Red Rock RV Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Red Rock RV 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	5% 10% 4 8% 5% 4 5% 4 6% 7% 42%	135190
	Night	6% 11% 4 9% 5% 4 4 4 6% 7% 39%	131213
Transparency	Day	40% 6% 11% 21% 16% 6%	129889
	Night	43% 6% 12% 21% 13% 4	127517
Seeing	Day	16% 16% 31% 24% 11% 2	16603
	Night	15% 8% 25% 36% 15% 1	26069

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	4 19% 8% 20% 9% 5% 5% 3 4 4 19%	3267
	11th to 20th	Day	4 13% 5% 15% 10% 7% 5% 3 5% 5% 28%	3701
	21st to end	Day	4 23% 7% 10% 5% 4 4 3 4 4 34%	4510
February	1st to 10th	Day	7% 20% 8% 14% 8% 6% 4 4 4 5% 20%	1800
	11th to 20th	Day	6% 18% 8% 16% 7% 5% 5% 4 5% 5% 22%	1755
	21st to end	Day	5% 23% 9% 16% 8% 4 4 3 4 4 20%	1605
March	1st to 10th	Day	3 14% 7% 13% 6% 5% 4 4 5% 6% 34%	4782
	11th to 20th	Day	4 18% 6% 9% 5% 4 4 3 5% 6% 35%	5000
	21st to end	Day	4 19% 7% 14% 8% 7% 7% 4 6% 6% 18%	5486
April	1st to 10th	Day	8% 19% 5% 10% 7% 5% 4 3 6% 5% 28%	2292
	11th to 20th	Day	7% 14% 4 11% 6% 5% 5% 3 5% 7% 32%	2567
	21st to end	Day	8% 14% 4 11% 5% 4 5% 3 6% 8% 30%	2600
May	1st to 10th	Day	6% 11% 3 7% 5% 4 5% 4 6% 7% 41%	5880
	11th to 20th	Day	7% 9% 3 9% 6% 6% 7% 5% 7% 8% 32%	6041
	21st to end	Day	7% 10% 3 8% 5% 5% 5% 4 5% 7% 41%	6925
June	1st to 10th	Day	12% 8% 3 7% 6% 5% 5% 4 7% 8% 35%	2968
	11th to 20th	Day	11% 7% 3 7% 5% 5% 5% 4 6% 7% 39%	3000
	21st to end	Day	3 4 1 5% 4 4 5% 4 6% 8% 57%	3000
July	1st to 10th	Day	2 1 1 4 3 4 5% 5% 7% 8% 60%	6779
	11th to 20th	Day	1 1 1 3 3 4 5% 5% 6% 9% 62%	6581
	21st to end	Day	1 2 1 3 3 4 4 4 6% 8% 63%	6411
August	1st to 10th	Day	3 2 1 5% 4 5% 6% 5% 8% 11% 51%	5779
	11th to 20th	Day	2 2 1 3 2 3 3 3 6% 8% 67%	5798
	21st to end	Day	7% 4 1 4 3 3 4 4 5% 6% 58%	6468
September	1st to 10th	Day	5% 4 1 4 3 4 3 3 5% 7% 62%	2366
	11th to 20th	Day	8% 6% 2 5% 4 3 4 4 5% 8% 51%	2179
	21st to end	Day	8% 6% 1 5% 3 3 3 3 5% 7% 56%	2090
October	1st to 10th	Day	6% 6% 2 5% 4 3 3 3 4 4 60%	3251
	11th to 20th	Day	7% 7% 3 5% 3 3 3 2 3 6% 58%	3150
	21st to end	Day	7% 12% 4 8% 4 5% 5% 4 6% 7% 39%	3291
November	1st to 10th	Day	12% 16% 5% 8% 5% 3 5% 2 6% 6% 32%	1739
	11th to 20th	Day	8% 15% 5% 9% 5% 5% 5% 4 5% 7% 32%	1600
	21st to end	Day	5% 17% 6% 12% 6% 5% 4 3 5% 6% 31%	1600
December	1st to 10th	Day	4 10% 5% 10% 5% 5% 5% 3 4 6% 42%	2620
	11th to 20th	Day	7% 21% 9% 16% 9% 6% 4 3 5% 5% 15%	2811
	21st to end	Day	6% 21% 8% 15% 6% 4 5% 3 5% 5% 22%	3498
January	1st to 10th	Night	4 16% 7% 17% 10% 6% 5% 5% 6% 5% 20%	6720
	11th to 20th	Night	5% 13% 5% 15% 9% 8% 5% 3 6% 7% 24%	6259
	21st to end	Night	5% 21% 7% 10% 4 4 3 3 4 5% 33%	6468
February	1st to 10th	Night	7% 19% 8% 15% 7% 5% 4 3 5% 5% 23%	2600
	11th to 20th	Night	7% 18% 7% 14% 7% 5% 4 3 4 6% 24%	2532
	21st to end	Night	6% 16% 6% 17% 9% 7% 4 3 5% 4 23%	2020
