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 2024-03-01.

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	8% 7% 3 7% 6% 3 5% 5% 5% 7% 44%	78356
	Night	10% 8% 4 8% 6% 4 5% 5% 5% 7% 38%	81007
Transparency	Day	39% 7% 12% 20% 16% 6%	78083
	Night	44% 8% 13% 18% 12% 5%	80860
Seeing	Day	11% 10% 23% 27% 20% 9%	13339
	Night	14% 8% 20% 34% 21% 3	22623

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% 7% 13% 9% 5% 6% 6% 6% 7% 14%	2539
	11th to 20th	Day	19% 14% 8% 10% 8% 3 5% 6% 6% 6% 15%	2516
	21st to end	Day	20% 18% 8% 13% 8% 4 5% 4 4 5% 11%	2794
February	1st to 10th	Day	13% 14% 6% 9% 6% 4 7% 5% 5% 7% 24%	1591
	11th to 20th	Day	13% 12% 4 10% 7% 3 5% 4 6% 6% 31%	1763
	21st to end	Day	9% 10% 5% 9% 7% 4 6% 5% 5% 8% 32%	1570
March	1st to 10th	Day	10% 9% 4 7% 8% 4 6% 7% 7% 8% 31%	1801
	11th to 20th	Day	9% 8% 4 8% 7% 5% 7% 7% 5% 7% 32%	1838
	21st to end	Day	12% 8% 3 8% 8% 4 7% 7% 8% 7% 28%	2376
April	1st to 10th	Day	7% 8% 3 7% 7% 4 6% 6% 9% 9% 34%	2160
	11th to 20th	Day	6% 7% 3 7% 5% 4 5% 6% 7% 7% 43%	2140
	21st to end	Day	7% 6% 3 6% 5% 3 5% 4 6% 8% 46%	2340
May	1st to 10th	Day	5% 5% 1 5% 4 3 5% 5% 6% 8% 53%	2479
	11th to 20th	Day	7% 5% 3 6% 7% 4 6% 6% 6% 9% 42%	2477
	21st to end	Day	7% 5% 3 6% 5% 4 6% 6% 6% 8% 45%	2723
June	1st to 10th	Day	10% 6% 3 6% 5% 3 5% 5% 6% 7% 45%	2520
	11th to 20th	Day	7% 4 2 4 5% 2 5% 5% 6% 8% 52%	2520
	21st to end	Day	3 3 1 4 3 3 4 3 5% 7% 65%	2520
July	1st to 10th	Day	2 2 1 2 2 1 2 3 4 6% 75%	2520
	11th to 20th	Day	1 2 1 2 2 1 3 3 3 5% 76%	2520
	21st to end	Day	1 1 1 1 1 2 2 3 4 83%	2741
August	1st to 10th	Day	3 2 1 2 2 1 3 2 3 5% 76%	2507
	11th to 20th	Day	2 1 1 2 3 1 2 2 4 6% 75%	2358
	21st to end	Day	3 4 1 2 3 2 3 4 4 7% 66%	2376
September	1st to 10th	Day	2 2 1 3 3 1 2 4 4 6% 73%	2160
	11th to 20th	Day	4 4 2 4 4 4 4 6% 6% 7% 56%	2085
	21st to end	Day	5% 5% 2 5% 5% 2 4 5% 5% 7% 55%	1980
October	1st to 10th	Day	6% 4 2 5% 5% 3 4 4 6% 7% 54%	1873
	11th to 20th	Day	8% 4 2 4 4 3 5% 6% 7% 9% 48%	1741
	21st to end	Day	11% 7% 3 6% 5% 3 5% 6% 7% 8% 40%	1782
November	1st to 10th	Day	14% 7% 3 6% 8% 4 5% 5% 8% 8% 32%	1674
	11th to 20th	Day	13% 12% 6% 9% 8% 5% 6% 6% 4 6% 25%	1613
	21st to end	Day	11% 13% 5% 12% 10% 4 6% 6% 5% 6% 22%	1520
December	1st to 10th	Day	13% 12% 5% 12% 8% 5% 7% 6% 5% 6% 20%	1520
	11th to 20th	Day	14% 16% 9% 20% 11% 4 5% 4 3 4 11%	1925
