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 2024-10-24.

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% 5% 12% 6% 5% 5% 4 5% 6% 35%	101720
	Night	3 11% 5% 12% 7% 5% 4 4 5% 7% 36%	97231
Transparency	Day	49% 6% 11% 18% 13% 3	101460
	Night	48% 7% 11% 19% 12% 3	97080
Seeing	Day	20% 17% 27% 22% 11% 3	15636
	Night	16% 16% 26% 28% 11% 2	25176

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	7% 7% 26% 12% 7% 5% 4 5% 6% 22%	2219
	11th to 20th	Day	1 13% 8% 13% 11% 7% 5% 3 4 5% 29%	2687
	21st to end	Day	1 16% 13% 20% 6% 4 3 2 3 5% 27%	3146
February	1st to 10th	Day	1 16% 9% 25% 10% 4 4 2 4 5% 20%	1710
	11th to 20th	Day	13% 9% 26% 12% 6% 4 3 3 4 20%	1665
	21st to end	Day	1 17% 8% 20% 19% 6% 3 3 3 3 18%	1437
March	1st to 10th	Day	13% 9% 21% 14% 5% 3 2 3 4 26%	3430
	11th to 20th	Day	1 16% 9% 12% 6% 4 3 2 4 5% 36%	3490
	21st to end	Day	2 25% 12% 24% 7% 5% 4 3 4 4 11%	3825
April	1st to 10th	Day	4 25% 10% 15% 7% 3 3 4 4 6% 19%	2237
	11th to 20th	Day	3 21% 6% 16% 6% 6% 5% 4 5% 6% 22%	2358
	21st to end	Day	6% 25% 7% 12% 6% 5% 4 3 4 6% 23%	2470
May	1st to 10th	Day	9% 18% 7% 15% 6% 5% 5% 3 4 5% 22%	4135
	11th to 20th	Day	5% 13% 4 10% 6% 6% 6% 5% 6% 8% 31%	4388
	21st to end	Day	8% 22% 6% 9% 6% 5% 5% 4 5% 6% 24%	4825
June	1st to 10th	Day	12% 14% 3 6% 5% 5% 5% 5% 7% 8% 29%	2700
	11th to 20th	Day	13% 13% 3 7% 5% 5% 5% 5% 6% 7% 32%	2850
	21st to end	Day	5% 6% 2 5% 4 4 4 5% 7% 8% 50%	2850
July	1st to 10th	Day	4 4 1 5% 5% 6% 7% 5% 7% 9% 46%	4740
	11th to 20th	Day	3 4 2 5% 4 5% 6% 5% 8% 8% 52%	4564
	21st to end	Day	3 4 2 6% 5% 6% 6% 5% 6% 8% 49%	4560
August	1st to 10th	Day	6% 5% 2 6% 5% 5% 6% 5% 8% 9% 43%	4092
	11th to 20th	Day	4 4 2 6% 4 5% 5% 5% 6% 7% 51%	4028
	21st to end	Day	7% 5% 2 5% 4 3 4 3 5% 6% 56%	4438
September	1st to 10th	Day	9% 7% 2 5% 4 3 3 3 5% 6% 53%	2280
	11th to 20th	Day	9% 11% 3 6% 4 4 4 3 4 6% 47%	2149
	21st to end	Day	8% 10% 2 6% 4 4 4 3 5% 6% 49%	2081
October	1st to 10th	Day	8% 16% 4 8% 4 4 3 3 4 6% 40%	1900
	11th to 20th	Day	6% 19% 4 8% 3 3 3 3 4 5% 44%	1900
	21st to end	Day	5% 16% 6% 12% 5% 4 3 3 5% 6% 36%	1997
November	1st to 10th	Day	6% 19% 5% 13% 4 4 4 3 6% 6% 30%	1545
	11th to 20th	Day	2 18% 6% 12% 7% 5% 3 3 5% 7% 32%	1520
	21st to end	Day	1 10% 6% 15% 8% 6% 4 3 5% 6% 36%	1520
December	1st to 10th	Day	1 14% 6% 16% 10% 7% 5% 5% 5% 7% 24%	1520
	11th to 20th	Day	2 19% 8% 18% 8% 5% 4 4 5% 6% 22%	1926
