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 2026-08-15.

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 11% 5% 11% 6% 5% 5% 4 5% 7% 38%	153517
	Night	3 10% 5% 12% 6% 4 4 4 5% 7% 40%	145843
Transparency	Day	46% 7% 11% 19% 13% 3	148251
	Night	45% 7% 12% 20% 13% 3	142116
Seeing	Day	21% 18% 27% 21% 10% 3	18114
	Night	17% 17% 26% 28% 11% 1	27587

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	12% 11% 27% 10% 6% 5% 4 4 4 18%	4124
	11th to 20th	Day	1 8% 5% 13% 8% 7% 6% 4 5% 6% 38%	5055
	21st to end	Day	9% 8% 14% 7% 5% 4 3 4 7% 40%	5844
February	1st to 10th	Day	1 16% 9% 24% 10% 5% 4 2 4 5% 20%	1890
	11th to 20th	Day	13% 9% 26% 11% 6% 4 3 3 4 20%	1845
	21st to end	Day	1 16% 8% 19% 17% 6% 3 3 3 3 21%	1583
March	1st to 10th	Day	11% 8% 19% 11% 5% 4 2 3 4 32%	5049
	11th to 20th	Day	1 19% 9% 18% 6% 3 3 2 3 5% 32%	5110
	21st to end	Day	2 25% 12% 22% 6% 5% 5% 3 4 5% 13%	5607
April	1st to 10th	Day	3 23% 9% 15% 7% 4 3 4 5% 6% 21%	2473
	11th to 20th	Day	3 21% 6% 15% 6% 6% 5% 4 5% 5% 24%	2610
	21st to end	Day	5% 24% 8% 13% 6% 5% 4 3 4 6% 22%	2730
May	1st to 10th	Day	5% 11% 5% 9% 4 5% 5% 4 6% 8% 37%	7678
	11th to 20th	Day	5% 13% 4 10% 6% 6% 6% 5% 7% 8% 31%	8191
	21st to end	Day	7% 15% 4 8% 5% 5% 5% 4 6% 7% 33%	9026
June	1st to 10th	Day	11% 13% 3 6% 5% 5% 5% 5% 7% 8% 31%	2984
	11th to 20th	Day	12% 12% 3 7% 5% 5% 5% 5% 6% 7% 33%	3150
	21st to end	Day	5% 6% 2 5% 4 4 5% 5% 7% 7% 49%	3150
July	1st to 10th	Day	3 3 1 5% 4 6% 6% 5% 8% 10% 48%	8819
	11th to 20th	Day	3 3 1 5% 4 4 5% 5% 7% 8% 53%	8501
	21st to end	Day	4 4 2 6% 5% 6% 7% 6% 8% 9% 45%	8505
August	1st to 10th	Day	5% 4 2 6% 5% 5% 6% 5% 8% 9% 47%	5909
	11th to 20th	Day	3 3 2 5% 4 5% 5% 5% 7% 8% 52%	5851
	21st to end	Day	10% 6% 2 5% 4 3 4 3 5% 7% 52%	6346
September	1st to 10th	Day	8% 7% 2 5% 4 3 3 3 5% 6% 54%	2400
	11th to 20th	Day	9% 10% 3 7% 4 4 4 3 4 6% 46%	2262
	21st to end	Day	8% 10% 2 6% 4 3 4 3 5% 6% 49%	2190
October	1st to 10th	Day	5% 10% 3 5% 3 3 2 2 3 5% 59%	3270
	11th to 20th	Day	4 14% 3 6% 3 2 3 2 3 5% 54%	3250
	21st to end	Day	3 16% 7% 9% 4 4 4 3 5% 7% 39%	3522
November	1st to 10th	Day	6% 19% 5% 13% 4 4 4 3 5% 7% 32%	1711
	11th to 20th	Day	2 18% 7% 11% 6% 5% 3 3 5% 7% 32%	1680
	21st to end	Day	1 11% 7% 16% 7% 6% 4 3 5% 6% 35%	1680
December	1st to 10th	Day	9% 5% 16% 8% 6% 4 4 4 6% 38%	2700
	11th to 20th	Day	1 18% 9% 21% 6% 4 4 3 4 6% 23%	3106
	21st to end	Day	1 16% 13% 18% 8% 5% 4 3 4 5% 24%	3716
January	1st to 10th	Night	12% 10% 20% 13% 5% 4 3 4 5% 23%	8768
	11th to 20th	Night	5% 4 13% 9% 5% 5% 4 6% 8% 41%	7971
	21st to end	Night	1 11% 7% 13% 6% 5% 4 3 4 6% 40%	8370
February	1st to 10th	Night	1 15% 7% 21% 12% 7% 5% 4 4 6% 19%	2730
	11th to 20th	Night	1 11% 8% 24% 10% 6% 5% 4 5% 5% 22%	2662
	21st to end	Night	14% 8% 21% 13% 5% 4 3 4 5% 23%	2222
March	1st to 10th	Night	11% 6% 18% 13% 5% 3 2 3 5% 33%	5064
