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 2024-01-14.

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	4 6% 3 6% 6% 4 6% 6% 7% 9% 41%	74606
	Night	4 7% 3 7% 7% 4 6% 6% 7% 9% 39%	75153
Transparency	Day	38% 8% 15% 21% 13% 5%	74307
	Night	38% 8% 18% 22% 11% 3	74974
Seeing	Day	9% 15% 31% 29% 14% 3	13927
	Night	7% 6% 28% 40% 17% 2	23489

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	2 8% 3 9% 9% 5% 9% 8% 9% 12% 26%	1509
	11th to 20th	Day	1 5% 3 8% 9% 5% 10% 8% 8% 9% 36%	1464
	21st to end	Day	2 8% 5% 7% 9% 5% 8% 9% 7% 10% 32%	1584
February	1st to 10th	Day	2 8% 4 10% 7% 4 7% 10% 9% 10% 28%	1620
	11th to 20th	Day	2 7% 5% 8% 9% 4 8% 8% 9% 10% 31%	1650
	21st to end	Day	1 7% 6% 10% 9% 6% 8% 8% 8% 10% 28%	1480
March	1st to 10th	Day	3 5% 4 8% 7% 5% 8% 9% 9% 11% 32%	1805
	11th to 20th	Day	4 8% 4 8% 7% 4 7% 8% 8% 10% 32%	1980
	21st to end	Day	4 9% 5% 9% 9% 5% 9% 8% 6% 9% 27%	2178
April	1st to 10th	Day	4 9% 5% 9% 9% 5% 7% 7% 7% 9% 28%	2136
	11th to 20th	Day	5% 10% 4 7% 8% 5% 7% 6% 6% 7% 35%	2289
	21st to end	Day	7% 10% 4 9% 7% 4 6% 5% 6% 8% 33%	2340
May	1st to 10th	Day	5% 8% 3 7% 7% 4 7% 7% 7% 9% 36%	2340
	11th to 20th	Day	8% 7% 4 7% 7% 5% 7% 6% 7% 8% 34%	2301
	21st to end	Day	11% 10% 4 10% 8% 4 6% 7% 7% 8% 26%	2835
June	1st to 10th	Day	9% 7% 3 7% 7% 5% 7% 7% 7% 9% 33%	2700
	11th to 20th	Day	10% 6% 2 6% 6% 4 7% 5% 6% 8% 40%	2700
	21st to end	Day	3 2 2 4 5% 4 6% 5% 6% 8% 55%	2700
July	1st to 10th	Day	2 2 2 3 4 3 5% 7% 7% 9% 54%	2637
	11th to 20th	Day	3 2 3 4 3 4 5% 6% 7% 64%	2520
	21st to end	Day	4 3 1 3 4 4 5% 5% 5% 8% 58%	2741
August	1st to 10th	Day	5% 4 2 5% 5% 3 5% 5% 7% 8% 51%	2337
	11th to 20th	Day	3 3 1 2 4 3 4 4 6% 8% 63%	2299
	21st to end	Day	4 3 2 4 4 2 4 4 6% 8% 60%	2570
September	1st to 10th	Day	4 2 1 3 4 2 5% 4 3 7% 64%	2097
	11th to 20th	Day	5% 4 2 4 5% 4 4 5% 6% 7% 54%	1980
	21st to end	Day	7% 5% 2 4 3 2 4 4 5% 6% 58%	1980
October	1st to 10th	Day	7% 8% 3 7% 5% 3 5% 6% 6% 7% 44%	1945
	11th to 20th	Day	5% 7% 3 5% 5% 4 5% 6% 6% 9% 47%	1769
	21st to end	Day	3 6% 2 6% 5% 4 7% 7% 7% 11% 41%	1782
November	1st to 10th	Day	5% 7% 3 5% 6% 5% 6% 6% 7% 10% 39%	1674
	11th to 20th	Day	3 8% 3 7% 7% 4 6% 7% 7% 10% 38%	1649
	21st to end	Day	2 6% 5% 7% 7% 5% 7% 6% 9% 9% 39%	1520
December	1st to 10th	Day	2 5% 4 6% 8% 5% 9% 9% 8% 11% 33%	1368
	11th to 20th	Day	2 6% 3 9% 9% 5% 7% 9% 10% 11% 28%	1685
	21st to end	Day	2 7% 3 11% 11% 6% 7% 8% 9% 10% 27%	2442
January	1st to 10th	Night	3 9% 4 8% 8% 6% 10% 9% 10% 11% 22%	2671
	11th to 20th	Night	2 8% 4 8% 9% 6% 9% 8% 7% 9% 30%	2574
	21st to end	Night	2 8% 4 9% 9% 5% 8% 7% 8% 10% 29%	2771
February	1st to 10th	Night	2 10% 4 9% 9% 5% 9% 9% 9% 12% 23%	2340
	11th to 20th	Night	2 10% 5% 7% 9% 4 8% 8% 9% 10% 30%	2196
	21st to end	Night	1 6% 6% 10% 8% 6% 8% 8% 9% 9% 30%	1776
