Klickitat County Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Klickitat County Star Party clear sky chart from 2005-11-06 to 2025-10-04.

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% 3 6% 4 4 4 4 5% 7% 50%	135610
	Night	9% 8% 3 6% 4 4 4 4 5% 7% 46%	131080
Transparency	Day	35% 5% 12% 23% 18% 7%	130349
	Night	38% 6% 13% 23% 15% 5%	127354
Seeing	Day	14% 17% 28% 24% 13% 3	15638
	Night	14% 13% 25% 29% 17% 3	24596

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	17% 18% 6% 14% 8% 6% 5% 5% 5% 5% 10%	3639
	11th to 20th	Day	12% 12% 4 8% 4 4 4 3 5% 7% 37%	3640
	21st to end	Day	18% 11% 4 8% 5% 4 4 4 5% 6% 31%	4075
February	1st to 10th	Day	13% 15% 5% 10% 6% 5% 4 4 5% 7% 27%	1800
	11th to 20th	Day	12% 12% 3 9% 7% 5% 5% 4 5% 7% 32%	1760
	21st to end	Day	8% 11% 4 9% 8% 8% 5% 5% 6% 7% 29%	1650
March	1st to 10th	Day	7% 9% 3 9% 6% 5% 6% 5% 8% 10% 32%	4518
	11th to 20th	Day	7% 12% 4 9% 5% 4 4 4 5% 7% 40%	4946
	21st to end	Day	8% 11% 4 11% 8% 7% 6% 5% 7% 8% 23%	5793
April	1st to 10th	Day	8% 9% 3 8% 6% 6% 7% 5% 7% 9% 33%	2400
	11th to 20th	Day	7% 9% 2 7% 5% 5% 6% 4 6% 8% 42%	2369
	21st to end	Day	5% 6% 2 6% 5% 5% 6% 4 7% 8% 46%	2551
May	1st to 10th	Day	9% 5% 2 5% 3 4 3 3 5% 7% 54%	6320
	11th to 20th	Day	4 4 2 6% 4 4 5% 4 6% 8% 53%	6277
	21st to end	Day	5% 5% 2 5% 5% 4 5% 4 6% 8% 52%	6902
June	1st to 10th	Day	9% 5% 2 5% 3 4 5% 5% 6% 8% 49%	2800
	11th to 20th	Day	5% 4 1 4 4 4 5% 4 5% 8% 56%	2800
	21st to end	Day	3 3 1 3 2 2 3 3 4 6% 68%	2800
July	1st to 10th	Day	1 2 2 1 1 1 2 3 4 83%	6319
	11th to 20th	Day	2 1 1 1 1 2 1 2 3 85%	6320
	21st to end	Day	2 2 1 2 1 2 2 2 3 5% 78%	6880
August	1st to 10th	Day	3 3 1 3 2 2 3 3 4 6% 69%	6173
	11th to 20th	Day	2 2 1 3 2 3 3 3 5% 6% 72%	5766
	21st to end	Day	5% 5% 2 4 3 3 3 3 4 5% 63%	5984
September	1st to 10th	Day	3 2 1 3 2 2 3 2 4 6% 72%	2400
	11th to 20th	Day	4 4 2 5% 4 4 4 4 5% 6% 60%	2400
	21st to end	Day	6% 5% 2 5% 3 4 3 3 4 7% 58%	2151
October	1st to 10th	Day	5% 4 2 5% 3 3 3 3 7% 7% 59%	3211
	11th to 20th	Day	6% 7% 3 7% 5% 5% 5% 4 7% 8% 43%	3161
	21st to end	Day	10% 7% 3 8% 6% 5% 5% 4 7% 8% 36%	3195
November	1st to 10th	Day	11% 12% 4 9% 6% 5% 5% 5% 6% 8% 29%	1758
	11th to 20th	Day	13% 11% 5% 10% 8% 6% 5% 5% 7% 8% 22%	1600
	21st to end	Day	10% 13% 4 11% 6% 5% 5% 4 7% 7% 29%	1600
December	1st to 10th	Day	8% 9% 3 9% 6% 5% 4 5% 10% 9% 32%	2620
	11th to 20th	Day	16% 17% 6% 14% 9% 6% 6% 4 5% 5% 12%	3028
	21st to end	Day	14% 17% 6% 15% 8% 6% 5% 3 5% 6% 16%	4004
January	1st to 10th	Night	17% 16% 5% 12% 7% 6% 6% 6% 7% 4 14%	6306
	11th to 20th	Night	13% 10% 3 7% 4 3 4 4 4 6% 42%	6320
	21st to end	Night	15% 11% 4 8% 5% 4 4 3 5% 6% 35%	6881
February	1st to 10th	Night	11% 14% 5% 10% 7% 5% 5% 4 5% 7% 28%	2600
	11th to 20th	Night	11% 12% 4 8% 6% 5% 4 4 5% 6% 36%	2527
	21st to end	Night	9% 14% 4 8% 6% 4 5% 5% 6% 7% 33%	1980
