Colter Bay Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Colter Bay Campground clear sky chart from 2005-11-06 to 2026-03-18.

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	3 6% 3 7% 5% 5% 6% 5% 7% 8% 46%	140742
	Night	2 7% 3 8% 5% 6% 6% 5% 7% 8% 44%	138172
Transparency	Day	32% 9% 14% 22% 17% 6%	135469
	Night	31% 10% 16% 24% 15% 4	134450
Seeing	Day	7% 13% 30% 31% 15% 4	17366
	Night	6% 6% 24% 44% 18% 2	27114

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% 7% 14% 9% 10% 8% 5% 7% 7% 23%	4319
	11th to 20th	Day	5% 2 8% 7% 6% 6% 4 7% 8% 47%	5340
	21st to end	Day	8% 4 9% 6% 7% 6% 6% 8% 8% 38%	5844
February	1st to 10th	Day	2 10% 5% 14% 8% 8% 8% 6% 8% 7% 24%	1890
	11th to 20th	Day	1 11% 6% 13% 10% 8% 8% 5% 6% 8% 25%	1845
	21st to end	Day	1 11% 4 15% 8% 7% 8% 6% 6% 8% 25%	1651
March	1st to 10th	Day	1 8% 4 11% 6% 6% 7% 5% 7% 8% 37%	4992
	11th to 20th	Day	1 11% 5% 11% 7% 6% 6% 4 6% 7% 36%	5078
	21st to end	Day	1 11% 5% 13% 9% 7% 8% 7% 9% 9% 21%	5486
April	1st to 10th	Day	4 11% 4 10% 8% 6% 6% 5% 7% 7% 30%	2311
	11th to 20th	Day	4 9% 4 9% 7% 8% 6% 6% 7% 7% 33%	2510
	21st to end	Day	5% 12% 4 8% 6% 6% 6% 5% 7% 10% 32%	2600
May	1st to 10th	Day	5% 7% 3 7% 4 5% 5% 5% 7% 7% 45%	5880
	11th to 20th	Day	5% 5% 2 6% 4 5% 6% 5% 8% 10% 43%	6086
	21st to end	Day	5% 7% 2 6% 5% 5% 5% 5% 7% 8% 44%	6925
June	1st to 10th	Day	7% 5% 2 6% 5% 5% 5% 5% 7% 9% 43%	2807
	11th to 20th	Day	8% 6% 2 5% 5% 4 6% 4 7% 8% 47%	3000
	21st to end	Day	2 2 1 3 3 3 3 3 6% 9% 65%	3000
July	1st to 10th	Day	1 2 1 3 3 4 4 4 6% 8% 66%	6779
	11th to 20th	Day	1 1 1 2 3 3 4 4 6% 7% 67%	6325
	21st to end	Day	2 2 1 3 3 4 5% 5% 8% 9% 58%	6401
August	1st to 10th	Day	2 2 1 3 4 4 6% 5% 8% 9% 57%	5779
	11th to 20th	Day	1 1 1 3 3 4 5% 4 6% 8% 63%	5798
	21st to end	Day	4 3 1 4 3 3 3 3 5% 6% 63%	6390
September	1st to 10th	Day	4 4 1 3 3 4 4 3 6% 8% 60%	2398
	11th to 20th	Day	5% 4 1 5% 4 4 5% 4 6% 8% 53%	2200
	21st to end	Day	6% 5% 2 5% 3 3 3 3 5% 8% 58%	2200
October	1st to 10th	Day	5% 5% 2 4 3 3 3 3 5% 5% 61%	3312
	11th to 20th	Day	3 7% 2 6% 4 4 3 4 4 6% 57%	3250
	21st to end	Day	2 9% 3 8% 5% 6% 6% 5% 7% 8% 41%	3497
November	1st to 10th	Day	4 11% 5% 10% 5% 5% 5% 5% 6% 8% 35%	1804
	11th to 20th	Day	2 12% 4 10% 8% 5% 6% 4 6% 6% 36%	1680
	21st to end	Day	1 9% 5% 12% 5% 6% 7% 5% 7% 6% 38%	1680
December	1st to 10th	Day	1 6% 4 10% 6% 6% 5% 4 6% 6% 46%	2700
	11th to 20th	Day	1 9% 6% 14% 7% 7% 8% 6% 10% 9% 24%	3106
	21st to end	Day	1 12% 5% 14% 8% 7% 7% 6% 8% 9% 23%	3879
January	1st to 10th	Night	5% 5% 15% 9% 10% 10% 7% 8% 9% 23%	8589
	11th to 20th	Night	4 4 10% 9% 7% 6% 5% 7% 9% 39%	7650
	21st to end	Night	10% 3 9% 7% 8% 7% 5% 9% 10% 30%	8370
February	1st to 10th	Night	2 10% 5% 14% 9% 9% 7% 6% 7% 9% 23%	2730
	11th to 20th	Night	9% 5% 15% 8% 8% 7% 5% 8% 8% 27%	2662
	21st to end	Night	1 8% 3 14% 9% 9% 8% 5% 9% 8% 26%	2152
