Cincinnati
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cincinnati clear sky chart from 2005-11-06 to 2024-01-15.

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	14% 8% 3 6% 6% 3 5% 5% 5% 7% 36%	75128
	Night	15% 9% 4 6% 5% 3 4 4 5% 7% 38%	74627
Transparency	Day	46% 5% 11% 22% 14% 2	74841
	Night	46% 4 11% 22% 14% 2	74434
Seeing	Day	19% 11% 27% 23% 14% 6%	14192
	Night	20% 9% 25% 29% 15% 2	24011

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	16% 13% 6% 9% 6% 3 4 4 4 6% 28%	1517
	11th to 20th	Day	19% 12% 6% 10% 7% 3 5% 4 4 6% 24%	1596
	21st to end	Day	16% 13% 6% 8% 8% 3 6% 3 5% 7% 25%	1782
February	1st to 10th	Day	19% 13% 5% 8% 5% 3 4 5% 4 6% 28%	1726
	11th to 20th	Day	17% 11% 4 10% 6% 3 5% 4 4 6% 30%	1748
	21st to end	Day	19% 12% 6% 9% 5% 2 4 3 4 6% 29%	1480
March	1st to 10th	Day	18% 9% 3 6% 6% 3 4 4 5% 7% 34%	1804
	11th to 20th	Day	19% 10% 4 6% 6% 3 4 4 5% 7% 31%	1980
	21st to end	Day	21% 10% 5% 6% 7% 3 5% 4 5% 6% 29%	2178
April	1st to 10th	Day	15% 8% 3 6% 5% 3 5% 5% 6% 7% 36%	2132
	11th to 20th	Day	17% 6% 4 6% 5% 3 5% 4 5% 7% 39%	2173
	21st to end	Day	19% 7% 3 6% 6% 3 5% 4 5% 7% 35%	2340
May	1st to 10th	Day	20% 7% 2 7% 6% 4 5% 5% 5% 7% 33%	2340
	11th to 20th	Day	19% 8% 3 6% 6% 3 5% 4 6% 7% 34%	2301
	21st to end	Day	9% 5% 3 7% 7% 4 7% 7% 8% 10% 34%	2531
June	1st to 10th	Day	12% 5% 2 6% 6% 3 5% 6% 6% 8% 40%	2346
	11th to 20th	Day	9% 4 2 5% 5% 3 6% 6% 6% 9% 43%	2520
	21st to end	Day	9% 5% 3 7% 7% 4 6% 6% 5% 10% 40%	2520
July	1st to 10th	Day	12% 5% 3 6% 6% 4 6% 5% 6% 9% 38%	2520
	11th to 20th	Day	8% 5% 2 6% 5% 4 6% 6% 7% 11% 40%	2444
	21st to end	Day	10% 4 3 5% 5% 4 7% 6% 7% 9% 40%	2547
August	1st to 10th	Day	8% 5% 2 5% 6% 4 5% 5% 8% 9% 43%	2327
	11th to 20th	Day	8% 6% 3 6% 6% 4 6% 5% 8% 11% 39%	2303
	21st to end	Day	8% 5% 2 5% 6% 4 5% 5% 7% 9% 46%	2381
September	1st to 10th	Day	13% 5% 2 5% 5% 3 4 5% 6% 7% 45%	2056
	11th to 20th	Day	8% 5% 2 5% 5% 3 4 5% 6% 9% 47%	1980
	21st to end	Day	14% 5% 2 4 5% 2 3 4 4 6% 50%	1980
October	1st to 10th	Day	11% 5% 2 5% 6% 3 4 4 5% 6% 48%	1980
	11th to 20th	Day	12% 7% 2 5% 6% 4 3 4 6% 7% 44%	1836
	21st to end	Day	20% 9% 2 6% 5% 2 4 3 5% 6% 38%	1836
November	1st to 10th	Day	9% 6% 3 5% 5% 3 4 3 4 6% 53%	1672
	11th to 20th	Day	14% 10% 4 8% 5% 2 4 4 5% 7% 37%	1710
	21st to end	Day	17% 10% 3 8% 5% 3 4 3 4 7% 36%	1710
December	1st to 10th	Day	21% 11% 6% 9% 8% 3 4 4 4 6% 25%	1710
	11th to 20th	Day	16% 13% 6% 8% 7% 4 4 4 5% 5% 29%	2153
	21st to end	Day	21% 19% 6% 8% 7% 3 4 4 4 5% 18%	2969
January	1st to 10th	Night	17% 13% 5% 10% 7% 4 5% 4 4 5% 26%	2648
	11th to 20th	Night	19% 15% 5% 10% 7% 3 5% 4 3 4 26%	2452
	21st to end	Night	17% 14% 6% 9% 6% 3 4 4 4 5% 29%	2574
February	1st to 10th	Night	21% 11% 5% 9% 5% 3 4 4 4 5% 27%	2232
	11th to 20th	Night	17% 10% 4 7% 7% 3 5% 5% 5% 6% 31%	2098
