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 2024-11-01.

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 5% 7% 49%	101498
	Night	9% 8% 3 8% 5% 4 4 4 5% 7% 42%	97531
Transparency	Day	34% 7% 12% 21% 17% 10%	101267
	Night	40% 7% 12% 19% 14% 8%	97408
Seeing	Day	11% 10% 23% 27% 20% 9%	14303
	Night	14% 8% 20% 34% 21% 3	23378

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% 15% 6% 15% 7% 7% 6% 5% 6% 6% 14%	2539
	11th to 20th	Day	19% 15% 7% 12% 6% 5% 5% 4 6% 6% 15%	2516
	21st to end	Day	20% 18% 7% 14% 7% 6% 4 3 4 5% 11%	2794
February	1st to 10th	Day	13% 14% 6% 11% 5% 6% 6% 4 5% 7% 24%	1591
	11th to 20th	Day	13% 12% 4 11% 5% 4 5% 3 6% 6% 31%	1763
	21st to end	Day	9% 12% 4 10% 6% 5% 6% 4 5% 8% 32%	1570
March	1st to 10th	Day	7% 8% 3 7% 5% 5% 6% 6% 8% 10% 36%	3138
	11th to 20th	Day	5% 5% 2 6% 4 4 5% 4 5% 7% 52%	3257
	21st to end	Day	10% 9% 3 9% 7% 6% 7% 5% 8% 8% 28%	4165
April	1st to 10th	Day	7% 9% 3 8% 6% 6% 5% 5% 9% 8% 34%	2280
	11th to 20th	Day	5% 8% 2 7% 5% 5% 5% 5% 7% 7% 44%	2261
	21st to end	Day	7% 6% 2 6% 5% 5% 4 4 6% 8% 46%	2470
May	1st to 10th	Day	8% 5% 1 5% 3 3 4 3 6% 7% 55%	4353
	11th to 20th	Day	4 4 1 4 4 3 4 3 5% 7% 61%	4377
	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	6% 4 2 5% 4 4 3 3 6% 7% 55%	1977
	11th to 20th	Day	8% 3 2 5% 4 5% 5% 4 7% 9% 48%	1837
	21st to end	Day	11% 7% 3 7% 5% 5% 4 5% 6% 8% 40%	1881
November	1st to 10th	Day	14% 7% 3 7% 7% 5% 5% 4 8% 8% 32%	1674
	11th to 20th	Day	12% 13% 5% 11% 6% 7% 6% 4 5% 5% 25%	1613
	21st to end	Day	10% 13% 5% 14% 9% 5% 5% 5% 6% 6% 22%	1520
December	1st to 10th	Day	13% 14% 4 14% 8% 7% 6% 5% 5% 5% 20%	1520
	11th to 20th	Day	14% 17% 9% 22% 8% 5% 4 3 3 4 11%	1925
	21st to end	Day	14% 13% 8% 15% 8% 7% 6% 4 6% 7% 13%	2794
January	1st to 10th	Night	17% 17% 6% 13% 7% 6% 5% 4 5% 6% 15%	4406
	11th to 20th	Night	18% 16% 5% 9% 6% 5% 5% 4 5% 8% 19%	4382
	21st to end	Night	16% 14% 6% 16% 8% 6% 5% 4 4 5% 13%	4862
February	1st to 10th	Night	14% 13% 4 10% 6% 5% 4 4 5% 7% 28%	2586
	11th to 20th	Night	10% 10% 4 9% 6% 5% 6% 4 6% 8% 33%	2302
	21st to end	Night	9% 12% 4 10% 6% 6% 5% 4 6% 7% 30%	1884
March	1st to 10th	Night	7% 8% 2 8% 6% 5% 5% 5% 7% 11% 37%	3736
	11th to 20th	Night	6% 6% 2 5% 3 3 4 4 5% 6% 54%	3707
	21st to end	Night	7% 7% 4 9% 7% 8% 9% 7% 9% 8% 26%	3488
April	1st to 10th	Night	10% 11% 3 7% 6% 5% 5% 5% 6% 8% 34%	1900
	11th to 20th	Night	8% 7% 3 6% 5% 4 5% 4 5% 7% 46%	1868
	21st to end	Night	6% 8% 2 9% 6% 4 4 4 7% 9% 41%	1710
