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 2024-12-02.

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 3 4 6% 65%	105111
	Night	9% 5% 1 4 2 2 3 3 4 6% 61%	103288
Transparency	Day	20% 5% 6% 18% 26% 27%	104873
	Night	22% 5% 7% 16% 23% 28%	103117
Seeing	Day	9% 9% 23% 33% 21% 5%	15657
	Night	9% 6% 16% 30% 29% 10%	25124

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	16% 8% 3 7% 4 4 3 3 4 5% 43%	2799
	11th to 20th	Day	18% 7% 2 8% 4 5% 4 5% 5% 7% 36%	2860
	21st to end	Day	19% 10% 3 7% 4 3 3 3 5% 7% 34%	3146
February	1st to 10th	Day	19% 8% 2 4 2 3 4 3 3 5% 47%	1710
	11th to 20th	Day	14% 6% 3 5% 4 4 4 5% 4 6% 46%	1804
	21st to end	Day	14% 8% 2 7% 3 4 3 3 5% 6% 44%	1570
March	1st to 10th	Day	16% 12% 3 9% 4 5% 5% 4 6% 7% 30%	3374
	11th to 20th	Day	12% 6% 2 4 2 3 3 2 4 6% 56%	3490
	21st to end	Day	14% 11% 3 7% 4 4 4 4 6% 7% 37%	3903
April	1st to 10th	Day	13% 8% 2 6% 3 3 4 4 4 6% 48%	2280
	11th to 20th	Day	9% 5% 2 3 3 3 3 4 6% 8% 54%	2249
	21st to end	Day	7% 4 1 4 3 3 3 4 5% 8% 59%	2280
May	1st to 10th	Day	6% 3 1 2 2 2 2 2 3 5% 73%	3800
	11th to 20th	Day	3 2 1 2 1 1 2 2 8% 7% 74%	4050
	21st to end	Day	3 2 1 2 1 1 2 3 5% 5% 75%	4813
June	1st to 10th	Day	3 3 1 3 2 2 2 3 4 8% 69%	2660
	11th to 20th	Day	1 1 2 1 1 1 2 5% 6% 78%	2660
	21st to end	Day	2 1 1 1 1 1 2 2 3 85%	2660
July	1st to 10th	Day	1 1 2 2 92%	4313
	11th to 20th	Day	1 1 1 1 1 2 2 3 7% 82%	4110
	21st to end	Day	1 1 1 1 1 2 3 4 88%	4455
August	1st to 10th	Day	1 1 1 1 2 3 3 4 4 80%	4091
	11th to 20th	Day	1 1 1 1 2 3 90%	3731
	21st to end	Day	1 1 1 1 1 1 1 2 4 88%	4180
September	1st to 10th	Day	1 1 1 1 1 1 1 2 4 87%	2280
	11th to 20th	Day	2 2 1 2 1 1 1 2 4 6% 78%	2280
	21st to end	Day	3 1 1 2 1 2 2 2 3 5% 79%	2033
October	1st to 10th	Day	2 2 1 3 2 2 2 2 4 5% 75%	3180
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 4 78%	3161
	21st to end	Day	5% 3 1 4 2 3 3 3 6% 6% 64%	3448
November	1st to 10th	Day	9% 5% 2 4 3 2 3 2 6% 6% 59%	1951
	11th to 20th	Day	10% 4 1 4 3 2 3 3 5% 8% 57%	1800
	21st to end	Day	12% 5% 1 4 3 3 3 3 5% 5% 55%	1740
December	1st to 10th	Day	14% 7% 2 4 3 3 4 4 6% 8% 44%	1528
	11th to 20th	Day	31% 8% 2 4 3 3 4 4 4 5% 32%	1928
	21st to end	Day	22% 10% 2 6% 3 4 4 3 5% 6% 36%	2794
January	1st to 10th	Night	13% 7% 2 8% 3 3 3 3 4 8% 45%	4150
	11th to 20th	Night	20% 9% 3 6% 3 4 4 4 6% 7% 35%	4110
	21st to end	Night	19% 10% 3 8% 3 4 4 3 5% 6% 34%	4521
February	1st to 10th	Night	17% 7% 2 5% 3 4 3 3 4 5% 48%	2470
	11th to 20th	Night	13% 7% 2 4 4 3 4 3 5% 8% 46%	2262
	21st to end	Night	13% 9% 2 6% 3 2 3 3 4 7% 48%	1884
March	1st to 10th	Night	20% 11% 3 9% 5% 4 4 3 4 5% 31%	3496
	11th to 20th	Night	9% 6% 2 5% 2 3 3 3 4 6% 57%	3490
	21st to end	Night	17% 12% 3 9% 3 3 4 3 4 7% 34%	3748