	21st to end	Night	22% 13% 4 7% 4 2 4 4 4 6% 29%	1776
March	1st to 10th	Night	17% 10% 3 5% 6% 3 4 4 5% 5% 38%	2155
	11th to 20th	Night	18% 9% 3 5% 5% 3 4 5% 5% 7% 36%	1980
	21st to end	Night	19% 8% 4 6% 6% 3 5% 5% 4 6% 34%	2178
April	1st to 10th	Night	13% 7% 3 5% 5% 3 6% 5% 6% 8% 38%	1841
	11th to 20th	Night	15% 7% 3 6% 4 2 5% 5% 6% 7% 40%	1734
	21st to end	Night	17% 7% 3 6% 5% 2 5% 3 5% 8% 37%	1620
May	1st to 10th	Night	18% 8% 3 6% 6% 3 5% 4 5% 7% 34%	1620
	11th to 20th	Night	16% 6% 3 6% 6% 4 5% 4 6% 8% 37%	1592
	21st to end	Night	7% 6% 3 4 5% 4 5% 6% 6% 11% 42%	1744
June	1st to 10th	Night	8% 5% 2 4 4 3 4 5% 5% 9% 49%	1608
	11th to 20th	Night	8% 5% 2 5% 4 3 4 5% 5% 12% 48%	1440
	21st to end	Night	6% 4 2 5% 5% 4 4 5% 7% 10% 48%	1440
July	1st to 10th	Night	10% 5% 3 5% 5% 3 4 4 6% 8% 46%	1440
	11th to 20th	Night	7% 4 2 4 4 3 5% 5% 7% 10% 49%	1512
	21st to end	Night	8% 5% 3 5% 4 4 4 4 6% 10% 48%	1771
August	1st to 10th	Night	6% 4 2 6% 5% 3 4 6% 6% 11% 48%	1611
	11th to 20th	Night	6% 4 3 5% 5% 3 5% 5% 7% 10% 46%	1598
	21st to end	Night	6% 4 1 5% 4 2 4 4 6% 9% 56%	1971
September	1st to 10th	Night	12% 5% 2 3 4 2 4 4 5% 7% 51%	1885
	11th to 20th	Night	8% 4 2 4 4 3 4 4 5% 7% 54%	1980
	21st to end	Night	14% 5% 3 5% 5% 2 4 4 4 5% 51%	1980
October	1st to 10th	Night	8% 3 2 5% 4 4 4 4 4 7% 54%	1980
	11th to 20th	Night	15% 6% 2 5% 4 3 4 4 5% 7% 44%	2123
	21st to end	Night	18% 8% 3 5% 5% 3 4 4 4 5% 41%	2517
November	1st to 10th	Night	12% 6% 3 5% 4 3 4 4 5% 6% 48%	2406
	11th to 20th	Night	16% 8% 3 6% 6% 3 4 4 5% 6% 40%	2470
	21st to end	Night	19% 10% 3 6% 6% 3 4 4 4 6% 34%	2470
December	1st to 10th	Night	20% 12% 5% 9% 5% 3 4 4 4 6% 29%	2470
	11th to 20th	Night	18% 12% 6% 7% 5% 3 4 4 4 6% 30%	3042
	21st to end	Night	20% 18% 6% 10% 7% 4 4 4 4 5% 17%	4669

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	58% 4 8% 17% 11%	1518
	11th to 20th	Day	62% 4 10% 16% 7%	1596
	21st to end	Day	60% 3 11% 19% 6% 1	1782
February	1st to 10th	Day	59% 4 9% 17% 9% 2	1726
	11th to 20th	Day	57% 4 9% 20% 10% 1	1758
	21st to end	Day	57% 3 8% 20% 9% 2	1480
March	1st to 10th	Day	51% 4 10% 23% 11% 1	1804
	11th to 20th	Day	54% 4 11% 19% 11% 2	1980
	21st to end	Day	56% 4 10% 21% 7% 1	2178
April	1st to 10th	Day	46% 5% 11% 23% 13% 1	2132
	11th to 20th	Day	46% 4 9% 22% 16% 3	2173
	21st to end	Day	50% 4 9% 23% 12% 2	2340
May	1st to 10th	Day	51% 5% 11% 21% 10% 1	2340
	11th to 20th	Day	50% 5% 12% 19% 13% 1	2305
	21st to end	Day	42% 7% 15% 22% 12% 1	2531
June	1st to 10th	Day	39% 6% 11% 25% 16% 2	2346
	11th to 20th	Day	36% 5% 14% 24% 18% 2	2520
	21st to end	Day	39% 6% 14% 22% 14% 4	2520
July	1st to 10th	Day	42% 5% 13% 19% 18% 2	2451
	11th to 20th	Day	35% 7% 13% 26% 18% 2	2369
	21st to end	Day	37% 6% 15% 23% 15% 3	2405
August	1st to 10th	Day	35% 6% 15% 28% 14% 2	2314
