Charles Towne Landing State Historic Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Charles Towne Landing State Historic Site clear sky chart from 2005-11-06 to 2024-11-11.

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% 5% 5% 5% 4 7% 9% 41%	101174
	Night	11% 6% 2 6% 4 4 4 4 6% 8% 43%	97949
Transparency	Day	37% 9% 15% 19% 15% 5%	104837
	Night	36% 9% 13% 19% 17% 7%	102425
Seeing	Day	12% 6% 23% 28% 23% 9%	15587
	Night	12% 6% 22% 31% 24% 5%	25671

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% 6% 2 5% 4 4 5% 3 6% 9% 43%	2836
	11th to 20th	Day	12% 6% 2 5% 5% 4 3 3 5% 9% 46%	2840
	21st to end	Day	14% 9% 3 6% 4 3 3 2 4 6% 44%	3124
February	1st to 10th	Day	14% 7% 1 6% 5% 5% 5% 4 6% 7% 41%	1710
	11th to 20th	Day	17% 7% 2 6% 3 3 3 3 4 5% 46%	1810
	21st to end	Day	13% 7% 3 6% 4 4 4 4 5% 5% 46%	1718
March	1st to 10th	Day	21% 10% 4 8% 4 3 3 3 5% 5% 34%	3435
	11th to 20th	Day	8% 4 2 4 3 4 4 4 6% 8% 53%	3480
	21st to end	Day	17% 6% 2 6% 4 4 4 3 5% 6% 45%	3815
April	1st to 10th	Day	8% 5% 2 4 4 4 4 4 5% 7% 53%	2113
	11th to 20th	Day	9% 4 2 5% 3 4 5% 3 6% 8% 51%	2254
	21st to end	Day	5% 4 1 4 3 3 3 4 7% 9% 56%	2280
May	1st to 10th	Day	6% 4 2 6% 5% 5% 5% 6% 7% 11% 43%	4015
	11th to 20th	Day	12% 7% 3 7% 4 4 5% 4 7% 8% 38%	4081
	21st to end	Day	6% 4 2 5% 3 4 5% 5% 8% 12% 47%	4476
June	1st to 10th	Day	8% 7% 2 7% 6% 6% 8% 6% 8% 10% 32%	2470
	11th to 20th	Day	7% 5% 2 5% 5% 6% 5% 6% 9% 12% 38%	2470
	21st to end	Day	6% 5% 2 7% 5% 6% 7% 6% 10% 12% 33%	2470
July	1st to 10th	Day	13% 6% 3 7% 6% 6% 7% 6% 8% 11% 27%	4120
	11th to 20th	Day	5% 5% 2 7% 6% 6% 8% 7% 10% 13% 30%	4120
	21st to end	Day	6% 5% 3 8% 7% 7% 8% 7% 10% 14% 26%	4466
August	1st to 10th	Day	19% 7% 2 8% 5% 5% 6% 5% 9% 10% 23%	4104
	11th to 20th	Day	6% 6% 3 7% 6% 6% 7% 5% 9% 12% 33%	3921
	21st to end	Day	10% 6% 3 8% 5% 6% 5% 5% 7% 10% 35%	4180
September	1st to 10th	Day	12% 6% 2 7% 5% 5% 6% 6% 6% 10% 35%	2175
	11th to 20th	Day	12% 8% 3 8% 5% 5% 6% 5% 7% 7% 34%	2090
	21st to end	Day	14% 7% 3 6% 4 5% 4 4 6% 9% 39%	2090
October	1st to 10th	Day	12% 7% 2 6% 4 4 4 3 5% 5% 48%	1933
	11th to 20th	Day	7% 4 2 4 3 3 3 3 5% 8% 57%	1900
	21st to end	Day	9% 5% 2 5% 4 4 3 2 4 6% 56%	2090
November	1st to 10th	Day	10% 6% 2 4 3 3 4 3 5% 6% 52%	1957
	11th to 20th	Day	11% 7% 2 6% 5% 4 4 3 4 6% 48%	1900
	21st to end	Day	13% 6% 1 4 4 3 3 3 5% 7% 51%	1744
December	1st to 10th	Day	13% 7% 2 7% 4 4 5% 5% 5% 6% 42%	1710
	11th to 20th	Day	15% 5% 2 4 3 3 3 2 4 6% 54%	2153
	21st to end	Day	17% 9% 3 6% 3 3 4 3 5% 5% 43%	3124
January	1st to 10th	Night	12% 6% 2 6% 4 5% 5% 4 6% 6% 43%	4109
	11th to 20th	Night	11% 8% 2 7% 5% 4 5% 4 5% 8% 42%	4120
	21st to end	Night	13% 9% 3 7% 4 3 3 3 4 6% 44%	4532
February	1st to 10th	Night	14% 7% 2 6% 4 4 4 3 6% 6% 43%	2470
	11th to 20th	Night	16% 7% 2 6% 4 4 4 3 5% 6% 43%	2252
