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 2025-02-21.

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	16% 12% 4 9% 5% 4 4 3 5% 7% 30%	108927
	Night	17% 14% 5% 10% 5% 4 4 3 5% 6% 28%	109631
Transparency	Day	52% 5% 12% 19% 10% 1	112592
	Night	56% 5% 10% 18% 10% 1	114094
Seeing	Day	21% 11% 29% 23% 11% 4	15142
	Night	24% 11% 25% 26% 12% 2	24822

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% 5% 4 3 2 3 4 11%	4056
	11th to 20th	Day	14% 24% 7% 18% 8% 6% 4 2 3 4 10%	4060
	21st to end	Day	22% 19% 9% 15% 8% 5% 3 2 3 3 11%	4466
February	1st to 10th	Day	17% 19% 6% 12% 8% 4 4 3 4 5% 19%	1800
	11th to 20th	Day	15% 15% 7% 15% 9% 5% 4 2 3 5% 19%	1813
	21st to end	Day	19% 14% 4 12% 6% 5% 4 4 4 6% 22%	1570
March	1st to 10th	Day	21% 14% 5% 8% 4 3 4 3 4 6% 27%	3339
	11th to 20th	Day	13% 14% 5% 11% 5% 4 3 3 4 5% 33%	3480
	21st to end	Day	20% 13% 6% 10% 4 4 3 2 4 5% 28%	3815
April	1st to 10th	Day	15% 14% 3 7% 4 4 4 3 6% 8% 32%	2123
	11th to 20th	Day	19% 10% 2 6% 5% 4 4 4 5% 7% 34%	2427
	21st to end	Day	21% 11% 3 7% 4 4 4 3 4 6% 34%	2470
May	1st to 10th	Day	18% 10% 3 8% 5% 5% 5% 3 5% 6% 32%	4082
	11th to 20th	Day	18% 9% 3 6% 4 4 3 4 5% 8% 35%	4081
	21st to end	Day	10% 6% 3 6% 5% 5% 5% 4 7% 8% 41%	4534
June	1st to 10th	Day	14% 7% 2 5% 5% 5% 5% 4 6% 8% 38%	2660
	11th to 20th	Day	12% 5% 2 7% 5% 4 4 4 6% 9% 41%	2660
	21st to end	Day	12% 6% 2 5% 5% 4 5% 4 7% 9% 41%	2842
July	1st to 10th	Day	9% 5% 2 7% 5% 5% 4 4 6% 11% 41%	4262
	11th to 20th	Day	10% 5% 2 5% 3 4 5% 4 7% 10% 46%	4120
	21st to end	Day	10% 5% 2 7% 5% 5% 5% 4 6% 9% 41%	4466
August	1st to 10th	Day	13% 7% 2 7% 5% 5% 5% 4 6% 9% 38%	4104
	11th to 20th	Day	13% 6% 2 8% 4 4 5% 5% 7% 9% 37%	4044
	21st to end	Day	11% 5% 2 6% 4 5% 5% 4 7% 10% 41%	4474
September	1st to 10th	Day	15% 7% 2 6% 4 4 4 4 5% 8% 42%	2172
	11th to 20th	Day	12% 6% 3 5% 4 4 4 4 5% 9% 45%	2090
	21st to end	Day	19% 8% 3 6% 5% 3 4 3 5% 6% 37%	2090
October	1st to 10th	Day	15% 7% 3 7% 4 4 5% 5% 5% 7% 39%	1968
	11th to 20th	Day	21% 10% 3 8% 4 4 4 3 5% 6% 32%	1900
	21st to end	Day	24% 10% 3 8% 5% 4 4 4 5% 7% 26%	2069
November	1st to 10th	Day	14% 13% 4 8% 4 5% 4 4 5% 7% 33%	1762
	11th to 20th	Day	18% 21% 4 7% 4 3 5% 2 5% 5% 26%	1773
	21st to end	Day	20% 20% 6% 9% 5% 5% 4 4 5% 6% 15%	1600
December	1st to 10th	Day	18% 20% 9% 12% 6% 4 4 3 5% 5% 14%	2600
	11th to 20th	Day	22% 22% 7% 12% 6% 4 4 3 4 6% 10%	2990
	21st to end	Day	24% 21% 7% 16% 6% 4 4 3 4 4 8%	4165
January	1st to 10th	Night	15% 22% 10% 23% 5% 3 3 2 3 4 10%	5889
	11th to 20th	Night	11% 23% 11% 18% 8% 4 3 3 4 4 9%	5900
	21st to end	Night	22% 20% 7% 14% 5% 4 3 3 3 3 16%	6490
February	1st to 10th	Night	19% 18% 6% 13% 6% 4 4 3 4 4 19%	2600
	11th to 20th	Night	18% 16% 6% 12% 6% 5% 4 3 5% 5% 20%	2469
	21st to end	Night	20% 15% 6% 13% 5% 5% 4 3 5% 5% 22%	1885