	11th to 20th	Day	38% 5% 13% 27% 16% 1	2303
	21st to end	Day	33% 6% 13% 25% 17% 6%	2381
September	1st to 10th	Day	36% 4 11% 25% 18% 6%	2056
	11th to 20th	Day	33% 4 11% 28% 21% 2	1980
	21st to end	Day	36% 4 10% 26% 22% 2	1980
October	1st to 10th	Day	37% 5% 9% 24% 22% 3	1980
	11th to 20th	Day	39% 4 8% 26% 20% 3	1836
	21st to end	Day	49% 2 10% 22% 15% 1	1836
November	1st to 10th	Day	35% 3 8% 30% 21% 3	1672
	11th to 20th	Day	47% 3 7% 23% 16% 3	1710
	21st to end	Day	50% 3 9% 23% 14% 1	1710
December	1st to 10th	Day	62% 3 9% 19% 6%	1710
	11th to 20th	Day	57% 4 7% 20% 11% 1	2150
	21st to end	Day	69% 5% 8% 11% 6% 1	2969
January	1st to 10th	Night	62% 4 6% 18% 9%	2648
	11th to 20th	Night	64% 3 9% 18% 6% 1	2452
	21st to end	Night	59% 3 8% 20% 8% 1	2574
February	1st to 10th	Night	61% 2 11% 19% 6% 1	2232
	11th to 20th	Night	54% 4 10% 20% 10% 1	2099
	21st to end	Night	58% 3 11% 18% 9% 2	1776
March	1st to 10th	Night	49% 3 7% 24% 15% 2	2155
	11th to 20th	Night	49% 4 12% 22% 12% 2	1980
	21st to end	Night	52% 4 10% 23% 9% 2	2178
April	1st to 10th	Night	44% 5% 10% 26% 13% 2	1841
	11th to 20th	Night	41% 4 10% 18% 20% 6%	1734
	21st to end	Night	46% 4 11% 22% 14% 4	1620
May	1st to 10th	Night	50% 6% 11% 21% 10% 3	1620
	11th to 20th	Night	45% 6% 13% 20% 13% 2	1593
	21st to end	Night	34% 7% 17% 24% 15% 3	1745
June	1st to 10th	Night	32% 6% 11% 27% 21% 3	1608
	11th to 20th	Night	31% 6% 14% 24% 20% 4	1440
	21st to end	Night	30% 6% 17% 23% 18% 5%	1440
July	1st to 10th	Night	36% 6% 14% 21% 18% 5%	1400
	11th to 20th	Night	29% 6% 14% 29% 19% 3	1464
	21st to end	Night	32% 6% 12% 31% 17% 2	1672
August	1st to 10th	Night	30% 6% 14% 31% 15% 3	1600
	11th to 20th	Night	32% 6% 13% 30% 17% 1	1598
	21st to end	Night	25% 6% 17% 26% 21% 5%	1971
September	1st to 10th	Night	34% 4 12% 25% 18% 7%	1885
	11th to 20th	Night	28% 5% 10% 27% 27% 3	1980
	21st to end	Night	36% 3 8% 24% 26% 3	1980
October	1st to 10th	Night	31% 4 10% 28% 24% 4	1980
	11th to 20th	Night	41% 4 6% 25% 22% 2	2123
	21st to end	Night	46% 3 9% 22% 17% 3	2517
November	1st to 10th	Night	38% 3 10% 22% 23% 4	2406
	11th to 20th	Night	45% 3 8% 22% 19% 3	2470
	21st to end	Night	52% 3 10% 22% 12% 1	2470
December	1st to 10th	Night	57% 3 10% 20% 9% 1	2470
	11th to 20th	Night	56% 3 9% 21% 10% 1	3044
	21st to end	Night	69% 4 8% 13% 5%	4669

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% 19% 35% 16% 4 1	270
	11th to 20th	Day	30% 19% 33% 13% 4	252
	21st to end	Day	28% 22% 32% 15% 4	264
February	1st to 10th	Day	31% 24% 28% 15% 2	240
	11th to 20th	Day	31% 25% 33% 12%	240
	21st to end	Day	33% 15% 44% 7% 2	198
March	1st to 10th	Day	23% 31% 32% 13% 1	244
	11th to 20th	Day	27% 17% 32% 18% 6%	420
	21st to end	Day	31% 16% 30% 17% 5%	462
April	1st to 10th	Day	20% 18% 31% 20% 10% 1	420
	11th to 20th	Day	24% 18% 25% 20% 10% 4	412
