Dead Horse Point State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dead Horse Point State Park clear sky chart from 2005-11-06 to 2025-09-19.

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 4 2 5% 4 4 4 4 6% 8% 58%	134617
	Night	3 5% 2 5% 4 4 4 4 6% 8% 55%	131934
Transparency	Day	24% 3 7% 20% 26% 20%	129447
	Night	27% 3 7% 22% 25% 17%	128107
Seeing	Day	7% 8% 19% 32% 25% 8%	16208
	Night	7% 4 14% 42% 29% 4	26471

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	2 6% 3 8% 5% 6% 7% 6% 8% 12% 37%	4098
	11th to 20th	Day	3 3 2 7% 6% 6% 7% 5% 7% 8% 47%	4100
	21st to end	Day	4 6% 2 7% 5% 4 5% 4 8% 10% 43%	4510
February	1st to 10th	Day	4 5% 3 9% 5% 5% 5% 5% 8% 11% 40%	1800
	11th to 20th	Day	5% 6% 2 9% 7% 5% 6% 4 7% 9% 40%	1755
	21st to end	Day	6% 7% 2 6% 5% 4 5% 5% 6% 8% 46%	1705
March	1st to 10th	Day	3 5% 2 6% 4 4 4 4 6% 7% 53%	4954
	11th to 20th	Day	4 10% 3 9% 5% 5% 5% 4 6% 7% 43%	5000
	21st to end	Day	5% 8% 3 8% 6% 5% 4 3 6% 7% 45%	5486
April	1st to 10th	Day	4 5% 2 5% 4 3 4 3 5% 7% 58%	2303
	11th to 20th	Day	3 5% 2 5% 4 4 4 4 6% 7% 57%	2371
	21st to end	Day	3 3 2 5% 4 4 4 4 5% 8% 60%	2530
May	1st to 10th	Day	4 4 2 5% 4 4 4 3 6% 7% 57%	5880
	11th to 20th	Day	2 3 1 5% 3 4 4 4 5% 8% 62%	5841
	21st to end	Day	2 2 1 3 3 3 3 3 5% 7% 69%	6423
June	1st to 10th	Day	2 2 1 3 2 3 3 3 5% 8% 68%	2785
	11th to 20th	Day	1 2 1 3 2 3 2 2 3 5% 75%	2800
	21st to end	Day	1 2 1 3 2 2 3 2 4 6% 74%	2703
July	1st to 10th	Day	2 1 1 2 2 2 3 3 4 5% 75%	5879
	11th to 20th	Day	1 2 1 3 3 3 4 4 8% 11% 60%	5880
	21st to end	Day	1 2 1 3 3 3 4 4 6% 8% 66%	6401
August	1st to 10th	Day	1 2 1 3 3 3 5% 4 7% 10% 62%	5779
	11th to 20th	Day	1 2 1 4 3 4 4 3 5% 7% 67%	5798
	21st to end	Day	4 3 1 4 4 4 5% 5% 7% 9% 55%	6082
September	1st to 10th	Day	4 2 1 4 3 3 4 4 5% 6% 65%	2400
	11th to 20th	Day	2 2 1 4 3 2 3 3 5% 7% 69%	2185
	21st to end	Day	3 3 1 3 2 2 2 2 4 5% 73%	2090
October	1st to 10th	Day	3 2 1 2 1 2 2 2 2 4 79%	3180
	11th to 20th	Day	6% 3 2 4 3 3 4 3 6% 8% 58%	3150
	21st to end	Day	2 2 1 3 3 3 3 3 5% 6% 68%	3438
November	1st to 10th	Day	4 4 1 4 2 2 2 2 5% 7% 67%	1959
	11th to 20th	Day	3 3 1 4 2 2 2 2 4 7% 69%	1780
	21st to end	Day	5% 5% 1 5% 3 4 4 4 5% 7% 58%	1600
December	1st to 10th	Day	3 5% 1 4 3 3 4 4 8% 10% 55%	2620
	11th to 20th	Day	4 4 2 7% 4 6% 8% 6% 8% 10% 42%	3026
	21st to end	Day	4 8% 3 8% 5% 5% 6% 5% 7% 14% 34%	4326
January	1st to 10th	Night	2 9% 3 8% 4 5% 5% 4 6% 8% 46%	5867
	11th to 20th	Night	2 4 2 5% 4 5% 6% 4 6% 8% 53%	5880
	21st to end	Night	5% 8% 4 7% 5% 4 4 3 6% 7% 47%	6468
February	1st to 10th	Night	2 6% 2 6% 4 5% 5% 5% 7% 11% 47%	2600
	11th to 20th	Night	5% 7% 3 7% 5% 5% 6% 5% 6% 7% 45%	2532
	21st to end	Night	4 8% 2 6% 5% 3 4 5% 8% 10% 45%	1920
March	1st to 10th	Night	5% 7% 2 6% 4 4 5% 3 5% 7% 53%	4940
