Redmond
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Redmond clear sky chart from 2005-11-06 to 2026-09-29.

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	6% 6% 2 6% 4 4 4 3 5% 7% 54%	158618
	Night	7% 7% 3 6% 4 4 4 4 5% 6% 49%	150159
Transparency	Day	31% 3 9% 24% 22% 11%	153414
	Night	35% 3 12% 25% 18% 6%	146361
Seeing	Day	11% 11% 23% 26% 20% 8%	17054
	Night	12% 6% 21% 39% 20% 2	26032

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	10% 14% 4 12% 8% 7% 7% 5% 6% 7% 21%	4722
	11th to 20th	Day	10% 9% 2 5% 4 4 4 3 4 5% 50%	4740
	21st to end	Day	8% 10% 3 8% 5% 4 5% 4 7% 8% 37%	5561
February	1st to 10th	Day	8% 12% 4 8% 6% 6% 5% 5% 6% 8% 33%	1890
	11th to 20th	Day	8% 12% 4 9% 5% 6% 5% 4 7% 8% 33%	1856
	21st to end	Day	7% 12% 4 10% 6% 5% 5% 5% 7% 8% 31%	1730
March	1st to 10th	Day	6% 10% 4 9% 5% 5% 5% 4 6% 10% 34%	4652
	11th to 20th	Day	7% 14% 4 9% 6% 5% 4 4 5% 6% 37%	5110
	21st to end	Day	8% 12% 4 11% 7% 6% 6% 5% 6% 8% 27%	5868
April	1st to 10th	Day	8% 11% 4 9% 6% 6% 6% 4 6% 8% 32%	2520
	11th to 20th	Day	8% 10% 3 8% 6% 4 4 4 5% 7% 39%	2489
	21st to end	Day	7% 7% 3 6% 4 5% 4 4 7% 7% 46%	2583
May	1st to 10th	Day	7% 5% 2 5% 3 3 4 4 5% 6% 56%	8195
	11th to 20th	Day	5% 4 2 5% 3 4 4 3 6% 7% 56%	8160
	21st to end	Day	6% 5% 2 5% 3 4 4 4 6% 8% 54%	8992
June	1st to 10th	Day	9% 7% 3 5% 5% 5% 4 4 6% 6% 47%	2940
	11th to 20th	Day	5% 5% 2 5% 3 4 4 4 5% 6% 56%	2940
	21st to end	Day	4 3 1 3 3 2 3 3 5% 6% 66%	2940
July	1st to 10th	Day	1 1 1 2 1 2 2 2 3 4 80%	8219
	11th to 20th	Day	2 1 1 3 2 2 2 2 3 4 79%	8220
	21st to end	Day	1 1 1 2 2 2 2 2 3 4 80%	8922
August	1st to 10th	Day	2 1 1 2 2 2 2 3 4 6% 76%	7777
	11th to 20th	Day	2 2 1 3 2 2 2 2 4 6% 74%	7507
	21st to end	Day	4 3 1 3 2 2 3 2 4 7% 68%	7750
September	1st to 10th	Day	2 2 1 3 2 2 3 2 3 5% 73%	2520
	11th to 20th	Day	4 3 1 5% 3 4 3 4 5% 6% 61%	2520
	21st to end	Day	7% 6% 1 5% 3 3 4 3 4 5% 60%	2232
October	1st to 10th	Day	5% 4 1 5% 3 3 3 2 3 5% 65%	3280
	11th to 20th	Day	6% 5% 2 5% 4 5% 5% 4 6% 10% 49%	3261
	21st to end	Day	10% 8% 3 7% 5% 6% 5% 4 6% 6% 40%	3382
November	1st to 10th	Day	11% 10% 3 8% 5% 5% 5% 4 6% 8% 35%	1854
	11th to 20th	Day	10% 11% 4 9% 7% 6% 6% 5% 7% 7% 29%	1706
	21st to end	Day	8% 10% 3 9% 5% 4 5% 6% 6% 8% 36%	1680
December	1st to 10th	Day	8% 7% 3 5% 4 3 3 3 5% 8% 50%	2700
	11th to 20th	Day	10% 13% 4 10% 6% 6% 6% 5% 6% 7% 24%	3108
	21st to end	Day	8% 14% 5% 11% 7% 7% 6% 5% 7% 7% 24%	4092
January	1st to 10th	Night	11% 13% 5% 12% 7% 7% 6% 5% 7% 7% 19%	8172
	11th to 20th	Night	8% 9% 3 6% 4 4 4 3 4 6% 50%	8220
	21st to end	Night	8% 10% 3 9% 7% 5% 6% 4 5% 6% 37%	8626
February	1st to 10th	Night	8% 13% 4 9% 5% 5% 5% 5% 6% 7% 31%	2730
	11th to 20th	Night	8% 12% 4 8% 5% 5% 5% 4 5% 7% 36%	2651
	21st to end	Night	7% 13% 4 9% 5% 5% 6% 5% 7% 8% 31%	2076