	21st to end	Day	25% 15% 35% 14% 9% 2	420
May	1st to 10th	Day	25% 13% 32% 17% 8% 4	423
	11th to 20th	Day	21% 10% 30% 23% 11% 5%	447
	21st to end	Day	14% 6% 27% 27% 18% 9%	485
June	1st to 10th	Day	15% 5% 23% 31% 19% 7%	456
	11th to 20th	Day	13% 7% 27% 30% 18% 6%	630
	21st to end	Day	11% 7% 28% 29% 17% 8%	630
July	1st to 10th	Day	13% 2 18% 27% 24% 16%	621
	11th to 20th	Day	11% 4 23% 30% 21% 11%	542
	21st to end	Day	14% 1 17% 32% 23% 14%	488
August	1st to 10th	Day	11% 3 15% 29% 26% 16%	446
	11th to 20th	Day	13% 3 18% 32% 20% 14%	439
	21st to end	Day	11% 4 16% 28% 28% 13%	495
September	1st to 10th	Day	13% 2 17% 28% 29% 10%	450
	11th to 20th	Day	11% 3 14% 27% 31% 14%	450
	21st to end	Day	18% 7% 19% 26% 23% 7%	450
October	1st to 10th	Day	12% 7% 24% 30% 20% 7%	450
	11th to 20th	Day	17% 14% 32% 24% 10% 3	450
	21st to end	Day	25% 11% 37% 22% 4 1	351
November	1st to 10th	Day	12% 17% 36% 23% 10% 3	270
	11th to 20th	Day	23% 20% 26% 21% 8% 1	270
	21st to end	Day	26% 14% 39% 16% 5%	270
December	1st to 10th	Day	23% 20% 35% 15% 7% 1	270
	11th to 20th	Day	22% 18% 38% 16% 7%	270
	21st to end	Day	33% 14% 33% 15% 3 1	297
January	1st to 10th	Night	23% 17% 30% 25% 6%	950
	11th to 20th	Night	29% 15% 30% 22% 4	792
	21st to end	Night	24% 15% 31% 26% 3	792
February	1st to 10th	Night	30% 11% 30% 26% 3	720
	11th to 20th	Night	24% 18% 32% 24% 2	703
	21st to end	Night	31% 13% 31% 24% 2	592
March	1st to 10th	Night	22% 14% 33% 25% 6%	720
	11th to 20th	Night	25% 13% 31% 24% 7% 1	720
	21st to end	Night	25% 12% 29% 27% 8%	792
April	1st to 10th	Night	18% 14% 32% 27% 9%	581
	11th to 20th	Night	20% 9% 31% 28% 11% 1	533
	21st to end	Night	20% 8% 37% 26% 9%	540
May	1st to 10th	Night	23% 7% 30% 27% 11% 1	540
	11th to 20th	Night	18% 5% 26% 32% 17% 2	531
	21st to end	Night	10% 2 22% 35% 26% 4	584
June	1st to 10th	Night	11% 3 18% 44% 22% 2	540
	11th to 20th	Night	11% 3 18% 42% 23% 4	540
	21st to end	Night	6% 2 24% 38% 26% 3	540
July	1st to 10th	Night	14% 1 11% 32% 33% 8%	525
	11th to 20th	Night	10% 1 15% 36% 33% 5%	522
	21st to end	Night	12% 1 13% 41% 30% 4	591
August	1st to 10th	Night	10% 1 11% 37% 39% 3	537
	11th to 20th	Night	9% 1 11% 42% 31% 5%	534
	21st to end	Night	7% 1 14% 32% 40% 6%	594
September	1st to 10th	Night	14% 2 14% 30% 36% 4	625
	11th to 20th	Night	10% 3 14% 33% 35% 5%	720
	21st to end	Night	16% 5% 20% 31% 25% 3	720
October	1st to 10th	Night	11% 4 23% 34% 23% 5%	720
	11th to 20th	Night	20% 9% 25% 29% 15% 1	720
	21st to end	Night	24% 9% 30% 27% 10% 1	792
November	1st to 10th	Night	18% 9% 28% 27% 17% 1	740
	11th to 20th	Night	22% 13% 27% 26% 10% 1	760
	21st to end	Night	25% 11% 26% 29% 9% 1	760
December	1st to 10th	Night	27% 12% 29% 25% 6%	760
	11th to 20th	Night	24% 11% 32% 27% 6% 1	760
	21st to end	Night	31% 13% 28% 24% 4	921

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