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 2024-11-03.

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	12% 7% 2 6% 5% 4 5% 4 6% 8% 41%	100864
	Night	13% 7% 2 6% 5% 4 4 4 6% 7% 41%	98063
Transparency	Day	39% 8% 14% 22% 14% 3	100661
	Night	41% 7% 12% 22% 15% 3	97936
Seeing	Day	14% 6% 20% 29% 23% 7%	15434
	Night	16% 7% 22% 31% 21% 4	24989

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	12% 8% 3 7% 3 4 4 4 5% 6% 45%	2654
	11th to 20th	Day	11% 6% 2 7% 5% 5% 4 3 4 6% 47%	2840
	21st to end	Day	13% 10% 2 8% 5% 4 5% 4 6% 8% 36%	3124
February	1st to 10th	Day	12% 8% 3 7% 5% 4 4 4 5% 7% 41%	1751
	11th to 20th	Day	18% 7% 3 6% 5% 4 3 3 5% 4 41%	1848
	21st to end	Day	14% 7% 3 5% 5% 3 5% 4 5% 6% 42%	1570
March	1st to 10th	Day	21% 9% 3 6% 4 3 3 3 5% 6% 38%	3240
	11th to 20th	Day	10% 4 1 5% 4 4 3 3 4 6% 56%	3480
	21st to end	Day	15% 9% 2 5% 3 3 4 3 4 6% 46%	3992
April	1st to 10th	Day	12% 6% 2 4 4 3 4 3 4 5% 52%	2280
	11th to 20th	Day	8% 5% 2 5% 4 4 3 4 5% 8% 51%	2254
	21st to end	Day	10% 5% 2 5% 4 4 4 3 6% 8% 51%	2280
May	1st to 10th	Day	9% 5% 3 6% 5% 6% 6% 5% 7% 10% 39%	3765
	11th to 20th	Day	17% 9% 3 8% 5% 5% 6% 4 6% 7% 31%	4059
	21st to end	Day	7% 7% 3 7% 5% 5% 5% 4 6% 9% 43%	4823
June	1st to 10th	Day	8% 5% 2 5% 5% 5% 5% 4 8% 11% 42%	2660
	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	18% 5% 2 5% 3 5% 4 4 5% 5% 43%	1766
	11th to 20th	Day	15% 6% 2 4 5% 4 3 3 5% 7% 47%	1710
	21st to end	Day	13% 6% 3 6% 4 3 4 4 5% 7% 47%	1710
December	1st to 10th	Day	16% 8% 2 5% 5% 5% 4 4 6% 7% 38%	1569
	11th to 20th	Day	15% 9% 2 6% 5% 4 3 3 5% 5% 43%	1910
	21st to end	Day	15% 7% 2 5% 4 4 4 4 5% 7% 45%	2772
January	1st to 10th	Night	14% 7% 3 6% 4 3 5% 3 5% 7% 43%	4287
	11th to 20th	Night	15% 7% 2 6% 4 5% 4 4 6% 6% 41%	4120
	21st to end	Night	14% 8% 3 8% 5% 5% 4 4 5% 5% 39%	4532
February	1st to 10th	Night	17% 8% 3 5% 4 3 3 3 6% 7% 41%	2428
	11th to 20th	Night	19% 8% 3 6% 4 4 4 3 5% 6% 39%	2218
	21st to end	Night	14% 7% 3 7% 4 3 4 3 5% 6% 43%	1884
March	1st to 10th	Night	20% 10% 3 8% 6% 4 5% 3 4 6% 31%	3609
	11th to 20th	Night	13% 6% 2 6% 3 4 3 3 5% 5% 50%	3480
	21st to end	Night	17% 9% 3 6% 3 3 3 2 4 4 46%	3640
April	1st to 10th	Night	13% 5% 2 6% 4 4 4 3 5% 8% 46%	1900
	11th to 20th	Night	10% 7% 3 6% 4 3 4 4 6% 7% 47%	1875
	21st to end	Night	12% 5% 2 6% 4 4 4 2 5% 7% 48%	1900
May	1st to 10th	Night	8% 6% 3 9% 5% 5% 6% 5% 7% 9% 37%	3130
	11th to 20th	Night	20% 7% 3 7% 5% 4 4 4 5% 7% 34%	2857
	21st to end	Night	7% 9% 4 7% 4 4 5% 4 6% 9% 41%	2732
June	1st to 10th	Night	11% 6% 2 5% 5% 5% 4 4 6% 9% 42%	1520
	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 7% 5% 4 4 3 6% 6% 40%	2355
	11th to 20th	Night	15% 7% 3 6% 5% 3 4 4 5% 6% 42%	2470
	21st to end	Night	12% 6% 2 5% 4 4 4 3 6% 7% 48%	2470
December	1st to 10th	Night	16% 8% 3 7% 5% 4 4 4 5% 7% 38%	2607
	11th to 20th	Night	15% 7% 2 6% 4 4 4 3 5% 7% 44%	3285
	21st to end	Night	11% 8% 2 6% 4 4 5% 3 5% 7% 46%	4884

