Knudson Forestry Service Road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Knudson Forestry Service Road clear sky chart from 2005-11-06 to 2026-02-16.

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% 10% 4 9% 6% 5% 6% 4 6% 7% 36%	134361
	Night	6% 12% 4 10% 6% 6% 6% 5% 6% 7% 33%	135125
Transparency	Day	44% 9% 15% 19% 10% 3	134077
	Night	46% 10% 16% 18% 8% 2	134987
Seeing	Day	17% 17% 29% 22% 12% 4	16693
	Night	14% 11% 26% 31% 16% 2	25364

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	7% 19% 7% 16% 8% 7% 7% 4 6% 6% 13%	4125
	11th to 20th	Day	5% 10% 4 11% 6% 6% 5% 5% 7% 8% 34%	4655
	21st to end	Day	4 12% 5% 13% 7% 6% 6% 5% 6% 7% 28%	5186
February	1st to 10th	Day	6% 16% 6% 14% 8% 7% 6% 5% 6% 7% 19%	1781
	11th to 20th	Day	4 15% 6% 14% 8% 5% 6% 5% 6% 7% 23%	1801
	21st to end	Day	4 15% 6% 16% 10% 7% 6% 4 7% 7% 19%	1593
March	1st to 10th	Day	2 10% 5% 13% 9% 7% 8% 6% 8% 8% 25%	4518
	11th to 20th	Day	2 13% 5% 11% 7% 6% 7% 5% 7% 8% 29%	4868
	21st to end	Day	11% 16% 5% 11% 7% 7% 6% 5% 7% 7% 19%	5830
April	1st to 10th	Day	7% 14% 5% 11% 8% 8% 7% 6% 7% 7% 21%	2400
	11th to 20th	Day	7% 13% 4 11% 7% 5% 6% 4 6% 7% 29%	2372
	21st to end	Day	8% 14% 5% 10% 6% 6% 6% 5% 6% 8% 27%	2757
May	1st to 10th	Day	6% 10% 3 7% 5% 5% 5% 4 5% 7% 42%	6320
	11th to 20th	Day	8% 13% 4 10% 6% 6% 7% 4 7% 8% 27%	6277
	21st to end	Day	12% 13% 3 8% 5% 5% 5% 4 6% 8% 30%	6903
June	1st to 10th	Day	14% 8% 3 9% 6% 6% 6% 5% 5% 7% 32%	2904
	11th to 20th	Day	13% 9% 3 8% 7% 5% 6% 4 6% 7% 31%	3200
	21st to end	Day	10% 7% 3 8% 6% 5% 5% 4 6% 8% 39%	3033
July	1st to 10th	Day	4 3 1 4 3 3 3 3 5% 8% 63%	6780
	11th to 20th	Day	3 3 1 3 3 2 3 2 4 6% 70%	6552
	21st to end	Day	3 3 1 4 3 4 4 3 5% 8% 60%	6874
August	1st to 10th	Day	3 3 1 4 3 4 4 4 5% 7% 62%	4541
	11th to 20th	Day	5% 4 2 6% 5% 5% 6% 4 6% 7% 51%	4349
	21st to end	Day	8% 6% 3 7% 5% 5% 6% 4 5% 7% 44%	4417
September	1st to 10th	Day	8% 5% 2 7% 4 5% 4 3 5% 6% 51%	2400
	11th to 20th	Day	8% 8% 3 8% 5% 5% 4 5% 5% 6% 42%	2400
	21st to end	Day	13% 10% 3 8% 4 4 4 3 6% 8% 37%	2144
October	1st to 10th	Day	10% 11% 3 8% 5% 5% 5% 5% 6% 7% 35%	3280
	11th to 20th	Day	15% 11% 4 9% 5% 5% 5% 4 6% 6% 30%	3234
	21st to end	Day	9% 14% 5% 12% 7% 6% 6% 4 6% 8% 24%	3200
November	1st to 10th	Day	9% 17% 6% 12% 7% 6% 6% 4 4 6% 22%	1713