March	1st to 10th	Night	5% 8% 3 8% 6% 6% 6% 5% 7% 10% 36%	5376
	11th to 20th	Night	8% 8% 3 8% 5% 5% 4 4 5% 6% 43%	5053
	21st to end	Night	8% 10% 4 9% 6% 7% 7% 5% 7% 8% 29%	5182
April	1st to 10th	Night	8% 9% 3 8% 4 5% 4 4 8% 9% 39%	2000
	11th to 20th	Night	8% 6% 2 5% 5% 4 4 3 5% 7% 51%	1979
	21st to end	Night	5% 5% 3 7% 5% 4 5% 4 7% 9% 46%	1843
May	1st to 10th	Night	7% 7% 3 5% 3 3 3 2 3 5% 60%	3640
	11th to 20th	Night	5% 4 2 4 3 3 3 3 6% 8% 61%	3616
	21st to end	Night	7% 6% 2 3 2 3 3 3 5% 8% 59%	3972
June	1st to 10th	Night	10% 5% 2 4 4 4 3 4 6% 7% 51%	1600
	11th to 20th	Night	6% 5% 2 3 4 2 4 3 5% 7% 60%	1600
	21st to end	Night	3 4 1 5% 3 3 3 2 5% 4 67%	1600
July	1st to 10th	Night	1 2 1 2 1 2 2 2 3 4 80%	3640
	11th to 20th	Night	1 1 1 1 1 1 2 3 3 85%	3640
	21st to end	Night	2 2 1 1 1 1 1 4 6% 80%	3970
August	1st to 10th	Night	3 3 1 3 3 3 3 3 5% 7% 68%	3618
	11th to 20th	Night	3 2 1 3 2 3 3 3 4 5% 71%	4070
	21st to end	Night	3 4 1 5% 3 2 3 3 4 6% 65%	5015
September	1st to 10th	Night	2 2 1 3 3 2 3 2 5% 6% 72%	2000
	11th to 20th	Night	4 4 1 3 3 4 4 3 4 5% 63%	2000
	21st to end	Night	6% 3 2 4 3 3 3 3 5% 7% 61%	2245
October	1st to 10th	Night	4 4 2 4 3 3 3 3 5% 6% 63%	3836
	11th to 20th	Night	6% 5% 2 7% 5% 4 5% 4 7% 8% 45%	3777
	21st to end	Night	9% 6% 2 6% 4 5% 5% 5% 7% 8% 42%	4366
November	1st to 10th	Night	13% 10% 3 8% 5% 4 4 4 6% 7% 35%	2540
	11th to 20th	Night	14% 12% 4 7% 6% 5% 6% 4 6% 7% 29%	2800
	21st to end	Night	10% 9% 3 9% 7% 5% 6% 4 7% 7% 33%	2800
December	1st to 10th	Night	7% 7% 2 8% 6% 5% 5% 5% 8% 8% 40%	4560
	11th to 20th	Night	20% 16% 5% 11% 7% 6% 5% 4 6% 6% 14%	5176
	21st to end	Night	18% 12% 5% 10% 6% 5% 4 4 5% 7% 25%	6952

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	69% 7% 13% 9% 2	3639
	11th to 20th	Day	46% 8% 16% 21% 9%	3640
	21st to end	Day	54% 8% 8% 17% 12% 1	4075
February	1st to 10th	Day	57% 9% 15% 15% 4	1800
	11th to 20th	Day	51% 11% 15% 16% 7%	1769
	21st to end	Day	51% 10% 17% 13% 8% 1	1650
March	1st to 10th	Day	43% 5% 15% 22% 13% 1	4518
	11th to 20th	Day	44% 5% 12% 28% 11%	4946
	21st to end	Day	55% 7% 15% 17% 5%	5793
April	1st to 10th	Day	45% 9% 17% 20% 10%	2400
	11th to 20th	Day	40% 8% 15% 21% 13% 3	2372
	21st to end	Day	33% 10% 15% 26% 14% 2	2551
May	1st to 10th	Day	30% 3 10% 22% 30% 4	6320
	11th to 20th	Day	30% 4 14% 32% 18% 3	6280
	21st to end	Day	28% 7% 20% 33% 12% 1	6904
June	1st to 10th	Day	32% 8% 12% 28% 17% 4	2800
	11th to 20th	Day	25% 6% 14% 32% 19% 4	2800
	21st to end	Day	18% 5% 12% 32% 24% 9%	2800
July	1st to 10th	Day	9% 2 5% 21% 34% 31%	6251
	11th to 20th	Day	8% 1 4 13% 33% 41%	6245
	21st to end	Day	13% 1 5% 29% 35% 17%	6681
August	1st to 10th	Day	16% 2 5% 15% 36% 26%	4499
	11th to 20th	Day	15% 2 7% 40% 27% 9%	4177
	21st to end	Day	23% 2 9% 25% 34% 7%	4311
September	1st to 10th	Day	15% 4 8% 30% 29% 13%	2400
