Stage Line Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stage Line Ranch 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	8% 7% 3 7% 4 4 4 3 5% 6% 48%	134363
	Night	10% 9% 3 7% 4 4 4 3 5% 7% 44%	135489
Transparency	Day	36% 5% 11% 22% 19% 7%	134090
	Night	40% 5% 11% 22% 16% 6%	135340
Seeing	Day	11% 7% 22% 29% 23% 10%	15793
	Night	14% 5% 21% 36% 21% 3	25339

By Month

Percentage Cloud Cover NW (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% 17% 8% 15% 5% 5% 5% 3 5% 5% 16%	4723
	11th to 20th	Day	10% 7% 3 9% 5% 4 5% 3 5% 7% 41%	4716
	21st to end	Day	16% 15% 4 10% 4 3 4 3 4 5% 32%	5186
February	1st to 10th	Day	13% 12% 5% 10% 6% 6% 5% 4 5% 6% 28%	1743
	11th to 20th	Day	12% 12% 4 9% 5% 6% 4 3 5% 7% 33%	1919
	21st to end	Day	10% 12% 5% 10% 6% 4 5% 4 4 6% 34%	1730
March	1st to 10th	Day	7% 7% 2 6% 5% 6% 6% 6% 8% 9% 38%	4539
	11th to 20th	Day	7% 9% 3 8% 5% 4 4 3 5% 6% 46%	4682
	21st to end	Day	10% 9% 3 8% 6% 6% 6% 5% 7% 8% 31%	5969
April	1st to 10th	Day	10% 9% 3 8% 6% 5% 6% 6% 6% 8% 33%	2400
	11th to 20th	Day	6% 8% 2 7% 5% 5% 5% 4 6% 9% 42%	2389
	21st to end	Day	7% 7% 3 8% 5% 5% 4 4 6% 7% 45%	2607
May	1st to 10th	Day	7% 6% 2 5% 3 3 4 4 5% 8% 53%	6320
	11th to 20th	Day	9% 7% 3 7% 5% 5% 5% 4 6% 8% 44%	6277
	21st to end	Day	6% 6% 2 6% 5% 4 5% 4 6% 8% 48%	6903
June	1st to 10th	Day	11% 6% 2 6% 5% 4 5% 3 6% 7% 45%	2800
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 4 7% 7% 47%	2800
	21st to end	Day	4 4 2 5% 3 4 3 4 5% 7% 60%	2800
July	1st to 10th	Day	2 2 1 3 2 2 2 2 4 4 76%	6320
	11th to 20th	Day	1 2 1 2 2 2 2 2 3 3 81%	6320
	21st to end	Day	3 2 1 2 2 2 2 2 4 6% 75%	6874
August	1st to 10th	Day	3 2 1 3 2 2 3 2 3 6% 71%	4541
	11th to 20th	Day	2 2 1 3 2 3 3 3 5% 6% 71%	4327
	21st to end	Day	3 4 2 5% 3 3 4 3 5% 6% 63%	4312
September	1st to 10th	Day	4 3 1 3 2 2 3 3 5% 6% 69%	2400
	11th to 20th	Day	5% 4 2 5% 3 4 4 4 6% 8% 56%	2332
	21st to end	Day	6% 5% 1 5% 3 4 4 4 4 7% 56%	2200
October	1st to 10th	Day	6% 4 2 4 3 3 3 3 6% 7% 60%	3359
	11th to 20th	Day	7% 5% 2 6% 5% 5% 6% 5% 6% 7% 47%	3142
	21st to end	Day	11% 8% 3 6% 4 4 4 4 5% 7% 45%	3200
November	1st to 10th	Day	18% 9% 3 8% 5% 5% 4 4 5% 6% 33%	1854
	11th to 20th	Day	15% 12% 3 9% 6% 5% 6% 4 5% 6% 29%	1726
	21st to end	Day	13% 15% 5% 11% 6% 4 5% 4 5% 7% 24%	1680
December	1st to 10th	Day	12% 11% 5% 13% 5% 5% 5% 5% 6% 7% 27%	2404
	11th to 20th	Day	19% 19% 7% 14% 6% 4 4 3 4 4 15%	2777
	21st to end	Day	17% 18% 8% 14% 5% 4 4 3 4 5% 17%	4092
January	1st to 10th	Night	19% 18% 6% 11% 5% 5% 5% 3 4 5% 19%	8172
	11th to 20th	Night	10% 8% 3 8% 5% 4 4 3 5% 7% 42%	8182
	21st to end	Night	14% 14% 6% 9% 4 4 3 3 4 5% 35%	8994
February	1st to 10th	Night	13% 13% 4 8% 5% 5% 4 4 6% 7% 32%	2872
	11th to 20th	Night	11% 11% 4 9% 5% 4 4 4 6% 7% 35%	2587
	21st to end	Night	11% 11% 3 8% 6% 5% 5% 4 5% 8% 33%	2076