March	1st to 10th	Night	22% 15% 4 6% 4 3 4 2 3 5% 32%	3513
	11th to 20th	Night	16% 14% 5% 7% 3 4 4 3 4 6% 33%	3480
	21st to end	Night	18% 13% 4 10% 4 4 3 3 5% 5% 32%	3817
April	1st to 10th	Night	18% 14% 4 7% 5% 3 4 4 5% 6% 31%	2057
	11th to 20th	Night	18% 10% 3 7% 5% 4 6% 3 6% 6% 34%	1719
	21st to end	Night	16% 10% 4 5% 4 4 3 4 6% 7% 36%	1710
May	1st to 10th	Night	22% 10% 3 7% 4 4 4 3 6% 7% 29%	2813
	11th to 20th	Night	16% 8% 3 6% 5% 4 5% 3 6% 8% 36%	2812
	21st to end	Night	13% 4 2 5% 4 4 5% 4 7% 9% 45%	3016
June	1st to 10th	Night	11% 8% 3 6% 4 5% 5% 4 6% 8% 41%	1520
	11th to 20th	Night	10% 6% 2 6% 6% 5% 6% 4 6% 9% 41%	1509
	21st to end	Night	10% 5% 2 7% 5% 4 5% 5% 7% 10% 41%	1332
July	1st to 10th	Night	10% 6% 2 6% 4 4 4 3 5% 8% 48%	2680
	11th to 20th	Night	11% 4 2 6% 3 4 4 3 6% 9% 48%	2840
	21st to end	Night	8% 6% 2 6% 5% 5% 5% 4 6% 9% 44%	3087
August	1st to 10th	Night	11% 6% 3 7% 4 4 5% 4 7% 9% 40%	2825
	11th to 20th	Night	14% 8% 2 7% 4 4 3 3 5% 7% 41%	2785
	21st to end	Night	9% 5% 3 7% 5% 4 6% 4 6% 8% 44%	3149
September	1st to 10th	Night	12% 6% 2 6% 4 5% 5% 4 6% 7% 43%	2004
	11th to 20th	Night	11% 6% 2 5% 4 4 4 3 5% 7% 50%	2090
	21st to end	Night	17% 8% 2 7% 5% 5% 4 3 5% 6% 37%	2090
October	1st to 10th	Night	15% 7% 2 6% 4 3 4 4 7% 6% 42%	2211
	11th to 20th	Night	23% 9% 3 7% 4 5% 4 3 5% 7% 32%	2280
	21st to end	Night	27% 11% 3 8% 4 4 3 3 5% 6% 27%	2527
November	1st to 10th	Night	18% 12% 3 7% 4 4 3 3 6% 7% 33%	2536
	11th to 20th	Night	19% 19% 4 9% 5% 4 3 3 4 4 24%	2625
	21st to end	Night	24% 19% 5% 8% 5% 4 4 3 4 6% 19%	2800
December	1st to 10th	Night	18% 20% 9% 12% 5% 4 4 4 5% 5% 14%	4580
	11th to 20th	Night	19% 25% 7% 11% 5% 4 3 2 4 5% 15%	5205
	21st to end	Night	22% 21% 6% 12% 6% 4 4 3 4 5% 11%	6786

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	79% 3 9% 6% 2	4057
	11th to 20th	Day	80% 4 9% 5% 2	4060
	21st to end	Day	79% 3 7% 9% 3	4466
February	1st to 10th	Day	67% 5% 10% 13% 5%	1800
	11th to 20th	Day	69% 4 8% 14% 5% 1	1822
	21st to end	Day	62% 5% 13% 13% 6% 1	1570
March	1st to 10th	Day	59% 3 10% 23% 5%	3339
	11th to 20th	Day	52% 5% 15% 20% 6% 1	3480
	21st to end	Day	58% 4 11% 16% 10% 1	3815
April	1st to 10th	Day	50% 4 13% 19% 13% 1	2123
	11th to 20th	Day	50% 4 12% 20% 13% 2	2427
	21st to end	Day	51% 4 11% 21% 10% 2	2470
May	1st to 10th	Day	52% 5% 9% 22% 10% 1	4120
	11th to 20th	Day	46% 7% 12% 24% 10% 2	4085
	21st to end	Day	39% 6% 13% 20% 15% 7%	4548
June	1st to 10th	Day	43% 6% 11% 26% 13% 1	2660
	11th to 20th	Day	39% 5% 16% 22% 14% 3	2660
	21st to end	Day	38% 5% 13% 25% 16% 3	2842
July	1st to 10th	Day	37% 6% 12% 26% 17% 3	4197
	11th to 20th	Day	32% 5% 13% 29% 19% 2	4051
	21st to end	Day	37% 6% 16% 20% 19% 1	4324
August	1st to 10th	Day	41% 6% 15% 26% 12%	4091
	11th to 20th	Day	41% 6% 12% 31% 8% 1	4083
