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 2024-11-25.

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% 2 6% 4 4 5% 4 6% 8% 51%	105493
	Night	4 8% 3 6% 5% 4 5% 4 6% 8% 48%	102596
Transparency	Day	30% 8% 13% 23% 17% 8%	105262
	Night	33% 9% 15% 24% 14% 5%	102473
Seeing	Day	9% 13% 28% 31% 16% 4	14397
	Night	9% 8% 25% 37% 19% 2	23395

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	6% 17% 6% 10% 6% 5% 6% 5% 7% 6% 24%	2539
	11th to 20th	Day	5% 18% 5% 11% 6% 5% 4 5% 6% 7% 27%	2516
	21st to end	Day	9% 19% 6% 12% 7% 6% 6% 6% 8% 6% 17%	2794
February	1st to 10th	Day	5% 11% 5% 9% 6% 6% 6% 6% 7% 9% 31%	1668
	11th to 20th	Day	4 10% 4 7% 6% 5% 6% 5% 7% 10% 36%	1665
	21st to end	Day	3 9% 5% 9% 6% 5% 7% 6% 8% 9% 34%	1563
March	1st to 10th	Day	2 7% 2 7% 5% 7% 7% 6% 9% 10% 39%	3138
	11th to 20th	Day	2 5% 2 6% 4 4 4 4 6% 8% 54%	3395
	21st to end	Day	6% 8% 3 7% 6% 7% 7% 6% 8% 9% 34%	4071
April	1st to 10th	Day	5% 8% 2 8% 6% 6% 7% 6% 8% 9% 35%	2280
	11th to 20th	Day	3 8% 2 6% 5% 6% 5% 5% 8% 8% 43%	2252
	21st to end	Day	4 5% 2 6% 6% 6% 6% 5% 7% 10% 44%	2507
May	1st to 10th	Day	6% 4 2 5% 4 3 4 3 6% 8% 56%	4420
	11th to 20th	Day	4 3 1 4 4 3 4 4 5% 8% 59%	4377
	21st to end	Day	7% 7% 3 8% 5% 6% 5% 5% 8% 8% 37%	4813
June	1st to 10th	Day	7% 5% 2 5% 5% 5% 5% 5% 7% 8% 45%	2660
	11th to 20th	Day	3 4 2 5% 4 5% 5% 4 7% 8% 51%	2660
	21st to end	Day	2 3 2 5% 3 4 4 3 6% 7% 61%	2660
July	1st to 10th	Day	1 1 1 1 2 2 2 2 3 4 80%	4420
	11th to 20th	Day	1 2 1 2 2 2 2 2 3 4 80%	4420
	21st to end	Day	1 1 2 1 2 2 2 4 5% 80%	4790
August	1st to 10th	Day	1 1 2 2 3 3 3 4 6% 75%	4401
	11th to 20th	Day	1 1 1 2 2 2 3 3 6% 10% 69%	4123
	21st to end	Day	2 3 1 4 3 3 4 4 5% 6% 64%	4190
September	1st to 10th	Day	2 2 1 2 3 3 3 2 5% 7% 71%	2280
	11th to 20th	Day	3 3 1 4 4 5% 5% 5% 7% 9% 55%	2280
	21st to end	Day	4 3 1 4 3 4 5% 3 5% 8% 59%	2047
October	1st to 10th	Day	3 3 1 3 2 3 4 3 5% 8% 64%	3180
	11th to 20th	Day	3 3 1 5% 4 4 6% 5% 8% 11% 50%	3161
	21st to end	Day	4 5% 1 5% 4 5% 6% 5% 8% 9% 49%	3113
November	1st to 10th	Day	5% 9% 3 6% 6% 7% 7% 6% 7% 9% 35%	1719
	11th to 20th	Day	3 10% 3 9% 8% 7% 7% 5% 8% 8% 33%	1600
	21st to end	Day	5% 11% 3 8% 5% 7% 6% 6% 8% 10% 32%	1552
December	1st to 10th	Day	4 12% 4 10% 7% 6% 4 6% 8% 7% 31%	1520
	11th to 20th	Day	5% 13% 5% 13% 7% 7% 7% 4 9% 8% 21%	1925
	21st to end	Day	5% 15% 9% 15% 7% 6% 5% 5% 5% 5% 22%	2794
January	1st to 10th	Night	5% 17% 6% 12% 6% 5% 6% 5% 7% 8% 23%	4406
	11th to 20th	Night	7% 15% 6% 10% 6% 5% 5% 4 6% 8% 28%	4382
	21st to end	Night	5% 20% 7% 16% 10% 6% 5% 4 6% 5% 16%	4862
February	1st to 10th	Night	4 14% 4 9% 6% 7% 5% 5% 8% 8% 30%	2508
