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 2005-11-05 to 2024-10-14.

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 8% 6% 5% 5% 4 5% 7% 34%	100776
	Night	14% 11% 4 8% 5% 5% 4 4 5% 7% 34%	97769
Transparency	Day	48% 7% 12% 20% 12% 1	100568
	Night	49% 6% 12% 20% 11% 1	97654
Seeing	Day	20% 15% 31% 21% 10% 4	15571
	Night	20% 12% 31% 26% 10% 1	25355

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	13% 19% 9% 13% 6% 7% 5% 3 4 4 18%	2527
	11th to 20th	Day	14% 17% 7% 17% 13% 10% 6% 3 3 4 7%	2530
	21st to end	Day	20% 21% 9% 10% 6% 5% 4 3 4 5% 13%	2783
February	1st to 10th	Day	11% 14% 5% 12% 10% 8% 5% 4 4 6% 21%	1710
	11th to 20th	Day	11% 14% 6% 13% 8% 7% 5% 3 5% 6% 22%	1825
	21st to end	Day	12% 15% 6% 12% 7% 4 4 4 5% 6% 24%	1570
March	1st to 10th	Day	13% 13% 4 9% 6% 5% 4 3 4 6% 31%	3120
	11th to 20th	Day	12% 10% 5% 10% 6% 6% 4 4 5% 6% 32%	3447
	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	21% 10% 4 10% 5% 5% 5% 3 6% 6% 25%	1781
	21st to end	Day	21% 12% 4 9% 6% 5% 4 3 6% 7% 23%	1782
November	1st to 10th	Day	13% 11% 3 9% 4 5% 5% 3 6% 7% 33%	1672
	11th to 20th	Day	13% 15% 6% 10% 6% 5% 5% 4 5% 7% 24%	1710
	21st to end	Day	20% 18% 5% 11% 7% 4 4 3 3 4 22%	1634
December	1st to 10th	Day	16% 15% 6% 15% 6% 5% 5% 3 5% 6% 18%	1392
	11th to 20th	Day	15% 17% 5% 11% 6% 5% 5% 5% 5% 6% 20%	1675
	21st to end	Day	25% 22% 7% 11% 6% 5% 4 3 4 4 10%	2731
January	1st to 10th	Night	16% 16% 7% 12% 6% 5% 4 3 5% 5% 21%	4428
	11th to 20th	Night	13% 15% 6% 16% 10% 11% 5% 3 4 4 12%	4440
	21st to end	Night	18% 20% 7% 13% 6% 4 5% 4 5% 5% 13%	4884
February	1st to 10th	Night	12% 13% 5% 12% 8% 6% 5% 5% 5% 6% 23%	2470
	11th to 20th	Night	12% 13% 5% 10% 6% 6% 5% 4 5% 6% 26%	2237
	21st to end	Night	15% 13% 4 11% 7% 5% 5% 4 4 5% 26%	1884
March	1st to 10th	Night	15% 9% 4 7% 4 4 4 3 5% 6% 39%	3733
	11th to 20th	Night	10% 8% 3 7% 5% 4 4 4 6% 8% 41%	3513
	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	18% 11% 2 9% 6% 4 4 3 4 5% 34%	2249
	21st to end	Night	23% 11% 3 7% 4 4 4 4 5% 7% 29%	2574
November	1st to 10th	Night	11% 10% 3 7% 5% 4 5% 3 6% 7% 39%	2406
	11th to 20th	Night	14% 12% 4 9% 6% 5% 5% 4 6% 7% 27%	2470
	21st to end	Night	17% 16% 5% 9% 6% 5% 4 4 5% 6% 23%	2542
December	1st to 10th	Night	15% 17% 6% 12% 7% 6% 5% 4 5% 5% 20%	2784
	11th to 20th	Night	14% 15% 5% 12% 7% 6% 5% 4 6% 7% 19%	3522
	21st to end	Night	27% 22% 5% 11% 5% 4 3 2 4 4 13%	4916