March	1st to 10th	Night	6% 7% 2 7% 5% 5% 5% 5% 7% 9% 43%	5400
	11th to 20th	Night	9% 10% 3 6% 4 3 4 3 4 6% 46%	5304
	21st to end	Night	8% 9% 3 9% 7% 7% 7% 5% 9% 9% 27%	5006
April	1st to 10th	Night	9% 8% 2 8% 6% 5% 5% 4 6% 8% 39%	2000
	11th to 20th	Night	6% 9% 3 6% 5% 4 5% 3 5% 6% 47%	1961
	21st to end	Night	5% 7% 2 6% 7% 5% 5% 5% 7% 8% 43%	1790
May	1st to 10th	Night	5% 4 2 5% 4 5% 4 4 5% 8% 54%	3640
	11th to 20th	Night	7% 7% 3 8% 4 5% 3 4 5% 8% 46%	3616
	21st to end	Night	5% 4 2 5% 5% 4 4 4 6% 9% 54%	3972
June	1st to 10th	Night	7% 6% 2 6% 4 4 4 4 6% 9% 48%	1600
	11th to 20th	Night	6% 6% 2 6% 3 4 6% 4 6% 8% 50%	1581
	21st to end	Night	5% 3 2 4 4 4 4 3 5% 7% 60%	1600
July	1st to 10th	Night	3 2 1 1 1 1 2 2 3 5% 79%	3640
	11th to 20th	Night	1 1 1 1 1 1 1 1 2 4 85%	3640
	21st to end	Night	2 2 1 1 2 2 1 2 4 4 80%	3969
August	1st to 10th	Night	4 2 1 3 3 1 2 2 3 6% 73%	2609
	11th to 20th	Night	2 3 1 5% 4 3 4 3 4 5% 66%	2722
	21st to end	Night	2 2 1 4 3 3 4 3 5% 5% 66%	3608
September	1st to 10th	Night	3 2 1 3 3 2 3 4 5% 7% 67%	2000
	11th to 20th	Night	4 4 2 5% 3 4 3 4 6% 8% 57%	2067
	21st to end	Night	6% 4 2 5% 3 3 4 4 7% 7% 56%	2200
October	1st to 10th	Night	6% 3 1 4 2 3 4 3 5% 8% 60%	3838
	11th to 20th	Night	8% 5% 2 5% 4 4 4 5% 6% 8% 50%	4011
	21st to end	Night	12% 6% 2 6% 4 5% 5% 4 4 6% 46%	4600
November	1st to 10th	Night	16% 10% 3 7% 5% 4 5% 3 6% 6% 35%	2665
	11th to 20th	Night	15% 10% 3 8% 5% 4 5% 4 5% 6% 33%	2893
	21st to end	Night	16% 12% 4 10% 5% 5% 5% 3 5% 6% 29%	2940
December	1st to 10th	Night	8% 9% 5% 10% 5% 4 4 4 6% 8% 37%	4956
	11th to 20th	Night	19% 17% 8% 14% 7% 4 5% 4 5% 5% 13%	5672
	21st to end	Night	20% 17% 6% 11% 5% 5% 4 3 4 5% 20%	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	69% 6% 8% 11% 5%	4723
	11th to 20th	Day	43% 6% 19% 22% 9% 1	4740
	21st to end	Day	57% 4 12% 19% 8%	5187
February	1st to 10th	Day	58% 8% 14% 12% 7% 1	1743
	11th to 20th	Day	51% 8% 14% 18% 9%	1928
	21st to end	Day	50% 7% 14% 19% 9% 1	1730
March	1st to 10th	Day	40% 6% 12% 22% 19% 1	4539
	11th to 20th	Day	38% 4 11% 32% 15%	4682
	21st to end	Day	48% 8% 17% 19% 8% 1	5969
April	1st to 10th	Day	46% 8% 13% 22% 10% 2	2400
	11th to 20th	Day	38% 6% 15% 23% 16% 3	2389
	21st to end	Day	37% 6% 13% 24% 17% 3	2607
May	1st to 10th	Day	29% 4 7% 23% 34% 3	6320
	11th to 20th	Day	36% 6% 10% 25% 19% 3	6280
	21st to end	Day	33% 6% 14% 30% 16% 2	6904
June	1st to 10th	Day	38% 6% 9% 22% 20% 5%	2800
	11th to 20th	Day	35% 5% 11% 25% 18% 6%	2800
	21st to end	Day	24% 4 9% 29% 26% 8%	2800
July	1st to 10th	Day	14% 2 5% 18% 28% 33%	6251
	11th to 20th	Day	10% 2 4 17% 32% 36%	6245
	21st to end	Day	13% 2 4 25% 34% 21%	6681
August	1st to 10th	Day	16% 2 5% 17% 37% 22%	4524
	11th to 20th	Day	15% 3 7% 36% 31% 7%	4369
	21st to end	Day	23% 4 8% 29% 30% 7%	4311
