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 2024-11-02.

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	7% 7% 2 6% 4 4 4 3 5% 6% 51%	101534
	Night	8% 9% 3 7% 4 4 4 4 5% 6% 46%	97592
Transparency	Day	34% 2 10% 23% 20% 11%	101277
	Night	39% 3 12% 24% 16% 6%	97438
Seeing	Day	12% 11% 23% 26% 20% 8%	14644
	Night	12% 6% 21% 38% 21% 2	23668

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	13% 12% 4 10% 7% 7% 7% 5% 6% 7% 23%	2539
	11th to 20th	Day	18% 17% 4 9% 7% 5% 6% 4 5% 5% 21%	2540
	21st to end	Day	13% 15% 5% 9% 5% 4 5% 3 5% 7% 27%	2989
February	1st to 10th	Day	8% 12% 4 8% 6% 6% 5% 5% 6% 7% 33%	1710
	11th to 20th	Day	8% 12% 3 8% 5% 5% 5% 4 7% 8% 34%	1674
	21st to end	Day	7% 13% 4 10% 6% 4 6% 5% 7% 8% 30%	1570
March	1st to 10th	Day	6% 11% 5% 10% 6% 6% 6% 4 7% 8% 31%	3159
	11th to 20th	Day	5% 10% 2 6% 5% 4 3 3 5% 6% 49%	3490
	21st to end	Day	7% 12% 4 11% 6% 6% 6% 5% 6% 7% 28%	4002
April	1st to 10th	Day	9% 12% 4 9% 6% 6% 6% 4 5% 7% 32%	2280
	11th to 20th	Day	9% 10% 3 8% 6% 4 4 5% 5% 7% 38%	2249
	21st to end	Day	7% 8% 3 6% 4 5% 4 4 7% 8% 44%	2337
May	1st to 10th	Day	11% 8% 2 7% 4 4 4 4 5% 6% 45%	4420
	11th to 20th	Day	6% 4 2 4 3 3 3 3 5% 6% 63%	4377
	21st to end	Day	7% 6% 2 5% 4 4 5% 4 6% 8% 49%	4813
June	1st to 10th	Day	10% 8% 3 6% 5% 5% 4 4 6% 7% 43%	2660
	11th to 20th	Day	6% 5% 2 5% 3 4 4 4 5% 7% 55%	2660
	21st to end	Day	4 3 1 3 3 2 3 3 5% 6% 66%	2660
July	1st to 10th	Day	1 1 1 1 2 1 2 2 3 85%	4420
	11th to 20th	Day	2 1 1 2 1 2 2 2 2 4 81%	4420
	21st to end	Day	1 1 1 2 1 1 2 2 3 4 82%	4790
August	1st to 10th	Day	3 2 1 3 2 2 3 3 5% 5% 71%	4219
	11th to 20th	Day	2 1 1 3 2 3 3 2 4 7% 72%	3996
	21st to end	Day	4 3 1 3 2 2 2 2 3 5% 74%	4180
September	1st to 10th	Day	2 2 1 2 2 2 2 2 3 5% 77%	2280
	11th to 20th	Day	4 3 1 5% 3 3 3 4 6% 6% 61%	2280
	21st to end	Day	7% 6% 1 5% 2 3 3 3 4 6% 60%	2037
October	1st to 10th	Day	8% 6% 2 6% 4 4 3 3 4 5% 54%	1900
	11th to 20th	Day	9% 6% 2 5% 4 4 4 3 5% 10% 48%	1900
	21st to end	Day	11% 8% 3 7% 4 5% 4 3 5% 5% 44%	1994
November	1st to 10th	Day	11% 11% 3 7% 5% 5% 5% 3 6% 8% 35%	1683
	11th to 20th	Day	10% 10% 4 8% 6% 6% 6% 5% 7% 7% 30%	1544
	21st to end	Day	9% 10% 3 8% 5% 4 5% 6% 7% 8% 36%	1520
December	1st to 10th	Day	9% 9% 4 7% 6% 4 5% 4 7% 8% 37%	1520
	11th to 20th	Day	10% 12% 4 10% 6% 6% 5% 5% 7% 8% 27%	1928
	21st to end	Day	8% 14% 5% 10% 7% 6% 5% 4 6% 7% 28%	2794
January	1st to 10th	Night	10% 13% 5% 11% 7% 7% 6% 5% 7% 7% 21%	4406
	11th to 20th	Night	16% 16% 5% 10% 7% 6% 6% 4 5% 6% 20%	4420
	21st to end	Night	13% 15% 5% 10% 6% 5% 6% 4 6% 6% 25%	4672
February	1st to 10th	Night	8% 13% 4 10% 6% 5% 6% 5% 6% 7% 31%	2470
	11th to 20th	Night	9% 12% 4 8% 5% 5% 5% 4 5% 7% 37%	2393
	21st to end	Night	7% 13% 4 9% 6% 5% 6% 5% 6% 8% 30%	1884
March	1st to 10th	Night	6% 11% 4 9% 6% 6% 6% 5% 7% 8% 33%	3710
