Onondaga Cave State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Onondaga Cave State Park clear sky chart from 2005-11-06 to 2025-07-21.

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% 8% 3 6% 4 4 4 4 5% 7% 43%	120097
	Night	14% 8% 3 7% 4 4 4 3 4 6% 44%	119227
Transparency	Day	39% 5% 11% 24% 17% 3	123735
	Night	40% 5% 11% 23% 18% 3	123733
Seeing	Day	17% 12% 28% 25% 14% 4	16561
	Night	18% 12% 30% 27% 12% 1	26365

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% 12% 5% 13% 4 4 3 3 4 5% 33%	3663
	11th to 20th	Day	9% 11% 4 8% 4 5% 3 3 4 6% 43%	4080
	21st to end	Day	18% 11% 4 7% 3 3 3 3 5% 6% 38%	4488
February	1st to 10th	Day	15% 12% 4 8% 5% 5% 4 3 4 6% 34%	1800
	11th to 20th	Day	16% 10% 3 8% 5% 4 3 4 5% 5% 37%	1891
	21st to end	Day	13% 11% 3 7% 4 3 4 4 5% 7% 39%	1650
March	1st to 10th	Day	16% 11% 2 5% 3 3 3 2 3 4 48%	4706
	11th to 20th	Day	10% 7% 2 4 3 3 3 3 5% 6% 53%	4980
	21st to end	Day	13% 8% 3 7% 5% 5% 5% 4 5% 8% 36%	5662
April	1st to 10th	Day	13% 6% 2 6% 4 4 4 3 6% 7% 44%	2400
	11th to 20th	Day	17% 9% 2 5% 4 4 4 3 5% 6% 41%	2374
	21st to end	Day	19% 8% 3 7% 5% 4 4 3 5% 7% 35%	2400
May	1st to 10th	Day	16% 8% 3 7% 5% 5% 6% 4 7% 9% 31%	5441
	11th to 20th	Day	16% 8% 3 7% 4 5% 5% 3 5% 8% 36%	6245
	21st to end	Day	16% 7% 3 6% 5% 4 4 3 5% 6% 41%	6935
June	1st to 10th	Day	10% 5% 2 6% 4 5% 5% 4 6% 8% 45%	2800
	11th to 20th	Day	8% 5% 2 5% 4 4 5% 4 6% 9% 48%	2800
	21st to end	Day	6% 3 1 4 5% 5% 5% 5% 8% 10% 48%	2800
July	1st to 10th	Day	13% 5% 2 6% 4 4 5% 4 7% 8% 41%	4580
	11th to 20th	Day	5% 4 2 6% 4 5% 5% 5% 6% 10% 48%	4494
	21st to end	Day	9% 5% 2 7% 6% 5% 6% 5% 8% 10% 38%	4466
August	1st to 10th	Day	6% 3 1 5% 4 4 5% 4 7% 10% 52%	4104
	11th to 20th	Day	12% 5% 2 6% 4 5% 5% 4 5% 7% 45%	3764
	21st to end	Day	7% 4 2 5% 4 4 5% 4 6% 8% 52%	4180
September	1st to 10th	Day	13% 5% 2 4 4 3 4 3 6% 8% 49%	2280
	11th to 20th	Day	11% 5% 2 6% 3 3 4 3 6% 6% 50%	2280
	21st to end	Day	9% 5% 3 5% 3 4 4 4 5% 6% 52%	2035
October	1st to 10th	Day	10% 5% 2 5% 4 3 3 2 4 6% 58%	1900
	11th to 20th	Day	15% 6% 2 4 3 2 3 3 3 5% 54%	1900
	21st to end	Day	17% 8% 2 5% 3 3 3 3 4 5% 47%	2090
November	1st to 10th	Day	12% 6% 1 5% 2 4 3 3 4 5% 54%	1814
	11th to 20th	Day	14% 8% 3 5% 4 3 4 2 5% 6% 47%	1800
	21st to end	Day	15% 11% 2 7% 3 3 3 3 4 5% 44%	1695
December	1st to 10th	Day	10% 10% 3 6% 4 3 3 3 4 5% 50%	2610
	11th to 20th	Day	13% 11% 4 6% 4 4 3 3 5% 6% 41%	3008
	21st to end	Day	21% 18% 5% 8% 5% 4 3 3 4 5% 26%	3982
January	1st to 10th	Night	15% 11% 6% 13% 5% 4 4 2 3 4 32%	6284
	11th to 20th	Night	11% 9% 5% 13% 5% 5% 5% 3 3 4 37%	5900
	21st to end	Night	18% 12% 4 8% 4 3 3 2 3 3 39%	6490
February	1st to 10th	Night	17% 12% 4 8% 4 3 3 3 5% 5% 36%	2600
	11th to 20th	Night	15% 9% 4 8% 5% 4 3 3 4 5% 40%	2393
	21st to end	Night	16% 10% 2 9% 4 3 3 3 5% 5% 41%	1980
