Salmon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Salmon clear sky chart from 2005-11-06 to 2026-02-01.

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	3 5% 2 6% 5% 5% 6% 5% 7% 9% 47%	135843
	Night	3 6% 3 7% 5% 5% 6% 5% 7% 9% 44%	133494
Transparency	Day	32% 7% 16% 23% 16% 6%	130549
	Night	32% 8% 20% 24% 12% 3	129804
Seeing	Day	8% 14% 31% 29% 14% 3	16592
	Night	7% 6% 29% 40% 16% 2	26142

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 6% 3 11% 9% 9% 9% 8% 11% 12% 22%	3696
	11th to 20th	Day	1 4 2 8% 8% 7% 10% 5% 7% 9% 40%	3720
	21st to end	Day	1 5% 3 8% 6% 6% 5% 5% 7% 10% 43%	4092
February	1st to 10th	Day	2 10% 4 12% 7% 5% 8% 8% 10% 10% 26%	1800
	11th to 20th	Day	1 8% 4 9% 8% 6% 8% 7% 9% 10% 30%	1839
	21st to end	Day	1 10% 3 12% 7% 8% 7% 6% 8% 9% 29%	1650
March	1st to 10th	Day	1 6% 3 8% 5% 6% 7% 6% 9% 10% 39%	4549
	11th to 20th	Day	2 9% 4 8% 6% 6% 7% 6% 7% 8% 37%	5000
	21st to end	Day	2 9% 4 12% 8% 7% 7% 7% 8% 9% 26%	5486
April	1st to 10th	Day	4 10% 4 9% 9% 7% 7% 5% 8% 9% 29%	2374
	11th to 20th	Day	4 10% 3 8% 7% 7% 6% 5% 7% 7% 36%	2547
	21st to end	Day	6% 10% 4 9% 6% 6% 6% 4 7% 8% 34%	2600
May	1st to 10th	Day	8% 8% 3 7% 5% 4 5% 4 6% 8% 42%	5880
	11th to 20th	Day	5% 7% 3 7% 5% 6% 6% 5% 8% 11% 37%	5841
	21st to end	Day	6% 7% 2 7% 5% 5% 5% 4 6% 7% 45%	7210
June	1st to 10th	Day	9% 7% 3 7% 6% 6% 6% 5% 7% 8% 35%	3000
	11th to 20th	Day	9% 6% 2 6% 5% 5% 5% 4 7% 8% 42%	3000
	21st to end	Day	3 2 2 4 4 5% 6% 4 6% 8% 56%	3000
July	1st to 10th	Day	2 2 1 3 3 4 4 4 5% 6% 66%	6604
	11th to 20th	Day	1 1 2 2 3 4 3 6% 8% 70%	6320
	21st to end	Day	2 2 1 3 3 5% 5% 5% 7% 8% 59%	6880
August	1st to 10th	Day	2 2 1 4 4 5% 6% 5% 8% 9% 53%	5788
	11th to 20th	Day	1 1 1 2 3 3 5% 3 6% 7% 68%	5798
	21st to end	Day	4 3 2 4 3 3 4 3 5% 6% 62%	6438
September	1st to 10th	Day	3 2 1 3 4 3 4 3 4 8% 64%	2329
	11th to 20th	Day	4 4 2 5% 4 5% 5% 4 6% 7% 53%	2200
	21st to end	Day	7% 4 2 4 3 3 4 3 4 6% 61%	2200
October	1st to 10th	Day	4 5% 2 4 3 3 3 4 4 6% 63%	3535
	11th to 20th	Day	3 6% 2 4 3 3 4 3 6% 10% 56%	3193
	21st to end	Day	2 5% 2 6% 4 5% 6% 5% 7% 10% 50%	3200
November	1st to 10th	Day	5% 7% 2 6% 5% 6% 6% 5% 7% 10% 41%	1854
	11th to 20th	Day	3 9% 2 7% 6% 5% 6% 6% 8% 11% 37%	1822
	21st to end	Day	1 7% 4 7% 6% 6% 7% 5% 9% 9% 40%	1680
December	1st to 10th	Day	1 4 2 5% 5% 6% 6% 5% 7% 10% 49%	2428
	11th to 20th	Day	2 5% 3 10% 7% 6% 8% 7% 9% 11% 31%	2715
	21st to end	Day	3 8% 2 10% 8% 7% 7% 6% 10% 11% 28%	3575
January	1st to 10th	Night	1 7% 4 11% 8% 9% 11% 7% 9% 10% 22%	6512
	11th to 20th	Night	1 7% 3 13% 8% 8% 7% 6% 9% 9% 31%	6460
	21st to end	Night	1 7% 3 10% 8% 7% 6% 5% 7% 8% 37%	7092
February	1st to 10th	Night	2 12% 4 10% 8% 7% 9% 7% 9% 11% 21%	2600
	11th to 20th	Night	2 10% 5% 9% 8% 6% 8% 6% 9% 9% 29%	2447
	21st to end	Night	1 8% 4 11% 7% 8% 7% 6% 9% 8% 30%	1980
