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 2026-07-16.

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% 34%	137032
	Night	13% 11% 4 9% 5% 5% 4 4 5% 7% 33%	135837
Transparency	Day	48% 6% 11% 21% 13% 1	140558
	Night	49% 6% 12% 20% 12% 1	140388
Seeing	Day	20% 15% 31% 21% 10% 3	17918
	Night	19% 13% 31% 26% 10% 1	27733

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% 16% 8% 16% 7% 7% 5% 3 4 5% 16%	4691
	11th to 20th	Day	11% 15% 8% 19% 12% 9% 6% 3 3 3 11%	4710
	21st to end	Day	12% 16% 7% 11% 8% 6% 5% 4 5% 6% 20%	5156
February	1st to 10th	Day	12% 14% 5% 11% 9% 7% 6% 4 4 7% 21%	1890
	11th to 20th	Day	11% 13% 5% 13% 8% 8% 5% 3 5% 6% 22%	2023
	21st to end	Day	11% 16% 6% 13% 7% 4 5% 4 5% 6% 24%	1730
March	1st to 10th	Day	12% 10% 3 10% 6% 5% 4 3 5% 7% 35%	4580
	11th to 20th	Day	12% 10% 5% 9% 6% 5% 4 4 6% 8% 32%	5042
	21st to end	Day	21% 12% 5% 8% 5% 4 4 3 5% 5% 28%	5663
April	1st to 10th	Day	17% 14% 4 9% 5% 4 3 3 4 7% 29%	2520
	11th to 20th	Day	17% 11% 3 6% 5% 5% 4 3 4 5% 36%	2624
	21st to end	Day	15% 9% 3 8% 5% 5% 5% 3 5% 6% 34%	2730
May	1st to 10th	Day	15% 8% 3 7% 6% 5% 5% 4 6% 7% 34%	7616
	11th to 20th	Day	13% 7% 3 7% 5% 5% 5% 4 6% 7% 37%	7626
	21st to end	Day	12% 6% 2 6% 4 4 4 3 5% 7% 45%	8987
June	1st to 10th	Day	12% 6% 2 6% 5% 4 5% 4 6% 8% 43%	2992
	11th to 20th	Day	12% 5% 2 7% 5% 5% 4 5% 7% 8% 41%	3150
	21st to end	Day	10% 6% 3 7% 5% 5% 5% 5% 6% 7% 41%	2963
July	1st to 10th	Day	9% 6% 3 6% 5% 5% 5% 5% 7% 9% 39%	6500
	11th to 20th	Day	6% 5% 2 7% 5% 4 4 4 6% 9% 48%	6431
	21st to end	Day	6% 4 2 6% 5% 5% 5% 5% 7% 10% 45%	6924
August	1st to 10th	Day	9% 5% 2 6% 6% 6% 6% 5% 6% 8% 41%	4239
	11th to 20th	Day	12% 5% 3 5% 4 4 5% 4 6% 8% 45%	4174
	21st to end	Day	10% 6% 2 6% 4 5% 5% 5% 6% 8% 42%	4526
September	1st to 10th	Day	10% 6% 2 6% 5% 5% 6% 4 5% 9% 42%	2330
	11th to 20th	Day	11% 5% 2 6% 4 4 4 4 6% 8% 47%	2200
	21st to end	Day	13% 7% 3 7% 5% 4 5% 4 5% 8% 39%	2200
October	1st to 10th	Day	15% 7% 3 8% 5% 4 4 3 4 6% 43%	2190
	11th to 20th	Day	20% 9% 4 9% 5% 5% 5% 4 5% 7% 27%	1945
	21st to end	Day	19% 11% 4 8% 6% 5% 4 3 6% 7% 24%	1980
November	1st to 10th	Day	13% 12% 3 8% 4 5% 4 4 6% 7% 34%	1852
	11th to 20th	Day	14% 15% 6% 10% 6% 5% 4 4 5% 7% 23%	1890
	21st to end	Day	19% 18% 5% 11% 6% 5% 4 3 3 4 21%	1806
December	1st to 10th	Day	14% 17% 6% 15% 6% 6% 6% 4 6% 6% 14%	2454
	11th to 20th	Day	17% 19% 7% 12% 7% 5% 5% 4 4 4 17%	2695
	21st to end	Day	26% 23% 7% 11% 5% 4 4 3 3 3 12%	4003
January	1st to 10th	Night	14% 13% 6% 15% 8% 6% 5% 3 5% 5% 20%	8232
	11th to 20th	Night	10% 17% 7% 18% 9% 10% 5% 4 4 5% 11%	8280
	21st to end	Night	10% 16% 6% 14% 7% 5% 6% 5% 6% 7% 18%	9044
February	1st to 10th	Night	11% 13% 5% 12% 8% 6% 5% 5% 5% 6% 23%	2730
	11th to 20th	Night	13% 13% 5% 10% 6% 6% 6% 4 5% 7% 26%	2479
	21st to end	Night	15% 13% 5% 12% 7% 5% 5% 4 4 6% 25%	2076
