Cuyahoga Valley National Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cuyahoga Valley National Park clear sky chart from 2005-11-06 to 2026-05-17.

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	16% 11% 4 10% 5% 5% 4 4 5% 7% 29%	131587
	Night	16% 12% 5% 10% 5% 4 4 3 5% 6% 30%	131206
Transparency	Day	55% 2 10% 21% 11% 1	135220
	Night	56% 2 9% 20% 11% 1	135643
Seeing	Day	23% 14% 28% 20% 11% 4	16528
	Night	22% 11% 27% 26% 11% 1	26473

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	15% 21% 8% 24% 6% 4 3 2 3 4 11%	5258
	11th to 20th	Day	11% 22% 8% 19% 9% 6% 5% 2 3 4 11%	5280
	21st to end	Day	19% 17% 9% 13% 9% 7% 4 3 3 3 13%	5780
February	1st to 10th	Day	16% 19% 6% 11% 7% 4 3 3 4 5% 21%	1890
	11th to 20th	Day	16% 14% 7% 15% 8% 4 4 3 4 4 20%	1906
	21st to end	Day	17% 15% 5% 14% 7% 4 4 3 5% 5% 23%	1730
March	1st to 10th	Day	17% 13% 7% 13% 5% 4 3 2 4 6% 26%	4926
	11th to 20th	Day	12% 12% 5% 11% 5% 4 4 3 4 6% 35%	5090
	21st to end	Day	20% 13% 6% 9% 5% 4 4 3 4 5% 27%	5586
April	1st to 10th	Day	17% 14% 4 8% 5% 4 4 3 5% 7% 29%	2349
	11th to 20th	Day	18% 11% 3 7% 5% 4 5% 3 5% 6% 32%	2670
	21st to end	Day	19% 11% 3 7% 5% 4 4 3 4 7% 33%	2730
May	1st to 10th	Day	22% 9% 3 8% 5% 5% 5% 3 5% 6% 29%	5992
	11th to 20th	Day	19% 9% 3 7% 5% 4 4 4 6% 8% 32%	5939
	21st to end	Day	18% 8% 3 6% 4 4 5% 4 6% 8% 34%	6478
June	1st to 10th	Day	15% 7% 2 7% 5% 5% 4 4 7% 8% 37%	2800
	11th to 20th	Day	14% 6% 3 7% 6% 4 5% 4 7% 8% 37%	2800
	21st to end	Day	12% 5% 2 6% 4 5% 5% 5% 7% 10% 39%	2772
July	1st to 10th	Day	8% 6% 2 6% 5% 5% 6% 4 6% 10% 41%	5900
	11th to 20th	Day	10% 6% 3 6% 5% 5% 6% 5% 7% 10% 37%	5900
	21st to end	Day	11% 6% 2 7% 4 5% 5% 5% 6% 9% 40%	6424
August	1st to 10th	Day	12% 8% 3 8% 5% 5% 6% 5% 6% 8% 35%	4234
	11th to 20th	Day	11% 7% 2 7% 4 5% 6% 5% 8% 10% 35%	4174
	21st to end	Day	9% 5% 2 6% 5% 5% 6% 5% 7% 9% 39%	4591
September	1st to 10th	Day	14% 6% 2 5% 4 5% 5% 3 5% 8% 44%	2290
	11th to 20th	Day	11% 6% 2 6% 5% 4 5% 4 5% 8% 45%	2200
	21st to end	Day	20% 8% 3 6% 4 4 4 3 4 6% 38%	2200
October	1st to 10th	Day	16% 6% 2 7% 4 4 4 3 6% 7% 41%	2069
	11th to 20th	Day	19% 9% 3 8% 4 5% 3 4 5% 6% 35%	2000
	21st to end	Day	23% 9% 3 8% 5% 4 5% 3 5% 6% 29%	2195
November	1st to 10th	Day	13% 11% 4 7% 5% 5% 4 4 5% 6% 37%	1852
	11th to 20th	Day	18% 16% 4 7% 5% 4 4 3 5% 5% 28%	1869
	21st to end	Day	19% 19% 6% 10% 5% 5% 4 3 5% 6% 18%	1680
December	1st to 10th	Day	18% 16% 8% 16% 7% 4 4 3 4 4 17%	2680
	11th to 20th	Day	23% 21% 7% 11% 5% 3 3 2 3 5% 16%	3070
	21st to end	Day	26% 23% 7% 13% 5% 4 4 2 3 4 9%	4283
January	1st to 10th	Night	14% 20% 9% 23% 6% 4 3 2 3 3 10%	7635
	11th to 20th	Night	11% 20% 10% 19% 9% 6% 6% 3 3 3 11%	7680
	21st to end	Night	18% 19% 6% 12% 6% 5% 5% 3 4 5% 18%	8401
February	1st to 10th	Night	20% 15% 6% 12% 6% 5% 3 3 4 5% 21%	2730
