	800
	21st to end	Night	6% 3 15% 33% 28% 15%	880
November	1st to 10th	Night	7% 7% 15% 34% 26% 11%	820
	11th to 20th	Night	11% 7% 18% 31% 26% 8%	840
	21st to end	Night	10% 5% 20% 36% 22% 7%	840
December	1st to 10th	Night	15% 6% 17% 32% 23% 6%	840
	11th to 20th	Night	20% 6% 18% 30% 21% 4	840
	21st to end	Night	18% 13% 20% 28% 16% 5%	924

Page generated at 2026-02-27 22:40:20. Version ac07

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