	21st to end	Day	36% 7% 15% 29% 12% 1	4474
September	1st to 10th	Day	40% 5% 15% 22% 16% 3	2172
	11th to 20th	Day	36% 5% 15% 25% 17% 2	2090
	21st to end	Day	47% 4 11% 20% 16% 1	2090
October	1st to 10th	Day	34% 6% 13% 28% 18% 1	3267
	11th to 20th	Day	48% 5% 10% 19% 17% 1	3140
	21st to end	Day	44% 5% 13% 23% 15% 1	3383
November	1st to 10th	Day	50% 6% 10% 21% 12% 1	1762
	11th to 20th	Day	61% 5% 9% 15% 9% 2	1773
	21st to end	Day	70% 5% 8% 12% 5%	1600
December	1st to 10th	Day	71% 7% 12% 8% 2	2600
	11th to 20th	Day	76% 4 9% 9% 2	2986
	21st to end	Day	81% 4 7% 7% 1	4165
January	1st to 10th	Night	80% 4 6% 8% 3	5889
	11th to 20th	Night	81% 3 8% 6% 2	5900
	21st to end	Night	75% 3 9% 8% 5%	6490
February	1st to 10th	Night	69% 5% 9% 12% 4	2600
	11th to 20th	Night	67% 5% 7% 16% 5%	2471
	21st to end	Night	65% 4 9% 14% 7% 1	1885
March	1st to 10th	Night	56% 4 11% 21% 8%	3513
	11th to 20th	Night	49% 7% 15% 18% 10% 1	3480
	21st to end	Night	52% 6% 10% 22% 9% 1	3817
April	1st to 10th	Night	54% 4 10% 18% 12% 2	2057
	11th to 20th	Night	49% 4 12% 18% 14% 3	1719
	21st to end	Night	45% 5% 12% 21% 14% 3	1710
May	1st to 10th	Night	53% 5% 10% 19% 11% 3	2840
	11th to 20th	Night	45% 6% 10% 23% 13% 2	2813
	21st to end	Night	32% 8% 14% 25% 19% 3	3023
June	1st to 10th	Night	41% 6% 10% 25% 15% 3	1520
	11th to 20th	Night	39% 5% 15% 21% 18% 2	1509
	21st to end	Night	36% 7% 13% 27% 16% 2	1332
July	1st to 10th	Night	34% 5% 12% 24% 19% 6%	2636
	11th to 20th	Night	33% 4 13% 28% 19% 3	2786
	21st to end	Night	35% 7% 14% 19% 23% 2	2988
August	1st to 10th	Night	39% 7% 12% 27% 13% 2	2814
	11th to 20th	Night	42% 6% 11% 29% 12% 1	2812
	21st to end	Night	36% 7% 11% 29% 15% 2	3149
September	1st to 10th	Night	39% 7% 11% 25% 15% 4	2004
	11th to 20th	Night	33% 6% 12% 26% 20% 2	2090
	21st to end	Night	47% 5% 9% 21% 17% 1	2090
October	1st to 10th	Night	32% 5% 9% 30% 23% 1	3692
	11th to 20th	Night	49% 5% 8% 20% 17% 1	3779
	21st to end	Night	45% 4 10% 25% 16% 1	4151
November	1st to 10th	Night	50% 6% 10% 20% 12% 2	2536
	11th to 20th	Night	62% 6% 8% 14% 7% 2	2625
	21st to end	Night	68% 5% 9% 14% 4	2800
December	1st to 10th	Night	71% 7% 11% 9% 3	4580
	11th to 20th	Night	73% 4 10% 11% 2	5208
	21st to end	Night	76% 5% 9% 9% 1	6786

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% 23% 35% 9% 6% 1	300
	11th to 20th	Day	31% 22% 34% 9% 4	300
	21st to end	Day	26% 23% 32% 16% 3 1	330
February	1st to 10th	Day	26% 22% 38% 11% 3	300
	11th to 20th	Day	30% 24% 30% 15% 1	300
	21st to end	Day	26% 28% 36% 8% 2	225
March	1st to 10th	Day	27% 16% 30% 21% 4 1	398
	11th to 20th	Day	27% 17% 32% 19% 5% 1	460
	21st to end	Day	32% 16% 29% 19% 4	506
April	1st to 10th	Day	23% 18% 31% 22% 5% 1	460
	11th to 20th	Day	27% 14% 30% 18% 10% 2	452
	21st to end	Day	27% 13% 32% 19% 7% 2	460
May	1st to 10th	Day	28% 12% 29% 21% 8% 2	463