March	1st to 10th	Night	18% 12% 3 6% 3 3 3 3 3 5% 42%	5189
	11th to 20th	Night	13% 8% 2 5% 4 3 4 3 4 6% 49%	4980
	21st to end	Night	16% 10% 3 7% 5% 5% 4 4 5% 6% 34%	5266
April	1st to 10th	Night	11% 7% 2 6% 4 3 3 3 5% 9% 47%	2000
	11th to 20th	Night	14% 9% 2 5% 4 3 3 4 4 6% 46%	1975
	21st to end	Night	20% 7% 3 6% 4 4 3 3 5% 6% 40%	2000
May	1st to 10th	Night	19% 7% 3 7% 4 4 4 4 5% 7% 36%	4453
	11th to 20th	Night	14% 8% 3 6% 4 4 4 4 5% 7% 42%	3653
	21st to end	Night	17% 8% 2 7% 5% 4 4 4 5% 7% 37%	3942
June	1st to 10th	Night	8% 5% 2 5% 5% 5% 4 4 6% 8% 48%	1600
	11th to 20th	Night	7% 4 2 4 3 3 4 4 6% 12% 53%	1600
	21st to end	Night	4 3 1 3 3 5% 3 5% 6% 9% 59%	1600
July	1st to 10th	Night	13% 5% 2 5% 4 4 3 3 5% 10% 47%	2610
	11th to 20th	Night	6% 3 1 4 3 3 3 3 6% 8% 60%	2691
	21st to end	Night	7% 5% 2 6% 5% 5% 5% 4 6% 10% 44%	3098
August	1st to 10th	Night	5% 2 1 4 3 4 4 3 5% 8% 60%	2836
	11th to 20th	Night	11% 4 2 6% 4 3 4 4 5% 8% 49%	3063
	21st to end	Night	6% 3 1 4 3 3 4 3 5% 8% 59%	3476
September	1st to 10th	Night	12% 6% 2 5% 4 3 3 2 5% 6% 53%	1900
	11th to 20th	Night	9% 5% 2 5% 5% 3 4 4 5% 7% 53%	1900
	21st to end	Night	10% 4 2 5% 3 4 4 3 4 6% 55%	2121
October	1st to 10th	Night	8% 3 1 4 3 2 3 3 4 7% 61%	2280
	11th to 20th	Night	15% 5% 1 4 3 2 3 2 4 5% 54%	2280
	21st to end	Night	19% 7% 2 4 3 3 3 2 4 5% 48%	2508
November	1st to 10th	Night	12% 5% 2 4 2 3 2 3 5% 5% 56%	2483
	11th to 20th	Night	14% 7% 3 5% 4 3 3 3 4 7% 49%	2600
	21st to end	Night	16% 10% 3 5% 4 3 3 2 4 6% 45%	2701
December	1st to 10th	Night	12% 9% 3 6% 4 3 3 2 4 6% 47%	4580
	11th to 20th	Night	16% 9% 4 6% 4 4 3 3 4 5% 43%	5199
	21st to end	Night	23% 16% 4 9% 4 4 4 3 4 4 24%	6996

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	53% 4 10% 20% 12% 2	3664
	11th to 20th	Day	42% 5% 6% 25% 17% 4	4080
	21st to end	Day	48% 3 9% 16% 17% 8%	4488
February	1st to 10th	Day	52% 4 10% 22% 12% 1	1800
	11th to 20th	Day	48% 4 10% 18% 15% 5%	1901
	21st to end	Day	44% 5% 8% 23% 15% 5%	1650
March	1st to 10th	Day	42% 4 5% 21% 19% 9%	4706
	11th to 20th	Day	32% 4 8% 24% 24% 8%	4980
	21st to end	Day	44% 7% 14% 26% 9%	5664
April	1st to 10th	Day	38% 6% 12% 24% 19% 2	2400
	11th to 20th	Day	44% 5% 11% 21% 15% 3	2374
	21st to end	Day	48% 6% 11% 21% 12% 1	2400
May	1st to 10th	Day	47% 8% 13% 20% 12%	5476
	11th to 20th	Day	45% 6% 10% 23% 14% 1	6249
	21st to end	Day	43% 6% 9% 23% 17% 1	6949
June	1st to 10th	Day	35% 9% 13% 26% 16% 2	2800
	11th to 20th	Day	30% 8% 13% 27% 19% 3	2800
	21st to end	Day	28% 9% 18% 26% 15% 5%	2800
July	1st to 10th	Day	39% 6% 12% 29% 13% 3	4511
	11th to 20th	Day	30% 6% 14% 32% 15% 2	4419
	21st to end	Day	40% 5% 18% 27% 8% 1	4326
August	1st to 10th	Day	27% 6% 16% 32% 18%	4090
	11th to 20th	Day	39% 5% 12% 25% 17% 2	3800
	21st to end	Day	30% 4 15% 35% 13% 3	4179