March	1st to 10th	Night	2 8% 4 9% 9% 4 7% 7% 8% 10% 32%	2154
	11th to 20th	Night	3 7% 3 6% 6% 4 6% 8% 8% 11% 39%	1980
	21st to end	Night	3 10% 6% 7% 8% 4 6% 7% 8% 10% 30%	2178
April	1st to 10th	Night	4 9% 4 6% 7% 4 7% 5% 7% 10% 36%	1822
	11th to 20th	Night	5% 7% 4 7% 6% 4 6% 8% 7% 8% 38%	1619
	21st to end	Night	6% 7% 4 7% 7% 4 7% 5% 7% 8% 39%	1620
May	1st to 10th	Night	6% 8% 3 7% 5% 2 5% 6% 7% 8% 43%	1620
	11th to 20th	Night	8% 7% 4 6% 6% 4 6% 6% 7% 10% 37%	1594
	21st to end	Night	12% 9% 4 7% 6% 4 7% 6% 6% 8% 31%	1434
June	1st to 10th	Night	9% 6% 2 6% 6% 4 6% 5% 5% 8% 42%	1260
	11th to 20th	Night	13% 5% 3 4 4 3 4 5% 6% 7% 45%	1260
	21st to end	Night	3 2 1 3 3 3 5% 5% 6% 8% 61%	1260
July	1st to 10th	Night	2 1 1 3 3 3 5% 4 5% 8% 65%	1319
	11th to 20th	Night	1 2 1 3 2 2 3 3 4 9% 69%	1440
	21st to end	Night	2 2 1 2 3 2 4 5% 5% 5% 70%	1576
August	1st to 10th	Night	3 3 2 5% 5% 4 5% 3 6% 9% 55%	1601
	11th to 20th	Night	2 2 1 2 2 1 3 4 6% 9% 67%	1602
	21st to end	Night	5% 3 2 4 4 2 4 5% 5% 7% 60%	1784
September	1st to 10th	Night	5% 3 1 3 3 2 3 4 4 6% 65%	1862
	11th to 20th	Night	6% 3 2 5% 5% 2 4 4 4 8% 57%	1980
	21st to end	Night	6% 4 2 4 4 3 4 3 5% 6% 60%	1980
October	1st to 10th	Night	7% 8% 3 5% 5% 3 4 4 5% 7% 49%	2014
	11th to 20th	Night	6% 6% 2 4 5% 3 5% 5% 6% 8% 51%	2189
	21st to end	Night	5% 7% 3 5% 6% 4 6% 5% 7% 10% 42%	2574
November	1st to 10th	Night	6% 7% 4 5% 6% 4 5% 6% 8% 9% 38%	2405
	11th to 20th	Night	4 8% 3 7% 8% 4 7% 7% 7% 10% 34%	2511
	21st to end	Night	3 5% 2 6% 7% 4 7% 7% 8% 11% 38%	2660
December	1st to 10th	Night	3 7% 4 6% 8% 5% 7% 8% 9% 12% 31%	2807
	11th to 20th	Night	3 9% 4 10% 9% 5% 9% 9% 9% 9% 24%	3506
	21st to end	Night	3 8% 5% 12% 11% 7% 10% 10% 8% 9% 18%	5214

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	46% 11% 24% 14% 4 1	1509
	11th to 20th	Day	42% 10% 22% 17% 7% 3	1464
	21st to end	Day	46% 9% 19% 21% 6%	1584
February	1st to 10th	Day	47% 12% 20% 17% 4	1620
	11th to 20th	Day	47% 10% 21% 16% 6%	1659
	21st to end	Day	52% 8% 14% 18% 7% 1	1480
March	1st to 10th	Day	45% 11% 21% 17% 7%	1805
	11th to 20th	Day	44% 10% 20% 20% 5%	1980
	21st to end	Day	55% 8% 19% 14% 4	2178
April	1st to 10th	Day	52% 9% 16% 16% 6% 1	2136
	11th to 20th	Day	49% 7% 15% 20% 8% 1	2292
	21st to end	Day	50% 7% 13% 23% 6% 1	2340
May	1st to 10th	Day	44% 7% 16% 24% 9% 1	2340
	11th to 20th	Day	46% 8% 17% 21% 8% 1	2304
	21st to end	Day	55% 9% 16% 14% 5% 1	2836
June	1st to 10th	Day	47% 9% 16% 21% 6% 1	2700
	11th to 20th	Day	40% 8% 11% 22% 13% 5%	2700
	21st to end	Day	27% 6% 9% 24% 27% 6%	2700
July	1st to 10th	Day	21% 8% 12% 22% 23% 14%	2566
	11th to 20th	Day	18% 5% 7% 17% 25% 28%	2445
	21st to end	Day	22% 5% 6% 16% 30% 22%	2589
August	1st to 10th	Day	30% 6% 9% 20% 23% 12%	2321
	11th to 20th	Day	17% 5% 9% 27% 30% 11%	2299
