River Valley RV Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the River Valley RV Park clear sky chart from 2005-11-06 to 2025-03-12.

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	13% 10% 4 9% 6% 5% 5% 4 5% 7% 33%	108090
	Night	13% 11% 4 9% 5% 5% 4 4 5% 7% 32%	111014
Transparency	Day	49% 7% 12% 20% 12% 1	111661
	Night	50% 6% 12% 20% 11% 1	115584
Seeing	Day	20% 15% 31% 20% 10% 3	15997
	Night	20% 13% 31% 26% 10% 1	26009

By Month

Percentage Cloud Cover SE (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	11% 15% 7% 17% 7% 7% 5% 3 5% 5% 17%	3617
	11th to 20th	Day	12% 14% 7% 19% 12% 10% 7% 4 4 4 9%	3620
	21st to end	Day	15% 17% 8% 12% 6% 5% 5% 4 4 5% 19%	3982
February	1st to 10th	Day	11% 14% 5% 12% 9% 8% 5% 4 4 7% 21%	1800
	11th to 20th	Day	11% 14% 6% 13% 9% 8% 5% 3 5% 6% 21%	1924
	21st to end	Day	12% 15% 6% 12% 8% 4 4 4 5% 6% 24%	1650
March	1st to 10th	Day	13% 13% 4 9% 6% 5% 4 3 4 7% 31%	3220
	11th to 20th	Day	12% 10% 5% 10% 6% 5% 4 4 5% 6% 32%	3457
	21st to end	Day	18% 12% 5% 8% 6% 5% 4 3 5% 4 29%	3865
April	1st to 10th	Day	17% 14% 4 9% 4 4 3 3 4 7% 30%	2280
	11th to 20th	Day	18% 12% 2 6% 5% 5% 4 3 4 5% 36%	2371
	21st to end	Day	15% 9% 3 8% 6% 5% 5% 3 5% 6% 34%	2470
May	1st to 10th	Day	14% 8% 3 7% 5% 5% 5% 4 7% 7% 35%	4082
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 7% 8% 40%	4081
	21st to end	Day	9% 7% 3 6% 4 4 4 4 6% 9% 45%	4792
June	1st to 10th	Day	12% 6% 2 6% 5% 4 5% 4 6% 8% 41%	2707
	11th to 20th	Day	12% 5% 2 7% 4 4 4 5% 7% 8% 42%	2850
	21st to end	Day	10% 6% 3 7% 5% 5% 5% 5% 6% 8% 40%	2681
July	1st to 10th	Day	11% 7% 3 7% 6% 6% 5% 5% 6% 8% 36%	4440
	11th to 20th	Day	5% 5% 2 6% 5% 4 5% 4 7% 10% 47%	4440
	21st to end	Day	6% 4 2 6% 5% 5% 6% 6% 7% 9% 42%	4813
August	1st to 10th	Day	10% 5% 2 6% 6% 6% 6% 5% 6% 8% 40%	4109
	11th to 20th	Day	12% 5% 3 5% 4 4 5% 4 6% 8% 45%	4044
	21st to end	Day	10% 6% 3 6% 4 5% 5% 5% 6% 8% 42%	4387
September	1st to 10th	Day	10% 6% 2 6% 5% 5% 6% 4 5% 9% 42%	2214
	11th to 20th	Day	12% 5% 2 6% 4 4 4 4 6% 8% 46%	2090
	21st to end	Day	13% 7% 3 7% 5% 4 5% 4 5% 9% 38%	2090
October	1st to 10th	Day	15% 7% 3 8% 5% 4 4 3 4 6% 42%	2081
	11th to 20th	Day	20% 10% 4 9% 5% 5% 5% 3 5% 7% 27%	1848
	21st to end	Day	20% 12% 4 9% 6% 5% 4 3 6% 7% 23%	1881
November	1st to 10th	Day	14% 12% 3 9% 4 5% 4 3 6% 7% 34%	1762
	11th to 20th	Day	14% 15% 6% 10% 6% 5% 4 4 5% 7% 23%	1800