	11th to 20th	Night	17% 14% 7% 12% 7% 6% 5% 4 4 4 21%	2598
	21st to end	Night	20% 15% 5% 12% 5% 5% 4 3 4 5% 24%	2076
March	1st to 10th	Night	22% 13% 4 9% 4 3 3 2 3 5% 31%	5147
	11th to 20th	Night	13% 10% 4 7% 4 4 4 4 5% 6% 38%	5090
	21st to end	Night	18% 12% 4 8% 5% 4 4 3 5% 5% 32%	5588
April	1st to 10th	Night	18% 14% 3 7% 6% 4 4 4 4 6% 29%	2270
	11th to 20th	Night	16% 10% 4 8% 4 4 6% 4 5% 6% 33%	1917
	21st to end	Night	15% 9% 2 7% 4 5% 5% 4 5% 6% 36%	1890
May	1st to 10th	Night	25% 10% 3 8% 4 4 4 4 5% 6% 27%	4123
	11th to 20th	Night	17% 9% 3 6% 4 4 4 3 5% 8% 38%	4086
	21st to end	Night	17% 7% 2 5% 3 4 4 4 7% 9% 38%	4358
June	1st to 10th	Night	10% 7% 2 6% 5% 5% 4 5% 6% 7% 43%	1600
	11th to 20th	Night	11% 5% 2 6% 6% 6% 5% 4 8% 7% 41%	1600
	21st to end	Night	11% 5% 2 5% 4 5% 5% 4 8% 10% 41%	1621
July	1st to 10th	Night	9% 6% 2 6% 4 5% 4 4 6% 9% 44%	4058
	11th to 20th	Night	9% 6% 2 6% 4 4 5% 4 7% 9% 42%	4057
	21st to end	Night	8% 6% 2 6% 5% 4 4 4 6% 8% 47%	4427
August	1st to 10th	Night	10% 7% 3 8% 6% 5% 5% 4 5% 8% 40%	2915
	11th to 20th	Night	13% 8% 3 8% 4 4 3 3 4 7% 43%	2875
	21st to end	Night	8% 5% 2 7% 5% 5% 6% 5% 6% 8% 43%	3272
September	1st to 10th	Night	12% 5% 2 5% 5% 4 4 4 5% 6% 48%	2105
	11th to 20th	Night	9% 4 1 5% 4 4 4 3 4 8% 54%	2200
	21st to end	Night	17% 7% 2 7% 5% 4 3 4 5% 7% 39%	2200
October	1st to 10th	Night	13% 6% 2 6% 4 3 4 3 5% 7% 45%	2330
	11th to 20th	Night	20% 7% 3 7% 5% 4 5% 3 5% 6% 36%	2400
	21st to end	Night	23% 10% 2 6% 4 4 4 3 5% 6% 31%	2642
November	1st to 10th	Night	14% 9% 3 6% 4 4 4 4 6% 6% 40%	2666
	11th to 20th	Night	17% 16% 4 8% 5% 5% 4 3 5% 6% 28%	2747
	21st to end	Night	21% 16% 5% 8% 5% 5% 4 4 5% 5% 23%	2940
December	1st to 10th	Night	16% 16% 7% 12% 6% 5% 4 3 5% 5% 20%	4720
	11th to 20th	Night	19% 21% 7% 12% 5% 4 3 3 4 4 18%	5345
	21st to end	Night	25% 21% 7% 12% 5% 4 4 3 4 4 13%	6897

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	80% 1 8% 7% 3	5259
	11th to 20th	Day	80% 2 6% 7% 6%	5280
	21st to end	Day	78% 1 6% 12% 3	5780
February	1st to 10th	Day	67% 1 9% 15% 7%	1890
	11th to 20th	Day	68% 3 7% 14% 7% 1	1915
	21st to end	Day	65% 2 11% 15% 7% 1	1730
March	1st to 10th	Day	62% 1 9% 21% 6%	4926
	11th to 20th	Day	53% 2 11% 25% 8% 1	5090
	21st to end	Day	61% 1 7% 18% 12% 1	5586
April	1st to 10th	Day	56% 2 11% 18% 12% 1	2349
	11th to 20th	Day	54% 2 11% 18% 13% 2	2670
	21st to end	Day	54% 2 10% 22% 11% 2	2730
May	1st to 10th	Day	58% 2 8% 19% 11% 3	6027
	11th to 20th	Day	52% 2 11% 23% 12% 1	5943
	21st to end	Day	49% 2 11% 22% 13% 3	6493
June	1st to 10th	Day	45% 3 10% 26% 14% 1	2800
	11th to 20th	Day	45% 3 13% 22% 15% 1	2800
	21st to end	Day	39% 5% 13% 25% 17% 2	2772
July	1st to 10th	Day	39% 2 11% 30% 16% 2	5835
	11th to 20th	Day	42% 3 13% 26% 15% 1	5831
	21st to end	Day	41% 3 10% 23% 21% 2	6240
