Furnace Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Furnace Creek clear sky chart from 2005-11-06 to 2025-09-04.

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	1 1 1 2 1 2 2 2 3 5% 79%	134727
	Night	1 2 1 2 2 2 2 2 4 6% 77%	131452
Transparency	Day	9% 3 5% 13% 24% 45%	129759
	Night	11% 4 5% 14% 25% 42%	127399
Seeing	Day	6% 10% 30% 33% 18% 4	16373
	Night	4 7% 22% 38% 25% 3	26067

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	1 1 1 2 2 2 3 3 5% 7% 74%	3639
	11th to 20th	Day	1 1 1 3 2 2 2 2 3 6% 77%	3704
	21st to end	Day	3 3 1 4 3 3 3 3 5% 8% 63%	4878
February	1st to 10th	Day	2 2 1 2 1 3 3 2 5% 8% 70%	2000
	11th to 20th	Day	2 2 1 2 2 2 4 3 4 9% 70%	1950
	21st to end	Day	2 2 1 2 2 3 4 3 5% 5% 71%	1650
March	1st to 10th	Day	1 3 1 4 3 3 3 2 5% 8% 69%	4518
	11th to 20th	Day	3 3 1 3 2 2 3 3 5% 8% 67%	4777
	21st to end	Day	1 1 1 2 2 2 3 3 5% 9% 71%	5766
April	1st to 10th	Day	1 1 1 2 2 2 3 3 5% 6% 74%	2400
	11th to 20th	Day	1 2 1 1 2 2 2 2 4 5% 78%	2369
	21st to end	Day	1 1 2 2 2 2 2 4 5% 79%	2445
May	1st to 10th	Day	2 2 1 2 1 2 2 2 3 5% 80%	5880
	11th to 20th	Day	1 1 1 1 2 2 3 4 84%	5841
	21st to end	Day	1 1 1 1 1 2 3 5% 85%	6423
June	1st to 10th	Day	1 1 1 2 2 2 4 6% 81%	2655
	11th to 20th	Day	1 1 1 2 1 3 4 87%	2800
	21st to end	Day	1 1 1 1 1 1 1 2 3 88%	2800
July	1st to 10th	Day	1 1 1 1 1 1 1 2 2 90%	6319
	11th to 20th	Day	1 1 1 1 1 1 2 3 3 85%	6276
	21st to end	Day	1 1 1 1 1 1 1 2 4 86%	6401
August	1st to 10th	Day	1 1 1 2 1 1 2 2 3 4 83%	5523
	11th to 20th	Day	1 1 1 2 94%	5364
	21st to end	Day	1 1 2 1 2 2 1 2 3 84%	5981
September	1st to 10th	Day	1 1 2 1 1 2 2 2 4 83%	2312
	11th to 20th	Day	1 1 1 1 1 2 2 91%	2090
	21st to end	Day	1 1 1 1 1 2 3 90%	2090
October	1st to 10th	Day	1 1 1 1 1 1 2 3 89%	3490
	11th to 20th	Day	1 1 1 2 1 2 2 4 85%	3378
	21st to end	Day	1 1 1 3 1 1 2 1 3 6% 81%	3143
November	1st to 10th	Day	1 1 1 2 1 2 2 4 6% 80%	1764
	11th to 20th	Day	1 2 1 1 1 2 2 2 3 6% 80%	1800
	21st to end	Day	2 1 1 2 1 2 2 3 6% 7% 74%	1800
December	1st to 10th	Day	1 1 1 2 2 2 4 4 5% 7% 71%	2950
	11th to 20th	Day	1 3 1 3 2 3 3 4 7% 10% 62%	3409
	21st to end	Day	2 2 1 4 3 3 4 4 7% 10% 59%	4142
January	1st to 10th	Night	1 3 1 2 2 2 3 2 4 6% 73%	6306
	11th to 20th	Night	1 2 1 3 2 2 2 2 3 5% 77%	6253
	21st to end	Night	4 3 1 3 2 3 4 3 5% 7% 65%	6099
February	1st to 10th	Night	3 2 1 4 3 3 3 3 5% 7% 67%	2400
	11th to 20th	Night	2 2 1 3 3 3 3 3 5% 7% 68%	2338
	21st to end	Night	3 3 1 3 1 2 2 3 4 6% 73%	1980
March	1st to 10th	Night	1 3 1 3 3 3 4 3 5% 6% 68%	5376
	11th to 20th	Night	4 3 2 4 3 3 3 3 5% 8% 63%	5221
	21st to end	Night	1 2 1 3 2 2 3 3 5% 7% 70%	5192
