Wenatchee
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wenatchee clear sky chart from 2005-11-06 to 2026-01-17.

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% 4 4 5% 4 6% 8% 52%	131476
	Night	4 7% 3 7% 5% 4 5% 4 6% 8% 49%	128944
Transparency	Day	28% 8% 13% 25% 18% 7%	131203
	Night	32% 9% 15% 25% 15% 5%	128794
Seeing	Day	9% 13% 28% 31% 16% 4	15754
	Night	9% 8% 25% 37% 19% 2	24835

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	4 14% 5% 11% 8% 6% 6% 5% 7% 8% 26%	3719
	11th to 20th	Day	3 12% 3 8% 5% 4 4 5% 7% 8% 40%	3664
	21st to end	Day	6% 13% 4 9% 5% 5% 5% 6% 8% 6% 32%	4004
February	1st to 10th	Day	4 10% 5% 9% 6% 7% 7% 6% 7% 9% 31%	1756
	11th to 20th	Day	4 10% 4 7% 6% 5% 6% 5% 7% 10% 36%	1755
	21st to end	Day	3 9% 5% 9% 5% 5% 7% 6% 8% 9% 34%	1643
March	1st to 10th	Day	2 5% 2 6% 5% 6% 7% 6% 9% 11% 41%	4518
	11th to 20th	Day	2 5% 2 6% 4 5% 6% 5% 7% 9% 48%	4866
	21st to end	Day	5% 7% 2 7% 6% 7% 7% 6% 9% 11% 33%	5836
April	1st to 10th	Day	5% 7% 2 8% 6% 6% 7% 6% 8% 10% 35%	2400
	11th to 20th	Day	3 8% 2 6% 5% 6% 5% 5% 7% 8% 45%	2372
	21st to end	Day	4 5% 2 6% 5% 6% 6% 5% 7% 9% 46%	2639
May	1st to 10th	Day	4 3 1 4 3 3 4 3 6% 8% 61%	6320
	11th to 20th	Day	4 3 2 5% 4 4 5% 5% 6% 10% 53%	6277
	21st to end	Day	5% 5% 2 6% 4 5% 4 4 6% 8% 50%	6903
June	1st to 10th	Day	7% 5% 2 5% 5% 5% 5% 5% 6% 8% 47%	2800
	11th to 20th	Day	3 4 2 5% 4 5% 5% 4 7% 8% 52%	2800
	21st to end	Day	2 3 1 5% 3 4 4 3 6% 7% 62%	2800
July	1st to 10th	Day	1 1 1 2 2 2 2 3 4 81%	6320
	11th to 20th	Day	1 1 1 2 2 2 1 2 3 4 81%	6320
	21st to end	Day	2 1 1 2 2 2 2 2 4 6% 76%	6874
August	1st to 10th	Day	1 1 2 2 3 3 3 4 6% 74%	4541
	11th to 20th	Day	1 1 1 2 2 2 3 3 6% 10% 70%	4256
	21st to end	Day	2 3 1 4 3 3 4 4 5% 6% 64%	4322
September	1st to 10th	Day	2 2 1 2 3 3 3 3 5% 7% 70%	2400
	11th to 20th	Day	3 3 1 4 4 5% 5% 4 6% 8% 57%	2400
	21st to end	Day	4 3 1 4 3 4 5% 4 5% 8% 59%	2154
October	1st to 10th	Day	3 3 1 3 2 3 4 3 5% 8% 64%	3280
	11th to 20th	Day	3 3 1 5% 3 4 6% 5% 8% 11% 50%	3261
	21st to end	Day	4 5% 1 5% 4 5% 6% 5% 8% 10% 48%	3212
November	1st to 10th	Day	5% 9% 3 6% 6% 6% 7% 6% 7% 9% 35%	1807
	11th to 20th	Day	3 10% 3 9% 8% 7% 7% 5% 8% 8% 33%	1680
	21st to end	Day	5% 11% 3 8% 5% 7% 6% 6% 8% 10% 32%	1680
December	1st to 10th	Day	3 7% 3 9% 6% 7% 7% 6% 8% 7% 37%	2700
	11th to 20th	Day	4 12% 6% 15% 8% 7% 7% 4 8% 7% 21%	3105
	21st to end	Day	5% 14% 7% 14% 8% 6% 5% 5% 6% 6% 24%	4092
January	1st to 10th	Night	5% 15% 7% 15% 7% 5% 5% 5% 6% 7% 23%	6446
	11th to 20th	Night	4 10% 4 7% 5% 5% 5% 4 6% 8% 40%	6366
	21st to end	Night	4 14% 5% 12% 8% 6% 5% 4 6% 5% 31%	6952
February	1st to 10th	Night	4 14% 4 9% 6% 6% 5% 5% 8% 8% 31%	2640
	11th to 20th	Night	5% 9% 4 7% 6% 6% 6% 4 6% 9% 39%	2532
	21st to end	Night	4 10% 4 11% 7% 5% 5% 5% 7% 8% 36%	1986
