Lake Wenatchee
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Wenatchee clear sky chart from 2005-11-06 to 2024-03-18.

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	8% 9% 4 7% 7% 4 6% 5% 6% 8% 37%	78792
	Night	8% 10% 4 7% 6% 4 6% 6% 7% 8% 33%	80936
Transparency	Day	43% 5% 18% 20% 11% 2	78519
	Night	46% 6% 19% 19% 9% 1	80789
Seeing	Day	15% 20% 33% 21% 9% 2	13726
	Night	14% 13% 34% 27% 11% 1	22584

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	11% 21% 8% 14% 8% 4 6% 5% 5% 5% 14%	2539
	11th to 20th	Day	8% 16% 6% 12% 7% 4 5% 4 4 6% 27%	2516
	21st to end	Day	20% 21% 5% 8% 7% 4 5% 4 5% 5% 15%	2794
February	1st to 10th	Day	6% 16% 5% 9% 9% 5% 6% 6% 7% 9% 22%	1676
	11th to 20th	Day	6% 14% 6% 9% 7% 4 6% 5% 7% 9% 27%	1665
	21st to end	Day	6% 15% 6% 11% 8% 5% 7% 7% 9% 6% 21%	1536
March	1st to 10th	Day	7% 13% 6% 10% 8% 5% 7% 6% 8% 7% 24%	1900
	11th to 20th	Day	8% 14% 6% 8% 8% 6% 8% 6% 6% 7% 23%	2021
	21st to end	Day	8% 14% 5% 9% 10% 5% 7% 7% 7% 8% 20%	2304
April	1st to 10th	Day	8% 12% 4 9% 9% 5% 7% 7% 8% 8% 22%	2160
	11th to 20th	Day	7% 9% 5% 8% 9% 5% 7% 6% 8% 8% 28%	2132
	21st to end	Day	6% 8% 4 8% 8% 5% 7% 6% 8% 9% 30%	2397
May	1st to 10th	Day	6% 6% 3 7% 6% 4 6% 6% 9% 10% 37%	2520
	11th to 20th	Day	9% 8% 3 6% 6% 4 6% 6% 8% 10% 34%	2477
	21st to end	Day	9% 7% 4 8% 8% 6% 7% 6% 7% 8% 31%	2723
June	1st to 10th	Day	11% 6% 3 6% 7% 4 6% 7% 7% 9% 35%	2520
	11th to 20th	Day	6% 6% 4 7% 7% 4 6% 7% 8% 11% 35%	2564
	21st to end	Day	4 4 2 5% 5% 3 5% 6% 7% 9% 49%	2700
July	1st to 10th	Day	2 3 1 4 5% 3 5% 5% 5% 7% 58%	2592
	11th to 20th	Day	3 3 1 3 3 2 4 4 5% 6% 66%	2520
	21st to end	Day	1 2 1 2 3 1 3 3 4 6% 74%	2741
August	1st to 10th	Day	2 2 1 3 4 3 3 5% 6% 8% 64%	2507
	11th to 20th	Day	3 1 1 3 3 2 3 4 5% 9% 66%	2346
	21st to end	Day	2 3 2 5% 5% 3 5% 5% 6% 8% 56%	2412
September	1st to 10th	Day	3 2 2 3 4 2 3 5% 6% 8% 62%	2160
	11th to 20th	Day	5% 5% 2 4 6% 4 6% 6% 7% 8% 47%	2160
	21st to end	Day	8% 6% 2 5% 6% 3 5% 5% 6% 7% 47%	1931
October	1st to 10th	Day	10% 5% 3 7% 6% 4 5% 6% 7% 7% 41%	1800
	11th to 20th	Day	9% 7% 3 7% 6% 4 5% 5% 8% 8% 38%	1800
	21st to end	Day	14% 10% 3 7% 6% 4 8% 5% 5% 7% 31%	1805
November	1st to 10th	Day	14% 12% 4 7% 7% 5% 5% 6% 9% 8% 24%	1595
	11th to 20th	Day	11% 14% 5% 10% 9% 5% 7% 5% 5% 6% 23%	1520
	21st to end	Day	8% 13% 6% 10% 8% 5% 7% 6% 7% 7% 23%	1520
December	1st to 10th	Day	9% 12% 5% 8% 8% 6% 6% 6% 7% 9% 25%	1520
	11th to 20th	Day	9% 16% 6% 9% 7% 6% 7% 6% 6% 7% 21%	1925
	21st to end	Day	12% 16% 6% 13% 9% 5% 5% 4 5% 6% 20%	2794
January	1st to 10th	Night	11% 20% 7% 11% 8% 4 6% 5% 6% 6% 13%	4406
	11th to 20th	Night	12% 13% 8% 12% 7% 3 5% 4 6% 9% 22%	4382
	21st to end	Night	16% 23% 5% 8% 8% 4 5% 5% 6% 6% 15%	4862
February	1st to 10th	Night	7% 14% 6% 9% 8% 4 6% 8% 6% 9% 23%	2499
	11th to 20th	Night	7% 11% 4 7% 7% 3 6% 6% 8% 10% 31%	2402