March	1st to 10th	Night	3 15% 6% 15% 6% 4 4 3 4 5% 35%	5099
	11th to 20th	Night	4 14% 5% 7% 4 4 4 4 6% 7% 40%	5000
	21st to end	Night	5% 17% 5% 10% 5% 5% 5% 5% 7% 8% 27%	5489
April	1st to 10th	Night	9% 14% 5% 10% 6% 4 4 4 5% 6% 33%	2105
	11th to 20th	Night	9% 8% 3 7% 4 5% 5% 3 6% 8% 42%	1781
	21st to end	Night	10% 12% 3 7% 5% 4 4 3 7% 8% 38%	1800
May	1st to 10th	Night	7% 9% 2 6% 5% 4 5% 3 5% 7% 46%	4100
	11th to 20th	Night	9% 11% 2 8% 6% 5% 5% 5% 7% 7% 35%	3859
	21st to end	Night	9% 9% 2 7% 4 5% 6% 4 8% 9% 38%	3972
June	1st to 10th	Night	10% 5% 2 6% 5% 5% 5% 6% 7% 7% 41%	1429
	11th to 20th	Night	11% 6% 2 7% 5% 5% 5% 4 6% 6% 45%	1400
	21st to end	Night	3 2 1 4 3 3 5% 4 5% 7% 62%	1400
July	1st to 10th	Night	2 2 1 4 3 3 4 4 6% 7% 64%	3180
	11th to 20th	Night	2 2 1 3 3 3 4 3 6% 8% 63%	3361
	21st to end	Night	2 2 1 4 4 4 5% 4 7% 9% 58%	4458
August	1st to 10th	Night	3 2 1 4 4 5% 6% 5% 8% 10% 52%	4033
	11th to 20th	Night	1 1 1 4 3 4 4 4 6% 7% 66%	4051
	21st to end	Night	8% 5% 2 4 3 3 3 3 4 7% 59%	4509
September	1st to 10th	Night	5% 4 2 4 4 3 3 3 5% 6% 61%	2030
	11th to 20th	Night	7% 5% 2 4 4 4 5% 3 6% 7% 54%	2178
	21st to end	Night	8% 5% 2 3 3 3 3 3 4 6% 60%	2090
October	1st to 10th	Night	5% 5% 1 3 3 3 3 2 4 5% 66%	3707
	11th to 20th	Night	9% 7% 2 6% 3 2 3 2 4 6% 56%	3778
	21st to end	Night	8% 9% 3 6% 4 4 5% 4 6% 9% 40%	4262
November	1st to 10th	Night	13% 13% 3 9% 5% 4 4 3 6% 6% 34%	2537
	11th to 20th	Night	8% 15% 4 10% 5% 5% 4 4 6% 7% 32%	2800
	21st to end	Night	6% 14% 6% 10% 7% 5% 4 4 5% 6% 33%	2800
December	1st to 10th	Night	6% 12% 4 10% 5% 4 3 4 5% 6% 42%	4570
	11th to 20th	Night	5% 18% 10% 17% 8% 6% 5% 4 6% 7% 14%	5378
	21st to end	Night	5% 23% 8% 15% 7% 5% 4 3 5% 6% 18%	7458

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% 8% 7% 13% 6%	3267
	11th to 20th	Day	57% 6% 14% 11% 8% 5%	3701
	21st to end	Day	53% 6% 8% 18% 12% 3	4510
February	1st to 10th	Day	66% 7% 11% 12% 4	1800
	11th to 20th	Day	63% 7% 12% 12% 4 2	1764
	21st to end	Day	68% 6% 7% 12% 4 3	1605
March	1st to 10th	Day	50% 5% 16% 15% 9% 4	4782
	11th to 20th	Day	49% 5% 16% 22% 8%	5000
	21st to end	Day	64% 7% 15% 12% 2	5486
April	1st to 10th	Day	56% 7% 13% 16% 8%	2292
	11th to 20th	Day	50% 6% 14% 21% 8% 2	2570
	21st to end	Day	53% 7% 13% 22% 5% 1	2600
May	1st to 10th	Day	40% 7% 10% 29% 13% 2	5880
	11th to 20th	Day	42% 9% 12% 23% 10% 3	6045
	21st to end	Day	39% 8% 13% 30% 10%	6926
June	1st to 10th	Day	44% 9% 15% 25% 6%	2968
	11th to 20th	Day	41% 8% 10% 20% 17% 4	3000
	21st to end	Day	23% 7% 10% 27% 26% 7%	3000
July	1st to 10th	Day	17% 5% 8% 22% 30% 18%	6706
	11th to 20th	Day	16% 6% 7% 23% 29% 21%	6500
	21st to end	Day	16% 5% 5% 19% 38% 16%	6226
August	1st to 10th	Day	27% 6% 8% 23% 27% 10%	4208
	11th to 20th	Day	17% 5% 8% 28% 35% 8%	4197
	21st to end	Day	21% 6% 7% 22% 32% 13%	4663