April	1st to 10th	Night	1 2 1 2 2 2 3 3 5% 7% 74%	2000
	11th to 20th	Night	1 1 1 2 2 2 2 2 4 5% 78%	1979
	21st to end	Night	1 1 2 2 2 2 3 4 6% 78%	1954
May	1st to 10th	Night	1 2 1 3 2 2 2 2 3 4 79%	4100
	11th to 20th	Night	1 1 2 1 1 1 1 3 3 84%	4074
	21st to end	Night	1 2 1 1 2 1 3 4 85%	4474
June	1st to 10th	Night	1 1 1 2 2 2 3 5% 83%	1739
	11th to 20th	Night	1 1 1 1 1 1 2 3 4 86%	1600
	21st to end	Night	1 1 1 1 1 1 2 2 4 87%	1600
July	1st to 10th	Night	1 1 1 1 1 1 2 92%	3640
	11th to 20th	Night	1 1 1 1 1 2 2 3 4 84%	3681
	21st to end	Night	1 1 1 2 2 2 3 4 84%	4472
August	1st to 10th	Night	1 1 1 1 2 1 2 3 4 85%	4296
	11th to 20th	Night	1 1 1 1 2 93%	4506
	21st to end	Night	1 1 1 1 1 2 2 2 4 4 82%	5015
September	1st to 10th	Night	1 1 1 2 1 1 2 2 3 3 82%	1933
	11th to 20th	Night	1 1 1 1 1 3 3 88%	2090
	21st to end	Night	1 1 1 1 3 4 89%	2090
October	1st to 10th	Night	1 1 1 1 1 1 2 3 89%	3490
	11th to 20th	Night	1 1 1 2 1 1 2 5% 86%	3555
	21st to end	Night	1 2 1 2 1 1 1 2 2 4 83%	4413
November	1st to 10th	Night	1 1 1 2 2 1 2 2 3 6% 81%	2535
	11th to 20th	Night	1 1 1 2 2 2 2 2 5% 5% 78%	2600
	21st to end	Night	2 2 1 2 1 2 2 2 4 7% 75%	2600
December	1st to 10th	Night	1 2 1 2 2 2 3 4 5% 7% 71%	4240
	11th to 20th	Night	1 2 1 3 2 2 3 3 6% 11% 66%	4811
	21st to end	Night	1 3 1 5% 4 4 5% 4 7% 11% 55%	6800

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	12% 5% 6% 34% 31% 13%	3639
	11th to 20th	Day	13% 4 10% 22% 21% 30%	3704
	21st to end	Day	18% 6% 8% 24% 23% 21%	4878
February	1st to 10th	Day	16% 5% 8% 20% 32% 20%	2000
	11th to 20th	Day	13% 5% 7% 21% 34% 20%	1960
	21st to end	Day	15% 6% 8% 20% 32% 19%	1650
March	1st to 10th	Day	15% 5% 4 23% 30% 23%	4518
	11th to 20th	Day	15% 7% 7% 28% 27% 16%	4777
	21st to end	Day	10% 5% 8% 22% 34% 20%	5766
April	1st to 10th	Day	12% 5% 5% 17% 33% 27%	2400
	11th to 20th	Day	10% 3 5% 14% 31% 37%	2372
	21st to end	Day	10% 3 4 13% 37% 32%	2445
May	1st to 10th	Day	9% 3 5% 12% 32% 38%	5880
	11th to 20th	Day	5% 3 2 7% 29% 53%	5844
	21st to end	Day	5% 2 3 7% 27% 57%	6424
June	1st to 10th	Day	8% 3 3 9% 23% 55%	2655
	11th to 20th	Day	4 2 2 6% 17% 70%	2800
	21st to end	Day	5% 1 2 3 11% 78%	2800
July	1st to 10th	Day	4 1 1 2 8% 82%	6251
	11th to 20th	Day	6% 2 2 4 10% 76%	6201
	21st to end	Day	6% 2 2 6% 15% 69%	6217
August	1st to 10th	Day	9% 2 2 5% 21% 61%	4020
	11th to 20th	Day	3 1 2 3 11% 80%	3880
	21st to end	Day	4 1 2 3 13% 77%	4311
September	1st to 10th	Day	8% 3 4 4 15% 66%	2312
	11th to 20th	Day	3 1 2 6% 24% 63%	2090
	21st to end	Day	4 1 2 7% 27% 59%	2090
October	1st to 10th	Day	5% 2 2 7% 21% 64%	3490
	11th to 20th	Day	6% 3 2 7% 29% 53%	3378
	21st to end	Day	7% 4 2 9% 36% 42%	3143