	21st to end	Day	1 11% 11% 17% 10% 5% 4 3 4 6% 29%	2538
January	1st to 10th	Night	6% 5% 21% 14% 7% 5% 4 5% 7% 25%	4726
	11th to 20th	Night	1 8% 6% 16% 14% 7% 5% 4 5% 7% 27%	4291
	21st to end	Night	2 18% 11% 18% 7% 5% 4 3 4 6% 23%	4521
February	1st to 10th	Night	1 13% 7% 22% 12% 7% 5% 4 4 6% 19%	2470
	11th to 20th	Night	1 11% 8% 23% 10% 6% 5% 4 5% 5% 22%	2402
	21st to end	Night	13% 8% 22% 13% 6% 4 3 5% 5% 21%	2017
March	1st to 10th	Night	1 13% 6% 19% 16% 4 3 2 3 5% 28%	3443
	11th to 20th	Night	1 9% 8% 13% 5% 4 4 3 4 5% 44%	3490
	21st to end	Night	1 19% 10% 18% 7% 4 5% 4 7% 7% 18%	3828
April	1st to 10th	Night	3 17% 6% 15% 6% 4 4 3 6% 6% 29%	1942
	11th to 20th	Night	3 12% 5% 12% 7% 5% 5% 4 7% 8% 32%	1766
	21st to end	Night	4 18% 3 8% 5% 5% 4 4 6% 7% 35%	1710
May	1st to 10th	Night	5% 13% 7% 15% 6% 5% 4 4 5% 7% 28%	2833
	11th to 20th	Night	5% 12% 4 7% 5% 5% 4 4 6% 8% 41%	2517
	21st to end	Night	7% 20% 4 9% 6% 4 5% 5% 6% 8% 27%	2762
June	1st to 10th	Night	12% 9% 2 7% 5% 4 5% 4 8% 9% 36%	1475
	11th to 20th	Night	10% 10% 4 7% 6% 4 4 3 5% 7% 40%	1330
	21st to end	Night	4 4 1 4 3 4 5% 4 4 7% 59%	1330
July	1st to 10th	Night	6% 4 1 3 3 3 4 4 6% 7% 59%	2220
	11th to 20th	Night	3 3 1 4 4 4 4 5% 7% 9% 56%	2398
	21st to end	Night	3 3 1 5% 4 5% 5% 4 6% 7% 57%	3000
August	1st to 10th	Night	5% 7% 2 6% 4 4 6% 4 7% 8% 47%	2847
	11th to 20th	Night	3 3 2 5% 4 5% 6% 4 6% 7% 53%	2811
	21st to end	Night	5% 5% 2 4 2 3 3 3 4 5% 65%	3229
September	1st to 10th	Night	6% 6% 1 5% 3 4 4 3 5% 8% 55%	1900
	11th to 20th	Night	7% 8% 1 6% 3 3 4 4 5% 7% 51%	2028
	21st to end	Night	8% 8% 2 6% 3 2 2 3 5% 6% 54%	2099
October	1st to 10th	Night	6% 11% 3 7% 5% 5% 5% 4 5% 7% 43%	2280
	11th to 20th	Night	6% 13% 3 7% 4 3 3 3 5% 6% 47%	2280
	21st to end	Night	5% 12% 5% 9% 4 4 3 2 6% 8% 41%	2423
November	1st to 10th	Night	5% 17% 5% 11% 6% 4 4 4 5% 7% 31%	2513
	11th to 20th	Night	2 15% 5% 14% 7% 4 4 4 5% 7% 32%	2660
	21st to end	Night	2 10% 4 13% 8% 5% 5% 3 5% 8% 37%	2660
December	1st to 10th	Night	12% 7% 19% 10% 6% 6% 5% 6% 6% 24%	2660
	11th to 20th	Night	1 13% 8% 17% 11% 6% 5% 3 5% 6% 25%	3271
	21st to end	Night	1 13% 9% 14% 9% 6% 4 3 4 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	71% 4 9% 12% 3 2	1674
	21st to end	Day	73% 5% 4 8% 6% 3	1437
March	1st to 10th	Day	64% 5% 9% 14% 5% 2	3430
	11th to 20th	Day	53% 7% 15% 18% 6% 2	3490