April	1st to 10th	Night	10% 7% 1 6% 4 3 4 4 5% 6% 49%	1900
	11th to 20th	Night	9% 6% 2 4 3 3 2 3 5% 7% 56%	1879
	21st to end	Night	5% 4 2 3 2 2 3 3 6% 10% 58%	1900
May	1st to 10th	Night	2 2 1 4 2 2 2 2 3 6% 74%	3180
	11th to 20th	Night	2 1 1 2 1 2 2 2 9% 8% 71%	2847
	21st to end	Night	2 3 1 1 1 1 2 3 4 6% 77%	2762
June	1st to 10th	Night	3 2 1 2 1 2 3 4 4 8% 71%	1520
	11th to 20th	Night	1 1 1 2 2 2 1 2 4 8% 77%	1520
	21st to end	Night	1 1 1 1 1 2 5% 5% 84%	1520
July	1st to 10th	Night	1 1 2 4 91%	2632
	11th to 20th	Night	1 1 1 1 1 3 7% 83%	2860
	21st to end	Night	1 1 1 1 2 4 6% 83%	3109
August	1st to 10th	Night	1 1 1 1 1 1 2 2 4 6% 80%	2848
	11th to 20th	Night	1 1 1 1 2 1 3 90%	3117
	21st to end	Night	1 1 1 1 1 1 1 2 4 87%	3498
September	1st to 10th	Night	1 1 1 1 1 1 2 5% 86%	1900
	11th to 20th	Night	3 2 2 2 1 1 2 3 5% 80%	1900
	21st to end	Night	3 1 2 2 1 1 2 3 5% 81%	2143
October	1st to 10th	Night	3 2 1 2 1 2 2 2 3 6% 75%	3800
	11th to 20th	Night	2 2 1 3 2 2 2 2 3 5% 76%	3777
	21st to end	Night	5% 4 1 3 2 2 3 2 5% 7% 66%	4121
November	1st to 10th	Night	8% 4 1 4 3 2 2 3 5% 7% 61%	2345
	11th to 20th	Night	8% 4 2 4 3 3 3 4 5% 9% 57%	2600
	21st to end	Night	10% 6% 2 4 3 3 4 4 5% 5% 56%	2655
December	1st to 10th	Night	15% 6% 2 5% 3 3 3 2 5% 6% 50%	2686
	11th to 20th	Night	29% 8% 2 4 3 3 4 3 4 5% 34%	3276
	21st to end	Night	18% 10% 2 7% 4 4 4 3 5% 7% 36%	4862

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	37% 7% 9% 28% 16% 4	2799
	11th to 20th	Day	42% 8% 10% 17% 13% 9%	2860
	21st to end	Day	46% 7% 6% 20% 13% 7%	3146
February	1st to 10th	Day	37% 5% 6% 16% 21% 14%	1710
	11th to 20th	Day	35% 6% 8% 18% 22% 11%	1814
	21st to end	Day	37% 8% 7% 20% 19% 8%	1570
March	1st to 10th	Day	42% 12% 11% 13% 17% 4	3374
	11th to 20th	Day	27% 6% 7% 28% 18% 14%	3490
	21st to end	Day	40% 9% 12% 24% 12% 3	3903
April	1st to 10th	Day	33% 5% 11% 22% 20% 8%	2280
	11th to 20th	Day	24% 7% 11% 26% 23% 9%	2252
	21st to end	Day	20% 7% 8% 30% 27% 7%	2280
May	1st to 10th	Day	14% 4 6% 25% 31% 20%	3800
	11th to 20th	Day	9% 11% 5% 32% 32% 12%	4053
	21st to end	Day	10% 4 7% 28% 40% 12%	4814
June	1st to 10th	Day	13% 6% 9% 24% 32% 16%	2660
	11th to 20th	Day	6% 4 5% 18% 36% 30%	2660
	21st to end	Day	6% 2 2 12% 32% 44%	2660
July	1st to 10th	Day	2 2 2 5% 18% 72%	4247
	11th to 20th	Day	5% 2 4 5% 20% 63%	4041
	21st to end	Day	3 2 3 7% 28% 58%	4315
August	1st to 10th	Day	8% 2 3 7% 26% 54%	4076
	11th to 20th	Day	3 1 2 6% 29% 59%	3767
	21st to end	Day	5% 2 2 10% 33% 48%	4179
September	1st to 10th	Day	5% 2 4 9% 30% 51%	2280
	11th to 20th	Day	8% 4 4 18% 39% 28%	2280
	21st to end	Day	10% 2 3 19% 40% 27%	2033
October	1st to 10th	Day	12% 3 5% 11% 25% 44%	3180
	11th to 20th	Day	12% 3 4 22% 34% 25%	3161