November	1st to 10th	Day	9% 2 5% 16% 42% 26%	1764
	11th to 20th	Day	9% 4 5% 19% 38% 25%	1800
	21st to end	Day	12% 4 7% 21% 34% 23%	1800
December	1st to 10th	Day	12% 6% 8% 17% 31% 26%	2950
	11th to 20th	Day	16% 8% 11% 24% 31% 10%	3408
	21st to end	Day	20% 7% 11% 30% 24% 8%	4142
January	1st to 10th	Night	13% 4 5% 30% 33% 14%	6306
	11th to 20th	Night	13% 3 7% 25% 26% 27%	6253
	21st to end	Night	19% 6% 7% 20% 23% 25%	6099
February	1st to 10th	Night	19% 5% 8% 18% 29% 22%	2400
	11th to 20th	Night	17% 4 6% 19% 30% 24%	2339
	21st to end	Night	14% 5% 5% 19% 33% 23%	1980
March	1st to 10th	Night	16% 5% 6% 18% 29% 27%	5376
	11th to 20th	Night	18% 6% 7% 24% 29% 15%	5221
	21st to end	Night	12% 5% 5% 21% 38% 19%	5192
April	1st to 10th	Night	11% 5% 6% 15% 34% 29%	2000
	11th to 20th	Night	11% 4 5% 12% 31% 36%	1979
	21st to end	Night	9% 3 5% 12% 33% 38%	1954
May	1st to 10th	Night	11% 4 3 11% 28% 43%	4097
	11th to 20th	Night	6% 2 2 8% 29% 52%	4075
	21st to end	Night	6% 2 2 5% 24% 60%	4474
June	1st to 10th	Night	7% 3 2 9% 19% 60%	1739
	11th to 20th	Night	6% 3 2 6% 14% 70%	1600
	21st to end	Night	5% 2 2 3 9% 80%	1600
July	1st to 10th	Night	3 1 1 1 7% 86%	3600
	11th to 20th	Night	6% 3 2 5% 11% 74%	3633
	21st to end	Night	6% 3 2 5% 12% 72%	4344
August	1st to 10th	Night	8% 2 2 5% 15% 68%	3117
	11th to 20th	Night	3 2 2 3 10% 80%	3256
	21st to end	Night	4 1 1 3 11% 79%	3608
September	1st to 10th	Night	9% 2 2 6% 13% 68%	1933
	11th to 20th	Night	4 2 2 7% 20% 64%	2090
	21st to end	Night	4 1 2 5% 23% 66%	2090
October	1st to 10th	Night	4 2 2 6% 13% 72%	3490
	11th to 20th	Night	5% 2 2 4 20% 66%	3555
	21st to end	Night	8% 3 2 6% 31% 49%	4413
November	1st to 10th	Night	9% 2 4 15% 39% 31%	2535
	11th to 20th	Night	10% 4 6% 15% 33% 32%	2600
	21st to end	Night	13% 3 6% 16% 33% 29%	2600
December	1st to 10th	Night	13% 6% 5% 15% 32% 29%	4240
	11th to 20th	Night	14% 7% 8% 25% 32% 13%	4811
	21st to end	Night	22% 8% 10% 30% 23% 7%	6800

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	11% 10% 37% 32% 10% 2	200
	11th to 20th	Day	10% 12% 31% 29% 16% 1	213
	21st to end	Day	8% 9% 30% 32% 19% 2	490
February	1st to 10th	Day	11% 12% 33% 27% 14% 2	500
	11th to 20th	Day	12% 14% 38% 24% 11% 2	495
	21st to end	Day	10% 14% 42% 25% 9%	414
March	1st to 10th	Day	11% 18% 35% 25% 10%	500
	11th to 20th	Day	13% 16% 36% 25% 11%	500
	21st to end	Day	9% 21% 35% 25% 8% 1	550
April	1st to 10th	Day	8% 17% 31% 27% 15% 2	500
	11th to 20th	Day	10% 18% 34% 25% 10% 3	492
	21st to end	Day	6% 17% 33% 30% 12% 3	500
May	1st to 10th	Day	7% 15% 36% 25% 12% 5%	503
	11th to 20th	Day	4 14% 32% 32% 14% 4	528
	21st to end	Day	3 12% 30% 36% 15% 4	573