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	38% 5% 10% 30% 14% 2	2655
	11th to 20th	Day	39% 4 8% 20% 24% 5%	2840
	21st to end	Day	45% 9% 10% 17% 17% 2	3124
February	1st to 10th	Day	42% 4 12% 24% 14% 3	1751
	11th to 20th	Day	45% 4 9% 18% 19% 5%	1857
	21st to end	Day	42% 6% 11% 21% 15% 4	1570
March	1st to 10th	Day	48% 5% 12% 19% 11% 6%	3240
	11th to 20th	Day	30% 5% 9% 21% 25% 11%	3480
	21st to end	Day	41% 5% 13% 20% 18% 4	3992
April	1st to 10th	Day	33% 5% 15% 21% 21% 4	2280
	11th to 20th	Day	32% 5% 13% 26% 19% 6%	2254
	21st to end	Day	32% 7% 14% 28% 17% 3	2280
May	1st to 10th	Day	39% 11% 18% 21% 9% 2	3800
	11th to 20th	Day	49% 11% 11% 21% 7% 1	4063
	21st to end	Day	34% 10% 16% 28% 11% 2	4837
June	1st to 10th	Day	34% 11% 16% 26% 13% 1	2660
	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	39% 6% 9% 22% 22% 2	1900
	11th to 20th	Day	37% 5% 7% 25% 21% 5%	1900
	21st to end	Day	35% 5% 8% 24% 25% 3	2090
November	1st to 10th	Day	40% 6% 12% 20% 19% 3	1766
	11th to 20th	Day	37% 5% 11% 24% 17% 5%	1710
	21st to end	Day	36% 5% 11% 25% 20% 3	1710
December	1st to 10th	Day	45% 5% 14% 22% 13% 1	1569
	11th to 20th	Day	42% 4 11% 22% 15% 7%	1906
	21st to end	Day	38% 5% 10% 27% 19% 2	2772
January	1st to 10th	Night	40% 5% 8% 26% 18% 3	4287
	11th to 20th	Night	43% 5% 8% 23% 18% 4	4120
	21st to end	Night	44% 7% 9% 17% 18% 6%	4532
February	1st to 10th	Night	43% 4 10% 23% 17% 3	2428
	11th to 20th	Night	46% 4 9% 18% 18% 5%	2220
	21st to end	Night	42% 5% 9% 21% 18% 6%	1884
March	1st to 10th	Night	55% 5% 9% 18% 11% 2	3609
	11th to 20th	Night	37% 5% 8% 16% 22% 12%	3480
	21st to end	Night	42% 4 8% 27% 14% 5%	3640
April	1st to 10th	Night	37% 6% 12% 18% 21% 5%	1900
	11th to 20th	Night	36% 6% 12% 22% 19% 5%	1875
	21st to end	Night	36% 7% 10% 28% 17% 3	1900
May	1st to 10th	Night	41% 11% 17% 20% 10% 1	3160
	11th to 20th	Night	49% 8% 14% 21% 7% 1	2858
	21st to end	Night	36% 12% 15% 25% 11% 1	2739
June	1st to 10th	Night	37% 9% 15% 25% 13% 1	1520
	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	36% 7% 9% 23% 22% 3	2280
	11th to 20th	Night	37% 4 9% 23% 23% 5%	2280
	21st to end	Night	33% 5% 8% 25% 25% 4	2508
November	1st to 10th	Night	43% 6% 10% 21% 18% 3	2355
	11th to 20th	Night	42% 5% 10% 19% 19% 5%	2470
	21st to end	Night	36% 4 11% 25% 21% 3	2470
December	1st to 10th	Night	46% 5% 12% 19% 14% 3	2607
	11th to 20th	Night	40% 4 10% 21% 19% 5%	3288
	21st to end	Night	37% 6% 13% 25% 18% 2	4884

