Cooke City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cooke City clear sky chart from 2005-11-06 to 2024-02-20.

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	5% 13% 6% 11% 8% 4 5% 4 5% 6% 33%	78469
	Night	3 10% 6% 11% 9% 4 5% 5% 5% 7% 35%	80720
Transparency	Day	52% 6% 11% 17% 11% 3	78169
	Night	50% 6% 12% 18% 11% 3	80541
Seeing	Day	20% 17% 26% 22% 12% 3	14605
	Night	16% 16% 26% 28% 11% 2	24391

By Month

Percentage Cloud Cover SW (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	6% 8% 23% 15% 5% 5% 4 5% 6% 22%	2219
	11th to 20th	Day	1 12% 9% 11% 13% 6% 5% 3 4 5% 29%	2687
	21st to end	Day	1 16% 14% 19% 7% 3 4 3 3 5% 27%	3146
February	1st to 10th	Day	1 15% 10% 22% 12% 4 5% 2 4 5% 20%	1710
	11th to 20th	Day	1 12% 10% 23% 14% 5% 5% 4 3 4 20%	1656
	21st to end	Day	1 13% 9% 17% 23% 4 3 4 3 4 18%	1354
March	1st to 10th	Day	1 17% 8% 16% 13% 4 6% 3 5% 6% 22%	1966
	11th to 20th	Day	2 17% 11% 13% 9% 4 4 4 4 6% 26%	1980
	21st to end	Day	4 19% 10% 17% 9% 4 5% 4 5% 6% 17%	2178
April	1st to 10th	Day	5% 23% 10% 14% 9% 3 3 4 5% 6% 18%	2119
	11th to 20th	Day	4 20% 7% 15% 8% 5% 5% 5% 5% 6% 21%	2232
	21st to end	Day	6% 23% 8% 11% 6% 3 5% 4 4 6% 23%	2340
May	1st to 10th	Day	8% 18% 7% 11% 7% 3 6% 4 5% 6% 23%	2351
	11th to 20th	Day	7% 14% 4 9% 8% 5% 7% 7% 6% 8% 24%	2478
	21st to end	Day	12% 19% 6% 8% 7% 4 5% 5% 5% 6% 20%	2724
June	1st to 10th	Day	12% 13% 4 6% 6% 4 6% 7% 7% 8% 29%	2557
	11th to 20th	Day	13% 13% 3 7% 6% 3 5% 6% 6% 7% 31%	2700
	21st to end	Day	5% 5% 2 5% 4 3 4 6% 7% 8% 51%	2700
July	1st to 10th	Day	5% 4 2 4 4 4 6% 6% 7% 10% 48%	2700
	11th to 20th	Day	4 5% 2 4 5% 3 5% 5% 6% 6% 54%	2602
	21st to end	Day	4 5% 2 5% 6% 3 5% 5% 5% 7% 52%	2609
August	1st to 10th	Day	8% 6% 3 6% 6% 4 5% 6% 6% 7% 43%	2328
	11th to 20th	Day	5% 5% 2 6% 5% 3 6% 6% 5% 6% 51%	2299
	21st to end	Day	7% 6% 3 5% 6% 3 4 5% 6% 7% 50%	2530
September	1st to 10th	Day	9% 7% 2 5% 4 2 3 4 5% 6% 52%	2160
	11th to 20th	Day	9% 10% 3 6% 4 3 3 3 3 6% 49%	2036
	21st to end	Day	8% 10% 2 5% 5% 2 5% 4 5% 6% 47%	1972
October	1st to 10th	Day	9% 16% 5% 7% 5% 3 4 4 4 6% 38%	1800
	11th to 20th	Day	7% 18% 5% 7% 4 1 4 4 4 5% 42%	1800
	21st to end	Day	5% 16% 7% 11% 6% 3 3 3 4 6% 36%	1967
November	1st to 10th	Day	6% 18% 5% 12% 5% 3 4 4 6% 6% 30%	1545
	11th to 20th	Day	2 17% 7% 11% 8% 4 4 4 5% 7% 32%	1520
	21st to end	Day	1 9% 8% 13% 9% 4 5% 4 4 6% 36%	1520
December	1st to 10th	Day	1 13% 7% 14% 10% 5% 7% 6% 5% 7% 24%	1520
	11th to 20th	Day	2 18% 8% 16% 10% 3 5% 4 5% 6% 23%	1926
	21st to end	Day	1 10% 12% 15% 11% 4 4 4 4 6% 29%	2538
January	1st to 10th	Night	1 5% 6% 17% 18% 5% 6% 5% 5% 7% 25%	4726
	11th to 20th	Night	1 8% 7% 14% 16% 5% 6% 5% 5% 7% 27%	4291
	21st to end	Night	2 18% 11% 16% 9% 4 4 3 4 6% 23%	4521
February	1st to 10th	Night	1 12% 8% 20% 14% 5% 6% 4 4 7% 19%	2470
	11th to 20th	Night	1 10% 8% 21% 13% 5% 5% 5% 5% 5% 22%	2395