	21st to end	Day	14% 12% 8% 13% 10% 6% 6% 5% 6% 7% 13%	2794
January	1st to 10th	Night	17% 16% 6% 11% 8% 4 5% 5% 5% 6% 15%	4406
	11th to 20th	Night	18% 15% 6% 8% 6% 4 5% 5% 5% 8% 19%	4382
	21st to end	Night	17% 14% 7% 15% 10% 5% 6% 6% 4 5% 13%	4862
February	1st to 10th	Night	14% 12% 4 9% 7% 4 5% 5% 5% 7% 28%	2586
	11th to 20th	Night	10% 10% 4 8% 7% 4 6% 5% 5% 8% 33%	2302
	21st to end	Night	9% 11% 4 9% 7% 4 6% 5% 6% 8% 30%	1884
March	1st to 10th	Night	11% 9% 3 8% 7% 4 5% 6% 6% 7% 34%	2165
	11th to 20th	Night	9% 8% 4 5% 5% 4 6% 6% 7% 8% 37%	2119
	21st to end	Night	10% 9% 4 7% 7% 5% 7% 8% 8% 8% 29%	1980
April	1st to 10th	Night	10% 10% 3 6% 7% 4 5% 6% 6% 8% 34%	1800
	11th to 20th	Night	8% 6% 4 5% 6% 3 5% 5% 5% 7% 45%	1769
	21st to end	Night	6% 7% 3 8% 6% 3 5% 5% 6% 9% 41%	1620
May	1st to 10th	Night	5% 3 2 5% 6% 4 5% 6% 7% 7% 51%	1478
	11th to 20th	Night	7% 5% 2 6% 6% 2 4 6% 7% 9% 45%	1416
	21st to end	Night	5% 6% 3 6% 6% 4 6% 7% 8% 9% 42%	1552
June	1st to 10th	Night	9% 6% 2 4 5% 3 5% 6% 6% 8% 46%	1440
	11th to 20th	Night	8% 5% 3 5% 5% 3 4 4 5% 7% 50%	1440
	21st to end	Night	5% 3 2 3 4 3 3 4 4 6% 61%	1440
July	1st to 10th	Night	2 2 1 2 2 1 3 4 5% 6% 72%	1440
	11th to 20th	Night	2 1 1 2 2 2 2 3 4 7% 74%	1440
	21st to end	Night	1 1 1 1 2 1 2 3 3 5% 81%	1576
August	1st to 10th	Night	4 2 1 2 2 2 2 3 4 6% 73%	1432
	11th to 20th	Night	1 2 1 3 3 2 3 3 4 5% 74%	1537
	21st to end	Night	2 2 1 2 3 2 3 4 4 6% 70%	1980
September	1st to 10th	Night	2 2 1 2 2 2 3 4 4 6% 72%	1800
	11th to 20th	Night	4 3 1 4 5% 3 4 5% 5% 7% 59%	1874
	21st to end	Night	6% 4 2 5% 4 2 5% 5% 6% 8% 57%	1980
October	1st to 10th	Night	8% 4 3 4 5% 3 4 4 5% 8% 52%	2083
	11th to 20th	Night	9% 5% 2 5% 5% 3 5% 4 5% 7% 50%	2218
	21st to end	Night	10% 5% 3 6% 5% 4 5% 5% 5% 9% 43%	2574
November	1st to 10th	Night	14% 7% 4 8% 6% 4 5% 5% 6% 7% 35%	2405
	11th to 20th	Night	14% 9% 4 7% 6% 5% 7% 5% 6% 7% 30%	2565
	21st to end	Night	13% 9% 4 9% 8% 4 6% 7% 6% 8% 28%	2660
December	1st to 10th	Night	13% 10% 5% 11% 9% 4 5% 5% 6% 7% 24%	2660
	11th to 20th	Night	16% 17% 7% 16% 10% 4 4 5% 5% 5% 12%	3280
	21st to end	Night	15% 12% 7% 13% 8% 4 5% 6% 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	48% 9% 17% 20% 6%	1801
	11th to 20th	Day	49% 7% 15% 22% 6%	1838
	21st to end	Day	50% 11% 17% 18% 4	2376
April	1st to 10th	Day	42% 9% 16% 22% 10% 1	2160
