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 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 5% 6% 4 5% 6% 6% 8% 47%	74785
	Night	4 7% 3 6% 6% 3 5% 5% 6% 8% 45%	74992
Transparency	Day	34% 9% 14% 22% 16% 5%	74488
	Night	36% 10% 15% 22% 14% 4	74807
Seeing	Day	9% 13% 28% 31% 16% 4	13244
	Night	9% 8% 24% 37% 19% 2	22361

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	5% 14% 6% 9% 10% 5% 7% 8% 7% 8% 20%	1519
	11th to 20th	Day	5% 11% 5% 9% 8% 5% 7% 7% 8% 8% 27%	1464
	21st to end	Day	5% 11% 4 8% 8% 6% 8% 6% 7% 10% 29%	1584
February	1st to 10th	Day	5% 9% 5% 8% 7% 4 7% 8% 7% 9% 31%	1580
	11th to 20th	Day	4 9% 4 6% 6% 4 5% 6% 7% 9% 38%	1575
	21st to end	Day	3 7% 5% 9% 6% 4 7% 7% 8% 9% 34%	1474
March	1st to 10th	Day	4 9% 3 7% 7% 4 6% 7% 7% 9% 37%	1800
	11th to 20th	Day	3 7% 4 8% 7% 5% 7% 7% 7% 10% 35%	1924
	21st to end	Day	4 7% 3 7% 8% 5% 8% 8% 8% 10% 33%	2321
April	1st to 10th	Day	6% 7% 2 7% 7% 5% 7% 8% 8% 10% 35%	2160
	11th to 20th	Day	3 8% 3 5% 6% 4 6% 7% 7% 8% 42%	2132
	21st to end	Day	4 4 2 5% 6% 4 6% 7% 7% 10% 45%	2374
May	1st to 10th	Day	4 3 2 4 5% 3 5% 6% 7% 10% 51%	2520
	11th to 20th	Day	7% 5% 3 5% 7% 4 6% 6% 7% 10% 40%	2477
	21st to end	Day	8% 6% 2 5% 6% 4 5% 6% 7% 9% 40%	2723
June	1st to 10th	Day	7% 4 2 5% 5% 4 6% 6% 6% 8% 46%	2520
	11th to 20th	Day	4 3 2 4 6% 4 6% 5% 7% 9% 51%	2520
	21st to end	Day	2 3 2 4 4 3 4 4 5% 7% 61%	2520
July	1st to 10th	Day	2 1 1 2 3 2 4 5% 5% 7% 68%	2520
	11th to 20th	Day	2 2 1 3 3 2 3 3 4 6% 71%	2520
	21st to end	Day	1 1 1 2 2 2 2 3 4 81%	2741
August	1st to 10th	Day	2 1 1 2 3 2 4 4 4 6% 72%	2507
	11th to 20th	Day	1 1 1 2 2 2 2 3 4 7% 73%	2359
	21st to end	Day	1 2 1 2 3 2 4 5% 6% 8% 65%	2386
September	1st to 10th	Day	2 2 1 2 3 2 3 3 5% 7% 71%	2160
	11th to 20th	Day	3 3 2 3 4 4 5% 6% 6% 8% 55%	2160
	21st to end	Day	4 4 1 3 4 3 5% 5% 5% 8% 58%	1940
October	1st to 10th	Day	6% 5% 2 4 4 3 5% 5% 6% 8% 53%	1800
	11th to 20th	Day	5% 4 2 5% 4 4 6% 6% 7% 8% 50%	1800
	21st to end	Day	7% 7% 2 6% 5% 3 6% 6% 7% 9% 43%	1794
November	1st to 10th	Day	6% 8% 3 6% 7% 5% 7% 7% 7% 9% 35%	1632
	11th to 20th	Day	3 9% 4 8% 8% 6% 7% 7% 8% 8% 34%	1520
	21st to end	Day	5% 10% 4 7% 6% 5% 7% 7% 8% 10% 33%	1520
December	1st to 10th	Day	5% 10% 5% 9% 8% 5% 5% 7% 8% 7% 32%	1520
	11th to 20th	Day	5% 12% 5% 12% 9% 5% 8% 6% 9% 8% 21%	1925
	21st to end	Day	6% 14% 9% 13% 9% 5% 5% 6% 5% 5% 22%	2794
January	1st to 10th	Night	6% 14% 7% 10% 9% 5% 6% 7% 7% 7% 22%	2646
	11th to 20th	Night	5% 11% 6% 9% 9% 5% 7% 6% 7% 8% 26%	2568
	21st to end	Night	5% 11% 6% 9% 8% 5% 6% 7% 8% 9% 27%	2772
February	1st to 10th	Night	5% 12% 5% 8% 7% 4 6% 6% 8% 8% 32%	2376
	11th to 20th	Night	6% 6% 3 6% 7% 4 6% 6% 6% 10% 40%	2272
	21st to end	Night	4 10% 3 9% 8% 4 4 6% 7% 8% 36%	1781
March	1st to 10th	Night	5% 10% 3 5% 6% 3 6% 6% 9% 9% 37%	2160
