Palouse Falls Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Palouse Falls Star Party clear sky chart from 2005-11-06 to 2026-09-14.

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 4 5% 7% 51%	153329
	Night	8% 8% 3 8% 5% 5% 5% 4 6% 7% 43%	146504
Transparency	Day	32% 6% 11% 22% 20% 9%	153057
	Night	38% 7% 11% 20% 16% 7%	146358
Seeing	Day	11% 10% 23% 27% 20% 9%	16638
	Night	13% 8% 20% 34% 21% 3	25650

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	14% 16% 8% 17% 7% 6% 5% 4 5% 5% 13%	4723
	11th to 20th	Day	10% 8% 5% 10% 6% 6% 7% 6% 8% 7% 26%	4716
	21st to end	Day	12% 12% 5% 11% 6% 6% 5% 5% 7% 8% 25%	5186
February	1st to 10th	Day	13% 15% 6% 11% 6% 6% 6% 4 5% 7% 23%	1759
	11th to 20th	Day	13% 13% 4 12% 5% 4 5% 3 6% 5% 30%	1955
	21st to end	Day	9% 11% 4 9% 6% 5% 6% 4 5% 7% 33%	1730
March	1st to 10th	Day	5% 7% 3 7% 5% 6% 6% 7% 8% 10% 36%	4618
	11th to 20th	Day	6% 7% 3 7% 5% 5% 6% 4 6% 7% 44%	4765
	21st to end	Day	10% 9% 3 10% 7% 6% 6% 5% 7% 9% 28%	6101
April	1st to 10th	Day	7% 8% 2 8% 6% 6% 6% 5% 9% 8% 36%	2520
	11th to 20th	Day	5% 8% 2 7% 5% 5% 5% 4 7% 7% 44%	2503
	21st to end	Day	7% 6% 2 6% 5% 5% 4 4 6% 8% 48%	2730
May	1st to 10th	Day	5% 4 1 4 2 3 3 3 6% 7% 61%	8076
	11th to 20th	Day	5% 5% 2 5% 5% 5% 5% 4 6% 9% 50%	8160
	21st to end	Day	5% 4 2 5% 4 5% 6% 5% 7% 8% 51%	8993
June	1st to 10th	Day	9% 6% 2 6% 4 4 5% 4 6% 7% 46%	2940
	11th to 20th	Day	6% 4 2 5% 4 4 4 4 6% 8% 54%	2940
	21st to end	Day	3 3 1 4 3 4 4 2 5% 7% 63%	2940
July	1st to 10th	Day	2 2 1 2 2 2 2 2 3 5% 78%	8220
	11th to 20th	Day	3 2 1 3 2 2 2 2 3 4 77%	8220
	21st to end	Day	2 1 2 1 2 2 2 4 6% 79%	8916
August	1st to 10th	Day	2 1 1 2 1 2 2 2 3 4 80%	6441
	11th to 20th	Day	1 1 1 2 2 2 3 3 5% 7% 73%	6061
	21st to end	Day	2 3 1 3 3 3 3 3 5% 7% 69%	6078
September	1st to 10th	Day	2 2 1 3 2 3 3 3 4 6% 70%	2520
	11th to 20th	Day	5% 4 2 5% 3 4 4 4 6% 7% 56%	2353
	21st to end	Day	5% 5% 1 6% 4 3 5% 3 5% 7% 57%	2200
October	1st to 10th	Day	4 3 1 4 3 4 3 3 5% 7% 63%	3409
	11th to 20th	Day	5% 3 2 5% 4 5% 6% 5% 8% 9% 47%	3143
	21st to end	Day	10% 6% 3 6% 4 4 4 5% 7% 9% 41%	3200
November	1st to 10th	Day	14% 8% 3 7% 7% 5% 5% 4 8% 8% 32%	1854
	11th to 20th	Day	12% 13% 5% 11% 6% 7% 6% 4 5% 6% 25%	1782
	21st to end	Day	10% 13% 5% 15% 9% 6% 6% 5% 6% 6% 20%	1680
December	1st to 10th	Day	11% 10% 4 15% 8% 8% 8% 5% 5% 6% 21%	2700
	11th to 20th	Day	16% 17% 7% 18% 8% 5% 5% 3 4 4 14%	3105
	21st to end	Day	16% 12% 7% 13% 8% 7% 5% 4 6% 7% 15%	4092
January	1st to 10th	Night	17% 19% 7% 15% 6% 6% 5% 3 5% 5% 12%	8172
	11th to 20th	Night	10% 9% 4 7% 5% 6% 7% 6% 9% 9% 28%	8182
	21st to end	Night	10% 11% 4 12% 7% 6% 5% 5% 7% 11% 23%	8994
February	1st to 10th	Night	13% 13% 4 10% 6% 5% 5% 4 6% 6% 27%	2858
	11th to 20th	Night	11% 11% 4 9% 6% 5% 6% 4 6% 8% 32%	2550
	21st to end	Night	10% 11% 4 10% 5% 6% 5% 4 6% 7% 31%	2076