	11th to 20th	Day	7% 17% 5% 11% 8% 7% 6% 6% 5% 6% 22%	1680
	21st to end	Day	8% 14% 5% 11% 8% 7% 6% 5% 7% 8% 22%	1680
December	1st to 10th	Day	5% 11% 5% 13% 7% 8% 6% 5% 7% 8% 25%	2401
	11th to 20th	Day	6% 15% 6% 14% 9% 8% 10% 5% 7% 6% 14%	2641
	21st to end	Day	6% 18% 6% 15% 9% 8% 7% 5% 7% 6% 13%	3552
January	1st to 10th	Night	7% 18% 7% 15% 9% 9% 8% 6% 7% 5% 9%	8770
	11th to 20th	Night	6% 8% 4 9% 7% 6% 6% 5% 7% 7% 36%	8226
	21st to end	Night	4 11% 5% 12% 8% 6% 7% 5% 6% 7% 29%	8994
February	1st to 10th	Night	6% 17% 6% 14% 7% 7% 6% 5% 6% 7% 19%	2835
	11th to 20th	Night	4 16% 6% 12% 7% 6% 6% 4 5% 6% 28%	2597
	21st to end	Night	6% 13% 6% 15% 8% 5% 6% 5% 6% 8% 22%	2036
March	1st to 10th	Night	2 9% 5% 11% 7% 6% 7% 6% 9% 11% 29%	5376
	11th to 20th	Night	2 13% 5% 11% 6% 6% 6% 6% 7% 9% 31%	5114
	21st to end	Night	10% 16% 5% 11% 7% 6% 6% 5% 7% 6% 21%	5144
April	1st to 10th	Night	4 13% 5% 9% 8% 6% 7% 6% 6% 8% 29%	2000
	11th to 20th	Night	5% 10% 4 10% 6% 7% 6% 5% 7% 7% 32%	1979
	21st to end	Night	8% 12% 3 8% 7% 6% 6% 5% 6% 8% 32%	1639
May	1st to 10th	Night	5% 9% 3 8% 5% 5% 4 4 6% 6% 44%	3640
	11th to 20th	Night	9% 15% 4 9% 5% 4 5% 4 5% 7% 33%	3616
	21st to end	Night	8% 14% 3 7% 5% 5% 5% 4 7% 8% 35%	3972
June	1st to 10th	Night	8% 9% 3 7% 7% 5% 6% 5% 7% 9% 36%	1481
	11th to 20th	Night	8% 9% 2 6% 7% 5% 6% 4 6% 9% 38%	1200
	21st to end	Night	6% 6% 2 7% 5% 4 4 4 7% 9% 47%	1355
July	1st to 10th	Night	3 4 1 3 3 3 4 3 5% 6% 66%	3180
	11th to 20th	Night	1 1 1 2 2 2 3 3 5% 7% 73%	3405
	21st to end	Night	4 4 2 4 2 3 3 4 5% 6% 65%	3969
August	1st to 10th	Night	2 2 1 3 3 3 4 4 6% 9% 64%	2609
	11th to 20th	Night	2 3 2 4 3 4 4 3 6% 10% 57%	2699
	21st to end	Night	13% 6% 2 6% 4 3 4 3 5% 7% 46%	3499
September	1st to 10th	Night	5% 4 2 4 3 4 4 4 6% 8% 56%	2000
	11th to 20th	Night	8% 7% 2 5% 4 3 5% 4 6% 7% 50%	2000
	21st to end	Night	10% 8% 3 7% 4 5% 4 4 6% 8% 40%	2255
October	1st to 10th	Night	9% 11% 3 8% 5% 5% 5% 4 6% 8% 36%	3920
	11th to 20th	Night	16% 11% 3 8% 5% 4 5% 4 6% 7% 32%	3922
	21st to end	Night	10% 16% 4 9% 5% 5% 5% 5% 5% 6% 29%	4600
November	1st to 10th	Night	10% 15% 5% 11% 7% 7% 6% 5% 6% 7% 23%	2800
	11th to 20th	Night	7% 15% 4 12% 7% 7% 7% 5% 6% 7% 23%	2940
	21st to end	Night	6% 15% 5% 13% 8% 6% 6% 5% 8% 8% 19%	2940
December	1st to 10th	Night	5% 11% 4 9% 7% 6% 5% 5% 7% 9% 31%	4960
