Keaton Beach
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Keaton Beach clear sky chart from 2005-11-06 to 2024-10-20.

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	9% 5% 2 6% 4 4 5% 5% 7% 10% 44%	100771
	Night	9% 6% 2 6% 4 4 5% 4 7% 9% 44%	97842
Transparency	Day	18% 52% 10% 10% 7% 3	100581
	Night	20% 51% 9% 10% 7% 3	97702
Seeing	Day	10% 7% 21% 27% 23% 12%	15107
	Night	10% 6% 20% 31% 26% 7%	25106

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	14% 7% 2 5% 3 4 4 4 5% 6% 45%	2836
	11th to 20th	Day	15% 7% 3 6% 5% 4 5% 4 5% 7% 40%	2840
	21st to end	Day	12% 7% 2 8% 4 4 4 3 5% 6% 44%	3424
February	1st to 10th	Day	16% 7% 2 6% 4 3 3 3 5% 6% 43%	1900
	11th to 20th	Day	14% 6% 2 6% 3 3 4 3 4 6% 50%	1848
	21st to end	Day	13% 6% 2 5% 4 4 4 4 5% 5% 47%	1570
March	1st to 10th	Day	13% 7% 3 7% 5% 4 5% 3 6% 9% 39%	3344
	11th to 20th	Day	8% 6% 2 5% 4 4 4 4 6% 9% 48%	3480
	21st to end	Day	13% 4 1 4 3 3 4 3 6% 8% 52%	3815
April	1st to 10th	Day	7% 5% 1 5% 4 4 5% 4 6% 9% 50%	2090
	11th to 20th	Day	10% 5% 2 6% 4 4 3 3 6% 7% 50%	2126
	21st to end	Day	5% 3 1 4 3 2 3 3 5% 9% 62%	2384
May	1st to 10th	Day	5% 3 1 4 3 3 4 4 6% 9% 58%	4082
	11th to 20th	Day	8% 6% 3 6% 4 5% 4 5% 7% 9% 43%	4081
	21st to end	Day	4 3 1 4 4 3 4 4 7% 12% 55%	4476
June	1st to 10th	Day	8% 6% 2 7% 5% 5% 6% 6% 8% 11% 38%	2470
	11th to 20th	Day	6% 3 2 6% 5% 5% 7% 6% 10% 14% 36%	2470
	21st to end	Day	8% 4 2 6% 5% 5% 6% 7% 10% 12% 35%	2470
July	1st to 10th	Day	6% 3 1 4 5% 5% 8% 7% 12% 16% 32%	4120
	11th to 20th	Day	3 3 2 6% 5% 6% 8% 7% 9% 14% 38%	4120
	21st to end	Day	5% 4 2 6% 6% 6% 7% 7% 11% 13% 32%	4466
August	1st to 10th	Day	11% 3 2 5% 5% 6% 6% 6% 9% 12% 33%	3979
	11th to 20th	Day	6% 4 2 5% 4 5% 5% 5% 8% 12% 45%	3729
	21st to end	Day	8% 5% 2 7% 5% 5% 6% 6% 8% 11% 37%	4020
September	1st to 10th	Day	8% 8% 3 8% 6% 7% 7% 5% 9% 12% 28%	2090
	11th to 20th	Day	8% 5% 3 8% 6% 6% 6% 6% 9% 12% 32%	2090
	21st to end	Day	7% 6% 2 6% 4 5% 5% 4 6% 9% 45%	2090
October	1st to 10th	Day	8% 5% 2 7% 5% 4 4 4 7% 9% 46%	2090
	11th to 20th	Day	5% 3 2 3 4 4 3 3 5% 7% 62%	1990
	21st to end	Day	6% 3 1 5% 4 4 5% 4 6% 7% 55%	1980
November	1st to 10th	Day	8% 4 2 4 3 3 3 4 6% 9% 55%	1857
	11th to 20th	Day	9% 5% 2 4 3 3 4 3 6% 6% 54%	1747
	21st to end	Day	9% 5% 2 5% 4 4 4 4 5% 8% 51%	1710
December	1st to 10th	Day	11% 6% 2 6% 4 4 4 4 6% 7% 46%	1710
	11th to 20th	Day	13% 7% 2 6% 3 4 3 4 6% 7% 44%	2153
	21st to end	Day	19% 8% 3 6% 3 3 4 3 4 6% 41%	3124
January	1st to 10th	Night	15% 9% 3 5% 3 4 4 3 6% 8% 41%	4109
	11th to 20th	Night	11% 8% 3 8% 5% 4 5% 4 5% 8% 39%	4120
	21st to end	Night	15% 9% 4 7% 4 3 4 3 5% 6% 40%	4215
February	1st to 10th	Night	14% 8% 2 6% 4 3 4 3 5% 7% 45%	2280
	11th to 20th	Night	13% 8% 3 5% 4 3 3 3 4 6% 47%	2218
	21st to end	Night	11% 8% 3 7% 4 3 4 4 4 6% 47%	1884
