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 2025-04-11.

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	4 13% 6% 12% 6% 5% 4 4 5% 6% 36%	117758
	Night	3 11% 5% 13% 7% 5% 4 3 5% 6% 37%	119387
Transparency	Day	49% 6% 11% 18% 13% 3	117498
	Night	47% 7% 11% 19% 13% 3	119236
Seeing	Day	20% 17% 27% 21% 11% 3	16168
	Night	16% 17% 26% 28% 11% 2	25918

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	8% 6% 28% 11% 6% 5% 4 5% 5% 21%	3179
	11th to 20th	Day	1 9% 6% 14% 10% 8% 7% 3 4 6% 32%	3871
	21st to end	Day	1 11% 9% 15% 7% 4 3 2 4 6% 39%	4510
February	1st to 10th	Day	1 17% 9% 25% 10% 5% 4 2 4 4 19%	1800
	11th to 20th	Day	13% 9% 26% 12% 5% 4 3 3 4 20%	1755
	21st to end	Day	1 16% 8% 19% 18% 6% 3 3 3 4 20%	1510
March	1st to 10th	Day	11% 8% 19% 11% 5% 3 2 3 4 32%	4940
	11th to 20th	Day	1 19% 9% 18% 6% 3 3 2 3 5% 32%	5000
	21st to end	Day	2 25% 13% 22% 6% 5% 5% 3 4 5% 12%	5486
April	1st to 10th	Day	3 24% 9% 15% 7% 4 3 4 5% 6% 20%	2355
	11th to 20th	Day	3 21% 6% 16% 6% 6% 5% 4 5% 6% 22%	2359
	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	5% 10% 3 5% 4 3 2 2 3 5% 59%	3170
	11th to 20th	Day	4 14% 3 6% 3 2 3 2 3 5% 55%	3150
	21st to end	Day	3 16% 7% 9% 4 4 4 3 5% 7% 38%	3413
November	1st to 10th	Day	6% 19% 5% 14% 4 4 4 3 5% 7% 31%	1628
	11th to 20th	Day	2 17% 7% 12% 7% 5% 4 3 5% 7% 32%	1600
	21st to end	Day	1 11% 6% 16% 8% 6% 4 3 5% 6% 35%	1600
December	1st to 10th	Day	8% 4 16% 8% 6% 5% 4 4 6% 39%	2620
	11th to 20th	Day	1 18% 10% 21% 6% 4 3 3 4 6% 23%	3026
	21st to end	Day	1 16% 13% 18% 9% 5% 4 3 4 5% 24%	3636
January	1st to 10th	Night	8% 5% 21% 14% 6% 5% 4 5% 6% 27%	6766
	11th to 20th	Night	1 6% 5% 16% 11% 6% 6% 4 6% 8% 31%	6131
	21st to end	Night	1 13% 8% 13% 7% 5% 4 3 4 6% 38%	6468
February	1st to 10th	Night	1 15% 7% 22% 12% 7% 5% 4 4 6% 18%	2600
	11th to 20th	Night	1 11% 8% 24% 10% 6% 5% 4 5% 5% 22%	2532
	21st to end	Night	14% 8% 22% 13% 6% 4 3 4 5% 22%	2119
March	1st to 10th	Night	11% 6% 18% 13% 5% 3 2 3 5% 33%	4953
	11th to 20th	Night	1 14% 7% 17% 5% 4 4 3 4 5% 38%	5000
	21st to end	Night	1 20% 12% 17% 6% 4 5% 4 6% 7% 19%	5489
April	1st to 10th	Night	3 16% 7% 14% 6% 4 4 3 6% 6% 30%	2044
	11th to 20th	Night	3 12% 5% 12% 7% 5% 5% 4 7% 8% 32%	1771
	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	4 7% 2 5% 3 3 3 3 4 6% 60%	3800
	11th to 20th	Night	5% 10% 3 6% 4 3 3 3 4 6% 53%	3778
	21st to end	Night	4 12% 4 10% 4 3 3 3 6% 8% 42%	4143
November	1st to 10th	Night	5% 17% 5% 11% 6% 4 4 4 5% 7% 32%	2649
	11th to 20th	Night	2 16% 5% 15% 8% 4 5% 4 5% 7% 31%	2800
	21st to end	Night	1 10% 4 14% 8% 5% 5% 4 5% 8% 35%	2800
December	1st to 10th	Night	7% 5% 14% 7% 4 5% 4 5% 6% 43%	4570
	11th to 20th	Night	1 13% 8% 21% 9% 5% 5% 3 5% 6% 22%	5181
	21st to end	Night	1 15% 12% 18% 8% 5% 4 2 4 6% 26%	7304

