Cleveland
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cleveland clear sky chart from 2005-11-06 to 2026-06-16.

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	16% 11% 4 9% 5% 4 4 3 5% 7% 31%	137529
	Night	17% 13% 5% 10% 5% 4 4 3 5% 6% 29%	134468
Transparency	Day	52% 5% 11% 20% 11% 1	141150
	Night	55% 5% 10% 18% 11% 1	138908
Seeing	Day	22% 12% 29% 23% 11% 3	16904
	Night	24% 12% 26% 26% 12% 2	26487

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% 21% 7% 24% 5% 4 4 3 3 4 9%	5258
	11th to 20th	Day	12% 22% 8% 19% 9% 6% 4 2 3 4 11%	5280
	21st to end	Day	19% 17% 8% 16% 8% 7% 5% 3 3 3 11%	5780
February	1st to 10th	Day	16% 18% 6% 12% 8% 4 4 3 4 5% 20%	1890
	11th to 20th	Day	14% 16% 7% 15% 9% 5% 4 3 3 5% 19%	1906
	21st to end	Day	18% 15% 4 12% 6% 5% 4 4 4 6% 22%	1730
March	1st to 10th	Day	17% 14% 6% 11% 5% 4 4 3 4 6% 28%	4904
	11th to 20th	Day	12% 12% 4 11% 5% 4 4 3 4 5% 35%	5090
	21st to end	Day	20% 15% 6% 10% 4 4 3 2 4 5% 27%	5586
April	1st to 10th	Day	16% 14% 3 8% 4 4 4 3 6% 7% 31%	2347
	11th to 20th	Day	19% 10% 2 6% 5% 4 4 3 5% 7% 34%	2685
	21st to end	Day	20% 11% 3 7% 4 4 4 3 4 6% 34%	2730
May	1st to 10th	Day	19% 10% 3 8% 5% 5% 5% 3 5% 6% 31%	7616
	11th to 20th	Day	16% 9% 3 7% 4 4 4 4 5% 8% 35%	7626
	21st to end	Day	16% 8% 3 6% 5% 4 5% 4 6% 7% 38%	8505
June	1st to 10th	Day	14% 7% 2 5% 5% 5% 5% 4 6% 8% 40%	2940
	11th to 20th	Day	13% 6% 2 7% 5% 4 4 4 6% 9% 40%	2870
	21st to end	Day	11% 6% 2 6% 5% 4 5% 4 7% 9% 41%	2991
July	1st to 10th	Day	9% 5% 2 6% 4 4 4 4 6% 10% 44%	6112
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 7% 10% 41%	5900
	21st to end	Day	12% 5% 2 6% 4 5% 4 4 6% 9% 43%	6424
August	1st to 10th	Day	13% 6% 2 7% 4 5% 5% 4 6% 9% 39%	4234
	11th to 20th	Day	13% 6% 2 8% 4 4 5% 5% 7% 9% 37%	4174
	21st to end	Day	10% 5% 2 6% 4 5% 5% 4 7% 10% 41%	4615
September	1st to 10th	Day	15% 6% 2 6% 4 4 4 4 5% 8% 43%	2286
	11th to 20th	Day	11% 5% 3 5% 4 4 4 4 5% 9% 46%	2200
	21st to end	Day	19% 8% 3 6% 5% 4 4 4 5% 6% 37%	2200
October	1st to 10th	Day	15% 7% 2 7% 3 4 5% 4 5% 7% 41%	2071
	11th to 20th	Day	20% 10% 3 7% 4 4 4 3 5% 7% 33%	2000
	21st to end	Day	24% 10% 3 7% 5% 4 4 4 5% 7% 26%	2178
November	1st to 10th	Day	15% 13% 4 8% 4 5% 4 4 5% 7% 33%	1852
	11th to 20th	Day	18% 21% 4 7% 4 3 5% 2 5% 6% 25%	1861
	21st to end	Day	20% 21% 6% 9% 5% 5% 4 4 5% 6% 15%	1680
December	1st to 10th	Day	18% 20% 9% 12% 6% 4 4 3 5% 5% 14%	2680
	11th to 20th	Day	21% 22% 7% 13% 6% 4 3 3 4 6% 10%	3070
	21st to end	Day	24% 21% 7% 16% 6% 4 4 3 4 4 8%	4258
January	1st to 10th	Night	17% 21% 9% 23% 5% 4 3 2 3 3 9%	7635
	11th to 20th	Night	11% 21% 11% 18% 8% 5% 3 3 4 5% 11%	7680
	21st to end	Night	18% 18% 6% 13% 6% 5% 4 3 4 4 18%	8401
February	1st to 10th	Night	19% 18% 6% 12% 6% 4 4 3 4 4 20%	2730
	11th to 20th	Night	17% 16% 6% 12% 6% 5% 4 3 5% 5% 19%	2596