	11th to 20th	Night	5% 8% 2 6% 5% 4 5% 4 6% 7% 47%	5000
	21st to end	Night	4 7% 2 7% 5% 4 5% 4 6% 7% 48%	5489
April	1st to 10th	Night	4 6% 2 6% 5% 4 4 3 5% 6% 55%	2095
	11th to 20th	Night	5% 5% 2 5% 4 4 5% 3 6% 7% 53%	1977
	21st to end	Night	4 5% 2 5% 4 3 4 3 6% 8% 57%	1866
May	1st to 10th	Night	5% 5% 2 5% 4 4 5% 4 5% 6% 54%	4100
	11th to 20th	Night	3 4 2 6% 4 4 5% 3 6% 8% 55%	4074
	21st to end	Night	3 3 1 3 3 3 3 3 4 7% 67%	4474
June	1st to 10th	Night	3 2 2 4 4 3 4 3 6% 8% 61%	1605
	11th to 20th	Night	3 3 1 3 3 3 4 4 5% 6% 66%	1600
	21st to end	Night	1 2 1 3 3 4 3 2 5% 6% 68%	1688
July	1st to 10th	Night	1 2 1 4 3 3 4 4 6% 7% 66%	4100
	11th to 20th	Night	1 3 2 5% 4 6% 7% 6% 8% 10% 49%	4100
	21st to end	Night	1 2 1 4 4 4 5% 4 7% 9% 59%	4472
August	1st to 10th	Night	2 2 1 5% 4 5% 6% 5% 7% 11% 52%	4033
	11th to 20th	Night	2 2 1 4 3 4 4 4 6% 8% 61%	4051
	21st to end	Night	3 3 1 6% 5% 5% 6% 5% 6% 8% 52%	4894
September	1st to 10th	Night	4 2 1 3 3 2 4 3 6% 7% 65%	2000
	11th to 20th	Night	3 3 1 4 3 3 3 3 4 7% 66%	2168
	21st to end	Night	4 2 1 3 3 3 3 2 3 4 72%	2090
October	1st to 10th	Night	4 1 1 2 2 2 2 2 3 6% 75%	3790
	11th to 20th	Night	4 5% 2 5% 4 4 4 3 6% 7% 57%	3778
	21st to end	Night	4 4 2 4 3 3 3 3 4 5% 66%	4120
November	1st to 10th	Night	2 4 1 4 3 3 3 3 5% 6% 66%	2340
	11th to 20th	Night	4 4 1 3 2 3 3 3 4 5% 68%	2592
	21st to end	Night	5% 5% 2 5% 3 3 3 4 5% 7% 58%	2800
December	1st to 10th	Night	3 3 1 4 2 2 4 3 8% 7% 62%	4570
	11th to 20th	Night	4 5% 2 5% 4 4 5% 6% 8% 9% 48%	5181
	21st to end	Night	5% 7% 3 7% 4 5% 5% 4 6% 11% 43%	6680

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	37% 3 15% 34% 10% 1	4099
	11th to 20th	Day	30% 3 12% 29% 18% 7%	4100
	21st to end	Day	33% 2 13% 25% 23% 4	4510
February	1st to 10th	Day	36% 4 16% 25% 15% 5%	1800
	11th to 20th	Day	37% 3 10% 28% 18% 4	1764
	21st to end	Day	34% 2 5% 26% 25% 6%	1705
March	1st to 10th	Day	29% 2 2 25% 31% 10%	4954
	11th to 20th	Day	41% 2 6% 23% 23% 5%	5000
	21st to end	Day	39% 2 5% 25% 25% 5%	5486
April	1st to 10th	Day	26% 3 4 22% 29% 16%	2303
	11th to 20th	Day	26% 3 4 22% 28% 17%	2374
	21st to end	Day	24% 2 4 20% 37% 13%	2530
May	1st to 10th	Day	27% 2 6% 14% 35% 15%	5880
	11th to 20th	Day	21% 3 2 16% 34% 23%	5844
	21st to end	Day	17% 2 2 11% 41% 27%	6424
June	1st to 10th	Day	16% 2 2 12% 34% 34%	2785
	11th to 20th	Day	14% 1 2 7% 22% 54%	2800
	21st to end	Day	14% 2 1 7% 21% 55%	2703
July	1st to 10th	Day	13% 3 3 6% 12% 64%	5816
	11th to 20th	Day	16% 4 3 16% 28% 33%	5811
	21st to end	Day	15% 4 5% 16% 24% 36%	6217
August	1st to 10th	Day	21% 4 9% 27% 18% 20%	4208
	11th to 20th	Day	21% 4 7% 17% 23% 28%	4197
	21st to end	Day	20% 4 7% 18% 26% 25%	4385
September	1st to 10th	Day	20% 3 4 13% 24% 36%	2400
