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 2025-05-11.

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 7% 4 4 4 4 6% 7% 47%	117692
	Night	9% 8% 3 8% 5% 5% 5% 4 6% 7% 41%	119968
Transparency	Day	35% 7% 12% 22% 16% 8%	117461
	Night	41% 7% 12% 20% 14% 6%	119845
Seeing	Day	11% 10% 23% 27% 20% 9%	14878
	Night	14% 8% 20% 34% 21% 3	24112

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	15% 17% 9% 18% 6% 5% 5% 4 5% 5% 12%	3639
	11th to 20th	Day	13% 10% 5% 10% 6% 5% 7% 5% 8% 7% 24%	3616
	21st to end	Day	15% 14% 5% 10% 5% 5% 4 4 6% 7% 25%	4004
February	1st to 10th	Day	13% 15% 6% 11% 5% 6% 6% 3 5% 6% 24%	1675
	11th to 20th	Day	13% 13% 4 11% 5% 4 5% 3 6% 5% 31%	1859
	21st to end	Day	9% 11% 4 10% 6% 5% 6% 4 5% 8% 32%	1650
March	1st to 10th	Day	5% 7% 3 7% 5% 6% 6% 6% 8% 10% 36%	4518
	11th to 20th	Day	6% 7% 3 7% 4 5% 6% 4 6% 7% 45%	4663
	21st to end	Day	10% 9% 3 11% 7% 6% 6% 5% 7% 9% 27%	5969
April	1st to 10th	Day	7% 8% 3 8% 6% 6% 6% 5% 9% 8% 35%	2400
	11th to 20th	Day	5% 7% 2 7% 5% 5% 5% 4 7% 7% 44%	2382
	21st to end	Day	7% 6% 2 6% 5% 4 4 4 6% 8% 47%	2600
May	1st to 10th	Day	8% 5% 1 5% 3 3 4 3 6% 7% 55%	4491
	11th to 20th	Day	4 4 1 4 4 3 4 3 5% 7% 61%	4380
	21st to end	Day	6% 5% 2 6% 5% 6% 7% 6% 7% 8% 43%	4813
June	1st to 10th	Day	10% 6% 2 6% 5% 4 5% 4 6% 7% 45%	2660
	11th to 20th	Day	7% 5% 2 5% 4 4 4 4 6% 8% 52%	2660
	21st to end	Day	3 3 1 4 3 3 4 2 5% 6% 65%	2660
July	1st to 10th	Day	1 1 1 2 1 2 1 2 3 3 83%	4420
	11th to 20th	Day	1 1 1 2 1 2 2 2 2 4 82%	4420
	21st to end	Day	1 1 1 1 2 2 3 4 5% 80%	4790
August	1st to 10th	Day	3 2 1 3 2 2 2 2 4 5% 74%	4401
	11th to 20th	Day	1 1 1 2 2 2 3 3 5% 7% 73%	4109
	21st to end	Day	2 4 1 3 3 3 3 3 4 6% 69%	4180
September	1st to 10th	Day	2 2 1 3 2 2 3 3 4 6% 73%	2280
	11th to 20th	Day	4 4 2 5% 3 5% 5% 4 6% 7% 55%	2200
	21st to end	Day	5% 5% 1 6% 4 3 5% 3 5% 7% 56%	2090
October	1st to 10th	Day	4 3 1 4 3 4 3 3 5% 7% 63%	3305
	11th to 20th	Day	5% 3 2 5% 4 5% 6% 5% 8% 10% 47%	3047
	21st to end	Day	10% 6% 3 6% 4 4 4 5% 7% 9% 42%	3101
November	1st to 10th	Day	14% 7% 3 7% 7% 5% 5% 4 8% 8% 32%	1764
	11th to 20th	Day	13% 13% 5% 11% 6% 7% 6% 4 5% 5% 25%	1697
	21st to end	Day	10% 14% 5% 15% 9% 5% 6% 5% 6% 5% 21%	1600
December	1st to 10th	Day	10% 9% 4 15% 8% 8% 8% 5% 6% 6% 21%	2620
	11th to 20th	Day	16% 17% 7% 18% 8% 5% 5% 3 3 4 14%	3025
	21st to end	Day	17% 12% 7% 13% 8% 7% 5% 4 6% 7% 15%	4004
January	1st to 10th	Night	19% 20% 8% 16% 6% 5% 4 3 4 5% 10%	6306
	11th to 20th	Night	12% 11% 4 8% 5% 6% 6% 5% 8% 9% 26%	6282
	21st to end	Night	12% 12% 5% 12% 6% 5% 5% 4 6% 10% 22%	6952
February	1st to 10th	Night	14% 13% 4 10% 7% 6% 5% 4 5% 6% 27%	2722
	11th to 20th	Night	10% 10% 4 9% 6% 5% 6% 4 6% 8% 33%	2426
	21st to end	Night	9% 11% 4 10% 5% 6% 5% 4 6% 7% 31%	1980
March	1st to 10th	Night	6% 6% 2 8% 5% 5% 5% 5% 7% 10% 40%	5376