March	1st to 10th	Night	15% 9% 3 8% 5% 4 4 3 6% 6% 38%	5493
	11th to 20th	Night	12% 8% 3 7% 4 4 4 4 6% 9% 38%	5138
	21st to end	Night	16% 11% 4 9% 5% 4 4 3 4 6% 34%	5553
April	1st to 10th	Night	16% 12% 3 7% 4 5% 4 4 4 7% 34%	2100
	11th to 20th	Night	18% 8% 4 7% 4 3 4 3 5% 7% 37%	1943
	21st to end	Night	16% 9% 3 6% 4 4 4 4 6% 7% 37%	1890
May	1st to 10th	Night	12% 7% 2 7% 5% 5% 4 4 6% 8% 41%	5237
	11th to 20th	Night	14% 8% 3 6% 4 4 4 3 5% 8% 41%	5234
	21st to end	Night	16% 5% 2 4 3 3 4 3 5% 6% 49%	5180
June	1st to 10th	Night	12% 6% 1 5% 4 4 5% 4 5% 7% 46%	1617
	11th to 20th	Night	10% 6% 2 5% 5% 5% 5% 4 7% 9% 43%	1470
	21st to end	Night	9% 6% 2 5% 4 4 4 5% 6% 8% 46%	1644
July	1st to 10th	Night	9% 6% 2 7% 4 4 5% 5% 6% 8% 43%	3698
	11th to 20th	Night	6% 4 2 5% 4 4 4 4 5% 8% 54%	3657
	21st to end	Night	7% 5% 2 5% 4 4 5% 4 6% 8% 50%	3947
August	1st to 10th	Night	9% 5% 2 5% 4 4 4 4 6% 9% 48%	2910
	11th to 20th	Night	11% 4 1 5% 3 3 4 3 6% 7% 51%	2875
	21st to end	Night	9% 5% 2 5% 4 4 5% 3 5% 8% 50%	3355
September	1st to 10th	Night	8% 5% 2 6% 4 4 5% 3 6% 7% 51%	2049
	11th to 20th	Night	10% 4 1 5% 3 3 3 3 6% 8% 55%	2200
	21st to end	Night	13% 6% 3 7% 4 5% 5% 4 6% 8% 42%	2200
October	1st to 10th	Night	16% 6% 2 5% 3 3 4 3 5% 7% 46%	2210
	11th to 20th	Night	17% 11% 2 8% 5% 4 3 3 4 5% 36%	2452
	21st to end	Night	21% 10% 3 7% 4 4 4 4 5% 7% 31%	2860
November	1st to 10th	Night	12% 10% 3 7% 5% 4 4 3 5% 7% 39%	2666
	11th to 20th	Night	14% 12% 4 9% 6% 5% 5% 4 6% 6% 28%	2730
	21st to end	Night	16% 16% 5% 10% 6% 5% 4 4 5% 6% 22%	2810
December	1st to 10th	Night	12% 15% 5% 12% 7% 6% 5% 4 6% 7% 21%	4949
	11th to 20th	Night	13% 20% 6% 12% 7% 5% 4 4 5% 6% 18%	5732
	21st to end	Night	25% 22% 5% 10% 5% 3 3 2 4 4 16%	7197

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	69% 6% 11% 12% 3	4692
	11th to 20th	Day	77% 5% 4 8% 4	4710
	21st to end	Day	64% 5% 11% 12% 8% 1	5156
February	1st to 10th	Day	61% 7% 9% 17% 6%	1890
	11th to 20th	Day	63% 6% 10% 13% 7% 1	2033
	21st to end	Day	61% 6% 11% 16% 6% 1	1730
March	1st to 10th	Day	49% 5% 13% 18% 11% 4	4580
	11th to 20th	Day	50% 5% 16% 17% 11% 1	5042
	21st to end	Day	58% 5% 9% 16% 11% 1	5665
April	1st to 10th	Day	56% 5% 10% 16% 12% 1	2520
	11th to 20th	Day	50% 5% 10% 19% 15% 1	2624
	21st to end	Day	50% 6% 13% 16% 14% 2	2730
May	1st to 10th	Day	46% 6% 11% 20% 16% 1	7651
	11th to 20th	Day	44% 6% 10% 22% 16% 1	7630
	21st to end	Day	38% 5% 8% 22% 23% 3	9001
June	1st to 10th	Day	38% 6% 13% 26% 16% 1	2992
	11th to 20th	Day	39% 7% 13% 23% 17% 1	3150
	21st to end	Day	40% 8% 13% 25% 13% 1	2963
July	1st to 10th	Day	39% 7% 13% 24% 15% 1	6431
	11th to 20th	Day	31% 6% 12% 33% 17% 1	6356
	21st to end	Day	32% 8% 14% 27% 18% 1	6728
August	1st to 10th	Day	39% 7% 11% 27% 15% 1	4225
	11th to 20th	Day	36% 6% 13% 30% 14% 1	4213
