Lexington(SC)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lexington(SC) clear sky chart from 2005-11-06 to 2025-04-26.

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% 6% 2 6% 4 4 4 4 6% 8% 44%	114178
	Night	13% 6% 2 6% 4 4 4 4 5% 7% 45%	114450
Transparency	Day	37% 6% 11% 20% 20% 7%	117894
	Night	37% 6% 10% 18% 22% 8%	118873
Seeing	Day	15% 8% 24% 24% 20% 9%	15897
	Night	15% 7% 23% 32% 20% 3	26058

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% 4 2 4 3 3 3 2 4 6% 55%	4056
	11th to 20th	Day	12% 5% 2 5% 3 3 2 2 3 5% 59%	4060
	21st to end	Day	15% 7% 3 6% 5% 3 3 3 4 5% 46%	4466
February	1st to 10th	Day	14% 7% 2 6% 4 4 5% 3 5% 9% 41%	1831
	11th to 20th	Day	20% 6% 2 6% 4 3 3 3 5% 5% 44%	1948
	21st to end	Day	17% 6% 2 5% 5% 4 3 4 5% 6% 44%	1700
March	1st to 10th	Day	20% 9% 3 6% 4 4 3 3 4 5% 40%	4935
	11th to 20th	Day	7% 4 2 4 4 4 4 4 5% 6% 55%	4980
	21st to end	Day	14% 7% 2 6% 4 4 4 3 4 4 47%	5465
April	1st to 10th	Day	10% 4 2 4 4 4 4 3 6% 7% 51%	2200
	11th to 20th	Day	9% 5% 2 5% 3 4 4 4 6% 7% 49%	2334
	21st to end	Day	8% 5% 1 4 4 4 4 4 6% 8% 50%	2471
May	1st to 10th	Day	9% 6% 2 7% 4 4 5% 4 7% 10% 42%	4082
	11th to 20th	Day	15% 7% 3 7% 4 4 4 4 6% 7% 38%	4081
	21st to end	Day	6% 4 2 5% 4 5% 4 5% 7% 10% 50%	4476
June	1st to 10th	Day	9% 7% 2 7% 6% 5% 6% 5% 8% 9% 36%	2470
	11th to 20th	Day	6% 5% 2 4 5% 5% 6% 4 7% 11% 44%	2470
	21st to end	Day	4 5% 2 6% 6% 5% 7% 5% 9% 12% 39%	2470
July	1st to 10th	Day	13% 6% 3 7% 6% 5% 7% 6% 8% 10% 28%	4120
	11th to 20th	Day	5% 5% 2 7% 6% 6% 7% 6% 10% 14% 31%	4120
	21st to end	Day	9% 6% 3 9% 7% 7% 7% 7% 9% 13% 23%	4466
August	1st to 10th	Day	21% 6% 2 7% 5% 6% 6% 5% 8% 10% 24%	4104
	11th to 20th	Day	11% 6% 2 7% 5% 5% 6% 5% 8% 11% 33%	4044
	21st to end	Day	7% 4 2 5% 4 4 5% 5% 7% 11% 47%	4170
September	1st to 10th	Day	7% 6% 2 7% 5% 5% 6% 4 7% 9% 41%	2090
	11th to 20th	Day	13% 6% 2 7% 6% 5% 3 4 5% 8% 40%	2090
	21st to end	Day	16% 6% 2 6% 4 4 3 3 6% 6% 43%	2090
October	1st to 10th	Day	13% 6% 2 5% 3 4 3 3 4 7% 50%	1995
	11th to 20th	Day	11% 5% 1 4 4 3 3 2 4 6% 59%	1900
	21st to end	Day	10% 5% 2 5% 3 3 3 3 4 4 57%	2090
November	1st to 10th	Day	14% 5% 2 5% 4 3 3 2 5% 5% 53%	1957
	11th to 20th	Day	14% 5% 3 4 3 3 3 3 4 6% 53%	1878
	21st to end	Day	13% 6% 2 6% 4 3 4 3 4 6% 50%	1800
December	1st to 10th	Day	11% 6% 2 5% 4 4 4 3 5% 6% 51%	2930
	11th to 20th	Day	15% 6% 2 5% 3 4 4 3 5% 6% 47%	3373
	21st to end	Day	20% 6% 2 5% 3 3 3 3 5% 6% 45%	4466
January	1st to 10th	Night	12% 4 2 4 3 3 3 3 4 5% 57%	5889
	11th to 20th	Night	11% 5% 2 6% 4 4 4 3 5% 7% 49%	5900
	21st to end	Night	13% 8% 3 5% 4 4 3 3 4 5% 47%	6490
February	1st to 10th	Night	15% 6% 2 5% 5% 4 4 3 5% 6% 46%	2565
	11th to 20th	Night	19% 7% 2 6% 4 3 4 2 4 5% 45%	2338