	21st to end	Day	19% 18% 5% 11% 7% 5% 4 3 3 4 21%	1720
December	1st to 10th	Day	14% 17% 6% 14% 7% 6% 6% 4 6% 6% 15%	2381
	11th to 20th	Day	17% 19% 8% 11% 7% 5% 5% 4 4 4 17%	2625
	21st to end	Day	26% 23% 7% 11% 5% 4 4 3 3 3 11%	3916
January	1st to 10th	Night	11% 12% 6% 16% 7% 6% 5% 3 5% 6% 23%	6348
	11th to 20th	Night	12% 15% 6% 19% 9% 11% 5% 4 5% 5% 11%	6360
	21st to end	Night	13% 18% 7% 14% 6% 4 6% 4 5% 6% 16%	6982
February	1st to 10th	Night	12% 13% 5% 12% 8% 6% 5% 5% 5% 6% 23%	2600
	11th to 20th	Night	13% 14% 5% 10% 6% 6% 6% 4 5% 6% 26%	2358
	21st to end	Night	15% 13% 4 12% 7% 5% 5% 4 4 6% 26%	1980
March	1st to 10th	Night	15% 9% 4 7% 4 4 4 3 5% 6% 39%	3853
	11th to 20th	Night	10% 8% 3 7% 5% 4 4 4 6% 8% 41%	3532
	21st to end	Night	14% 12% 4 9% 5% 5% 4 4 5% 6% 33%	3796
April	1st to 10th	Night	16% 12% 3 7% 4 5% 4 4 4 7% 35%	1900
	11th to 20th	Night	19% 8% 3 6% 4 3 4 3 5% 7% 38%	1756
	21st to end	Night	17% 9% 3 6% 4 4 4 4 6% 7% 37%	1710
May	1st to 10th	Night	13% 7% 3 6% 5% 5% 4 4 5% 8% 41%	2813
	11th to 20th	Night	13% 7% 2 6% 4 4 4 4 5% 8% 42%	2812
	21st to end	Night	14% 6% 2 5% 4 4 4 3 5% 7% 46%	2758
June	1st to 10th	Night	13% 6% 1 5% 4 4 4 4 6% 8% 45%	1463
	11th to 20th	Night	10% 6% 2 5% 5% 4 4 4 7% 9% 44%	1330
	21st to end	Night	8% 6% 2 5% 4 4 4 5% 6% 8% 47%	1487
July	1st to 10th	Night	9% 6% 2 7% 4 4 5% 5% 6% 8% 42%	2530
	11th to 20th	Night	5% 4 2 5% 4 3 4 4 5% 7% 58%	2530
	21st to end	Night	7% 5% 2 5% 4 4 5% 4 6% 8% 50%	2750
August	1st to 10th	Night	9% 5% 2 5% 4 4 4 4 6% 9% 48%	2820
	11th to 20th	Night	11% 4 1 5% 3 3 4 3 6% 7% 51%	2785
	21st to end	Night	9% 5% 2 5% 4 4 5% 3 5% 8% 49%	3252
September	1st to 10th	Night	8% 5% 2 6% 4 4 5% 3 6% 7% 51%	1946
	11th to 20th	Night	10% 4 1 5% 3 3 3 3 6% 7% 55%	2090
	21st to end	Night	13% 6% 3 6% 4 5% 5% 4 6% 8% 42%	2090
October	1st to 10th	Night	17% 6% 2 5% 3 3 4 3 5% 6% 45%	2099
	11th to 20th	Night	17% 11% 2 9% 5% 4 3 3 4 5% 35%	2329
	21st to end	Night	22% 10% 3 7% 4 4 4 4 5% 7% 30%	2717
November	1st to 10th	Night	12% 10% 3 7% 5% 4 4 3 6% 7% 39%	2536
	11th to 20th	Night	14% 12% 4 10% 6% 5% 5% 4 6% 6% 27%	2600
	21st to end	Night	17% 16% 5% 10% 6% 5% 4 4 5% 6% 22%	2676
December	1st to 10th	Night	12% 15% 5% 12% 7% 6% 5% 4 6% 7% 21%	4802
	11th to 20th	Night	14% 20% 6% 12% 7% 5% 4 4 5% 6% 18%	5582
	21st to end	Night	26% 22% 5% 10% 5% 3 3 2 4 4 16%	7042

