High Sierra Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the High Sierra Park clear sky chart from 2005-11-06 to 2024-11-05.

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	8% 5% 1 3 2 2 2 2 3 5% 65%	105049
	Night	9% 6% 1 3 2 2 3 2 4 5% 62%	102723
Transparency	Day	23% 4 6% 18% 26% 24%	104798
	Night	26% 4 7% 19% 24% 21%	102563
Seeing	Day	13% 13% 33% 27% 11% 4	15198
	Night	12% 4 16% 36% 25% 7%	24588

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% 13% 3 4 3 3 3 2 3 4 46%	2539
	11th to 20th	Day	19% 8% 3 7% 5% 4 4 3 3 6% 37%	2714
	21st to end	Day	18% 12% 2 6% 3 4 4 3 5% 7% 37%	3146
February	1st to 10th	Day	18% 10% 2 4 3 2 2 3 4 5% 48%	1729
	11th to 20th	Day	12% 12% 3 3 3 3 4 2 4 6% 48%	1850
	21st to end	Day	18% 13% 3 4 2 3 3 2 3 5% 43%	1570
March	1st to 10th	Day	14% 17% 4 7% 4 4 4 4 6% 7% 28%	3138
	11th to 20th	Day	12% 8% 2 4 3 3 3 2 4 5% 54%	3480
	21st to end	Day	15% 15% 3 7% 4 4 4 3 4 5% 35%	4054
April	1st to 10th	Day	13% 10% 2 4 4 3 3 3 4 7% 48%	2280
	11th to 20th	Day	13% 8% 2 4 3 2 3 3 5% 6% 51%	2249
	21st to end	Day	11% 5% 1 3 3 3 3 3 4 6% 58%	2280
May	1st to 10th	Day	8% 3 1 3 2 2 2 2 4 4 69%	3890
	11th to 20th	Day	4 3 1 2 1 1 2 2 4 5% 74%	4248
	21st to end	Day	5% 3 1 2 2 2 2 2 3 4 73%	4813
June	1st to 10th	Day	5% 4 1 3 3 3 3 3 4 6% 65%	2660
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 5% 79%	2660
	21st to end	Day	2 2 1 2 1 2 2 2 2 2 82%	2660
July	1st to 10th	Day	1 1 1 1 1 1 1 2 92%	4420
	11th to 20th	Day	1 1 2 2 2 2 2 3 4 81%	4420
	21st to end	Day	1 1 1 1 1 1 1 2 3 86%	4551
August	1st to 10th	Day	2 2 1 2 1 1 2 2 2 3 82%	4009
	11th to 20th	Day	1 1 1 1 2 1 2 3 88%	3724
	21st to end	Day	1 1 1 1 1 1 1 1 2 2 87%	4180
September	1st to 10th	Day	2 1 1 2 1 1 1 2 3 87%	2280
	11th to 20th	Day	3 2 1 2 1 2 3 2 3 5% 75%	2256
	21st to end	Day	4 1 1 2 1 1 2 2 3 4 79%	2090
October	1st to 10th	Day	4 2 1 3 2 1 2 2 4 5% 74%	3215
	11th to 20th	Day	5% 2 1 2 2 1 2 2 3 3 77%	3161
	21st to end	Day	6% 3 1 4 2 2 3 3 4 7% 66%	3431
November	1st to 10th	Day	10% 6% 1 5% 4 3 3 3 5% 6% 54%	1710
	11th to 20th	Day	10% 5% 1 3 3 3 3 3 5% 6% 58%	1710
	21st to end	Day	11% 7% 1 4 3 3 3 3 4 7% 54%	1690
December	1st to 10th	Day	15% 6% 2 4 3 4 4 2 3 6% 52%	1520
	11th to 20th	Day	27% 9% 2 6% 4 3 3 3 4 5% 35%	1928
	21st to end	Day	12% 9% 3 6% 4 4 5% 4 6% 8% 39%	2794
January	1st to 10th	Night	14% 10% 3 5% 3 2 3 2 5% 6% 48%	4406
	11th to 20th	Night	21% 9% 2 6% 4 4 4 4 5% 5% 36%	4234
	21st to end	Night	18% 11% 2 6% 4 4 4 3 5% 6% 37%	4521
February	1st to 10th	Night	16% 9% 1 5% 3 2 2 3 4 5% 49%	2450
	11th to 20th	Night	12% 12% 2 3 3 2 2 3 5% 7% 48%	2218
	21st to end	Night	15% 10% 3 4 3 3 2 3 3 5% 49%	1884
March	1st to 10th	Night	16% 18% 3 5% 3 3 3 4 5% 4 35%	3736