March	1st to 10th	Night	6% 10% 3 8% 5% 5% 6% 5% 7% 9% 35%	5456
	11th to 20th	Night	6% 10% 2 8% 4 5% 5% 4 6% 8% 42%	5110
	21st to end	Night	8% 10% 4 10% 7% 6% 6% 5% 7% 8% 26%	5347
April	1st to 10th	Night	9% 13% 3 6% 4 4 4 5% 7% 7% 37%	2100
	11th to 20th	Night	9% 13% 3 8% 5% 4 5% 3 6% 6% 39%	2079
	21st to end	Night	8% 8% 3 6% 4 5% 5% 4 6% 8% 43%	2032
May	1st to 10th	Night	7% 6% 2 5% 3 3 3 3 5% 6% 57%	4723
	11th to 20th	Night	4 5% 2 6% 5% 4 4 3 6% 7% 55%	4700
	21st to end	Night	7% 6% 2 4 3 3 3 2 5% 8% 57%	5181
June	1st to 10th	Night	11% 7% 1 6% 4 4 3 3 5% 6% 49%	1680
	11th to 20th	Night	5% 5% 1 4 3 3 2 3 5% 8% 58%	1680
	21st to end	Night	4 4 1 3 1 3 3 3 4 6% 68%	1680
July	1st to 10th	Night	1 1 1 2 2 2 2 2 3 4 81%	4740
	11th to 20th	Night	2 2 1 2 2 2 2 2 2 3 79%	4740
	21st to end	Night	1 1 1 2 2 2 2 2 3 4 78%	5153
August	1st to 10th	Night	1 2 1 3 2 3 3 3 4 5% 73%	5030
	11th to 20th	Night	1 1 1 3 2 3 3 3 4 6% 74%	5349
	21st to end	Night	3 3 1 4 2 2 2 2 4 5% 72%	6499
September	1st to 10th	Night	2 2 1 3 2 2 3 2 4 5% 74%	2100
	11th to 20th	Night	4 4 1 5% 3 3 3 3 5% 6% 62%	2100
	21st to end	Night	6% 4 1 4 2 3 4 3 5% 6% 62%	2341
October	1st to 10th	Night	6% 4 2 3 2 2 3 2 3 5% 69%	3920
	11th to 20th	Night	7% 5% 2 6% 4 4 4 3 6% 9% 51%	3897
	21st to end	Night	8% 7% 3 7% 5% 6% 5% 5% 6% 7% 42%	4410
November	1st to 10th	Night	12% 10% 4 8% 5% 4 5% 5% 5% 7% 35%	2665
	11th to 20th	Night	12% 11% 3 10% 6% 5% 5% 5% 6% 7% 31%	2910
	21st to end	Night	9% 9% 3 7% 5% 4 5% 5% 6% 8% 40%	2940
December	1st to 10th	Night	6% 7% 2 5% 3 3 3 3 4 7% 55%	4700
	11th to 20th	Night	10% 13% 5% 12% 7% 6% 6% 5% 6% 7% 23%	5316
	21st to end	Night	10% 14% 4 10% 6% 6% 6% 4 6% 7% 28%	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	60% 4 14% 17% 5%	4723
	11th to 20th	Day	37% 2 9% 24% 23% 6%	4740
	21st to end	Day	42% 4 11% 19% 19% 5%	5561
February	1st to 10th	Day	48% 4 15% 24% 10% 1	1890
	11th to 20th	Day	47% 4 14% 22% 11% 1	1865
	21st to end	Day	49% 5% 15% 18% 11% 2	1730
March	1st to 10th	Day	46% 2 8% 26% 15% 3	4652
	11th to 20th	Day	47% 3 11% 25% 14% 1	5110
	21st to end	Day	53% 4 12% 24% 7% 1	5868
April	1st to 10th	Day	49% 3 12% 22% 13% 2	2520
	11th to 20th	Day	46% 3 12% 21% 16% 3	2492
	21st to end	Day	38% 3 12% 29% 15% 3	2583
May	1st to 10th	Day	29% 3 7% 28% 30% 4	8195
	11th to 20th	Day	26% 4 13% 30% 25% 3	8163
	21st to end	Day	28% 3 15% 33% 20% 1	8994
June	1st to 10th	Day	38% 2 9% 30% 18% 3	2940
	11th to 20th	Day	29% 3 9% 31% 24% 5%	2940
	21st to end	Day	20% 2 9% 29% 29% 10%	2940
July	1st to 10th	Day	10% 2 4 20% 32% 33%	8151
	11th to 20th	Day	12% 2 3 9% 25% 49%	8145
	21st to end	Day	10% 2 3 24% 39% 21%	8723
August	1st to 10th	Day	11% 2 3 13% 34% 38%	6159
	11th to 20th	Day	13% 2 7% 31% 33% 13%	5918
	21st to end	Day	15% 2 4 28% 36% 16%	6077
September	1st to 10th	Day	15% 2 5% 25% 32% 21%	2520