	11th to 20th	Night	3 6% 2 6% 6% 4 6% 7% 8% 10% 42%	2033
	21st to end	Night	5% 6% 3 6% 6% 4 6% 7% 8% 11% 39%	2034
April	1st to 10th	Night	5% 5% 2 6% 6% 4 6% 6% 8% 10% 43%	1800
	11th to 20th	Night	3 6% 2 5% 5% 4 6% 5% 5% 8% 52%	1779
	21st to end	Night	5% 4 3 3 5% 3 5% 5% 6% 10% 51%	1583
May	1st to 10th	Night	4 2 2 4 5% 2 4 5% 7% 9% 57%	1440
	11th to 20th	Night	7% 3 1 5% 4 3 5% 5% 6% 9% 51%	1416
	21st to end	Night	6% 3 2 4 5% 3 5% 6% 7% 11% 49%	1552
June	1st to 10th	Night	6% 5% 2 4 3 3 4 6% 8% 8% 52%	1440
	11th to 20th	Night	4 3 1 3 5% 3 5% 6% 6% 8% 57%	1440
	21st to end	Night	1 2 1 3 4 2 4 4 6% 6% 67%	1440
July	1st to 10th	Night	2 1 1 2 2 2 2 3 5% 8% 72%	1440
	11th to 20th	Night	1 1 1 2 1 3 3 4 4 79%	1440
	21st to end	Night	1 1 1 2 2 4 4 86%	1576
August	1st to 10th	Night	1 1 1 1 2 3 3 4 7% 76%	1432
	11th to 20th	Night	1 2 2 2 1 2 3 3 6% 77%	1539
	21st to end	Night	1 2 1 1 3 2 3 4 5% 8% 70%	1969
September	1st to 10th	Night	3 2 1 1 2 2 3 3 5% 9% 71%	1800
	11th to 20th	Night	4 2 1 4 4 2 4 4 6% 7% 62%	1800
	21st to end	Night	3 3 1 3 3 2 4 5% 7% 9% 61%	2018
October	1st to 10th	Night	5% 5% 3 4 4 3 4 4 6% 7% 54%	2160
	11th to 20th	Night	4 4 1 4 5% 3 5% 6% 7% 9% 53%	2160
	21st to end	Night	7% 6% 3 5% 6% 3 5% 5% 6% 8% 46%	2561
November	1st to 10th	Night	8% 8% 3 6% 6% 4 6% 6% 8% 9% 38%	2443
	11th to 20th	Night	4 8% 3 7% 7% 5% 6% 7% 7% 8% 36%	2660
	21st to end	Night	3 10% 6% 8% 8% 4 7% 6% 6% 7% 35%	2660
December	1st to 10th	Night	5% 11% 6% 10% 8% 4 5% 5% 7% 8% 30%	2660
	11th to 20th	Night	5% 14% 5% 12% 9% 4 7% 7% 7% 10% 21%	3280
	21st to end	Night	6% 17% 9% 10% 6% 4 5% 5% 6% 7% 24%	4862

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	61% 14% 12% 7% 5% 1	1519
	11th to 20th	Day	53% 13% 16% 14% 4	1464
	21st to end	Day	51% 14% 14% 15% 5%	1584
February	1st to 10th	Day	50% 13% 17% 16% 4 1	1580
	11th to 20th	Day	40% 14% 18% 19% 8% 1	1584
	21st to end	Day	41% 13% 20% 18% 7% 1	1474
March	1st to 10th	Day	41% 13% 17% 19% 10% 1	1800
	11th to 20th	Day	43% 10% 13% 25% 8%	1924
	21st to end	Day	44% 12% 19% 18% 6% 1	2321
April	1st to 10th	Day	42% 11% 16% 22% 9% 1	2160
	11th to 20th	Day	38% 8% 16% 22% 13% 2	2132
	21st to end	Day	33% 10% 15% 25% 14% 3	2374
May	1st to 10th	Day	26% 8% 18% 32% 13% 3	2520
	11th to 20th	Day	36% 9% 16% 26% 13%	2480
	21st to end	Day	39% 8% 15% 27% 10% 1	2724
June	1st to 10th	Day	36% 7% 13% 25% 15% 4	2520
	11th to 20th	Day	29% 7% 15% 28% 18% 3	2520
	21st to end	Day	22% 4 13% 30% 23% 7%	2520
July	1st to 10th	Day	16% 6% 10% 24% 30% 14%	2451
	11th to 20th	Day	15% 4 7% 20% 33% 21%	2445
	21st to end	Day	9% 3 5% 21% 40% 22%	2589
August	1st to 10th	Day	14% 4 9% 24% 34% 15%	2490
	11th to 20th	Day	12% 4 9% 28% 38% 9%	2359
	21st to end	Day	16% 7% 10% 30% 30% 6%	2386
September	1st to 10th	Day	16% 4 10% 30% 30% 10%	2160