June	1st to 10th	Day	3 8% 28% 35% 18% 8%	530
	11th to 20th	Day	2 10% 33% 35% 16% 5%	530
	21st to end	Day	1 7% 26% 40% 19% 6%	530
July	1st to 10th	Day	2 2 27% 38% 23% 8%	526
	11th to 20th	Day	2 1 20% 39% 27% 11%	524
	21st to end	Day	2 2 21% 42% 24% 10%	575
August	1st to 10th	Day	3 4 27% 36% 22% 8%	527
	11th to 20th	Day	1 3 21% 41% 26% 9%	517
	21st to end	Day	2 3 22% 39% 26% 8%	583
September	1st to 10th	Day	2 4 21% 40% 26% 7%	503
	11th to 20th	Day	2 9% 30% 38% 18% 4	490
	21st to end	Day	4 7% 24% 39% 23% 3	490
October	1st to 10th	Day	3 8% 28% 33% 24% 3	490
	11th to 20th	Day	5% 6% 24% 41% 22% 2	490
	21st to end	Day	6% 7% 26% 33% 24% 4	360
November	1st to 10th	Day	5% 7% 31% 33% 19% 4	300
	11th to 20th	Day	6% 6% 33% 33% 15% 7%	300
	21st to end	Day	4 9% 32% 32% 21% 2	300
December	1st to 10th	Day	4 5% 33% 38% 18% 1	300
	11th to 20th	Day	6% 8% 32% 32% 18% 4	300
	21st to end	Day	12% 10% 35% 28% 14% 2	250
January	1st to 10th	Night	7% 9% 23% 33% 24% 4	800
	11th to 20th	Night	4 8% 26% 39% 20% 4	800
	21st to end	Night	7% 10% 23% 36% 21% 3	880
February	1st to 10th	Night	8% 10% 24% 36% 19% 3	800
	11th to 20th	Night	7% 9% 27% 35% 18% 3	784
	21st to end	Night	7% 13% 28% 35% 15% 2	660
March	1st to 10th	Night	7% 13% 28% 35% 15% 3	800
	11th to 20th	Night	7% 12% 26% 30% 22% 3	800
	21st to end	Night	7% 14% 27% 34% 17% 1	880
April	1st to 10th	Night	6% 12% 28% 37% 17% 2	800
	11th to 20th	Night	5% 11% 33% 31% 18% 2	791
	21st to end	Night	3 10% 28% 35% 21% 4	754
May	1st to 10th	Night	6% 9% 30% 37% 16% 3	600
	11th to 20th	Night	4 9% 23% 37% 25% 2	591
	21st to end	Night	3 9% 24% 37% 25% 2	650
June	1st to 10th	Night	2 5% 19% 42% 30% 2	539
	11th to 20th	Night	2 4 19% 45% 28% 3	400
	21st to end	Night	1 2 18% 40% 37% 3	400
July	1st to 10th	Night	1 16% 44% 35% 4	390
	11th to 20th	Night	2 8% 51% 36% 1	403
	21st to end	Night	1 1 14% 47% 35% 2	657
August	1st to 10th	Night	1 3 20% 46% 29% 1	708
	11th to 20th	Night	1 1 14% 44% 38% 3	792
	21st to end	Night	2 1 13% 43% 36% 4	880
September	1st to 10th	Night	1 3 14% 39% 39% 4	772
	11th to 20th	Night	1 4 20% 38% 32% 4	760
	21st to end	Night	5% 18% 39% 33% 5%	760
October	1st to 10th	Night	2 5% 22% 43% 24% 4	760
	11th to 20th	Night	4 5% 19% 38% 28% 7%	760
	21st to end	Night	3 8% 20% 33% 30% 6%	836
November	1st to 10th	Night	4 6% 19% 37% 29% 6%	780
	11th to 20th	Night	2 5% 23% 37% 28% 4	800
	21st to end	Night	4 7% 25% 35% 25% 4	800
December	1st to 10th	Night	5% 7% 25% 36% 25% 3	800
	11th to 20th	Night	7% 10% 22% 37% 22% 2	800
	21st to end	Night	6% 10% 27% 33% 21% 3	880

Page generated at 2025-08-31 22:51:03. Version ac07

Copyright © 2025 Attilla Danko.