Cape Lookout National Seashore
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cape Lookout National Seashore clear sky chart from 2005-11-06 to 2024-07-02.

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% 6% 2 6% 4 4 4 4 6% 8% 43%	89355
	Night	12% 7% 3 7% 4 4 4 4 6% 8% 42%	89777
Transparency	Day	37% 8% 15% 22% 14% 3	89125
	Night	40% 7% 14% 20% 16% 3	89611
Seeing	Day	14% 5% 18% 27% 27% 10%	15056
	Night	14% 7% 21% 28% 23% 6%	24921

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	10% 8% 2 6% 3 3 4 3 5% 7% 49%	2836
	11th to 20th	Day	10% 7% 3 5% 4 5% 5% 3 6% 7% 45%	2840
	21st to end	Day	13% 8% 4 7% 5% 5% 4 3 5% 7% 38%	3124
February	1st to 10th	Day	15% 6% 2 6% 4 5% 4 4 7% 7% 40%	1724
	11th to 20th	Day	17% 8% 3 6% 4 4 3 3 4 4 43%	1848
	21st to end	Day	13% 8% 3 7% 3 4 4 4 5% 8% 41%	1570
March	1st to 10th	Day	22% 10% 3 7% 3 3 4 3 4 5% 35%	3395
	11th to 20th	Day	9% 5% 2 5% 3 3 4 3 4 7% 54%	3480
	21st to end	Day	15% 6% 2 5% 4 4 3 2 5% 7% 48%	3900
April	1st to 10th	Day	11% 5% 2 4 3 3 3 3 5% 7% 52%	2280
	11th to 20th	Day	8% 4 2 5% 4 4 4 4 7% 8% 50%	2254
	21st to end	Day	8% 4 2 4 4 4 5% 4 5% 7% 53%	2280
May	1st to 10th	Day	7% 5% 2 6% 5% 5% 5% 5% 7% 10% 42%	3765
	11th to 20th	Day	16% 8% 3 9% 6% 5% 5% 4 6% 8% 31%	3904
	21st to end	Day	7% 5% 2 6% 4 5% 5% 4 7% 12% 44%	4684
June	1st to 10th	Day	9% 6% 3 6% 5% 5% 5% 4 8% 10% 38%	2660
	11th to 20th	Day	8% 4 2 5% 4 4 5% 5% 7% 13% 42%	2660
	21st to end	Day	6% 5% 2 6% 5% 5% 6% 7% 9% 12% 37%	2660
July	1st to 10th	Day	9% 6% 2 6% 5% 4 5% 5% 9% 13% 37%	2365
	11th to 20th	Day	7% 5% 2 6% 5% 4 6% 6% 9% 12% 38%	2340
	21st to end	Day	8% 6% 3 7% 6% 5% 5% 5% 9% 11% 36%	2547
August	1st to 10th	Day	11% 6% 2 7% 5% 5% 6% 5% 8% 11% 33%	2254
	11th to 20th	Day	9% 6% 2 6% 5% 6% 5% 5% 8% 11% 38%	2126
	21st to end	Day	11% 7% 4 7% 5% 5% 5% 4 7% 11% 34%	2376
September	1st to 10th	Day	11% 6% 2 7% 4 4 5% 4 7% 8% 40%	2160
	11th to 20th	Day	13% 7% 3 7% 5% 5% 5% 4 6% 8% 36%	2160
	21st to end	Day	18% 7% 3 7% 4 4 4 4 5% 6% 37%	1927
October	1st to 10th	Day	14% 7% 3 6% 5% 4 3 2 4 7% 45%	1800
	11th to 20th	Day	10% 5% 2 5% 4 4 4 3 5% 7% 51%	1800
	21st to end	Day	10% 5% 2 6% 4 3 3 3 5% 7% 51%	1980
November	1st to 10th	Day	14% 5% 2 4 4 3 3 3 5% 7% 49%	1857
	11th to 20th	Day	13% 6% 2 6% 4 4 3 3 4 5% 49%	1735
	21st to end	Day	11% 6% 3 6% 4 3 3 3 5% 8% 48%	1710
December	1st to 10th	Day	15% 6% 3 7% 6% 4 5% 4 6% 5% 39%	1568
	11th to 20th	Day	15% 7% 2 5% 4 3 3 3 4 5% 51%	1910
	21st to end	Day	12% 9% 3 6% 4 3 4 4 5% 6% 46%	2876
January	1st to 10th	Night	13% 7% 3 6% 4 3 3 3 5% 7% 46%	4109
	11th to 20th	Night	13% 7% 2 7% 5% 4 5% 4 6% 8% 39%	4120
	21st to end	Night	12% 8% 3 7% 4 5% 4 3 5% 7% 43%	4532
February	1st to 10th	Night	17% 8% 2 5% 4 3 3 4 5% 6% 43%	2453
	11th to 20th	Night	17% 9% 2 6% 4 4 4 3 4 5% 40%	2218
	21st to end	Night	15% 7% 2 7% 5% 5% 4 4 6% 6% 40%	1884