	21st to end	Night	14% 5% 2 5% 4 4 4 3 5% 6% 46%	1928
March	1st to 10th	Night	19% 8% 3 6% 4 4 4 3 5% 6% 40%	4918
	11th to 20th	Night	11% 4 1 4 3 3 4 4 5% 7% 55%	4980
	21st to end	Night	13% 5% 2 5% 4 4 4 4 5% 7% 48%	5467
April	1st to 10th	Night	10% 5% 2 5% 3 4 5% 4 6% 7% 51%	2200
	11th to 20th	Night	10% 5% 2 5% 4 3 4 3 4 6% 53%	2014
	21st to end	Night	8% 4 2 5% 5% 4 4 3 6% 7% 53%	1841
May	1st to 10th	Night	9% 6% 2 6% 5% 4 5% 5% 6% 9% 43%	2813
	11th to 20th	Night	13% 6% 2 6% 5% 4 5% 4 6% 9% 40%	2812
	21st to end	Night	5% 4 2 6% 4 5% 4 5% 7% 10% 48%	3079
June	1st to 10th	Night	10% 7% 2 7% 5% 5% 6% 5% 9% 11% 33%	1710
	11th to 20th	Night	7% 6% 2 5% 6% 6% 5% 3 7% 11% 41%	1710
	21st to end	Night	5% 5% 2 7% 6% 4 7% 6% 10% 12% 34%	1710
July	1st to 10th	Night	13% 9% 3 8% 6% 5% 6% 4 8% 10% 30%	2840
	11th to 20th	Night	8% 6% 3 7% 6% 6% 6% 6% 10% 12% 29%	2840
	21st to end	Night	11% 7% 3 10% 7% 6% 6% 5% 9% 11% 23%	3087
August	1st to 10th	Night	21% 7% 3 8% 6% 5% 6% 5% 7% 9% 23%	2825
	11th to 20th	Night	11% 7% 3 8% 5% 4 6% 5% 7% 10% 34%	2785
	21st to end	Night	6% 4 2 5% 4 3 4 4 8% 11% 50%	3447
September	1st to 10th	Night	9% 5% 2 7% 5% 4 5% 5% 8% 10% 40%	2090
	11th to 20th	Night	12% 6% 2 9% 5% 6% 4 4 5% 8% 39%	2090
	21st to end	Night	16% 6% 2 6% 5% 4 4 3 6% 5% 43%	2090
October	1st to 10th	Night	13% 5% 3 6% 3 3 3 3 4 6% 52%	2182
	11th to 20th	Night	13% 4 2 4 3 3 2 3 4 5% 56%	2280
	21st to end	Night	9% 6% 2 5% 3 2 4 3 4 5% 57%	2508
November	1st to 10th	Night	13% 6% 2 5% 3 4 4 3 3 5% 53%	2341
	11th to 20th	Night	14% 7% 2 4 3 3 3 3 4 5% 52%	2519
	21st to end	Night	14% 4 2 4 4 4 4 3 5% 6% 49%	2600
December	1st to 10th	Night	12% 5% 2 5% 4 3 3 3 4 5% 55%	4250
	11th to 20th	Night	17% 7% 2 6% 3 3 3 3 4 6% 45%	4822
	21st to end	Night	19% 6% 2 6% 4 4 4 3 4 5% 43%	6490

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	32% 3 5% 23% 30% 7%	4057
	11th to 20th	Day	31% 3 4 16% 36% 10%	4060
	21st to end	Day	42% 3 4 17% 23% 12%	4466
February	1st to 10th	Day	42% 3 10% 20% 19% 6%	1831
	11th to 20th	Day	44% 4 5% 18% 24% 6%	1958
	21st to end	Day	42% 4 8% 15% 22% 9%	1700
March	1st to 10th	Day	48% 4 5% 13% 21% 10%	4935
	11th to 20th	Day	29% 4 8% 16% 26% 18%	4980
	21st to end	Day	41% 4 6% 19% 22% 8%	5465
April	1st to 10th	Day	32% 4 11% 21% 26% 7%	2200
	11th to 20th	Day	32% 5% 10% 21% 21% 10%	2334
	21st to end	Day	31% 6% 10% 27% 22% 4	2471
May	1st to 10th	Day	37% 7% 16% 25% 14% 2	4120
	11th to 20th	Day	44% 7% 11% 22% 15% 1	4085
	21st to end	Day	29% 7% 17% 22% 22% 2	4489
June	1st to 10th	Day	40% 9% 16% 22% 11% 2	2470
	11th to 20th	Day	32% 8% 17% 28% 14% 1	2470
	21st to end	Day	33% 11% 18% 22% 14% 2	2470
July	1st to 10th	Day	46% 10% 18% 17% 7% 2	4055
	11th to 20th	Day	37% 15% 26% 17% 4 1	4051