	11th to 20th	Day	16% 3 5% 19% 22% 34%	2185
	21st to end	Day	16% 2 3 13% 37% 30%	2090
October	1st to 10th	Day	12% 2 4 14% 28% 40%	3180
	11th to 20th	Day	25% 3 3 21% 37% 11%	3150
	21st to end	Day	16% 3 8% 30% 37% 6%	3438
November	1st to 10th	Day	19% 2 7% 31% 33% 9%	1959
	11th to 20th	Day	18% 2 6% 38% 31% 4	1780
	21st to end	Day	26% 2 11% 33% 24% 3	1600
December	1st to 10th	Day	23% 6% 18% 34% 18% 1	2620
	11th to 20th	Day	31% 5% 23% 32% 10%	3024
	21st to end	Day	39% 4 13% 25% 18% 1	4326
January	1st to 10th	Night	36% 3 13% 31% 16% 2	5867
	11th to 20th	Night	27% 2 14% 27% 26% 4	5880
	21st to end	Night	36% 2 11% 24% 22% 5%	6468
February	1st to 10th	Night	30% 4 14% 30% 17% 5%	2600
	11th to 20th	Night	36% 4 7% 27% 21% 4	2533
	21st to end	Night	32% 3 6% 28% 24% 7%	1920
March	1st to 10th	Night	31% 2 2 21% 31% 12%	4940
	11th to 20th	Night	36% 2 5% 23% 26% 8%	5000
	21st to end	Night	36% 2 3 28% 27% 3	5489
April	1st to 10th	Night	29% 3 4 20% 29% 15%	2095
	11th to 20th	Night	31% 3 4 16% 30% 17%	1977
	21st to end	Night	26% 3 4 16% 37% 14%	1866
May	1st to 10th	Night	30% 3 5% 14% 32% 16%	4097
	11th to 20th	Night	27% 1 2 15% 36% 19%	4075
	21st to end	Night	19% 2 2 14% 37% 26%	4474
June	1st to 10th	Night	20% 3 2 10% 32% 33%	1605
	11th to 20th	Night	18% 3 3 7% 19% 49%	1600
	21st to end	Night	18% 2 1 8% 19% 52%	1688
July	1st to 10th	Night	17% 3 4 9% 10% 59%	4055
	11th to 20th	Night	25% 6% 4 13% 21% 31%	4046
	21st to end	Night	20% 4 5% 13% 22% 35%	4344
August	1st to 10th	Night	32% 5% 8% 20% 15% 20%	2928
	11th to 20th	Night	25% 3 8% 15% 18% 31%	2928
	21st to end	Night	22% 5% 7% 16% 22% 28%	3522
September	1st to 10th	Night	19% 3 4 14% 20% 40%	2000
	11th to 20th	Night	19% 2 6% 17% 21% 34%	2168
	21st to end	Night	18% 1 3 12% 29% 36%	2090
October	1st to 10th	Night	14% 2 3 12% 23% 45%	3790
	11th to 20th	Night	27% 3 4 14% 38% 15%	3778
	21st to end	Night	20% 2 6% 27% 36% 9%	4120
November	1st to 10th	Night	20% 2 4 23% 36% 14%	2340
	11th to 20th	Night	20% 2 5% 32% 36% 5%	2592
	21st to end	Night	26% 2 6% 26% 33% 7%	2800
December	1st to 10th	Night	19% 3 12% 44% 19% 2	4570
	11th to 20th	Night	29% 2 16% 41% 12%	5182
	21st to end	Night	36% 3 14% 31% 16% 1	6680

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	13% 4 16% 41% 17% 9%	300
	11th to 20th	Day	11% 4 16% 36% 28% 5%	300
	21st to end	Day	4 3 13% 46% 26% 8%	330
February	1st to 10th	Day	9% 6% 17% 44% 18% 6%	300
	11th to 20th	Day	11% 5% 24% 37% 20% 3	300
	21st to end	Day	10% 11% 21% 38% 18% 3	389
March	1st to 10th	Day	12% 11% 19% 35% 18% 4	500
	11th to 20th	Day	10% 12% 23% 32% 18% 4	500
	21st to end	Day	15% 17% 22% 29% 15% 2	550
April	1st to 10th	Day	9% 15% 25% 25% 21% 5%	500
	11th to 20th	Day	14% 15% 26% 28% 14% 3	492
	21st to end	Day	10% 15% 25% 25% 21% 4	500