March	1st to 10th	Night	21% 11% 4 8% 4 4 4 4 4 5% 30%	3454
	11th to 20th	Night	11% 5% 2 7% 4 4 5% 4 5% 7% 47%	3480
	21st to end	Night	15% 6% 3 5% 3 3 3 3 4 6% 48%	3732
April	1st to 10th	Night	10% 6% 2 5% 4 4 4 3 6% 6% 50%	1900
	11th to 20th	Night	8% 5% 3 7% 5% 4 5% 4 4 7% 47%	1875
	21st to end	Night	8% 5% 2 5% 4 4 3 3 6% 6% 54%	1900
May	1st to 10th	Night	7% 6% 2 6% 4 6% 7% 5% 7% 9% 40%	3130
	11th to 20th	Night	14% 8% 3 9% 5% 5% 4 4 5% 7% 36%	3017
	21st to end	Night	7% 6% 3 6% 4 4 5% 4 7% 10% 43%	2867
June	1st to 10th	Night	9% 8% 3 7% 4 5% 6% 4 8% 10% 36%	1520
	11th to 20th	Night	6% 5% 2 6% 4 5% 5% 6% 7% 11% 43%	1520
	21st to end	Night	8% 6% 2 7% 6% 5% 5% 5% 8% 13% 35%	1520
July	1st to 10th	Night	7% 4 3 6% 5% 5% 5% 6% 10% 14% 34%	1615
	11th to 20th	Night	6% 6% 2 7% 5% 4 6% 5% 8% 11% 38%	1620
	21st to end	Night	8% 6% 3 8% 7% 6% 5% 5% 8% 11% 35%	1771
August	1st to 10th	Night	8% 5% 2 8% 5% 6% 5% 6% 9% 11% 34%	1665
	11th to 20th	Night	9% 5% 3 6% 6% 6% 5% 6% 8% 11% 35%	1774
	21st to end	Night	11% 8% 2 7% 5% 5% 5% 4 7% 11% 34%	1980
September	1st to 10th	Night	9% 6% 3 7% 5% 7% 5% 4 7% 9% 38%	1800
	11th to 20th	Night	11% 8% 4 8% 5% 5% 5% 4 6% 7% 37%	1800
	21st to end	Night	16% 8% 3 9% 4 5% 6% 4 5% 7% 35%	2027
October	1st to 10th	Night	12% 6% 3 7% 4 4 4 3 5% 7% 46%	2160
	11th to 20th	Night	13% 5% 2 5% 4 4 4 3 5% 7% 47%	2160
	21st to end	Night	10% 5% 2 5% 4 4 4 3 4 7% 52%	2376
November	1st to 10th	Night	12% 6% 2 7% 5% 4 4 3 6% 6% 46%	2221
	11th to 20th	Night	13% 9% 3 6% 5% 3 4 3 5% 7% 43%	2441
	21st to end	Night	10% 6% 2 5% 4 4 4 3 4 7% 50%	2470
December	1st to 10th	Night	15% 8% 2 7% 4 3 4 4 5% 7% 40%	2607
	11th to 20th	Night	15% 6% 2 6% 4 4 4 3 5% 6% 46%	3285
	21st to end	Night	13% 7% 3 6% 4 4 3 3 5% 6% 45%	4774

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% 6% 10% 27% 21% 2	2837
	11th to 20th	Day	37% 5% 8% 23% 20% 7%	2840
	21st to end	Day	44% 7% 10% 17% 15% 6%	3124
February	1st to 10th	Day	41% 6% 13% 23% 15% 3	1724
	11th to 20th	Day	45% 4 8% 18% 19% 5%	1857
	21st to end	Day	40% 7% 13% 20% 14% 6%	1570
March	1st to 10th	Day	50% 6% 11% 14% 12% 6%	3395
	11th to 20th	Day	30% 6% 11% 18% 22% 13%	3480
	21st to end	Day	37% 5% 11% 26% 16% 5%	3900
April	1st to 10th	Day	31% 6% 14% 24% 20% 5%	2280
	11th to 20th	Day	30% 6% 14% 26% 18% 6%	2254
	21st to end	Day	30% 6% 14% 28% 19% 3	2280
May	1st to 10th	Day	33% 12% 25% 21% 8% 1	3800
	11th to 20th	Day	47% 9% 14% 22% 8%	3908
	21st to end	Day	29% 11% 18% 32% 9% 1	4698
June	1st to 10th	Day	38% 10% 17% 23% 11%	2660
	11th to 20th	Day	30% 12% 22% 25% 11%	2660
	21st to end	Day	35% 14% 21% 22% 7%	2660
July	1st to 10th	Day	34% 12% 26% 21% 6% 1	2300
	11th to 20th	Day	32% 14% 25% 22% 7%	2271
	21st to end	Day	36% 12% 23% 24% 4	2405
August	1st to 10th	Day	40% 13% 26% 16% 5%	2241
	11th to 20th	Day	36% 13% 22% 21% 8%	2126
