Summer Village of Yellowstone
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Summer Village of Yellowstone clear sky chart from 2005-11-06 to 2024-04-03.

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	10% 9% 4 7% 7% 4 6% 6% 6% 8% 34%	78552
	Night	8% 10% 4 9% 8% 4 6% 5% 6% 8% 32%	81484
Transparency	Day	46% 8% 17% 21% 7% 1	78248
	Night	48% 8% 15% 19% 9% 1	81369
Seeing	Day	13% 7% 25% 31% 19% 6%	15056
	Night	13% 5% 28% 35% 16% 2	23764

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	4 14% 5% 12% 10% 4 5% 6% 6% 9% 25%	2188
	11th to 20th	Day	6% 10% 4 7% 7% 3 5% 7% 7% 9% 33%	2199
	21st to end	Day	7% 12% 4 8% 7% 4 5% 6% 6% 7% 34%	2666
February	1st to 10th	Day	9% 12% 6% 9% 9% 5% 6% 6% 8% 8% 21%	1520
	11th to 20th	Day	5% 13% 6% 9% 9% 5% 6% 6% 6% 8% 28%	1576
	21st to end	Day	4 11% 6% 10% 10% 6% 6% 7% 7% 7% 25%	1494
March	1st to 10th	Day	7% 14% 6% 9% 9% 6% 6% 5% 5% 8% 25%	1900
	11th to 20th	Day	8% 10% 6% 7% 6% 4 5% 6% 7% 8% 33%	2038
	21st to end	Day	9% 14% 6% 10% 8% 4 6% 6% 7% 7% 22%	2367
April	1st to 10th	Day	7% 11% 4 9% 7% 5% 7% 6% 6% 8% 30%	2250
	11th to 20th	Day	11% 10% 4 8% 7% 4 6% 6% 6% 7% 30%	2310
	21st to end	Day	10% 11% 3 7% 7% 4 5% 6% 6% 8% 31%	2354
May	1st to 10th	Day	11% 10% 4 8% 8% 4 6% 7% 7% 7% 28%	2636
	11th to 20th	Day	9% 6% 2 6% 6% 4 6% 5% 7% 8% 41%	2654
	21st to end	Day	18% 8% 3 5% 6% 3 6% 5% 6% 8% 34%	2917
June	1st to 10th	Day	17% 8% 3 7% 7% 4 5% 6% 6% 7% 31%	2718
	11th to 20th	Day	19% 8% 4 7% 8% 5% 6% 6% 6% 7% 25%	2880
	21st to end	Day	10% 6% 3 6% 6% 4 6% 6% 7% 9% 39%	2880
July	1st to 10th	Day	12% 6% 2 7% 5% 4 5% 6% 7% 8% 39%	2880
	11th to 20th	Day	10% 5% 2 6% 7% 4 6% 6% 7% 11% 36%	2700
	21st to end	Day	10% 4 2 5% 5% 3 6% 5% 7% 9% 45%	2938
August	1st to 10th	Day	9% 5% 2 5% 6% 4 5% 6% 8% 11% 38%	2548
	11th to 20th	Day	8% 5% 2 5% 5% 3 5% 5% 7% 11% 45%	2408
	21st to end	Day	11% 6% 2 5% 7% 4 6% 6% 6% 8% 40%	2574
September	1st to 10th	Day	12% 7% 3 6% 6% 3 4 5% 6% 8% 41%	2265
	11th to 20th	Day	14% 7% 3 5% 5% 2 5% 4 5% 9% 42%	1998
	21st to end	Day	9% 6% 3 8% 5% 3 5% 5% 6% 9% 41%	1980
October	1st to 10th	Day	11% 10% 3 8% 7% 3 4 5% 5% 6% 38%	1890
	11th to 20th	Day	10% 9% 5% 7% 7% 3 4 5% 6% 7% 36%	1620
	21st to end	Day	9% 12% 5% 7% 7% 4 5% 6% 6% 7% 31%	1782
November	1st to 10th	Day	11% 14% 6% 9% 7% 4 5% 5% 5% 8% 25%	1484