September	1st to 10th	Day	17% 4 10% 27% 29% 14%	2400
	11th to 20th	Day	26% 6% 12% 25% 24% 7%	2332
	21st to end	Day	28% 5% 16% 32% 15% 5%	2200
October	1st to 10th	Day	25% 4 12% 38% 21% 1	3359
	11th to 20th	Day	35% 6% 17% 24% 17% 1	3142
	21st to end	Day	39% 5% 15% 25% 12% 3	3200
November	1st to 10th	Day	50% 7% 15% 19% 8% 1	1854
	11th to 20th	Day	55% 9% 15% 15% 5% 2	1726
	21st to end	Day	59% 11% 12% 12% 5% 1	1680
December	1st to 10th	Day	55% 9% 17% 16% 4	2404
	11th to 20th	Day	74% 6% 8% 10% 3	2779
	21st to end	Day	71% 6% 11% 9% 4	4092
January	1st to 10th	Night	67% 7% 11% 13% 2	8172
	11th to 20th	Night	41% 7% 16% 25% 10% 1	8220
	21st to end	Night	53% 5% 14% 21% 8%	8994
February	1st to 10th	Night	52% 7% 16% 15% 9% 1	2872
	11th to 20th	Night	49% 7% 16% 17% 10% 1	2589
	21st to end	Night	46% 7% 14% 20% 11% 1	2076
March	1st to 10th	Night	35% 6% 10% 25% 22% 2	5400
	11th to 20th	Night	39% 4 9% 30% 18% 1	5305
	21st to end	Night	48% 8% 15% 21% 7%	5006
April	1st to 10th	Night	42% 6% 13% 26% 12% 2	2000
	11th to 20th	Night	37% 5% 11% 24% 19% 4	1961
	21st to end	Night	35% 6% 11% 23% 20% 4	1790
May	1st to 10th	Night	28% 4 7% 22% 35% 4	3637
	11th to 20th	Night	35% 6% 9% 28% 21% 2	3616
	21st to end	Night	27% 7% 14% 34% 17% 1	3972
June	1st to 10th	Night	32% 6% 10% 23% 24% 6%	1600
	11th to 20th	Night	32% 5% 8% 27% 21% 7%	1581
	21st to end	Night	24% 4 9% 26% 28% 9%	1600
July	1st to 10th	Night	11% 1 4 17% 32% 35%	3600
	11th to 20th	Night	8% 1 3 17% 29% 42%	3592
	21st to end	Night	10% 1 4 20% 35% 29%	3857
August	1st to 10th	Night	15% 2 5% 14% 38% 27%	2601
	11th to 20th	Night	21% 4 5% 25% 35% 11%	2746
	21st to end	Night	19% 4 7% 26% 30% 14%	3608
September	1st to 10th	Night	17% 4 7% 25% 30% 18%	2000
	11th to 20th	Night	25% 5% 10% 26% 25% 10%	2067
	21st to end	Night	26% 5% 12% 30% 19% 8%	2200
October	1st to 10th	Night	23% 3 8% 39% 26% 1	3838
	11th to 20th	Night	32% 5% 15% 24% 22% 3	4011
	21st to end	Night	39% 5% 10% 30% 14% 2	4600
November	1st to 10th	Night	49% 7% 16% 18% 9% 2	2665
	11th to 20th	Night	51% 9% 15% 17% 7% 2	2893
	21st to end	Night	56% 8% 13% 15% 7% 1	2940
December	1st to 10th	Night	45% 10% 17% 24% 4	4956
	11th to 20th	Night	72% 6% 11% 8% 3	5669
	21st to end	Night	67% 6% 10% 11% 5%	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	21% 8% 32% 21% 15% 3	220
	11th to 20th	Day	22% 4 17% 32% 20% 5%	220
	21st to end	Day	22% 5% 21% 29% 21% 2	242
February	1st to 10th	Day	15% 8% 25% 33% 16% 3	283
	11th to 20th	Day	17% 10% 25% 27% 16% 5%	464
	21st to end	Day	14% 12% 29% 27% 14% 4	446
March	1st to 10th	Day	14% 8% 30% 30% 12% 5%	509
	11th to 20th	Day	12% 10% 22% 29% 20% 6%	500
	21st to end	Day	14% 11% 30% 26% 15% 3	550
April	1st to 10th	Day	14% 9% 26% 29% 14% 7%	500
	11th to 20th	Day	11% 13% 28% 27% 14% 7%	492
	21st to end	Day	7% 9% 26% 29% 21% 8%	500
May	1st to 10th	Day	9% 6% 24% 33% 22% 7%	503