	11th to 20th	Night	5% 8% 2 6% 3 3 4 4 5% 6% 51%	3490
	21st to end	Night	7% 11% 4 11% 8% 7% 7% 6% 8% 8% 25%	3649
April	1st to 10th	Night	10% 13% 3 7% 4 4 4 5% 6% 6% 37%	1900
	11th to 20th	Night	9% 14% 3 8% 5% 4 4 3 6% 6% 38%	1879
	21st to end	Night	9% 8% 3 6% 5% 5% 6% 5% 6% 8% 39%	1838
May	1st to 10th	Night	11% 9% 3 7% 4 4 4 4 6% 7% 43%	2540
	11th to 20th	Night	4 4 2 4 4 3 4 3 5% 5% 63%	2516
	21st to end	Night	8% 6% 2 5% 4 4 4 3 6% 7% 53%	2762
June	1st to 10th	Night	11% 7% 2 6% 4 4 3 3 6% 6% 47%	1520
	11th to 20th	Night	6% 6% 2 4 3 3 2 3 5% 9% 58%	1520
	21st to end	Night	4 4 1 3 2 3 3 3 4 6% 69%	1520
July	1st to 10th	Night	1 1 1 1 1 1 2 2 3 86%	2540
	11th to 20th	Night	2 2 1 2 2 2 2 2 2 4 82%	2540
	21st to end	Night	1 1 1 2 1 2 2 2 2 3 84%	2761
August	1st to 10th	Night	1 2 1 4 2 3 2 3 5% 5% 72%	2713
	11th to 20th	Night	1 1 1 3 2 3 3 3 4 6% 73%	2841
	21st to end	Night	2 3 1 3 2 2 2 2 4 4 76%	3498
September	1st to 10th	Night	2 2 1 2 1 1 2 2 4 5% 78%	1900
	11th to 20th	Night	4 4 1 5% 3 3 4 3 5% 6% 62%	1900
	21st to end	Night	7% 4 1 4 2 3 3 3 4 6% 62%	2139
October	1st to 10th	Night	8% 6% 2 5% 3 3 3 3 4 6% 58%	2280
	11th to 20th	Night	8% 5% 3 5% 3 3 4 3 6% 7% 53%	2280
	21st to end	Night	10% 7% 3 6% 4 4 4 4 6% 6% 45%	2603
November	1st to 10th	Night	12% 10% 4 8% 6% 4 5% 5% 5% 6% 36%	2418
	11th to 20th	Night	12% 10% 3 9% 6% 5% 5% 5% 6% 7% 32%	2632
	21st to end	Night	9% 9% 3 6% 5% 4 5% 5% 6% 8% 40%	2660
December	1st to 10th	Night	9% 12% 4 8% 5% 4 4 3 6% 8% 37%	2660
	11th to 20th	Night	10% 12% 4 11% 6% 6% 6% 5% 6% 7% 26%	3276
	21st to end	Night	9% 14% 4 10% 6% 6% 5% 4 6% 7% 30%	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	59% 3 15% 18% 5%	2539
	11th to 20th	Day	64% 3 12% 14% 4 3	2540
	21st to end	Day	55% 3 15% 20% 6% 1	2989
February	1st to 10th	Day	49% 4 15% 24% 8%	1710
	11th to 20th	Day	45% 4 15% 23% 11% 2	1683
	21st to end	Day	50% 5% 16% 18% 10% 1	1570
March	1st to 10th	Day	50% 2 8% 23% 16% 1	3159
	11th to 20th	Day	36% 2 12% 33% 17%	3490
	21st to end	Day	55% 2 10% 25% 7% 1	4002
April	1st to 10th	Day	52% 3 11% 20% 13% 2	2280
	11th to 20th	Day	47% 3 12% 20% 14% 4	2252
	21st to end	Day	39% 3 12% 29% 14% 3	2337
May	1st to 10th	Day	42% 1 7% 26% 23% 1	4420
	11th to 20th	Day	25% 1 6% 29% 34% 5%	4380
	21st to end	Day	35% 2 16% 31% 15% 1	4814
June	1st to 10th	Day	41% 2 10% 30% 15% 2	2660
	11th to 20th	Day	30% 3 10% 33% 21% 4	2660
	21st to end	Day	20% 2 8% 30% 30% 10%	2660
July	1st to 10th	Day	8% 1 4 13% 22% 52%	4351
	11th to 20th	Day	10% 1 3 9% 23% 54%	4345
	21st to end	Day	9% 2 3 17% 38% 32%	4639
August	1st to 10th	Day	16% 2 3 16% 37% 25%	4203
	11th to 20th	Day	14% 2 6% 30% 32% 16%	4035
	21st to end	Day	16% 2 5% 26% 30% 20%	4179
September	1st to 10th	Day	13% 1 4 26% 34% 23%	2280