	11th to 20th	Day	22% 9% 29% 24% 12% 3	487
	21st to end	Day	14% 4 29% 29% 18% 6%	529
June	1st to 10th	Day	17% 5% 35% 27% 13% 4	490
	11th to 20th	Day	17% 4 27% 33% 14% 4	490
	21st to end	Day	14% 8% 32% 30% 15% 3	679
July	1st to 10th	Day	12% 2 27% 32% 19% 8%	575
	11th to 20th	Day	16% 3 25% 30% 20% 6%	484
	21st to end	Day	10% 3 28% 32% 20% 6%	532
August	1st to 10th	Day	13% 5% 22% 33% 19% 9%	486
	11th to 20th	Day	15% 4 25% 32% 17% 7%	479
	21st to end	Day	12% 4 24% 33% 18% 8%	539
September	1st to 10th	Day	18% 4 23% 28% 21% 6%	490
	11th to 20th	Day	14% 3 18% 32% 22% 11%	490
	21st to end	Day	24% 9% 27% 21% 13% 6%	490
October	1st to 10th	Day	16% 10% 24% 26% 18% 6%	490
	11th to 20th	Day	24% 15% 31% 21% 8% 2	490
	21st to end	Day	33% 12% 28% 21% 5%	518
November	1st to 10th	Day	21% 21% 29% 18% 8% 3	300
	11th to 20th	Day	32% 22% 28% 12% 6% 1	285
	21st to end	Day	32% 17% 37% 13% 2	200
December	1st to 10th	Day	26% 21% 34% 15% 4 1	200
	11th to 20th	Day	29% 24% 32% 14% 3	200
	21st to end	Day	32% 22% 31% 13% 2	265
January	1st to 10th	Night	32% 21% 29% 14% 4	800
	11th to 20th	Night	33% 18% 29% 16% 4	800
	21st to end	Night	31% 15% 29% 21% 4	880
February	1st to 10th	Night	31% 17% 28% 21% 3	800
	11th to 20th	Night	29% 16% 31% 22% 3	783
	21st to end	Night	28% 17% 33% 19% 2	629
March	1st to 10th	Night	25% 13% 32% 24% 6%	760
	11th to 20th	Night	24% 15% 30% 24% 7% 1	760
	21st to end	Night	26% 10% 28% 25% 9% 1	836
April	1st to 10th	Night	24% 12% 29% 29% 6% 1	760
	11th to 20th	Night	23% 9% 34% 22% 10% 1	595
	21st to end	Night	22% 8% 31% 30% 8% 1	570
May	1st to 10th	Night	23% 8% 23% 32% 12% 2	570
	11th to 20th	Night	21% 7% 22% 33% 15% 2	561
	21st to end	Night	14% 2 23% 34% 25% 3	579
June	1st to 10th	Night	13% 5% 26% 39% 16% 2	380
	11th to 20th	Night	12% 3 24% 42% 17% 1	380
	21st to end	Night	10% 6% 24% 38% 22% 1	382
July	1st to 10th	Night	12% 3 14% 38% 29% 4	555
	11th to 20th	Night	12% 4 19% 35% 25% 5%	552
	21st to end	Night	11% 3 17% 40% 28% 2	624
August	1st to 10th	Night	10% 4 14% 42% 25% 5%	567
	11th to 20th	Night	13% 3 13% 39% 27% 4	564
	21st to end	Night	13% 4 18% 33% 27% 5%	639
September	1st to 10th	Night	15% 6% 17% 33% 23% 6%	760
	11th to 20th	Night	13% 4 14% 33% 30% 6%	760
	21st to end	Night	20% 9% 23% 26% 18% 5%	760
October	1st to 10th	Night	21% 8% 22% 28% 18% 4	760
	11th to 20th	Night	28% 13% 27% 23% 9% 1	760
	21st to end	Night	34% 13% 25% 23% 5%	836
November	1st to 10th	Night	25% 13% 28% 24% 8% 1	780
	11th to 20th	Night	31% 19% 27% 17% 5% 1	800
	21st to end	Night	34% 17% 29% 16% 4	800
December	1st to 10th	Night	34% 18% 29% 15% 5%	800
	11th to 20th	Night	31% 22% 29% 15% 3	800
	21st to end	Night	34% 15% 31% 17% 2	880

Page generated at 2025-02-18 03:26:29. Version ac07

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