March	1st to 10th	Night	1 11% 5% 11% 7% 7% 7% 5% 9% 7% 30%	5121
	11th to 20th	Night	1 10% 4 9% 5% 5% 5% 4 6% 8% 42%	5077
	21st to end	Night	2 10% 4 10% 7% 7% 6% 6% 10% 10% 28%	5489
April	1st to 10th	Night	2 10% 4 9% 6% 5% 6% 6% 8% 9% 35%	2087
	11th to 20th	Night	4 6% 3 9% 6% 5% 5% 4 6% 8% 42%	1835
	21st to end	Night	4 10% 4 7% 5% 5% 5% 5% 6% 8% 43%	1800
May	1st to 10th	Night	3 7% 3 7% 3 4 4 4 6% 7% 52%	4100
	11th to 20th	Night	6% 7% 2 6% 4 5% 5% 5% 6% 10% 45%	3813
	21st to end	Night	4 6% 2 5% 3 4 5% 4 8% 11% 48%	3972
June	1st to 10th	Night	7% 5% 1 6% 4 5% 5% 6% 7% 9% 46%	1588
	11th to 20th	Night	8% 3 2 4 4 4 3 4 5% 9% 54%	1400
	21st to end	Night	3 1 1 2 2 3 3 3 5% 8% 70%	1400
July	1st to 10th	Night	1 2 1 2 2 3 3 3 6% 7% 70%	3180
	11th to 20th	Night	1 2 2 2 3 3 5% 10% 72%	3630
	21st to end	Night	1 1 1 2 2 3 4 4 7% 8% 68%	4472
August	1st to 10th	Night	2 1 1 3 3 3 4 4 8% 9% 63%	4033
	11th to 20th	Night	1 1 1 3 2 3 4 4 6% 8% 67%	4051
	21st to end	Night	4 3 1 4 3 3 3 3 4 7% 64%	4587
September	1st to 10th	Night	4 3 1 3 2 3 4 3 4 6% 67%	2000
	11th to 20th	Night	4 4 1 4 4 4 5% 4 6% 6% 58%	2199
	21st to end	Night	7% 4 1 3 2 3 3 3 4 6% 64%	2200
October	1st to 10th	Night	4 5% 2 4 2 2 3 2 3 5% 69%	3878
	11th to 20th	Night	4 6% 2 6% 4 4 4 3 6% 6% 55%	3898
	21st to end	Night	3 8% 3 6% 4 4 5% 4 7% 9% 48%	4299
November	1st to 10th	Night	4 11% 4 8% 5% 5% 6% 4 7% 9% 38%	2691
	11th to 20th	Night	2 10% 4 8% 6% 6% 6% 5% 9% 10% 35%	2940
	21st to end	Night	1 7% 3 9% 5% 6% 6% 7% 8% 11% 36%	2940
December	1st to 10th	Night	1 7% 3 10% 7% 6% 5% 4 6% 9% 44%	4710
	11th to 20th	Night	1 9% 5% 14% 7% 6% 7% 6% 10% 11% 26%	5321
	21st to end	Night	1 11% 6% 14% 9% 8% 8% 6% 8% 8% 22%	7308

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	46% 15% 20% 12% 6%	4320
	11th to 20th	Day	30% 9% 24% 20% 12% 5%	5340
	21st to end	Day	35% 11% 16% 21% 13% 3	5844
February	1st to 10th	Day	54% 12% 15% 15% 4 1	1890
	11th to 20th	Day	52% 11% 16% 14% 5% 2	1854
	21st to end	Day	54% 8% 10% 18% 8% 2	1651
March	1st to 10th	Day	42% 7% 15% 20% 13% 3	4992
	11th to 20th	Day	38% 10% 19% 23% 9% 1	5078
	21st to end	Day	47% 15% 19% 16% 2	5486
April	1st to 10th	Day	51% 8% 14% 17% 8% 1	2311
	11th to 20th	Day	48% 7% 14% 21% 9% 1	2513
	21st to end	Day	46% 11% 14% 24% 5%	2600
May	1st to 10th	Day	35% 7% 15% 30% 13% 1	5880
	11th to 20th	Day	29% 10% 16% 30% 13% 3	6090
	21st to end	Day	33% 9% 13% 31% 13%	6926
June	1st to 10th	Day	35% 10% 17% 27% 10% 1	2807
	11th to 20th	Day	33% 8% 11% 23% 20% 7%	3000
	21st to end	Day	16% 6% 8% 29% 30% 11%	3000
July	1st to 10th	Day	14% 5% 6% 18% 33% 24%	6706
	11th to 20th	Day	12% 6% 7% 19% 29% 27%	6246
	21st to end	Day	16% 6% 8% 23% 34% 14%	6217
August	1st to 10th	Day	19% 7% 8% 21% 28% 17%	4208
	11th to 20th	Day	16% 7% 9% 25% 31% 12%	4197
	21st to end	Day	17% 5% 7% 22% 34% 15%	4609