September	1st to 10th	Day	33% 7% 11% 26% 18% 5%	2280
	11th to 20th	Day	35% 6% 8% 26% 25% 2	2280
	21st to end	Day	32% 6% 8% 27% 24% 3	2035
October	1st to 10th	Day	17% 3 6% 19% 45% 9%	3160
	11th to 20th	Day	23% 2 6% 21% 37% 10%	3140
	21st to end	Day	31% 3 7% 30% 26% 3	3428
November	1st to 10th	Day	35% 4 10% 23% 23% 6%	1814
	11th to 20th	Day	38% 3 9% 23% 21% 6%	1800
	21st to end	Day	43% 4 9% 27% 16% 1	1695
December	1st to 10th	Day	38% 4 9% 34% 15% 1	2610
	11th to 20th	Day	46% 3 9% 22% 19% 1	3005
	21st to end	Day	62% 5% 11% 13% 8% 1	3982
January	1st to 10th	Night	57% 4 8% 19% 11% 1	6284
	11th to 20th	Night	50% 4 7% 23% 14% 2	5900
	21st to end	Night	51% 3 8% 19% 16% 3	6490
February	1st to 10th	Night	51% 4 10% 20% 13% 2	2600
	11th to 20th	Night	46% 4 10% 21% 16% 3	2394
	21st to end	Night	45% 4 9% 22% 16% 4	1980
March	1st to 10th	Night	47% 3 6% 21% 19% 4	5189
	11th to 20th	Night	37% 4 9% 22% 20% 8%	4980
	21st to end	Night	48% 7% 12% 22% 10% 1	5266
April	1st to 10th	Night	34% 6% 12% 27% 19% 3	2000
	11th to 20th	Night	38% 5% 11% 24% 17% 5%	1975
	21st to end	Night	45% 6% 9% 23% 16% 1	2000
May	1st to 10th	Night	47% 7% 14% 18% 12% 2	4483
	11th to 20th	Night	41% 6% 12% 23% 15% 2	3654
	21st to end	Night	44% 8% 11% 22% 13% 2	3950
June	1st to 10th	Night	32% 8% 15% 26% 17% 3	1600
	11th to 20th	Night	24% 7% 14% 28% 23% 4	1600
	21st to end	Night	20% 8% 17% 29% 20% 7%	1600
July	1st to 10th	Night	35% 5% 14% 26% 16% 3	2570
	11th to 20th	Night	22% 5% 12% 39% 20% 2	2643
	21st to end	Night	36% 6% 17% 26% 13% 2	2999
August	1st to 10th	Night	22% 6% 19% 31% 21% 1	2826
	11th to 20th	Night	33% 6% 16% 26% 16% 3	3093
	21st to end	Night	24% 4 16% 37% 17% 3	3476
September	1st to 10th	Night	32% 5% 10% 26% 22% 6%	1900
	11th to 20th	Night	30% 5% 11% 24% 27% 2	1900
	21st to end	Night	30% 6% 9% 24% 27% 3	2121
October	1st to 10th	Night	14% 3 7% 17% 50% 10%	3800
	11th to 20th	Night	22% 2 7% 21% 35% 13%	3779
	21st to end	Night	32% 2 7% 27% 27% 4	4120
November	1st to 10th	Night	31% 3 12% 27% 22% 5%	2483
	11th to 20th	Night	37% 4 7% 23% 23% 5%	2600
	21st to end	Night	43% 4 9% 24% 18% 2	2701
December	1st to 10th	Night	40% 3 9% 32% 15% 1	4580
	11th to 20th	Night	45% 3 11% 22% 18% 1	5201
	21st to end	Night	63% 5% 11% 14% 6% 1	6996

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% 25% 34% 15% 2	300
	11th to 20th	Day	30% 21% 38% 11%	300
	21st to end	Day	22% 29% 38% 10% 2	330
February	1st to 10th	Day	27% 26% 32% 15% 1	300
	11th to 20th	Day	31% 27% 30% 10% 1 1	300
	21st to end	Day	29% 24% 35% 11% 1	249
March	1st to 10th	Day	23% 25% 39% 11% 2	300
	11th to 20th	Day	32% 22% 30% 12% 3 1	300
	21st to end	Day	33% 21% 33% 12% 2	414
April	1st to 10th	Day	24% 18% 34% 17% 6%	500
	11th to 20th	Day	29% 17% 29% 19% 5% 1	492
	21st to end	Day	23% 17% 35% 19% 5% 1	500