	21st to end	Day	37% 7% 14% 27% 14% 1	4525
September	1st to 10th	Day	38% 8% 13% 27% 13% 2	2330
	11th to 20th	Day	35% 7% 15% 28% 15% 1	2200
	21st to end	Day	43% 7% 13% 25% 12%	2200
October	1st to 10th	Day	32% 4 9% 34% 18% 4	3567
	11th to 20th	Day	43% 6% 10% 29% 12%	3148
	21st to end	Day	55% 5% 12% 20% 7%	3180
November	1st to 10th	Day	48% 7% 13% 21% 10% 1	1852
	11th to 20th	Day	60% 6% 13% 14% 6% 1	1890
	21st to end	Day	66% 6% 11% 12% 4	1806
December	1st to 10th	Day	69% 7% 13% 9% 1	2454
	11th to 20th	Day	71% 5% 9% 12% 3	2691
	21st to end	Day	78% 4 6% 7% 4	4003
January	1st to 10th	Night	63% 6% 9% 13% 7% 1	8233
	11th to 20th	Night	74% 6% 7% 7% 5% 1	8280
	21st to end	Night	62% 7% 9% 13% 8%	9044
February	1st to 10th	Night	60% 7% 9% 17% 7% 1	2730
	11th to 20th	Night	57% 6% 11% 19% 7% 1	2480
	21st to end	Night	59% 5% 12% 16% 8% 1	2076
March	1st to 10th	Night	46% 5% 16% 22% 10% 1	5493
	11th to 20th	Night	42% 5% 20% 22% 10% 1	5138
	21st to end	Night	51% 6% 11% 20% 11% 1	5553
April	1st to 10th	Night	50% 4 10% 20% 14% 2	2100
	11th to 20th	Night	47% 4 9% 20% 17% 2	1943
	21st to end	Night	44% 6% 12% 22% 14% 3	1890
May	1st to 10th	Night	40% 6% 11% 20% 19% 3	5264
	11th to 20th	Night	41% 6% 10% 28% 14% 1	5235
	21st to end	Night	36% 5% 8% 24% 23% 4	5190
June	1st to 10th	Night	36% 7% 9% 26% 19% 2	1617
	11th to 20th	Night	37% 8% 13% 22% 20% 1	1470
	21st to end	Night	35% 7% 13% 27% 16% 2	1644
July	1st to 10th	Night	37% 6% 12% 25% 16% 5%	3660
	11th to 20th	Night	28% 6% 12% 35% 19% 1	3612
	21st to end	Night	31% 7% 16% 28% 18% 1	3832
August	1st to 10th	Night	32% 6% 16% 30% 15% 1	2900
	11th to 20th	Night	31% 6% 16% 31% 15% 1	2902
	21st to end	Night	32% 6% 13% 31% 17% 1	3355
September	1st to 10th	Night	32% 7% 13% 29% 18% 1	2049
	11th to 20th	Night	28% 6% 13% 37% 16% 1	2200
	21st to end	Night	40% 7% 13% 28% 11% 1	2200
October	1st to 10th	Night	28% 5% 11% 35% 20% 1	3613
	11th to 20th	Night	43% 5% 12% 25% 15% 1	3988
	21st to end	Night	47% 5% 11% 28% 10%	4610
November	1st to 10th	Night	44% 6% 14% 23% 12% 1	2666
	11th to 20th	Night	54% 8% 13% 17% 8% 1	2730
	21st to end	Night	61% 7% 14% 13% 4	2810
December	1st to 10th	Night	61% 7% 16% 12% 4	4949
	11th to 20th	Night	65% 5% 10% 11% 7% 1	5735
	21st to end	Night	73% 4 8% 7% 8%	7197

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	25% 20% 39% 10% 5%	330
	11th to 20th	Day	27% 22% 39% 8% 3	330
	21st to end	Day	28% 16% 37% 14% 4	363
February	1st to 10th	Day	25% 28% 32% 11% 3 1	330
	11th to 20th	Day	26% 27% 36% 8% 2	330
	21st to end	Day	34% 31% 29% 5% 1	273
March	1st to 10th	Day	29% 28% 35% 8% 1	330
	11th to 20th	Day	27% 20% 31% 16% 5%	518
	21st to end	Day	30% 18% 30% 17% 4 1	594
April	1st to 10th	Day	30% 19% 31% 15% 5% 1	540
	11th to 20th	Day	33% 18% 25% 15% 7% 2	532
	21st to end	Day	25% 16% 29% 21% 8% 1	540