March	1st to 10th	Night	6% 6% 2 8% 5% 5% 5% 5% 7% 10% 39%	5496
	11th to 20th	Night	7% 11% 4 7% 4 4 4 4 5% 6% 44%	5439
	21st to end	Night	7% 8% 4 9% 6% 8% 8% 6% 8% 9% 27%	5116
April	1st to 10th	Night	9% 10% 3 7% 5% 5% 5% 5% 6% 8% 36%	2100
	11th to 20th	Night	8% 7% 3 6% 5% 4 5% 4 5% 7% 46%	2066
	21st to end	Night	6% 7% 2 9% 5% 4 4 4 6% 9% 43%	1890
May	1st to 10th	Night	4 3 1 4 3 3 5% 4 6% 8% 58%	4846
	11th to 20th	Night	5% 6% 3 7% 4 4 6% 5% 6% 8% 46%	4700
	21st to end	Night	5% 5% 2 6% 4 5% 5% 4 7% 9% 49%	5178
June	1st to 10th	Night	8% 6% 2 4 5% 4 5% 5% 6% 7% 47%	1680
	11th to 20th	Night	7% 5% 2 6% 4 4 4 3 5% 7% 52%	1680
	21st to end	Night	5% 4 2 4 4 4 4 3 5% 6% 58%	1680
July	1st to 10th	Night	2 1 1 2 1 2 2 2 4 6% 78%	4740
	11th to 20th	Night	1 1 1 3 2 2 2 3 4 5% 76%	4740
	21st to end	Night	2 2 1 2 2 2 2 2 3 5% 78%	5152
August	1st to 10th	Night	3 2 1 2 1 2 2 2 3 4 79%	3709
	11th to 20th	Night	1 2 1 3 2 3 4 3 6% 7% 68%	3992
	21st to end	Night	2 2 1 3 3 3 3 3 4 5% 72%	5092
September	1st to 10th	Night	2 3 1 3 2 3 3 3 4 7% 69%	2100
	11th to 20th	Night	5% 4 1 4 4 4 4 4 5% 7% 59%	2113
	21st to end	Night	5% 4 1 5% 3 3 4 4 5% 8% 58%	2200
October	1st to 10th	Night	5% 3 2 4 3 3 3 3 4 7% 63%	3787
	11th to 20th	Night	7% 4 2 5% 4 5% 5% 3 6% 9% 51%	4010
	21st to end	Night	9% 5% 2 6% 4 5% 5% 4 6% 8% 45%	4600
November	1st to 10th	Night	14% 8% 3 8% 5% 5% 5% 4 7% 7% 34%	2665
	11th to 20th	Night	14% 10% 4 9% 6% 7% 6% 4 6% 7% 29%	2835
	21st to end	Night	13% 11% 3 10% 7% 5% 6% 5% 7% 7% 26%	2940
December	1st to 10th	Night	8% 7% 4 12% 7% 8% 9% 6% 7% 7% 25%	4700
	11th to 20th	Night	17% 18% 7% 16% 7% 6% 5% 4 5% 5% 10%	5320
	21st to end	Night	16% 13% 6% 13% 6% 6% 5% 4 5% 6% 19%	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	70% 9% 11% 8% 2	4723
	11th to 20th	Day	50% 11% 16% 18% 6%	4740
	21st to end	Day	53% 9% 16% 16% 6%	5187
February	1st to 10th	Day	58% 9% 17% 11% 4	1759
	11th to 20th	Day	54% 9% 14% 18% 5%	1964
	21st to end	Day	50% 9% 11% 21% 8% 1	1730
March	1st to 10th	Day	38% 8% 14% 25% 15% 1	4618
	11th to 20th	Day	38% 6% 13% 31% 12%	4765
	21st to end	Day	49% 9% 16% 18% 7%	6101
April	1st to 10th	Day	41% 9% 16% 24% 10% 1	2520
	11th to 20th	Day	37% 6% 15% 24% 13% 5%	2503
	21st to end	Day	34% 7% 15% 24% 18% 2	2730
May	1st to 10th	Day	22% 4 8% 29% 31% 6%	8076
	11th to 20th	Day	29% 6% 12% 29% 19% 5%	8163
	21st to end	Day	28% 7% 17% 27% 19% 2	8994
June	1st to 10th	Day	36% 7% 8% 24% 20% 5%	2940
	11th to 20th	Day	27% 6% 12% 27% 22% 7%	2940
	21st to end	Day	21% 4 9% 29% 27% 9%	2940
July	1st to 10th	Day	12% 2 4 20% 32% 31%	8151
	11th to 20th	Day	14% 2 3 12% 30% 40%	8145
	21st to end	Day	9% 3 4 23% 36% 25%	8723
August	1st to 10th	Day	10% 2 4 11% 38% 35%	6424
	11th to 20th	Day	11% 4 7% 36% 34% 9%	6103
	21st to end	Day	16% 4 8% 30% 34% 8%	6077
September	1st to 10th	Day	15% 4 9% 29% 29% 14%	2520