	11th to 20th	Day	8% 12% 4 9% 8% 4 5% 4 5% 7% 33%	1330
	21st to end	Day	6% 10% 6% 11% 9% 5% 6% 5% 5% 7% 30%	1330
December	1st to 10th	Day	6% 11% 5% 11% 8% 6% 7% 6% 4 7% 28%	1330
	11th to 20th	Day	6% 11% 6% 11% 8% 5% 7% 5% 5% 8% 28%	1682
	21st to end	Day	5% 7% 4 7% 7% 4 6% 6% 7% 9% 39%	2266
January	1st to 10th	Night	4 12% 5% 13% 11% 5% 5% 5% 6% 7% 27%	4730
	11th to 20th	Night	5% 8% 4 10% 10% 5% 7% 7% 7% 7% 32%	4699
	21st to end	Night	7% 13% 5% 9% 7% 4 5% 5% 5% 8% 32%	5019
February	1st to 10th	Night	6% 11% 6% 13% 9% 6% 6% 5% 6% 6% 26%	2660
	11th to 20th	Night	5% 11% 6% 11% 10% 5% 6% 6% 5% 7% 28%	2489
	21st to end	Night	6% 10% 5% 9% 9% 4 7% 7% 6% 8% 28%	1958
March	1st to 10th	Night	7% 10% 5% 10% 9% 5% 6% 6% 7% 7% 28%	2280
	11th to 20th	Night	8% 9% 5% 8% 8% 4 6% 6% 7% 8% 31%	2141
	21st to end	Night	8% 13% 6% 10% 7% 4 6% 5% 5% 8% 26%	2228
April	1st to 10th	Night	8% 9% 4 8% 9% 5% 7% 6% 6% 8% 28%	1754
	11th to 20th	Night	9% 11% 4 8% 8% 5% 7% 5% 5% 8% 29%	1601
	21st to end	Night	13% 9% 4 7% 5% 3 5% 5% 7% 8% 34%	1603
May	1st to 10th	Night	11% 12% 5% 9% 8% 4 5% 6% 6% 8% 27%	1324
	11th to 20th	Night	9% 8% 3 8% 7% 3 4 5% 7% 7% 38%	1239
	21st to end	Night	19% 8% 4 7% 6% 4 5% 5% 5% 7% 31%	1358
June	1st to 10th	Night	15% 10% 4 7% 6% 4 6% 6% 6% 7% 30%	1238
	11th to 20th	Night	16% 8% 3 9% 7% 4 9% 8% 8% 9% 19%	1080
	21st to end	Night	11% 5% 3 7% 5% 4 6% 8% 7% 10% 34%	1080
July	1st to 10th	Night	13% 7% 2 5% 5% 3 5% 4 7% 10% 38%	1080
	11th to 20th	Night	11% 5% 3 7% 7% 4 6% 7% 9% 9% 33%	1257
	21st to end	Night	11% 4 2 5% 6% 4 5% 5% 7% 10% 41%	1379
August	1st to 10th	Night	10% 6% 3 6% 7% 3 6% 7% 7% 9% 37%	1389
	11th to 20th	Night	10% 6% 3 5% 5% 3 6% 5% 7% 10% 41%	1491
	21st to end	Night	12% 5% 3 6% 6% 2 5% 7% 6% 9% 39%	1782
September	1st to 10th	Night	13% 6% 2 5% 5% 3 5% 5% 6% 8% 42%	1692
	11th to 20th	Night	12% 8% 2 5% 5% 3 4 4 6% 8% 44%	1962
	21st to end	Night	10% 8% 2 6% 5% 3 5% 4 6% 8% 43%	1980
October	1st to 10th	Night	12% 8% 4 7% 6% 4 5% 4 5% 7% 38%	2069
	11th to 20th	Night	10% 9% 4 7% 6% 3 5% 5% 6% 7% 38%	2340
	21st to end	Night	8% 11% 4 8% 8% 5% 5% 6% 7% 7% 33%	2574
November	1st to 10th	Night	14% 15% 5% 9% 7% 3 5% 6% 5% 6% 25%	2574
	11th to 20th	Night	8% 12% 6% 11% 8% 4 6% 5% 5% 7% 28%	2850
	21st to end	Night	7% 10% 6% 10% 9% 5% 6% 5% 6% 8% 28%	2850