	21st to end	Night	5% 14% 4 10% 8% 4 6% 8% 6% 8% 26%	1918
March	1st to 10th	Night	7% 12% 6% 8% 7% 5% 7% 6% 7% 10% 26%	2280
	11th to 20th	Night	6% 11% 5% 7% 6% 4 6% 6% 7% 8% 33%	2099
	21st to end	Night	6% 13% 4 8% 8% 5% 7% 7% 8% 9% 26%	2052
April	1st to 10th	Night	5% 9% 5% 8% 8% 5% 7% 6% 8% 10% 28%	1800
	11th to 20th	Night	5% 7% 4 6% 6% 3 7% 7% 8% 11% 36%	1779
	21st to end	Night	5% 7% 3 6% 6% 5% 6% 8% 9% 10% 35%	1560
May	1st to 10th	Night	4 4 3 8% 6% 4 6% 7% 8% 10% 41%	1440
	11th to 20th	Night	6% 5% 2 6% 5% 4 6% 7% 9% 12% 39%	1416
	21st to end	Night	7% 5% 2 6% 7% 5% 6% 7% 9% 12% 34%	1552
June	1st to 10th	Night	7% 5% 2 4 7% 4 6% 6% 9% 10% 40%	1440
	11th to 20th	Night	3 5% 2 6% 6% 5% 7% 8% 7% 10% 39%	1387
	21st to end	Night	3 2 2 3 5% 3 6% 6% 5% 9% 55%	1260
July	1st to 10th	Night	2 2 1 3 3 3 5% 6% 5% 8% 61%	1358
	11th to 20th	Night	1 1 3 3 3 3 3 4 8% 71%	1440
	21st to end	Night	1 1 1 2 1 3 3 4 7% 77%	1576
August	1st to 10th	Night	1 1 1 2 2 1 3 4 5% 8% 73%	1432
	11th to 20th	Night	1 2 1 2 3 1 3 2 5% 8% 72%	1552
	21st to end	Night	3 2 1 3 4 3 4 5% 6% 9% 61%	1944
September	1st to 10th	Night	3 2 2 3 3 3 4 4 6% 8% 63%	1800
	11th to 20th	Night	5% 4 1 5% 5% 3 5% 5% 6% 8% 52%	1800
	21st to end	Night	6% 5% 2 4 5% 3 4 5% 7% 10% 49%	2027
October	1st to 10th	Night	7% 6% 3 6% 6% 3 5% 5% 7% 9% 44%	2160
	11th to 20th	Night	10% 7% 3 4 6% 4 5% 7% 6% 8% 39%	2160
	21st to end	Night	13% 8% 3 6% 6% 3 5% 6% 8% 9% 34%	2550
November	1st to 10th	Night	13% 12% 4 6% 6% 4 6% 6% 8% 10% 25%	2481
	11th to 20th	Night	12% 13% 5% 8% 7% 4 5% 7% 8% 8% 22%	2660
	21st to end	Night	8% 13% 6% 11% 8% 4 6% 6% 6% 8% 24%	2660
December	1st to 10th	Night	8% 14% 7% 8% 8% 4 6% 7% 7% 8% 23%	2660
	11th to 20th	Night	11% 16% 5% 9% 10% 6% 7% 6% 6% 7% 18%	3280
	21st to end	Night	14% 16% 8% 13% 8% 4 6% 5% 6% 6% 15%	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	68% 7% 14% 9% 2	2539
	11th to 20th	Day	57% 6% 14% 16% 5% 2	2540
	21st to end	Day	68% 4 14% 10% 3	2794
February	1st to 10th	Day	55% 8% 18% 14% 4 1	1676
	11th to 20th	Day	51% 8% 18% 15% 8% 1	1674
	21st to end	Day	58% 5% 17% 15% 4 1	1536
March	1st to 10th	Day	55% 5% 18% 14% 7% 1	1900
	11th to 20th	Day	56% 5% 18% 17% 4	2021
	21st to end	Day	57% 7% 19% 14% 2	2304
April	1st to 10th	Day	54% 7% 19% 17% 4	2160
	11th to 20th	Day	47% 7% 20% 17% 8% 1	2132
	21st to end	Day	46% 5% 21% 19% 8% 1	2397
May	1st to 10th	Day	37% 5% 26% 24% 8% 1	2520
	11th to 20th	Day	43% 5% 23% 24% 6%	2480
	21st to end	Day	46% 6% 23% 20% 5%	2724
June	1st to 10th	Day	43% 5% 19% 22% 9% 2	2520
	11th to 20th	Day	38% 3 27% 24% 8%	2564
	21st to end	Day	29% 4 22% 26% 16% 2	2700
July	1st to 10th	Day	24% 4 18% 26% 21% 7%	2523
	11th to 20th	Day	18% 4 12% 27% 31% 8%	2445
	21st to end	Day	12% 3 9% 28% 37% 11%	2589
August	1st to 10th	Day	18% 3 15% 29% 26% 9%	2490