	11th to 20th	Night	5% 16% 6% 15% 8% 7% 7% 5% 6% 7% 16%	5765
	21st to end	Night	6% 17% 6% 14% 9% 8% 8% 6% 8% 6% 14%	7688

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	63% 12% 13% 10% 2	4125
	11th to 20th	Day	44% 9% 18% 20% 6% 3	4679
	21st to end	Day	51% 10% 14% 18% 8%	5187
February	1st to 10th	Day	61% 10% 11% 9% 8% 1	1781
	11th to 20th	Day	57% 10% 14% 12% 7% 1	1810
	21st to end	Day	62% 8% 13% 13% 3	1593
March	1st to 10th	Day	49% 12% 13% 14% 12% 1	4518
	11th to 20th	Day	46% 10% 16% 21% 6%	4868
	21st to end	Day	59% 10% 13% 10% 7%	5830
April	1st to 10th	Day	60% 10% 15% 14% 2	2400
	11th to 20th	Day	52% 9% 13% 15% 10% 1	2372
	21st to end	Day	53% 9% 16% 14% 7%	2757
May	1st to 10th	Day	38% 6% 14% 30% 12% 1	6320
	11th to 20th	Day	50% 8% 20% 18% 3	6280
	21st to end	Day	48% 9% 18% 20% 4	6904
June	1st to 10th	Day	50% 8% 14% 16% 8% 3	2904
	11th to 20th	Day	51% 8% 15% 18% 7%	3200
	21st to end	Day	41% 8% 17% 21% 11% 1	3033
July	1st to 10th	Day	21% 5% 15% 24% 21% 15%	6706
	11th to 20th	Day	16% 5% 15% 26% 27% 11%	6471
	21st to end	Day	20% 6% 18% 31% 19% 5%	6681
August	1st to 10th	Day	19% 6% 12% 25% 29% 8%	4524
	11th to 20th	Day	29% 9% 23% 26% 11% 3	4391
	21st to end	Day	37% 9% 15% 24% 14% 2	4416
September	1st to 10th	Day	33% 6% 13% 27% 17% 4	2400
	11th to 20th	Day	41% 7% 11% 22% 17% 3	2400
	21st to end	Day	45% 8% 17% 18% 10% 3	2144
October	1st to 10th	Day	45% 9% 17% 23% 6%	3280
	11th to 20th	Day	53% 7% 11% 22% 7% 1	3234
	21st to end	Day	54% 11% 15% 15% 5%	3200
November	1st to 10th	Day	63% 8% 14% 12% 4	1713
	11th to 20th	Day	60% 10% 13% 12% 6% 1	1680
	21st to end	Day	56% 12% 12% 14% 5% 1	1680
December	1st to 10th	Day	52% 10% 20% 12% 5%	2401
	11th to 20th	Day	61% 13% 13% 9% 3	2643
	21st to end	Day	63% 13% 13% 9% 1	3552
January	1st to 10th	Night	65% 14% 13% 7% 2	8770
	11th to 20th	Night	42% 10% 18% 21% 7% 2	8264
	21st to end	Night	48% 12% 15% 17% 8%	8994
February	1st to 10th	Night	61% 11% 11% 12% 5% 1	2835
	11th to 20th	Night	56% 8% 13% 15% 7% 1	2599
	21st to end	Night	57% 9% 12% 16% 5%	2036
March	1st to 10th	Night	40% 11% 17% 19% 12% 1	5376
	11th to 20th	Night	44% 10% 19% 22% 4	5115
	21st to end	Night	58% 10% 13% 14% 4	5144
April	1st to 10th	Night	49% 11% 20% 16% 3	2000
	11th to 20th	Night	45% 10% 19% 17% 8% 1	1979
	21st to end	Night	48% 9% 18% 17% 8%	1639
