Fremont Peak
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fremont Peak 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	5% 5% 2 5% 3 3 3 3 5% 8% 59%	139588
	Night	6% 7% 3 6% 4 4 4 4 6% 7% 51%	139090
Transparency	Day	23% 5% 8% 18% 25% 21%	134555
	Night	29% 7% 10% 15% 21% 18%	135107
Seeing	Day	8% 9% 26% 32% 18% 6%	17135
	Night	9% 5% 13% 33% 31% 9%	26668

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	10% 7% 3 6% 4 3 3 3 5% 8% 48%	5040
	11th to 20th	Day	7% 4 2 5% 3 3 3 3 4 6% 60%	5340
	21st to end	Day	10% 8% 2 8% 4 4 4 4 6% 7% 43%	5843
February	1st to 10th	Day	13% 7% 2 5% 4 3 3 3 5% 6% 47%	1890
	11th to 20th	Day	12% 8% 3 7% 5% 3 5% 4 6% 6% 44%	2007
	21st to end	Day	10% 9% 2 7% 5% 3 4 3 6% 5% 44%	1730
March	1st to 10th	Day	11% 9% 3 9% 6% 5% 7% 5% 7% 7% 30%	4802
	11th to 20th	Day	9% 5% 3 6% 4 4 4 3 5% 7% 49%	5000
	21st to end	Day	8% 8% 3 8% 5% 5% 6% 4 7% 10% 36%	5634
April	1st to 10th	Day	9% 7% 3 7% 5% 4 3 4 5% 7% 48%	2400
	11th to 20th	Day	7% 7% 2 6% 4 4 3 3 5% 7% 51%	2369
	21st to end	Day	6% 7% 2 6% 4 4 3 4 5% 7% 53%	2400
May	1st to 10th	Day	5% 3 1 2 1 2 2 2 4 6% 71%	5440
	11th to 20th	Day	2 3 1 3 3 3 3 3 5% 9% 65%	5954
	21st to end	Day	2 7% 2 4 3 3 3 2 4 8% 62%	6902
June	1st to 10th	Day	3 5% 2 5% 3 3 3 4 5% 8% 58%	2800
	11th to 20th	Day	2 4 1 3 2 2 2 3 3 7% 71%	2800
	21st to end	Day	2 3 1 3 3 3 3 2 3 6% 73%	2800
July	1st to 10th	Day	1 1 2 1 1 2 1 3 6% 81%	6319
	11th to 20th	Day	1 1 1 2 2 2 2 3 5% 9% 71%	5925
	21st to end	Day	2 1 4 4 3 4 3 5% 11% 63%	6402
August	1st to 10th	Day	1 2 1 2 2 2 2 2 5% 9% 71%	5777
	11th to 20th	Day	1 1 2 3 2 2 2 4 9% 74%	5368
	21st to end	Day	2 1 2 2 2 2 3 4 8% 74%	5984
September	1st to 10th	Day	1 3 1 2 2 1 2 2 3 6% 77%	2400
	11th to 20th	Day	3 4 2 4 3 3 3 2 4 8% 64%	2400
	21st to end	Day	3 3 1 3 2 2 2 2 4 6% 73%	2150
October	1st to 10th	Day	2 2 1 3 2 3 3 2 3 5% 74%	3280
	11th to 20th	Day	2 4 2 5% 3 3 3 2 3 6% 66%	3261
	21st to end	Day	3 3 1 4 3 3 4 3 5% 7% 62%	3558
November	1st to 10th	Day	6% 5% 2 5% 3 4 3 3 4 7% 57%	2001
	11th to 20th	Day	7% 6% 3 6% 4 4 4 4 5% 6% 52%	1890
	21st to end	Day	10% 4 2 4 3 4 3 3 5% 7% 57%	1822
December	1st to 10th	Day	6% 6% 2 5% 3 3 4 3 5% 7% 56%	2700
	11th to 20th	Day	13% 9% 3 8% 5% 4 5% 4 6% 8% 37%	3108
	21st to end	Day	12% 10% 4 9% 6% 5% 5% 4 6% 7% 31%	4092
January	1st to 10th	Night	10% 8% 2 6% 4 4 4 3 5% 7% 46%	7853
	11th to 20th	Night	8% 4 2 5% 3 3 4 3 6% 8% 55%	7650
	21st to end	Night	11% 8% 3 9% 4 4 4 3 5% 7% 41%	8371
February	1st to 10th	Night	12% 8% 2 5% 4 4 3 3 4 5% 48%	2730
	11th to 20th	Night	11% 8% 4 7% 4 4 4 4 6% 7% 43%	2500
	21st to end	Night	10% 7% 3 6% 4 4 3 2 4 6% 50%	2076
March	1st to 10th	Night	14% 14% 4 9% 5% 5% 4 3 4 5% 33%	5123
	11th to 20th	Night	9% 8% 3 7% 5% 4 5% 3 4 7% 46%	5000
	21st to end	Night	12% 12% 4 8% 5% 4 4 4 6% 7% 35%	5341