	11th to 20th	Night	1 14% 7% 16% 5% 4 4 3 4 5% 38%	5110
	21st to end	Night	1 20% 11% 17% 6% 4 5% 4 6% 7% 20%	5610
April	1st to 10th	Night	3 17% 7% 14% 6% 4 4 3 6% 6% 30%	2146
	11th to 20th	Night	2 13% 5% 12% 7% 4 5% 4 7% 8% 32%	1954
	21st to end	Night	4 17% 4 9% 6% 5% 4 4 6% 7% 35%	1890
May	1st to 10th	Night	3 8% 5% 9% 4 4 4 4 5% 7% 46%	5267
	11th to 20th	Night	5% 13% 3 6% 5% 5% 5% 4 6% 9% 39%	4701
	21st to end	Night	5% 13% 3 7% 4 4 5% 5% 8% 10% 37%	5181
June	1st to 10th	Night	11% 9% 2 7% 4 4 5% 4 7% 9% 37%	1630
	11th to 20th	Night	9% 10% 4 6% 5% 4 4 3 5% 7% 42%	1470
	21st to end	Night	5% 5% 2 4 3 4 5% 4 5% 7% 56%	1470
July	1st to 10th	Night	4 3 1 3 3 4 5% 5% 8% 10% 55%	4140
	11th to 20th	Night	4 2 1 4 3 4 4 5% 7% 10% 55%	4458
	21st to end	Night	2 3 1 4 4 4 5% 5% 7% 9% 56%	5587
August	1st to 10th	Night	4 5% 2 4 3 4 5% 4 7% 9% 52%	4123
	11th to 20th	Night	3 2 1 4 4 4 5% 4 7% 8% 58%	4087
	21st to end	Night	6% 6% 2 5% 3 3 3 3 4 5% 61%	4631
September	1st to 10th	Night	5% 5% 1 5% 3 4 4 3 5% 8% 55%	2000
	11th to 20th	Night	7% 8% 1 6% 4 3 4 3 5% 7% 50%	2135
	21st to end	Night	8% 8% 2 6% 3 2 2 3 4 6% 55%	2210
October	1st to 10th	Night	4 7% 2 5% 3 3 3 3 4 6% 60%	3920
	11th to 20th	Night	5% 11% 3 6% 4 3 3 3 4 6% 52%	3898
	21st to end	Night	4 12% 4 10% 4 3 3 3 6% 8% 42%	4276
November	1st to 10th	Night	5% 17% 5% 11% 5% 4 4 4 5% 7% 33%	2785
	11th to 20th	Night	2 16% 6% 14% 7% 4 4 4 5% 7% 31%	2940
	21st to end	Night	1 10% 4 15% 8% 6% 5% 4 5% 8% 35%	2940
December	1st to 10th	Night	8% 5% 15% 7% 5% 5% 4 5% 6% 42%	4710
	11th to 20th	Night	1 14% 8% 21% 8% 5% 5% 3 5% 6% 23%	5321
	21st to end	Night	1 15% 11% 18% 8% 5% 4 2 4 6% 26%	7466

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	70% 5% 8% 10% 7%	4125
	11th to 20th	Day	47% 8% 14% 11% 12% 7%	5055
	21st to end	Day	47% 6% 9% 17% 15% 6%	5844
February	1st to 10th	Day	69% 4 9% 11% 5% 1	1890
	11th to 20th	Day	70% 4 9% 12% 3 2	1854
	21st to end	Day	69% 5% 5% 11% 7% 3	1583
March	1st to 10th	Day	57% 5% 10% 15% 8% 5%	5049
	11th to 20th	Day	59% 5% 11% 18% 7% 1	5110
	21st to end	Day	75% 6% 9% 9% 1	5607
April	1st to 10th	Day	65% 6% 10% 14% 4	2473
	11th to 20th	Day	61% 6% 11% 16% 4 1	2613
	21st to end	Day	64% 6% 14% 13% 3 1	2730
May	1st to 10th	Day	43% 9% 13% 26% 7%	7678
	11th to 20th	Day	46% 10% 14% 21% 7% 1	8195
	21st to end	Day	46% 10% 16% 21% 7%	9027
June	1st to 10th	Day	48% 7% 20% 19% 5%	2984
	11th to 20th	Day	46% 7% 13% 20% 13% 2	3150
	21st to end	Day	30% 6% 14% 30% 17% 3	3150
July	1st to 10th	Day	27% 8% 11% 26% 24% 5%	8746
	11th to 20th	Day	25% 8% 10% 23% 23% 11%	8421
	21st to end	Day	32% 9% 9% 19% 27% 5%	8317
August	1st to 10th	Day	33% 8% 10% 19% 23% 7%	4338
	11th to 20th	Day	31% 7% 9% 24% 24% 5%	4250
	21st to end	Day	30% 5% 6% 24% 28% 6%	4577
September	1st to 10th	Day	31% 6% 5% 24% 29% 5%	2400