May	1st to 10th	Night	8% 5% 2 6% 4 4 5% 4 6% 7% 49%	2606
	11th to 20th	Night	5% 4 2 5% 3 3 4 4 6% 8% 56%	2516
	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	8% 4 2 5% 4 4 3 4 5% 7% 53%	2199
	11th to 20th	Night	9% 5% 2 5% 5% 4 5% 3 6% 7% 50%	2342
	21st to end	Night	10% 6% 3 7% 4 5% 5% 3 5% 8% 44%	2717
November	1st to 10th	Night	14% 8% 3 8% 5% 5% 5% 4 6% 7% 35%	2411
	11th to 20th	Night	14% 10% 4 8% 6% 7% 6% 4 6% 6% 30%	2565
	21st to end	Night	12% 10% 3 10% 7% 5% 6% 5% 7% 7% 27%	2660
December	1st to 10th	Night	13% 11% 5% 12% 8% 5% 5% 5% 6% 7% 24%	2660
	11th to 20th	Night	16% 18% 7% 18% 8% 5% 4 3 5% 5% 12%	3280
	21st to end	Night	15% 13% 6% 15% 7% 6% 5% 5% 6% 6% 17%	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	65% 12% 14% 7% 1	2539
	11th to 20th	Day	67% 9% 12% 9% 2	2540
	21st to end	Day	72% 9% 11% 7% 1	2794
February	1st to 10th	Day	58% 9% 19% 10% 4	1591
	11th to 20th	Day	52% 9% 15% 18% 5%	1772
	21st to end	Day	51% 10% 11% 20% 8% 1	1570
March	1st to 10th	Day	38% 8% 14% 26% 13%	3138
	11th to 20th	Day	31% 6% 15% 37% 11%	3257
	21st to end	Day	48% 11% 17% 15% 8%	4165
April	1st to 10th	Day	42% 9% 16% 22% 10% 1	2280
	11th to 20th	Day	37% 6% 15% 23% 13% 5%	2261
	21st to end	Day	36% 7% 15% 23% 17% 2	2470
May	1st to 10th	Day	27% 5% 11% 31% 22% 4	4353
	11th to 20th	Day	22% 6% 11% 30% 24% 8%	4380
	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	29% 5% 14% 30% 19% 2	1977
	11th to 20th	Day	30% 8% 18% 30% 12% 1	1837
	21st to end	Day	39% 8% 19% 25% 8% 1	1881
November	1st to 10th	Day	46% 10% 16% 21% 5%	1674
	11th to 20th	Day	59% 8% 16% 14% 3 1	1613
	21st to end	Day	58% 11% 16% 11% 4	1520
December	1st to 10th	Day	62% 9% 11% 14% 3	1520
	11th to 20th	Day	76% 8% 10% 5% 1	1928
	21st to end	Day	63% 13% 13% 10% 2	2794
January	1st to 10th	Night	67% 10% 11% 10% 1	4406
	11th to 20th	Night	62% 9% 16% 10% 3	4420
	21st to end	Night	65% 13% 12% 7% 1	4862
February	1st to 10th	Night	55% 8% 17% 14% 5% 1	2586
	11th to 20th	Night	49% 9% 16% 19% 7%	2304
	21st to end	Night	51% 9% 13% 20% 7% 1	1884
March	1st to 10th	Night	38% 8% 12% 28% 14% 1	3736
	11th to 20th	Night	30% 5% 13% 36% 16%	3708
	21st to end	Night	47% 13% 16% 19% 4 1	3488
April	1st to 10th	Night	46% 8% 15% 22% 9% 1	1900
	11th to 20th	Night	38% 6% 13% 25% 14% 4	1868
	21st to end	Night	37% 8% 15% 19% 18% 4	1710
May	1st to 10th	Night	31% 7% 11% 27% 19% 5%	2606
	11th to 20th	Night	24% 6% 11% 30% 26% 4	2516
	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	30% 5% 12% 27% 25% 2	2199