	11th to 20th	Day	16% 4 15% 33% 27% 5%	2346
	21st to end	Day	25% 4 14% 32% 21% 4	2412
September	1st to 10th	Day	21% 3 17% 30% 23% 7%	2160
	11th to 20th	Day	32% 4 17% 22% 19% 5%	2160
	21st to end	Day	36% 4 19% 24% 15% 4	1931
October	1st to 10th	Day	40% 3 17% 29% 10% 2	1800
	11th to 20th	Day	40% 4 20% 23% 12%	1800
	21st to end	Day	50% 4 15% 20% 10%	1805
November	1st to 10th	Day	52% 6% 18% 17% 7% 1	1595
	11th to 20th	Day	60% 8% 17% 10% 4 2	1520
	21st to end	Day	54% 9% 16% 13% 6% 1	1520
December	1st to 10th	Day	53% 8% 17% 17% 5%	1520
	11th to 20th	Day	57% 10% 18% 12% 2	1928
	21st to end	Day	65% 6% 12% 11% 6%	2794
January	1st to 10th	Night	66% 6% 14% 11% 4	4406
	11th to 20th	Night	59% 5% 13% 15% 7% 1	4420
	21st to end	Night	69% 5% 12% 10% 3	4862
February	1st to 10th	Night	54% 9% 18% 14% 4	2499
	11th to 20th	Night	45% 10% 22% 16% 6% 1	2404
	21st to end	Night	52% 8% 16% 17% 6%	1918
March	1st to 10th	Night	51% 6% 20% 17% 7%	2280
	11th to 20th	Night	44% 6% 25% 19% 5%	2100
	21st to end	Night	51% 9% 22% 16% 2	2052
April	1st to 10th	Night	48% 8% 19% 21% 4	1800
	11th to 20th	Night	36% 9% 27% 19% 9% 1	1779
	21st to end	Night	38% 7% 23% 23% 8%	1560
May	1st to 10th	Night	32% 5% 30% 24% 7% 1	1440
	11th to 20th	Night	35% 7% 26% 26% 6% 1	1416
	21st to end	Night	38% 9% 26% 22% 6%	1552
June	1st to 10th	Night	35% 6% 26% 22% 9% 1	1440
	11th to 20th	Night	34% 6% 32% 22% 7%	1387
	21st to end	Night	24% 5% 24% 31% 12% 3	1260
July	1st to 10th	Night	19% 6% 21% 33% 17% 4	1318
	11th to 20th	Night	14% 3 17% 35% 24% 6%	1392
	21st to end	Night	8% 2 14% 33% 34% 9%	1488
August	1st to 10th	Night	13% 4 17% 31% 28% 7%	1424
	11th to 20th	Night	13% 3 21% 35% 22% 5%	1552
	21st to end	Night	20% 4 18% 34% 20% 3	1944
September	1st to 10th	Night	18% 4 20% 31% 21% 5%	1800
	11th to 20th	Night	27% 5% 17% 26% 21% 4	1800
	21st to end	Night	29% 5% 21% 27% 14% 4	2027
October	1st to 10th	Night	35% 4 18% 29% 12% 1	2160
	11th to 20th	Night	40% 4 20% 23% 12%	2160
	21st to end	Night	44% 5% 18% 22% 11%	2550
November	1st to 10th	Night	52% 8% 17% 17% 6%	2481
	11th to 20th	Night	54% 8% 19% 13% 4 2	2660
	21st to end	Night	54% 8% 18% 12% 6% 2	2660
December	1st to 10th	Night	56% 9% 14% 16% 5%	2660
	11th to 20th	Night	61% 7% 19% 10% 3	3276
	21st to end	Night	68% 5% 13% 12% 3	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	23% 13% 23% 23% 16% 2	180
	11th to 20th	Day	21% 7% 29% 26% 15% 2	180
	21st to end	Day	25% 12% 29% 23% 11% 2	198
February	1st to 10th	Day	25% 24% 29% 17% 4	336
	11th to 20th	Day	28% 19% 30% 17% 4 1	365
	21st to end	Day	19% 27% 31% 16% 7% 1	366
March	1st to 10th	Day	18% 28% 30% 17% 5% 1	460
	11th to 20th	Day	20% 22% 28% 20% 9% 1	449
	21st to end	Day	23% 29% 29% 14% 5%	462
April	1st to 10th	Day	24% 24% 32% 15% 4 2	420
	11th to 20th	Day	20% 28% 32% 15% 4 1	412
	21st to end	Day	20% 28% 32% 14% 6% 1	420