	11th to 20th	Day	13% 7% 18% 27% 24% 11%	528
	21st to end	Day	9% 5% 19% 27% 23% 17%	573
June	1st to 10th	Day	11% 7% 19% 26% 24% 13%	530
	11th to 20th	Day	7% 7% 29% 33% 17% 6%	530
	21st to end	Day	3 4 20% 30% 29% 14%	530
July	1st to 10th	Day	3 3 15% 37% 33% 9%	526
	11th to 20th	Day	2 3 18% 28% 34% 15%	524
	21st to end	Day	2 2 14% 30% 36% 17%	575
August	1st to 10th	Day	4 3 12% 30% 31% 19%	527
	11th to 20th	Day	2 2 12% 28% 34% 22%	517
	21st to end	Day	6% 4 18% 25% 30% 17%	583
September	1st to 10th	Day	6% 2 16% 27% 31% 18%	530
	11th to 20th	Day	7% 4 17% 28% 32% 12%	530
	21st to end	Day	7% 7% 22% 29% 27% 8%	530
October	1st to 10th	Day	10% 5% 23% 31% 22% 8%	530
	11th to 20th	Day	13% 6% 21% 29% 23% 8%	462
	21st to end	Day	15% 10% 27% 29% 14% 5%	363
November	1st to 10th	Day	21% 9% 19% 35% 15% 1	330
	11th to 20th	Day	21% 12% 21% 23% 16% 6%	244
	21st to end	Day	20% 6% 22% 31% 17% 4	220
December	1st to 10th	Day	24% 7% 20% 23% 18% 8%	220
	11th to 20th	Day	23% 10% 28% 25% 13% 2	220
	21st to end	Day	21% 9% 24% 32% 12% 2	242
January	1st to 10th	Night	27% 10% 21% 29% 10% 2	840
	11th to 20th	Night	22% 5% 21% 34% 15% 3	840
	21st to end	Night	20% 4 20% 38% 18% 2	924
February	1st to 10th	Night	18% 7% 27% 34% 13% 2	840
	11th to 20th	Night	16% 5% 26% 34% 17% 2	824
	21st to end	Night	16% 8% 27% 32% 13% 3	692
March	1st to 10th	Night	15% 6% 23% 35% 19% 2	808
	11th to 20th	Night	13% 8% 24% 34% 20% 2	800
	21st to end	Night	13% 6% 32% 33% 14% 2	880
April	1st to 10th	Night	12% 7% 25% 33% 20% 3	800
	11th to 20th	Night	10% 8% 29% 36% 15% 2	773
	21st to end	Night	7% 8% 27% 36% 20% 2	590
May	1st to 10th	Night	9% 6% 26% 34% 23% 3	400
	11th to 20th	Night	11% 6% 19% 30% 30% 5%	394
	21st to end	Night	8% 3 18% 38% 28% 4	433
June	1st to 10th	Night	8% 4 22% 40% 24% 3	400
	11th to 20th	Night	8% 5% 28% 39% 19% 2	400
	21st to end	Night	6% 2 21% 39% 28% 5%	400
July	1st to 10th	Night	4 2 11% 47% 33% 4	390
	11th to 20th	Night	3 1 19% 43% 32% 3	388
	21st to end	Night	1 2 11% 43% 39% 3	438
August	1st to 10th	Night	3 2 11% 38% 38% 8%	398
	11th to 20th	Night	2 1 11% 38% 38% 9%	476
	21st to end	Night	4 3 14% 37% 37% 5%	880
September	1st to 10th	Night	4 2 14% 43% 33% 6%	800
	11th to 20th	Night	6% 2 15% 34% 35% 9%	800
	21st to end	Night	8% 3 19% 37% 28% 5%	800
October	1st to 10th	Night	11% 4 18% 37% 27% 3	800
	11th to 20th	Night	13% 6% 21% 33% 25% 3	800
	21st to end	Night	15% 5% 24% 36% 16% 4	880
November	1st to 10th	Night	20% 7% 20% 41% 10%	820
	11th to 20th	Night	19% 8% 26% 31% 13% 3	840
	21st to end	Night	22% 5% 19% 31% 20% 2	840
December	1st to 10th	Night	17% 6% 18% 39% 17% 2	992
	11th to 20th	Night	24% 8% 20% 35% 11% 1	1035
	21st to end	Night	25% 6% 23% 35% 10% 1	924

Page generated at 2026-02-27 22:40:19. Version ac07

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