Wright Brothers National Memorial
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wright Brothers National Memorial clear sky chart from 2005-11-06 to 2025-06-10.

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	11% 7% 2 6% 4 4 5% 4 6% 8% 42%	119132
	Night	12% 7% 2 6% 4 4 4 4 6% 7% 42%	119103
Transparency	Day	38% 7% 14% 22% 16% 3	122765
	Night	39% 6% 12% 21% 18% 4	123607
Seeing	Day	14% 7% 21% 28% 22% 7%	16181
	Night	16% 7% 22% 31% 20% 4	25817

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	11% 7% 3 6% 3 3 4 3 4 5% 52%	3804
	11th to 20th	Day	12% 5% 2 5% 4 4 3 3 4 5% 52%	4060
	21st to end	Day	12% 11% 3 8% 4 5% 4 3 6% 6% 38%	4466
February	1st to 10th	Day	13% 8% 3 7% 5% 4 4 3 5% 7% 41%	1844
	11th to 20th	Day	19% 8% 3 6% 5% 4 3 3 5% 5% 41%	1948
	21st to end	Day	14% 7% 2 5% 5% 3 5% 4 5% 6% 43%	1650
March	1st to 10th	Day	18% 8% 2 6% 4 3 4 3 5% 6% 41%	4656
	11th to 20th	Day	9% 5% 2 6% 4 4 4 3 4 6% 52%	4980
	21st to end	Day	11% 7% 2 5% 3 4 4 3 5% 7% 50%	5712
April	1st to 10th	Day	12% 6% 2 5% 4 4 4 3 5% 6% 51%	2400
	11th to 20th	Day	8% 5% 2 5% 4 4 3 4 5% 8% 51%	2374
	21st to end	Day	9% 5% 2 5% 4 4 4 3 6% 9% 50%	2400
May	1st to 10th	Day	8% 6% 3 7% 5% 6% 6% 5% 7% 9% 38%	5405
	11th to 20th	Day	15% 8% 3 8% 5% 5% 6% 4 6% 9% 31%	5839
	21st to end	Day	12% 7% 3 7% 4 4 4 4 5% 8% 41%	6934
June	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 4 7% 11% 42%	2786
	11th to 20th	Day	8% 4 2 5% 4 5% 5% 4 7% 11% 45%	2660
	21st to end	Day	5% 5% 2 6% 5% 5% 5% 6% 9% 12% 41%	2660
July	1st to 10th	Day	8% 5% 2 6% 5% 4 5% 5% 8% 13% 38%	4440
	11th to 20th	Day	8% 6% 3 9% 5% 5% 6% 5% 9% 12% 32%	4223
	21st to end	Day	10% 7% 3 8% 6% 6% 7% 5% 8% 9% 32%	4466
August	1st to 10th	Day	12% 10% 4 8% 6% 5% 5% 4 7% 10% 28%	3931
	11th to 20th	Day	9% 6% 2 6% 4 4 5% 4 7% 9% 43%	3730
	21st to end	Day	7% 5% 2 6% 5% 5% 6% 4 7% 10% 43%	4180
September	1st to 10th	Day	11% 6% 2 6% 4 5% 6% 5% 7% 9% 40%	2280
	11th to 20th	Day	12% 7% 2 8% 5% 5% 5% 4 5% 7% 40%	2262
	21st to end	Day	18% 6% 3 9% 5% 4 4 4 5% 7% 36%	2085
October	1st to 10th	Day	15% 6% 2 6% 4 3 4 3 5% 6% 46%	1900
	11th to 20th	Day	14% 6% 2 5% 4 4 4 2 5% 5% 49%	1900
	21st to end	Day	11% 6% 2 5% 4 4 4 4 6% 6% 49%	2090
November	1st to 10th	Day	17% 5% 2 6% 4 5% 4 4 5% 6% 43%	1840
	11th to 20th	Day	15% 6% 2 4 4 4 3 3 5% 7% 46%	1800
	21st to end	Day	12% 6% 3 6% 4 3 4 4 5% 7% 47%	1800
December	1st to 10th	Day	11% 6% 2 5% 4 4 4 3 5% 6% 51%	2677
	11th to 20th	Day	13% 9% 2 7% 6% 4 5% 4 6% 5% 38%	2990
	21st to end	Day	13% 6% 2 5% 4 4 4 4 5% 8% 46%	3960
January	1st to 10th	Night	12% 7% 3 5% 4 3 4 3 4 6% 51%	6137
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 5% 6% 49%	5900
	21st to end	Night	13% 8% 3 8% 5% 4 4 3 5% 6% 42%	6490
February	1st to 10th	Night	17% 8% 3 6% 4 3 3 3 6% 7% 41%	2555
	11th to 20th	Night	19% 8% 3 6% 4 4 4 3 5% 6% 39%	2338