	21st to end	Day	41% 11% 21% 20% 6% 1	2376
September	1st to 10th	Day	39% 11% 20% 18% 11% 2	2160
	11th to 20th	Day	44% 9% 14% 18% 13% 2	2160
	21st to end	Day	46% 6% 13% 17% 15% 2	1927
October	1st to 10th	Day	40% 5% 11% 22% 20% 2	1800
	11th to 20th	Day	35% 6% 10% 22% 21% 6%	1800
	21st to end	Day	33% 5% 9% 24% 23% 6%	1980
November	1st to 10th	Day	36% 5% 10% 20% 24% 4	1857
	11th to 20th	Day	39% 4 9% 20% 21% 6%	1735
	21st to end	Day	36% 5% 13% 23% 19% 4	1710
December	1st to 10th	Day	44% 7% 14% 19% 13% 3	1568
	11th to 20th	Day	36% 5% 8% 22% 21% 7%	1906
	21st to end	Day	39% 6% 14% 20% 19% 2	2876
January	1st to 10th	Night	37% 6% 10% 24% 20% 3	4109
	11th to 20th	Night	43% 7% 9% 18% 19% 4	4120
	21st to end	Night	40% 7% 9% 19% 20% 5%	4532
February	1st to 10th	Night	42% 5% 11% 21% 17% 5%	2453
	11th to 20th	Night	46% 5% 10% 17% 17% 5%	2220
	21st to end	Night	45% 5% 10% 18% 16% 6%	1884
March	1st to 10th	Night	55% 7% 8% 14% 12% 3	3454
	11th to 20th	Night	36% 7% 10% 13% 21% 12%	3480
	21st to end	Night	38% 4 12% 26% 15% 5%	3732
April	1st to 10th	Night	35% 6% 14% 19% 22% 6%	1900
	11th to 20th	Night	36% 6% 12% 23% 16% 6%	1875
	21st to end	Night	29% 6% 15% 30% 16% 4	1900
May	1st to 10th	Night	35% 12% 22% 21% 9% 1	3160
	11th to 20th	Night	45% 9% 14% 20% 11%	3018
	21st to end	Night	33% 10% 23% 24% 10%	2874
June	1st to 10th	Night	41% 8% 19% 21% 11% 1	1520
	11th to 20th	Night	31% 11% 22% 24% 11%	1520
	21st to end	Night	38% 12% 19% 22% 8%	1520
July	1st to 10th	Night	34% 14% 25% 19% 8%	1570
	11th to 20th	Night	37% 12% 23% 22% 6%	1566
	21st to end	Night	39% 12% 23% 21% 5% 1	1672
August	1st to 10th	Night	39% 13% 27% 19% 3	1654
	11th to 20th	Night	39% 13% 22% 19% 7% 1	1774
	21st to end	Night	43% 11% 21% 19% 6% 1	1980
September	1st to 10th	Night	42% 12% 18% 16% 12% 1	1800
	11th to 20th	Night	45% 10% 13% 18% 12% 2	1800
	21st to end	Night	49% 6% 12% 19% 14% 1	2027
October	1st to 10th	Night	38% 6% 11% 22% 20% 3	2160
	11th to 20th	Night	37% 6% 10% 23% 19% 5%	2160
	21st to end	Night	32% 5% 9% 25% 24% 6%	2376
November	1st to 10th	Night	41% 5% 11% 16% 22% 5%	2221
	11th to 20th	Night	44% 4 9% 17% 21% 5%	2441
	21st to end	Night	35% 5% 11% 24% 20% 5%	2470
December	1st to 10th	Night	44% 6% 13% 18% 16% 3	2607
	11th to 20th	Night	39% 5% 9% 19% 23% 5%	3288
	21st to end	Night	40% 5% 12% 23% 18% 2	4774

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	17% 12% 32% 29% 10% 1	270
	11th to 20th	Day	14% 8% 30% 33% 14% 1	270
	21st to end	Day	15% 9% 36% 28% 11% 1	297
February	1st to 10th	Day	17% 8% 32% 30% 14%	284
	11th to 20th	Day	23% 11% 33% 25% 6% 1	456
	21st to end	Day	15% 9% 30% 32% 12% 2	382
March	1st to 10th	Day	14% 8% 32% 29% 14% 2	460
	11th to 20th	Day	16% 10% 31% 28% 13% 1	460
	21st to end	Day	15% 6% 32% 34% 11% 2	506
April	1st to 10th	Day	13% 12% 24% 31% 18% 2	460
	11th to 20th	Day	9% 4 25% 29% 26% 6%	452