	11th to 20th	Day	25% 5% 11% 28% 23% 8%	2400
	21st to end	Day	28% 5% 14% 28% 19% 5%	2151
October	1st to 10th	Day	26% 5% 10% 31% 26% 3	3211
	11th to 20th	Day	39% 6% 16% 23% 16% 1	3161
	21st to end	Day	45% 5% 10% 27% 11% 1	3195
November	1st to 10th	Day	52% 9% 14% 18% 6% 1	1758
	11th to 20th	Day	58% 12% 15% 11% 3 1	1600
	21st to end	Day	52% 11% 15% 14% 8% 1	1600
December	1st to 10th	Day	44% 5% 18% 27% 6%	2620
	11th to 20th	Day	71% 10% 9% 8% 2	3028
	21st to end	Day	68% 8% 13% 10% 1	4004
January	1st to 10th	Night	65% 10% 13% 11% 2	6306
	11th to 20th	Night	43% 7% 17% 25% 8%	6320
	21st to end	Night	51% 9% 9% 18% 12% 1	6881
February	1st to 10th	Night	54% 9% 17% 15% 3 1	2600
	11th to 20th	Night	48% 8% 15% 19% 9% 1	2529
	21st to end	Night	48% 10% 16% 17% 8% 1	1980
March	1st to 10th	Night	40% 5% 16% 25% 13% 1	5376
	11th to 20th	Night	41% 6% 14% 27% 11%	5053
	21st to end	Night	49% 10% 17% 22% 3	5182
April	1st to 10th	Night	39% 10% 17% 23% 10% 1	2000
	11th to 20th	Night	33% 6% 16% 28% 14% 3	1979
	21st to end	Night	33% 10% 15% 26% 14% 2	1843
May	1st to 10th	Night	28% 3 9% 23% 35% 3	3637
	11th to 20th	Night	23% 3 15% 36% 21% 2	3616
	21st to end	Night	23% 6% 26% 33% 11% 1	3972
June	1st to 10th	Night	31% 9% 11% 31% 13% 4	1600
	11th to 20th	Night	25% 5% 14% 34% 22% 1	1600
	21st to end	Night	20% 4 12% 32% 25% 7%	1600
July	1st to 10th	Night	11% 1 6% 21% 32% 30%	3600
	11th to 20th	Night	8% 1 4 11% 37% 38%	3592
	21st to end	Night	9% 5% 26% 37% 21%	3857
August	1st to 10th	Night	16% 1 4 16% 37% 25%	2624
	11th to 20th	Night	15% 1 6% 42% 26% 9%	2947
	21st to end	Night	18% 2 9% 28% 31% 11%	3608
September	1st to 10th	Night	14% 4 11% 27% 30% 15%	2000
	11th to 20th	Night	23% 6% 9% 30% 22% 11%	2000
	21st to end	Night	22% 6% 13% 29% 22% 8%	2245
October	1st to 10th	Night	22% 4 9% 31% 32% 2	3836
	11th to 20th	Night	37% 4 14% 27% 17% 1	3777
	21st to end	Night	40% 5% 9% 30% 14% 1	4366
November	1st to 10th	Night	47% 9% 14% 20% 9%	2540
	11th to 20th	Night	53% 11% 14% 17% 5%	2800
	21st to end	Night	47% 12% 15% 18% 8%	2800
December	1st to 10th	Night	40% 5% 15% 32% 7%	4560
	11th to 20th	Night	69% 9% 12% 8% 2	5176
	21st to end	Night	59% 10% 14% 13% 5%	6952

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	27% 23% 23% 18% 8% 3	200
	11th to 20th	Day	24% 17% 25% 25% 9% 2	200
	21st to end	Day	21% 18% 27% 19% 13% 2	252
February	1st to 10th	Day	27% 17% 30% 20% 6% 1	400
	11th to 20th	Day	27% 19% 28% 21% 5% 1	398
	21st to end	Day	21% 25% 25% 22% 7% 1	414
March	1st to 10th	Day	20% 22% 32% 18% 7% 1	500
	11th to 20th	Day	21% 21% 29% 20% 8% 1	500
	21st to end	Day	21% 25% 30% 17% 7% 1	550
April	1st to 10th	Day	21% 20% 32% 16% 8% 3	500
	11th to 20th	Day	18% 27% 28% 16% 8% 2	492
	21st to end	Day	14% 26% 31% 20% 8% 2	500
May	1st to 10th	Day	13% 18% 32% 24% 11% 2	503