	21st to end	Night	14% 7% 3 7% 4 3 4 3 5% 6% 44%	1980
March	1st to 10th	Night	17% 8% 3 7% 5% 4 4 3 4 5% 39%	5193
	11th to 20th	Night	14% 6% 2 6% 3 4 3 4 5% 5% 48%	4980
	21st to end	Night	14% 7% 3 6% 4 3 3 3 4 5% 48%	5220
April	1st to 10th	Night	12% 6% 2 6% 4 4 4 3 5% 8% 46%	2000
	11th to 20th	Night	9% 7% 3 6% 3 3 4 4 6% 7% 47%	1975
	21st to end	Night	12% 5% 2 6% 5% 4 5% 2 5% 7% 48%	2000
May	1st to 10th	Night	8% 7% 3 9% 6% 5% 6% 5% 7% 10% 34%	4490
	11th to 20th	Night	18% 8% 3 7% 5% 4 5% 4 6% 9% 30%	4091
	21st to end	Night	11% 9% 4 8% 5% 4 5% 4 6% 8% 37%	3920
June	1st to 10th	Night	11% 6% 2 5% 5% 5% 4 5% 6% 9% 42%	1598
	11th to 20th	Night	7% 5% 2 5% 4 4 5% 6% 8% 11% 43%	1520
	21st to end	Night	7% 4 2 5% 5% 5% 5% 4 9% 12% 42%	1520
July	1st to 10th	Night	7% 4 2 6% 5% 5% 6% 5% 8% 13% 40%	2520
	11th to 20th	Night	8% 7% 3 7% 5% 6% 5% 5% 8% 13% 34%	2732
	21st to end	Night	12% 6% 3 7% 6% 6% 7% 5% 9% 10% 30%	3087
August	1st to 10th	Night	14% 9% 3 8% 6% 5% 5% 5% 7% 10% 28%	2953
	11th to 20th	Night	8% 6% 3 8% 6% 5% 6% 4 7% 8% 39%	3097
	21st to end	Night	9% 5% 2 7% 5% 4 5% 4 7% 9% 42%	3476
September	1st to 10th	Night	12% 5% 2 5% 5% 5% 5% 5% 7% 9% 40%	1900
	11th to 20th	Night	14% 8% 2 7% 5% 5% 5% 4 6% 7% 38%	1916
	21st to end	Night	17% 9% 3 7% 4 5% 5% 4 5% 7% 34%	2091
October	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 4 8% 46%	2280
	11th to 20th	Night	14% 6% 2 6% 3 3 3 3 4 6% 50%	2280
	21st to end	Night	12% 6% 2 5% 3 4 4 3 5% 7% 50%	2508
November	1st to 10th	Night	16% 7% 2 6% 5% 4 4 3 6% 6% 41%	2456
	11th to 20th	Night	15% 7% 3 6% 5% 4 4 5% 5% 6% 41%	2600
	21st to end	Night	12% 6% 2 5% 4 4 4 3 6% 7% 48%	2600
December	1st to 10th	Night	10% 6% 2 5% 4 3 3 3 4 5% 54%	4499
	11th to 20th	Night	14% 7% 2 8% 5% 5% 5% 4 7% 7% 37%	5205
	21st to end	Night	11% 8% 2 5% 4 4 5% 3 6% 8% 46%	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	34% 4 7% 26% 19% 10%	3805
	11th to 20th	Day	35% 3 6% 19% 32% 5%	4060
	21st to end	Day	46% 6% 8% 18% 19% 3	4466
February	1st to 10th	Day	43% 4 12% 24% 15% 3	1844
	11th to 20th	Day	46% 4 9% 17% 19% 5%	1957
	21st to end	Day	41% 6% 11% 22% 16% 4	1650
March	1st to 10th	Day	45% 4 9% 19% 16% 7%	4656
	11th to 20th	Day	33% 4 8% 18% 25% 11%	4980
	21st to end	Day	36% 5% 14% 23% 18% 5%	5712
April	1st to 10th	Day	34% 5% 15% 21% 21% 4	2400
	11th to 20th	Day	31% 5% 13% 27% 18% 5%	2374
	21st to end	Day	31% 6% 15% 28% 17% 3	2400
May	1st to 10th	Day	40% 9% 19% 21% 9% 1	5437
	11th to 20th	Day	48% 9% 16% 19% 8% 1	5843
	21st to end	Day	39% 8% 14% 27% 11% 1	6949
June	1st to 10th	Day	34% 10% 15% 26% 13% 1	2786
	11th to 20th	Day	32% 9% 19% 28% 12%	2660
	21st to end	Day	33% 11% 19% 25% 11% 1	2660
July	1st to 10th	Day	36% 11% 21% 23% 9% 1	4370
	11th to 20th	Day	42% 12% 26% 16% 5%	4150
	21st to end	Day	46% 11% 15% 18% 10%	4324
August	1st to 10th	Day	51% 9% 23% 14% 4	3918