	11th to 20th	Day	26% 5% 13% 24% 23% 8%	2353
	21st to end	Day	27% 6% 14% 30% 19% 5%	2200
October	1st to 10th	Day	23% 4 11% 36% 24% 3	3409
	11th to 20th	Day	31% 7% 19% 29% 13% 1	3143
	21st to end	Day	37% 7% 14% 31% 11% 1	3200
November	1st to 10th	Day	47% 10% 17% 21% 5%	1854
	11th to 20th	Day	59% 8% 16% 14% 2 1	1782
	21st to end	Day	59% 11% 15% 10% 4	1680
December	1st to 10th	Day	58% 11% 17% 12% 2	2700
	11th to 20th	Day	73% 7% 10% 9% 1	3108
	21st to end	Day	63% 11% 14% 11% 1	4092
January	1st to 10th	Night	72% 8% 10% 9% 1	8172
	11th to 20th	Night	46% 12% 18% 17% 7%	8220
	21st to end	Night	50% 11% 14% 18% 7%	8994
February	1st to 10th	Night	56% 8% 17% 14% 5%	2858
	11th to 20th	Night	50% 9% 16% 19% 7%	2552
	21st to end	Night	50% 8% 14% 20% 7% 1	2076
March	1st to 10th	Night	36% 7% 10% 27% 19% 1	5496
	11th to 20th	Night	40% 5% 11% 30% 14%	5440
	21st to end	Night	48% 11% 14% 22% 5% 1	5116
April	1st to 10th	Night	44% 8% 15% 23% 10%	2100
	11th to 20th	Night	37% 6% 13% 26% 15% 4	2066
	21st to end	Night	35% 8% 14% 19% 20% 4	1890
May	1st to 10th	Night	23% 5% 9% 24% 32% 7%	4843
	11th to 20th	Night	32% 7% 11% 26% 21% 2	4700
	21st to end	Night	29% 8% 16% 26% 19% 1	5182
June	1st to 10th	Night	33% 7% 11% 24% 21% 6%	1680
	11th to 20th	Night	31% 6% 8% 25% 24% 6%	1680
	21st to end	Night	26% 4 9% 23% 26% 12%	1680
July	1st to 10th	Night	9% 2 3 20% 29% 36%	4700
	11th to 20th	Night	12% 2 4 9% 30% 43%	4692
	21st to end	Night	11% 2 3 16% 39% 29%	5040
August	1st to 10th	Night	12% 2 3 8% 33% 43%	3701
	11th to 20th	Night	16% 4 5% 27% 36% 12%	4016
	21st to end	Night	16% 3 6% 27% 35% 14%	5092
September	1st to 10th	Night	16% 4 8% 22% 30% 19%	2100
	11th to 20th	Night	24% 6% 10% 24% 24% 12%	2113
	21st to end	Night	24% 5% 12% 29% 21% 9%	2200
October	1st to 10th	Night	22% 4 10% 29% 32% 2	3787
	11th to 20th	Night	31% 5% 16% 24% 23% 2	4010
	21st to end	Night	35% 6% 11% 32% 14% 1	4600
November	1st to 10th	Night	48% 8% 14% 23% 6% 1	2665
	11th to 20th	Night	54% 8% 16% 17% 5% 1	2835
	21st to end	Night	52% 10% 18% 15% 4	2940
December	1st to 10th	Night	50% 13% 17% 16% 3	4700
	11th to 20th	Night	73% 8% 12% 6% 1	5316
	21st to end	Night	62% 10% 15% 11% 3	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	19% 15% 25% 20% 16% 5%	220
	11th to 20th	Day	18% 7% 17% 31% 19% 8%	220
	21st to end	Day	21% 6% 20% 24% 24% 5%	242
February	1st to 10th	Day	22% 15% 24% 22% 13% 4	299
	11th to 20th	Day	21% 14% 21% 26% 15% 3	484
	21st to end	Day	15% 14% 26% 26% 15% 2	446
March	1st to 10th	Day	16% 14% 28% 22% 16% 3	540
	11th to 20th	Day	16% 13% 23% 24% 16% 8%	540
	21st to end	Day	14% 16% 31% 23% 13% 2	594
April	1st to 10th	Day	14% 16% 26% 22% 15% 8%	540
	11th to 20th	Day	10% 19% 31% 20% 14% 6%	532
	21st to end	Day	9% 15% 28% 24% 17% 7%	540
May	1st to 10th	Day	8% 11% 26% 31% 19% 6%	543