March	1st to 10th	Night	13% 10% 3 9% 5% 5% 4 3 5% 7% 36%	3495
	11th to 20th	Night	9% 6% 2 5% 4 4 4 4 8% 10% 44%	3480
	21st to end	Night	12% 6% 2 5% 4 4 4 3 5% 7% 49%	3817
April	1st to 10th	Night	9% 6% 2 6% 5% 4 3 5% 6% 7% 48%	2090
	11th to 20th	Night	8% 4 2 6% 4 3 4 3 6% 8% 50%	2018
	21st to end	Night	5% 3 2 4 3 4 4 3 5% 8% 58%	1796
May	1st to 10th	Night	5% 3 1 4 3 3 4 4 6% 11% 57%	2813
	11th to 20th	Night	9% 5% 2 7% 4 4 4 4 5% 10% 45%	2812
	21st to end	Night	3 2 1 3 3 2 4 4 6% 11% 61%	3079
June	1st to 10th	Night	8% 5% 2 7% 5% 5% 5% 4 8% 11% 39%	1710
	11th to 20th	Night	5% 4 2 6% 5% 6% 6% 5% 9% 12% 41%	1710
	21st to end	Night	6% 6% 2 7% 5% 5% 5% 6% 10% 11% 38%	1710
July	1st to 10th	Night	5% 4 3 6% 7% 7% 8% 7% 12% 15% 26%	2840
	11th to 20th	Night	2 3 1 5% 4 4 5% 6% 9% 14% 46%	2840
	21st to end	Night	5% 5% 2 6% 6% 6% 7% 6% 10% 17% 31%	3087
August	1st to 10th	Night	8% 4 2 7% 5% 5% 6% 5% 9% 14% 36%	2943
	11th to 20th	Night	3 3 1 4 4 4 6% 5% 9% 14% 46%	3100
	21st to end	Night	7% 6% 3 8% 6% 6% 7% 6% 9% 12% 31%	3601
September	1st to 10th	Night	8% 7% 3 7% 7% 6% 6% 6% 9% 12% 28%	2090
	11th to 20th	Night	10% 6% 2 8% 5% 6% 7% 6% 8% 11% 31%	2090
	21st to end	Night	8% 5% 2 7% 4 4 5% 4 7% 9% 44%	2090
October	1st to 10th	Night	8% 6% 3 6% 5% 6% 4 4 5% 7% 47%	2090
	11th to 20th	Night	6% 4 2 4 3 4 4 3 5% 6% 59%	2174
	21st to end	Night	7% 5% 2 5% 4 4 5% 3 6% 6% 52%	2376
November	1st to 10th	Night	6% 4 1 6% 5% 5% 4 4 5% 7% 53%	2221
	11th to 20th	Night	10% 5% 2 5% 4 3 3 4 5% 6% 52%	2430
	21st to end	Night	9% 6% 2 6% 4 3 4 4 6% 7% 48%	2470
December	1st to 10th	Night	11% 6% 2 5% 5% 4 4 4 6% 8% 45%	2470
	11th to 20th	Night	12% 7% 2 7% 4 3 4 3 5% 7% 47%	3042
	21st to end	Night	15% 8% 3 6% 4 4 4 3 6% 6% 40%	4532

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	26% 38% 5% 10% 13% 8%	2837
	11th to 20th	Day	32% 39% 4 6% 8% 11%	2840
	21st to end	Day	21% 44% 6% 9% 13% 7%	3424
February	1st to 10th	Day	14% 65% 4 6% 6% 5%	1900
	11th to 20th	Day	11% 65% 3 9% 10% 3	1858
	21st to end	Day	13% 65% 4 5% 9% 4	1570
March	1st to 10th	Day	31% 45% 7% 11% 5% 2	3344
	11th to 20th	Day	19% 45% 9% 7% 15% 5%	3480
	21st to end	Day	19% 42% 7% 19% 8% 7%	3815
April	1st to 10th	Day	11% 67% 5% 6% 6% 4	2090
	11th to 20th	Day	13% 66% 3 8% 8% 3	2126
	21st to end	Day	9% 65% 5% 10% 8% 3	2384
May	1st to 10th	Day	13% 47% 11% 16% 9% 4	4120
	11th to 20th	Day	25% 43% 8% 15% 8% 1	4085
	21st to end	Day	9% 43% 14% 20% 12% 1	4489
June	1st to 10th	Day	14% 69% 8% 7% 1	2470
	11th to 20th	Day	13% 70% 8% 7% 3	2470
	21st to end	Day	11% 69% 9% 9% 3	2470
July	1st to 10th	Day	22% 47% 25% 5%	4055
	11th to 20th	Day	19% 46% 28% 7%	4051
	21st to end	Day	27% 48% 18% 6%	4324
August	1st to 10th	Day	27% 45% 14% 11% 4	3966
	11th to 20th	Day	14% 44% 18% 17% 8%	3765