May	1st to 10th	Night	38% 7% 18% 27% 11%	3637
	11th to 20th	Night	49% 9% 20% 18% 5%	3616
	21st to end	Night	44% 12% 19% 20% 4	3972
June	1st to 10th	Night	44% 9% 18% 19% 8% 3	1481
	11th to 20th	Night	42% 11% 18% 20% 9%	1200
	21st to end	Night	32% 9% 25% 23% 9% 1	1355
July	1st to 10th	Night	19% 6% 15% 24% 22% 13%	3145
	11th to 20th	Night	11% 5% 21% 27% 27% 10%	3363
	21st to end	Night	19% 6% 16% 35% 16% 8%	3857
August	1st to 10th	Night	16% 6% 15% 30% 30% 4	2601
	11th to 20th	Night	21% 9% 30% 26% 11% 3	2723
	21st to end	Night	36% 8% 18% 24% 12% 3	3499
September	1st to 10th	Night	25% 8% 18% 28% 18% 3	2000
	11th to 20th	Night	32% 7% 15% 24% 17% 4	2000
	21st to end	Night	40% 9% 18% 21% 8% 2	2255
October	1st to 10th	Night	42% 9% 19% 23% 6%	3920
	11th to 20th	Night	49% 9% 13% 22% 7%	3922
	21st to end	Night	51% 9% 16% 19% 4	4600
November	1st to 10th	Night	58% 11% 14% 12% 5%	2800
	11th to 20th	Night	55% 13% 14% 12% 4 1	2940
	21st to end	Night	57% 13% 13% 10% 5% 1	2940
December	1st to 10th	Night	46% 11% 20% 18% 5% 1	4960
	11th to 20th	Night	61% 12% 13% 11% 2	5762
	21st to end	Night	60% 13% 12% 13% 2	7688

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	14% 17% 29% 24% 14% 4	220
	11th to 20th	Day	11% 10% 24% 35% 15% 5%	220
	21st to end	Day	10% 13% 28% 33% 15% 1	242
February	1st to 10th	Day	21% 20% 29% 20% 9% 2	321
	11th to 20th	Day	18% 19% 30% 23% 6% 3	411
	21st to end	Day	19% 21% 34% 17% 9% 1	387
March	1st to 10th	Day	19% 20% 28% 21% 9% 2	500
	11th to 20th	Day	19% 22% 25% 19% 11% 4	500
	21st to end	Day	24% 23% 26% 16% 8% 3	550
April	1st to 10th	Day	24% 21% 31% 15% 8% 1	500
	11th to 20th	Day	21% 22% 29% 18% 8% 3	492
	21st to end	Day	21% 23% 25% 19% 8% 4	500
May	1st to 10th	Day	17% 20% 31% 20% 9% 3	503
	11th to 20th	Day	20% 16% 28% 21% 12% 3	528
	21st to end	Day	22% 16% 28% 22% 10% 3	573
June	1st to 10th	Day	18% 21% 33% 18% 9% 1	634
	11th to 20th	Day	19% 20% 32% 18% 10% 2	930
	21st to end	Day	14% 17% 31% 22% 13% 3	763
July	1st to 10th	Day	11% 14% 36% 25% 13% 2	721
	11th to 20th	Day	10% 14% 34% 26% 12% 4	620
	21st to end	Day	6% 13% 31% 27% 16% 7%	575
August	1st to 10th	Day	7% 11% 27% 30% 17% 8%	527
	11th to 20th	Day	8% 12% 27% 29% 16% 7%	517
	21st to end	Day	11% 16% 30% 21% 15% 7%	583
September	1st to 10th	Day	13% 13% 26% 23% 16% 8%	530