	21st to end	Day	22% 6% 8% 25% 27% 12%	2570
September	1st to 10th	Day	20% 5% 8% 23% 28% 15%	2097
	11th to 20th	Day	28% 6% 12% 23% 25% 6%	1980
	21st to end	Day	27% 4 14% 31% 22% 2	1980
October	1st to 10th	Day	40% 6% 15% 25% 13% 2	1945
	11th to 20th	Day	33% 7% 19% 28% 11% 1	1769
	21st to end	Day	38% 8% 19% 25% 9% 1	1782
November	1st to 10th	Day	40% 9% 18% 23% 8% 2	1674
	11th to 20th	Day	41% 10% 25% 20% 4 1	1649
	21st to end	Day	40% 8% 22% 21% 8% 1	1520
December	1st to 10th	Day	42% 12% 21% 18% 7% 1	1368
	11th to 20th	Day	43% 10% 28% 17% 2	1684
	21st to end	Day	42% 10% 20% 18% 9% 1	2442
January	1st to 10th	Night	47% 13% 20% 15% 4	2671
	11th to 20th	Night	45% 11% 17% 18% 7% 2	2574
	21st to end	Night	44% 10% 19% 19% 7% 1	2771
February	1st to 10th	Night	51% 10% 20% 15% 4	2340
	11th to 20th	Night	48% 8% 21% 17% 7%	2197
	21st to end	Night	46% 9% 16% 20% 8% 1	1776
March	1st to 10th	Night	42% 10% 23% 18% 6%	2154
	11th to 20th	Night	36% 9% 24% 24% 6%	1980
	21st to end	Night	47% 10% 21% 18% 4	2178
April	1st to 10th	Night	43% 9% 19% 22% 6% 1	1822
	11th to 20th	Night	42% 8% 17% 22% 10%	1619
	21st to end	Night	42% 8% 21% 22% 7%	1620
May	1st to 10th	Night	38% 7% 18% 29% 7%	1620
	11th to 20th	Night	40% 11% 19% 22% 7%	1595
	21st to end	Night	50% 10% 20% 15% 4	1434
June	1st to 10th	Night	38% 10% 20% 24% 7% 1	1260
	11th to 20th	Night	37% 7% 14% 24% 13% 5%	1260
	21st to end	Night	20% 6% 15% 28% 24% 7%	1260
July	1st to 10th	Night	16% 6% 12% 30% 24% 12%	1281
	11th to 20th	Night	13% 4 9% 23% 27% 24%	1392
	21st to end	Night	15% 4 7% 21% 33% 20%	1488
August	1st to 10th	Night	25% 6% 11% 23% 21% 13%	1593
	11th to 20th	Night	14% 5% 13% 29% 28% 12%	1602
	21st to end	Night	22% 6% 9% 26% 25% 12%	1784
September	1st to 10th	Night	19% 4 9% 26% 26% 15%	1862
	11th to 20th	Night	26% 6% 13% 23% 26% 6%	1980
	21st to end	Night	26% 3 13% 30% 24% 4	1980
October	1st to 10th	Night	34% 6% 16% 28% 15% 2	2014
	11th to 20th	Night	32% 6% 15% 33% 13% 1	2189
	21st to end	Night	39% 7% 18% 23% 12%	2574
November	1st to 10th	Night	39% 8% 18% 24% 9% 2	2405
	11th to 20th	Night	42% 10% 21% 22% 5% 1	2511
	21st to end	Night	37% 8% 22% 23% 9% 1	2660
December	1st to 10th	Night	41% 12% 20% 19% 7% 1	2807
	11th to 20th	Night	45% 10% 24% 18% 3	3507
	21st to end	Night	46% 10% 19% 14% 9% 1	5214

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 12% 36% 28% 18% 1	180
	11th to 20th	Day	5% 8% 39% 28% 14% 7%	166
	21st to end	Day	7% 11% 39% 31% 10% 2	176
February	1st to 10th	Day	12% 14% 44% 28% 3	240
	11th to 20th	Day	5% 18% 39% 28% 8% 2	315
	21st to end	Day	9% 21% 36% 27% 8%	346
March	1st to 10th	Day	8% 21% 41% 25% 4 1	420
	11th to 20th	Day	9% 21% 31% 29% 9% 1	420
	21st to end	Day	10% 26% 37% 20% 7% 1	462
April	1st to 10th	Day	13% 22% 34% 22% 8% 1	420
	11th to 20th	Day	11% 28% 32% 21% 6% 2	412