March	1st to 10th	Night	2 6% 1 5% 4 4 5% 5% 10% 13% 46%	5376
	11th to 20th	Night	2 5% 2 6% 5% 4 5% 5% 7% 8% 52%	5131
	21st to end	Night	4 6% 3 7% 6% 6% 7% 5% 9% 9% 39%	5138
April	1st to 10th	Night	4 6% 2 7% 6% 5% 6% 5% 7% 10% 44%	2000
	11th to 20th	Night	3 6% 2 5% 4 5% 5% 3 6% 7% 53%	1979
	21st to end	Night	4 4 2 4 5% 4 4 4 6% 10% 51%	1757
May	1st to 10th	Night	3 3 1 3 3 2 3 3 5% 7% 66%	3640
	11th to 20th	Night	3 4 2 5% 4 3 4 4 6% 7% 57%	3616
	21st to end	Night	5% 2 1 3 3 3 4 4 6% 11% 58%	3972
June	1st to 10th	Night	5% 5% 2 3 3 4 4 4 8% 8% 53%	1600
	11th to 20th	Night	4 3 1 3 4 4 5% 5% 7% 8% 57%	1600
	21st to end	Night	1 2 1 3 4 4 3 4 6% 6% 67%	1600
July	1st to 10th	Night	1 2 1 2 1 1 1 1 2 4 84%	3640
	11th to 20th	Night	1 1 1 1 2 3 3 87%	3640
	21st to end	Night	1 1 1 1 2 2 2 4 5% 81%	3969
August	1st to 10th	Night	1 1 2 1 3 3 2 4 7% 76%	2609
	11th to 20th	Night	2 1 2 2 2 3 3 4 7% 75%	2797
	21st to end	Night	3 2 1 2 2 2 3 4 6% 7% 69%	3597
September	1st to 10th	Night	2 2 1 2 2 2 3 2 5% 9% 70%	2000
	11th to 20th	Night	3 2 1 4 4 3 4 3 5% 8% 63%	2000
	21st to end	Night	2 3 1 3 3 3 4 4 7% 9% 61%	2243
October	1st to 10th	Night	3 3 2 3 3 3 3 3 6% 9% 62%	3920
	11th to 20th	Night	3 3 1 4 4 3 5% 4 7% 10% 56%	3897
	21st to end	Night	5% 5% 2 6% 4 5% 5% 5% 6% 8% 50%	4587
November	1st to 10th	Night	7% 8% 3 6% 5% 6% 6% 5% 8% 9% 37%	2708
	11th to 20th	Night	5% 9% 3 8% 6% 6% 7% 5% 6% 9% 36%	2940
	21st to end	Night	4 12% 4 9% 7% 6% 6% 5% 6% 7% 33%	2940
December	1st to 10th	Night	3 8% 3 10% 6% 5% 6% 4 6% 7% 43%	4700
	11th to 20th	Night	4 15% 6% 16% 8% 6% 7% 5% 7% 9% 19%	5320
	21st to end	Night	7% 17% 7% 11% 6% 6% 6% 3 6% 7% 25%	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	53% 13% 14% 14% 5%	3719
	11th to 20th	Day	40% 9% 20% 24% 7%	3688
	21st to end	Day	49% 12% 14% 20% 5%	4004
February	1st to 10th	Day	49% 13% 17% 16% 4 2	1756
	11th to 20th	Day	42% 14% 17% 18% 8% 1	1764
	21st to end	Day	40% 13% 20% 19% 7% 1	1643
March	1st to 10th	Day	29% 11% 17% 23% 18% 1	4518
	11th to 20th	Day	29% 8% 13% 37% 12% 2	4866
	21st to end	Day	38% 14% 23% 20% 6%	5836
April	1st to 10th	Day	41% 11% 16% 23% 9% 1	2400
	11th to 20th	Day	35% 8% 16% 23% 15% 3	2372
	21st to end	Day	33% 9% 15% 26% 14% 3	2639
May	1st to 10th	Day	21% 5% 10% 29% 27% 8%	6320
	11th to 20th	Day	24% 7% 15% 30% 21% 2	6280
	21st to end	Day	28% 9% 16% 34% 13% 1	6904
June	1st to 10th	Day	34% 7% 12% 25% 17% 5%	2800
	11th to 20th	Day	27% 6% 14% 28% 21% 4	2800
	21st to end	Day	22% 4 13% 32% 23% 6%	2800
July	1st to 10th	Day	9% 3 6% 21% 30% 31%	6251
	11th to 20th	Day	10% 2 4 17% 33% 35%	6245
	21st to end	Day	11% 2 5% 29% 34% 18%	6681
August	1st to 10th	Day	12% 3 7% 20% 37% 21%	4524
	11th to 20th	Day	11% 4 12% 42% 26% 5%	4298
	21st to end	Day	21% 5% 11% 27% 30% 6%	4321
September	1st to 10th	Day	16% 4 10% 29% 31% 10%	2400