	21st to end	Day	19% 3 5% 16% 36% 21%	3448
November	1st to 10th	Day	24% 4 8% 20% 28% 17%	1951
	11th to 20th	Day	24% 4 10% 21% 26% 16%	1800
	21st to end	Day	30% 3 8% 18% 25% 17%	1740
December	1st to 10th	Day	36% 5% 9% 17% 19% 14%	1528
	11th to 20th	Day	52% 4 8% 15% 14% 7%	1928
	21st to end	Day	44% 6% 9% 21% 14% 6%	2794
January	1st to 10th	Night	32% 7% 13% 27% 17% 5%	4150
	11th to 20th	Night	43% 7% 9% 19% 14% 9%	4110
	21st to end	Night	43% 7% 9% 15% 16% 10%	4521
February	1st to 10th	Night	36% 4 8% 15% 21% 16%	2470
	11th to 20th	Night	31% 6% 7% 20% 25% 11%	2263
	21st to end	Night	35% 4 8% 23% 21% 9%	1884
March	1st to 10th	Night	46% 10% 10% 15% 14% 5%	3496
	11th to 20th	Night	25% 6% 6% 19% 28% 15%	3490
	21st to end	Night	38% 10% 11% 20% 16% 6%	3748
April	1st to 10th	Night	31% 4 11% 21% 22% 11%	1900
	11th to 20th	Night	25% 4 9% 26% 24% 12%	1879
	21st to end	Night	17% 6% 10% 26% 30% 10%	1900
May	1st to 10th	Night	10% 4 8% 20% 32% 26%	3180
	11th to 20th	Night	11% 8% 6% 21% 34% 20%	2848
	21st to end	Night	8% 4 6% 22% 35% 25%	2762
June	1st to 10th	Night	10% 6% 10% 17% 34% 24%	1520
	11th to 20th	Night	9% 3 4 16% 27% 40%	1520
	21st to end	Night	3 2 3 8% 30% 53%	1520
July	1st to 10th	Night	1 2 3 14% 78%	2590
	11th to 20th	Night	4 1 2 5% 17% 70%	2806
	21st to end	Night	4 2 3 5% 25% 62%	3011
August	1st to 10th	Night	7% 2 2 5% 21% 64%	2839
	11th to 20th	Night	3 1 1 4 22% 69%	3147
	21st to end	Night	5% 1 2 8% 30% 54%	3498
September	1st to 10th	Night	4 2 3 6% 25% 61%	1900
	11th to 20th	Night	8% 2 3 14% 31% 41%	1900
	21st to end	Night	8% 2 3 16% 37% 34%	2143
October	1st to 10th	Night	11% 3 3 12% 18% 53%	3800
	11th to 20th	Night	12% 2 5% 16% 37% 28%	3777
	21st to end	Night	17% 3 4 14% 33% 29%	4121
November	1st to 10th	Night	20% 4 7% 20% 27% 22%	2345
	11th to 20th	Night	23% 4 11% 19% 25% 18%	2600
	21st to end	Night	29% 4 8% 15% 25% 19%	2655
December	1st to 10th	Night	33% 4 7% 18% 20% 17%	2686
	11th to 20th	Night	51% 5% 8% 15% 14% 8%	3276
	21st to end	Night	42% 8% 10% 18% 15% 7%	4862

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	30% 10% 25% 19% 12% 4	336
	11th to 20th	Day	17% 11% 21% 28% 19% 4	370
	21st to end	Day	15% 12% 23% 24% 19% 6%	407
February	1st to 10th	Day	24% 12% 19% 19% 19% 8%	370
	11th to 20th	Day	21% 12% 27% 22% 15% 2	434
	21st to end	Day	15% 15% 28% 27% 13% 2	382
March	1st to 10th	Day	22% 13% 32% 23% 10% 1	460
	11th to 20th	Day	21% 15% 24% 24% 13% 3	460
	21st to end	Day	19% 17% 32% 23% 9% 1	506
April	1st to 10th	Day	17% 14% 32% 21% 14% 2	460
	11th to 20th	Day	12% 16% 28% 31% 12% 1	452
	21st to end	Day	7% 13% 34% 28% 13% 4	460
May	1st to 10th	Day	9% 14% 32% 29% 14% 3	463
	11th to 20th	Day	7% 10% 28% 32% 18% 5%	488
	21st to end	Day	7% 10% 24% 34% 20% 5%	529