March	1st to 10th	Night	1 7% 4 10% 6% 5% 6% 5% 8% 9% 39%	5344
	11th to 20th	Night	2 7% 4 10% 5% 6% 7% 6% 7% 10% 37%	5000
	21st to end	Night	2 9% 4 10% 7% 6% 7% 5% 9% 10% 30%	5489
April	1st to 10th	Night	3 10% 3 6% 7% 5% 7% 4 8% 10% 37%	2024
	11th to 20th	Night	4 9% 3 8% 6% 6% 5% 6% 7% 8% 39%	1800
	21st to end	Night	6% 7% 3 8% 6% 6% 7% 4 7% 8% 39%	1800
May	1st to 10th	Night	9% 9% 3 6% 4 3 4 3 5% 6% 49%	4100
	11th to 20th	Night	8% 7% 3 6% 4 4 4 4 6% 10% 44%	4074
	21st to end	Night	7% 9% 2 7% 4 5% 5% 4 5% 7% 45%	3658
June	1st to 10th	Night	8% 6% 2 7% 5% 5% 6% 4 5% 8% 45%	1400
	11th to 20th	Night	11% 5% 2 5% 4 3 4 4 6% 7% 47%	1400
	21st to end	Night	3 3 1 4 3 4 4 4 6% 7% 61%	1400
July	1st to 10th	Night	1 1 1 2 2 2 3 3 5% 7% 74%	3351
	11th to 20th	Night	1 1 2 1 2 2 2 4 6% 77%	3640
	21st to end	Night	1 1 1 2 3 4 6% 5% 7% 9% 61%	3970
August	1st to 10th	Night	1 2 1 4 3 4 5% 3 7% 10% 61%	4023
	11th to 20th	Night	1 1 1 1 2 3 3 5% 7% 75%	4051
	21st to end	Night	5% 3 1 4 3 3 3 3 4 5% 64%	4525
September	1st to 10th	Night	4 3 1 3 3 3 3 3 4 6% 66%	2070
	11th to 20th	Night	6% 4 2 6% 4 3 4 4 5% 7% 55%	2200
	21st to end	Night	6% 5% 2 4 3 3 3 2 4 6% 62%	2200
October	1st to 10th	Night	4 5% 1 4 3 3 3 2 4 6% 66%	3662
	11th to 20th	Night	6% 5% 2 5% 3 3 4 3 5% 7% 57%	3953
	21st to end	Night	5% 6% 2 6% 4 4 5% 3 6% 8% 50%	4600
November	1st to 10th	Night	6% 8% 3 6% 5% 5% 5% 5% 8% 9% 40%	2665
	11th to 20th	Night	4 9% 2 8% 6% 6% 7% 6% 7% 10% 34%	2776
	21st to end	Night	3 6% 2 7% 6% 6% 7% 5% 9% 10% 39%	2940
December	1st to 10th	Night	2 6% 2 5% 5% 5% 5% 5% 7% 9% 49%	4969
	11th to 20th	Night	2 8% 3 9% 6% 6% 9% 6% 9% 11% 31%	5696
	21st to end	Night	2 8% 4 12% 8% 9% 9% 7% 9% 10% 21%	7623

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	41% 12% 27% 17% 3	3696
	11th to 20th	Day	35% 9% 26% 20% 9% 1	3720
	21st to end	Day	32% 8% 22% 27% 11%	4092
February	1st to 10th	Day	48% 11% 19% 17% 5%	1800
	11th to 20th	Day	46% 10% 21% 16% 7%	1848
	21st to end	Day	50% 9% 14% 20% 7% 1	1650
March	1st to 10th	Day	35% 8% 16% 25% 15% 2	4549
	11th to 20th	Day	37% 7% 19% 30% 6%	5000
	21st to end	Day	50% 8% 22% 17% 4	5486
April	1st to 10th	Day	50% 9% 16% 18% 7% 1	2374
	11th to 20th	Day	46% 7% 15% 20% 10% 1	2550
	21st to end	Day	48% 7% 13% 24% 7% 1	2600
May	1st to 10th	Day	38% 7% 13% 24% 16% 2	5880
	11th to 20th	Day	37% 8% 14% 25% 13% 3	5844
	21st to end	Day	35% 8% 14% 28% 13% 3	7212
June	1st to 10th	Day	44% 9% 16% 22% 8% 1	3000
	11th to 20th	Day	38% 8% 12% 22% 15% 6%	3000
	21st to end	Day	26% 6% 9% 25% 27% 7%	3000
July	1st to 10th	Day	17% 5% 9% 18% 27% 25%	6534
	11th to 20th	Day	11% 5% 6% 16% 32% 30%	6245
	21st to end	Day	18% 5% 11% 22% 25% 18%	6681
August	1st to 10th	Day	26% 6% 9% 23% 23% 13%	4216
	11th to 20th	Day	17% 5% 9% 30% 32% 7%	4197
	21st to end	Day	17% 5% 7% 26% 31% 14%	4645