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	67% 6% 11% 12% 3	3618
	11th to 20th	Day	78% 6% 5% 7% 4	3620
	21st to end	Day	67% 5% 12% 9% 5% 1	3982
February	1st to 10th	Day	62% 7% 9% 16% 6%	1800
	11th to 20th	Day	64% 6% 9% 13% 7% 1	1934
	21st to end	Day	61% 6% 11% 16% 6% 1	1650
March	1st to 10th	Day	52% 6% 11% 20% 9% 1	3220
	11th to 20th	Day	51% 6% 14% 18% 9% 2	3457
	21st to end	Day	57% 6% 9% 15% 12% 1	3865
April	1st to 10th	Day	56% 5% 10% 17% 12%	2280
	11th to 20th	Day	50% 5% 10% 19% 15% 2	2371
	21st to end	Day	50% 6% 12% 15% 15% 2	2470
May	1st to 10th	Day	44% 8% 12% 17% 17% 2	4120
	11th to 20th	Day	39% 8% 14% 25% 13% 1	4085
	21st to end	Day	35% 7% 12% 22% 21% 2	4805
June	1st to 10th	Day	39% 7% 13% 25% 15% 1	2707
	11th to 20th	Day	38% 7% 12% 24% 18% 1	2850
	21st to end	Day	40% 8% 12% 24% 14% 1	2681
July	1st to 10th	Day	44% 7% 13% 20% 15% 2	4371
	11th to 20th	Day	29% 7% 14% 32% 16% 1	4365
	21st to end	Day	34% 9% 13% 22% 20% 1	4662
August	1st to 10th	Day	40% 7% 10% 26% 15% 2	4095
	11th to 20th	Day	36% 7% 13% 30% 14% 1	4083
	21st to end	Day	38% 7% 14% 26% 14% 1	4386
September	1st to 10th	Day	39% 8% 13% 26% 13% 2	2214
	11th to 20th	Day	35% 7% 14% 28% 15% 1	2090
	21st to end	Day	43% 7% 14% 25% 11%	2090
October	1st to 10th	Day	32% 4 9% 33% 18% 4	3458
	11th to 20th	Day	43% 6% 10% 28% 12%	3051
	21st to end	Day	56% 5% 12% 19% 7%	3081
November	1st to 10th	Day	49% 7% 13% 21% 10%	1762
	11th to 20th	Day	60% 7% 13% 14% 6% 1	1800
	21st to end	Day	66% 7% 11% 11% 4	1720
December	1st to 10th	Day	69% 7% 13% 9% 1	2381
	11th to 20th	Day	70% 5% 9% 12% 3	2621
	21st to end	Day	78% 4 6% 7% 4	3916
January	1st to 10th	Night	60% 6% 9% 15% 8% 2	6348
	11th to 20th	Night	74% 7% 8% 7% 4 1	6360
	21st to end	Night	65% 8% 10% 11% 6%	6982
February	1st to 10th	Night	60% 7% 9% 16% 8% 1	2600
	11th to 20th	Night	57% 6% 11% 18% 7% 1	2359
	21st to end	Night	59% 5% 12% 16% 8% 1	1980
March	1st to 10th	Night	46% 6% 15% 24% 9% 1	3853
	11th to 20th	Night	39% 6% 16% 24% 13% 1	3532
	21st to end	Night	50% 7% 13% 20% 9% 1	3796
April	1st to 10th	Night	49% 5% 10% 21% 14% 2	1900
	11th to 20th	Night	46% 4 10% 20% 17% 2	1756
	21st to end	Night	44% 6% 11% 21% 14% 3	1710
May	1st to 10th	Night	40% 7% 13% 19% 17% 3	2840
	11th to 20th	Night	39% 7% 10% 29% 13% 2	2813
	21st to end	Night	37% 7% 12% 22% 18% 4	2766
June	1st to 10th	Night	37% 7% 10% 26% 18% 2	1463
	11th to 20th	Night	35% 8% 13% 22% 21% 2	1330
	21st to end	Night	34% 8% 12% 27% 17% 2	1487
July	1st to 10th	Night	38% 6% 12% 25% 13% 6%	2490
	11th to 20th	Night	26% 5% 13% 37% 19% 1	2482
	21st to end	Night	32% 8% 17% 23% 19% 2	2662
August	1st to 10th	Night	32% 6% 16% 30% 15% 1	2810
	11th to 20th	Night	31% 6% 15% 32% 15% 1	2812
	21st to end	Night	32% 6% 13% 30% 18% 1	3252
September	1st to 10th	Night	32% 7% 12% 29% 18% 1	1946
	11th to 20th	Night	29% 6% 13% 37% 16% 1	2090
	21st to end	Night	39% 7% 14% 29% 10% 1	2090
October	1st to 10th	Night	29% 5% 11% 35% 20% 1	3502
	11th to 20th	Night	43% 5% 12% 25% 15% 1	3865
	21st to end	Night	47% 5% 11% 28% 9%	4467
November	1st to 10th	Night	44% 6% 14% 23% 12% 1	2536
	11th to 20th	Night	55% 8% 13% 17% 8% 1	2600
	21st to end	Night	61% 8% 14% 13% 4	2676
December	1st to 10th	Night	61% 7% 16% 12% 4	4802
	11th to 20th	Night	65% 5% 10% 11% 7% 1	5585
	21st to end	Night	73% 4 8% 7% 8%	7042