June	1st to 10th	Day	4 6% 28% 35% 22% 5%	490
	11th to 20th	Day	3 8% 27% 41% 16% 5%	490
	21st to end	Day	1 2 21% 43% 26% 5%	490
July	1st to 10th	Day	1 1 18% 46% 27% 7%	486
	11th to 20th	Day	1 1 10% 45% 35% 8%	484
	21st to end	Day	1 11% 47% 32% 10%	531
August	1st to 10th	Day	2 3 16% 47% 26% 6%	487
	11th to 20th	Day	2 18% 42% 30% 8%	477
	21st to end	Day	1 1 12% 46% 31% 8%	539
September	1st to 10th	Day	1 4 16% 44% 29% 6%	490
	11th to 20th	Day	3 7% 23% 38% 26% 4	490
	21st to end	Day	5% 5% 14% 39% 29% 8%	490
October	1st to 10th	Day	3 5% 25% 34% 28% 5%	490
	11th to 20th	Day	5% 8% 19% 32% 28% 9%	490
	21st to end	Day	8% 6% 24% 31% 25% 7%	539
November	1st to 10th	Day	9% 11% 20% 25% 29% 6%	487
	11th to 20th	Day	11% 8% 22% 27% 23% 9%	300
	21st to end	Day	14% 10% 22% 28% 20% 6%	270
December	1st to 10th	Day	17% 12% 22% 28% 17% 4	182
	11th to 20th	Day	17% 14% 19% 23% 19% 7%	180
	21st to end	Day	20% 19% 19% 22% 14% 6%	198
January	1st to 10th	Night	19% 6% 16% 27% 23% 9%	760
	11th to 20th	Night	15% 6% 16% 29% 26% 8%	760
	21st to end	Night	17% 6% 17% 33% 22% 5%	836
February	1st to 10th	Night	21% 6% 15% 30% 23% 6%	760
	11th to 20th	Night	15% 9% 17% 29% 22% 7%	744
	21st to end	Night	14% 12% 20% 32% 19% 3	628
March	1st to 10th	Night	19% 9% 19% 30% 20% 4	760
	11th to 20th	Night	13% 10% 18% 29% 22% 7%	760
	21st to end	Night	14% 11% 22% 30% 21% 3	836
April	1st to 10th	Night	12% 8% 25% 31% 22% 2	760
	11th to 20th	Night	10% 11% 23% 29% 21% 7%	751
	21st to end	Night	5% 9% 29% 26% 20% 11%	760
May	1st to 10th	Night	4 8% 25% 32% 23% 8%	760
	11th to 20th	Night	5% 3 17% 38% 27% 10%	575
	21st to end	Night	4 6% 19% 31% 30% 9%	411
June	1st to 10th	Night	3 5% 19% 35% 28% 10%	380
	11th to 20th	Night	1 5% 15% 33% 35% 10%	380
	21st to end	Night	1 1 12% 36% 37% 14%	380
July	1st to 10th	Night	10% 28% 45% 16%	421
	11th to 20th	Night	1 4 24% 47% 24%	552
	21st to end	Night	4 20% 50% 25%	624
August	1st to 10th	Night	1 8% 32% 43% 16%	567
	11th to 20th	Night	1 1 10% 30% 42% 16%	743
	21st to end	Night	1 1 6% 24% 52% 17%	836
September	1st to 10th	Night	1 7% 32% 43% 16%	760
	11th to 20th	Night	2 2 15% 33% 37% 12%	760
	21st to end	Night	3 2 11% 28% 41% 16%	760
October	1st to 10th	Night	4 4 13% 34% 34% 11%	760
	11th to 20th	Night	5% 4 12% 31% 34% 14%	760
	21st to end	Night	6% 3 15% 31% 29% 16%	836
November	1st to 10th	Night	7% 7% 15% 33% 26% 12%	780
	11th to 20th	Night	9% 6% 18% 32% 27% 8%	800
	21st to end	Night	10% 5% 20% 35% 24% 7%	800
December	1st to 10th	Night	17% 7% 15% 32% 24% 7%	768
	11th to 20th	Night	21% 6% 18% 28% 23% 5%	760
	21st to end	Night	17% 12% 19% 30% 17% 5%	836

Page generated at 2024-11-29 07:43:10. Version ac07

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