	11th to 20th	Day	24% 3 8% 27% 26% 12%	2520
	21st to end	Day	27% 2 8% 27% 24% 11%	2232
October	1st to 10th	Day	25% 2 9% 23% 25% 16%	3280
	11th to 20th	Day	31% 4 17% 27% 19% 3	3261
	21st to end	Day	42% 4 10% 26% 17% 2	3382
November	1st to 10th	Day	47% 3 13% 25% 12% 1	1854
	11th to 20th	Day	50% 4 18% 19% 9%	1706
	21st to end	Day	43% 5% 16% 21% 14% 1	1680
December	1st to 10th	Day	33% 3 13% 29% 21% 1	2700
	11th to 20th	Day	57% 4 17% 18% 5%	3108
	21st to end	Day	56% 4 14% 20% 5% 1	4092
January	1st to 10th	Night	60% 5% 16% 15% 4	8172
	11th to 20th	Night	37% 2 7% 26% 21% 6%	8220
	21st to end	Night	48% 3 9% 17% 18% 5%	8626
February	1st to 10th	Night	51% 4 16% 19% 9%	2730
	11th to 20th	Night	46% 5% 16% 21% 10% 1	2653
	21st to end	Night	50% 5% 12% 22% 9% 1	2076
March	1st to 10th	Night	43% 4 10% 27% 15% 2	5456
	11th to 20th	Night	37% 5% 14% 32% 11%	5110
	21st to end	Night	53% 6% 15% 20% 6%	5347
April	1st to 10th	Night	46% 3 18% 23% 9% 1	2100
	11th to 20th	Night	46% 4 14% 22% 13% 2	2079
	21st to end	Night	39% 5% 14% 27% 13% 2	2032
May	1st to 10th	Night	29% 2 8% 31% 28% 1	4721
	11th to 20th	Night	29% 4 16% 35% 15% 1	4700
	21st to end	Night	28% 3 23% 32% 13%	5182
June	1st to 10th	Night	37% 4 12% 32% 14% 2	1680
	11th to 20th	Night	25% 3 13% 38% 18% 3	1680
	21st to end	Night	19% 2 11% 34% 25% 8%	1680
July	1st to 10th	Night	11% 1 5% 28% 29% 25%	4700
	11th to 20th	Night	13% 1 4 13% 26% 42%	4692
	21st to end	Night	13% 2 3 29% 38% 16%	5040
August	1st to 10th	Night	11% 1 3 14% 40% 29%	3975
	11th to 20th	Night	13% 3 10% 34% 33% 7%	4213
	21st to end	Night	14% 2 6% 30% 37% 10%	5092
September	1st to 10th	Night	14% 2 6% 28% 34% 16%	2100
	11th to 20th	Night	24% 3 9% 27% 26% 11%	2100
	21st to end	Night	24% 2 8% 29% 25% 12%	2341
October	1st to 10th	Night	21% 3 8% 26% 34% 9%	3920
	11th to 20th	Night	30% 4 20% 25% 18% 3	3897
	21st to end	Night	39% 5% 11% 30% 14% 1	4410
November	1st to 10th	Night	48% 4 13% 22% 13% 2	2665
	11th to 20th	Night	50% 5% 15% 23% 7%	2910
	21st to end	Night	41% 4 16% 23% 16% 1	2940
December	1st to 10th	Night	29% 4 12% 32% 22% 1	4700
	11th to 20th	Night	59% 4 15% 17% 5%	5316
	21st to end	Night	54% 5% 16% 19% 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	21% 14% 34% 21% 10% 1	220
	11th to 20th	Day	17% 9% 26% 29% 14% 5%	220
	21st to end	Day	15% 11% 26% 26% 18% 3	372
February	1st to 10th	Day	18% 15% 23% 29% 13% 1	430
	11th to 20th	Day	17% 18% 28% 23% 13% 2	431
	21st to end	Day	21% 15% 29% 24% 10% 1	446
March	1st to 10th	Day	18% 19% 24% 31% 8% 1	540
	11th to 20th	Day	16% 17% 25% 26% 13% 3	540
	21st to end	Day	19% 19% 23% 25% 13% 1	594
April	1st to 10th	Day	19% 15% 23% 23% 14% 7%	540
	11th to 20th	Day	14% 18% 24% 24% 13% 6%	532
	21st to end	Day	11% 17% 24% 25% 17% 6%	540
May	1st to 10th	Day	11% 13% 27% 23% 18% 8%	543