	21st to end	Night	1 10% 9% 17% 17% 5% 5% 4 4 6% 22%	1902
March	1st to 10th	Night	1 14% 9% 17% 11% 4 4 4 4 6% 27%	1993
	11th to 20th	Night	1 12% 8% 11% 9% 4 6% 5% 5% 7% 33%	1980
	21st to end	Night	2 15% 7% 16% 10% 3 5% 5% 7% 8% 23%	2178
April	1st to 10th	Night	3 15% 6% 14% 7% 3 5% 4 6% 7% 29%	1840
	11th to 20th	Night	3 11% 6% 11% 8% 4 5% 5% 7% 8% 31%	1672
	21st to end	Night	4 16% 4 7% 6% 4 4 5% 7% 7% 36%	1620
May	1st to 10th	Night	5% 12% 6% 10% 7% 4 5% 6% 4 7% 35%	1607
	11th to 20th	Night	5% 11% 3 7% 7% 4 6% 5% 8% 8% 36%	1417
	21st to end	Night	10% 13% 4 9% 8% 3 6% 6% 7% 9% 27%	1552
June	1st to 10th	Night	11% 9% 3 6% 5% 3 5% 5% 8% 9% 36%	1398
	11th to 20th	Night	10% 10% 3 7% 6% 3 4 5% 5% 7% 39%	1260
	21st to end	Night	5% 4 1 3 4 3 4 5% 4 8% 59%	1260
July	1st to 10th	Night	4 3 1 2 4 2 5% 6% 7% 8% 58%	1260
	11th to 20th	Night	3 3 1 4 4 3 4 5% 6% 8% 58%	1354
	21st to end	Night	3 3 2 3 4 3 5% 4 6% 7% 61%	1706
August	1st to 10th	Night	5% 6% 2 5% 5% 3 6% 6% 6% 9% 47%	1611
	11th to 20th	Night	4 3 1 3 4 2 5% 4 6% 7% 60%	1602
	21st to end	Night	6% 4 1 3 4 3 4 4 6% 6% 57%	1826
September	1st to 10th	Night	6% 6% 1 5% 4 4 4 4 5% 8% 54%	1800
	11th to 20th	Night	7% 7% 1 5% 4 2 4 4 5% 7% 52%	1921
	21st to end	Night	9% 8% 2 6% 4 1 3 3 4 7% 52%	1988
October	1st to 10th	Night	7% 11% 4 7% 6% 3 5% 5% 5% 7% 41%	2160
	11th to 20th	Night	7% 13% 3 7% 4 2 3 3 5% 7% 46%	2160
	21st to end	Night	5% 12% 5% 9% 6% 3 3 3 6% 8% 40%	2387
November	1st to 10th	Night	6% 16% 5% 10% 7% 3 4 5% 5% 7% 31%	2513
	11th to 20th	Night	2 15% 6% 12% 9% 3 4 4 5% 7% 32%	2660
	21st to end	Night	2 8% 6% 12% 9% 4 6% 4 5% 8% 37%	2660
December	1st to 10th	Night	12% 6% 16% 12% 5% 7% 6% 5% 7% 24%	2660
	11th to 20th	Night	2 12% 8% 15% 13% 5% 5% 4 5% 6% 25%	3271
	21st to end	Night	1 12% 9% 12% 10% 4 5% 4 3 6% 33%	5099

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	64% 4 7% 17% 8% 1	2219
	11th to 20th	Day	59% 6% 10% 10% 8% 7%	2687
	21st to end	Day	63% 4 7% 13% 10% 2	3146
February	1st to 10th	Day	70% 4 9% 11% 5% 1	1710
	11th to 20th	Day	70% 4 9% 12% 3 2	1665
	21st to end	Day	72% 5% 4 9% 7% 4	1354
March	1st to 10th	Day	65% 5% 12% 13% 4 1	1966
	11th to 20th	Day	61% 6% 11% 12% 6% 3	1980
	21st to end	Day	70% 6% 11% 11% 2	2178
April	1st to 10th	Day	69% 5% 9% 13% 4	2119
	11th to 20th	Day	65% 6% 11% 15% 4	2235
	21st to end	Day	63% 6% 15% 13% 3 1	2340
May	1st to 10th	Day	62% 5% 12% 17% 4	2351
	11th to 20th	Day	56% 7% 20% 14% 2	2482
	21st to end	Day	63% 7% 16% 11% 3	2724
June	1st to 10th	Day	50% 7% 21% 18% 4	2557
	11th to 20th	Day	50% 6% 13% 18% 11% 2	2700
	21st to end	Day	29% 6% 14% 30% 17% 3	2700
July	1st to 10th	Day	29% 7% 13% 26% 20% 4	2626
	11th to 20th	Day	29% 5% 8% 20% 26% 12%	2522
	21st to end	Day	29% 6% 7% 21% 29% 8%	2464
August	1st to 10th	Day	39% 6% 9% 21% 20% 6%	2313
	11th to 20th	Day	33% 4 9% 28% 21% 5%	2299