May	1st to 10th	Day	22% 17% 34% 21% 6% 1	513
	11th to 20th	Day	19% 13% 28% 27% 11% 2	725
	21st to end	Day	15% 9% 35% 24% 12% 5%	789
June	1st to 10th	Day	12% 7% 25% 28% 24% 5%	730
	11th to 20th	Day	9% 4 26% 37% 21% 4	730
	21st to end	Day	5% 8% 28% 38% 17% 3	730
July	1st to 10th	Day	14% 3 15% 30% 28% 9%	721
	11th to 20th	Day	5% 4 20% 38% 27% 6%	718
	21st to end	Day	10% 4 17% 36% 26% 7%	740
August	1st to 10th	Day	9% 1 20% 39% 24% 7%	676
	11th to 20th	Day	12% 3 21% 33% 24% 8%	502
	21st to end	Day	11% 1 16% 31% 33% 8%	539
September	1st to 10th	Day	13% 4 16% 33% 26% 8%	490
	11th to 20th	Day	9% 3 19% 33% 25% 12%	490
	21st to end	Day	11% 9% 24% 32% 17% 7%	423
October	1st to 10th	Day	12% 11% 29% 31% 12% 5%	300
	11th to 20th	Day	19% 17% 33% 22% 7% 1	300
	21st to end	Day	30% 19% 29% 18% 4	330
November	1st to 10th	Day	17% 13% 42% 17% 9% 2	300
	11th to 20th	Day	24% 18% 33% 15% 8% 1	300
	21st to end	Day	28% 18% 30% 20% 4	300
December	1st to 10th	Day	19% 26% 33% 13% 6% 3	300
	11th to 20th	Day	24% 22% 36% 14% 3 1	300
	21st to end	Day	31% 22% 34% 11% 3	330
January	1st to 10th	Night	22% 21% 36% 18% 3	1000
	11th to 20th	Night	23% 24% 33% 17% 3	1000
	21st to end	Night	20% 20% 38% 20% 1	1100
February	1st to 10th	Night	24% 19% 38% 17% 2	1000
	11th to 20th	Night	22% 19% 40% 17% 2	838
	21st to end	Night	25% 20% 36% 18% 1	660
March	1st to 10th	Night	25% 17% 38% 18% 2	720
	11th to 20th	Night	25% 15% 38% 21% 3	600
	21st to end	Night	27% 16% 33% 20% 4	660
April	1st to 10th	Night	16% 17% 40% 23% 4	600
	11th to 20th	Night	19% 16% 33% 26% 5%	593
	21st to end	Night	24% 12% 38% 19% 7%	600
May	1st to 10th	Night	18% 9% 34% 30% 9%	600
	11th to 20th	Night	18% 8% 28% 32% 13% 1	591
	21st to end	Night	13% 7% 28% 34% 16% 3	650
June	1st to 10th	Night	10% 6% 20% 38% 25% 2	600
	11th to 20th	Night	8% 2 25% 43% 20% 2	600
	21st to end	Night	4 2 26% 43% 23% 2	600
July	1st to 10th	Night	11% 1 12% 37% 31% 7%	585
	11th to 20th	Night	5% 3 16% 42% 31% 3	582
	21st to end	Night	7% 2 16% 44% 28% 3	624
August	1st to 10th	Night	7% 2 14% 42% 33% 2	567
	11th to 20th	Night	8% 1 18% 38% 32% 3	564
	21st to end	Night	6% 2 15% 35% 37% 5%	627
September	1st to 10th	Night	14% 2 14% 35% 29% 5%	570
	11th to 20th	Night	12% 3 14% 37% 30% 6%	570
	21st to end	Night	10% 7% 24% 30% 24% 5%	727
October	1st to 10th	Night	9% 4 28% 34% 22% 3	760
	11th to 20th	Night	18% 12% 32% 28% 11%	760
	21st to end	Night	23% 14% 32% 24% 7%	836
November	1st to 10th	Night	14% 10% 38% 29% 8% 1	780
	11th to 20th	Night	20% 16% 33% 23% 7%	800
	21st to end	Night	23% 17% 34% 21% 5%	901
December	1st to 10th	Night	23% 15% 37% 20% 4 1	1000
	11th to 20th	Night	24% 13% 38% 21% 4	1000
	21st to end	Night	27% 18% 34% 18% 2	1100

Page generated at 2025-07-18 00:10:03. Version ac07

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