	11th to 20th	Day	24% 3 8% 27% 26% 12%	2280
	21st to end	Day	27% 2 8% 27% 25% 11%	2037
October	1st to 10th	Day	34% 2 9% 22% 22% 10%	1900
	11th to 20th	Day	34% 3 14% 24% 21% 5%	1900
	21st to end	Day	42% 3 11% 23% 19% 3	1994
November	1st to 10th	Day	47% 2 12% 25% 12% 1	1683
	11th to 20th	Day	49% 4 19% 20% 9%	1544
	21st to end	Day	43% 5% 16% 20% 15% 1	1520
December	1st to 10th	Day	44% 5% 15% 27% 9% 1	1520
	11th to 20th	Day	53% 3 19% 20% 5%	1928
	21st to end	Day	55% 3 14% 23% 4 1	2794
January	1st to 10th	Night	60% 4 16% 16% 5%	4406
	11th to 20th	Night	65% 3 11% 14% 5% 3	4420
	21st to end	Night	59% 2 14% 17% 7% 1	4672
February	1st to 10th	Night	52% 4 17% 18% 9%	2470
	11th to 20th	Night	45% 5% 17% 22% 10% 1	2395
	21st to end	Night	51% 5% 13% 22% 8% 1	1884
March	1st to 10th	Night	48% 3 9% 25% 14% 1	3710
	11th to 20th	Night	33% 3 14% 39% 12%	3490
	21st to end	Night	55% 3 16% 20% 6%	3649
April	1st to 10th	Night	48% 3 18% 20% 10% 1	1900
	11th to 20th	Night	47% 3 14% 22% 13% 2	1879
	21st to end	Night	41% 5% 15% 26% 11% 2	1838
May	1st to 10th	Night	43% 1 9% 30% 16%	2540
	11th to 20th	Night	24% 3 9% 39% 23% 2	2516
	21st to end	Night	33% 2 28% 30% 7%	2762
June	1st to 10th	Night	39% 4 12% 31% 13% 1	1520
	11th to 20th	Night	26% 3 14% 39% 15% 3	1520
	21st to end	Night	19% 2 11% 35% 26% 7%	1520
July	1st to 10th	Night	7% 1 5% 16% 27% 44%	2500
	11th to 20th	Night	11% 2 4 15% 21% 48%	2492
	21st to end	Night	9% 2 3 19% 39% 28%	2674
August	1st to 10th	Night	16% 2 4 19% 40% 19%	2705
	11th to 20th	Night	12% 3 8% 38% 29% 10%	2868
	21st to end	Night	14% 3 9% 29% 31% 14%	3498
September	1st to 10th	Night	11% 2 5% 29% 36% 17%	1900
	11th to 20th	Night	24% 3 9% 26% 26% 12%	1900
	21st to end	Night	24% 2 8% 29% 25% 11%	2139
October	1st to 10th	Night	29% 3 9% 26% 26% 7%	2280
	11th to 20th	Night	31% 3 16% 25% 21% 5%	2280
	21st to end	Night	41% 3 13% 22% 19% 2	2603
November	1st to 10th	Night	48% 4 11% 22% 13% 2	2418
	11th to 20th	Night	49% 5% 15% 24% 7%	2632
	21st to end	Night	41% 4 16% 22% 16% 1	2660
December	1st to 10th	Night	45% 5% 17% 23% 9% 1	2660
	11th to 20th	Night	55% 3 15% 20% 7%	3276
	21st to end	Night	54% 3 14% 23% 6% 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	23% 12% 32% 21% 11% 1	180
	11th to 20th	Day	21% 11% 27% 24% 13% 4	180
	21st to end	Day	17% 12% 26% 26% 17% 2	315
February	1st to 10th	Day	20% 15% 22% 29% 13% 1	370
	11th to 20th	Day	17% 18% 28% 22% 12% 2	369
	21st to end	Day	20% 14% 27% 26% 11% 2	382
March	1st to 10th	Day	19% 18% 23% 30% 8% 1	460
	11th to 20th	Day	15% 15% 24% 27% 15% 4	460
	21st to end	Day	18% 18% 24% 25% 13% 1	506
April	1st to 10th	Day	20% 16% 23% 23% 13% 6%	460
	11th to 20th	Day	15% 19% 25% 23% 12% 6%	452
	21st to end	Day	12% 18% 24% 24% 16% 6%	460
May	1st to 10th	Day	12% 13% 27% 24% 16% 8%	463