	21st to end	Night	19% 15% 6% 13% 5% 4 3 3 5% 5% 22%	2076
March	1st to 10th	Night	21% 14% 4 8% 4 3 3 2 3 5% 31%	5168
	11th to 20th	Night	13% 13% 4 6% 3 4 4 3 5% 7% 37%	5090
	21st to end	Night	17% 14% 4 10% 4 4 4 3 4 5% 31%	5588
April	1st to 10th	Night	19% 15% 4 7% 5% 3 5% 4 5% 6% 29%	2273
	11th to 20th	Night	17% 10% 3 7% 5% 4 5% 4 6% 6% 32%	1902
	21st to end	Night	15% 10% 4 6% 4 4 3 4 6% 7% 37%	1890
May	1st to 10th	Night	23% 10% 3 7% 5% 5% 5% 4 5% 6% 27%	5237
	11th to 20th	Night	17% 7% 3 6% 4 4 5% 4 5% 8% 38%	5234
	21st to end	Night	21% 6% 2 6% 4 4 4 4 5% 7% 37%	5642
June	1st to 10th	Night	10% 7% 3 6% 5% 5% 5% 4 6% 8% 42%	1680
	11th to 20th	Night	10% 5% 2 7% 6% 5% 6% 5% 6% 9% 40%	1628
	21st to end	Night	10% 5% 1 7% 5% 3 5% 5% 7% 10% 42%	1402
July	1st to 10th	Night	9% 5% 2 6% 4 4 5% 4 6% 9% 45%	3833
	11th to 20th	Night	12% 5% 2 6% 4 5% 4 4 6% 9% 44%	4057
	21st to end	Night	9% 5% 2 6% 4 4 4 4 5% 8% 47%	4427
August	1st to 10th	Night	10% 6% 3 7% 4 4 5% 4 7% 9% 41%	2915
	11th to 20th	Night	14% 8% 2 7% 4 4 3 3 5% 7% 41%	2875
	21st to end	Night	9% 5% 3 7% 5% 4 6% 4 6% 8% 43%	3249
September	1st to 10th	Night	11% 6% 2 6% 4 5% 5% 4 5% 7% 44%	2110
	11th to 20th	Night	11% 6% 2 5% 4 4 4 3 5% 7% 51%	2200
	21st to end	Night	17% 8% 3 7% 5% 5% 4 3 5% 6% 37%	2200
October	1st to 10th	Night	15% 7% 2 6% 4 3 4 4 6% 6% 43%	2328
	11th to 20th	Night	22% 9% 3 7% 4 5% 4 3 5% 6% 33%	2400
	21st to end	Night	27% 11% 3 8% 4 4 3 3 5% 6% 27%	2660
November	1st to 10th	Night	17% 12% 3 7% 4 4 3 3 5% 6% 34%	2666
	11th to 20th	Night	19% 19% 4 9% 5% 4 3 3 4 4 25%	2756
	21st to end	Night	24% 19% 5% 9% 5% 4 4 3 4 6% 19%	2940
December	1st to 10th	Night	18% 20% 9% 11% 5% 4 4 4 5% 5% 14%	4720
	11th to 20th	Night	19% 24% 7% 11% 5% 4 3 2 4 5% 16%	5345
	21st to end	Night	22% 21% 6% 12% 6% 4 4 3 4 5% 11%	6935

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% 4 9% 6% 2	5259
	11th to 20th	Day	79% 4 8% 6% 4	5280
	21st to end	Day	78% 4 6% 9% 3	5780
February	1st to 10th	Day	66% 5% 10% 14% 5%	1890
	11th to 20th	Day	69% 4 8% 14% 5% 1	1915
	21st to end	Day	62% 5% 13% 13% 6% 1	1730
March	1st to 10th	Day	57% 4 12% 20% 6%	4904
	11th to 20th	Day	50% 5% 15% 22% 7% 1	5090
	21st to end	Day	59% 4 9% 17% 10% 1	5586
April	1st to 10th	Day	51% 4 12% 19% 12% 1	2347
	11th to 20th	Day	50% 4 12% 20% 13% 2	2685
	21st to end	Day	50% 4 11% 22% 10% 2	2730
May	1st to 10th	Day	53% 5% 9% 20% 11% 2	7651
	11th to 20th	Day	46% 7% 11% 23% 12% 1	7630
	21st to end	Day	44% 5% 10% 19% 17% 5%	8520
June	1st to 10th	Day	42% 5% 11% 26% 14% 2	2940
	11th to 20th	Day	41% 6% 16% 21% 14% 3	2870
	21st to end	Day	37% 6% 14% 25% 16% 3	2991
July	1st to 10th	Day	34% 6% 11% 30% 18% 2	6047
	11th to 20th	Day	36% 7% 14% 27% 16% 1	5831
	21st to end	Day	36% 6% 13% 23% 21% 1	6240
August	1st to 10th	Day	40% 6% 15% 26% 12%	4221
