Chillicothe
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chillicothe clear sky chart from 2005-11-06 to 2025-10-04.

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	12% 8% 3 7% 4 4 4 4 5% 7% 43%	126437
	Night	12% 7% 3 7% 4 4 4 3 5% 7% 45%	123168
Transparency	Day	40% 4 12% 25% 16% 2	130042
	Night	39% 4 11% 25% 18% 3	127639
Seeing	Day	15% 10% 27% 28% 16% 4	17009
	Night	15% 9% 31% 32% 12% 1	26765

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	14% 10% 4 11% 4 5% 4 3 5% 6% 33%	3873
	11th to 20th	Day	8% 9% 4 9% 6% 6% 7% 3 4 5% 39%	4080
	21st to end	Day	14% 13% 6% 11% 5% 4 4 3 4 5% 31%	4488
February	1st to 10th	Day	14% 12% 3 8% 5% 4 4 4 6% 8% 33%	1800
	11th to 20th	Day	14% 10% 5% 7% 4 4 3 2 5% 6% 39%	1754
	21st to end	Day	12% 10% 3 7% 4 4 4 4 5% 6% 43%	1657
March	1st to 10th	Day	16% 9% 3 4 3 2 3 2 3 5% 49%	4936
	11th to 20th	Day	9% 7% 2 6% 4 4 4 3 5% 7% 50%	4980
	21st to end	Day	15% 13% 3 7% 5% 5% 5% 4 5% 7% 31%	5462
April	1st to 10th	Day	16% 8% 3 7% 4 4 4 3 5% 6% 41%	2375
	11th to 20th	Day	15% 9% 2 7% 4 4 3 3 5% 7% 40%	2374
	21st to end	Day	22% 8% 3 7% 5% 4 4 4 5% 8% 32%	2475
May	1st to 10th	Day	14% 7% 2 6% 4 4 4 4 6% 8% 40%	5862
	11th to 20th	Day	15% 7% 2 6% 4 3 4 4 5% 7% 44%	5971
	21st to end	Day	17% 7% 3 6% 4 4 4 3 6% 7% 41%	6935
June	1st to 10th	Day	7% 5% 2 6% 5% 4 5% 4 7% 9% 46%	2800
	11th to 20th	Day	7% 6% 2 6% 5% 4 5% 4 7% 9% 46%	2800
	21st to end	Day	8% 4 2 5% 5% 4 4 5% 6% 10% 47%	2800
July	1st to 10th	Day	8% 6% 3 7% 5% 4 4 4 6% 9% 45%	6360
	11th to 20th	Day	8% 6% 3 7% 5% 4 5% 4 6% 9% 44%	5956
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 5% 7% 10% 43%	6422
August	1st to 10th	Day	5% 3 2 4 4 4 5% 5% 7% 10% 51%	4234
	11th to 20th	Day	11% 5% 2 6% 4 5% 4 4 7% 8% 45%	4171
	21st to end	Day	5% 5% 2 5% 4 4 4 4 6% 9% 53%	4322
September	1st to 10th	Day	12% 4 1 5% 3 3 3 3 5% 7% 53%	2400
	11th to 20th	Day	10% 4 2 5% 4 4 4 4 6% 8% 49%	2325
	21st to end	Day	9% 5% 2 4 4 4 4 4 4 6% 55%	2127
October	1st to 10th	Day	13% 5% 3 5% 4 3 3 3 4 6% 52%	1930
	11th to 20th	Day	13% 6% 2 5% 4 3 3 3 4 4 54%	1900
	21st to end	Day	15% 7% 2 6% 3 4 3 3 5% 6% 46%	2090
November	1st to 10th	Day	11% 7% 2 4 2 3 3 3 5% 6% 53%	1929
	11th to 20th	Day	15% 7% 3 5% 4 3 4 4 5% 6% 46%	1649
	21st to end	Day	17% 11% 3 5% 3 3 3 3 4 6% 43%	1600
December	1st to 10th	Day	6% 6% 3 8% 4 3 4 3 4 7% 53%	2610
	11th to 20th	Day	12% 8% 4 9% 4 4 4 3 4 6% 42%	3008
	21st to end	Day	20% 16% 8% 12% 4 4 4 3 4 4 21%	3982
January	1st to 10th	Night	12% 10% 5% 15% 6% 5% 4 4 5% 5% 30%	6076
	11th to 20th	Night	9% 10% 4 10% 6% 6% 5% 4 6% 5% 36%	5900
	21st to end	Night	14% 11% 6% 10% 5% 4 4 2 4 5% 36%	6490
February	1st to 10th	Night	13% 11% 4 7% 5% 4 4 3 5% 6% 37%	2600
	11th to 20th	Night	13% 9% 4 7% 4 4 3 3 6% 6% 41%	2533
	21st to end	Night	13% 8% 3 6% 3 3 3 3 4 6% 47%	1988