	11th to 20th	Night	7% 10% 3 7% 4 4 4 4 5% 6% 45%	5321
	21st to end	Night	7% 8% 4 9% 7% 8% 8% 6% 9% 9% 27%	5006
April	1st to 10th	Night	10% 11% 3 8% 5% 5% 5% 5% 6% 8% 35%	2000
	11th to 20th	Night	8% 7% 3 6% 5% 4 5% 3 5% 7% 47%	1967
	21st to end	Night	6% 7% 2 9% 6% 4 4 4 6% 9% 43%	1800
May	1st to 10th	Night	8% 5% 2 6% 4 4 5% 4 6% 7% 49%	2688
	11th to 20th	Night	5% 4 2 5% 3 3 4 4 6% 8% 56%	2519
	21st to end	Night	6% 5% 2 5% 5% 5% 4 5% 7% 9% 46%	2762
June	1st to 10th	Night	9% 7% 2 4 5% 4 5% 5% 6% 7% 46%	1520
	11th to 20th	Night	8% 6% 3 6% 4 4 4 3 5% 7% 50%	1520
	21st to end	Night	5% 3 2 4 4 4 4 3 4 6% 60%	1520
July	1st to 10th	Night	1 1 1 2 1 1 1 2 4 4 82%	2540
	11th to 20th	Night	1 1 1 1 1 1 1 2 3 5% 82%	2540
	21st to end	Night	1 2 1 2 2 2 1 2 2 4 82%	2762
August	1st to 10th	Night	4 3 1 3 2 2 3 2 4 5% 72%	2529
	11th to 20th	Night	2 3 1 4 2 2 3 3 6% 6% 69%	2722
	21st to end	Night	2 2 1 3 3 3 3 3 4 6% 71%	3498
September	1st to 10th	Night	2 2 1 3 2 2 3 3 4 6% 72%	1900
	11th to 20th	Night	5% 3 1 4 4 4 4 4 5% 7% 58%	1979
	21st to end	Night	5% 3 2 5% 3 3 4 4 6% 8% 58%	2090
October	1st to 10th	Night	5% 3 2 4 3 3 3 3 4 7% 64%	3671
	11th to 20th	Night	7% 4 2 5% 4 5% 5% 3 6% 8% 51%	3886
	21st to end	Night	10% 5% 2 6% 4 5% 5% 4 6% 8% 45%	4457
November	1st to 10th	Night	14% 8% 3 8% 5% 5% 5% 4 6% 7% 35%	2535
	11th to 20th	Night	14% 10% 4 8% 6% 7% 6% 4 6% 6% 29%	2700
	21st to end	Night	13% 10% 3 10% 7% 5% 6% 5% 7% 7% 27%	2800
December	1st to 10th	Night	8% 7% 4 11% 7% 8% 9% 6% 7% 7% 26%	4560
	11th to 20th	Night	17% 18% 7% 16% 7% 6% 5% 4 5% 5% 10%	5180
	21st to end	Night	16% 13% 6% 13% 6% 6% 5% 4 5% 6% 19%	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	71% 10% 12% 6% 1	3639
	11th to 20th	Day	54% 10% 16% 15% 4	3640
	21st to end	Day	55% 8% 12% 18% 7%	4004
February	1st to 10th	Day	58% 9% 18% 10% 4	1675
	11th to 20th	Day	53% 9% 15% 18% 5%	1868
	21st to end	Day	50% 9% 11% 20% 8% 1	1650
March	1st to 10th	Day	38% 8% 14% 25% 15% 1	4518
	11th to 20th	Day	37% 6% 13% 31% 12%	4663
	21st to end	Day	49% 9% 16% 18% 7%	5969
April	1st to 10th	Day	41% 9% 16% 23% 10% 1	2400
	11th to 20th	Day	36% 6% 15% 24% 14% 5%	2382
	21st to end	Day	35% 7% 15% 24% 17% 2	2600
May	1st to 10th	Day	27% 5% 11% 31% 23% 4	4491
	11th to 20th	Day	22% 6% 11% 30% 24% 8%	4383
	21st to end	Day	33% 9% 18% 28% 10% 2	4814
June	1st to 10th	Day	37% 7% 8% 25% 19% 4	2660
	11th to 20th	Day	29% 6% 13% 28% 19% 5%	2660
	21st to end	Day	20% 4 9% 29% 28% 9%	2660
July	1st to 10th	Day	8% 2 5% 14% 27% 44%	4351
	11th to 20th	Day	9% 2 5% 9% 26% 50%	4345
	21st to end	Day	9% 3 5% 17% 33% 32%	4639
August	1st to 10th	Day	14% 3 5% 13% 37% 28%	4384
	11th to 20th	Day	11% 4 7% 36% 31% 11%	4151
	21st to end	Day	17% 4 9% 29% 31% 10%	4179
September	1st to 10th	Day	14% 4 9% 29% 30% 15%	2280