	11th to 20th	Day	36% 9% 18% 24% 12%	3766
	21st to end	Day	36% 8% 17% 27% 12% 1	4180
September	1st to 10th	Day	38% 10% 18% 19% 14% 2	2280
	11th to 20th	Day	42% 8% 11% 21% 16% 2	2262
	21st to end	Day	47% 7% 12% 19% 13% 1	2085
October	1st to 10th	Day	34% 5% 8% 24% 25% 5%	3160
	11th to 20th	Day	31% 4 5% 23% 24% 13%	3140
	21st to end	Day	24% 4 8% 32% 30% 3	3428
November	1st to 10th	Day	41% 6% 11% 21% 18% 3	1840
	11th to 20th	Day	38% 5% 11% 24% 17% 5%	1800
	21st to end	Day	36% 5% 11% 25% 20% 3	1800
December	1st to 10th	Day	34% 4 10% 27% 23% 2	2677
	11th to 20th	Day	46% 5% 13% 18% 13% 5%	2986
	21st to end	Day	36% 5% 14% 29% 15% 1	3960
January	1st to 10th	Night	35% 4 6% 22% 26% 7%	6137
	11th to 20th	Night	37% 4 6% 20% 28% 6%	5900
	21st to end	Night	42% 5% 9% 19% 21% 5%	6490
February	1st to 10th	Night	43% 4 11% 23% 17% 3	2555
	11th to 20th	Night	46% 4 9% 18% 18% 4	2340
	21st to end	Night	41% 5% 9% 20% 19% 6%	1980
March	1st to 10th	Night	48% 4 8% 19% 14% 7%	5193
	11th to 20th	Night	37% 5% 8% 13% 24% 12%	4980
	21st to end	Night	40% 4 10% 25% 15% 6%	5220
April	1st to 10th	Night	38% 6% 13% 19% 21% 5%	2000
	11th to 20th	Night	35% 6% 12% 24% 19% 5%	1975
	21st to end	Night	36% 7% 10% 27% 17% 3	2000
May	1st to 10th	Night	42% 10% 18% 20% 9% 1	4520
	11th to 20th	Night	50% 8% 13% 20% 7% 1	4092
	21st to end	Night	43% 9% 12% 23% 11% 1	3927
June	1st to 10th	Night	37% 9% 15% 24% 14% 1	1598
	11th to 20th	Night	30% 11% 19% 26% 13%	1520
	21st to end	Night	34% 10% 21% 23% 12% 1	1520
July	1st to 10th	Night	34% 13% 23% 19% 11% 1	2480
	11th to 20th	Night	40% 11% 27% 17% 4	2682
	21st to end	Night	46% 14% 15% 15% 10%	2988
August	1st to 10th	Night	50% 10% 20% 17% 3	2942
	11th to 20th	Night	41% 8% 17% 21% 12%	3127
	21st to end	Night	38% 6% 15% 27% 13% 2	3476
September	1st to 10th	Night	40% 9% 18% 18% 13% 2	1900
	11th to 20th	Night	44% 7% 12% 22% 14% 2	1916
	21st to end	Night	49% 7% 10% 21% 13%	2091
October	1st to 10th	Night	39% 5% 7% 21% 26% 3	3800
	11th to 20th	Night	28% 3 6% 20% 29% 14%	3779
	21st to end	Night	22% 3 7% 32% 30% 5%	4120
November	1st to 10th	Night	42% 6% 10% 22% 18% 2	2456
	11th to 20th	Night	43% 5% 10% 19% 18% 5%	2600
	21st to end	Night	36% 4 11% 25% 21% 3	2600
December	1st to 10th	Night	33% 4 8% 20% 30% 5%	4499
	11th to 20th	Night	45% 6% 14% 15% 15% 5%	5208
	21st to end	Night	35% 6% 16% 27% 15% 2	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	14% 20% 30% 29% 7%	245
	11th to 20th	Day	16% 15% 37% 26% 6%	300
	21st to end	Day	19% 14% 32% 27% 8% 1	330
February	1st to 10th	Day	18% 13% 29% 32% 7%	344
	11th to 20th	Day	26% 14% 33% 24% 3	496
	21st to end	Day	17% 9% 35% 29% 9% 1	414
March	1st to 10th	Day	17% 14% 33% 26% 8% 1	500
	11th to 20th	Day	20% 11% 32% 26% 9% 1	500
	21st to end	Day	13% 10% 34% 31% 10% 1	550
April	1st to 10th	Day	15% 11% 32% 29% 11% 1	500
	11th to 20th	Day	9% 7% 32% 33% 16% 4	492