	21st to end	Day	16% 24% 29% 22% 6% 3	420
May	1st to 10th	Day	11% 22% 28% 27% 11% 1	423
	11th to 20th	Day	16% 17% 28% 26% 11% 2	448
	21st to end	Day	12% 15% 24% 25% 19% 4	600
June	1st to 10th	Day	10% 14% 25% 31% 17% 4	630
	11th to 20th	Day	15% 18% 27% 27% 12% 1	630
	21st to end	Day	4 12% 23% 36% 22% 2	630
July	1st to 10th	Day	4 10% 29% 34% 20% 3	561
	11th to 20th	Day	4 11% 41% 31% 13% 2	444
	21st to end	Day	4 11% 31% 34% 15% 5%	487
August	1st to 10th	Day	6% 8% 33% 35% 15% 4	447
	11th to 20th	Day	4 8% 27% 35% 19% 7%	437
	21st to end	Day	6% 8% 31% 32% 18% 5%	495
September	1st to 10th	Day	5% 11% 27% 31% 22% 4	450
	11th to 20th	Day	9% 10% 26% 32% 18% 5%	450
	21st to end	Day	11% 11% 26% 31% 20% 2	450
October	1st to 10th	Day	11% 11% 29% 27% 17% 5%	415
	11th to 20th	Day	9% 11% 28% 28% 16% 8%	270
	21st to end	Day	8% 14% 35% 30% 11% 3	297
November	1st to 10th	Day	9% 11% 38% 27% 15% 1	270
	11th to 20th	Day	5% 14% 37% 31% 10% 2	270
	21st to end	Day	4 8% 35% 40% 12% 1	270
December	1st to 10th	Day	5% 11% 38% 25% 18% 4	198
	11th to 20th	Day	9% 10% 42% 27% 11% 2	180
	21st to end	Day	7% 9% 42% 28% 13% 1	198
January	1st to 10th	Night	7% 6% 36% 41% 10%	785
	11th to 20th	Night	6% 6% 39% 36% 12% 1	736
	21st to end	Night	5% 6% 36% 41% 10% 1	792
February	1st to 10th	Night	8% 7% 43% 36% 6% 1	720
	11th to 20th	Night	6% 9% 39% 37% 8% 1	704
	21st to end	Night	4 10% 37% 37% 11% 1	592
March	1st to 10th	Night	4 6% 40% 40% 9% 1	720
	11th to 20th	Night	5% 9% 33% 39% 13% 1	720
	21st to end	Night	8% 10% 31% 41% 9% 1	792
April	1st to 10th	Night	8% 8% 28% 40% 15% 1	720
	11th to 20th	Night	7% 11% 34% 38% 9% 1	551
	21st to end	Night	9% 9% 30% 37% 14% 1	540
May	1st to 10th	Night	10% 9% 24% 40% 16% 1	540
	11th to 20th	Night	10% 9% 20% 36% 24% 1	531
	21st to end	Night	15% 5% 20% 33% 25% 2	389
June	1st to 10th	Night	13% 4 17% 41% 24% 2	360
	11th to 20th	Night	16% 3 21% 41% 18% 1	360
	21st to end	Night	4 1 16% 48% 29% 1	360
July	1st to 10th	Night	2 1 11% 49% 35% 2	350
	11th to 20th	Night	1 2 15% 54% 28%	348
	21st to end	Night	2 1 10% 51% 35% 2	394
August	1st to 10th	Night	4 2 14% 49% 29% 2	527
	11th to 20th	Night	2 2 11% 50% 32% 3	534
	21st to end	Night	6% 4 15% 42% 31% 1	596
September	1st to 10th	Night	6% 1 16% 41% 31% 4	720
	11th to 20th	Night	7% 2 11% 43% 33% 5%	720
	21st to end	Night	8% 3 18% 39% 27% 5%	720
October	1st to 10th	Night	10% 6% 21% 39% 21% 3	720
	11th to 20th	Night	10% 6% 20% 42% 17% 4	720
	21st to end	Night	9% 7% 26% 41% 13% 4	792
November	1st to 10th	Night	9% 7% 28% 44% 12% 1	740
	11th to 20th	Night	8% 9% 36% 37% 10% 1	801
	21st to end	Night	5% 7% 33% 41% 12% 1	950
December	1st to 10th	Night	7% 5% 38% 39% 10% 2	950
	11th to 20th	Night	7% 7% 36% 40% 9% 1	950
	21st to end	Night	6% 8% 41% 33% 11% 1	1045

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