	21st to end	Day	77% 6% 8% 7% 1	3825
April	1st to 10th	Day	68% 5% 9% 13% 4	2237
	11th to 20th	Day	63% 6% 11% 15% 4 1	2361
	21st to end	Day	63% 6% 14% 13% 3 1	2470
May	1st to 10th	Day	63% 6% 10% 16% 4	4135
	11th to 20th	Day	44% 11% 17% 20% 7% 1	4392
	21st to end	Day	57% 10% 14% 16% 4	4825
June	1st to 10th	Day	50% 7% 21% 18% 4	2700
	11th to 20th	Day	49% 6% 12% 18% 13% 2	2850
	21st to end	Day	29% 6% 14% 30% 18% 3	2850
July	1st to 10th	Day	30% 8% 11% 24% 24% 3	4666
	11th to 20th	Day	27% 7% 9% 17% 27% 12%	4484
	21st to end	Day	29% 8% 7% 20% 28% 8%	4416
August	1st to 10th	Day	34% 8% 10% 19% 22% 7%	4078
	11th to 20th	Day	30% 7% 9% 25% 24% 5%	4067
	21st to end	Day	29% 5% 7% 24% 28% 6%	4437
September	1st to 10th	Day	32% 6% 5% 22% 30% 5%	2280
	11th to 20th	Day	40% 5% 9% 23% 19% 3	2149
	21st to end	Day	37% 5% 11% 28% 15% 3	2081
October	1st to 10th	Day	48% 4 10% 22% 14% 2	1900
	11th to 20th	Day	45% 5% 17% 23% 10% 1	1900
	21st to end	Day	50% 6% 14% 18% 10% 2	1997
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	2403
	21st to end	Night	66% 7% 6% 10% 8% 4	2017
March	1st to 10th	Night	60% 6% 7% 15% 7% 5%	3443
	11th to 20th	Night	45% 6% 18% 21% 8% 2	3490
	21st to end	Night	61% 11% 12% 12% 3	3828
April	1st to 10th	Night	57% 7% 12% 17% 7%	1942
	11th to 20th	Night	52% 6% 16% 19% 5% 1	1766
	21st to end	Night	49% 8% 18% 19% 6%	1710
May	1st to 10th	Night	53% 10% 14% 16% 7%	2833
	11th to 20th	Night	39% 10% 18% 26% 5% 2	2518
	21st to end	Night	50% 12% 16% 19% 4	2762
June	1st to 10th	Night	43% 9% 20% 23% 5%	1475
	11th to 20th	Night	44% 6% 13% 22% 13% 2	1330
	21st to end	Night	24% 6% 16% 30% 20% 4	1330
July	1st to 10th	Night	24% 8% 11% 25% 30% 2	2185
	11th to 20th	Night	22% 5% 9% 21% 34% 9%	2355
	21st to end	Night	25% 5% 8% 27% 28% 7%	2906
August	1st to 10th	Night	33% 6% 9% 22% 22% 7%	2838
	11th to 20th	Night	29% 5% 10% 26% 24% 5%	2838
	21st to end	Night	23% 4 7% 29% 31% 6%	3229
September	1st to 10th	Night	28% 6% 8% 24% 28% 6%	1900
	11th to 20th	Night	33% 6% 14% 25% 18% 4	2028
	21st to end	Night	33% 4 12% 31% 18% 2	2099
October	1st to 10th	Night	42% 5% 13% 23% 15% 1	2280
	11th to 20th	Night	41% 5% 15% 25% 11% 3	2280
	21st to end	Night	43% 9% 14% 24% 9% 1	2423
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% 20% 29% 11% 3 3	270
	21st to end	Day	29% 27% 22% 18% 4	249
March	1st to 10th	Day	26% 30% 25% 14% 3 1	460