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% 16% 30% 32% 8%	220
	11th to 20th	Day	17% 14% 34% 27% 7%	270
	21st to end	Day	19% 13% 30% 29% 9% 1	297
February	1st to 10th	Day	17% 13% 28% 34% 7%	311
	11th to 20th	Day	24% 13% 33% 26% 4	456
	21st to end	Day	18% 9% 35% 27% 9% 1	382
March	1st to 10th	Day	17% 13% 33% 27% 9% 1	460
	11th to 20th	Day	20% 11% 33% 25% 10% 1	460
	21st to end	Day	14% 9% 32% 32% 11% 1	506
April	1st to 10th	Day	15% 11% 32% 29% 12% 2	460
	11th to 20th	Day	10% 6% 30% 33% 17% 4	452
	21st to end	Day	11% 7% 25% 34% 20% 3	460
May	1st to 10th	Day	13% 6% 25% 31% 20% 4	463
	11th to 20th	Day	15% 3 18% 32% 27% 6%	487
	21st to end	Day	15% 2 13% 28% 30% 12%	529
June	1st to 10th	Day	10% 2 13% 35% 30% 10%	490
	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	17% 9% 20% 32% 16% 6%	410
	11th to 20th	Day	18% 11% 26% 30% 13% 3	370
	21st to end	Day	12% 15% 24% 26% 20% 2	370
December	1st to 10th	Day	22% 10% 35% 23% 10% 1	229
	11th to 20th	Day	17% 12% 34% 23% 12% 2	180
	21st to end	Day	19% 8% 33% 25% 14% 2	198
January	1st to 10th	Night	18% 16% 32% 25% 9% 1	760
	11th to 20th	Night	18% 14% 27% 32% 9% 1	760
	21st to end	Night	19% 13% 33% 29% 6%	836
February	1st to 10th	Night	20% 8% 34% 31% 6%	760
	11th to 20th	Night	24% 12% 35% 25% 4	743
	21st to end	Night	19% 10% 35% 27% 10%	628
March	1st to 10th	Night	15% 9% 33% 32% 10% 1	760
	11th to 20th	Night	19% 10% 29% 30% 10% 2	760
	21st to end	Night	17% 8% 31% 33% 11% 1	836
April	1st to 10th	Night	15% 8% 32% 34% 11%	760
	11th to 20th	Night	13% 5% 27% 35% 18% 2	751
	21st to end	Night	14% 6% 21% 40% 16% 1	760
May	1st to 10th	Night	12% 7% 23% 38% 18% 2	760
	11th to 20th	Night	16% 4 17% 42% 17% 4	593
	21st to end	Night	11% 1 8% 33% 36% 10%	411
June	1st to 10th	Night	14% 2 10% 37% 32% 5%	380
	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	20% 5% 22% 31% 17% 5%	749
	11th to 20th	Night	18% 9% 25% 29% 16% 2	760
	21st to end	Night	14% 12% 24% 31% 18% 2	760
December	1st to 10th	Night	19% 11% 29% 28% 12%	760
	11th to 20th	Night	17% 10% 32% 29% 12%	760
	21st to end	Night	17% 11% 29% 32% 11% 1	836

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