September	1st to 10th	Day	22% 6% 9% 20% 32% 11%	2398
	11th to 20th	Day	27% 7% 11% 24% 24% 7%	2200
	21st to end	Day	26% 5% 12% 30% 22% 5%	2200
October	1st to 10th	Day	24% 5% 9% 23% 34% 5%	3312
	11th to 20th	Day	27% 6% 14% 34% 17% 2	3250
	21st to end	Day	32% 11% 20% 26% 9% 1	3497
November	1st to 10th	Day	44% 8% 16% 24% 8% 1	1804
	11th to 20th	Day	46% 10% 19% 18% 6% 1	1680
	21st to end	Day	42% 8% 20% 20% 9% 1	1680
December	1st to 10th	Day	34% 12% 25% 22% 5% 1	2700
	11th to 20th	Day	42% 17% 22% 16% 2	3104
	21st to end	Day	46% 11% 17% 14% 8% 4	3879
January	1st to 10th	Night	41% 16% 18% 18% 6%	8590
	11th to 20th	Night	34% 10% 23% 22% 8% 3	7650
	21st to end	Night	35% 12% 19% 18% 12% 3	8370
February	1st to 10th	Night	52% 11% 15% 14% 7%	2730
	11th to 20th	Night	48% 11% 14% 18% 7% 1	2663
	21st to end	Night	50% 9% 12% 18% 9% 1	2152
March	1st to 10th	Night	43% 9% 15% 22% 10% 2	5121
	11th to 20th	Night	32% 9% 19% 31% 8% 1	5077
	21st to end	Night	37% 14% 23% 22% 2	5489
April	1st to 10th	Night	41% 11% 18% 19% 10% 1	2087
	11th to 20th	Night	38% 8% 19% 24% 9% 2	1835
	21st to end	Night	37% 8% 19% 29% 7%	1800
May	1st to 10th	Night	31% 7% 15% 32% 13% 1	4097
	11th to 20th	Night	27% 9% 18% 34% 11% 2	3814
	21st to end	Night	25% 8% 19% 33% 14% 1	3972
June	1st to 10th	Night	32% 11% 18% 27% 11% 1	1588
	11th to 20th	Night	25% 8% 14% 25% 21% 7%	1400
	21st to end	Night	13% 6% 10% 29% 31% 11%	1400
July	1st to 10th	Night	11% 4 8% 20% 37% 19%	3145
	11th to 20th	Night	7% 3 6% 23% 39% 22%	3586
	21st to end	Night	10% 5% 8% 22% 36% 18%	4344
August	1st to 10th	Night	16% 5% 8% 25% 31% 15%	2928
	11th to 20th	Night	17% 5% 10% 31% 24% 13%	2928
	21st to end	Night	15% 5% 6% 24% 36% 14%	3299
September	1st to 10th	Night	18% 5% 8% 22% 33% 14%	2000
	11th to 20th	Night	24% 8% 11% 24% 26% 8%	2199
	21st to end	Night	22% 6% 10% 32% 26% 5%	2200
October	1st to 10th	Night	20% 4 9% 29% 34% 4	3878
	11th to 20th	Night	26% 7% 13% 36% 16% 1	3898
	21st to end	Night	26% 11% 19% 29% 14% 1	4299
November	1st to 10th	Night	39% 10% 17% 23% 10% 1	2691
	11th to 20th	Night	39% 10% 21% 21% 7% 1	2940
	21st to end	Night	37% 11% 20% 21% 10% 1	2940
December	1st to 10th	Night	32% 14% 23% 24% 7% 1	4710
	11th to 20th	Night	40% 15% 26% 16% 2	5322
	21st to end	Night	44% 14% 17% 15% 8% 2	7308

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	4 11% 31% 35% 15% 3	241
	11th to 20th	Day	4 8% 32% 42% 9% 5%	330
	21st to end	Day	2 8% 33% 44% 11% 2	363
February	1st to 10th	Day	9% 19% 36% 28% 7% 1	330
	11th to 20th	Day	6% 15% 33% 35% 11% 1	330
	21st to end	Day	7% 20% 38% 26% 9%	367
March	1st to 10th	Day	7% 20% 37% 28% 7% 1	540
	11th to 20th	Day	8% 20% 32% 29% 9% 2	529
	21st to end	Day	10% 21% 33% 28% 7% 1	550
April	1st to 10th	Day	12% 20% 34% 23% 10% 1	500
	11th to 20th	Day	9% 23% 35% 22% 10% 1	492
	21st to end	Day	12% 17% 31% 22% 15% 3	500