	11th to 20th	Night	14% 7% 1 3 2 2 2 2 3 5% 58%	3495
	21st to end	Night	18% 12% 2 5% 3 3 3 3 5% 6% 38%	3597
April	1st to 10th	Night	12% 7% 2 5% 3 3 3 3 4 7% 51%	1900
	11th to 20th	Night	10% 6% 1 4 3 2 3 3 4 5% 57%	1879
	21st to end	Night	8% 5% 2 3 3 2 2 3 4 7% 61%	1900
May	1st to 10th	Night	4 5% 2 2 1 2 2 2 3 6% 71%	3084
	11th to 20th	Night	3 2 1 2 1 1 2 2 4 6% 76%	2645
	21st to end	Night	3 3 1 2 2 2 2 2 3 4 77%	2762
June	1st to 10th	Night	5% 3 1 3 2 3 2 3 5% 6% 68%	1520
	11th to 20th	Night	1 1 2 1 3 2 3 3 83%	1520
	21st to end	Night	1 2 1 2 2 1 2 2 2 3 84%	1520
July	1st to 10th	Night	1 1 1 1 1 1 93%	2540
	11th to 20th	Night	3 3 1 3 2 2 2 2 3 3 76%	2540
	21st to end	Night	1 2 1 2 2 2 2 1 3 3 82%	3004
August	1st to 10th	Night	2 2 1 2 1 1 2 2 3 3 79%	2932
	11th to 20th	Night	1 1 1 1 1 1 1 3 3 87%	3126
	21st to end	Night	3 2 1 1 1 1 1 1 1 2 88%	3498
September	1st to 10th	Night	1 1 1 1 1 1 1 1 1 2 89%	1900
	11th to 20th	Night	3 2 1 2 2 3 2 3 4 78%	1922
	21st to end	Night	2 2 2 2 1 2 2 3 4 80%	2090
October	1st to 10th	Night	3 2 1 2 2 2 2 2 3 3 79%	3761
	11th to 20th	Night	3 1 1 2 1 2 1 2 3 4 79%	3777
	21st to end	Night	7% 2 1 3 3 3 2 2 4 5% 68%	4137
November	1st to 10th	Night	12% 5% 1 3 2 2 2 2 4 6% 61%	2469
	11th to 20th	Night	10% 3 1 3 3 2 3 3 5% 7% 59%	2470
	21st to end	Night	11% 6% 1 4 3 3 3 3 4 6% 57%	2488
December	1st to 10th	Night	16% 6% 2 3 2 2 3 3 5% 6% 52%	2660
	11th to 20th	Night	26% 10% 2 4 3 3 3 3 5% 5% 36%	3276
	21st to end	Night	14% 8% 2 8% 4 5% 5% 3 6% 6% 38%	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	42% 4 9% 23% 19% 4	2539
	11th to 20th	Day	50% 4 9% 14% 13% 9%	2714
	21st to end	Day	47% 5% 12% 19% 13% 4	3146
February	1st to 10th	Day	40% 3 7% 22% 17% 11%	1729
	11th to 20th	Day	37% 4 8% 21% 23% 7%	1860
	21st to end	Day	44% 4 7% 20% 21% 5%	1570
March	1st to 10th	Day	51% 8% 12% 14% 12% 4	3138
	11th to 20th	Day	31% 6% 13% 29% 14% 8%	3480
	21st to end	Day	46% 9% 12% 21% 10% 2	4054
April	1st to 10th	Day	35% 6% 13% 22% 19% 5%	2280
	11th to 20th	Day	32% 5% 13% 26% 18% 5%	2252
	21st to end	Day	28% 4 11% 32% 22% 4	2280
May	1st to 10th	Day	18% 3 8% 31% 26% 14%	3890
	11th to 20th	Day	13% 3 6% 29% 39% 9%	4251
	21st to end	Day	16% 4 6% 36% 35% 3	4814
June	1st to 10th	Day	19% 6% 9% 23% 30% 13%	2660
	11th to 20th	Day	10% 3 6% 22% 38% 21%	2660
	21st to end	Day	10% 2 3 11% 33% 42%	2660
July	1st to 10th	Day	3 1 1 6% 16% 74%	4351
	11th to 20th	Day	8% 2 3 7% 18% 62%	4345
	21st to end	Day	6% 2 2 7% 27% 56%	4407
August	1st to 10th	Day	9% 2 1 7% 29% 52%	3994
	11th to 20th	Day	4 2 2 6% 32% 54%	3760
	21st to end	Day	7% 1 2 6% 41% 42%	4179
September	1st to 10th	Day	7% 1 2 8% 34% 48%	2280
	11th to 20th	Day	13% 3 2 21% 39% 21%	2256
	21st to end	Day	11% 2 4 17% 38% 27%	2090