	11th to 20th	Day	18% 12% 20% 23% 18% 9%	488
	21st to end	Day	12% 9% 21% 24% 21% 12%	529
June	1st to 10th	Day	11% 12% 20% 23% 20% 13%	490
	11th to 20th	Day	10% 15% 24% 26% 19% 6%	490
	21st to end	Day	5% 7% 20% 29% 27% 13%	490
July	1st to 10th	Day	2 5% 25% 31% 26% 11%	486
	11th to 20th	Day	2 6% 27% 24% 29% 12%	484
	21st to end	Day	2 4 26% 27% 26% 15%	531
August	1st to 10th	Day	2 4 21% 31% 26% 16%	487
	11th to 20th	Day	2 4 17% 30% 27% 20%	477
	21st to end	Day	5% 7% 19% 27% 28% 15%	539
September	1st to 10th	Day	3 3 23% 26% 29% 16%	490
	11th to 20th	Day	6% 7% 19% 30% 29% 10%	490
	21st to end	Day	10% 7% 20% 27% 28% 8%	490
October	1st to 10th	Day	11% 10% 19% 27% 23% 10%	490
	11th to 20th	Day	14% 9% 20% 26% 24% 7%	490
	21st to end	Day	17% 11% 23% 24% 20% 5%	443
November	1st to 10th	Day	17% 9% 25% 32% 14% 2	273
	11th to 20th	Day	19% 14% 19% 27% 17% 5%	192
	21st to end	Day	18% 10% 23% 30% 17% 2	180
December	1st to 10th	Day	12% 16% 22% 30% 12% 8%	180
	11th to 20th	Day	18% 13% 34% 30% 5%	180
	21st to end	Day	18% 12% 28% 30% 10% 2	198
January	1st to 10th	Night	17% 8% 30% 29% 13% 2	760
	11th to 20th	Night	18% 9% 24% 29% 18% 3	760
	21st to end	Night	15% 7% 22% 38% 16% 2	836
February	1st to 10th	Night	15% 9% 27% 35% 13% 1	760
	11th to 20th	Night	15% 6% 25% 39% 14% 1	744
	21st to end	Night	14% 10% 28% 36% 11%	628
March	1st to 10th	Night	16% 12% 24% 36% 11% 1	760
	11th to 20th	Night	13% 8% 23% 39% 16% 2	760
	21st to end	Night	14% 10% 27% 34% 14% 2	836
April	1st to 10th	Night	17% 9% 22% 33% 19% 1	760
	11th to 20th	Night	16% 7% 26% 31% 17% 2	751
	21st to end	Night	12% 8% 25% 35% 18% 1	698
May	1st to 10th	Night	13% 5% 17% 43% 21% 2	380
	11th to 20th	Night	10% 5% 15% 43% 26% 1	374
	21st to end	Night	11% 5% 15% 40% 26% 3	411
June	1st to 10th	Night	14% 5% 17% 42% 21% 1	380
	11th to 20th	Night	8% 4 22% 46% 20% 1	380
	21st to end	Night	6% 2 14% 52% 26% 1	380
July	1st to 10th	Night	2 2 9% 56% 31% 1	370
	11th to 20th	Night	2 1 14% 59% 23% 1	368
	21st to end	Night	1 11% 54% 32% 2	416
August	1st to 10th	Night	2 1 6% 48% 40% 3	484
	11th to 20th	Night	2 1 6% 42% 42% 8%	580
	21st to end	Night	3 2 16% 44% 32% 3	836
September	1st to 10th	Night	3 1 15% 44% 33% 4	760
	11th to 20th	Night	6% 2 13% 40% 34% 6%	760
	21st to end	Night	8% 4 14% 41% 27% 5%	760
October	1st to 10th	Night	10% 4 14% 42% 27% 3	760
	11th to 20th	Night	11% 4 18% 39% 24% 4	760
	21st to end	Night	14% 6% 22% 36% 17% 4	836
November	1st to 10th	Night	17% 6% 21% 40% 15% 1	744
	11th to 20th	Night	18% 8% 26% 32% 15% 2	760
	21st to end	Night	13% 8% 23% 36% 17% 3	760
December	1st to 10th	Night	16% 8% 21% 35% 18% 2	760
	11th to 20th	Night	17% 8% 27% 32% 14% 1	760
	21st to end	Night	20% 10% 31% 28% 10% 1	836

Page generated at 2024-10-29 22:22:54. Version ac07

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