August	1st to 10th	Day	47% 3 13% 25% 12% 1	4221
	11th to 20th	Day	42% 3 11% 31% 12% 1	4213
	21st to end	Day	40% 3 13% 31% 11% 2	4591
September	1st to 10th	Day	40% 4 12% 24% 18% 3	2290
	11th to 20th	Day	39% 3 13% 28% 17% 2	2200
	21st to end	Day	49% 2 9% 23% 16% 1	2200
October	1st to 10th	Day	34% 3 12% 31% 20% 1	3368
	11th to 20th	Day	47% 2 10% 22% 16% 4	3240
	21st to end	Day	44% 2 12% 26% 16% 1	3521
November	1st to 10th	Day	49% 3 9% 25% 14% 1	1852
	11th to 20th	Day	59% 2 9% 19% 9% 3	1869
	21st to end	Day	68% 2 9% 15% 6%	1680
December	1st to 10th	Day	72% 2 11% 13% 2	2680
	11th to 20th	Day	74% 1 8% 14% 3	3066
	21st to end	Day	82% 1 7% 9% 2	4283
January	1st to 10th	Night	81% 1 5% 10% 3	7636
	11th to 20th	Night	80% 1 6% 8% 4	7680
	21st to end	Night	71% 1 8% 14% 6%	8401
February	1st to 10th	Night	67% 2 8% 16% 6%	2730
	11th to 20th	Night	66% 3 8% 16% 7%	2600
	21st to end	Night	65% 2 8% 15% 9% 1	2076
March	1st to 10th	Night	59% 1 10% 21% 9%	5147
	11th to 20th	Night	47% 2 13% 26% 11% 1	5090
	21st to end	Night	56% 1 7% 21% 14% 1	5588
April	1st to 10th	Night	56% 3 9% 17% 14% 1	2270
	11th to 20th	Night	51% 3 11% 18% 14% 3	1917
	21st to end	Night	48% 2 10% 22% 16% 2	1890
May	1st to 10th	Night	60% 2 8% 16% 9% 5%	4150
	11th to 20th	Night	47% 2 10% 25% 14% 2	4087
	21st to end	Night	44% 3 12% 25% 14% 2	4365
June	1st to 10th	Night	41% 4 10% 26% 17% 3	1600
	11th to 20th	Night	40% 3 14% 22% 18% 2	1600
	21st to end	Night	38% 5% 12% 26% 17% 2	1621
July	1st to 10th	Night	38% 2 12% 26% 18% 3	4015
	11th to 20th	Night	39% 3 13% 29% 14% 1	4006
	21st to end	Night	36% 3 12% 21% 27% 2	4297
August	1st to 10th	Night	43% 3 11% 26% 15% 2	2904
	11th to 20th	Night	43% 3 10% 31% 13% 1	2902
	21st to end	Night	39% 3 12% 30% 14% 2	3272
September	1st to 10th	Night	36% 3 10% 29% 18% 4	2105
	11th to 20th	Night	31% 3 12% 29% 24% 2	2200
	21st to end	Night	45% 3 10% 21% 19% 1	2200
October	1st to 10th	Night	33% 2 8% 31% 25% 1	3811
	11th to 20th	Night	47% 1 9% 22% 19% 2	3899
	21st to end	Night	42% 2 9% 29% 16% 1	4266
November	1st to 10th	Night	45% 2 11% 24% 15% 3	2666
	11th to 20th	Night	59% 2 8% 19% 10% 2	2747
	21st to end	Night	63% 2 11% 18% 5%	2940
December	1st to 10th	Night	66% 2 10% 17% 4	4720
	11th to 20th	Night	72% 1 9% 16% 2	5348
	21st to end	Night	77% 2 9% 11% 1	6897

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	32% 23% 32% 9% 3 1	330
	11th to 20th	Day	33% 26% 32% 7% 2	330
	21st to end	Day	32% 29% 28% 9% 2	363
February	1st to 10th	Day	31% 24% 32% 11% 1 1	330
	11th to 20th	Day	31% 28% 31% 9% 2	330
	21st to end	Day	32% 28% 34% 5%	273
March	1st to 10th	Day	28% 21% 34% 14% 3	482
	11th to 20th	Day	33% 17% 32% 13% 4 1	540
	21st to end	Day	33% 21% 27% 15% 4	594
April	1st to 10th	Day	29% 22% 28% 15% 6% 1	540
	11th to 20th	Day	29% 20% 25% 16% 7% 3	532
	21st to end	Day	26% 18% 31% 18% 6% 1	540