	11th to 20th	Day	40% 6% 9% 23% 19% 3	2262
	21st to end	Day	36% 5% 10% 28% 16% 4	2190
October	1st to 10th	Day	33% 3 6% 28% 29% 1	3270
	11th to 20th	Day	35% 4 15% 27% 18% 1	3250
	21st to end	Day	47% 5% 14% 24% 9% 1	3522
November	1st to 10th	Day	54% 7% 13% 16% 8% 2	1711
	11th to 20th	Day	54% 7% 15% 16% 7% 2	1680
	21st to end	Day	51% 6% 15% 15% 11% 2	1680
December	1st to 10th	Day	49% 6% 16% 16% 10% 3	2700
	11th to 20th	Day	63% 6% 14% 14% 2 1	3104
	21st to end	Day	65% 4 6% 10% 6% 10%	3716
January	1st to 10th	Night	64% 5% 10% 10% 10% 2	8769
	11th to 20th	Night	41% 8% 18% 17% 9% 7%	7971
	21st to end	Night	47% 6% 8% 15% 16% 8%	8370
February	1st to 10th	Night	68% 6% 8% 10% 6% 2	2730
	11th to 20th	Night	65% 6% 9% 11% 6% 2	2663
	21st to end	Night	65% 6% 6% 12% 8% 3	2222
March	1st to 10th	Night	55% 6% 8% 14% 9% 7%	5064
	11th to 20th	Night	52% 6% 14% 20% 7% 1	5110
	21st to end	Night	62% 9% 11% 14% 3	5610
April	1st to 10th	Night	56% 6% 12% 18% 7%	2146
	11th to 20th	Night	52% 6% 16% 19% 6% 1	1954
	21st to end	Night	49% 8% 17% 19% 7%	1890
May	1st to 10th	Night	37% 10% 13% 28% 12%	5265
	11th to 20th	Night	40% 10% 16% 25% 6% 3	4702
	21st to end	Night	38% 11% 18% 24% 8% 1	5182
June	1st to 10th	Night	42% 9% 19% 24% 6%	1630
	11th to 20th	Night	41% 6% 13% 23% 14% 2	1470
	21st to end	Night	27% 6% 15% 29% 19% 4	1470
July	1st to 10th	Night	22% 8% 9% 30% 28% 3	4105
	11th to 20th	Night	22% 6% 13% 25% 26% 8%	4415
	21st to end	Night	23% 6% 12% 27% 27% 4	5463
August	1st to 10th	Night	32% 6% 9% 23% 22% 8%	3018
	11th to 20th	Night	29% 5% 10% 27% 24% 5%	2964
	21st to end	Night	24% 4 7% 29% 31% 6%	3331
September	1st to 10th	Night	27% 6% 9% 25% 27% 6%	2000
	11th to 20th	Night	33% 6% 14% 25% 18% 4	2135
	21st to end	Night	32% 4 12% 31% 19% 2	2210
October	1st to 10th	Night	28% 4 9% 32% 26% 1	3920
	11th to 20th	Night	35% 4 14% 26% 18% 2	3898
	21st to end	Night	41% 7% 12% 27% 12% 1	4276
November	1st to 10th	Night	51% 6% 13% 18% 9% 2	2785
	11th to 20th	Night	53% 7% 16% 15% 6% 2	2940
	21st to end	Night	48% 7% 15% 14% 13% 3	2940
December	1st to 10th	Night	43% 7% 16% 21% 11% 2	4710
	11th to 20th	Night	60% 8% 15% 13% 3 1	5322
	21st to end	Night	61% 5% 8% 12% 7% 8%	7466

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	26% 22% 26% 18% 7% 1	220
	11th to 20th	Day	21% 29% 25% 12% 8% 4	326
	21st to end	Day	18% 21% 38% 17% 6% 1	363
February	1st to 10th	Day	28% 32% 27% 11% 3	330
	11th to 20th	Day	33% 21% 28% 12% 3 3	330
	21st to end	Day	34% 27% 20% 16% 3	299
March	1st to 10th	Day	26% 31% 24% 15% 3 1	540
	11th to 20th	Day	26% 26% 27% 13% 7% 1	540
	21st to end	Day	27% 25% 28% 16% 3 1	594
April	1st to 10th	Day	29% 25% 32% 11% 2	540
	11th to 20th	Day	29% 28% 30% 11% 3	532
	21st to end	Day	26% 20% 28% 18% 5% 3	540
May	1st to 10th	Day	20% 14% 29% 22% 11% 3	557