	11th to 20th	Day	19% 27% 30% 15% 8% 2	460
	21st to end	Day	21% 25% 31% 18% 4 1	506
April	1st to 10th	Day	29% 27% 32% 10% 2	460
	11th to 20th	Day	26% 28% 30% 12% 3	452
	21st to end	Day	26% 18% 26% 20% 6% 3	460
May	1st to 10th	Day	23% 13% 27% 22% 11% 3	475
	11th to 20th	Day	19% 11% 25% 26% 14% 4	675
	21st to end	Day	25% 11% 19% 20% 18% 6%	734
June	1st to 10th	Day	19% 7% 20% 27% 20% 7%	680
	11th to 20th	Day	25% 14% 26% 24% 10% 2	680
	21st to end	Day	10% 7% 25% 35% 19% 4	680
July	1st to 10th	Day	7% 7% 21% 36% 23% 6%	671
	11th to 20th	Day	8% 11% 23% 36% 19% 3	668
	21st to end	Day	9% 8% 27% 31% 20% 4	598
August	1st to 10th	Day	14% 11% 26% 27% 17% 5%	487
	11th to 20th	Day	10% 14% 25% 30% 16% 5%	477
	21st to end	Day	16% 16% 30% 20% 13% 6%	539
September	1st to 10th	Day	16% 16% 32% 24% 9% 3	490
	11th to 20th	Day	25% 18% 25% 17% 10% 4	490
	21st to end	Day	22% 21% 32% 15% 9% 2	481
October	1st to 10th	Day	22% 16% 27% 18% 13% 4	300
	11th to 20th	Day	24% 21% 23% 16% 12% 4	300
	21st to end	Day	29% 20% 29% 16% 5% 1	306
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%	744
	21st to end	Night	19% 26% 26% 19% 9% 1	628
March	1st to 10th	Night	19% 21% 29% 23% 6% 1	760
	11th to 20th	Night	17% 21% 24% 27% 10% 1	760
	21st to end	Night	15% 17% 31% 27% 8% 1	836
April	1st to 10th	Night	17% 21% 28% 27% 7% 1	612
	11th to 20th	Night	15% 18% 35% 24% 7% 1	563
	21st to end	Night	17% 12% 26% 31% 13% 1	570
May	1st to 10th	Night	15% 14% 21% 31% 16% 3	570
	11th to 20th	Night	16% 8% 20% 36% 18% 2	561
	21st to end	Night	20% 11% 19% 31% 16% 2	617
June	1st to 10th	Night	20% 8% 18% 32% 19% 2	525
	11th to 20th	Night	18% 12% 27% 31% 12% 1	380
	21st to end	Night	8% 4 23% 44% 19% 2	380
July	1st to 10th	Night	6% 2 16% 41% 32% 4	370
	11th to 20th	Night	6% 4 28% 45% 16% 1	467
	21st to end	Night	8% 5% 21% 44% 20% 2	624
August	1st to 10th	Night	10% 4 20% 45% 20% 2	567
	11th to 20th	Night	8% 4 21% 43% 22% 2	564
	21st to end	Night	11% 8% 21% 38% 20% 1	627
September	1st to 10th	Night	11% 6% 24% 38% 17% 3	570
	11th to 20th	Night	14% 9% 20% 35% 19% 3	698
	21st to end	Night	16% 9% 21% 33% 18% 2	760
October	1st to 10th	Night	16% 12% 21% 33% 17% 2	760
	11th to 20th	Night	19% 13% 24% 30% 12% 2	760
	21st to end	Night	19% 18% 29% 25% 7% 3	804
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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