	11th to 20th	Day	18% 13% 21% 23% 17% 8%	568
	21st to end	Day	11% 10% 21% 24% 22% 12%	617
June	1st to 10th	Day	11% 12% 20% 23% 21% 13%	570
	11th to 20th	Day	9% 14% 24% 26% 21% 7%	570
	21st to end	Day	5% 8% 20% 27% 26% 13%	570
July	1st to 10th	Day	3 5% 24% 30% 26% 12%	566
	11th to 20th	Day	2 7% 26% 24% 29% 12%	564
	21st to end	Day	2 4 26% 27% 26% 16%	619
August	1st to 10th	Day	2 4 21% 30% 27% 17%	567
	11th to 20th	Day	2 4 18% 28% 28% 20%	557
	21st to end	Day	5% 7% 19% 27% 28% 15%	627
September	1st to 10th	Day	3 4 22% 27% 28% 16%	570
	11th to 20th	Day	5% 7% 19% 28% 29% 12%	570
	21st to end	Day	10% 7% 19% 26% 29% 9%	563
October	1st to 10th	Day	11% 10% 20% 26% 23% 9%	530
	11th to 20th	Day	14% 10% 19% 27% 24% 6%	530
	21st to end	Day	17% 11% 23% 25% 20% 5%	482
November	1st to 10th	Day	16% 11% 25% 33% 14% 2	330
	11th to 20th	Day	20% 14% 20% 27% 15% 5%	234
	21st to end	Day	15% 10% 25% 32% 16% 2	220
December	1st to 10th	Day	11% 16% 22% 29% 11% 10%	220
	11th to 20th	Day	18% 14% 34% 30% 5%	220
	21st to end	Day	18% 17% 27% 27% 9% 3	242
January	1st to 10th	Night	17% 10% 30% 29% 13% 2	840
	11th to 20th	Night	16% 8% 23% 31% 18% 3	840
	21st to end	Night	14% 7% 22% 38% 17% 2	924
February	1st to 10th	Night	15% 10% 27% 35% 13% 1	840
	11th to 20th	Night	14% 7% 26% 39% 13% 1	824
	21st to end	Night	15% 11% 28% 36% 10%	692
March	1st to 10th	Night	15% 12% 25% 36% 10% 1	840
	11th to 20th	Night	13% 8% 25% 38% 14% 1	840
	21st to end	Night	14% 10% 26% 35% 14% 1	924
April	1st to 10th	Night	16% 9% 21% 33% 20% 1	840
	11th to 20th	Night	15% 8% 26% 33% 16% 2	831
	21st to end	Night	11% 8% 24% 37% 18% 1	772
May	1st to 10th	Night	12% 5% 16% 44% 22% 1	420
	11th to 20th	Night	10% 5% 16% 43% 25%	414
	21st to end	Night	11% 5% 14% 42% 25% 3	455
June	1st to 10th	Night	13% 5% 18% 43% 20% 1	420
	11th to 20th	Night	7% 4 22% 47% 20%	420
	21st to end	Night	6% 2 14% 51% 26% 1	420
July	1st to 10th	Night	2 1 9% 55% 31%	410
	11th to 20th	Night	2 2 15% 58% 22% 1	408
	21st to end	Night	1 11% 54% 32% 2	460
August	1st to 10th	Night	2 1 6% 49% 39% 3	536
	11th to 20th	Night	2 6% 44% 41% 7%	642
	21st to end	Night	2 3 17% 45% 31% 3	924
September	1st to 10th	Night	3 2 15% 44% 31% 4	840
	11th to 20th	Night	6% 2 13% 41% 33% 6%	840
	21st to end	Night	8% 4 14% 42% 28% 5%	832
October	1st to 10th	Night	11% 4 14% 42% 27% 3	800
	11th to 20th	Night	11% 4 19% 40% 23% 4	800
	21st to end	Night	14% 5% 23% 37% 17% 4	880
November	1st to 10th	Night	16% 6% 22% 40% 15% 1	820
	11th to 20th	Night	18% 9% 25% 32% 14% 2	840
	21st to end	Night	13% 8% 23% 36% 17% 2	840
December	1st to 10th	Night	16% 7% 21% 34% 19% 2	840
	11th to 20th	Night	18% 9% 27% 32% 13% 1	840
	21st to end	Night	20% 10% 32% 28% 10% 1	924

Page generated at 2026-09-26 01:18:44. Version ac07

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