	21st to end	Day	11% 6% 26% 34% 20% 3	500
May	1st to 10th	Day	13% 6% 26% 32% 19% 4	503
	11th to 20th	Day	15% 3 20% 31% 26% 5%	527
	21st to end	Day	15% 3 16% 27% 28% 11%	573
June	1st to 10th	Day	10% 2 14% 35% 29% 10%	526
	11th to 20th	Day	11% 2 11% 30% 32% 14%	490
	21st to end	Day	7% 1 10% 33% 38% 11%	490
July	1st to 10th	Day	10% 2 6% 25% 40% 16%	485
	11th to 20th	Day	7% 1 6% 22% 46% 18%	484
	21st to end	Day	11% 2 8% 27% 39% 14%	532
August	1st to 10th	Day	12% 3 8% 27% 38% 12%	486
	11th to 20th	Day	12% 1 7% 22% 38% 20%	479
	21st to end	Day	11% 1 8% 26% 35% 18%	539
September	1st to 10th	Day	12% 2 13% 25% 31% 17%	490
	11th to 20th	Day	14% 4 13% 29% 31% 9%	490
	21st to end	Day	22% 3 15% 29% 24% 7%	490
October	1st to 10th	Day	20% 4 13% 29% 25% 9%	490
	11th to 20th	Day	17% 6% 21% 28% 24% 4	490
	21st to end	Day	13% 8% 19% 29% 24% 7%	539
November	1st to 10th	Day	16% 8% 20% 33% 16% 6%	436
	11th to 20th	Day	18% 11% 27% 29% 13% 3	400
	21st to end	Day	12% 17% 26% 26% 19% 2	400
December	1st to 10th	Day	20% 11% 35% 24% 9% 1	251
	11th to 20th	Day	17% 13% 34% 25% 11% 2	200
	21st to end	Day	18% 9% 33% 25% 14% 1	220
January	1st to 10th	Night	18% 19% 31% 24% 8% 1	800
	11th to 20th	Night	18% 14% 28% 31% 9% 1	800
	21st to end	Night	19% 13% 34% 29% 5%	880
February	1st to 10th	Night	20% 8% 35% 30% 6%	800
	11th to 20th	Night	23% 13% 35% 25% 4	783
	21st to end	Night	18% 10% 34% 27% 10%	660
March	1st to 10th	Night	15% 10% 34% 31% 9% 1	800
	11th to 20th	Night	20% 9% 30% 30% 10% 2	800
	21st to end	Night	16% 8% 32% 33% 10% 1	880
April	1st to 10th	Night	15% 8% 33% 33% 11%	800
	11th to 20th	Night	13% 6% 28% 35% 17% 2	791
	21st to end	Night	14% 6% 21% 40% 17% 2	800
May	1st to 10th	Night	12% 7% 24% 37% 18% 2	800
	11th to 20th	Night	16% 4 17% 42% 17% 3	624
	21st to end	Night	12% 2 9% 32% 34% 10%	433
June	1st to 10th	Night	13% 3 10% 37% 32% 5%	400
	11th to 20th	Night	9% 3 10% 36% 35% 8%	380
	21st to end	Night	7% 1 6% 39% 41% 5%	380
July	1st to 10th	Night	6% 1 8% 29% 48% 8%	370
	11th to 20th	Night	8% 6% 26% 44% 16%	487
	21st to end	Night	9% 1 8% 32% 43% 7%	624
August	1st to 10th	Night	13% 2 6% 31% 42% 7%	643
	11th to 20th	Night	11% 1 8% 28% 41% 12%	750
	21st to end	Night	16% 1 6% 24% 40% 13%	836
September	1st to 10th	Night	14% 2 9% 23% 36% 15%	760
	11th to 20th	Night	18% 3 11% 29% 34% 6%	760
	21st to end	Night	21% 4 12% 28% 29% 6%	760
October	1st to 10th	Night	15% 4 16% 28% 30% 9%	760
	11th to 20th	Night	16% 8% 20% 33% 19% 3	760
	21st to end	Night	14% 7% 24% 27% 23% 5%	836
November	1st to 10th	Night	19% 5% 22% 32% 17% 5%	780
	11th to 20th	Night	19% 10% 26% 29% 16% 2	800
	21st to end	Night	13% 13% 24% 31% 17% 2	800
December	1st to 10th	Night	19% 12% 30% 28% 12%	800
	11th to 20th	Night	17% 10% 32% 30% 11%	800
	21st to end	Night	16% 12% 29% 32% 11% 1	880

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