	11th to 20th	Night	5% 8% 4 7% 6% 6% 6% 4 6% 9% 39%	2402
	21st to end	Night	4 11% 4 10% 7% 4 5% 5% 7% 8% 35%	1890
March	1st to 10th	Night	3 8% 2 5% 4 4 6% 5% 9% 12% 42%	3736
	11th to 20th	Night	1 4 2 5% 4 3 4 4 6% 8% 60%	3582
	21st to end	Night	5% 6% 3 7% 6% 6% 7% 5% 9% 10% 36%	3581
April	1st to 10th	Night	4 6% 2 7% 6% 5% 6% 5% 8% 10% 43%	1900
	11th to 20th	Night	3 7% 2 5% 5% 6% 5% 4 6% 7% 52%	1879
	21st to end	Night	5% 5% 3 3 5% 4 4 4 6% 11% 51%	1670
May	1st to 10th	Night	4 4 2 5% 4 3 4 4 6% 7% 60%	2540
	11th to 20th	Night	4 4 1 4 3 3 4 3 5% 7% 63%	2516
	21st to end	Night	3 2 1 3 3 4 4 5% 8% 11% 54%	2762
June	1st to 10th	Night	5% 6% 2 3 3 4 5% 4 8% 8% 52%	1520
	11th to 20th	Night	4 3 1 4 4 5% 5% 5% 7% 8% 56%	1520
	21st to end	Night	1 2 1 3 4 4 3 4 6% 6% 67%	1520
July	1st to 10th	Night	1 1 1 2 1 1 1 2 3 4 83%	2540
	11th to 20th	Night	1 1 1 1 2 2 3 3 86%	2540
	21st to end	Night	1 1 1 1 1 2 2 3 5% 85%	2762
August	1st to 10th	Night	1 1 1 2 1 3 3 2 4 7% 76%	2529
	11th to 20th	Night	2 1 2 2 2 3 3 4 6% 75%	2710
	21st to end	Night	3 2 1 2 2 2 3 4 6% 6% 69%	3487
September	1st to 10th	Night	2 2 1 2 2 2 3 2 5% 9% 71%	1900
	11th to 20th	Night	3 2 1 4 4 3 4 3 5% 7% 62%	1900
	21st to end	Night	3 3 1 3 3 3 4 4 7% 9% 61%	2131
October	1st to 10th	Night	3 3 2 3 3 3 3 3 6% 9% 62%	3800
	11th to 20th	Night	3 3 1 4 4 3 5% 4 7% 10% 56%	3777
	21st to end	Night	5% 5% 2 6% 4 5% 5% 5% 6% 8% 49%	4444
November	1st to 10th	Night	7% 9% 2 6% 5% 5% 6% 5% 8% 9% 38%	2576
	11th to 20th	Night	5% 10% 3 8% 6% 6% 7% 5% 7% 8% 36%	2800
	21st to end	Night	4 12% 5% 9% 7% 6% 6% 5% 6% 7% 34%	2722
December	1st to 10th	Night	5% 13% 4 11% 7% 6% 5% 5% 7% 8% 30%	2660
	11th to 20th	Night	5% 14% 5% 14% 7% 6% 7% 5% 7% 10% 20%	3280
	21st to end	Night	6% 18% 8% 11% 5% 5% 6% 4 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	58% 14% 11% 11% 6% 1	2539
	11th to 20th	Day	55% 10% 16% 16% 3	2540
	21st to end	Day	66% 14% 9% 9% 3	2794
February	1st to 10th	Day	49% 13% 17% 16% 4 1	1668
	11th to 20th	Day	42% 14% 17% 18% 8% 1	1674
	21st to end	Day	40% 14% 20% 18% 7% 1	1563
March	1st to 10th	Day	33% 12% 16% 22% 15% 1	3138
	11th to 20th	Day	27% 7% 13% 45% 7% 1	3395
	21st to end	Day	41% 13% 19% 19% 8%	4071
April	1st to 10th	Day	42% 11% 16% 22% 9% 1	2280
	11th to 20th	Day	37% 8% 16% 22% 14% 3	2252
	21st to end	Day	35% 10% 15% 24% 14% 3	2507
May	1st to 10th	Day	26% 7% 12% 23% 24% 9%	4420
	11th to 20th	Day	21% 6% 14% 33% 22% 3	4380
	21st to end	Day	37% 11% 16% 28% 7%	4814
June	1st to 10th	Day	36% 7% 13% 25% 15% 4	2660
	11th to 20th	Day	28% 6% 15% 28% 18% 4	2660
	21st to end	Day	22% 4 13% 31% 23% 7%	2660
July	1st to 10th	Day	10% 3 6% 15% 27% 39%	4351