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	24% 20% 39% 11% 5%	300
	11th to 20th	Day	27% 21% 40% 9% 3	300
	21st to end	Day	28% 17% 36% 14% 5%	330
February	1st to 10th	Day	25% 29% 32% 10% 2 1	300
	11th to 20th	Day	26% 28% 36% 8% 2	300
	21st to end	Day	35% 30% 29% 4 1	249
March	1st to 10th	Day	28% 29% 35% 8% 1	300
	11th to 20th	Day	25% 20% 32% 17% 6%	443
	21st to end	Day	29% 17% 32% 16% 4 1	506
April	1st to 10th	Day	28% 18% 32% 15% 6% 1	460
	11th to 20th	Day	34% 17% 26% 14% 7% 2	452
	21st to end	Day	25% 17% 29% 21% 7% 2	460
May	1st to 10th	Day	25% 17% 34% 16% 6% 3	463
	11th to 20th	Day	19% 13% 31% 23% 8% 5%	487
	21st to end	Day	15% 14% 31% 25% 12% 3	715
June	1st to 10th	Day	14% 15% 33% 28% 8% 3	680
	11th to 20th	Day	14% 14% 38% 22% 9% 3	680
	21st to end	Day	14% 15% 34% 24% 11% 3	680
July	1st to 10th	Day	8% 7% 31% 30% 17% 7%	671
	11th to 20th	Day	8% 11% 30% 29% 15% 6%	668
	21st to end	Day	9% 8% 33% 27% 17% 6%	739
August	1st to 10th	Day	9% 7% 26% 28% 19% 11%	491
	11th to 20th	Day	10% 6% 21% 34% 17% 12%	479
	21st to end	Day	15% 10% 22% 30% 17% 6%	539
September	1st to 10th	Day	13% 11% 30% 23% 14% 9%	490
	11th to 20th	Day	13% 8% 23% 27% 22% 7%	490
	21st to end	Day	20% 11% 23% 25% 15% 6%	490
October	1st to 10th	Day	22% 14% 28% 21% 13% 2	490
	11th to 20th	Day	27% 14% 34% 20% 5% 1	438
	21st to end	Day	29% 20% 34% 12% 3 1	330
November	1st to 10th	Day	28% 19% 35% 13% 5%	300
	11th to 20th	Day	27% 24% 35% 11% 3 1	300
	21st to end	Day	27% 27% 32% 11% 3	260
December	1st to 10th	Day	29% 24% 29% 13% 5% 1	200
	11th to 20th	Day	32% 22% 36% 10% 2	200
	21st to end	Day	35% 24% 29% 8% 4 1	317
January	1st to 10th	Night	23% 18% 34% 19% 5% 1	1000
	11th to 20th	Night	24% 18% 33% 19% 5% 1	1000
	21st to end	Night	20% 13% 37% 24% 6%	1099
February	1st to 10th	Night	20% 18% 35% 23% 4	800
	11th to 20th	Night	23% 20% 33% 20% 4	783
	21st to end	Night	25% 20% 36% 17% 3	660
March	1st to 10th	Night	20% 16% 35% 22% 7%	800
	11th to 20th	Night	19% 20% 33% 22% 6%	767
	21st to end	Night	21% 16% 34% 23% 5% 1	827
April	1st to 10th	Night	21% 14% 37% 22% 6% 1	570
	11th to 20th	Night	23% 15% 31% 24% 6% 1	563
	21st to end	Night	22% 12% 31% 27% 7% 1	570
May	1st to 10th	Night	14% 11% 37% 30% 7% 1	570
	11th to 20th	Night	18% 9% 28% 33% 12% 1	561
	21st to end	Night	16% 8% 28% 30% 17% 1	617
June	1st to 10th	Night	14% 9% 29% 34% 13% 1	513
	11th to 20th	Night	13% 7% 31% 35% 13% 1	380
	21st to end	Night	11% 6% 29% 38% 15% 1	537
July	1st to 10th	Night	9% 3 22% 41% 22% 3	555
	11th to 20th	Night	8% 3 23% 41% 23% 3	552
	21st to end	Night	9% 4 26% 39% 21% 1	624
August	1st to 10th	Night	8% 2 24% 40% 26% 1	567
	11th to 20th	Night	9% 4 20% 38% 26% 3	564
	21st to end	Night	12% 4 22% 37% 22% 2	627
September	1st to 10th	Night	10% 6% 28% 30% 22% 4	616
	11th to 20th	Night	12% 4 23% 33% 23% 4	760
	21st to end	Night	17% 9% 25% 28% 18% 3	760
October	1st to 10th	Night	20% 9% 27% 28% 15% 1	760
	11th to 20th	Night	23% 14% 32% 23% 7% 1	760
	21st to end	Night	29% 14% 30% 21% 5% 1	836
November	1st to 10th	Night	21% 14% 34% 22% 9% 1	780
	11th to 20th	Night	23% 18% 33% 21% 5% 1	800
	21st to end	Night	26% 16% 34% 20% 5%	800
December	1st to 10th	Night	25% 17% 32% 22% 4	931
	11th to 20th	Night	26% 18% 35% 17% 4 1	1000
	21st to end	Night	32% 14% 32% 20% 2	1100

Page generated at 2025-03-09 08:08:45. Version ac07

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