Wheeling
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wheeling clear sky chart from 2005-11-06 to 2025-09-19.

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	15% 10% 4 9% 5% 5% 5% 4 6% 7% 32%	125737
	Night	16% 11% 4 9% 5% 4 4 3 5% 6% 32%	123294
Transparency	Day	33% 38% 6% 14% 8% 1	129356
	Night	34% 38% 6% 13% 7% 1	127744
Seeing	Day	23% 14% 27% 20% 11% 4	15873
	Night	22% 11% 25% 27% 13% 2	25717

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	17% 18% 7% 21% 5% 4 3 2 3 4 17%	4056
	11th to 20th	Day	13% 22% 9% 13% 9% 5% 3 2 3 3 17%	4060
	21st to end	Day	19% 20% 6% 11% 8% 5% 4 3 3 4 17%	4466
February	1st to 10th	Day	21% 16% 5% 9% 6% 4 4 3 4 4 24%	1800
	11th to 20th	Day	17% 15% 6% 13% 4 4 3 3 5% 6% 24%	1782
	21st to end	Day	20% 13% 5% 9% 5% 3 3 3 4 6% 28%	1651
March	1st to 10th	Day	16% 16% 4 9% 5% 4 4 3 4 6% 30%	4935
	11th to 20th	Day	13% 7% 3 8% 5% 4 5% 3 6% 6% 39%	4980
	21st to end	Day	19% 8% 3 8% 5% 4 5% 4 6% 6% 30%	5465
April	1st to 10th	Day	16% 13% 3 8% 6% 4 4 4 6% 6% 30%	2267
	11th to 20th	Day	15% 10% 3 8% 6% 5% 5% 3 5% 6% 36%	2447
	21st to end	Day	19% 9% 3 8% 4 5% 5% 4 4 7% 33%	2600
May	1st to 10th	Day	19% 9% 3 8% 5% 5% 5% 4 6% 6% 27%	5862
	11th to 20th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 8% 29%	5861
	21st to end	Day	18% 7% 3 7% 4 5% 6% 4 7% 8% 31%	6473
June	1st to 10th	Day	12% 6% 2 6% 5% 5% 5% 5% 6% 10% 37%	2800
	11th to 20th	Day	13% 7% 3 7% 5% 5% 5% 5% 7% 9% 35%	2800
	21st to end	Day	13% 5% 3 6% 5% 5% 5% 5% 7% 9% 37%	2758
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 4 6% 9% 42%	5900
	11th to 20th	Day	11% 7% 3 7% 6% 6% 6% 4 7% 9% 33%	5900
	21st to end	Day	11% 7% 3 8% 6% 5% 6% 4 6% 8% 36%	6424
August	1st to 10th	Day	12% 7% 3 8% 5% 6% 6% 5% 7% 10% 33%	4234
	11th to 20th	Day	11% 6% 2 7% 5% 6% 6% 5% 8% 8% 37%	4174
	21st to end	Day	7% 3 2 6% 5% 7% 6% 5% 7% 10% 42%	4492
September	1st to 10th	Day	15% 6% 2 5% 3 3 3 3 5% 7% 47%	2343
	11th to 20th	Day	10% 5% 2 6% 3 3 5% 4 5% 9% 47%	2178
	21st to end	Day	18% 9% 3 7% 4 4 4 4 4 6% 36%	2090
October	1st to 10th	Day	14% 6% 3 7% 4 4 4 4 6% 7% 41%	1932
	11th to 20th	Day	17% 8% 2 7% 5% 4 4 4 5% 5% 39%	1900
	21st to end	Day	21% 10% 2 7% 3 4 4 2 4 7% 35%	2090
November	1st to 10th	Day	11% 9% 3 6% 4 5% 4 4 5% 6% 45%	1848
	11th to 20th	Day	16% 16% 4 5% 4 4 5% 3 5% 6% 32%	1767
	21st to end	Day	18% 15% 5% 9% 4 5% 4 4 5% 5% 28%	1600
December	1st to 10th	Day	18% 12% 5% 16% 5% 5% 4 2 4 5% 23%	2600
	11th to 20th	Day	23% 17% 6% 11% 4 3 3 3 4 5% 23%	2990
	21st to end	Day	22% 19% 6% 11% 6% 5% 4 3 4 5% 16%	4212
January	1st to 10th	Night	15% 18% 8% 20% 6% 4 3 3 3 4 16%	5889
	11th to 20th	Night	16% 18% 8% 14% 8% 6% 5% 3 4 3 16%	5900
	21st to end	Night	22% 16% 5% 12% 6% 3 3 2 3 4 24%	6490
February	1st to 10th	Night	20% 15% 5% 10% 5% 4 4 3 4 5% 27%	2600