	11th to 20th	Day	41% 6% 12% 31% 9% 1	4213
	21st to end	Day	36% 7% 14% 30% 12% 1	4615
September	1st to 10th	Day	39% 5% 14% 23% 16% 3	2286
	11th to 20th	Day	35% 5% 15% 27% 17% 2	2200
	21st to end	Day	47% 4 12% 20% 16% 1	2200
October	1st to 10th	Day	34% 6% 12% 28% 19% 1	3370
	11th to 20th	Day	47% 5% 10% 20% 17% 1	3240
	21st to end	Day	44% 5% 13% 22% 15% 1	3492
November	1st to 10th	Day	50% 6% 10% 21% 12% 1	1852
	11th to 20th	Day	61% 5% 9% 15% 8% 2	1861
	21st to end	Day	70% 5% 8% 12% 5%	1680
December	1st to 10th	Day	71% 7% 12% 8% 2	2680
	11th to 20th	Day	76% 4 9% 9% 2	3066
	21st to end	Day	81% 4 8% 6% 1	4258
January	1st to 10th	Night	81% 4 6% 8% 2	7636
	11th to 20th	Night	78% 3 8% 8% 3	7680
	21st to end	Night	70% 4 9% 12% 5%	8401
February	1st to 10th	Night	68% 5% 9% 13% 4	2730
	11th to 20th	Night	66% 5% 8% 15% 5%	2598
	21st to end	Night	65% 4 10% 14% 7% 1	2076
March	1st to 10th	Night	57% 4 12% 19% 9%	5168
	11th to 20th	Night	45% 5% 13% 25% 10% 1	5090
	21st to end	Night	54% 5% 9% 19% 12% 1	5588
April	1st to 10th	Night	56% 4 9% 17% 11% 2	2273
	11th to 20th	Night	50% 4 11% 18% 14% 2	1902
	21st to end	Night	45% 5% 12% 21% 14% 3	1890
May	1st to 10th	Night	56% 5% 9% 16% 11% 4	5264
	11th to 20th	Night	45% 6% 10% 24% 13% 1	5235
	21st to end	Night	45% 6% 11% 20% 16% 2	5651
June	1st to 10th	Night	40% 5% 10% 24% 17% 4	1680
	11th to 20th	Night	39% 5% 15% 21% 18% 2	1628
	21st to end	Night	36% 7% 12% 26% 16% 2	1402
July	1st to 10th	Night	35% 6% 13% 24% 18% 4	3791
	11th to 20th	Night	36% 5% 13% 27% 16% 3	4006
	21st to end	Night	34% 6% 12% 20% 26% 2	4297
August	1st to 10th	Night	38% 7% 13% 27% 13% 2	2904
	11th to 20th	Night	41% 6% 10% 29% 12% 1	2902
	21st to end	Night	37% 7% 12% 28% 15% 2	3249
September	1st to 10th	Night	38% 7% 11% 26% 15% 4	2110
	11th to 20th	Night	32% 6% 12% 27% 21% 2	2200
	21st to end	Night	47% 5% 9% 20% 17% 1	2200
October	1st to 10th	Night	32% 5% 8% 30% 24% 1	3809
	11th to 20th	Night	49% 5% 8% 20% 18% 1	3899
	21st to end	Night	45% 4 9% 24% 16% 1	4284
November	1st to 10th	Night	49% 6% 10% 20% 12% 2	2666
	11th to 20th	Night	62% 6% 8% 14% 7% 2	2756
	21st to end	Night	68% 5% 9% 14% 4	2940
December	1st to 10th	Night	70% 7% 11% 9% 3	4720
	11th to 20th	Night	72% 4 10% 11% 2	5348
	21st to end	Night	76% 5% 9% 9% 1	6935

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% 24% 35% 9% 5% 1	330
	11th to 20th	Day	33% 23% 32% 8% 3	330
	21st to end	Day	28% 23% 31% 15% 2 1	363
February	1st to 10th	Day	25% 22% 38% 13% 3	330
	11th to 20th	Day	30% 23% 30% 15% 2	330
	21st to end	Day	25% 28% 38% 8% 1	273
March	1st to 10th	Day	27% 18% 32% 19% 4 1	472
	11th to 20th	Day	28% 18% 31% 17% 5% 1	540
	21st to end	Day	32% 18% 29% 17% 3	594
April	1st to 10th	Day	26% 19% 29% 20% 5% 1	540
	11th to 20th	Day	27% 17% 28% 18% 9% 2	532
	21st to end	Day	27% 13% 33% 19% 7% 1	540