September	1st to 10th	Day	19% 5% 9% 25% 28% 14%	2329
	11th to 20th	Day	28% 6% 13% 24% 23% 6%	2200
	21st to end	Day	25% 4 14% 31% 23% 3	2200
October	1st to 10th	Day	24% 3 12% 29% 28% 4	3535
	11th to 20th	Day	24% 6% 23% 29% 17% 1	3193
	21st to end	Day	30% 6% 19% 29% 15% 1	3200
November	1st to 10th	Day	38% 9% 19% 24% 8% 2	1854
	11th to 20th	Day	39% 10% 26% 19% 5% 1	1822
	21st to end	Day	38% 8% 24% 21% 8% 1	1680
December	1st to 10th	Day	28% 10% 31% 27% 5%	2428
	11th to 20th	Day	40% 9% 32% 16% 3	2714
	21st to end	Day	39% 9% 25% 19% 7% 1	3575
January	1st to 10th	Night	40% 15% 23% 20% 2	6512
	11th to 20th	Night	40% 12% 24% 17% 6% 1	6460
	21st to end	Night	34% 10% 24% 23% 10%	7092
February	1st to 10th	Night	52% 9% 19% 15% 5%	2600
	11th to 20th	Night	47% 8% 21% 17% 7%	2448
	21st to end	Night	45% 9% 17% 19% 8% 1	1980
March	1st to 10th	Night	32% 10% 20% 23% 14% 1	5344
	11th to 20th	Night	34% 9% 26% 26% 6%	5000
	21st to end	Night	41% 12% 25% 19% 3	5489
April	1st to 10th	Night	41% 9% 19% 24% 6% 1	2024
	11th to 20th	Night	40% 8% 18% 24% 10%	1800
	21st to end	Night	41% 9% 20% 23% 7%	1800
May	1st to 10th	Night	36% 6% 14% 34% 11%	4097
	11th to 20th	Night	34% 8% 15% 28% 14% 2	4075
	21st to end	Night	35% 9% 18% 30% 8%	3658
June	1st to 10th	Night	35% 9% 18% 26% 11% 1	1400
	11th to 20th	Night	35% 7% 15% 25% 14% 5%	1400
	21st to end	Night	19% 6% 15% 28% 25% 7%	1400
July	1st to 10th	Night	10% 4 13% 25% 27% 21%	3313
	11th to 20th	Night	9% 3 5% 24% 36% 23%	3592
	21st to end	Night	17% 5% 18% 23% 23% 14%	3857
August	1st to 10th	Night	18% 5% 11% 33% 23% 10%	2919
	11th to 20th	Night	10% 4 14% 38% 26% 8%	2928
	21st to end	Night	17% 5% 8% 30% 30% 10%	3261
September	1st to 10th	Night	18% 4 10% 29% 24% 14%	2070
	11th to 20th	Night	27% 6% 14% 23% 24% 6%	2200
	21st to end	Night	24% 3 13% 30% 25% 4	2200
October	1st to 10th	Night	20% 4 13% 31% 30% 2	3662
	11th to 20th	Night	28% 5% 21% 33% 13% 1	3953
	21st to end	Night	32% 6% 22% 27% 14%	4600
November	1st to 10th	Night	37% 8% 20% 25% 8% 2	2665
	11th to 20th	Night	41% 10% 23% 21% 4 1	2776
	21st to end	Night	36% 8% 24% 23% 9% 1	2940
December	1st to 10th	Night	27% 10% 35% 23% 5%	4969
	11th to 20th	Night	38% 11% 33% 15% 2	5697
	21st to end	Night	44% 10% 24% 15% 7% 1	7623

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	4 11% 39% 29% 16% 1	220
	11th to 20th	Day	4 6% 34% 37% 14% 5%	220
	21st to end	Day	5% 8% 33% 38% 12% 4	242
February	1st to 10th	Day	13% 14% 44% 26% 4	300
	11th to 20th	Day	5% 16% 40% 30% 9% 1	384
	21st to end	Day	9% 20% 36% 27% 7%	414
March	1st to 10th	Day	8% 20% 39% 26% 5% 1	500
	11th to 20th	Day	10% 21% 30% 28% 10% 1	500
	21st to end	Day	10% 25% 35% 21% 7% 1	550
April	1st to 10th	Day	13% 21% 33% 22% 8% 2	500
	11th to 20th	Day	12% 26% 31% 22% 7% 2	492
	21st to end	Day	14% 22% 30% 23% 8% 2	500