	11th to 20th	Day	11% 2 5% 11% 24% 47%	4345
	21st to end	Day	9% 2 5% 21% 36% 26%	4639
August	1st to 10th	Day	12% 3 7% 19% 38% 22%	4384
	11th to 20th	Day	11% 4 12% 42% 26% 5%	4165
	21st to end	Day	21% 6% 12% 27% 29% 6%	4189
September	1st to 10th	Day	15% 4 10% 29% 31% 10%	2280
	11th to 20th	Day	25% 9% 14% 22% 24% 7%	2280
	21st to end	Day	25% 7% 17% 29% 18% 5%	2047
October	1st to 10th	Day	19% 5% 14% 39% 21% 2	3180
	11th to 20th	Day	26% 11% 20% 24% 18% 1	3161
	21st to end	Day	28% 9% 17% 26% 14% 6%	3113
November	1st to 10th	Day	43% 12% 16% 19% 10% 1	1719
	11th to 20th	Day	45% 15% 17% 16% 6% 1	1600
	21st to end	Day	44% 16% 18% 14% 7% 2	1552
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	55% 14% 14% 11% 5%	4406
	11th to 20th	Night	51% 10% 15% 19% 6%	4420
	21st to end	Night	67% 12% 10% 9% 2 1	4862
February	1st to 10th	Night	47% 14% 17% 17% 4 1	2508
	11th to 20th	Night	40% 11% 20% 19% 8% 1	2404
	21st to end	Night	43% 11% 16% 19% 10%	1890
March	1st to 10th	Night	32% 11% 17% 23% 14% 4	3736
	11th to 20th	Night	23% 7% 17% 43% 9%	3583
	21st to end	Night	37% 14% 21% 24% 4	3581
April	1st to 10th	Night	35% 9% 20% 25% 10% 1	1900
	11th to 20th	Night	31% 9% 17% 24% 17% 2	1879
	21st to end	Night	29% 10% 15% 29% 16% 1	1670
May	1st to 10th	Night	24% 6% 10% 26% 28% 5%	2540
	11th to 20th	Night	19% 6% 15% 33% 24% 2	2516
	21st to end	Night	21% 10% 23% 37% 9% 1	2762
June	1st to 10th	Night	28% 9% 15% 26% 18% 4	1520
	11th to 20th	Night	25% 8% 14% 33% 17% 2	1520
	21st to end	Night	18% 6% 12% 36% 23% 6%	1520
July	1st to 10th	Night	8% 2 7% 18% 25% 39%	2500
	11th to 20th	Night	6% 2 5% 14% 27% 46%	2492
	21st to end	Night	6% 2 6% 23% 35% 29%	2674
August	1st to 10th	Night	11% 2 7% 19% 40% 22%	2521
	11th to 20th	Night	11% 4 17% 39% 22% 7%	2734
	21st to end	Night	14% 6% 14% 28% 31% 7%	3487
September	1st to 10th	Night	14% 5% 12% 27% 32% 11%	1900
	11th to 20th	Night	21% 7% 11% 27% 25% 9%	1900
	21st to end	Night	20% 8% 15% 33% 17% 7%	2131
October	1st to 10th	Night	19% 5% 12% 47% 16% 1	3800
	11th to 20th	Night	23% 10% 18% 31% 17% 1	3777
	21st to end	Night	30% 10% 16% 27% 15% 2	4444
November	1st to 10th	Night	40% 12% 18% 20% 10% 1	2576
	11th to 20th	Night	42% 12% 18% 19% 7% 1	2800
	21st to end	Night	46% 12% 17% 16% 8% 1	2722
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	16% 13% 23% 29% 13% 5%	180
	21st to end	Day	13% 12% 20% 34% 17% 4	198
February	1st to 10th	Day	12% 10% 37% 32% 8% 1	328
	11th to 20th	Day	12% 14% 36% 28% 8% 1	365
	21st to end	Day	8% 17% 36% 27% 10% 2	379
March	1st to 10th	Day	12% 15% 32% 27% 12% 2	460
	11th to 20th	Day	11% 17% 23% 30% 17% 2	460
	21st to end	Day	12% 19% 33% 25% 10%	506