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	68% 8% 12% 8% 3	2528
	11th to 20th	Day	81% 6% 6% 5% 1	2530
	21st to end	Day	74% 6% 11% 6% 3	2783
February	1st to 10th	Day	62% 7% 9% 16% 5%	1710
	11th to 20th	Day	63% 6% 9% 14% 8% 1	1835
	21st to end	Day	61% 6% 11% 16% 6% 1	1570
March	1st to 10th	Day	53% 6% 11% 20% 9% 1	3120
	11th to 20th	Day	51% 6% 14% 18% 9% 2	3447
	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	44% 6% 10% 26% 12% 1	2081
	11th to 20th	Day	58% 7% 12% 17% 6%	1782
	21st to end	Day	60% 7% 13% 14% 6%	1782
November	1st to 10th	Day	49% 8% 13% 20% 10%	1672
	11th to 20th	Day	59% 7% 14% 14% 6% 1	1710
	21st to end	Day	66% 7% 12% 11% 5%	1634
December	1st to 10th	Day	68% 6% 10% 13% 2	1392
	11th to 20th	Day	64% 7% 13% 13% 3	1671
	21st to end	Day	79% 5% 8% 5% 3	2731
January	1st to 10th	Night	64% 6% 10% 13% 6% 1	4428
	11th to 20th	Night	75% 6% 8% 8% 3	4440
	21st to end	Night	70% 9% 10% 7% 3	4884
February	1st to 10th	Night	60% 7% 9% 16% 7% 1	2470
	11th to 20th	Night	57% 6% 11% 17% 7% 1	2238
	21st to end	Night	59% 5% 11% 15% 8% 1	1884
March	1st to 10th	Night	46% 6% 15% 24% 8% 1	3733
	11th to 20th	Night	39% 6% 16% 24% 13% 1	3513
	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	38% 7% 12% 27% 15% 1	2099
	11th to 20th	Night	52% 5% 12% 22% 7% 1	2253
	21st to end	Night	55% 6% 12% 18% 8%	2574
November	1st to 10th	Night	43% 7% 14% 23% 12% 1	2406
	11th to 20th	Night	54% 8% 14% 17% 7% 1	2470
	21st to end	Night	61% 7% 14% 14% 4	2542
December	1st to 10th	Night	66% 6% 10% 13% 5%	2784
	11th to 20th	Night	63% 7% 14% 10% 6% 1	3525
	21st to end	Night	76% 5% 8% 7% 3	4916

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	26% 20% 38% 11% 5%	270
	11th to 20th	Day	28% 20% 40% 9% 4	270
	21st to end	Day	29% 15% 36% 14% 5%	297
February	1st to 10th	Day	24% 28% 33% 11% 2 1	270
	11th to 20th	Day	25% 29% 37% 8% 2	270
	21st to end	Day	36% 30% 29% 4 1	225
March	1st to 10th	Day	27% 30% 34% 8% 1	270
	11th to 20th	Day	25% 20% 32% 17% 6%	440
	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	29% 14% 35% 18% 4	413
	21st to end	Day	31% 21% 33% 11% 4 1	297
November	1st to 10th	Day	26% 19% 36% 14% 5%	270
	11th to 20th	Day	25% 26% 35% 11% 3 1	270
	21st to end	Day	26% 27% 33% 10% 3	234
December	1st to 10th	Day	29% 25% 30% 10% 5% 1	180
	11th to 20th	Day	32% 22% 37% 9% 1	180
	21st to end	Day	33% 27% 29% 8% 2	285
January	1st to 10th	Night	24% 19% 33% 19% 5% 1	950
	11th to 20th	Night	25% 18% 32% 19% 5% 1	950
	21st to end	Night	20% 12% 36% 25% 6%	1045
February	1st to 10th	Night	20% 18% 35% 23% 4	760
	11th to 20th	Night	22% 19% 34% 20% 4	743
	21st to end	Night	26% 20% 35% 17% 3	628
March	1st to 10th	Night	19% 16% 35% 23% 7%	760
	11th to 20th	Night	19% 20% 33% 22% 6%	760
	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% 15% 31% 23% 7% 1	735
	21st to end	Night	30% 14% 30% 20% 5% 1	792
November	1st to 10th	Night	20% 14% 34% 22% 10% 1	740
	11th to 20th	Night	23% 18% 33% 20% 5% 1	760
	21st to end	Night	26% 16% 33% 21% 5%	760
December	1st to 10th	Night	26% 17% 32% 21% 4	884
	11th to 20th	Night	25% 18% 35% 17% 4 1	950
	21st to end	Night	32% 15% 32% 19% 2	1045

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