Flaming Gorge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Flaming Gorge Observatory clear sky chart from 2005-11-06 to 2026-05-02.

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 5% 2 6% 4 5% 5% 4 7% 8% 50%	140822
	Night	2 5% 2 6% 4 4 4 4 6% 8% 54%	139230
Transparency	Day	18% 38% 8% 15% 14% 7%	135612
	Night	18% 37% 9% 17% 13% 5%	135446
Seeing	Day	7% 11% 26% 31% 19% 6%	17432
	Night	5% 7% 27% 39% 18% 2	27706

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	1 8% 3 9% 5% 5% 5% 5% 9% 11% 39%	5120
	11th to 20th	Day	1 3 3 6% 5% 4 6% 5% 8% 8% 52%	5340
	21st to end	Day	6% 3 7% 4 5% 9% 5% 10% 9% 41%	5844
February	1st to 10th	Day	2 7% 3 7% 5% 4 4 4 7% 10% 47%	1890
	11th to 20th	Day	1 7% 3 8% 4 5% 5% 5% 8% 10% 44%	1845
	21st to end	Day	2 6% 2 6% 4 6% 5% 5% 7% 9% 47%	1694
March	1st to 10th	Day	1 9% 4 8% 5% 5% 5% 4 7% 8% 44%	5064
	11th to 20th	Day	3 11% 3 5% 4 5% 5% 5% 8% 11% 41%	5110
	21st to end	Day	3 9% 3 9% 7% 6% 5% 4 7% 9% 38%	5607
April	1st to 10th	Day	3 7% 3 6% 4 5% 4 5% 7% 10% 45%	2446
	11th to 20th	Day	7% 8% 3 7% 5% 4 4 5% 6% 9% 43%	2492
	21st to end	Day	5% 7% 2 6% 5% 4 6% 5% 7% 9% 43%	2730
May	1st to 10th	Day	6% 8% 2 5% 4 4 5% 4 6% 8% 46%	5894
	11th to 20th	Day	5% 6% 2 6% 4 5% 5% 5% 8% 8% 46%	5882
	21st to end	Day	4 5% 2 5% 4 4 5% 4 6% 9% 52%	6925
June	1st to 10th	Day	3 4 2 4 5% 5% 6% 5% 7% 9% 51%	2800
	11th to 20th	Day	4 5% 2 5% 3 4 4 4 6% 7% 56%	2800
	21st to end	Day	3 3 2 4 4 5% 4 4 6% 8% 58%	2800
July	1st to 10th	Day	3 3 1 4 4 4 5% 4 6% 6% 60%	6339
	11th to 20th	Day	2 3 2 6% 5% 7% 6% 5% 7% 8% 48%	5883
	21st to end	Day	2 4 1 5% 5% 5% 7% 5% 7% 8% 51%	6401
August	1st to 10th	Day	3 3 2 5% 4 5% 5% 5% 7% 8% 52%	5779
	11th to 20th	Day	2 3 1 5% 5% 6% 6% 5% 6% 8% 53%	5798
	21st to end	Day	4 4 2 6% 5% 5% 5% 4 5% 7% 52%	6187
September	1st to 10th	Day	4 3 1 4 3 4 4 4 6% 5% 60%	2400
	11th to 20th	Day	4 3 1 4 4 3 4 3 6% 8% 59%	2240
	21st to end	Day	5% 3 1 4 3 4 3 2 5% 5% 65%	2196
October	1st to 10th	Day	4 4 1 3 2 2 3 2 5% 5% 69%	3270
	11th to 20th	Day	8% 5% 2 4 3 3 3 2 4 8% 58%	3250
	21st to end	Day	5% 6% 2 3 2 3 4 3 5% 7% 61%	3548
November	1st to 10th	Day	3 5% 2 4 3 3 3 4 5% 9% 59%	1980
	11th to 20th	Day	2 6% 1 4 4 4 4 4 5% 8% 58%	1690
	21st to end	Day	1 5% 3 7% 4 4 5% 4 6% 8% 53%	1680
December	1st to 10th	Day	1 4 2 3 3 3 3 5% 9% 10% 57%	2700
	11th to 20th	Day	1 5% 2 4 4 3 4 4 8% 12% 53%	3106
	21st to end	Day	2 8% 4 10% 6% 6% 5% 5% 7% 10% 38%	4092
January	1st to 10th	Night	1 10% 4 9% 5% 5% 5% 5% 8% 9% 39%	7845
	11th to 20th	Night	1 3 2 8% 5% 4 4 4 8% 8% 52%	7650
	21st to end	Night	1 8% 3 9% 5% 6% 7% 4 8% 8% 41%	8370
February	1st to 10th	Night	1 6% 2 6% 4 4 5% 5% 7% 9% 50%	2730
	11th to 20th	Night	1 6% 3 6% 5% 5% 5% 4 7% 10% 47%	2662
	21st to end	Night	1 7% 3 7% 4 4 4 3 7% 9% 51%	2107