December	1st to 10th	Night	9% 12% 4 10% 9% 4 4 5% 6% 7% 30%	2850
	11th to 20th	Night	8% 14% 6% 10% 7% 4 6% 5% 6% 7% 28%	3510
	21st to end	Night	3 8% 3 8% 7% 4 5% 5% 6% 9% 42%	5374

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	54% 7% 14% 18% 6% 1	2188
	11th to 20th	Day	45% 5% 13% 13% 22% 1	2220
	21st to end	Day	47% 8% 21% 18% 6%	2666
February	1st to 10th	Day	56% 6% 16% 13% 8% 1	1520
	11th to 20th	Day	52% 9% 14% 17% 8%	1584
	21st to end	Day	55% 8% 12% 18% 7%	1494
March	1st to 10th	Day	57% 6% 15% 16% 5%	1900
	11th to 20th	Day	46% 7% 14% 22% 10% 1	2039
	21st to end	Day	56% 10% 15% 15% 4	2367
April	1st to 10th	Day	49% 9% 16% 18% 8% 1	2250
	11th to 20th	Day	50% 8% 14% 21% 7%	2310
	21st to end	Day	49% 7% 13% 22% 7% 1	2354
May	1st to 10th	Day	51% 8% 14% 17% 9% 1	2636
	11th to 20th	Day	37% 8% 14% 30% 11% 1	2658
	21st to end	Day	48% 8% 14% 19% 11%	2918
June	1st to 10th	Day	51% 7% 16% 20% 7%	2718
	11th to 20th	Day	55% 10% 14% 15% 5%	2880
	21st to end	Day	39% 11% 20% 24% 5% 1	2880
July	1st to 10th	Day	41% 10% 18% 25% 5% 1	2801
	11th to 20th	Day	41% 13% 25% 20% 2	2619
	21st to end	Day	33% 10% 28% 26% 3	2775
August	1st to 10th	Day	37% 12% 27% 21% 3	2530
	11th to 20th	Day	33% 10% 26% 26% 6%	2408
	21st to end	Day	40% 10% 21% 23% 6%	2574
September	1st to 10th	Day	40% 8% 19% 24% 7% 1	2265
	11th to 20th	Day	39% 8% 20% 26% 7%	1998
	21st to end	Day	39% 9% 16% 25% 9% 2	1980
October	1st to 10th	Day	46% 7% 17% 22% 8% 1	1890
	11th to 20th	Day	45% 9% 14% 24% 8%	1620
	21st to end	Day	50% 8% 12% 23% 7%	1782
November	1st to 10th	Day	58% 7% 13% 15% 6% 1	1484
	11th to 20th	Day	50% 7% 16% 19% 8%	1330
	21st to end	Day	52% 8% 15% 17% 6% 1	1330
December	1st to 10th	Day	55% 7% 12% 15% 9% 1	1330
	11th to 20th	Day	53% 7% 14% 18% 7%	1684
	21st to end	Day	38% 6% 14% 24% 16% 2	2266
January	1st to 10th	Night	55% 6% 13% 16% 7% 2	4730
	11th to 20th	Night	49% 5% 13% 13% 18% 2	4740
	21st to end	Night	50% 8% 18% 15% 8%	5019
February	1st to 10th	Night	56% 7% 13% 16% 8% 1	2660
	11th to 20th	Night	53% 8% 14% 15% 10% 1	2491
	21st to end	Night	52% 7% 11% 20% 9% 1	1958
March	1st to 10th	Night	51% 8% 14% 19% 6% 1	2280
	11th to 20th	Night	49% 6% 12% 19% 12% 1	2141
	21st to end	Night	54% 8% 13% 18% 6% 1	2228
April	1st to 10th	Night	51% 8% 14% 18% 9% 1	1754