March	1st to 10th	Night	17% 9% 3 5% 3 3 3 2 4 4 47%	4919
	11th to 20th	Night	11% 6% 2 5% 3 3 3 2 5% 6% 54%	4980
	21st to end	Night	16% 9% 4 8% 5% 5% 4 4 6% 7% 32%	5467
April	1st to 10th	Night	11% 7% 3 6% 4 3 5% 3 4 7% 47%	2025
	11th to 20th	Night	14% 9% 2 6% 4 4 4 3 4 6% 44%	1975
	21st to end	Night	15% 9% 3 6% 4 4 5% 3 5% 6% 40%	1920
May	1st to 10th	Night	13% 8% 2 6% 4 4 4 4 6% 8% 42%	4053
	11th to 20th	Night	13% 6% 2 5% 4 3 3 4 5% 8% 47%	3926
	21st to end	Night	14% 6% 3 6% 4 3 4 3 4 6% 46%	3942
June	1st to 10th	Night	6% 3 2 4 3 4 5% 4 7% 10% 53%	1600
	11th to 20th	Night	5% 4 2 5% 4 4 5% 5% 6% 11% 50%	1600
	21st to end	Night	6% 5% 1 3 4 3 4 3 6% 9% 56%	1600
July	1st to 10th	Night	9% 5% 2 6% 4 3 4 3 6% 10% 49%	3618
	11th to 20th	Night	5% 4 2 7% 4 5% 4 4 6% 9% 50%	4003
	21st to end	Night	8% 5% 2 5% 4 4 4 4 8% 11% 44%	4449
August	1st to 10th	Night	2 2 1 4 3 4 4 4 7% 10% 58%	2926
	11th to 20th	Night	12% 5% 2 4 3 3 3 2 4 7% 54%	2888
	21st to end	Night	4 3 2 6% 3 4 4 3 6% 9% 57%	3574
September	1st to 10th	Night	10% 5% 2 5% 3 3 3 3 4 6% 57%	2000
	11th to 20th	Night	10% 4 1 4 4 3 4 4 7% 7% 53%	2070
	21st to end	Night	7% 4 2 5% 4 4 4 3 5% 5% 57%	2251
October	1st to 10th	Night	10% 6% 2 5% 3 3 3 2 5% 6% 56%	2317
	11th to 20th	Night	14% 4 2 5% 4 4 2 2 4 5% 55%	2280
	21st to end	Night	17% 7% 2 5% 3 3 3 2 4 5% 50%	2508
November	1st to 10th	Night	10% 5% 1 4 2 2 3 3 4 6% 59%	2366
	11th to 20th	Night	12% 7% 2 5% 4 3 4 2 3 6% 51%	2749
	21st to end	Night	16% 9% 3 5% 4 3 3 3 4 5% 46%	2800
December	1st to 10th	Night	8% 6% 2 6% 4 4 4 3 5% 6% 52%	4580
	11th to 20th	Night	13% 9% 3 6% 4 3 4 3 6% 7% 43%	5199
	21st to end	Night	23% 15% 5% 9% 4 4 3 3 3 4 26%	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	52% 3 12% 22% 10% 1	3874
	11th to 20th	Day	48% 2 12% 19% 15% 4	4080
	21st to end	Day	57% 3 10% 16% 12% 2	4488
February	1st to 10th	Day	50% 4 14% 20% 10% 2	1800
	11th to 20th	Day	47% 3 12% 22% 14% 2	1763
	21st to end	Day	42% 4 12% 23% 18% 2	1657
March	1st to 10th	Day	40% 3 8% 25% 21% 3	4936
	11th to 20th	Day	34% 3 9% 25% 24% 4	4980
	21st to end	Day	52% 5% 16% 22% 4 1	5464
April	1st to 10th	Day	44% 4 12% 25% 14% 2	2375
	11th to 20th	Day	44% 5% 11% 25% 14% 1	2374
	21st to end	Day	50% 5% 11% 21% 11% 1	2475
May	1st to 10th	Day	41% 6% 13% 24% 15% 1	5900
	11th to 20th	Day	41% 4 13% 25% 15% 2	5975
	21st to end	Day	43% 5% 11% 24% 16% 1	6949
June	1st to 10th	Day	32% 8% 15% 29% 13% 2	2800
	11th to 20th	Day	33% 7% 13% 27% 18% 2	2800
	21st to end	Day	32% 6% 17% 28% 14% 3	2800
July	1st to 10th	Day	37% 5% 12% 29% 15% 2	6291
	11th to 20th	Day	37% 6% 13% 26% 17% 1	5885
	21st to end	Day	34% 7% 15% 32% 10% 1	6240
August	1st to 10th	Day	27% 5% 17% 32% 18% 1	4220
	11th to 20th	Day	36% 5% 13% 28% 16% 1	4210
	21st to end	Day	28% 6% 17% 31% 13% 6%	4321