	21st to end	Day	22% 45% 16% 15% 2	4020
September	1st to 10th	Day	20% 63% 8% 5% 3 1	2090
	11th to 20th	Day	16% 63% 9% 7% 5%	2090
	21st to end	Day	14% 62% 7% 10% 6% 1	2090
October	1st to 10th	Day	16% 62% 6% 6% 8% 2	2090
	11th to 20th	Day	6% 60% 3 12% 14% 4	1990
	21st to end	Day	10% 63% 5% 7% 10% 6%	1980
November	1st to 10th	Day	12% 60% 7% 8% 8% 5%	1857
	11th to 20th	Day	15% 60% 3 7% 11% 4	1747
	21st to end	Day	14% 60% 3 11% 10% 3	1710
December	1st to 10th	Day	16% 61% 6% 9% 7% 2	1710
	11th to 20th	Day	20% 49% 3 8% 13% 8%	2150
	21st to end	Day	33% 37% 3 14% 9% 3	3124
January	1st to 10th	Night	28% 37% 4 7% 11% 12%	4109
	11th to 20th	Night	32% 37% 5% 8% 12% 7%	4120
	21st to end	Night	26% 42% 6% 8% 13% 5%	4215
February	1st to 10th	Night	14% 66% 3 6% 7% 3	2280
	11th to 20th	Night	13% 64% 3 8% 8% 3	2219
	21st to end	Night	13% 65% 5% 6% 7% 5%	1884
March	1st to 10th	Night	37% 44% 6% 7% 4 2	3495
	11th to 20th	Night	22% 42% 9% 12% 11% 5%	3480
	21st to end	Night	25% 41% 4 13% 11% 6%	3817
April	1st to 10th	Night	13% 66% 4 8% 5% 5%	2090
	11th to 20th	Night	11% 67% 3 10% 6% 4	2018
	21st to end	Night	9% 66% 3 11% 8% 3	1796
May	1st to 10th	Night	11% 46% 14% 18% 7% 4	2840
	11th to 20th	Night	23% 43% 11% 15% 7% 1	2813
	21st to end	Night	8% 41% 13% 27% 10% 1	3087
June	1st to 10th	Night	13% 67% 9% 9% 2	1710
	11th to 20th	Night	12% 69% 10% 7% 2	1710
	21st to end	Night	10% 67% 12% 8% 3	1710
July	1st to 10th	Night	29% 44% 22% 5%	2795
	11th to 20th	Night	12% 44% 36% 7% 1	2786
	21st to end	Night	25% 45% 24% 5% 1	2988
August	1st to 10th	Night	25% 43% 18% 10% 3	2932
	11th to 20th	Night	11% 42% 22% 20% 5%	3130
	21st to end	Night	25% 44% 18% 9% 3	3601
September	1st to 10th	Night	19% 63% 8% 5% 3 1	2090
	11th to 20th	Night	16% 63% 10% 8% 3 1	2090
	21st to end	Night	14% 60% 8% 10% 7% 1	2090
October	1st to 10th	Night	16% 61% 7% 8% 7% 2	2090
	11th to 20th	Night	8% 60% 3 12% 12% 4	2174
	21st to end	Night	10% 63% 5% 7% 10% 5%	2376
November	1st to 10th	Night	16% 59% 5% 9% 5% 5%	2221
	11th to 20th	Night	16% 60% 5% 7% 8% 5%	2430
	21st to end	Night	14% 60% 4 9% 9% 4	2470
December	1st to 10th	Night	17% 61% 5% 10% 6% 2	2470
	11th to 20th	Night	19% 49% 4 6% 14% 8%	3044
	21st to end	Night	32% 39% 5% 13% 10% 2	4532

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	11% 14% 48% 19% 7% 1	270
	11th to 20th	Day	10% 14% 40% 27% 7% 2	270
	21st to end	Day	19% 20% 44% 14% 4	297
February	1st to 10th	Day	17% 17% 37% 21% 9%	270
	11th to 20th	Day	20% 16% 33% 24% 7%	270
	21st to end	Day	12% 15% 45% 21% 7%	225
March	1st to 10th	Day	9% 16% 36% 28% 10%	403
	11th to 20th	Day	14% 12% 33% 27% 12% 1	460
	21st to end	Day	11% 13% 33% 28% 14% 1	506
April	1st to 10th	Day	13% 11% 33% 27% 14% 2	460
	11th to 20th	Day	12% 10% 32% 28% 16% 3	452
	21st to end	Day	6% 6% 30% 35% 18% 4	460