	21st to end	Day	33% 5% 8% 26% 22% 6%	2530
September	1st to 10th	Day	33% 6% 5% 22% 29% 5%	2160
	11th to 20th	Day	38% 5% 9% 24% 20% 4	2036
	21st to end	Day	39% 5% 11% 29% 14% 3	1972
October	1st to 10th	Day	50% 4 11% 21% 12% 2	1800
	11th to 20th	Day	46% 5% 17% 22% 9% 1	1800
	21st to end	Day	51% 6% 14% 18% 10% 2	1967
November	1st to 10th	Day	55% 7% 12% 16% 8% 2	1545
	11th to 20th	Day	53% 7% 15% 16% 7% 2	1520
	21st to end	Day	50% 6% 15% 16% 11% 2	1520
December	1st to 10th	Day	59% 7% 10% 10% 10% 4	1520
	11th to 20th	Day	62% 6% 14% 14% 3 1	1924
	21st to end	Day	58% 5% 5% 11% 7% 14%	2538
January	1st to 10th	Night	58% 6% 9% 15% 10% 2	4726
	11th to 20th	Night	58% 5% 11% 12% 10% 5%	4291
	21st to end	Night	64% 6% 8% 13% 7% 1	4521
February	1st to 10th	Night	67% 6% 7% 11% 7% 1	2470
	11th to 20th	Night	65% 6% 9% 12% 6% 2	2396
	21st to end	Night	64% 7% 6% 11% 8% 4	1902
March	1st to 10th	Night	59% 6% 11% 13% 8% 3	1993
	11th to 20th	Night	52% 7% 14% 16% 8% 2	1980
	21st to end	Night	60% 8% 14% 13% 4 1	2178
April	1st to 10th	Night	57% 6% 12% 17% 7%	1840
	11th to 20th	Night	54% 6% 16% 19% 5% 1	1672
	21st to end	Night	48% 8% 18% 19% 6%	1620
May	1st to 10th	Night	50% 6% 15% 23% 5%	1607
	11th to 20th	Night	44% 8% 25% 18% 4	1418
	21st to end	Night	54% 7% 20% 15% 4	1552
June	1st to 10th	Night	43% 9% 21% 22% 4	1398
	11th to 20th	Night	44% 6% 14% 21% 12% 2	1260
	21st to end	Night	24% 6% 16% 31% 19% 4	1260
July	1st to 10th	Night	23% 7% 15% 29% 21% 4	1225
	11th to 20th	Night	22% 5% 11% 25% 26% 11%	1311
	21st to end	Night	23% 4 10% 26% 30% 8%	1611
August	1st to 10th	Night	34% 6% 11% 24% 19% 6%	1602
	11th to 20th	Night	24% 4 12% 33% 23% 5%	1602
	21st to end	Night	27% 5% 10% 29% 24% 5%	1826
September	1st to 10th	Night	29% 6% 8% 24% 28% 6%	1800
	11th to 20th	Night	32% 6% 14% 26% 18% 5%	1921
	21st to end	Night	34% 4 12% 32% 17% 1	1988
October	1st to 10th	Night	44% 5% 14% 22% 14% 1	2160
	11th to 20th	Night	42% 5% 15% 25% 11% 3	2160
	21st to end	Night	43% 9% 14% 23% 9% 1	2387
November	1st to 10th	Night	53% 6% 13% 17% 7% 2	2513
	11th to 20th	Night	53% 7% 16% 15% 7% 2	2660
	21st to end	Night	47% 7% 15% 15% 13% 3	2660
December	1st to 10th	Night	59% 8% 9% 12% 10% 3	2660
	11th to 20th	Night	59% 6% 11% 18% 5% 1	3272
	21st to end	Night	55% 5% 4 15% 9% 12%	5099

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	21% 19% 29% 21% 9% 1	180
	11th to 20th	Day	18% 25% 27% 15% 10% 5%	266
	21st to end	Day	14% 20% 42% 16% 7% 1	297
February	1st to 10th	Day	24% 31% 31% 11% 3	270
	11th to 20th	Day	33% 19% 28% 12% 4 3	267
	21st to end	Day	26% 28% 23% 18% 4	220
March	1st to 10th	Day	26% 31% 25% 14% 3 1	420
	11th to 20th	Day	20% 28% 29% 14% 7% 2	420
	21st to end	Day	21% 26% 29% 18% 4 1	462
April	1st to 10th	Day	31% 28% 30% 9% 2	420
	11th to 20th	Day	28% 29% 29% 11% 3	412
	21st to end	Day	26% 18% 26% 20% 6% 3	420