	11th to 20th	Day	38% 6% 15% 24% 13% 4	2140
	21st to end	Day	36% 7% 15% 23% 17% 2	2340
May	1st to 10th	Day	29% 5% 13% 30% 21% 2	2479
	11th to 20th	Day	36% 8% 14% 24% 15% 3	2480
	21st to end	Day	35% 8% 14% 27% 13% 3	2724
June	1st to 10th	Day	38% 7% 9% 25% 18% 4	2520
	11th to 20th	Day	29% 6% 13% 28% 19% 4	2520
	21st to end	Day	20% 4 9% 30% 28% 9%	2520
July	1st to 10th	Day	12% 2 8% 23% 33% 21%	2451
	11th to 20th	Day	12% 3 8% 15% 36% 27%	2445
	21st to end	Day	8% 2 4 16% 42% 29%	2589
August	1st to 10th	Day	13% 3 8% 18% 38% 20%	2490
	11th to 20th	Day	12% 3 8% 23% 36% 18%	2358
	21st to end	Day	17% 4 8% 28% 32% 11%	2376
September	1st to 10th	Day	14% 4 9% 30% 30% 15%	2160
	11th to 20th	Day	25% 6% 13% 23% 24% 9%	2085
	21st to end	Day	29% 6% 14% 29% 18% 5%	1980
October	1st to 10th	Day	30% 6% 14% 30% 18% 2	1873
	11th to 20th	Day	30% 8% 18% 31% 12% 1	1741
	21st to end	Day	40% 8% 19% 24% 8% 1	1782
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	50% 9% 13% 20% 7% 1	1884
March	1st to 10th	Night	47% 8% 13% 22% 9% 1	2165
	11th to 20th	Night	43% 7% 16% 24% 10%	2120
	21st to end	Night	49% 10% 16% 20% 6%	1980
April	1st to 10th	Night	46% 8% 14% 22% 10% 1	1800
	11th to 20th	Night	39% 6% 13% 25% 14% 4	1769
	21st to end	Night	38% 7% 14% 19% 17% 5%	1620
May	1st to 10th	Night	29% 7% 11% 29% 20% 4	1478
	11th to 20th	Night	33% 7% 13% 25% 18% 4	1416
	21st to end	Night	34% 9% 13% 28% 13% 2	1552
June	1st to 10th	Night	34% 7% 12% 24% 20% 4	1440
	11th to 20th	Night	34% 6% 9% 26% 22% 4	1440
	21st to end	Night	25% 4 9% 23% 27% 12%	1440
July	1st to 10th	Night	13% 3 6% 20% 32% 26%	1400
	11th to 20th	Night	12% 3 9% 16% 28% 33%	1392
	21st to end	Night	9% 2 4 11% 36% 39%	1488
August	1st to 10th	Night	14% 3 6% 15% 36% 26%	1424
	11th to 20th	Night	15% 4 5% 18% 33% 25%	1537
	21st to end	Night	16% 3 8% 22% 34% 17%	1980
September	1st to 10th	Night	14% 4 8% 23% 31% 19%	1800
	11th to 20th	Night	23% 6% 10% 23% 25% 13%	1874
	21st to end	Night	25% 5% 13% 28% 20% 9%	1980
October	1st to 10th	Night	31% 6% 12% 27% 23% 2	2083
	11th to 20th	Night	34% 6% 13% 26% 19% 3	2218
	21st to end	Night	38% 8% 13% 26% 13% 2	2574
November	1st to 10th	Night	48% 8% 13% 24% 6% 1	2405
	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% 14% 26% 26% 15% 3	382
March	1st to 10th	Day	18% 13% 28% 21% 16% 4	421
	11th to 20th	Day	14% 11% 23% 27% 18% 7%	420