May	1st to 10th	Day	24% 18% 34% 16% 6% 3	543
	11th to 20th	Day	20% 14% 32% 22% 8% 4	567
	21st to end	Day	16% 15% 32% 24% 11% 3	823
June	1st to 10th	Day	14% 15% 33% 27% 8% 3	780
	11th to 20th	Day	15% 14% 38% 21% 9% 3	780
	21st to end	Day	13% 13% 34% 26% 11% 3	780
July	1st to 10th	Day	8% 6% 31% 32% 16% 6%	771
	11th to 20th	Day	8% 11% 29% 30% 16% 6%	744
	21st to end	Day	9% 8% 32% 28% 17% 5%	794
August	1st to 10th	Day	8% 7% 25% 28% 21% 11%	531
	11th to 20th	Day	10% 6% 21% 34% 17% 11%	519
	21st to end	Day	14% 10% 22% 31% 16% 7%	583
September	1st to 10th	Day	12% 11% 29% 23% 14% 9%	530
	11th to 20th	Day	12% 7% 22% 26% 23% 9%	530
	21st to end	Day	20% 11% 23% 25% 16% 6%	530
October	1st to 10th	Day	21% 13% 28% 21% 15% 3	530
	11th to 20th	Day	26% 13% 34% 21% 5% 1	475
	21st to end	Day	27% 19% 35% 14% 4 1	363
November	1st to 10th	Day	28% 19% 35% 13% 5%	330
	11th to 20th	Day	28% 24% 34% 11% 3 1	330
	21st to end	Day	28% 27% 31% 11% 3	286
December	1st to 10th	Day	27% 25% 29% 13% 5% 1	220
	11th to 20th	Day	33% 23% 34% 9% 2	220
	21st to end	Day	36% 24% 29% 7% 4 1	349
January	1st to 10th	Night	23% 19% 34% 19% 4 1	1050
	11th to 20th	Night	24% 19% 33% 19% 5%	1050
	21st to end	Night	20% 13% 37% 24% 5%	1154
February	1st to 10th	Night	20% 18% 34% 23% 4	840
	11th to 20th	Night	22% 20% 33% 20% 4	823
	21st to end	Night	25% 20% 36% 17% 3	692
March	1st to 10th	Night	20% 17% 35% 22% 7%	840
	11th to 20th	Night	20% 20% 32% 22% 5%	840
	21st to end	Night	22% 16% 34% 23% 5% 1	914
April	1st to 10th	Night	22% 15% 36% 22% 5%	630
	11th to 20th	Night	23% 16% 30% 23% 6% 1	623
	21st to end	Night	22% 11% 31% 28% 7% 1	630
May	1st to 10th	Night	14% 11% 37% 31% 7% 1	630
	11th to 20th	Night	18% 9% 29% 32% 12% 1	621
	21st to end	Night	16% 7% 30% 30% 16% 1	683
June	1st to 10th	Night	13% 8% 28% 36% 13% 1	567
	11th to 20th	Night	14% 8% 33% 34% 11%	420
	21st to end	Night	12% 5% 28% 39% 14% 1	594
July	1st to 10th	Night	9% 3 22% 41% 21% 3	615
	11th to 20th	Night	8% 3 22% 41% 23% 3	597
	21st to end	Night	9% 4 26% 40% 20% 1	657
August	1st to 10th	Night	8% 2 23% 39% 26% 1	597
	11th to 20th	Night	9% 4 20% 39% 25% 3	594
	21st to end	Night	12% 4 21% 38% 23% 2	660
September	1st to 10th	Night	10% 6% 27% 30% 23% 4	649
	11th to 20th	Night	12% 4 22% 33% 25% 4	800
	21st to end	Night	17% 9% 24% 29% 19% 3	800
October	1st to 10th	Night	19% 9% 27% 29% 16% 1	800
	11th to 20th	Night	23% 14% 31% 24% 7% 1	800
	21st to end	Night	28% 14% 30% 22% 6% 1	880
November	1st to 10th	Night	21% 15% 33% 22% 9%	820
	11th to 20th	Night	22% 18% 32% 21% 5% 1	840
	21st to end	Night	26% 16% 34% 19% 4	840
December	1st to 10th	Night	25% 17% 32% 22% 4	978
	11th to 20th	Night	26% 18% 35% 17% 4 1	1050
	21st to end	Night	33% 14% 32% 19% 2	1155

Page generated at 2026-07-13 03:14:48. Version ac07

Copyright © 2026 Attilla Danko.