September	1st to 10th	Day	22% 5% 7% 24% 33% 9%	2366
	11th to 20th	Day	31% 6% 10% 25% 23% 7%	2179
	21st to end	Day	27% 5% 13% 31% 20% 5%	2090
October	1st to 10th	Day	28% 4 7% 26% 33% 2	3251
	11th to 20th	Day	30% 3 13% 33% 17% 3	3150
	21st to end	Day	43% 6% 17% 25% 7% 1	3291
November	1st to 10th	Day	52% 7% 13% 20% 8% 1	1739
	11th to 20th	Day	51% 9% 18% 16% 4 2	1600
	21st to end	Day	52% 8% 15% 15% 8% 1	1600
December	1st to 10th	Day	43% 7% 21% 23% 5% 2	2620
	11th to 20th	Day	71% 6% 12% 10% 2	2809
	21st to end	Day	63% 6% 9% 11% 8% 3	3498
January	1st to 10th	Night	61% 8% 8% 15% 7%	6720
	11th to 20th	Night	59% 5% 12% 11% 7% 5%	6259
	21st to end	Night	50% 7% 10% 19% 10% 3	6468
February	1st to 10th	Night	63% 6% 11% 13% 6% 1	2600
	11th to 20th	Night	62% 6% 11% 13% 6% 1	2533
	21st to end	Night	64% 6% 10% 11% 7% 2	2020
March	1st to 10th	Night	52% 5% 13% 15% 10% 5%	5099
	11th to 20th	Night	41% 6% 18% 26% 8%	5000
	21st to end	Night	50% 8% 17% 21% 4	5489
April	1st to 10th	Night	51% 6% 15% 17% 9% 1	2105
	11th to 20th	Night	39% 6% 16% 28% 9% 1	1781
	21st to end	Night	43% 6% 15% 28% 8%	1800
May	1st to 10th	Night	34% 9% 11% 32% 13% 1	4097
	11th to 20th	Night	42% 10% 14% 26% 8% 2	3860
	21st to end	Night	38% 9% 15% 29% 9% 1	3972
June	1st to 10th	Night	38% 9% 15% 28% 9%	1429
	11th to 20th	Night	37% 8% 11% 24% 16% 4	1400
	21st to end	Night	20% 6% 11% 27% 27% 10%	1400
July	1st to 10th	Night	17% 5% 7% 24% 30% 17%	3145
	11th to 20th	Night	17% 5% 7% 24% 28% 19%	3319
	21st to end	Night	18% 6% 7% 22% 35% 13%	4331
August	1st to 10th	Night	24% 6% 8% 24% 26% 12%	2928
	11th to 20th	Night	20% 5% 8% 28% 29% 9%	2928
	21st to end	Night	20% 4 7% 23% 33% 12%	3245
September	1st to 10th	Night	24% 4 7% 24% 29% 12%	2030
	11th to 20th	Night	28% 6% 12% 25% 22% 7%	2178
	21st to end	Night	27% 5% 10% 30% 23% 5%	2090
October	1st to 10th	Night	22% 4 9% 28% 34% 4	3707
	11th to 20th	Night	31% 3 15% 31% 15% 4	3778
	21st to end	Night	39% 7% 15% 27% 12% 1	4262
November	1st to 10th	Night	49% 7% 15% 19% 8% 1	2537
	11th to 20th	Night	51% 6% 17% 18% 6% 2	2800
	21st to end	Night	50% 6% 17% 16% 10% 2	2800
December	1st to 10th	Night	43% 7% 23% 20% 6% 1	4570
	11th to 20th	Night	67% 7% 13% 10% 2 1	5379
	21st to end	Night	63% 7% 10% 11% 6% 3	7458

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	20% 22% 24% 28% 7% 2	200
	11th to 20th	Day	17% 16% 35% 20% 9% 3	212
	21st to end	Day	18% 13% 37% 25% 7% 1	330
February	1st to 10th	Day	27% 21% 34% 15% 3	300
	11th to 20th	Day	20% 21% 28% 23% 7% 1	300
	21st to end	Day	21% 25% 32% 18% 4 1	369
March	1st to 10th	Day	22% 23% 35% 15% 4 1	500
	11th to 20th	Day	22% 22% 30% 18% 7%	500
	21st to end	Day	26% 22% 32% 15% 4	550
April	1st to 10th	Day	26% 21% 33% 14% 6% 1	500
	11th to 20th	Day	25% 26% 29% 16% 4	492
	21st to end	Day	23% 20% 30% 17% 8% 2	500