April	1st to 10th	Night	10% 8% 2 5% 5% 4 4 4 5% 7% 48%	2000
	11th to 20th	Night	8% 7% 2 6% 4 3 3 3 5% 7% 51%	1979
	21st to end	Night	5% 8% 2 5% 3 3 5% 3 6% 8% 53%	2000
May	1st to 10th	Night	2 5% 2 5% 3 3 3 3 6% 6% 62%	4560
	11th to 20th	Night	2 8% 5% 8% 5% 4 4 4 9% 7% 44%	3947
	21st to end	Night	2 8% 3 5% 3 3 4 5% 7% 6% 54%	3972
June	1st to 10th	Night	4 8% 3 7% 4 4 4 4 6% 7% 51%	1600
	11th to 20th	Night	2 6% 3 4 3 3 3 4 6% 7% 60%	1600
	21st to end	Night	1 6% 2 6% 3 4 3 2 4 5% 64%	1600
July	1st to 10th	Night	2 3 4 2 2 2 2 6% 7% 70%	3640
	11th to 20th	Night	4 3 6% 3 3 5% 4 8% 8% 56%	4048
	21st to end	Night	4 4 9% 6% 6% 9% 9% 10% 9% 34%	4472
August	1st to 10th	Night	1 4 2 5% 3 3 4 5% 8% 9% 58%	4035
	11th to 20th	Night	3 1 3 3 4 5% 4 7% 7% 63%	4501
	21st to end	Night	3 2 5% 2 3 3 3 5% 8% 65%	5015
September	1st to 10th	Night	1 4 3 4 3 2 2 2 4 7% 68%	2000
	11th to 20th	Night	3 6% 3 7% 4 3 4 3 5% 6% 57%	2000
	21st to end	Night	2 5% 1 3 3 2 2 2 3 6% 69%	2245
October	1st to 10th	Night	3 3 1 2 2 2 2 2 3 5% 74%	3920
	11th to 20th	Night	3 6% 2 6% 4 4 4 3 6% 7% 55%	3897
	21st to end	Night	3 5% 2 6% 3 3 3 2 5% 6% 62%	4253
November	1st to 10th	Night	6% 6% 2 5% 3 3 3 3 4 6% 59%	2517
	11th to 20th	Night	9% 7% 3 5% 3 3 3 3 5% 9% 51%	2730
	21st to end	Night	8% 4 2 5% 4 3 4 3 5% 6% 56%	2793
December	1st to 10th	Night	6% 4 2 4 4 3 4 3 5% 6% 59%	4700
	11th to 20th	Night	11% 9% 3 8% 5% 4 5% 4 7% 9% 33%	5316
	21st to end	Night	13% 11% 4 10% 7% 6% 6% 4 5% 6% 27%	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% 7% 14% 24% 17% 5%	5041
	11th to 20th	Day	27% 4 7% 10% 22% 30%	5340
	21st to end	Day	38% 5% 6% 15% 24% 11%	5843
February	1st to 10th	Day	37% 5% 7% 19% 19% 13%	1890
	11th to 20th	Day	38% 7% 11% 17% 20% 7%	2017
	21st to end	Day	41% 5% 8% 22% 18% 6%	1730
March	1st to 10th	Day	45% 12% 10% 12% 18% 2	4802
	11th to 20th	Day	33% 8% 12% 29% 11% 7%	5000
	21st to end	Day	38% 12% 15% 23% 11% 2	5634
April	1st to 10th	Day	35% 7% 10% 26% 18% 4	2400
	11th to 20th	Day	31% 6% 12% 25% 20% 6%	2372
	21st to end	Day	27% 7% 12% 28% 21% 5%	2400
May	1st to 10th	Day	14% 4 8% 29% 37% 8%	5440
	11th to 20th	Day	13% 7% 10% 29% 32% 9%	5957
	21st to end	Day	16% 6% 10% 24% 38% 6%	6904
June	1st to 10th	Day	21% 7% 12% 23% 28% 10%	2800
	11th to 20th	Day	13% 3 8% 19% 35% 21%	2800
	21st to end	Day	11% 3 6% 12% 29% 39%	2800
July	1st to 10th	Day	5% 2 3 6% 20% 64%	6251
	11th to 20th	Day	7% 3 3 6% 15% 65%	5854
	21st to end	Day	9% 5% 7% 17% 28% 34%	6217
August	1st to 10th	Day	12% 2 4 10% 28% 45%	4206
	11th to 20th	Day	6% 2 4 8% 37% 44%	3884
	21st to end	Day	9% 3 5% 10% 31% 42%	4311
September	1st to 10th	Day	9% 4 3 10% 28% 46%	2400
	11th to 20th	Day	17% 4 6% 19% 35% 19%	2400
	21st to end	Day	12% 3 5% 19% 38% 23%	2150