	21st to end	Night	12% 8% 3 7% 5% 4 4 3 6% 6% 42%	1733
March	1st to 10th	Night	19% 13% 4 7% 5% 3 4 3 3 5% 33%	3418
	11th to 20th	Night	10% 6% 2 6% 3 4 3 4 5% 8% 49%	3480
	21st to end	Night	15% 6% 2 5% 3 3 4 3 6% 7% 45%	3817
April	1st to 10th	Night	9% 5% 2 6% 4 4 3 4 5% 7% 51%	2066
	11th to 20th	Night	11% 4 1 5% 3 4 4 3 5% 7% 51%	1875
	21st to end	Night	7% 4 2 4 4 4 4 3 5% 8% 54%	1900
May	1st to 10th	Night	5% 4 2 4 4 4 5% 5% 8% 10% 49%	2894
	11th to 20th	Night	11% 6% 2 6% 4 4 4 4 6% 8% 44%	2812
	21st to end	Night	6% 3 2 5% 4 4 4 4 7% 9% 52%	3079
June	1st to 10th	Night	8% 6% 2 7% 5% 6% 6% 5% 8% 13% 34%	1710
	11th to 20th	Night	6% 5% 2 6% 5% 5% 6% 6% 9% 12% 39%	1710
	21st to end	Night	5% 5% 2 6% 6% 7% 6% 6% 9% 13% 35%	1710
July	1st to 10th	Night	10% 6% 3 7% 6% 6% 7% 6% 9% 11% 31%	2840
	11th to 20th	Night	6% 5% 2 7% 6% 6% 7% 6% 8% 14% 33%	2840
	21st to end	Night	6% 6% 2 7% 6% 6% 7% 6% 10% 15% 29%	3087
August	1st to 10th	Night	17% 7% 3 7% 4 4 5% 5% 9% 13% 25%	2825
	11th to 20th	Night	7% 5% 2 7% 5% 6% 6% 6% 8% 12% 36%	2874
	21st to end	Night	7% 5% 2 7% 5% 5% 4 4 6% 9% 45%	3476
September	1st to 10th	Night	10% 6% 2 8% 6% 6% 5% 5% 7% 10% 36%	2001
	11th to 20th	Night	10% 7% 2 7% 5% 6% 6% 4 7% 8% 38%	2090
	21st to end	Night	14% 6% 3 7% 4 4 4 4 7% 8% 39%	2090
October	1st to 10th	Night	13% 5% 2 5% 4 4 4 3 5% 8% 47%	2247
	11th to 20th	Night	9% 3 2 4 4 2 3 4 5% 6% 58%	2280
	21st to end	Night	9% 5% 2 6% 3 3 3 2 6% 6% 56%	2508
November	1st to 10th	Night	10% 6% 2 5% 3 3 3 3 4 6% 54%	2341
	11th to 20th	Night	14% 6% 2 5% 4 3 2 3 5% 6% 50%	2287
	21st to end	Night	11% 6% 2 6% 4 4 4 4 6% 7% 46%	2432
December	1st to 10th	Night	13% 7% 2 7% 4 4 5% 4 6% 6% 41%	2470
	11th to 20th	Night	16% 6% 2 5% 3 3 3 3 4 6% 49%	3042
	21st to end	Night	18% 8% 2 6% 5% 4 4 4 4 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	35% 7% 10% 20% 21% 8%	2837
	11th to 20th	Day	35% 5% 8% 18% 24% 10%	2840
	21st to end	Day	41% 6% 7% 17% 19% 10%	3124
February	1st to 10th	Day	41% 6% 10% 19% 18% 6%	1710
	11th to 20th	Day	41% 5% 8% 16% 22% 8%	1820
	21st to end	Day	39% 6% 10% 18% 16% 10%	1718
March	1st to 10th	Day	49% 8% 8% 14% 13% 7%	3435
	11th to 20th	Day	27% 8% 13% 16% 23% 13%	3480
	21st to end	Day	39% 7% 9% 18% 21% 6%	3815
April	1st to 10th	Day	29% 7% 14% 21% 21% 9%	2113
	11th to 20th	Day	29% 6% 13% 23% 18% 10%	2254
	21st to end	Day	23% 7% 15% 29% 20% 5%	2280
May	1st to 10th	Day	30% 13% 18% 25% 11% 3	4052
	11th to 20th	Day	39% 9% 16% 24% 11% 1	4085
	21st to end	Day	25% 11% 20% 27% 17%	4489
June	1st to 10th	Day	41% 13% 18% 18% 10%	2470
	11th to 20th	Day	33% 12% 22% 26% 7%	2470
	21st to end	Day	36% 15% 23% 18% 7% 1	2470
July	1st to 10th	Day	46% 13% 18% 19% 4	4055
	11th to 20th	Day	39% 16% 32% 9% 3	4051
	21st to end	Day	42% 16% 26% 15% 1	4324
August	1st to 10th	Day	51% 13% 23% 11% 2	4091
	11th to 20th	Day	38% 14% 20% 21% 8%	3960