	11th to 20th	Day	14% 10% 25% 23% 17% 11%	568
	21st to end	Day	7% 10% 22% 26% 23% 11%	617
June	1st to 10th	Day	11% 11% 19% 28% 21% 10%	570
	11th to 20th	Day	9% 12% 32% 27% 14% 5%	570
	21st to end	Day	4 7% 25% 30% 21% 12%	570
July	1st to 10th	Day	3 4 19% 40% 28% 7%	566
	11th to 20th	Day	2 4 24% 35% 27% 9%	564
	21st to end	Day	2 5% 17% 32% 29% 15%	619
August	1st to 10th	Day	3 5% 18% 29% 31% 15%	567
	11th to 20th	Day	3 3 14% 29% 35% 15%	557
	21st to end	Day	6% 7% 19% 25% 27% 17%	627
September	1st to 10th	Day	4 3 23% 27% 24% 19%	570
	11th to 20th	Day	8% 8% 22% 26% 24% 13%	543
	21st to end	Day	7% 9% 22% 25% 25% 12%	530
October	1st to 10th	Day	8% 8% 20% 28% 24% 12%	530
	11th to 20th	Day	10% 11% 20% 27% 19% 12%	463
	21st to end	Day	15% 12% 24% 28% 14% 7%	363
November	1st to 10th	Day	18% 13% 25% 23% 17% 4	330
	11th to 20th	Day	20% 15% 21% 22% 14% 8%	272
	21st to end	Day	13% 13% 22% 25% 23% 5%	220
December	1st to 10th	Day	21% 14% 15% 22% 14% 13%	220
	11th to 20th	Day	25% 16% 19% 27% 10% 4	220
	21st to end	Day	27% 10% 20% 24% 15% 4	242
January	1st to 10th	Night	26% 12% 17% 29% 14% 2	840
	11th to 20th	Night	20% 8% 14% 35% 18% 4	840
	21st to end	Night	20% 5% 15% 36% 22% 2	924
February	1st to 10th	Night	21% 11% 20% 32% 14% 3	840
	11th to 20th	Night	17% 10% 20% 32% 19% 2	824
	21st to end	Night	17% 13% 22% 33% 14% 1	692
March	1st to 10th	Night	14% 8% 24% 35% 16% 2	840
	11th to 20th	Night	15% 11% 22% 30% 21% 2	840
	21st to end	Night	14% 11% 30% 33% 11% 1	924
April	1st to 10th	Night	15% 10% 23% 35% 16% 1	840
	11th to 20th	Night	11% 11% 28% 29% 18% 2	818
	21st to end	Night	10% 10% 27% 32% 20% 2	630
May	1st to 10th	Night	6% 10% 22% 37% 23% 2	464
	11th to 20th	Night	9% 5% 22% 32% 27% 4	414
	21st to end	Night	8% 9% 19% 37% 25% 3	455
June	1st to 10th	Night	10% 10% 24% 30% 24% 2	420
	11th to 20th	Night	9% 9% 31% 34% 14% 2	420
	21st to end	Night	5% 6% 23% 36% 26% 2	420
July	1st to 10th	Night	5% 3 18% 40% 31% 2	410
	11th to 20th	Night	3 4 24% 41% 26% 1	408
	21st to end	Night	2 4 18% 40% 33% 3	460
August	1st to 10th	Night	5% 3 14% 40% 35% 4	418
	11th to 20th	Night	3 3 15% 36% 36% 8%	549
	21st to end	Night	4 3 18% 38% 33% 4	924
September	1st to 10th	Night	4 3 16% 40% 30% 6%	840
	11th to 20th	Night	6% 4 17% 32% 34% 7%	812
	21st to end	Night	7% 5% 19% 32% 31% 5%	800
October	1st to 10th	Night	10% 5% 18% 37% 27% 3	800
	11th to 20th	Night	12% 7% 21% 33% 24% 4	800
	21st to end	Night	13% 8% 23% 34% 18% 5%	880
November	1st to 10th	Night	17% 8% 20% 39% 14% 1	820
	11th to 20th	Night	20% 11% 20% 30% 16% 3	840
	21st to end	Night	18% 8% 17% 34% 20% 4	840
December	1st to 10th	Night	17% 8% 17% 36% 18% 4	840
	11th to 20th	Night	24% 12% 15% 35% 13% 1	840
	21st to end	Night	26% 10% 20% 30% 13% 1	924

Page generated at 2026-09-11 01:11:52. Version ac07

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