	11th to 20th	Night	34% 6% 13% 25% 19% 3	2342
	21st to end	Night	37% 8% 13% 26% 14% 2	2717
November	1st to 10th	Night	48% 8% 13% 24% 6% 1	2411
	11th to 20th	Night	53% 8% 16% 17% 5% 1	2565
	21st to end	Night	51% 10% 18% 17% 4	2660
December	1st to 10th	Night	57% 9% 14% 16% 3	2660
	11th to 20th	Night	72% 8% 12% 7% 1	3276
	21st to end	Night	62% 10% 13% 11% 4	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	20% 14% 23% 21% 17% 6%	180
	11th to 20th	Day	22% 7% 17% 34% 13% 7%	180
	21st to end	Day	26% 6% 23% 23% 18% 4	198
February	1st to 10th	Day	23% 16% 24% 24% 10% 3	251
	11th to 20th	Day	22% 15% 23% 25% 14% 2	412
	21st to end	Day	15% 15% 26% 26% 15% 3	382
March	1st to 10th	Day	18% 13% 28% 21% 17% 3	460
	11th to 20th	Day	13% 12% 22% 26% 18% 10%	460
	21st to end	Day	14% 16% 31% 24% 13% 2	506
April	1st to 10th	Day	15% 17% 27% 22% 13% 6%	460
	11th to 20th	Day	10% 21% 32% 19% 13% 6%	452
	21st to end	Day	10% 17% 30% 23% 15% 5%	460
May	1st to 10th	Day	8% 12% 27% 30% 17% 5%	463
	11th to 20th	Day	14% 9% 24% 22% 19% 12%	488
	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% 28% 13% 7%	330
November	1st to 10th	Day	18% 13% 24% 24% 17% 4	270
	11th to 20th	Day	20% 14% 20% 22% 15% 9%	223
	21st to end	Day	13% 12% 21% 24% 24% 6%	180
December	1st to 10th	Day	20% 14% 17% 23% 12% 13%	180
	11th to 20th	Day	22% 16% 19% 29% 9% 5%	180
	21st to end	Day	29% 8% 21% 22% 18% 3	198
January	1st to 10th	Night	26% 12% 17% 27% 15% 2	760
	11th to 20th	Night	22% 9% 15% 33% 18% 4	760
	21st to end	Night	21% 5% 16% 35% 22% 2	836
February	1st to 10th	Night	21% 11% 20% 32% 14% 2	760
	11th to 20th	Night	17% 10% 20% 32% 19% 2	744
	21st to end	Night	16% 13% 21% 34% 14% 1	628
March	1st to 10th	Night	14% 8% 24% 35% 16% 3	760
	11th to 20th	Night	13% 10% 21% 31% 23% 2	760
	21st to end	Night	15% 10% 30% 33% 12% 1	836
April	1st to 10th	Night	16% 10% 24% 33% 16% 1	760
	11th to 20th	Night	12% 11% 29% 28% 18% 2	740
	21st to end	Night	11% 10% 27% 31% 19% 2	570
May	1st to 10th	Night	7% 11% 23% 35% 22% 2	420
	11th to 20th	Night	10% 5% 20% 32% 29% 5%	374
	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	18% 7% 20% 39% 15% 1	742
	11th to 20th	Night	20% 10% 20% 30% 16% 3	760
	21st to end	Night	17% 8% 17% 34% 20% 4	760
December	1st to 10th	Night	17% 8% 17% 37% 17% 4	760
	11th to 20th	Night	24% 11% 15% 35% 14% 1	760
	21st to end	Night	27% 9% 19% 30% 13% 1	836

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