May	1st to 10th	Day	8% 18% 30% 26% 14% 4	503
	11th to 20th	Day	11% 13% 29% 28% 15% 3	630
	21st to end	Day	11% 12% 24% 30% 20% 4	789
June	1st to 10th	Day	7% 15% 25% 29% 20% 5%	730
	11th to 20th	Day	10% 17% 33% 28% 12% 1	730
	21st to end	Day	4 10% 30% 34% 18% 4	730
July	1st to 10th	Day	2 7% 26% 36% 25% 4	721
	11th to 20th	Day	2 8% 30% 37% 20% 2	654
	21st to end	Day	3 7% 30% 35% 21% 4	575
August	1st to 10th	Day	6% 9% 27% 34% 21% 3	527
	11th to 20th	Day	3 7% 27% 35% 20% 8%	517
	21st to end	Day	6% 11% 26% 33% 17% 7%	583
September	1st to 10th	Day	4 9% 27% 30% 23% 7%	530
	11th to 20th	Day	8% 12% 28% 28% 18% 6%	530
	21st to end	Day	8% 11% 23% 29% 22% 6%	530
October	1st to 10th	Day	6% 8% 26% 31% 19% 9%	359
	11th to 20th	Day	8% 15% 24% 25% 18% 10%	330
	21st to end	Day	8% 15% 31% 33% 11% 3	363
November	1st to 10th	Day	8% 15% 33% 31% 8% 5%	330
	11th to 20th	Day	7% 14% 28% 37% 12% 2	330
	21st to end	Day	3 7% 33% 39% 16% 2	330
December	1st to 10th	Day	4 14% 27% 38% 14% 3	330
	11th to 20th	Day	7% 11% 36% 36% 9%	330
	21st to end	Day	9% 15% 30% 31% 11% 4	313
January	1st to 10th	Night	3 7% 32% 44% 12% 2	1043
	11th to 20th	Night	4 6% 31% 46% 11% 2	840
	21st to end	Night	3 5% 31% 49% 10% 2	924
February	1st to 10th	Night	4 8% 34% 44% 9% 1	840
	11th to 20th	Night	3 7% 31% 47% 11% 1	824
	21st to end	Night	5% 11% 34% 38% 11% 2	692
March	1st to 10th	Night	4 9% 28% 46% 12% 1	840
	11th to 20th	Night	5% 8% 24% 47% 15% 1	828
	21st to end	Night	6% 8% 26% 45% 14% 1	880
April	1st to 10th	Night	7% 10% 27% 40% 15% 1	687
	11th to 20th	Night	7% 8% 32% 41% 12%	593
	21st to end	Night	7% 8% 25% 40% 19% 1	600
May	1st to 10th	Night	10% 7% 22% 38% 23% 1	600
	11th to 20th	Night	10% 4 22% 37% 25% 3	591
	21st to end	Night	11% 5% 20% 36% 24% 3	650
June	1st to 10th	Night	10% 8% 19% 35% 26% 2	588
	11th to 20th	Night	9% 7% 19% 47% 18%	400
	21st to end	Night	3 1 12% 51% 31% 3	400
July	1st to 10th	Night	2 10% 46% 41% 2	390
	11th to 20th	Night	1 2 14% 46% 36% 1	516
	21st to end	Night	2 1 9% 52% 34% 3	657
August	1st to 10th	Night	5% 2 10% 48% 32% 2	597
	11th to 20th	Night	2 2 10% 45% 38% 3	594
	21st to end	Night	4 2 15% 40% 35% 3	660
September	1st to 10th	Night	5% 1 14% 44% 33% 3	600
	11th to 20th	Night	5% 4 12% 43% 30% 6%	799
	21st to end	Night	8% 5% 13% 42% 28% 5%	800
October	1st to 10th	Night	9% 6% 19% 40% 23% 4	800
	11th to 20th	Night	9% 7% 20% 41% 20% 3	800
	21st to end	Night	6% 8% 21% 49% 13% 3	880
November	1st to 10th	Night	8% 7% 26% 45% 13% 1	846
	11th to 20th	Night	6% 11% 30% 43% 8% 1	1050
	21st to end	Night	4 7% 28% 48% 12% 1	1050
December	1st to 10th	Night	4 10% 28% 45% 11% 2	1050
	11th to 20th	Night	7% 8% 30% 44% 9% 1	1050
	21st to end	Night	7% 9% 31% 40% 11% 2	1155

Page generated at 2026-03-15 00:23:54. Version ac07

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