October	1st to 10th	Day	14% 3 3 11% 29% 40%	3215
	11th to 20th	Day	14% 2 3 18% 41% 21%	3161
	21st to end	Day	20% 3 5% 18% 38% 16%	3431
November	1st to 10th	Day	31% 4 7% 21% 21% 16%	1710
	11th to 20th	Day	27% 4 8% 19% 28% 13%	1710
	21st to end	Day	30% 4 7% 17% 29% 13%	1690
December	1st to 10th	Day	35% 3 9% 19% 21% 12%	1520
	11th to 20th	Day	53% 4 5% 13% 15% 9%	1928
	21st to end	Day	41% 6% 12% 19% 15% 6%	2794
January	1st to 10th	Night	38% 4 12% 25% 17% 5%	4406
	11th to 20th	Night	48% 4 8% 18% 13% 10%	4234
	21st to end	Night	46% 5% 11% 17% 14% 7%	4521
February	1st to 10th	Night	38% 3 6% 21% 19% 12%	2450
	11th to 20th	Night	34% 4 7% 24% 20% 9%	2219
	21st to end	Night	39% 3 10% 21% 20% 6%	1884
March	1st to 10th	Night	50% 5% 8% 19% 13% 5%	3736
	11th to 20th	Night	30% 4 10% 26% 19% 10%	3495
	21st to end	Night	45% 7% 12% 21% 12% 4	3597
April	1st to 10th	Night	34% 4 15% 22% 20% 6%	1900
	11th to 20th	Night	28% 6% 12% 27% 19% 8%	1879
	21st to end	Night	23% 6% 11% 35% 20% 4	1900
May	1st to 10th	Night	16% 3 9% 33% 27% 11%	3084
	11th to 20th	Night	10% 3 9% 29% 35% 13%	2645
	21st to end	Night	13% 3 8% 44% 28% 4	2762
June	1st to 10th	Night	17% 5% 12% 24% 29% 13%	1520
	11th to 20th	Night	6% 3 6% 24% 37% 22%	1520
	21st to end	Night	8% 2 3 11% 34% 42%	1520
July	1st to 10th	Night	3 1 1 5% 17% 74%	2500
	11th to 20th	Night	14% 3 3 6% 16% 58%	2492
	21st to end	Night	9% 2 2 7% 24% 56%	2910
August	1st to 10th	Night	12% 2 1 8% 25% 52%	2923
	11th to 20th	Night	5% 1 2 7% 27% 58%	3156
	21st to end	Night	8% 1 1 9% 36% 45%	3498
September	1st to 10th	Night	5% 2 3 7% 35% 48%	1900
	11th to 20th	Night	11% 3 3 18% 40% 25%	1922
	21st to end	Night	10% 2 3 21% 38% 26%	2090
October	1st to 10th	Night	12% 3 3 11% 28% 44%	3761
	11th to 20th	Night	11% 2 4 21% 39% 23%	3777
	21st to end	Night	20% 3 3 20% 36% 19%	4137
November	1st to 10th	Night	26% 3 8% 22% 24% 17%	2469
	11th to 20th	Night	25% 4 7% 22% 28% 14%	2470
	21st to end	Night	30% 3 7% 19% 28% 14%	2488
December	1st to 10th	Night	34% 4 8% 20% 19% 15%	2660
	11th to 20th	Night	49% 4 8% 13% 18% 8%	3276
	21st to end	Night	44% 6% 11% 16% 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	34% 8% 27% 20% 9% 2	180
	11th to 20th	Day	24% 9% 22% 31% 10% 4	289
	21st to end	Day	23% 8% 26% 23% 16% 3	407
February	1st to 10th	Day	28% 13% 22% 23% 10% 4	379
	11th to 20th	Day	21% 14% 34% 20% 9% 2	455
	21st to end	Day	23% 18% 34% 19% 7% 1	382
March	1st to 10th	Day	30% 17% 30% 16% 6% 1	460
	11th to 20th	Day	27% 15% 27% 21% 8% 2	460
	21st to end	Day	24% 18% 35% 17% 6%	506
April	1st to 10th	Day	21% 19% 33% 19% 7% 1	460
	11th to 20th	Day	23% 21% 28% 22% 4 2	452
	21st to end	Day	13% 19% 32% 23% 10% 2	460
May	1st to 10th	Day	15% 22% 33% 19% 6% 4	463
	11th to 20th	Day	15% 18% 27% 24% 11% 4	488
