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 2024-11-30.

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% 3 6% 4 4 4 4 6% 8% 42%	100872
	Night	12% 7% 3 7% 5% 4 4 4 6% 8% 41%	98643
Transparency	Day	38% 8% 16% 22% 13% 4	104516
	Night	39% 7% 14% 21% 15% 4	103138
Seeing	Day	14% 5% 18% 27% 27% 10%	15645
	Night	14% 7% 21% 28% 23% 6%	25490

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	7% 5% 2 6% 5% 5% 6% 7% 9% 11% 37%	2660
July	1st to 10th	Day	10% 5% 2 6% 4 4 5% 5% 8% 13% 38%	4132
	11th to 20th	Day	7% 6% 3 8% 6% 5% 6% 6% 8% 12% 33%	4120
	21st to end	Day	8% 7% 3 8% 7% 5% 6% 5% 8% 12% 31%	4466
August	1st to 10th	Day	16% 11% 4 10% 5% 5% 6% 4 6% 9% 24%	3962
	11th to 20th	Day	8% 5% 2 5% 4 5% 4 5% 7% 10% 45%	3730
	21st to end	Day	8% 6% 3 7% 4 4 4 4 7% 10% 43%	4180
September	1st to 10th	Day	11% 6% 2 7% 4 4 5% 4 7% 8% 40%	2280
	11th to 20th	Day	14% 8% 3 8% 5% 5% 5% 4 6% 8% 36%	2280
	21st to end	Day	18% 7% 3 8% 4 4 4 4 6% 7% 38%	2033
October	1st to 10th	Day	13% 7% 3 6% 5% 4 3 3 4 7% 46%	1900
	11th to 20th	Day	10% 4 2 5% 4 4 4 3 5% 6% 52%	1900
	21st to end	Day	10% 5% 2 6% 4 3 3 3 5% 6% 52%	2090
November	1st to 10th	Day	14% 6% 2 4 4 3 4 3 5% 7% 49%	1957
	11th to 20th	Day	13% 6% 2 6% 4 4 3 3 4 6% 49%	1826
	21st to end	Day	11% 6% 3 6% 4 3 3 3 5% 7% 49%	1798
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 2 6% 5% 6% 6% 5% 9% 14% 36%	2807
	11th to 20th	Night	8% 6% 2 9% 5% 6% 6% 6% 9% 14% 29%	2840
	21st to end	Night	8% 6% 3 7% 6% 5% 6% 6% 10% 13% 31%	3087
August	1st to 10th	Night	12% 11% 4 10% 6% 5% 5% 5% 7% 11% 25%	2921
	11th to 20th	Night	7% 4 2 6% 6% 6% 6% 6% 8% 11% 37%	3097
	21st to end	Night	7% 6% 2 6% 5% 5% 5% 4 7% 10% 43%	3476
September	1st to 10th	Night	10% 6% 3 7% 5% 7% 5% 4 8% 9% 37%	1900
	11th to 20th	Night	11% 8% 4 8% 5% 5% 5% 4 6% 7% 36%	1900
	21st to end	Night	16% 8% 3 8% 4 5% 6% 4 6% 7% 34%	2141
October	1st to 10th	Night	12% 6% 3 7% 4 4 4 3 5% 7% 46%	2280
	11th to 20th	Night	13% 5% 2 5% 4 4 4 3 5% 7% 49%	2280
	21st to end	Night	10% 4 1 5% 4 4 4 3 4 7% 54%	2508
November	1st to 10th	Night	12% 6% 2 7% 5% 4 4 3 6% 6% 45%	2341
	11th to 20th	Night	13% 8% 3 6% 5% 3 4 3 5% 7% 42%	2570
	21st to end	Night	11% 6% 2 5% 4 4 4 3 4 7% 50%	2598
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% 20% 22% 7%	2660
July	1st to 10th	Day	35% 9% 28% 23% 5%	4067
	11th to 20th	Day	41% 13% 29% 13% 4	4051
	21st to end	Day	44% 12% 21% 17% 6%	4324
August	1st to 10th	Day	56% 9% 22% 10% 3	3949
	11th to 20th	Day	33% 10% 19% 28% 10%	3766
	21st to end	Day	37% 7% 21% 28% 6% 1	4180
September	1st to 10th	Day	40% 11% 19% 17% 10% 2	2280
	11th to 20th	Day	45% 9% 14% 18% 12% 2	2280
	21st to end	Day	46% 6% 13% 17% 16% 2	2033