	11th to 20th	Day	26% 6% 13% 23% 23% 8%	2200
	21st to end	Day	28% 6% 14% 30% 18% 5%	2090
October	1st to 10th	Day	23% 4 11% 36% 24% 3	3305
	11th to 20th	Day	31% 7% 20% 29% 13% 1	3047
	21st to end	Day	37% 7% 14% 31% 11% 1	3101
November	1st to 10th	Day	46% 10% 17% 21% 5%	1764
	11th to 20th	Day	59% 8% 16% 14% 2 1	1697
	21st to end	Day	59% 11% 15% 11% 4	1600
December	1st to 10th	Day	57% 11% 18% 12% 2	2620
	11th to 20th	Day	74% 7% 10% 8% 1	3028
	21st to end	Day	63% 11% 14% 11% 1	4004
January	1st to 10th	Night	75% 8% 8% 7% 1	6306
	11th to 20th	Night	51% 10% 18% 15% 6%	6320
	21st to end	Night	52% 11% 12% 17% 8%	6952
February	1st to 10th	Night	56% 8% 16% 14% 5%	2722
	11th to 20th	Night	49% 9% 16% 19% 7%	2428
	21st to end	Night	50% 9% 14% 20% 7% 1	1980
March	1st to 10th	Night	36% 7% 10% 27% 19% 1	5376
	11th to 20th	Night	39% 5% 11% 31% 14%	5322
	21st to end	Night	48% 11% 14% 22% 4 1	5006
April	1st to 10th	Night	45% 8% 15% 22% 10% 1	2000
	11th to 20th	Night	37% 6% 12% 26% 15% 4	1967
	21st to end	Night	36% 8% 14% 19% 19% 4	1800
May	1st to 10th	Night	30% 7% 11% 27% 20% 5%	2688
	11th to 20th	Night	24% 6% 11% 30% 26% 4	2519
	21st to end	Night	30% 10% 20% 29% 10% 1	2762
June	1st to 10th	Night	34% 7% 11% 24% 20% 5%	1520
	11th to 20th	Night	33% 6% 9% 26% 22% 5%	1520
	21st to end	Night	25% 4 9% 23% 27% 12%	1520
July	1st to 10th	Night	8% 2 4 14% 25% 49%	2500
	11th to 20th	Night	7% 2 5% 9% 19% 57%	2492
	21st to end	Night	10% 2 3 13% 30% 42%	2674
August	1st to 10th	Night	17% 3 4 10% 34% 33%	2521
	11th to 20th	Night	17% 4 5% 26% 34% 15%	2746
	21st to end	Night	16% 3 7% 28% 28% 17%	3498
September	1st to 10th	Night	14% 4 8% 23% 30% 21%	1900
	11th to 20th	Night	23% 6% 11% 24% 24% 12%	1979
	21st to end	Night	24% 5% 13% 29% 20% 9%	2090
October	1st to 10th	Night	22% 4 10% 29% 32% 2	3671
	11th to 20th	Night	31% 5% 16% 24% 23% 2	3886
	21st to end	Night	36% 6% 10% 32% 14% 1	4457
November	1st to 10th	Night	47% 8% 14% 24% 6% 1	2535
	11th to 20th	Night	53% 8% 16% 17% 5% 1	2700
	21st to end	Night	52% 10% 18% 16% 4	2800
December	1st to 10th	Night	49% 14% 18% 16% 3	4560
	11th to 20th	Night	74% 8% 12% 6% 1	5176
	21st to end	Night	62% 10% 14% 11% 3	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	20% 14% 23% 23% 17% 5%	200
	11th to 20th	Day	20% 8% 18% 32% 16% 8%	200
	21st to end	Day	24% 6% 22% 23% 21% 5%	220
February	1st to 10th	Day	22% 16% 26% 23% 11% 3	275
	11th to 20th	Day	22% 14% 22% 26% 15% 2	448
	21st to end	Day	15% 15% 25% 27% 16% 2	414
March	1st to 10th	Day	17% 13% 28% 23% 16% 3	500
	11th to 20th	Day	14% 12% 23% 25% 17% 9%	500
	21st to end	Day	14% 16% 32% 23% 13% 2	550
April	1st to 10th	Day	15% 16% 28% 22% 13% 6%	500
	11th to 20th	Day	10% 20% 32% 20% 13% 5%	492
	21st to end	Day	10% 16% 29% 23% 16% 7%	500
May	1st to 10th	Day	8% 11% 27% 30% 18% 6%	503
	11th to 20th	Day	14% 9% 24% 22% 19% 12%	489