May	1st to 10th	Day	23% 12% 28% 23% 11% 3	434
	11th to 20th	Day	19% 11% 26% 26% 14% 4	625
	21st to end	Day	25% 11% 18% 21% 19% 6%	679
June	1st to 10th	Day	18% 7% 20% 26% 21% 8%	630
	11th to 20th	Day	26% 12% 26% 24% 10% 2	630
	21st to end	Day	10% 7% 22% 36% 20% 5%	630
July	1st to 10th	Day	7% 7% 19% 38% 24% 6%	621
	11th to 20th	Day	9% 10% 22% 36% 20% 4	618
	21st to end	Day	8% 7% 28% 31% 21% 5%	551
August	1st to 10th	Day	14% 10% 24% 29% 18% 5%	447
	11th to 20th	Day	11% 10% 24% 32% 17% 6%	437
	21st to end	Day	15% 14% 30% 21% 14% 6%	495
September	1st to 10th	Day	17% 15% 33% 23% 10% 3	450
	11th to 20th	Day	23% 17% 27% 18% 11% 5%	450
	21st to end	Day	21% 20% 32% 15% 10% 2	442
October	1st to 10th	Day	21% 14% 27% 19% 14% 5%	270
	11th to 20th	Day	26% 22% 22% 16% 11% 3	270
	21st to end	Day	28% 20% 30% 16% 5% 1	297
November	1st to 10th	Day	27% 22% 25% 15% 7% 3	270
	11th to 20th	Day	26% 21% 31% 15% 5% 1	270
	21st to end	Day	13% 21% 35% 23% 6% 1	270
December	1st to 10th	Day	23% 24% 24% 18% 7% 3	270
	11th to 20th	Day	28% 22% 24% 20% 4 1	270
	21st to end	Day	24% 20% 34% 12% 6% 4	225
January	1st to 10th	Night	17% 25% 27% 24% 7% 1	950
	11th to 20th	Night	18% 24% 28% 20% 8% 2	860
	21st to end	Night	14% 19% 35% 24% 7% 2	836
February	1st to 10th	Night	19% 24% 32% 19% 5% 1	760
	11th to 20th	Night	19% 20% 31% 23% 7%	742
	21st to end	Night	18% 25% 27% 19% 9% 1	592
March	1st to 10th	Night	19% 21% 30% 23% 6% 1	720
	11th to 20th	Night	18% 21% 24% 26% 9% 1	720
	21st to end	Night	15% 18% 31% 26% 9% 1	792
April	1st to 10th	Night	17% 21% 27% 26% 7% 1	580
	11th to 20th	Night	15% 19% 34% 23% 7% 1	533
	21st to end	Night	17% 13% 25% 32% 13% 1	540
May	1st to 10th	Night	15% 13% 21% 32% 17% 3	540
	11th to 20th	Night	15% 8% 20% 36% 18% 2	531
	21st to end	Night	20% 11% 18% 32% 16% 2	584
June	1st to 10th	Night	20% 8% 17% 32% 20% 3	498
	11th to 20th	Night	18% 11% 25% 32% 12% 1	360
	21st to end	Night	8% 3 20% 46% 20% 3	360
July	1st to 10th	Night	6% 1 15% 41% 33% 4	350
	11th to 20th	Night	6% 4 28% 45% 16% 1	441
	21st to end	Night	8% 4 21% 44% 20% 3	591
August	1st to 10th	Night	10% 3 19% 45% 21% 2	537
	11th to 20th	Night	8% 4 19% 44% 23% 2	534
	21st to end	Night	10% 7% 21% 39% 21% 2	594
September	1st to 10th	Night	11% 7% 24% 38% 16% 4	540
	11th to 20th	Night	13% 8% 20% 36% 20% 4	661
	21st to end	Night	17% 9% 21% 33% 18% 3	720
October	1st to 10th	Night	16% 11% 21% 33% 18% 2	720
	11th to 20th	Night	19% 13% 24% 30% 11% 2	720
	21st to end	Night	18% 17% 29% 25% 7% 3	792
November	1st to 10th	Night	20% 22% 32% 20% 5% 1	848
	11th to 20th	Night	21% 27% 27% 20% 4	950
	21st to end	Night	18% 19% 26% 31% 6% 1	950
December	1st to 10th	Night	19% 23% 29% 21% 7% 1	950
	11th to 20th	Night	18% 25% 31% 20% 4 1	950
	21st to end	Night	21% 24% 27% 19% 9% 2	1045

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