October	1st to 10th	Day	37% 5% 8% 24% 22% 5%	3160
	11th to 20th	Day	26% 4 7% 19% 23% 21%	3140
	21st to end	Day	27% 5% 8% 33% 20% 8%	3428
November	1st to 10th	Day	36% 5% 10% 21% 23% 4	1957
	11th to 20th	Day	39% 4 9% 21% 21% 6%	1826
	21st to end	Day	36% 5% 13% 23% 20% 4	1798
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	36% 11% 27% 22% 4	2762
	11th to 20th	Night	42% 13% 29% 13% 3	2786
	21st to end	Night	40% 15% 22% 15% 8%	2988
August	1st to 10th	Night	52% 9% 25% 13% 2	2910
	11th to 20th	Night	37% 10% 22% 23% 8%	3127
	21st to end	Night	35% 8% 18% 32% 6% 1	3476
September	1st to 10th	Night	42% 11% 18% 16% 12% 1	1900
	11th to 20th	Night	46% 10% 14% 17% 11% 2	1900
	21st to end	Night	49% 6% 12% 19% 13% 1	2141
October	1st to 10th	Night	39% 5% 8% 19% 24% 5%	3800
	11th to 20th	Night	28% 5% 6% 17% 18% 26%	3779
	21st to end	Night	24% 4 8% 35% 23% 6%	4120
November	1st to 10th	Night	41% 5% 11% 17% 21% 5%	2341
	11th to 20th	Night	44% 4 8% 17% 22% 5%	2570
	21st to end	Night	35% 5% 11% 24% 20% 4	2598
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% 44% 15%	490
July	1st to 10th	Day	11% 2 5% 19% 44% 20%	485
	11th to 20th	Day	8% 2 4 16% 51% 19%	484
	21st to end	Day	9% 2 8% 22% 44% 14%	532
August	1st to 10th	Day	16% 2 7% 21% 35% 20%	486
	11th to 20th	Day	9% 2 5% 22% 37% 25%	479
	21st to end	Day	13% 1 5% 21% 40% 19%	539
September	1st to 10th	Day	14% 1 9% 21% 32% 23%	490
	11th to 20th	Day	18% 2 12% 20% 35% 13%	490
	21st to end	Day	19% 3 9% 27% 28% 14%	490
October	1st to 10th	Day	18% 3 13% 23% 30% 13%	490
	11th to 20th	Day	12% 2 18% 32% 28% 8%	490
	21st to end	Day	12% 5% 18% 28% 30% 8%	539
November	1st to 10th	Day	16% 7% 18% 29% 23% 6%	495
	11th to 20th	Day	17% 6% 28% 31% 16% 2	413
	21st to end	Day	14% 6% 29% 30% 19% 3	400
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% 38% 9%	380
July	1st to 10th	Night	8% 1 5% 25% 46% 15%	535
	11th to 20th	Night	9% 2 5% 18% 47% 19%	552
	21st to end	Night	9% 2 8% 29% 43% 10%	624
August	1st to 10th	Night	11% 2 6% 27% 43% 13%	624
	11th to 20th	Night	11% 1 6% 23% 39% 21%	750
	21st to end	Night	12% 2 7% 20% 43% 16%	836
September	1st to 10th	Night	12% 2 8% 23% 34% 21%	760
	11th to 20th	Night	15% 2 11% 26% 36% 10%	760
	21st to end	Night	22% 2 11% 23% 32% 10%	760
October	1st to 10th	Night	16% 3 14% 27% 30% 11%	760
	11th to 20th	Night	15% 4 20% 30% 24% 6%	760
	21st to end	Night	12% 7% 22% 28% 24% 7%	836
November	1st to 10th	Night	15% 6% 19% 33% 22% 5%	780
	11th to 20th	Night	18% 9% 24% 31% 16% 3	800
	21st to end	Night	13% 11% 28% 26% 20% 3	800
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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