	21st to end	Day	39% 10% 17% 31% 3	4180
September	1st to 10th	Day	41% 13% 18% 14% 12% 3	2175
	11th to 20th	Day	44% 12% 15% 17% 11% 3	2090
	21st to end	Day	41% 8% 14% 20% 14% 3	2090
October	1st to 10th	Day	41% 5% 8% 14% 27% 5%	3206
	11th to 20th	Day	17% 4 7% 14% 32% 27%	3140
	21st to end	Day	24% 5% 8% 18% 37% 8%	3428
November	1st to 10th	Day	31% 6% 12% 16% 25% 11%	1957
	11th to 20th	Day	37% 5% 8% 18% 21% 11%	1900
	21st to end	Day	33% 5% 10% 23% 22% 7%	1744
December	1st to 10th	Day	40% 8% 11% 20% 13% 8%	1710
	11th to 20th	Day	33% 4 8% 22% 27% 6%	2150
	21st to end	Day	42% 6% 8% 18% 23% 4	3124
January	1st to 10th	Night	37% 7% 8% 16% 22% 10%	4109
	11th to 20th	Night	39% 6% 8% 18% 24% 6%	4120
	21st to end	Night	41% 6% 7% 13% 23% 10%	4532
February	1st to 10th	Night	40% 5% 9% 19% 19% 8%	2470
	11th to 20th	Night	42% 6% 9% 14% 19% 10%	2253
	21st to end	Night	42% 5% 11% 17% 14% 11%	1733
March	1st to 10th	Night	52% 7% 10% 13% 11% 7%	3418
	11th to 20th	Night	32% 7% 11% 17% 22% 12%	3480
	21st to end	Night	37% 8% 11% 20% 18% 7%	3817
April	1st to 10th	Night	32% 7% 13% 19% 20% 9%	2066
	11th to 20th	Night	32% 6% 9% 22% 20% 11%	1875
	21st to end	Night	26% 8% 14% 26% 22% 5%	1900
May	1st to 10th	Night	25% 12% 20% 28% 12% 3	2922
	11th to 20th	Night	35% 11% 14% 25% 14% 1	2813
	21st to end	Night	25% 11% 17% 28% 18% 1	3087
June	1st to 10th	Night	37% 13% 21% 20% 9%	1710
	11th to 20th	Night	32% 13% 22% 25% 7% 1	1710
	21st to end	Night	35% 14% 26% 21% 4 1	1710
July	1st to 10th	Night	42% 13% 19% 23% 3 1	2795
	11th to 20th	Night	39% 16% 32% 9% 3	2786
	21st to end	Night	39% 17% 24% 17% 2	2988
August	1st to 10th	Night	46% 15% 25% 11% 2	2814
	11th to 20th	Night	36% 13% 23% 22% 6%	2901
	21st to end	Night	35% 10% 17% 35% 3	3476
September	1st to 10th	Night	41% 12% 17% 17% 11% 2	2001
	11th to 20th	Night	41% 11% 17% 18% 12% 2	2090
	21st to end	Night	40% 9% 15% 21% 13% 2	2090
October	1st to 10th	Night	36% 6% 10% 16% 26% 7%	3754
	11th to 20th	Night	15% 5% 6% 14% 27% 33%	3779
	21st to end	Night	25% 5% 6% 19% 29% 15%	4120
November	1st to 10th	Night	31% 6% 9% 18% 24% 12%	2341
	11th to 20th	Night	36% 5% 8% 18% 22% 12%	2287
	21st to end	Night	36% 5% 10% 18% 21% 10%	2432
December	1st to 10th	Night	41% 8% 13% 15% 17% 6%	2470
	11th to 20th	Night	37% 5% 9% 16% 27% 6%	3044
	21st to end	Night	43% 6% 7% 19% 20% 4	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	13% 9% 46% 27% 4	270
	11th to 20th	Day	10% 11% 40% 26% 13% 2	270
	21st to end	Day	20% 16% 39% 21% 3 1	297
February	1st to 10th	Day	16% 14% 37% 25% 8%	270
	11th to 20th	Day	24% 11% 37% 23% 4	270
	21st to end	Day	11% 12% 44% 25% 7% 1	373
March	1st to 10th	Day	13% 13% 34% 28% 12%	460
	11th to 20th	Day	13% 9% 39% 30% 8% 2	460
	21st to end	Day	13% 9% 40% 25% 10% 2	506
April	1st to 10th	Day	12% 13% 35% 27% 12% 2	460
	11th to 20th	Day	8% 12% 30% 25% 18% 6%	452