May	1st to 10th	Day	14% 23% 35% 22% 5%	423
	11th to 20th	Day	22% 15% 30% 23% 8% 2	448
	21st to end	Day	12% 21% 32% 24% 9% 1	485
June	1st to 10th	Day	15% 24% 32% 20% 8%	450
	11th to 20th	Day	15% 28% 39% 13% 4 1	494
	21st to end	Day	7% 23% 38% 23% 9% 1	630
July	1st to 10th	Day	4 19% 45% 25% 6%	518
	11th to 20th	Day	7% 19% 39% 23% 10% 1	444
	21st to end	Day	5% 13% 41% 28% 11% 2	487
August	1st to 10th	Day	7% 13% 36% 31% 11% 2	447
	11th to 20th	Day	5% 10% 35% 34% 13% 3	437
	21st to end	Day	8% 18% 37% 23% 12% 3	495
September	1st to 10th	Day	8% 21% 37% 24% 8% 2	450
	11th to 20th	Day	8% 20% 39% 24% 9% 1	450
	21st to end	Day	14% 21% 30% 24% 9% 2	450
October	1st to 10th	Day	16% 17% 27% 23% 13% 3	450
	11th to 20th	Day	17% 18% 30% 20% 11% 4	450
	21st to end	Day	25% 15% 27% 21% 9% 3	320
November	1st to 10th	Day	22% 19% 29% 24% 6% 1	232
	11th to 20th	Day	23% 16% 26% 20% 11% 5%	180
	21st to end	Day	14% 13% 31% 23% 14% 6%	180
December	1st to 10th	Day	24% 9% 25% 20% 17% 4	180
	11th to 20th	Day	16% 13% 36% 23% 10% 3	180
	21st to end	Day	18% 12% 30% 26% 13% 1	198
January	1st to 10th	Night	27% 11% 29% 22% 11% 1	760
	11th to 20th	Night	20% 11% 32% 25% 11% 1	760
	21st to end	Night	19% 9% 29% 30% 11% 1	836
February	1st to 10th	Night	19% 13% 35% 25% 7% 1	760
	11th to 20th	Night	16% 14% 32% 28% 8% 1	744
	21st to end	Night	22% 11% 30% 24% 12%	628
March	1st to 10th	Night	14% 13% 32% 31% 9% 1	760
	11th to 20th	Night	13% 13% 36% 26% 11% 1	752
	21st to end	Night	17% 18% 39% 20% 6% 1	792
April	1st to 10th	Night	12% 16% 37% 25% 8% 1	720
	11th to 20th	Night	11% 18% 35% 26% 8% 1	711
	21st to end	Night	9% 23% 38% 23% 8%	480
May	1st to 10th	Night	9% 18% 32% 30% 9% 1	360
	11th to 20th	Night	9% 11% 36% 30% 12% 1	354
	21st to end	Night	9% 9% 41% 29% 12%	389
June	1st to 10th	Night	11% 14% 40% 25% 9%	360
	11th to 20th	Night	9% 23% 41% 21% 6%	360
	21st to end	Night	5% 17% 36% 31% 11% 1	360
July	1st to 10th	Night	4 10% 42% 35% 9%	350
	11th to 20th	Night	2 17% 43% 31% 6% 1	348
	21st to end	Night	2 14% 38% 34% 12% 1	394
August	1st to 10th	Night	3 11% 36% 31% 18% 1	358
	11th to 20th	Night	4 8% 32% 35% 19% 2	484
	21st to end	Night	5% 14% 35% 31% 13% 2	756
September	1st to 10th	Night	4 14% 34% 29% 16% 2	720
	11th to 20th	Night	8% 9% 28% 30% 22% 3	720
	21st to end	Night	10% 13% 30% 28% 17% 3	720
October	1st to 10th	Night	12% 9% 31% 28% 19% 1	720
	11th to 20th	Night	16% 11% 28% 27% 16% 2	720
	21st to end	Night	21% 11% 31% 24% 10% 2	792
November	1st to 10th	Night	19% 10% 38% 27% 6%	740
	11th to 20th	Night	26% 9% 32% 21% 11% 2	760
	21st to end	Night	17% 10% 35% 22% 13% 3	760
December	1st to 10th	Night	19% 10% 31% 28% 11% 1	760
	11th to 20th	Night	19% 7% 41% 25% 7% 1	760
	21st to end	Night	21% 11% 36% 26% 5% 1	836

Page generated at 2024-03-15 11:01:44. Version ac07

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