	11th to 20th	Day	17% 17% 30% 21% 12% 3	528
	21st to end	Day	11% 17% 27% 28% 12% 5%	573
June	1st to 10th	Day	12% 21% 24% 26% 14% 3	530
	11th to 20th	Day	11% 25% 35% 20% 7% 2	530
	21st to end	Day	7% 17% 27% 32% 14% 4	530
July	1st to 10th	Day	3 10% 37% 33% 15% 3	526
	11th to 20th	Day	3 11% 34% 32% 16% 3	524
	21st to end	Day	3 7% 29% 35% 21% 5%	575
August	1st to 10th	Day	6% 8% 26% 31% 20% 9%	527
	11th to 20th	Day	2 8% 25% 31% 26% 7%	517
	21st to end	Day	9% 11% 29% 26% 19% 6%	583
September	1st to 10th	Day	6% 9% 28% 32% 17% 8%	530
	11th to 20th	Day	9% 9% 30% 32% 16% 4	530
	21st to end	Day	9% 18% 25% 27% 18% 3	530
October	1st to 10th	Day	13% 17% 28% 23% 16% 3	503
	11th to 20th	Day	18% 17% 23% 24% 14% 4	490
	21st to end	Day	19% 21% 25% 18% 14% 3	387
November	1st to 10th	Day	20% 20% 26% 23% 11%	296
	11th to 20th	Day	23% 23% 20% 24% 9% 3	200
	21st to end	Day	17% 19% 28% 22% 13% 2	200
December	1st to 10th	Day	22% 17% 25% 16% 13% 8%	200
	11th to 20th	Day	26% 21% 25% 21% 7% 1	200
	21st to end	Day	24% 23% 23% 19% 11%	220
January	1st to 10th	Night	26% 15% 22% 28% 8% 1	800
	11th to 20th	Night	21% 11% 25% 25% 16% 3	800
	21st to end	Night	21% 10% 21% 29% 17% 2	880
February	1st to 10th	Night	20% 16% 25% 25% 13% 2	800
	11th to 20th	Night	18% 17% 23% 28% 12% 1	784
	21st to end	Night	19% 19% 26% 25% 10% 1	660
March	1st to 10th	Night	16% 14% 29% 25% 15% 2	800
	11th to 20th	Night	14% 16% 27% 30% 11% 2	800
	21st to end	Night	15% 21% 31% 21% 10% 2	880
April	1st to 10th	Night	16% 16% 28% 25% 13% 3	800
	11th to 20th	Night	15% 19% 29% 20% 14% 3	791
	21st to end	Night	11% 19% 29% 26% 14% 2	643
May	1st to 10th	Night	9% 16% 26% 30% 16% 3	400
	11th to 20th	Night	13% 7% 27% 32% 19% 2	394
	21st to end	Night	9% 6% 30% 33% 18% 4	433
June	1st to 10th	Night	14% 13% 24% 30% 17% 2	400
	11th to 20th	Night	10% 16% 33% 29% 12% 1	400
	21st to end	Night	6% 11% 23% 38% 21% 2	400
July	1st to 10th	Night	4 5% 27% 41% 22% 2	390
	11th to 20th	Night	2 6% 32% 41% 16% 3	388
	21st to end	Night	2 7% 18% 44% 27% 3	438
August	1st to 10th	Night	3 5% 16% 44% 27% 5%	408
	11th to 20th	Night	5% 3 18% 33% 29% 13%	599
	21st to end	Night	4 9% 25% 34% 23% 5%	880
September	1st to 10th	Night	3 6% 22% 36% 29% 4	800
	11th to 20th	Night	6% 7% 22% 31% 28% 8%	800
	21st to end	Night	8% 11% 21% 28% 28% 5%	800
October	1st to 10th	Night	10% 9% 24% 33% 20% 3	772
	11th to 20th	Night	14% 12% 21% 28% 21% 4	760
	21st to end	Night	16% 15% 24% 27% 15% 4	836
November	1st to 10th	Night	20% 12% 26% 30% 12%	780
	11th to 20th	Night	23% 14% 25% 24% 13% 2	800
	21st to end	Night	14% 14% 23% 28% 17% 3	800
December	1st to 10th	Night	17% 13% 25% 27% 16% 3	800
	11th to 20th	Night	25% 11% 24% 27% 12% 2	800
	21st to end	Night	23% 16% 27% 24% 9% 1	880

Page generated at 2025-09-30 22:39:05. Version ac07

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