October	1st to 10th	Day	14% 3 5% 11% 27% 41%	3280
	11th to 20th	Day	17% 6% 6% 20% 33% 18%	3261
	21st to end	Day	20% 5% 6% 20% 31% 18%	3558
November	1st to 10th	Day	26% 5% 9% 20% 25% 14%	2001
	11th to 20th	Day	31% 5% 10% 20% 23% 10%	1890
	21st to end	Day	28% 4 9% 19% 26% 14%	1822
December	1st to 10th	Day	27% 4 7% 19% 32% 10%	2700
	11th to 20th	Day	44% 6% 10% 15% 15% 10%	3108
	21st to end	Day	49% 8% 14% 16% 9% 4	4092
January	1st to 10th	Night	35% 8% 14% 21% 19% 4	7853
	11th to 20th	Night	27% 6% 8% 9% 25% 26%	7650
	21st to end	Night	40% 6% 7% 15% 20% 12%	8371
February	1st to 10th	Night	38% 5% 8% 16% 19% 14%	2730
	11th to 20th	Night	38% 7% 10% 17% 21% 6%	2501
	21st to end	Night	36% 5% 9% 26% 17% 6%	2076
March	1st to 10th	Night	50% 9% 9% 13% 16% 3	5123
	11th to 20th	Night	35% 9% 13% 21% 15% 8%	5000
	21st to end	Night	43% 11% 14% 19% 11% 3	5341
April	1st to 10th	Night	35% 7% 13% 23% 17% 5%	2000
	11th to 20th	Night	31% 6% 13% 25% 18% 6%	1979
	21st to end	Night	28% 7% 12% 27% 22% 5%	2000
May	1st to 10th	Night	19% 7% 9% 22% 31% 12%	4557
	11th to 20th	Night	24% 16% 13% 14% 23% 10%	3948
	21st to end	Night	20% 15% 10% 15% 33% 7%	3972
June	1st to 10th	Night	25% 9% 12% 18% 25% 11%	1600
	11th to 20th	Night	20% 5% 10% 13% 31% 21%	1600
	21st to end	Night	16% 5% 7% 13% 24% 36%	1600
July	1st to 10th	Night	9% 5% 5% 6% 15% 61%	3600
	11th to 20th	Night	13% 6% 6% 9% 11% 55%	3996
	21st to end	Night	20% 9% 25% 10% 17% 19%	4345
August	1st to 10th	Night	17% 3 5% 10% 18% 46%	2929
	11th to 20th	Night	12% 4 8% 8% 26% 43%	3251
	21st to end	Night	17% 6% 5% 9% 26% 37%	3608
September	1st to 10th	Night	14% 5% 5% 8% 24% 45%	2000
	11th to 20th	Night	21% 8% 6% 17% 28% 21%	2000
	21st to end	Night	15% 5% 5% 16% 35% 25%	2245
October	1st to 10th	Night	13% 3 6% 10% 22% 45%	3920
	11th to 20th	Night	22% 9% 8% 15% 25% 20%	3897
	21st to end	Night	23% 4 5% 20% 26% 22%	4253
November	1st to 10th	Night	26% 4 9% 21% 25% 16%	2517
	11th to 20th	Night	31% 6% 10% 20% 25% 9%	2730
	21st to end	Night	29% 4 10% 17% 24% 15%	2793
December	1st to 10th	Night	25% 5% 7% 21% 28% 15%	4700
	11th to 20th	Night	44% 7% 10% 14% 18% 7%	5316
	21st to end	Night	52% 11% 11% 14% 8% 4	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	23% 13% 24% 26% 13% 1	330
	11th to 20th	Day	11% 10% 22% 34% 21% 2	430
	21st to end	Day	16% 8% 27% 28% 19% 1	473
February	1st to 10th	Day	17% 12% 26% 22% 18% 4	430
	11th to 20th	Day	19% 14% 28% 26% 11% 1	513
	21st to end	Day	11% 14% 32% 30% 10% 2	446
March	1st to 10th	Day	20% 17% 30% 24% 9% 1	509
	11th to 20th	Day	19% 14% 29% 23% 11% 4	500
	21st to end	Day	15% 19% 33% 22% 9% 1	550
April	1st to 10th	Day	14% 15% 33% 22% 13% 3	500
	11th to 20th	Day	11% 19% 29% 25% 12% 4	492
	21st to end	Day	7% 18% 28% 28% 13% 6%	500
May	1st to 10th	Day	8% 15% 34% 27% 11% 5%	503