	21st to end	Day	8% 4 21% 34% 27% 6%	460
May	1st to 10th	Day	9% 5% 22% 36% 21% 8%	463
	11th to 20th	Day	15% 3 14% 28% 30% 10%	487
	21st to end	Day	13% 2 8% 24% 33% 19%	529
June	1st to 10th	Day	11% 1 8% 30% 37% 11%	490
	11th to 20th	Day	10% 1 9% 25% 35% 20%	490
	21st to end	Day	8% 1 8% 23% 45% 15%	490
July	1st to 10th	Day	11% 2 6% 20% 42% 20%	449
	11th to 20th	Day	9% 2 4 15% 50% 21%	444
	21st to end	Day	9% 2 8% 21% 44% 15%	488
August	1st to 10th	Day	14% 2 6% 21% 35% 22%	446
	11th to 20th	Day	9% 2 3 21% 38% 27%	439
	21st to end	Day	14% 1 5% 20% 40% 20%	495
September	1st to 10th	Day	13% 1 8% 20% 33% 24%	450
	11th to 20th	Day	16% 2 12% 20% 35% 15%	450
	21st to end	Day	20% 3 9% 27% 26% 15%	450
October	1st to 10th	Day	18% 3 14% 21% 30% 13%	450
	11th to 20th	Day	12% 2 18% 31% 28% 8%	450
	21st to end	Day	12% 5% 19% 30% 28% 7%	495
November	1st to 10th	Day	17% 7% 18% 29% 22% 6%	455
	11th to 20th	Day	16% 6% 29% 31% 16% 2	382
	21st to end	Day	14% 6% 27% 30% 20% 3	370
December	1st to 10th	Day	19% 4 33% 29% 15%	228
	11th to 20th	Day	18% 9% 28% 28% 15% 2	180
	21st to end	Day	16% 5% 28% 28% 20% 3	229
January	1st to 10th	Night	15% 16% 34% 23% 10% 1	760
	11th to 20th	Night	16% 13% 28% 31% 11% 1	760
	21st to end	Night	18% 14% 35% 28% 5%	836
February	1st to 10th	Night	21% 10% 30% 30% 9%	760
	11th to 20th	Night	22% 14% 35% 23% 7%	743
	21st to end	Night	20% 11% 28% 32% 9% 1	628
March	1st to 10th	Night	16% 9% 34% 29% 11% 2	760
	11th to 20th	Night	14% 10% 30% 32% 12% 3	760
	21st to end	Night	15% 8% 30% 32% 13% 2	836
April	1st to 10th	Night	13% 7% 33% 31% 14% 2	760
	11th to 20th	Night	11% 7% 25% 32% 21% 5%	751
	21st to end	Night	10% 4 21% 37% 25% 3	760
May	1st to 10th	Night	12% 4 24% 36% 20% 4	760
	11th to 20th	Night	14% 4 19% 33% 24% 7%	688
	21st to end	Night	11% 2 8% 27% 37% 14%	495
June	1st to 10th	Night	12% 3 12% 35% 30% 9%	380
	11th to 20th	Night	8% 2 11% 29% 38% 13%	380
	21st to end	Night	8% 3 9% 33% 37% 9%	380
July	1st to 10th	Night	8% 1 5% 26% 46% 14%	510
	11th to 20th	Night	9% 2 5% 18% 47% 19%	522
	21st to end	Night	9% 2 8% 28% 42% 11%	591
August	1st to 10th	Night	10% 2 6% 27% 43% 13%	591
	11th to 20th	Night	11% 1 5% 22% 39% 21%	710
	21st to end	Night	12% 2 7% 20% 43% 16%	792
September	1st to 10th	Night	12% 2 7% 23% 35% 21%	720
	11th to 20th	Night	15% 2 10% 27% 36% 10%	720
	21st to end	Night	23% 2 11% 22% 31% 10%	720
October	1st to 10th	Night	16% 3 14% 27% 30% 11%	720
	11th to 20th	Night	16% 4 19% 30% 25% 6%	720
	21st to end	Night	13% 7% 23% 28% 23% 6%	792
November	1st to 10th	Night	16% 6% 19% 33% 21% 5%	740
	11th to 20th	Night	18% 9% 24% 30% 16% 4	760
	21st to end	Night	13% 11% 27% 26% 20% 3	760
December	1st to 10th	Night	18% 10% 29% 27% 14% 1	760
	11th to 20th	Night	16% 8% 31% 29% 13% 2	760
	21st to end	Night	17% 10% 31% 29% 11% 2	836

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