	21st to end	Day	5% 7% 28% 32% 20% 8%	460
May	1st to 10th	Day	5% 9% 32% 30% 18% 7%	463
	11th to 20th	Day	11% 4 21% 31% 24% 9%	487
	21st to end	Day	10% 3 13% 34% 27% 13%	529
June	1st to 10th	Day	8% 3 16% 35% 26% 12%	490
	11th to 20th	Day	9% 4 15% 26% 28% 19%	490
	21st to end	Day	6% 2 12% 31% 33% 15%	490
July	1st to 10th	Day	7% 2 5% 24% 43% 19%	485
	11th to 20th	Day	7% 2 5% 23% 43% 20%	484
	21st to end	Day	6% 2 6% 33% 40% 12%	532
August	1st to 10th	Day	12% 1 9% 27% 35% 16%	486
	11th to 20th	Day	6% 3 6% 24% 41% 20%	479
	21st to end	Day	13% 2 9% 23% 34% 19%	539
September	1st to 10th	Day	11% 5% 6% 25% 37% 16%	490
	11th to 20th	Day	15% 3 12% 30% 29% 10%	490
	21st to end	Day	16% 1 12% 30% 28% 13%	490
October	1st to 10th	Day	18% 4 20% 30% 19% 9%	490
	11th to 20th	Day	9% 3 22% 31% 25% 9%	490
	21st to end	Day	11% 4 22% 32% 27% 5%	539
November	1st to 10th	Day	15% 5% 26% 28% 21% 5%	495
	11th to 20th	Day	16% 5% 34% 27% 16% 2	460
	21st to end	Day	12% 8% 29% 33% 16% 2	304
December	1st to 10th	Day	18% 8% 30% 32% 12% 1	270
	11th to 20th	Day	17% 10% 34% 26% 10% 3	270
	21st to end	Day	22% 10% 30% 27% 11% 1	297
January	1st to 10th	Night	13% 10% 36% 34% 7%	760
	11th to 20th	Night	14% 10% 31% 32% 12%	760
	21st to end	Night	17% 10% 40% 29% 5%	836
February	1st to 10th	Night	17% 9% 33% 32% 10%	760
	11th to 20th	Night	18% 10% 34% 32% 6%	743
	21st to end	Night	15% 9% 34% 34% 7% 1	628
March	1st to 10th	Night	12% 8% 33% 36% 11%	760
	11th to 20th	Night	13% 9% 30% 36% 11% 1	760
	21st to end	Night	12% 7% 35% 31% 14% 1	836
April	1st to 10th	Night	11% 10% 30% 33% 15% 1	760
	11th to 20th	Night	12% 9% 24% 31% 21% 3	751
	21st to end	Night	9% 5% 25% 37% 23% 1	760
May	1st to 10th	Night	7% 5% 23% 36% 24% 4	626
	11th to 20th	Night	10% 3 20% 30% 30% 7%	561
	21st to end	Night	8% 1 11% 28% 40% 12%	617
June	1st to 10th	Night	9% 3 11% 36% 33% 8%	570
	11th to 20th	Night	6% 2 10% 26% 41% 16%	570
	21st to end	Night	6% 2 9% 31% 40% 12%	570
July	1st to 10th	Night	8% 2 6% 24% 48% 12%	555
	11th to 20th	Night	9% 1 4 21% 48% 17%	552
	21st to end	Night	5% 3 4 31% 47% 10%	624
August	1st to 10th	Night	12% 2 4 23% 46% 14%	567
	11th to 20th	Night	8% 2 7% 25% 43% 14%	614
	21st to end	Night	11% 2 8% 23% 39% 17%	836
September	1st to 10th	Night	10% 3 9% 26% 42% 11%	760
	11th to 20th	Night	11% 3 9% 31% 37% 10%	760
	21st to end	Night	16% 2 10% 28% 35% 9%	760
October	1st to 10th	Night	15% 2 16% 31% 28% 8%	760
	11th to 20th	Night	9% 4 22% 33% 26% 5%	760
	21st to end	Night	11% 5% 22% 31% 27% 5%	836
November	1st to 10th	Night	13% 5% 23% 35% 22% 3	780
	11th to 20th	Night	15% 7% 25% 35% 16% 2	763
	21st to end	Night	12% 9% 24% 34% 18% 3	760
December	1st to 10th	Night	16% 6% 30% 33% 14% 1	760
	11th to 20th	Night	18% 7% 28% 29% 17% 1	760
	21st to end	Night	20% 10% 29% 29% 11% 1	836

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