May	1st to 10th	Day	6% 6% 25% 35% 19% 8%	463
	11th to 20th	Day	8% 4 19% 33% 26% 10%	487
	21st to end	Day	8% 3 12% 29% 32% 16%	529
June	1st to 10th	Day	10% 3 12% 32% 29% 14%	490
	11th to 20th	Day	7% 3 15% 21% 32% 22%	490
	21st to end	Day	6% 2 7% 28% 34% 24%	490
July	1st to 10th	Day	8% 2 7% 20% 32% 31%	485
	11th to 20th	Day	5% 2 4 19% 39% 32%	484
	21st to end	Day	7% 2 5% 23% 38% 26%	532
August	1st to 10th	Day	12% 3 8% 18% 34% 26%	486
	11th to 20th	Day	9% 2 3 17% 40% 28%	479
	21st to end	Day	7% 2 6% 24% 38% 22%	539
September	1st to 10th	Day	10% 5% 9% 20% 33% 23%	490
	11th to 20th	Day	10% 2 12% 30% 31% 14%	490
	21st to end	Day	9% 4 12% 27% 34% 14%	490
October	1st to 10th	Day	10% 5% 22% 33% 24% 6%	490
	11th to 20th	Day	5% 4 22% 33% 26% 10%	486
	21st to end	Day	8% 5% 22% 40% 22% 4	495
November	1st to 10th	Day	11% 7% 22% 39% 16% 5%	455
	11th to 20th	Day	12% 8% 31% 35% 12% 2	307
	21st to end	Day	10% 9% 38% 33% 9% 1	270
December	1st to 10th	Day	12% 12% 34% 29% 9% 4	270
	11th to 20th	Day	17% 11% 34% 30% 7% 1	270
	21st to end	Day	15% 10% 35% 25% 12% 2	297
January	1st to 10th	Night	16% 10% 34% 28% 11% 1	760
	11th to 20th	Night	11% 9% 29% 35% 15% 1	760
	21st to end	Night	19% 10% 34% 29% 8%	836
February	1st to 10th	Night	17% 9% 28% 33% 12%	760
	11th to 20th	Night	18% 9% 31% 30% 11% 1	743
	21st to end	Night	14% 9% 28% 41% 7%	628
March	1st to 10th	Night	12% 8% 30% 38% 12% 1	760
	11th to 20th	Night	13% 8% 23% 37% 19% 1	760
	21st to end	Night	10% 8% 29% 36% 16% 1	836
April	1st to 10th	Night	12% 9% 24% 38% 17% 1	760
	11th to 20th	Night	8% 8% 26% 39% 18% 1	706
	21st to end	Night	6% 4 24% 39% 25% 2	570
May	1st to 10th	Night	5% 4 20% 40% 27% 4	570
	11th to 20th	Night	7% 3 17% 36% 33% 4	561
	21st to end	Night	5% 2 9% 35% 43% 7%	617
June	1st to 10th	Night	9% 3 8% 32% 40% 8%	570
	11th to 20th	Night	4 4 7% 29% 39% 18%	570
	21st to end	Night	7% 2 6% 21% 45% 19%	570
July	1st to 10th	Night	5% 2 4 15% 45% 29%	555
	11th to 20th	Night	4 1 2 14% 45% 34%	552
	21st to end	Night	5% 1 2 13% 53% 25%	624
August	1st to 10th	Night	5% 2 4 15% 49% 26%	567
	11th to 20th	Night	5% 2 2 12% 53% 26%	564
	21st to end	Night	9% 3 7% 24% 39% 18%	700
September	1st to 10th	Night	10% 3 7% 22% 41% 17%	760
	11th to 20th	Night	9% 3 10% 28% 40% 9%	760
	21st to end	Night	11% 3 11% 29% 39% 7%	760
October	1st to 10th	Night	11% 3 20% 36% 26% 4	760
	11th to 20th	Night	6% 4 19% 39% 29% 2	759
	21st to end	Night	10% 3 20% 41% 24% 2	792
November	1st to 10th	Night	9% 6% 28% 36% 20% 2	740
	11th to 20th	Night	13% 7% 26% 36% 17% 2	760
	21st to end	Night	12% 6% 28% 38% 16%	760
December	1st to 10th	Night	14% 6% 25% 34% 19% 2	760
	11th to 20th	Night	14% 7% 30% 31% 16% 1	760
	21st to end	Night	15% 9% 26% 34% 16%	836

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