May	1st to 10th	Day	18% 16% 31% 24% 10% 2	503
	11th to 20th	Day	19% 17% 29% 23% 10% 2	611
	21st to end	Day	21% 13% 23% 25% 15% 2	789
June	1st to 10th	Day	17% 14% 22% 29% 15% 3	730
	11th to 20th	Day	21% 20% 29% 21% 9% 1	730
	21st to end	Day	8% 17% 28% 31% 15% 2	730
July	1st to 10th	Day	6% 14% 28% 35% 17% 2	721
	11th to 20th	Day	5% 11% 38% 33% 12% 1	636
	21st to end	Day	5% 13% 36% 30% 13% 3	575
August	1st to 10th	Day	9% 10% 33% 30% 15% 2	527
	11th to 20th	Day	6% 11% 30% 35% 15% 4	517
	21st to end	Day	7% 15% 32% 28% 13% 4	583
September	1st to 10th	Day	8% 11% 34% 28% 17% 3	530
	11th to 20th	Day	16% 14% 33% 21% 15% 2	523
	21st to end	Day	15% 15% 31% 23% 12% 3	490
October	1st to 10th	Day	15% 14% 31% 21% 15% 4	355
	11th to 20th	Day	18% 16% 25% 20% 15% 7%	300
	21st to end	Day	21% 18% 31% 24% 6% 1	330
November	1st to 10th	Day	22% 14% 30% 21% 10% 3	300
	11th to 20th	Day	20% 17% 33% 25% 5% 1	300
	21st to end	Day	14% 14% 35% 28% 9%	300
December	1st to 10th	Day	16% 12% 34% 25% 11% 1	300
	11th to 20th	Day	19% 18% 37% 20% 4 2	250
	21st to end	Day	24% 16% 32% 19% 9%	220
January	1st to 10th	Night	19% 11% 26% 33% 10% 1	980
	11th to 20th	Night	18% 9% 30% 31% 12% 1	800
	21st to end	Night	13% 8% 32% 36% 10% 1	880
February	1st to 10th	Night	18% 10% 33% 31% 7%	800
	11th to 20th	Night	18% 10% 31% 32% 8% 1	784
	21st to end	Night	16% 10% 33% 32% 8% 1	660
March	1st to 10th	Night	17% 10% 29% 33% 10% 1	800
	11th to 20th	Night	15% 9% 26% 37% 13% 1	800
	21st to end	Night	18% 9% 26% 35% 11% 1	880
April	1st to 10th	Night	15% 13% 27% 33% 11% 1	715
	11th to 20th	Night	14% 13% 30% 34% 9% 1	593
	21st to end	Night	18% 8% 27% 33% 13% 1	600
May	1st to 10th	Night	14% 10% 25% 34% 17% 1	600
	11th to 20th	Night	15% 10% 22% 32% 20% 2	591
	21st to end	Night	18% 8% 22% 31% 19% 1	650
June	1st to 10th	Night	14% 6% 18% 38% 23% 1	429
	11th to 20th	Night	15% 7% 26% 37% 15%	400
	21st to end	Night	5% 2 17% 51% 23% 2	400
July	1st to 10th	Night	4 1 14% 49% 30% 2	390
	11th to 20th	Night	3 2 16% 55% 24% 1	388
	21st to end	Night	3 4 19% 46% 26% 2	643
August	1st to 10th	Night	8% 3 15% 46% 27% 1	597
	11th to 20th	Night	3 3 15% 49% 28% 2	594
	21st to end	Night	8% 5% 18% 42% 26% 2	660
September	1st to 10th	Night	8% 3 16% 42% 29% 2	645
	11th to 20th	Night	10% 3 16% 41% 27% 4	792
	21st to end	Night	12% 5% 19% 38% 24% 3	760
October	1st to 10th	Night	14% 4 20% 41% 20% 1	760
	11th to 20th	Night	15% 7% 18% 39% 18% 3	760
	21st to end	Night	16% 8% 25% 36% 12% 3	836
November	1st to 10th	Night	21% 6% 21% 39% 12%	782
	11th to 20th	Night	18% 13% 29% 33% 7% 1	1000
	21st to end	Night	13% 10% 33% 34% 9% 1	1000
December	1st to 10th	Night	20% 9% 31% 33% 7% 1	1000
	11th to 20th	Night	19% 11% 28% 34% 7% 1	1000
	21st to end	Night	20% 11% 33% 28% 8%	1100

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