	11th to 20th	Night	20% 14% 4 10% 5% 5% 4 4 5% 5% 24%	2502
	21st to end	Night	19% 16% 4 10% 5% 4 4 3 4 5% 25%	1977
March	1st to 10th	Night	20% 13% 4 8% 4 3 3 2 3 6% 33%	4918
	11th to 20th	Night	12% 9% 4 7% 4 4 4 4 5% 7% 41%	4980
	21st to end	Night	16% 10% 3 8% 6% 4 4 3 5% 6% 35%	5467
April	1st to 10th	Night	20% 12% 3 7% 5% 4 4 3 5% 6% 32%	2132
	11th to 20th	Night	16% 10% 2 6% 5% 5% 5% 3 6% 7% 36%	1917
	21st to end	Night	16% 9% 3 7% 4 3 5% 3 5% 7% 39%	1800
May	1st to 10th	Night	25% 12% 3 8% 5% 4 4 3 5% 6% 25%	4033
	11th to 20th	Night	16% 9% 3 7% 4 4 4 3 6% 9% 35%	4032
	21st to end	Night	18% 8% 3 7% 5% 4 5% 4 6% 9% 33%	4360
June	1st to 10th	Night	9% 7% 2 6% 5% 4 4 4 6% 8% 45%	1600
	11th to 20th	Night	11% 7% 2 6% 4 5% 5% 4 8% 11% 39%	1600
	21st to end	Night	10% 5% 2 6% 5% 4 5% 5% 6% 9% 44%	1634
July	1st to 10th	Night	12% 6% 3 7% 5% 4 4 3 6% 8% 42%	4058
	11th to 20th	Night	12% 7% 2 7% 4 5% 6% 4 6% 9% 37%	4057
	21st to end	Night	9% 7% 3 7% 4 4 5% 4 6% 9% 42%	4427
August	1st to 10th	Night	10% 8% 3 8% 5% 6% 5% 4 7% 10% 35%	2915
	11th to 20th	Night	11% 7% 3 7% 4 4 5% 4 6% 7% 42%	2875
	21st to end	Night	6% 4 2 6% 5% 5% 5% 4 7% 9% 46%	3373
September	1st to 10th	Night	13% 4 2 4 4 4 4 3 5% 7% 50%	2053
	11th to 20th	Night	9% 5% 2 5% 3 4 3 3 5% 8% 54%	2179
	21st to end	Night	16% 7% 2 6% 5% 4 5% 3 4 5% 43%	2090
October	1st to 10th	Night	14% 5% 2 6% 4 4 4 3 6% 6% 45%	2247
	11th to 20th	Night	16% 7% 3 7% 4 4 4 3 5% 7% 40%	2280
	21st to end	Night	22% 8% 3 6% 4 3 3 3 5% 6% 38%	2508
November	1st to 10th	Night	13% 8% 2 5% 4 3 4 3 4 7% 48%	2448
	11th to 20th	Night	17% 12% 3 7% 4 4 5% 3 5% 6% 33%	2630
	21st to end	Night	19% 14% 3 7% 5% 5% 4 4 4 5% 30%	2800
December	1st to 10th	Night	18% 14% 7% 15% 5% 4 4 3 4 5% 21%	4580
	11th to 20th	Night	20% 18% 6% 10% 5% 4 3 3 4 5% 23%	5205
	21st to end	Night	21% 18% 5% 11% 5% 4 4 3 4 5% 18%	6738

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	56% 26% 6% 7% 3	4057
	11th to 20th	Day	58% 26% 3 6% 5% 2	4060
	21st to end	Day	54% 27% 4 8% 6%	4466
February	1st to 10th	Day	26% 62% 3 6% 3	1800
	11th to 20th	Day	24% 60% 3 9% 3	1791
	21st to end	Day	20% 61% 5% 7% 6% 1	1651
March	1st to 10th	Day	44% 28% 5% 17% 5% 1	4935
	11th to 20th	Day	32% 29% 6% 24% 7% 2	4980
	21st to end	Day	39% 28% 5% 17% 11% 1	5465
April	1st to 10th	Day	23% 62% 3 8% 4 1	2267
	11th to 20th	Day	18% 62% 5% 8% 5% 1	2447
	21st to end	Day	20% 62% 4 9% 5%	2600
May	1st to 10th	Day	41% 30% 7% 14% 6% 3	5897
	11th to 20th	Day	38% 30% 7% 18% 7%	5865
	21st to end	Day	38% 30% 8% 15% 8% 2	6488
June	1st to 10th	Day	18% 63% 4 9% 6%	2800
	11th to 20th	Day	19% 63% 4 9% 5%	2800
	21st to end	Day	16% 62% 6% 10% 6%	2758
July	1st to 10th	Day	30% 28% 7% 21% 13% 1	5835
	11th to 20th	Day	34% 29% 9% 19% 8%	5831
	21st to end	Day	33% 27% 7% 16% 16% 1	6240
August	1st to 10th	Day	30% 38% 9% 16% 7%	4221