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	66% 5% 7% 13% 9% 1	3179
	11th to 20th	Day	54% 7% 11% 11% 10% 7%	3871
	21st to end	Day	49% 5% 7% 17% 16% 6%	4510
February	1st to 10th	Day	71% 4 8% 11% 5% 1	1800
	11th to 20th	Day	70% 4 9% 12% 3 2	1764
	21st to end	Day	71% 5% 4 10% 7% 3	1510
March	1st to 10th	Day	57% 5% 10% 16% 8% 5%	4940
	11th to 20th	Day	59% 5% 11% 17% 7% 1	5000
	21st to end	Day	76% 6% 8% 9% 1	5486
April	1st to 10th	Day	67% 5% 10% 14% 5%	2355
	11th to 20th	Day	63% 6% 11% 15% 4 1	2362
	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	33% 2 6% 28% 29% 1	3170
	11th to 20th	Day	34% 4 15% 27% 18% 1	3150
	21st to end	Day	48% 5% 14% 24% 9% 1	3413
November	1st to 10th	Day	54% 7% 12% 16% 9% 2	1628
	11th to 20th	Day	53% 7% 15% 16% 7% 2	1600
	21st to end	Day	51% 6% 15% 16% 10% 2	1600
December	1st to 10th	Day	48% 6% 16% 17% 10% 3	2620
	11th to 20th	Day	63% 6% 15% 14% 2 1	3024
	21st to end	Day	65% 4 5% 10% 6% 10%	3636
January	1st to 10th	Night	58% 6% 9% 12% 12% 2	6766
	11th to 20th	Night	51% 7% 11% 17% 8% 6%	6131
	21st to end	Night	49% 7% 8% 15% 15% 7%	6468
February	1st to 10th	Night	69% 6% 7% 11% 7% 1	2600
	11th to 20th	Night	65% 6% 9% 11% 6% 2	2533
	21st to end	Night	65% 7% 6% 10% 8% 3	2119
March	1st to 10th	Night	55% 6% 8% 14% 9% 7%	4953
	11th to 20th	Night	52% 6% 14% 20% 7% 1	5000
	21st to end	Night	63% 9% 11% 14% 3	5489
April	1st to 10th	Night	56% 6% 12% 18% 7%	2044
	11th to 20th	Night	52% 6% 16% 19% 5% 1	1771
	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	28% 4 9% 32% 26% 1	3800
	11th to 20th	Night	34% 4 14% 27% 19% 2	3778
	21st to end	Night	42% 8% 11% 26% 12% 1	4143
November	1st to 10th	Night	52% 6% 13% 18% 9% 2	2649
	11th to 20th	Night	53% 7% 16% 15% 7% 2	2800
	21st to end	Night	48% 7% 15% 14% 13% 3	2800
December	1st to 10th	Night	42% 7% 16% 21% 11% 2	4570
	11th to 20th	Night	60% 8% 15% 13% 3 1	5182
	21st to end	Night	61% 5% 7% 12% 7% 8%	7304

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	22% 22% 28% 20% 8% 1	200
	11th to 20th	Day	19% 28% 26% 14% 9% 5%	296
	21st to end	Day	15% 20% 40% 18% 7% 1	330
February	1st to 10th	Day	29% 30% 28% 10% 3	300
	11th to 20th	Day	33% 21% 28% 11% 3 3	300
	21st to end	Day	30% 27% 22% 17% 3	274
March	1st to 10th	Day	26% 30% 24% 15% 3 1	500
	11th to 20th	Day	22% 27% 29% 14% 7% 1	500
	21st to end	Day	24% 25% 30% 17% 4 1	550
April	1st to 10th	Day	29% 25% 33% 11% 2	500
	11th to 20th	Day	26% 28% 30% 12% 3	453
	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% 22% 28% 15% 4 2	330
November	1st to 10th	Day	26% 24% 24% 15% 8% 3	300
	11th to 20th	Day	28% 21% 31% 13% 5% 1	300
	21st to end	Day	16% 24% 33% 21% 6% 1	300
December	1st to 10th	Day	23% 24% 26% 18% 7% 3	300
	11th to 20th	Day	30% 25% 22% 18% 4 1	300
	21st to end	Day	26% 20% 34% 12% 5% 3	250
January	1st to 10th	Night	17% 25% 28% 23% 6% 1	1000
	11th to 20th	Night	18% 24% 28% 19% 8% 2	905
	21st to end	Night	13% 19% 34% 25% 7% 2	880
February	1st to 10th	Night	21% 25% 30% 19% 5% 1	800
	11th to 20th	Night	19% 21% 31% 22% 7%	784
	21st to end	Night	20% 26% 27% 18% 9% 1	660
March	1st to 10th	Night	19% 21% 30% 23% 6% 1	800
	11th to 20th	Night	18% 23% 24% 26% 10% 1	800
	21st to end	Night	15% 18% 31% 27% 8% 1	880
April	1st to 10th	Night	16% 21% 28% 27% 7% 1	644
	11th to 20th	Night	15% 18% 35% 24% 7% 1	565
	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% 24% 7% 3	836
November	1st to 10th	Night	19% 23% 32% 20% 5% 1	894
	11th to 20th	Night	22% 27% 27% 19% 4	1000
	21st to end	Night	18% 20% 26% 29% 6% 1	1000
December	1st to 10th	Night	19% 24% 29% 21% 7% 1	1000
	11th to 20th	Night	19% 27% 30% 19% 4 1	1000
	21st to end	Night	22% 24% 26% 18% 8% 2	1100

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