	11th to 20th	Night	54% 6% 11% 19% 10% 2	1601
	21st to end	Night	46% 7% 11% 23% 12% 1	1603
May	1st to 10th	Night	53% 8% 10% 19% 10% 1	1324
	11th to 20th	Night	43% 8% 11% 23% 13% 1	1239
	21st to end	Night	52% 7% 12% 17% 11% 1	1358
June	1st to 10th	Night	52% 7% 14% 19% 8%	1238
	11th to 20th	Night	56% 13% 13% 14% 3	1080
	21st to end	Night	42% 13% 19% 21% 5%	1080
July	1st to 10th	Night	39% 10% 22% 22% 6% 1	1050
	11th to 20th	Night	43% 13% 22% 18% 3	1216
	21st to end	Night	36% 11% 23% 27% 4	1302
August	1st to 10th	Night	42% 12% 21% 24% 2	1382
	11th to 20th	Night	37% 9% 22% 25% 6% 1	1491
	21st to end	Night	39% 10% 16% 25% 8%	1782
September	1st to 10th	Night	37% 9% 17% 27% 8% 2	1692
	11th to 20th	Night	38% 6% 16% 29% 10% 1	1962
	21st to end	Night	38% 9% 14% 26% 13% 2	1980
October	1st to 10th	Night	46% 7% 13% 23% 11%	2069
	11th to 20th	Night	42% 7% 15% 25% 9%	2340
	21st to end	Night	48% 8% 15% 21% 8% 1	2574
November	1st to 10th	Night	59% 6% 11% 18% 6%	2574
	11th to 20th	Night	56% 7% 12% 17% 7% 1	2850
	21st to end	Night	53% 8% 15% 17% 5% 1	2850
December	1st to 10th	Night	53% 5% 12% 18% 10% 1	2850
	11th to 20th	Night	55% 7% 15% 17% 6%	3507
	21st to end	Night	38% 6% 15% 23% 14% 2	5374

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	12% 4 30% 29% 18% 7%	180
	11th to 20th	Day	12% 8% 28% 31% 17% 5%	180
	21st to end	Day	12% 12% 25% 30% 17% 5%	198
February	1st to 10th	Day	16% 9% 31% 30% 13% 2	180
	11th to 20th	Day	15% 5% 29% 33% 14% 4	227
	21st to end	Day	6% 9% 33% 29% 18% 6%	306
March	1st to 10th	Day	12% 8% 30% 32% 16% 3	460
	11th to 20th	Day	10% 7% 29% 33% 17% 5%	460
	21st to end	Day	14% 7% 31% 25% 20% 3	506
April	1st to 10th	Day	8% 12% 32% 33% 10% 3	429
	11th to 20th	Day	15% 6% 22% 33% 17% 7%	412
	21st to end	Day	14% 10% 28% 29% 15% 5%	420
May	1st to 10th	Day	14% 9% 26% 29% 18% 3	539
	11th to 20th	Day	11% 5% 23% 36% 20% 5%	625
	21st to end	Day	18% 4 21% 29% 20% 7%	679
June	1st to 10th	Day	18% 8% 24% 31% 14% 4	648
	11th to 20th	Day	20% 5% 21% 27% 20% 7%	810
	21st to end	Day	12% 4 18% 30% 26% 9%	810
July	1st to 10th	Day	13% 2 20% 34% 23% 8%	796
	11th to 20th	Day	12% 3 20% 33% 25% 6%	618
	21st to end	Day	11% 4 14% 33% 26% 11%	684
August	1st to 10th	Day	11% 6% 16% 31% 22% 16%	488
	11th to 20th	Day	9% 4 26% 32% 22% 7%	437
	21st to end	Day	16% 5% 17% 32% 23% 8%	495