	11th to 20th	Day	24% 8% 14% 24% 24% 6%	2400
	21st to end	Day	24% 7% 16% 29% 18% 5%	2154
October	1st to 10th	Day	19% 5% 14% 40% 21% 2	3280
	11th to 20th	Day	26% 11% 20% 24% 18% 1	3261
	21st to end	Day	28% 9% 17% 26% 13% 5%	3212
November	1st to 10th	Day	42% 12% 17% 19% 10% 1	1807
	11th to 20th	Day	44% 15% 19% 16% 6% 1	1680
	21st to end	Day	43% 16% 19% 13% 7% 2	1680
December	1st to 10th	Day	38% 14% 21% 21% 7%	2700
	11th to 20th	Day	55% 17% 12% 11% 4	3108
	21st to end	Day	56% 12% 12% 15% 4	4092
January	1st to 10th	Night	56% 13% 14% 13% 4	6446
	11th to 20th	Night	39% 10% 17% 26% 8%	6404
	21st to end	Night	52% 11% 15% 17% 5%	6952
February	1st to 10th	Night	47% 13% 16% 17% 5% 1	2640
	11th to 20th	Night	40% 11% 20% 19% 8% 2	2534
	21st to end	Night	42% 12% 17% 20% 9% 1	1986
March	1st to 10th	Night	26% 9% 20% 28% 14% 3	5376
	11th to 20th	Night	28% 7% 17% 35% 13% 1	5132
	21st to end	Night	34% 14% 23% 23% 6%	5138
April	1st to 10th	Night	34% 9% 20% 25% 10% 1	2000
	11th to 20th	Night	30% 8% 17% 24% 18% 2	1979
	21st to end	Night	28% 10% 14% 31% 16% 1	1757
May	1st to 10th	Night	18% 5% 9% 30% 33% 5%	3637
	11th to 20th	Night	23% 6% 16% 32% 22% 1	3616
	21st to end	Night	20% 7% 22% 37% 13% 1	3972
June	1st to 10th	Night	27% 9% 15% 27% 19% 4	1600
	11th to 20th	Night	24% 8% 14% 32% 20% 3	1600
	21st to end	Night	18% 6% 13% 36% 23% 5%	1600
July	1st to 10th	Night	8% 2 7% 25% 26% 32%	3600
	11th to 20th	Night	5% 1 4 21% 34% 35%	3592
	21st to end	Night	8% 2 7% 29% 34% 20%	3857
August	1st to 10th	Night	11% 2 7% 19% 39% 21%	2601
	11th to 20th	Night	11% 4 17% 38% 23% 7%	2821
	21st to end	Night	14% 6% 14% 28% 31% 7%	3597
September	1st to 10th	Night	14% 5% 12% 28% 31% 11%	2000
	11th to 20th	Night	21% 7% 11% 28% 25% 9%	2000
	21st to end	Night	20% 7% 15% 33% 18% 7%	2243
October	1st to 10th	Night	19% 5% 12% 47% 16% 1	3920
	11th to 20th	Night	24% 9% 17% 31% 17% 1	3897
	21st to end	Night	30% 10% 16% 27% 15% 2	4587
November	1st to 10th	Night	40% 12% 18% 19% 10% 1	2708
	11th to 20th	Night	42% 13% 18% 19% 7% 1	2940
	21st to end	Night	46% 13% 17% 16% 8% 1	2940
December	1st to 10th	Night	38% 11% 21% 24% 6%	4700
	11th to 20th	Night	57% 16% 15% 9% 4	5316
	21st to end	Night	53% 13% 14% 12% 6%	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	11% 14% 21% 38% 13% 3	220
	11th to 20th	Day	14% 11% 23% 32% 17% 4	212
	21st to end	Day	12% 10% 19% 35% 19% 5%	220
February	1st to 10th	Day	11% 9% 35% 34% 8% 2	356
	11th to 20th	Day	12% 14% 34% 29% 9% 2	395
	21st to end	Day	8% 17% 35% 29% 10% 2	411
March	1st to 10th	Day	11% 14% 32% 28% 13% 2	500
	11th to 20th	Day	11% 18% 24% 30% 16% 2	500
	21st to end	Day	12% 19% 34% 25% 10% 1	550
April	1st to 10th	Day	15% 18% 29% 25% 10% 2	500
	11th to 20th	Day	10% 21% 34% 24% 9% 3	492
	21st to end	Day	12% 17% 29% 23% 14% 4	500
May	1st to 10th	Day	11% 14% 33% 30% 10% 2	503