September	1st to 10th	Day	32% 4 12% 27% 20% 6%	2400
	11th to 20th	Day	31% 6% 10% 30% 19% 3	2325
	21st to end	Day	31% 4 9% 31% 22% 3	2127
October	1st to 10th	Day	20% 2 7% 21% 44% 5%	3190
	11th to 20th	Day	24% 2 5% 22% 39% 9%	3140
	21st to end	Day	35% 4 9% 25% 25% 2	3428
November	1st to 10th	Day	33% 3 14% 27% 19% 4	1929
	11th to 20th	Day	39% 3 11% 26% 19% 2	1649
	21st to end	Day	45% 3 10% 27% 15%	1600
December	1st to 10th	Day	33% 3 17% 31% 16%	2610
	11th to 20th	Day	44% 3 15% 29% 9% 1	3005
	21st to end	Day	67% 3 12% 12% 5% 1	3982
January	1st to 10th	Night	56% 3 10% 21% 9% 1	6076
	11th to 20th	Night	49% 3 11% 20% 14% 3	5900
	21st to end	Night	53% 2 10% 17% 15% 3	6490
February	1st to 10th	Night	48% 4 12% 20% 13% 3	2600
	11th to 20th	Night	44% 5% 11% 23% 15% 3	2534
	21st to end	Night	39% 3 10% 24% 20% 4	1988
March	1st to 10th	Night	42% 3 7% 23% 22% 3	4919
	11th to 20th	Night	32% 2 7% 28% 25% 6%	4980
	21st to end	Night	50% 4 14% 22% 7% 2	5467
April	1st to 10th	Night	37% 4 10% 27% 18% 3	2025
	11th to 20th	Night	41% 3 9% 27% 16% 4	1975
	21st to end	Night	46% 3 11% 23% 15% 1	1920
May	1st to 10th	Night	40% 5% 13% 25% 15% 1	4080
	11th to 20th	Night	35% 5% 11% 28% 15% 4	3927
	21st to end	Night	40% 4 10% 24% 20% 1	3950
June	1st to 10th	Night	25% 6% 19% 32% 15% 3	1600
	11th to 20th	Night	28% 6% 12% 30% 19% 5%	1600
	21st to end	Night	24% 6% 16% 30% 20% 4	1600
July	1st to 10th	Night	32% 4 12% 27% 22% 3	3580
	11th to 20th	Night	30% 6% 16% 28% 18% 2	3954
	21st to end	Night	31% 6% 19% 32% 11% 1	4320
August	1st to 10th	Night	20% 6% 18% 32% 23% 1	2916
	11th to 20th	Night	32% 4 11% 29% 22% 1	2915
	21st to end	Night	24% 5% 16% 33% 17% 5%	3574
September	1st to 10th	Night	29% 5% 10% 26% 24% 7%	2000
	11th to 20th	Night	28% 4 12% 29% 23% 3	2070
	21st to end	Night	29% 4 8% 29% 26% 4	2251
October	1st to 10th	Night	18% 2 7% 18% 49% 5%	3837
	11th to 20th	Night	23% 2 6% 22% 35% 11%	3779
	21st to end	Night	36% 2 8% 27% 25% 3	4120
November	1st to 10th	Night	28% 4 14% 27% 22% 6%	2366
	11th to 20th	Night	36% 2 8% 29% 20% 4	2749
	21st to end	Night	41% 3 11% 27% 16% 2	2800
December	1st to 10th	Night	34% 3 12% 37% 13%	4580
	11th to 20th	Night	41% 4 15% 27% 13%	5201
	21st to end	Night	63% 3 11% 16% 5% 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% 14% 33% 24% 5%	300
	11th to 20th	Day	24% 18% 40% 17% 1	300
	21st to end	Day	15% 17% 45% 19% 2	330
February	1st to 10th	Day	24% 18% 39% 16% 3	300
	11th to 20th	Day	21% 20% 39% 13% 7%	300
	21st to end	Day	19% 20% 39% 17% 4	249
March	1st to 10th	Day	18% 17% 44% 18% 2	300
	11th to 20th	Day	25% 15% 33% 22% 4	300
	21st to end	Day	35% 18% 30% 14% 3	330
April	1st to 10th	Day	21% 17% 36% 20% 6%	475
	11th to 20th	Day	21% 16% 34% 22% 5% 2	492
	21st to end	Day	24% 18% 31% 21% 7%	575