September	1st to 10th	Day	16% 9% 27% 24% 20% 5%	450
	11th to 20th	Day	17% 5% 24% 29% 19% 6%	450
	21st to end	Day	12% 11% 29% 30% 14% 5%	450
October	1st to 10th	Day	15% 8% 24% 30% 18% 5%	368
	11th to 20th	Day	15% 10% 30% 26% 15% 4	270
	21st to end	Day	14% 10% 37% 26% 10% 2	297
November	1st to 10th	Day	19% 6% 32% 29% 12% 3	266
	11th to 20th	Day	12% 7% 37% 29% 12% 3	180
	21st to end	Day	8% 7% 36% 33% 12% 5%	180
December	1st to 10th	Day	9% 8% 30% 33% 13% 7%	180
	11th to 20th	Day	8% 11% 32% 34% 13% 2	180
	21st to end	Day	7% 4 24% 35% 27% 5%	198
January	1st to 10th	Night	12% 6% 35% 33% 13% 2	951
	11th to 20th	Night	11% 8% 33% 33% 13% 2	950
	21st to end	Night	13% 10% 35% 29% 11% 2	928
February	1st to 10th	Night	11% 7% 28% 34% 18% 3	760
	11th to 20th	Night	11% 5% 33% 34% 16% 2	744
	21st to end	Night	10% 5% 29% 35% 18% 4	628
March	1st to 10th	Night	10% 5% 32% 34% 17% 2	760
	11th to 20th	Night	11% 4 31% 37% 15% 2	760
	21st to end	Night	14% 5% 26% 38% 15% 3	836
April	1st to 10th	Night	11% 7% 27% 37% 16% 2	662
	11th to 20th	Night	14% 6% 28% 33% 17% 1	533
	21st to end	Night	15% 6% 27% 36% 15% 1	523
May	1st to 10th	Night	14% 6% 26% 37% 15% 2	360
	11th to 20th	Night	13% 2 27% 35% 21% 2	354
	21st to end	Night	20% 5% 22% 33% 18% 1	389
June	1st to 10th	Night	20% 5% 21% 38% 14% 2	360
	11th to 20th	Night	20% 4 19% 34% 20% 3	360
	21st to end	Night	14% 3 18% 36% 25% 4	360
July	1st to 10th	Night	16% 3 14% 42% 24% 1	350
	11th to 20th	Night	13% 5% 20% 38% 23% 2	348
	21st to end	Night	11% 3 17% 41% 25% 3	394
August	1st to 10th	Night	11% 4 18% 31% 31% 5%	358
	11th to 20th	Night	13% 4 18% 38% 25% 4	423
	21st to end	Night	13% 3 23% 38% 23% 1	594
September	1st to 10th	Night	16% 3 18% 39% 22% 2	612
	11th to 20th	Night	16% 4 19% 38% 21% 2	720
	21st to end	Night	14% 5% 28% 35% 16% 2	720
October	1st to 10th	Night	17% 4 26% 36% 17% 1	720
	11th to 20th	Night	15% 4 31% 36% 13% 1	720
	21st to end	Night	12% 9% 33% 33% 12% 1	792
November	1st to 10th	Night	21% 5% 30% 31% 10% 2	905
	11th to 20th	Night	13% 8% 37% 30% 10% 3	950
	21st to end	Night	12% 6% 37% 34% 10% 1	950
December	1st to 10th	Night	14% 6% 33% 30% 14% 3	950
	11th to 20th	Night	13% 7% 32% 34% 14% 1	950
	21st to end	Night	11% 4 30% 37% 15% 3	1090

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