	21st to end	Day	8% 10% 23% 26% 24% 9%	529
June	1st to 10th	Day	13% 10% 18% 28% 21% 10%	490
	11th to 20th	Day	11% 12% 31% 27% 14% 5%	490
	21st to end	Day	4 7% 25% 30% 22% 12%	490
July	1st to 10th	Day	2 4 19% 40% 29% 6%	486
	11th to 20th	Day	1 4 22% 35% 29% 9%	484
	21st to end	Day	1 5% 17% 32% 29% 15%	531
August	1st to 10th	Day	3 5% 18% 28% 31% 16%	487
	11th to 20th	Day	2 4 14% 27% 35% 17%	477
	21st to end	Day	6% 7% 19% 26% 26% 16%	539
September	1st to 10th	Day	4 3 23% 29% 23% 18%	490
	11th to 20th	Day	8% 8% 22% 26% 23% 12%	490
	21st to end	Day	7% 9% 23% 26% 25% 10%	490
October	1st to 10th	Day	8% 9% 20% 27% 24% 11%	490
	11th to 20th	Day	10% 11% 19% 27% 20% 13%	427
	21st to end	Day	16% 12% 23% 29% 13% 7%	330
November	1st to 10th	Day	18% 12% 24% 24% 18% 4	300
	11th to 20th	Day	21% 14% 21% 22% 13% 9%	247
	21st to end	Day	13% 13% 22% 24% 24% 5%	200
December	1st to 10th	Day	19% 13% 17% 23% 16% 15%	200
	11th to 20th	Day	24% 16% 18% 29% 10% 5%	200
	21st to end	Day	29% 10% 20% 22% 16% 2	220
January	1st to 10th	Night	27% 12% 17% 28% 15% 2	800
	11th to 20th	Night	21% 9% 15% 34% 17% 4	800
	21st to end	Night	20% 5% 16% 35% 22% 2	880
February	1st to 10th	Night	22% 11% 20% 31% 14% 2	800
	11th to 20th	Night	17% 10% 20% 32% 19% 2	784
	21st to end	Night	17% 13% 21% 33% 14% 1	660
March	1st to 10th	Night	14% 8% 24% 36% 16% 2	800
	11th to 20th	Night	14% 11% 22% 31% 22% 2	800
	21st to end	Night	14% 11% 30% 33% 12% 1	880
April	1st to 10th	Night	16% 10% 24% 34% 16% 1	800
	11th to 20th	Night	11% 11% 29% 28% 19% 2	779
	21st to end	Night	10% 10% 27% 32% 20% 2	600
May	1st to 10th	Night	7% 11% 22% 36% 23% 2	442
	11th to 20th	Night	10% 5% 20% 32% 29% 5%	375
	21st to end	Night	8% 8% 20% 36% 24% 3	411
June	1st to 10th	Night	11% 9% 25% 31% 22% 2	380
	11th to 20th	Night	10% 9% 31% 32% 14% 2	380
	21st to end	Night	5% 6% 23% 35% 28% 3	380
July	1st to 10th	Night	5% 4 19% 40% 30% 2	370
	11th to 20th	Night	3 4 24% 40% 27% 1	368
	21st to end	Night	2 4 18% 39% 33% 3	416
August	1st to 10th	Night	5% 3 14% 40% 34% 4	378
	11th to 20th	Night	3 3 14% 35% 36% 8%	497
	21st to end	Night	4 3 19% 38% 33% 4	836
September	1st to 10th	Night	4 3 17% 40% 30% 6%	760
	11th to 20th	Night	6% 4 18% 31% 34% 7%	760
	21st to end	Night	8% 5% 19% 32% 31% 5%	760
October	1st to 10th	Night	10% 5% 18% 37% 27% 3	760
	11th to 20th	Night	12% 7% 20% 32% 25% 4	760
	21st to end	Night	13% 8% 23% 33% 18% 5%	836
November	1st to 10th	Night	17% 8% 20% 39% 14% 1	780
	11th to 20th	Night	20% 11% 21% 30% 16% 3	800
	21st to end	Night	17% 8% 17% 33% 20% 4	800
December	1st to 10th	Night	16% 7% 16% 37% 19% 5%	800
	11th to 20th	Night	25% 11% 15% 35% 14% 1	800
	21st to end	Night	27% 10% 20% 30% 12% 1	880

Page generated at 2025-05-08 06:33:59. Version ac07

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