May	1st to 10th	Day	9% 13% 28% 28% 18% 3	503
	11th to 20th	Day	7% 11% 25% 28% 23% 6%	528
	21st to end	Day	7% 13% 21% 29% 21% 8%	573
June	1st to 10th	Day	5% 7% 19% 30% 31% 10%	715
	11th to 20th	Day	4 10% 22% 31% 26% 6%	730
	21st to end	Day	4 9% 23% 32% 26% 6%	633
July	1st to 10th	Day	3 3 20% 31% 33% 10%	526
	11th to 20th	Day	2 2 13% 30% 38% 15%	524
	21st to end	Day	3 4 11% 30% 38% 13%	575
August	1st to 10th	Day	4 4 18% 33% 29% 12%	527
	11th to 20th	Day	3 4 13% 32% 34% 13%	517
	21st to end	Day	5% 3 15% 30% 35% 12%	583
September	1st to 10th	Day	4 4 13% 27% 33% 18%	530
	11th to 20th	Day	4 10% 21% 29% 26% 10%	523
	21st to end	Day	5% 9% 19% 24% 30% 13%	490
October	1st to 10th	Day	9% 7% 12% 25% 27% 18%	310
	11th to 20th	Day	9% 9% 13% 28% 27% 13%	300
	21st to end	Day	8% 9% 15% 33% 29% 5%	330
November	1st to 10th	Day	8% 10% 19% 27% 28% 8%	300
	11th to 20th	Day	4 4 21% 37% 24% 10%	300
	21st to end	Day	8% 5% 16% 37% 23% 10%	300
December	1st to 10th	Day	10% 4 14% 43% 18% 11%	300
	11th to 20th	Day	7% 4 15% 42% 28% 4	300
	21st to end	Day	15% 6% 13% 44% 16% 5%	330
January	1st to 10th	Night	8% 4 11% 44% 27% 5%	800
	11th to 20th	Night	7% 4 11% 45% 29% 4	800
	21st to end	Night	9% 3 14% 46% 22% 5%	880
February	1st to 10th	Night	7% 3 19% 48% 19% 4	800
	11th to 20th	Night	9% 4 19% 47% 19% 3	784
	21st to end	Night	10% 4 20% 49% 15% 1	660
March	1st to 10th	Night	9% 8% 19% 43% 21% 1	800
	11th to 20th	Night	8% 4 18% 42% 25% 3	800
	21st to end	Night	8% 8% 21% 46% 16% 2	880
April	1st to 10th	Night	7% 8% 24% 43% 16% 2	695
	11th to 20th	Night	8% 11% 20% 42% 18% 1	593
	21st to end	Night	9% 9% 23% 37% 20% 3	600
May	1st to 10th	Night	7% 7% 22% 42% 20% 2	600
	11th to 20th	Night	5% 5% 15% 44% 27% 3	591
	21st to end	Night	5% 9% 21% 36% 27% 2	650
June	1st to 10th	Night	3 5% 14% 42% 34% 2	600
	11th to 20th	Night	5% 6% 19% 40% 28% 3	600
	21st to end	Night	3 4 14% 43% 34% 3	600
July	1st to 10th	Night	2 2 11% 36% 43% 5%	585
	11th to 20th	Night	3 1 5% 34% 51% 5%	582
	21st to end	Night	3 1 6% 31% 52% 6%	657
August	1st to 10th	Night	4 2 5% 37% 46% 5%	597
	11th to 20th	Night	5% 2 6% 40% 42% 6%	594
	21st to end	Night	5% 2 8% 37% 42% 7%	660
September	1st to 10th	Night	5% 2 7% 38% 41% 7%	600
	11th to 20th	Night	3 2 13% 38% 38% 6%	782
	21st to end	Night	5% 3 12% 36% 36% 9%	760
October	1st to 10th	Night	8% 4 13% 41% 30% 5%	760
	11th to 20th	Night	5% 4 12% 42% 32% 6%	760
	21st to end	Night	8% 4 15% 38% 31% 5%	836
November	1st to 10th	Night	5% 3 14% 42% 30% 5%	780
	11th to 20th	Night	5% 3 13% 49% 26% 4	810
	21st to end	Night	9% 5% 14% 39% 27% 6%	1000
December	1st to 10th	Night	8% 4 12% 49% 23% 4	1000
	11th to 20th	Night	9% 4 13% 47% 25% 2	1000
	21st to end	Night	13% 4 12% 47% 20% 3	975

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