May	1st to 10th	Day	30% 17% 29% 15% 7% 2	543
	11th to 20th	Day	24% 12% 34% 19% 7% 4	551
	21st to end	Day	19% 11% 27% 23% 16% 4	573
June	1st to 10th	Day	18% 11% 34% 25% 10% 3	530
	11th to 20th	Day	19% 9% 24% 32% 12% 4	530
	21st to end	Day	15% 9% 32% 27% 12% 5%	530
July	1st to 10th	Day	12% 3 24% 31% 22% 8%	525
	11th to 20th	Day	14% 4 27% 28% 19% 7%	524
	21st to end	Day	13% 5% 24% 30% 20% 8%	576
August	1st to 10th	Day	14% 5% 21% 30% 21% 9%	526
	11th to 20th	Day	16% 6% 23% 26% 19% 9%	519
	21st to end	Day	11% 6% 23% 29% 20% 11%	583
September	1st to 10th	Day	17% 7% 20% 27% 19% 10%	530
	11th to 20th	Day	11% 3 19% 28% 27% 12%	530
	21st to end	Day	26% 7% 23% 24% 15% 5%	530
October	1st to 10th	Day	15% 8% 29% 25% 19% 4	530
	11th to 20th	Day	23% 16% 35% 16% 8% 2	530
	21st to end	Day	32% 16% 30% 19% 3	578
November	1st to 10th	Day	23% 20% 35% 12% 9% 1	330
	11th to 20th	Day	36% 22% 25% 14% 3 1	319
	21st to end	Day	30% 23% 38% 9% 1	220
December	1st to 10th	Day	29% 21% 35% 11% 3 1	220
	11th to 20th	Day	29% 28% 30% 11% 3	220
	21st to end	Day	37% 21% 30% 11% 1	297
January	1st to 10th	Night	29% 19% 33% 15% 4	840
	11th to 20th	Night	34% 20% 28% 15% 3	840
	21st to end	Night	28% 20% 29% 20% 3	924
February	1st to 10th	Night	29% 17% 32% 20% 3	840
	11th to 20th	Night	26% 21% 32% 18% 2	823
	21st to end	Night	29% 19% 34% 15% 2	692
March	1st to 10th	Night	26% 15% 34% 20% 4	840
	11th to 20th	Night	25% 17% 30% 22% 5% 1	840
	21st to end	Night	25% 13% 33% 22% 6% 1	924
April	1st to 10th	Night	27% 14% 31% 23% 5% 1	840
	11th to 20th	Night	25% 11% 34% 20% 8% 1	673
	21st to end	Night	21% 10% 33% 28% 7%	630
May	1st to 10th	Night	22% 10% 27% 31% 8% 1	630
	11th to 20th	Night	21% 7% 25% 36% 10% 1	609
	21st to end	Night	14% 3 25% 37% 19% 2	625
June	1st to 10th	Night	12% 4 32% 37% 14% 1	400
	11th to 20th	Night	14% 4 27% 44% 12%	400
	21st to end	Night	13% 5% 25% 38% 18% 1	421
July	1st to 10th	Night	11% 1 15% 43% 27% 3	585
	11th to 20th	Night	11% 2 20% 38% 26% 3	582
	21st to end	Night	10% 3 15% 43% 27% 2	657
August	1st to 10th	Night	10% 2 15% 43% 27% 3	597
	11th to 20th	Night	14% 1 12% 39% 30% 3	594
	21st to end	Night	12% 1 18% 34% 31% 3	683
September	1st to 10th	Night	14% 4 19% 33% 27% 4	800
	11th to 20th	Night	10% 2 16% 36% 31% 4	800
	21st to end	Night	20% 6% 22% 30% 18% 4	800
October	1st to 10th	Night	16% 7% 24% 30% 21% 2	800
	11th to 20th	Night	25% 10% 28% 27% 9% 2	800
	21st to end	Night	27% 12% 30% 25% 6%	880
November	1st to 10th	Night	20% 13% 30% 26% 11%	820
	11th to 20th	Night	28% 17% 28% 19% 6% 1	840
	21st to end	Night	32% 16% 30% 16% 6%	840
December	1st to 10th	Night	33% 17% 29% 16% 5%	840
	11th to 20th	Night	28% 19% 33% 17% 3	840
	21st to end	Night	31% 17% 30% 20% 2	924

Page generated at 2026-05-14 01:59:01. Version ac07

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