	21st to end	Day	14% 16% 32% 23% 13% 2	462
April	1st to 10th	Day	16% 15% 29% 22% 13% 6%	420
	11th to 20th	Day	11% 21% 32% 20% 12% 6%	412
	21st to end	Day	11% 16% 29% 23% 16% 5%	420
May	1st to 10th	Day	8% 12% 26% 31% 18% 5%	423
	11th to 20th	Day	15% 8% 23% 23% 19% 13%	448
	21st to end	Day	8% 9% 22% 26% 25% 9%	485
June	1st to 10th	Day	12% 10% 19% 28% 20% 11%	450
	11th to 20th	Day	11% 12% 31% 27% 13% 6%	450
	21st to end	Day	4 6% 25% 30% 22% 12%	450
July	1st to 10th	Day	3 4 17% 41% 29% 6%	446
	11th to 20th	Day	1 4 23% 35% 28% 8%	444
	21st to end	Day	1 4 18% 32% 29% 16%	487
August	1st to 10th	Day	3 4 17% 28% 30% 17%	447
	11th to 20th	Day	2 3 14% 26% 36% 18%	437
	21st to end	Day	6% 7% 18% 27% 27% 15%	495
September	1st to 10th	Day	4 3 24% 30% 23% 15%	450
	11th to 20th	Day	7% 8% 22% 25% 25% 13%	450
	21st to end	Day	7% 10% 23% 26% 25% 10%	450
October	1st to 10th	Day	9% 9% 20% 28% 24% 11%	450
	11th to 20th	Day	11% 11% 18% 27% 20% 13%	391
	21st to end	Day	16% 12% 24% 27% 12% 8%	297
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	17% 13% 21% 34% 14% 1	628
March	1st to 10th	Night	15% 8% 24% 35% 16% 3	722
	11th to 20th	Night	14% 10% 21% 31% 22% 2	720
	21st to end	Night	15% 10% 30% 32% 11% 1	792
April	1st to 10th	Night	16% 9% 24% 33% 16% 1	720
	11th to 20th	Night	12% 11% 29% 28% 18% 2	701
	21st to end	Night	11% 10% 27% 31% 19% 2	540
May	1st to 10th	Night	7% 11% 23% 35% 23% 2	398
	11th to 20th	Night	10% 5% 19% 32% 29% 5%	354
	21st to end	Night	8% 8% 19% 37% 25% 3	389
June	1st to 10th	Night	12% 8% 25% 31% 22% 2	360
	11th to 20th	Night	11% 9% 31% 33% 14% 2	360
	21st to end	Night	5% 5% 23% 36% 28% 3	360
July	1st to 10th	Night	5% 4 19% 39% 31% 2	350
	11th to 20th	Night	3 4 26% 39% 26% 1	348
	21st to end	Night	1 4 19% 39% 34% 3	394
August	1st to 10th	Night	5% 3 14% 38% 35% 4	358
	11th to 20th	Night	3 2 14% 34% 37% 9%	469
	21st to end	Night	4 3 19% 38% 32% 4	792
September	1st to 10th	Night	4 3 18% 41% 28% 6%	720
	11th to 20th	Night	6% 4 18% 30% 35% 7%	720
	21st to end	Night	8% 5% 19% 32% 31% 5%	720
October	1st to 10th	Night	11% 6% 18% 36% 27% 3	720
	11th to 20th	Night	12% 7% 21% 31% 25% 4	720
	21st to end	Night	13% 8% 22% 33% 18% 5%	792
November	1st to 10th	Night	18% 7% 20% 39% 14% 1	740
	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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