March	1st to 10th	Night	2 8% 3 8% 4 4 5% 4 6% 7% 49%	5050
	11th to 20th	Night	2 10% 4 7% 4 4 4 4 6% 9% 46%	5110
	21st to end	Night	2 9% 2 8% 6% 5% 5% 5% 6% 7% 44%	5610
April	1st to 10th	Night	4 6% 3 5% 4 3 4 4 6% 7% 53%	2174
	11th to 20th	Night	5% 10% 3 6% 4 3 5% 4 5% 7% 46%	2072
	21st to end	Night	4 7% 2 5% 4 4 5% 5% 7% 9% 49%	1890
May	1st to 10th	Night	9% 7% 2 6% 4 4 4 3 5% 7% 49%	4109
	11th to 20th	Night	5% 6% 2 6% 3 5% 4 4 6% 8% 51%	4033
	21st to end	Night	4 4 1 4 4 4 4 4 7% 9% 55%	3972
June	1st to 10th	Night	2 2 1 3 4 4 4 4 7% 9% 58%	1600
	11th to 20th	Night	4 3 1 3 3 3 3 3 7% 9% 62%	1600
	21st to end	Night	2 3 1 2 2 3 4 3 6% 6% 69%	1600
July	1st to 10th	Night	1 2 1 3 3 4 3 4 5% 6% 69%	3640
	11th to 20th	Night	2 2 1 3 3 3 4 4 7% 9% 62%	4092
	21st to end	Night	2 2 1 3 3 4 5% 4 8% 9% 60%	4472
August	1st to 10th	Night	1 2 1 3 2 3 4 4 6% 8% 65%	4033
	11th to 20th	Night	2 2 1 4 4 4 5% 4 6% 6% 62%	4051
	21st to end	Night	2 2 1 4 3 4 5% 4 7% 8% 60%	4790
September	1st to 10th	Night	3 2 1 2 2 2 3 3 4 7% 70%	2000
	11th to 20th	Night	3 2 1 2 3 3 3 3 5% 7% 68%	2156
	21st to end	Night	3 3 1 3 3 3 3 3 3 6% 69%	2202
October	1st to 10th	Night	2 3 1 2 2 2 3 2 4 5% 73%	3920
	11th to 20th	Night	6% 5% 2 4 3 3 3 3 4 6% 61%	3898
	21st to end	Night	6% 7% 2 4 3 3 3 3 5% 8% 58%	4252
November	1st to 10th	Night	2 5% 2 3 3 4 4 3 5% 9% 59%	2534
	11th to 20th	Night	2 5% 1 5% 3 4 4 4 6% 9% 57%	2907
	21st to end	Night	1 6% 3 5% 4 3 4 4 6% 7% 56%	2940
December	1st to 10th	Night	1 3 2 5% 4 3 5% 6% 9% 8% 55%	4710
	11th to 20th	Night	1 6% 2 5% 4 4 5% 4 7% 10% 53%	5321
	21st to end	Night	2 8% 4 8% 5% 5% 5% 5% 8% 10% 40%	7128

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	31% 25% 19% 17% 8%	5123
	11th to 20th	Day	21% 26% 13% 23% 14% 3	5340
	21st to end	Day	23% 27% 15% 20% 14% 1	5844
February	1st to 10th	Day	14% 61% 9% 10% 5% 2	1890
	11th to 20th	Day	13% 60% 5% 14% 7%	1854
	21st to end	Day	12% 60% 5% 13% 8% 2	1694
March	1st to 10th	Day	25% 31% 7% 21% 10% 6%	5064
	11th to 20th	Day	24% 32% 13% 15% 14% 1	5110
	21st to end	Day	27% 35% 13% 17% 7% 1	5607
April	1st to 10th	Day	13% 60% 7% 11% 8% 1	2446
	11th to 20th	Day	16% 60% 5% 9% 8% 1	2495
	21st to end	Day	17% 60% 4 11% 8% 1	2730
May	1st to 10th	Day	23% 34% 8% 15% 17% 4	5894
	11th to 20th	Day	22% 31% 7% 19% 18% 2	5885
	21st to end	Day	17% 33% 7% 22% 20% 1	6926
June	1st to 10th	Day	9% 63% 4 10% 11% 3	2800
	11th to 20th	Day	11% 62% 3 9% 10% 5%	2800
	21st to end	Day	10% 60% 2 7% 12% 8%	2800
July	1st to 10th	Day	14% 26% 3 6% 14% 35%	6271
	11th to 20th	Day	20% 28% 5% 10% 21% 17%	5813
	21st to end	Day	17% 27% 6% 11% 19% 19%	6217
August	1st to 10th	Day	15% 38% 6% 12% 15% 14%	4208
	11th to 20th	Day	18% 39% 7% 15% 15% 6%	4197
	21st to end	Day	14% 37% 6% 12% 17% 15%	4454
September	1st to 10th	Day	10% 58% 4 9% 14% 6%	2400