	11th to 20th	Day	25% 9% 13% 21% 24% 7%	2160
	21st to end	Day	26% 7% 17% 27% 18% 5%	1940
October	1st to 10th	Day	30% 7% 14% 32% 15% 2	1800
	11th to 20th	Day	30% 10% 19% 28% 12% 1	1800
	21st to end	Day	37% 10% 16% 24% 13% 1	1794
November	1st to 10th	Day	44% 12% 16% 18% 10% 1	1632
	11th to 20th	Day	44% 15% 18% 16% 5% 1	1520
	21st to end	Day	43% 16% 18% 14% 7% 2	1520
December	1st to 10th	Day	49% 12% 15% 17% 7%	1520
	11th to 20th	Day	56% 19% 12% 9% 3	1928
	21st to end	Day	60% 13% 10% 12% 5%	2794
January	1st to 10th	Night	57% 15% 13% 9% 5% 1	2646
	11th to 20th	Night	54% 12% 15% 14% 4	2568
	21st to end	Night	50% 13% 17% 15% 4 1	2772
February	1st to 10th	Night	46% 14% 17% 18% 4 1	2376
	11th to 20th	Night	39% 11% 20% 20% 8% 1	2274
	21st to end	Night	43% 11% 16% 19% 10%	1781
March	1st to 10th	Night	39% 12% 18% 21% 8% 1	2160
	11th to 20th	Night	35% 11% 17% 27% 9% 1	2034
	21st to end	Night	39% 12% 19% 24% 6%	2034
April	1st to 10th	Night	35% 9% 19% 25% 11% 1	1800
	11th to 20th	Night	32% 9% 17% 24% 17% 2	1779
	21st to end	Night	29% 11% 14% 29% 16% 1	1583
May	1st to 10th	Night	24% 8% 16% 32% 18% 3	1440
	11th to 20th	Night	30% 8% 16% 31% 14% 1	1416
	21st to end	Night	29% 9% 18% 30% 13% 1	1552
June	1st to 10th	Night	28% 9% 15% 26% 18% 3	1440
	11th to 20th	Night	25% 8% 14% 34% 16% 2	1440
	21st to end	Night	18% 6% 12% 35% 23% 6%	1440
July	1st to 10th	Night	14% 4 13% 26% 29% 14%	1400
	11th to 20th	Night	10% 3 9% 25% 31% 22%	1392
	21st to end	Night	5% 3 6% 21% 39% 26%	1488
August	1st to 10th	Night	10% 4 9% 26% 31% 20%	1424
	11th to 20th	Night	11% 3 10% 30% 34% 12%	1539
	21st to end	Night	14% 6% 12% 26% 34% 8%	1969
September	1st to 10th	Night	14% 5% 12% 27% 32% 11%	1800
	11th to 20th	Night	22% 7% 11% 24% 26% 9%	1800
	21st to end	Night	21% 8% 15% 33% 17% 7%	2018
October	1st to 10th	Night	30% 6% 11% 31% 19% 2	2160
	11th to 20th	Night	28% 10% 15% 29% 15% 2	2160
	21st to end	Night	36% 9% 13% 27% 14% 1	2561
November	1st to 10th	Night	40% 12% 17% 20% 10% 1	2443
	11th to 20th	Night	42% 13% 19% 19% 7% 1	2660
	21st to end	Night	45% 12% 17% 17% 8% 1	2660
December	1st to 10th	Night	50% 12% 16% 18% 4	2660
	11th to 20th	Night	55% 19% 15% 8% 3	3276
	21st to end	Night	56% 13% 12% 12% 7% 1	4862

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	13% 13% 22% 33% 15% 4	180
	11th to 20th	Day	17% 13% 23% 29% 13% 5%	166
	21st to end	Day	12% 10% 22% 33% 18% 5%	176
February	1st to 10th	Day	11% 11% 38% 32% 7% 1	300
	11th to 20th	Day	12% 14% 38% 26% 8% 1	335
	21st to end	Day	8% 17% 35% 29% 10% 2	344
March	1st to 10th	Day	12% 15% 33% 26% 12% 2	420
	11th to 20th	Day	11% 18% 23% 30% 16% 1	420
	21st to end	Day	12% 20% 34% 24% 9%	462
April	1st to 10th	Day	15% 20% 28% 25% 10% 2	420
	11th to 20th	Day	10% 23% 32% 23% 9% 3	412
	21st to end	Day	12% 18% 31% 23% 13% 3	420