	11th to 20th	Day	14% 14% 25% 27% 17% 3	530
	21st to end	Day	21% 18% 25% 20% 12% 3	530
October	1st to 10th	Day	20% 15% 26% 19% 15% 5%	530
	11th to 20th	Day	24% 19% 18% 21% 13% 4	515
	21st to end	Day	22% 18% 26% 25% 8% 2	363
November	1st to 10th	Day	22% 16% 30% 25% 7% 1	256
	11th to 20th	Day	25% 17% 26% 17% 13% 2	220
	21st to end	Day	18% 11% 28% 24% 13% 6%	220
December	1st to 10th	Day	18% 15% 16% 26% 17% 8%	220
	11th to 20th	Day	20% 14% 29% 25% 10% 3	220
	21st to end	Day	15% 9% 31% 34% 10% 1	242
January	1st to 10th	Night	19% 14% 29% 27% 9% 2	950
	11th to 20th	Night	12% 10% 34% 30% 13% 1	848
	21st to end	Night	12% 12% 31% 32% 11% 2	924
February	1st to 10th	Night	17% 15% 27% 30% 9% 2	840
	11th to 20th	Night	13% 13% 27% 34% 13% 1	804
	21st to end	Night	15% 14% 27% 28% 15% 1	660
March	1st to 10th	Night	13% 12% 29% 29% 17% 2	800
	11th to 20th	Night	14% 12% 32% 28% 12% 2	800
	21st to end	Night	16% 14% 28% 27% 13% 2	880
April	1st to 10th	Night	14% 14% 24% 33% 14% 2	800
	11th to 20th	Night	13% 15% 29% 27% 15% 1	791
	21st to end	Night	15% 13% 23% 34% 12% 2	439
May	1st to 10th	Night	10% 12% 27% 33% 16% 2	400
	11th to 20th	Night	10% 7% 23% 37% 23% 2	394
	21st to end	Night	14% 8% 23% 33% 20% 1	433
June	1st to 10th	Night	11% 11% 26% 39% 12% 1	400
	11th to 20th	Night	12% 12% 30% 29% 16% 1	400
	21st to end	Night	8% 10% 26% 32% 23% 2	400
July	1st to 10th	Night	7% 7% 21% 40% 23% 2	390
	11th to 20th	Night	5% 8% 24% 41% 21% 1	388
	21st to end	Night	3 5% 22% 40% 29% 1	438
August	1st to 10th	Night	5% 4 17% 40% 32% 2	398
	11th to 20th	Night	4 3 18% 39% 33% 3	466
	21st to end	Night	10% 8% 21% 36% 23% 2	810
September	1st to 10th	Night	8% 6% 23% 33% 25% 5%	800
	11th to 20th	Night	12% 6% 20% 26% 28% 8%	800
	21st to end	Night	16% 9% 24% 31% 17% 3	800
October	1st to 10th	Night	13% 10% 22% 33% 20% 3	800
	11th to 20th	Night	19% 10% 24% 29% 17% 2	800
	21st to end	Night	20% 15% 24% 27% 12% 2	880
November	1st to 10th	Night	20% 12% 31% 28% 8%	820
	11th to 20th	Night	21% 15% 28% 24% 10% 2	840
	21st to end	Night	17% 15% 28% 26% 12% 3	840
December	1st to 10th	Night	14% 11% 28% 32% 13% 2	996
	11th to 20th	Night	18% 12% 31% 30% 9% 1	1064
	21st to end	Night	15% 13% 31% 33% 7%	1071

Page generated at 2026-02-12 22:42:12. Version ac07

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