	11th to 20th	Day	26% 38% 6% 21% 9%	4213
	21st to end	Day	22% 38% 9% 20% 11%	4492
September	1st to 10th	Day	15% 58% 5% 10% 10% 1	2343
	11th to 20th	Day	13% 58% 6% 12% 10% 1	2178
	21st to end	Day	20% 60% 4 10% 6%	2090
October	1st to 10th	Day	16% 37% 5% 25% 16% 2	3205
	11th to 20th	Day	26% 37% 7% 13% 12% 4	3140
	21st to end	Day	19% 37% 9% 19% 15% 1	3428
November	1st to 10th	Day	21% 56% 5% 11% 6% 1	1848
	11th to 20th	Day	21% 58% 3 11% 7% 1	1767
	21st to end	Day	28% 58% 5% 8% 2	1600
December	1st to 10th	Day	41% 37% 11% 8% 3	2600
	11th to 20th	Day	46% 31% 7% 12% 3	2986
	21st to end	Day	55% 27% 6% 9% 3	4212
January	1st to 10th	Night	58% 26% 4 9% 3	5889
	11th to 20th	Night	57% 26% 6% 7% 4 1	5900
	21st to end	Night	50% 27% 7% 10% 5% 2	6490
February	1st to 10th	Night	24% 62% 3 8% 3	2600
	11th to 20th	Night	24% 61% 3 9% 3	2504
	21st to end	Night	24% 62% 4 6% 5%	1977
March	1st to 10th	Night	42% 28% 5% 16% 7% 1	4918
	11th to 20th	Night	30% 28% 8% 24% 7% 3	4980
	21st to end	Night	36% 29% 7% 16% 11% 1	5467
April	1st to 10th	Night	24% 63% 2 8% 3	2132
	11th to 20th	Night	18% 63% 5% 8% 5% 1	1917
	21st to end	Night	17% 62% 4 9% 7%	1800
May	1st to 10th	Night	47% 30% 7% 9% 5% 3	4060
	11th to 20th	Night	34% 31% 6% 22% 6%	4033
	21st to end	Night	38% 30% 7% 17% 5% 2	4367
June	1st to 10th	Night	15% 63% 4 10% 7% 1	1600
	11th to 20th	Night	17% 63% 5% 8% 7% 1	1600
	21st to end	Night	16% 61% 5% 10% 7%	1634
July	1st to 10th	Night	32% 27% 6% 19% 13% 2	4015
	11th to 20th	Night	35% 29% 13% 17% 6%	4006
	21st to end	Night	30% 28% 8% 15% 18% 2	4297
August	1st to 10th	Night	32% 38% 9% 15% 5%	2904
	11th to 20th	Night	29% 37% 5% 17% 12%	2902
	21st to end	Night	21% 37% 9% 23% 9%	3373
September	1st to 10th	Night	14% 58% 6% 11% 10% 2	2053
	11th to 20th	Night	13% 58% 6% 11% 13% 1	2179
	21st to end	Night	18% 59% 4 9% 8% 1	2090
October	1st to 10th	Night	20% 36% 4 20% 18% 2	3754
	11th to 20th	Night	21% 38% 6% 15% 12% 8%	3779
	21st to end	Night	17% 36% 5% 20% 19% 2	4120
November	1st to 10th	Night	21% 56% 6% 10% 6% 1	2448
	11th to 20th	Night	23% 56% 3 10% 8% 1	2630
	21st to end	Night	27% 57% 6% 8% 2	2800
December	1st to 10th	Night	45% 35% 6% 11% 2	4580
	11th to 20th	Night	47% 31% 10% 10% 2	5208
	21st to end	Night	53% 27% 6% 11% 4	6738

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	36% 24% 27% 9% 4 1	300
	11th to 20th	Day	39% 24% 28% 8% 1	300
	21st to end	Day	34% 30% 28% 6% 3	330
February	1st to 10th	Day	40% 22% 29% 9%	300
	11th to 20th	Day	40% 28% 25% 6% 1	300
	21st to end	Day	36% 27% 32% 4	250
March	1st to 10th	Day	32% 21% 29% 16% 3	500
	11th to 20th	Day	32% 19% 30% 13% 4 1	500
	21st to end	Day	31% 21% 30% 15% 3	550
April	1st to 10th	Day	31% 16% 29% 17% 6% 1	500
	11th to 20th	Day	24% 23% 28% 15% 8% 3	492
	21st to end	Day	28% 18% 33% 13% 7% 2	500
May	1st to 10th	Day	27% 21% 28% 14% 9% 2	503