May	1st to 10th	Day	12% 21% 26% 27% 13% 2	503
	11th to 20th	Day	16% 17% 29% 25% 11% 2	528
	21st to end	Day	11% 15% 24% 25% 20% 5%	702
June	1st to 10th	Day	10% 12% 25% 31% 18% 4	730
	11th to 20th	Day	14% 16% 28% 29% 12% 1	730
	21st to end	Day	4 11% 24% 35% 23% 2	730
July	1st to 10th	Day	3 9% 29% 34% 20% 4	653
	11th to 20th	Day	3 9% 38% 32% 15% 3	524
	21st to end	Day	3 10% 30% 35% 17% 5%	575
August	1st to 10th	Day	5% 8% 32% 34% 16% 5%	527
	11th to 20th	Day	3 7% 28% 36% 18% 7%	517
	21st to end	Day	6% 9% 28% 31% 20% 6%	583
September	1st to 10th	Day	4 9% 24% 31% 23% 9%	530
	11th to 20th	Day	8% 10% 24% 31% 21% 6%	530
	21st to end	Day	10% 9% 26% 30% 21% 5%	530
October	1st to 10th	Day	10% 11% 28% 28% 18% 5%	491
	11th to 20th	Day	8% 10% 28% 28% 16% 9%	330
	21st to end	Day	6% 13% 33% 32% 13% 3	363
November	1st to 10th	Day	9% 9% 38% 27% 15% 2	330
	11th to 20th	Day	5% 12% 39% 32% 10% 2	330
	21st to end	Day	4 8% 35% 41% 12% 1	330
December	1st to 10th	Day	5% 9% 36% 27% 17% 6%	242
	11th to 20th	Day	10% 10% 41% 28% 10% 1	220
	21st to end	Day	7% 8% 43% 28% 14% 1	242
January	1st to 10th	Night	6% 6% 37% 41% 9%	867
	11th to 20th	Night	5% 6% 40% 37% 11% 1	840
	21st to end	Night	5% 6% 36% 43% 10% 1	924
February	1st to 10th	Night	8% 7% 43% 35% 6% 1	800
	11th to 20th	Night	6% 9% 39% 38% 8% 1	784
	21st to end	Night	4 10% 37% 37% 10% 1	660
March	1st to 10th	Night	4 6% 40% 40% 9% 1	800
	11th to 20th	Night	6% 9% 33% 40% 12% 1	800
	21st to end	Night	7% 10% 32% 41% 9% 1	880
April	1st to 10th	Night	7% 8% 30% 40% 15% 1	800
	11th to 20th	Night	7% 10% 35% 38% 9%	612
	21st to end	Night	9% 9% 29% 38% 14% 1	600
May	1st to 10th	Night	11% 10% 23% 40% 16% 1	600
	11th to 20th	Night	10% 9% 22% 36% 22% 1	591
	21st to end	Night	14% 5% 20% 34% 25% 2	433
June	1st to 10th	Night	12% 4 19% 42% 23% 2	400
	11th to 20th	Night	15% 3 22% 42% 18% 1	400
	21st to end	Night	4 2 18% 49% 27% 1	400
July	1st to 10th	Night	2 1 11% 51% 33% 2	390
	11th to 20th	Night	1 2 13% 57% 27%	388
	21st to end	Night	2 1 10% 52% 34% 1	438
August	1st to 10th	Night	4 2 15% 48% 29% 2	587
	11th to 20th	Night	2 2 12% 51% 30% 3	594
	21st to end	Night	6% 4 17% 42% 30% 1	663
September	1st to 10th	Night	6% 1 15% 41% 33% 4	800
	11th to 20th	Night	7% 3 11% 42% 32% 5%	800
	21st to end	Night	8% 3 19% 38% 28% 5%	800
October	1st to 10th	Night	9% 7% 22% 40% 20% 3	800
	11th to 20th	Night	10% 6% 22% 42% 17% 4	800
	21st to end	Night	9% 7% 28% 41% 12% 3	880
November	1st to 10th	Night	8% 7% 30% 43% 12% 1	820
	11th to 20th	Night	8% 9% 36% 37% 9% 1	886
	21st to end	Night	4 7% 34% 41% 12% 1	1050
December	1st to 10th	Night	7% 6% 38% 38% 10% 2	1050
	11th to 20th	Night	7% 7% 38% 38% 8% 1	1050
	21st to end	Night	7% 8% 43% 32% 10% 1	1155

Page generated at 2026-01-28 23:21:40. Version ac07

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