April	1st to 10th	Day	16% 19% 29% 24% 10% 2	460
	11th to 20th	Day	10% 22% 33% 23% 10% 3	452
	21st to end	Day	13% 18% 30% 23% 13% 3	460
May	1st to 10th	Day	11% 14% 33% 30% 10% 2	463
	11th to 20th	Day	15% 14% 27% 27% 13% 5%	488
	21st to end	Day	12% 12% 26% 31% 15% 5%	529
June	1st to 10th	Day	11% 16% 29% 27% 16% 2	490
	11th to 20th	Day	11% 18% 34% 25% 11% 1	490
	21st to end	Day	5% 12% 28% 29% 21% 4	490
July	1st to 10th	Day	5% 9% 24% 43% 17% 2	486
	11th to 20th	Day	2 12% 28% 33% 20% 5%	484
	21st to end	Day	2 8% 24% 37% 23% 6%	531
August	1st to 10th	Day	5% 6% 23% 34% 24% 7%	487
	11th to 20th	Day	2 6% 20% 39% 24% 10%	477
	21st to end	Day	5% 12% 25% 30% 20% 7%	539
September	1st to 10th	Day	3 9% 27% 33% 20% 7%	490
	11th to 20th	Day	7% 10% 27% 33% 20% 4	490
	21st to end	Day	10% 12% 24% 35% 16% 4	490
October	1st to 10th	Day	12% 11% 27% 28% 17% 6%	490
	11th to 20th	Day	11% 12% 25% 28% 19% 5%	490
	21st to end	Day	13% 11% 25% 34% 14% 2	342
November	1st to 10th	Day	13% 14% 22% 34% 16% 1	277
	11th to 20th	Day	12% 14% 28% 24% 16% 7%	200
	21st to end	Day	5% 11% 28% 32% 20% 3	188
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	760
	21st to end	Night	14% 8% 21% 38% 16% 3	836
February	1st to 10th	Night	14% 9% 29% 35% 13% 1	760
	11th to 20th	Night	11% 8% 26% 36% 16% 2	744
	21st to end	Night	12% 11% 26% 34% 16% 2	628
March	1st to 10th	Night	13% 8% 25% 37% 17% 1	760
	11th to 20th	Night	8% 8% 27% 35% 21% 1	760
	21st to end	Night	9% 11% 28% 38% 13% 1	836
April	1st to 10th	Night	8% 11% 26% 35% 18% 2	760
	11th to 20th	Night	7% 14% 29% 33% 15% 2	751
	21st to end	Night	7% 9% 33% 35% 15% 1	530
May	1st to 10th	Night	5% 7% 34% 35% 17% 2	380
	11th to 20th	Night	9% 5% 20% 40% 25% 2	374
	21st to end	Night	7% 6% 22% 39% 23% 3	411
June	1st to 10th	Night	8% 6% 27% 39% 18% 2	380
	11th to 20th	Night	5% 10% 31% 39% 14% 1	380
	21st to end	Night	2 8% 28% 36% 26% 1	380
July	1st to 10th	Night	2 4 25% 45% 24% 1	370
	11th to 20th	Night	1 5% 30% 41% 21% 2	368
	21st to end	Night	1 5% 19% 46% 27% 1	416
August	1st to 10th	Night	2 2 17% 40% 36% 3	378
	11th to 20th	Night	2 2 17% 37% 37% 5%	498
	21st to end	Night	3 6% 20% 40% 26% 4	825
September	1st to 10th	Night	4 3 19% 40% 29% 4	760
	11th to 20th	Night	5% 5% 19% 33% 31% 8%	760
	21st to end	Night	5% 5% 20% 39% 26% 5%	760
October	1st to 10th	Night	9% 7% 19% 37% 26% 2	760
	11th to 20th	Night	5% 8% 22% 37% 23% 4	760
	21st to end	Night	11% 8% 23% 39% 14% 4	836
November	1st to 10th	Night	13% 8% 23% 43% 13%	780
	11th to 20th	Night	13% 10% 27% 33% 15% 2	800
	21st to end	Night	12% 7% 27% 34% 17% 3	778
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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