	11th to 20th	Day	10% 58% 3 10% 13% 6%	2240
	21st to end	Day	11% 57% 2 10% 13% 6%	2196
October	1st to 10th	Day	9% 35% 4 12% 22% 18%	3270
	11th to 20th	Day	18% 37% 4 18% 18% 5%	3250
	21st to end	Day	16% 36% 6% 23% 17% 2	3548
November	1st to 10th	Day	11% 53% 7% 15% 11% 2	1980
	11th to 20th	Day	13% 55% 6% 17% 9% 1	1690
	21st to end	Day	16% 55% 6% 15% 8%	1680
December	1st to 10th	Day	12% 37% 14% 29% 8% 1	2700
	11th to 20th	Day	14% 33% 19% 23% 11% 1	3104
	21st to end	Day	30% 29% 7% 17% 11% 5%	4092
January	1st to 10th	Night	32% 24% 18% 16% 8%	7846
	11th to 20th	Night	22% 23% 18% 25% 11% 2	7650
	21st to end	Night	25% 26% 15% 16% 16% 1	8370
February	1st to 10th	Night	14% 60% 8% 12% 5% 1	2730
	11th to 20th	Night	13% 59% 6% 12% 9% 1	2663
	21st to end	Night	11% 59% 6% 15% 8% 1	2107
March	1st to 10th	Night	25% 29% 8% 22% 10% 6%	5050
	11th to 20th	Night	27% 34% 10% 18% 11% 1	5110
	21st to end	Night	27% 32% 14% 17% 9% 1	5610
April	1st to 10th	Night	12% 60% 6% 14% 7% 1	2174
	11th to 20th	Night	17% 61% 4 11% 6% 1	2072
	21st to end	Night	16% 60% 5% 12% 7%	1890
May	1st to 10th	Night	23% 32% 7% 12% 18% 7%	4106
	11th to 20th	Night	22% 31% 9% 19% 15% 4	4034
	21st to end	Night	18% 30% 7% 26% 19%	3972
June	1st to 10th	Night	6% 62% 4 12% 13% 3	1600
	11th to 20th	Night	7% 62% 3 12% 12% 5%	1600
	21st to end	Night	7% 60% 3 8% 14% 9%	1600
July	1st to 10th	Night	12% 26% 4 6% 16% 36%	3600
	11th to 20th	Night	14% 26% 4 12% 22% 22%	4039
	21st to end	Night	12% 26% 8% 12% 25% 17%	4344
August	1st to 10th	Night	10% 36% 5% 15% 19% 16%	2928
	11th to 20th	Night	17% 38% 8% 14% 18% 6%	2928
	21st to end	Night	9% 36% 7% 13% 21% 14%	3454
September	1st to 10th	Night	6% 57% 3 13% 15% 7%	2000
	11th to 20th	Night	7% 57% 4 12% 15% 4	2156
	21st to end	Night	10% 57% 3 11% 14% 5%	2202
October	1st to 10th	Night	7% 35% 4 11% 29% 14%	3920
	11th to 20th	Night	18% 38% 4 18% 16% 7%	3898
	21st to end	Night	19% 37% 6% 24% 13% 2	4252
November	1st to 10th	Night	11% 54% 7% 17% 10% 1	2534
	11th to 20th	Night	11% 56% 5% 19% 7% 1	2907
	21st to end	Night	16% 56% 7% 14% 6% 1	2940
December	1st to 10th	Night	14% 39% 13% 24% 10%	4710
	11th to 20th	Night	15% 34% 17% 25% 8% 1	5322
	21st to end	Night	27% 30% 11% 17% 10% 5%	7128

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% 27% 38% 17% 3	330
	11th to 20th	Day	5% 15% 24% 38% 17% 1	330
	21st to end	Day	5% 7% 30% 39% 15% 3	363
February	1st to 10th	Day	7% 17% 40% 25% 8% 3	330
	11th to 20th	Day	5% 11% 35% 35% 12% 2	330
	21st to end	Day	6% 14% 29% 40% 10% 1	362
March	1st to 10th	Day	6% 14% 36% 32% 10% 3	540
	11th to 20th	Day	10% 15% 30% 30% 14% 1	540
	21st to end	Day	11% 18% 32% 26% 13%	594
April	1st to 10th	Day	10% 19% 26% 24% 17% 4	540
	11th to 20th	Day	13% 19% 31% 26% 9% 2	532
	21st to end	Day	12% 19% 28% 23% 14% 3	540
May	1st to 10th	Day	10% 18% 29% 24% 15% 4	508