May	1st to 10th	Day	10% 14% 33% 31% 10% 1	423
	11th to 20th	Day	15% 13% 26% 27% 14% 5%	448
	21st to end	Day	11% 11% 25% 32% 16% 5%	485
June	1st to 10th	Day	10% 16% 30% 26% 16% 2	450
	11th to 20th	Day	11% 18% 34% 25% 10% 1	450
	21st to end	Day	5% 12% 27% 29% 22% 4	450
July	1st to 10th	Day	5% 9% 22% 44% 17% 2	446
	11th to 20th	Day	2 13% 29% 32% 19% 5%	444
	21st to end	Day	1 8% 25% 37% 23% 6%	487
August	1st to 10th	Day	5% 7% 22% 34% 25% 6%	447
	11th to 20th	Day	2 6% 20% 39% 24% 9%	437
	21st to end	Day	4 12% 26% 31% 20% 7%	495
September	1st to 10th	Day	3 10% 29% 34% 19% 5%	450
	11th to 20th	Day	6% 11% 27% 33% 19% 4	450
	21st to end	Day	10% 13% 24% 34% 16% 4	450
October	1st to 10th	Day	12% 11% 27% 28% 16% 6%	450
	11th to 20th	Day	12% 12% 24% 28% 18% 5%	450
	21st to end	Day	14% 12% 26% 31% 14% 2	309
November	1st to 10th	Day	11% 14% 23% 36% 15% 1	250
	11th to 20th	Day	12% 12% 28% 24% 16% 7%	180
	21st to end	Day	4 11% 29% 32% 20% 3	180
December	1st to 10th	Day	13% 8% 21% 29% 21% 8%	180
	11th to 20th	Day	6% 11% 27% 38% 17% 1	180
	21st to end	Day	9% 10% 24% 38% 15% 4	198
January	1st to 10th	Night	16% 9% 29% 30% 14% 2	760
	11th to 20th	Night	13% 12% 22% 35% 16% 2	734
	21st to end	Night	14% 7% 22% 39% 16% 3	792
February	1st to 10th	Night	14% 8% 29% 36% 13% 1	720
	11th to 20th	Night	11% 8% 27% 36% 16% 2	704
	21st to end	Night	11% 10% 26% 35% 16% 2	592
March	1st to 10th	Night	13% 8% 26% 36% 16% 1	720
	11th to 20th	Night	8% 8% 27% 35% 20% 2	720
	21st to end	Night	9% 11% 28% 38% 13% 1	792
April	1st to 10th	Night	9% 10% 26% 36% 18% 2	720
	11th to 20th	Night	7% 13% 28% 33% 16% 3	711
	21st to end	Night	7% 9% 33% 34% 16% 1	503
May	1st to 10th	Night	6% 7% 33% 35% 17% 2	360
	11th to 20th	Night	9% 5% 18% 41% 25% 2	354
	21st to end	Night	7% 6% 21% 38% 24% 3	389
June	1st to 10th	Night	8% 6% 25% 39% 19% 2	360
	11th to 20th	Night	5% 10% 30% 39% 14% 1	360
	21st to end	Night	2 8% 28% 36% 27% 1	360
July	1st to 10th	Night	2 4 24% 45% 25% 1	350
	11th to 20th	Night	1 5% 30% 41% 21% 2	348
	21st to end	Night	1 4 20% 46% 28% 2	394
August	1st to 10th	Night	2 2 17% 39% 37% 3	358
	11th to 20th	Night	2 2 17% 36% 37% 5%	471
	21st to end	Night	3 7% 20% 40% 27% 4	781
September	1st to 10th	Night	4 4 20% 40% 28% 4	720
	11th to 20th	Night	5% 4 18% 33% 32% 8%	720
	21st to end	Night	5% 5% 19% 39% 27% 5%	720
October	1st to 10th	Night	10% 7% 18% 37% 27% 2	720
	11th to 20th	Night	5% 8% 21% 37% 24% 4	720
	21st to end	Night	12% 8% 22% 39% 15% 4	792
November	1st to 10th	Night	13% 8% 23% 42% 13%	740
	11th to 20th	Night	13% 10% 27% 33% 16% 2	760
	21st to end	Night	11% 7% 27% 34% 18% 3	760
December	1st to 10th	Night	11% 8% 26% 37% 15% 3	760
	11th to 20th	Night	13% 9% 25% 39% 13%	760
	21st to end	Night	14% 10% 28% 39% 8% 1	836

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