	11th to 20th	Day	20% 14% 26% 24% 13% 4	775
	21st to end	Day	23% 12% 20% 22% 17% 6%	844
June	1st to 10th	Day	19% 8% 22% 26% 19% 6%	780
	11th to 20th	Day	23% 15% 28% 24% 9% 2	780
	21st to end	Day	12% 9% 25% 33% 17% 4	780
July	1st to 10th	Day	7% 10% 23% 34% 21% 5%	771
	11th to 20th	Day	9% 13% 24% 34% 17% 3	768
	21st to end	Day	11% 12% 27% 29% 18% 4	693
August	1st to 10th	Day	16% 16% 26% 24% 14% 4	567
	11th to 20th	Day	10% 17% 26% 27% 14% 5%	534
	21st to end	Day	17% 16% 30% 20% 12% 5%	583
September	1st to 10th	Day	15% 16% 32% 25% 9% 4	530
	11th to 20th	Day	24% 19% 25% 18% 9% 4	530
	21st to end	Day	21% 21% 32% 15% 10% 2	520
October	1st to 10th	Day	22% 17% 27% 17% 13% 4	330
	11th to 20th	Day	28% 21% 22% 15% 11% 3	330
	21st to end	Day	29% 22% 27% 16% 4 1	363
November	1st to 10th	Day	28% 25% 23% 13% 7% 3	330
	11th to 20th	Day	30% 22% 29% 13% 5% 1	330
	21st to end	Day	16% 24% 32% 21% 5% 1	330
December	1st to 10th	Day	27% 23% 25% 16% 6% 3	330
	11th to 20th	Day	34% 25% 21% 17% 4 1	330
	21st to end	Day	30% 19% 33% 11% 5% 3	275
January	1st to 10th	Night	18% 26% 27% 22% 6% 1	1050
	11th to 20th	Night	18% 26% 28% 18% 8% 2	950
	21st to end	Night	14% 21% 34% 23% 6% 2	924
February	1st to 10th	Night	21% 25% 30% 18% 5% 1	840
	11th to 20th	Night	18% 21% 31% 22% 7%	824
	21st to end	Night	22% 25% 26% 17% 9% 1	692
March	1st to 10th	Night	20% 21% 30% 23% 6% 1	840
	11th to 20th	Night	19% 23% 22% 24% 9% 1	840
	21st to end	Night	16% 19% 30% 26% 8% 1	924
April	1st to 10th	Night	17% 20% 28% 27% 7% 1	676
	11th to 20th	Night	15% 19% 35% 23% 6% 1	623
	21st to end	Night	16% 13% 27% 31% 12% 1	630
May	1st to 10th	Night	14% 14% 22% 33% 15% 2	630
	11th to 20th	Night	16% 11% 21% 34% 17% 2	621
	21st to end	Night	18% 11% 20% 33% 15% 2	683
June	1st to 10th	Night	20% 8% 19% 32% 18% 2	580
	11th to 20th	Night	18% 12% 28% 31% 10% 1	420
	21st to end	Night	10% 5% 24% 42% 18% 2	420
July	1st to 10th	Night	5% 2 16% 44% 29% 4	410
	11th to 20th	Night	6% 4 28% 45% 15% 1	517
	21st to end	Night	8% 6% 23% 43% 18% 2	690
August	1st to 10th	Night	9% 5% 21% 44% 19% 2	627
	11th to 20th	Night	7% 5% 21% 44% 21% 2	606
	21st to end	Night	10% 8% 22% 39% 20% 1	660
September	1st to 10th	Night	11% 6% 24% 39% 17% 3	600
	11th to 20th	Night	13% 9% 21% 36% 18% 3	735
	21st to end	Night	16% 9% 22% 32% 18% 2	800
October	1st to 10th	Night	16% 12% 22% 33% 16% 2	800
	11th to 20th	Night	20% 14% 25% 29% 11% 2	800
	21st to end	Night	18% 18% 31% 24% 7% 3	880
November	1st to 10th	Night	20% 23% 31% 20% 5% 1	940
	11th to 20th	Night	22% 28% 27% 19% 4	1050
	21st to end	Night	18% 21% 26% 28% 6% 1	1050
December	1st to 10th	Night	20% 23% 29% 20% 7% 1	1050
	11th to 20th	Night	21% 26% 29% 18% 4 1	1050
	21st to end	Night	23% 24% 26% 17% 8% 2	1155

Page generated at 2026-08-12 01:37:17. Version ac07

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