May	1st to 10th	Day	28% 13% 30% 19% 7% 2	543
	11th to 20th	Day	22% 11% 30% 24% 11% 3	567
	21st to end	Day	17% 6% 29% 27% 15% 5%	617
June	1st to 10th	Day	17% 6% 35% 26% 12% 3	570
	11th to 20th	Day	18% 5% 29% 30% 13% 4	550
	21st to end	Day	13% 7% 31% 31% 15% 3	729
July	1st to 10th	Day	12% 3 27% 33% 18% 8%	620
	11th to 20th	Day	17% 4 24% 30% 19% 6%	524
	21st to end	Day	10% 3 28% 32% 20% 7%	576
August	1st to 10th	Day	12% 5% 21% 34% 19% 8%	526
	11th to 20th	Day	14% 4 24% 32% 18% 7%	519
	21st to end	Day	11% 5% 26% 32% 18% 8%	583
September	1st to 10th	Day	17% 6% 23% 27% 21% 7%	530
	11th to 20th	Day	13% 2 18% 32% 23% 12%	530
	21st to end	Day	23% 9% 26% 22% 13% 6%	530
October	1st to 10th	Day	15% 9% 24% 27% 18% 6%	530
	11th to 20th	Day	23% 15% 32% 20% 8% 2	530
	21st to end	Day	33% 12% 29% 21% 5%	561
November	1st to 10th	Day	23% 21% 28% 17% 8% 3	330
	11th to 20th	Day	33% 23% 27% 11% 5% 1	313
	21st to end	Day	33% 17% 36% 13% 1	220
December	1st to 10th	Day	26% 20% 34% 15% 4 1	220
	11th to 20th	Day	30% 25% 30% 14% 2	220
	21st to end	Day	34% 22% 29% 13% 1	292
January	1st to 10th	Night	32% 21% 29% 15% 3	840
	11th to 20th	Night	33% 19% 29% 15% 4	840
	21st to end	Night	31% 16% 29% 21% 3	924
February	1st to 10th	Night	30% 16% 29% 21% 3	840
	11th to 20th	Night	28% 16% 31% 21% 3	823
	21st to end	Night	28% 17% 34% 18% 2	692
March	1st to 10th	Night	26% 14% 32% 23% 5%	840
	11th to 20th	Night	25% 15% 30% 22% 6% 1	840
	21st to end	Night	26% 12% 29% 24% 9% 1	924
April	1st to 10th	Night	27% 12% 29% 27% 6% 1	840
	11th to 20th	Night	23% 11% 33% 22% 9% 1	658
	21st to end	Night	22% 9% 32% 29% 8% 1	630
May	1st to 10th	Night	24% 8% 24% 31% 11% 2	630
	11th to 20th	Night	20% 8% 24% 32% 13% 2	621
	21st to end	Night	16% 3 22% 34% 22% 2	641
June	1st to 10th	Night	13% 5% 26% 39% 15% 1	420
	11th to 20th	Night	12% 4 25% 41% 17% 1	410
	21st to end	Night	10% 6% 24% 38% 22% 1	402
July	1st to 10th	Night	12% 3 15% 40% 27% 4	585
	11th to 20th	Night	12% 4 19% 35% 25% 5%	582
	21st to end	Night	11% 4 17% 39% 27% 2	657
August	1st to 10th	Night	10% 4 14% 43% 25% 5%	597
	11th to 20th	Night	13% 3 13% 39% 28% 4	594
	21st to end	Night	12% 4 18% 33% 27% 5%	673
September	1st to 10th	Night	15% 6% 17% 34% 23% 5%	800
	11th to 20th	Night	13% 4 14% 33% 32% 6%	800
	21st to end	Night	19% 9% 22% 26% 19% 5%	800
October	1st to 10th	Night	20% 7% 21% 29% 18% 4	800
	11th to 20th	Night	27% 13% 28% 23% 8% 1	800
	21st to end	Night	34% 13% 25% 23% 5%	880
November	1st to 10th	Night	25% 14% 28% 24% 8% 1	820
	11th to 20th	Night	32% 18% 27% 17% 5% 1	840
	21st to end	Night	35% 16% 29% 15% 4	840
December	1st to 10th	Night	33% 18% 29% 15% 4	840
	11th to 20th	Night	31% 23% 29% 15% 3	840
	21st to end	Night	34% 16% 31% 17% 2	924

Page generated at 2026-06-13 02:31:42. Version ac07

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