	11th to 20th	Day	15% 14% 28% 26% 13% 4	528
	21st to end	Day	11% 12% 27% 31% 15% 5%	573
June	1st to 10th	Day	10% 15% 29% 27% 16% 3	530
	11th to 20th	Day	11% 18% 34% 26% 10% 2	530
	21st to end	Day	5% 12% 30% 29% 21% 4	530
July	1st to 10th	Day	5% 9% 25% 42% 17% 2	526
	11th to 20th	Day	2 12% 29% 33% 19% 6%	524
	21st to end	Day	2 8% 24% 36% 24% 6%	575
August	1st to 10th	Day	5% 6% 23% 34% 24% 7%	527
	11th to 20th	Day	2 6% 21% 39% 23% 9%	517
	21st to end	Day	5% 11% 25% 30% 21% 8%	583
September	1st to 10th	Day	3 9% 25% 32% 21% 9%	530
	11th to 20th	Day	6% 10% 26% 34% 21% 4	530
	21st to end	Day	9% 12% 24% 35% 15% 4	530
October	1st to 10th	Day	11% 11% 28% 29% 16% 5%	530
	11th to 20th	Day	11% 12% 26% 28% 18% 5%	530
	21st to end	Day	13% 11% 25% 35% 14% 2	375
November	1st to 10th	Day	12% 14% 23% 34% 15% 1	305
	11th to 20th	Day	11% 13% 27% 25% 18% 6%	220
	21st to end	Day	6% 11% 27% 33% 18% 4	220
December	1st to 10th	Day	12% 9% 21% 28% 20% 9%	220
	11th to 20th	Day	7% 12% 28% 37% 16%	220
	21st to end	Day	9% 9% 22% 41% 15% 4	242
January	1st to 10th	Night	16% 10% 29% 32% 13% 2	840
	11th to 20th	Night	12% 11% 24% 37% 15% 2	824
	21st to end	Night	13% 8% 22% 38% 17% 3	880
February	1st to 10th	Night	13% 8% 30% 35% 13% 1	800
	11th to 20th	Night	11% 8% 26% 37% 16% 2	784
	21st to end	Night	11% 10% 26% 35% 15% 2	660
March	1st to 10th	Night	12% 8% 25% 37% 17% 1	800
	11th to 20th	Night	8% 8% 28% 35% 20% 1	800
	21st to end	Night	9% 11% 29% 38% 13% 1	880
April	1st to 10th	Night	8% 11% 26% 36% 18% 2	800
	11th to 20th	Night	6% 14% 30% 33% 15% 2	791
	21st to end	Night	7% 9% 33% 34% 16% 1	557
May	1st to 10th	Night	5% 8% 33% 36% 17% 2	400
	11th to 20th	Night	9% 5% 22% 39% 24% 2	394
	21st to end	Night	7% 7% 22% 39% 23% 3	433
June	1st to 10th	Night	8% 6% 27% 39% 19% 2	400
	11th to 20th	Night	5% 10% 33% 39% 14% 1	400
	21st to end	Night	2 8% 28% 36% 26% 1	400
July	1st to 10th	Night	2 4 25% 44% 24% 1	390
	11th to 20th	Night	1 5% 30% 42% 20% 2	388
	21st to end	Night	1 5% 20% 46% 28% 1	438
August	1st to 10th	Night	2 2 17% 41% 35% 3	398
	11th to 20th	Night	2 2 18% 38% 36% 5%	525
	21st to end	Night	4 6% 20% 40% 27% 4	869
September	1st to 10th	Night	4 4 19% 40% 31% 4	800
	11th to 20th	Night	5% 5% 18% 35% 31% 7%	800
	21st to end	Night	5% 6% 21% 40% 25% 4	800
October	1st to 10th	Night	9% 7% 19% 38% 25% 2	800
	11th to 20th	Night	5% 9% 23% 37% 22% 4	800
	21st to end	Night	11% 8% 25% 40% 14% 3	880
November	1st to 10th	Night	13% 8% 24% 42% 13%	820
	11th to 20th	Night	13% 11% 27% 33% 15% 2	840
	21st to end	Night	12% 7% 26% 35% 17% 3	840
December	1st to 10th	Night	11% 8% 26% 36% 16% 3	840
	11th to 20th	Night	14% 10% 27% 38% 12%	840
	21st to end	Night	14% 9% 29% 39% 8% 1	924

Page generated at 2026-01-13 22:14:27. Version ac07

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