	21st to end	Day	15% 15% 28% 24% 11% 7%	529
June	1st to 10th	Day	10% 14% 34% 26% 11% 5%	490
	11th to 20th	Day	6% 18% 37% 25% 8% 6%	490
	21st to end	Day	4 11% 36% 30% 11% 7%	490
July	1st to 10th	Day	2 9% 41% 30% 11% 7%	486
	11th to 20th	Day	2 5% 38% 36% 13% 7%	484
	21st to end	Day	2 7% 37% 37% 10% 8%	531
August	1st to 10th	Day	3 10% 39% 30% 13% 5%	487
	11th to 20th	Day	2 8% 41% 31% 12% 6%	477
	21st to end	Day	2 7% 39% 33% 14% 4	539
September	1st to 10th	Day	3 8% 43% 30% 14% 2	490
	11th to 20th	Day	7% 11% 37% 32% 11% 1	490
	21st to end	Day	5% 11% 34% 38% 9% 2	490
October	1st to 10th	Day	6% 13% 32% 33% 14% 3	490
	11th to 20th	Day	7% 10% 33% 34% 13% 3	490
	21st to end	Day	9% 10% 30% 32% 15% 3	534
November	1st to 10th	Day	15% 9% 25% 27% 17% 7%	282
	11th to 20th	Day	12% 6% 27% 29% 17% 9%	270
	21st to end	Day	15% 9% 24% 32% 16% 5%	260
December	1st to 10th	Day	22% 7% 21% 23% 20% 7%	180
	11th to 20th	Day	19% 12% 27% 19% 17% 6%	180
	21st to end	Day	24% 7% 29% 22% 14% 5%	198
January	1st to 10th	Night	22% 4 23% 26% 17% 8%	760
	11th to 20th	Night	17% 6% 22% 34% 16% 6%	760
	21st to end	Night	21% 3 23% 28% 19% 5%	836
February	1st to 10th	Night	20% 4 21% 31% 18% 5%	760
	11th to 20th	Night	19% 7% 19% 30% 17% 8%	744
	21st to end	Night	22% 6% 19% 36% 13% 4	628
March	1st to 10th	Night	26% 8% 16% 31% 15% 4	760
	11th to 20th	Night	23% 4 15% 32% 20% 6%	760
	21st to end	Night	22% 5% 20% 33% 18% 2	836
April	1st to 10th	Night	17% 5% 19% 36% 20% 3	760
	11th to 20th	Night	13% 7% 20% 34% 19% 6%	751
	21st to end	Night	10% 4 19% 37% 23% 7%	760
May	1st to 10th	Night	10% 6% 20% 36% 22% 7%	703
	11th to 20th	Night	6% 3 17% 39% 31% 3	451
	21st to end	Night	7% 3 14% 36% 33% 6%	411
June	1st to 10th	Night	7% 2 9% 44% 32% 6%	380
	11th to 20th	Night	1 1 14% 44% 36% 4	380
	21st to end	Night	2 1 11% 43% 39% 5%	380
July	1st to 10th	Night	1 8% 40% 47% 5%	370
	11th to 20th	Night	2 1 8% 42% 41% 6%	368
	21st to end	Night	3 2 9% 28% 44% 15%	558
August	1st to 10th	Night	3 1 11% 36% 39% 10%	612
	11th to 20th	Night	1 10% 42% 38% 8%	752
	21st to end	Night	2 1 7% 40% 43% 7%	836
September	1st to 10th	Night	1 1 8% 41% 40% 9%	760
	11th to 20th	Night	4 11% 39% 36% 10%	760
	21st to end	Night	3 2 13% 40% 32% 11%	760
October	1st to 10th	Night	6% 2 14% 46% 24% 9%	760
	11th to 20th	Night	6% 2 16% 37% 31% 8%	760
	21st to end	Night	7% 3 17% 34% 26% 13%	836
November	1st to 10th	Night	15% 2 13% 36% 25% 9%	760
	11th to 20th	Night	13% 2 20% 37% 20% 7%	760
	21st to end	Night	14% 5% 21% 33% 20% 6%	760
December	1st to 10th	Night	20% 4 18% 35% 15% 7%	760
	11th to 20th	Night	24% 4 21% 28% 18% 5%	760
	21st to end	Night	23% 8% 20% 30% 16% 4	836

Page generated at 2024-11-02 23:11:08. Version ac07

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