	11th to 20th	Day	11% 14% 29% 28% 14% 5%	543
	21st to end	Day	11% 10% 22% 28% 23% 7%	789
June	1st to 10th	Day	5% 9% 22% 32% 26% 7%	730
	11th to 20th	Day	6% 13% 25% 32% 21% 3	730
	21st to end	Day	4 9% 24% 34% 23% 6%	730
July	1st to 10th	Day	4 3 18% 34% 31% 10%	721
	11th to 20th	Day	6% 5% 25% 30% 25% 10%	526
	21st to end	Day	4 4 18% 32% 30% 12%	575
August	1st to 10th	Day	5% 5% 20% 35% 24% 11%	527
	11th to 20th	Day	5% 5% 21% 31% 27% 10%	517
	21st to end	Day	5% 7% 23% 30% 24% 12%	583
September	1st to 10th	Day	6% 8% 21% 28% 23% 14%	530
	11th to 20th	Day	7% 12% 26% 28% 18% 9%	530
	21st to end	Day	6% 13% 20% 25% 26% 9%	526
October	1st to 10th	Day	8% 9% 21% 25% 29% 8%	330
	11th to 20th	Day	7% 15% 20% 28% 23% 7%	330
	21st to end	Day	8% 13% 25% 33% 18% 3	363
November	1st to 10th	Day	7% 21% 23% 29% 16% 5%	330
	11th to 20th	Day	7% 11% 26% 39% 12% 5%	330
	21st to end	Day	5% 10% 24% 41% 17% 4	330
December	1st to 10th	Day	6% 12% 27% 36% 17% 2	330
	11th to 20th	Day	4 11% 26% 44% 15% 1	330
	21st to end	Day	7% 11% 37% 28% 14% 2	363
January	1st to 10th	Night	5% 10% 31% 36% 15% 2	928
	11th to 20th	Night	5% 12% 32% 35% 14% 2	840
	21st to end	Night	5% 8% 33% 40% 11% 2	924
February	1st to 10th	Night	5% 11% 38% 36% 9% 2	840
	11th to 20th	Night	4 8% 39% 38% 11% 1	824
	21st to end	Night	4 6% 40% 43% 6%	692
March	1st to 10th	Night	6% 9% 33% 41% 11% 1	840
	11th to 20th	Night	5% 8% 29% 42% 15% 1	840
	21st to end	Night	6% 9% 37% 38% 10%	924
April	1st to 10th	Night	8% 10% 31% 40% 10%	704
	11th to 20th	Night	11% 12% 29% 36% 11% 1	623
	21st to end	Night	7% 11% 31% 36% 13% 1	630
May	1st to 10th	Night	9% 10% 27% 36% 16% 2	603
	11th to 20th	Night	9% 4 21% 41% 22% 3	591
	21st to end	Night	6% 5% 26% 36% 24% 2	650
June	1st to 10th	Night	3 6% 21% 40% 28% 2	600
	11th to 20th	Night	6% 6% 28% 42% 18%	600
	21st to end	Night	3 4 16% 47% 29% 2	600
July	1st to 10th	Night	4 2 13% 41% 39% 3	585
	11th to 20th	Night	3 2 12% 48% 34% 3	582
	21st to end	Night	4 1 8% 42% 41% 5%	657
August	1st to 10th	Night	4 1 13% 44% 35% 3	597
	11th to 20th	Night	4 2 11% 45% 36% 2	594
	21st to end	Night	2 2 14% 41% 37% 4	660
September	1st to 10th	Night	4 3 15% 41% 33% 5%	600
	11th to 20th	Night	3 3 18% 43% 26% 6%	756
	21st to end	Night	5% 4 19% 37% 26% 9%	800
October	1st to 10th	Night	6% 5% 25% 38% 23% 3	800
	11th to 20th	Night	7% 7% 27% 37% 19% 4	800
	21st to end	Night	8% 6% 28% 38% 17% 3	880
November	1st to 10th	Night	5% 9% 29% 39% 16% 3	820
	11th to 20th	Night	5% 11% 34% 37% 12% 2	1017
	21st to end	Night	5% 10% 28% 39% 16% 2	1050
December	1st to 10th	Night	5% 8% 32% 42% 12% 1	1050
	11th to 20th	Night	6% 8% 35% 40% 10% 1	1050
	21st to end	Night	6% 11% 38% 34% 9% 2	1155

Page generated at 2026-04-29 00:21:44. Version ac07

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