May	1st to 10th	Day	20% 12% 34% 24% 9% 1	703
	11th to 20th	Day	19% 11% 27% 29% 11% 3	725
	21st to end	Day	16% 9% 28% 27% 17% 3	789
June	1st to 10th	Day	7% 5% 21% 35% 24% 8%	730
	11th to 20th	Day	9% 5% 24% 35% 21% 5%	730
	21st to end	Day	8% 5% 34% 32% 17% 3	730
July	1st to 10th	Day	9% 3 15% 30% 31% 12%	721
	11th to 20th	Day	8% 3 19% 36% 25% 9%	718
	21st to end	Day	7% 2 15% 35% 32% 7%	794
August	1st to 10th	Day	7% 2 18% 40% 26% 7%	726
	11th to 20th	Day	11% 3 14% 35% 30% 7%	715
	21st to end	Day	9% 3 14% 33% 31% 11%	593
September	1st to 10th	Day	13% 4 16% 32% 28% 8%	530
	11th to 20th	Day	9% 4 18% 34% 28% 8%	455
	21st to end	Day	12% 8% 22% 31% 18% 8%	330
October	1st to 10th	Day	15% 6% 29% 27% 15% 8%	309
	11th to 20th	Day	14% 22% 35% 19% 10% 1	300
	21st to end	Day	21% 18% 31% 23% 7% 1	330
November	1st to 10th	Day	17% 9% 38% 26% 6% 4	300
	11th to 20th	Day	19% 19% 32% 22% 5% 3	300
	21st to end	Day	24% 15% 30% 25% 5% 1	300
December	1st to 10th	Day	10% 17% 38% 24% 9% 2	300
	11th to 20th	Day	18% 19% 35% 22% 6% 1	300
	21st to end	Day	24% 21% 35% 18% 2	330
January	1st to 10th	Night	14% 14% 39% 26% 7%	1000
	11th to 20th	Night	17% 15% 39% 23% 6% 1	1000
	21st to end	Night	16% 12% 39% 29% 3	1100
February	1st to 10th	Night	18% 13% 40% 25% 4	1000
	11th to 20th	Night	18% 14% 37% 27% 4	979
	21st to end	Night	19% 14% 42% 20% 4 1	668
March	1st to 10th	Night	17% 14% 39% 25% 5%	600
	11th to 20th	Night	22% 12% 35% 27% 5% 1	600
	21st to end	Night	27% 10% 37% 22% 4	660
April	1st to 10th	Night	15% 12% 42% 27% 4	600
	11th to 20th	Night	20% 13% 33% 26% 7%	593
	21st to end	Night	20% 11% 34% 28% 6% 1	600
May	1st to 10th	Night	16% 9% 33% 33% 9% 1	600
	11th to 20th	Night	18% 7% 25% 35% 14% 1	591
	21st to end	Night	13% 6% 26% 36% 17% 2	650
June	1st to 10th	Night	7% 3 21% 43% 22% 3	600
	11th to 20th	Night	8% 3 25% 46% 17% 2	600
	21st to end	Night	6% 2 28% 47% 17%	600
July	1st to 10th	Night	8% 3 12% 39% 34% 4	585
	11th to 20th	Night	6% 2 15% 46% 29% 2	582
	21st to end	Night	8% 2 14% 42% 33% 2	657
August	1st to 10th	Night	4 2 17% 49% 27% 1	597
	11th to 20th	Night	8% 2 13% 41% 34% 3	594
	21st to end	Night	6% 1 12% 43% 34% 3	660
September	1st to 10th	Night	11% 2 17% 39% 27% 4	600
	11th to 20th	Night	11% 3 18% 40% 25% 4	600
	21st to end	Night	8% 4 25% 39% 21% 3	651
October	1st to 10th	Night	11% 5% 30% 33% 19% 2	773
	11th to 20th	Night	15% 9% 36% 30% 10% 1	760
	21st to end	Night	20% 11% 32% 27% 8%	836
November	1st to 10th	Night	11% 10% 33% 36% 10%	780
	11th to 20th	Night	16% 12% 39% 25% 8%	949
	21st to end	Night	21% 10% 36% 27% 6%	1000
December	1st to 10th	Night	17% 11% 38% 27% 6% 1	1000
	11th to 20th	Night	20% 9% 37% 29% 6%	1000
	21st to end	Night	24% 15% 33% 25% 3	1100

Page generated at 2025-10-01 00:39:01. Version ac07

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