	11th to 20th	Day	23% 14% 31% 18% 9% 5%	527
	21st to end	Day	18% 11% 27% 24% 15% 5%	573
June	1st to 10th	Day	17% 10% 26% 30% 14% 3	530
	11th to 20th	Day	17% 11% 24% 29% 13% 5%	530
	21st to end	Day	13% 10% 30% 27% 16% 5%	530
July	1st to 10th	Day	16% 7% 19% 27% 21% 10%	525
	11th to 20th	Day	13% 6% 26% 29% 17% 9%	524
	21st to end	Day	15% 7% 23% 28% 18% 9%	576
August	1st to 10th	Day	16% 5% 22% 28% 21% 8%	526
	11th to 20th	Day	15% 6% 21% 27% 20% 11%	519
	21st to end	Day	10% 6% 24% 27% 21% 12%	583
September	1st to 10th	Day	18% 5% 22% 26% 21% 8%	530
	11th to 20th	Day	11% 3 18% 31% 25% 11%	522
	21st to end	Day	25% 10% 26% 21% 14% 4	490
October	1st to 10th	Day	16% 8% 28% 26% 17% 5%	490
	11th to 20th	Day	23% 13% 28% 23% 10% 2	490
	21st to end	Day	28% 15% 30% 19% 6% 1	539
November	1st to 10th	Day	20% 18% 35% 15% 10% 2	386
	11th to 20th	Day	31% 16% 32% 15% 7%	283
	21st to end	Day	28% 26% 35% 12% 1 1	200
December	1st to 10th	Day	34% 25% 29% 9% 3 1	200
	11th to 20th	Day	31% 26% 30% 12% 3	200
	21st to end	Day	35% 27% 24% 11% 3	275
January	1st to 10th	Night	30% 18% 32% 16% 3 1	800
	11th to 20th	Night	32% 19% 29% 18% 3	800
	21st to end	Night	30% 18% 30% 18% 4	880
February	1st to 10th	Night	30% 18% 25% 24% 2	800
	11th to 20th	Night	32% 18% 34% 15% 1	783
	21st to end	Night	29% 17% 34% 18% 2	660
March	1st to 10th	Night	25% 18% 29% 24% 4	800
	11th to 20th	Night	27% 17% 28% 22% 6% 1	800
	21st to end	Night	27% 15% 29% 23% 5%	880
April	1st to 10th	Night	28% 15% 31% 21% 6%	800
	11th to 20th	Night	23% 13% 31% 23% 10% 1	733
	21st to end	Night	21% 10% 34% 27% 8%	600
May	1st to 10th	Night	24% 10% 23% 31% 11% 1	600
	11th to 20th	Night	23% 6% 23% 33% 14% 1	591
	21st to end	Night	13% 4 21% 35% 24% 3	627
June	1st to 10th	Night	11% 3 26% 40% 20% 1	400
	11th to 20th	Night	13% 4 20% 41% 21% 1	400
	21st to end	Night	10% 3 26% 37% 24% 1	434
July	1st to 10th	Night	11% 2 16% 39% 26% 6%	585
	11th to 20th	Night	9% 3 16% 36% 32% 3	582
	21st to end	Night	12% 3 13% 38% 31% 3	657
August	1st to 10th	Night	10% 3 15% 39% 31% 3	597
	11th to 20th	Night	11% 4 11% 37% 31% 6%	594
	21st to end	Night	11% 3 16% 32% 31% 6%	745
September	1st to 10th	Night	14% 4 17% 35% 25% 6%	800
	11th to 20th	Night	11% 3 18% 33% 30% 5%	793
	21st to end	Night	19% 7% 22% 28% 19% 4	760
October	1st to 10th	Night	16% 7% 22% 32% 20% 4	760
	11th to 20th	Night	20% 8% 29% 29% 12% 1	760
	21st to end	Night	26% 11% 26% 27% 9% 1	836
November	1st to 10th	Night	18% 10% 28% 30% 14% 1	780
	11th to 20th	Night	27% 16% 26% 23% 8% 1	800
	21st to end	Night	28% 12% 29% 25% 6%	800
December	1st to 10th	Night	32% 16% 28% 20% 5%	800
	11th to 20th	Night	31% 16% 28% 20% 4	800
	21st to end	Night	31% 15% 28% 23% 2	880

Page generated at 2025-09-16 01:49:11. Version ac07

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