	11th to 20th	Day	9% 14% 32% 27% 13% 5%	528
	21st to end	Day	9% 13% 30% 30% 13% 5%	573
June	1st to 10th	Day	5% 6% 34% 31% 16% 8%	530
	11th to 20th	Day	3 10% 32% 33% 16% 6%	530
	21st to end	Day	3 5% 26% 36% 22% 8%	530
July	1st to 10th	Day	1 3 25% 42% 22% 8%	526
	11th to 20th	Day	1 2 13% 48% 25% 11%	524
	21st to end	Day	1 1 19% 43% 24% 12%	575
August	1st to 10th	Day	3 5% 25% 39% 19% 10%	527
	11th to 20th	Day	3 24% 39% 22% 12%	517
	21st to end	Day	1 2 18% 43% 24% 12%	583
September	1st to 10th	Day	2 4 19% 38% 25% 12%	530
	11th to 20th	Day	4 7% 28% 34% 19% 7%	530
	21st to end	Day	5% 5% 20% 37% 25% 8%	530
October	1st to 10th	Day	5% 8% 23% 32% 23% 8%	530
	11th to 20th	Day	6% 8% 23% 28% 26% 9%	530
	21st to end	Day	8% 8% 21% 33% 23% 7%	583
November	1st to 10th	Day	7% 9% 20% 31% 25% 8%	477
	11th to 20th	Day	9% 7% 20% 32% 25% 7%	330
	21st to end	Day	9% 5% 25% 34% 23% 5%	294
December	1st to 10th	Day	12% 8% 19% 35% 21% 5%	220
	11th to 20th	Day	15% 8% 21% 25% 25% 7%	220
	21st to end	Day	18% 13% 27% 26% 14% 2	242
January	1st to 10th	Night	15% 7% 15% 35% 20% 7%	840
	11th to 20th	Night	11% 5% 13% 37% 27% 7%	840
	21st to end	Night	15% 5% 13% 38% 24% 5%	924
February	1st to 10th	Night	17% 6% 15% 35% 22% 5%	840
	11th to 20th	Night	16% 7% 17% 34% 21% 6%	824
	21st to end	Night	12% 8% 16% 42% 18% 3	692
March	1st to 10th	Night	16% 9% 18% 33% 20% 4	808
	11th to 20th	Night	14% 5% 18% 36% 21% 6%	800
	21st to end	Night	13% 8% 19% 36% 21% 3	880
April	1st to 10th	Night	12% 5% 16% 39% 25% 3	800
	11th to 20th	Night	9% 8% 20% 32% 25% 6%	791
	21st to end	Night	8% 9% 19% 31% 27% 7%	800
May	1st to 10th	Night	6% 6% 19% 36% 27% 7%	800
	11th to 20th	Night	8% 6% 13% 35% 31% 8%	543
	21st to end	Night	6% 7% 17% 34% 30% 7%	433
June	1st to 10th	Night	6% 5% 13% 34% 35% 8%	400
	11th to 20th	Night	4 2 13% 40% 36% 6%	400
	21st to end	Night	2 4 5% 31% 50% 9%	400
July	1st to 10th	Night	1 3 7% 23% 57% 10%	390
	11th to 20th	Night	2 6% 16% 53% 23%	558
	21st to end	Night	1 9% 15% 56% 19%	657
August	1st to 10th	Night	3 2 8% 22% 49% 15%	597
	11th to 20th	Night	2 2 7% 33% 45% 12%	787
	21st to end	Night	2 2 6% 23% 51% 15%	880
September	1st to 10th	Night	2 2 6% 25% 51% 14%	800
	11th to 20th	Night	4 4 8% 30% 43% 12%	800
	21st to end	Night	4 2 7% 31% 41% 15%	800
October	1st to 10th	Night	6% 2 8% 36% 37% 12%	800
	11th to 20th	Night	7% 3 10% 33% 34% 13%	800
	21st to end	Night	6% 4 11% 33% 30% 16%	880
November	1st to 10th	Night	7% 4 13% 34% 31% 11%	820
	11th to 20th	Night	13% 3 12% 35% 29% 8%	840
	21st to end	Night	9% 3 15% 40% 27% 6%	840
December	1st to 10th	Night	12% 5% 14% 38% 25% 6%	840
	11th to 20th	Night	17% 7% 13% 36% 23% 4	840
	21st to end	Night	18% 7% 20% 35% 17% 4	924

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

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