	21st to end	Day	47% 14% 18% 16% 4 1	4324
August	1st to 10th	Day	52% 10% 19% 15% 4	4091
	11th to 20th	Day	40% 11% 15% 19% 14% 1	4083
	21st to end	Day	30% 7% 15% 31% 16% 2	4170
September	1st to 10th	Day	36% 9% 14% 18% 18% 5%	2090
	11th to 20th	Day	42% 7% 11% 17% 19% 3	2090
	21st to end	Day	42% 5% 9% 20% 17% 7%	2090
October	1st to 10th	Day	33% 4 6% 17% 30% 10%	3320
	11th to 20th	Day	18% 2 4 18% 27% 30%	3140
	21st to end	Day	26% 3 4 21% 31% 15%	3428
November	1st to 10th	Day	35% 4 7% 17% 26% 12%	1957
	11th to 20th	Day	33% 3 7% 22% 24% 11%	1878
	21st to end	Day	37% 4 8% 19% 23% 9%	1800
December	1st to 10th	Day	35% 4 6% 18% 28% 9%	2930
	11th to 20th	Day	38% 4 11% 21% 20% 6%	3370
	21st to end	Day	41% 3 7% 23% 24% 2	4466
January	1st to 10th	Night	31% 3 4 19% 36% 7%	5889
	11th to 20th	Night	36% 3 5% 17% 32% 8%	5900
	21st to end	Night	40% 3 4 14% 28% 10%	6490
February	1st to 10th	Night	40% 3 7% 21% 20% 9%	2565
	11th to 20th	Night	44% 4 6% 18% 21% 8%	2339
	21st to end	Night	38% 5% 8% 17% 20% 12%	1928
March	1st to 10th	Night	45% 4 7% 11% 25% 8%	4918
	11th to 20th	Night	29% 4 7% 12% 30% 20%	4980
	21st to end	Night	36% 4 7% 20% 21% 12%	5467
April	1st to 10th	Night	33% 5% 10% 20% 23% 9%	2200
	11th to 20th	Night	32% 4 9% 21% 22% 12%	2014
	21st to end	Night	30% 5% 11% 25% 24% 5%	1841
May	1st to 10th	Night	35% 8% 14% 27% 14% 3	2840
	11th to 20th	Night	39% 9% 14% 21% 16% 1	2813
	21st to end	Night	28% 9% 12% 26% 21% 3	3087
June	1st to 10th	Night	40% 10% 16% 20% 11% 2	1710
	11th to 20th	Night	36% 10% 17% 24% 11% 2	1710
	21st to end	Night	35% 15% 19% 18% 11% 2	1710
July	1st to 10th	Night	47% 9% 22% 14% 7% 2	2795
	11th to 20th	Night	41% 14% 25% 14% 4 1	2786
	21st to end	Night	52% 14% 18% 12% 4	2988
August	1st to 10th	Night	55% 10% 18% 14% 3 1	2814
	11th to 20th	Night	41% 10% 21% 19% 8% 1	2812
	21st to end	Night	26% 8% 15% 31% 17% 2	3447
September	1st to 10th	Night	36% 9% 16% 19% 15% 5%	2090
	11th to 20th	Night	43% 7% 12% 17% 18% 4	2090
	21st to end	Night	41% 6% 12% 17% 18% 5%	2090
October	1st to 10th	Night	34% 4 8% 17% 30% 7%	3637
	11th to 20th	Night	20% 2 5% 16% 25% 32%	3779
	21st to end	Night	25% 3 5% 18% 29% 19%	4120
November	1st to 10th	Night	34% 4 7% 15% 26% 14%	2341
	11th to 20th	Night	35% 4 6% 17% 26% 13%	2519
	21st to end	Night	35% 5% 7% 18% 25% 10%	2600
December	1st to 10th	Night	34% 3 6% 16% 31% 9%	4250
	11th to 20th	Night	41% 3 10% 18% 20% 8%	4824
	21st to end	Night	44% 4 5% 23% 21% 3	6490

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	18% 17% 46% 15% 3	300
	11th to 20th	Day	20% 20% 37% 19% 5%	300
	21st to end	Day	21% 23% 37% 16% 3	330
February	1st to 10th	Day	18% 19% 37% 20% 6%	300
	11th to 20th	Day	34% 15% 34% 15% 2	300
	21st to end	Day	23% 16% 37% 18% 6%	299
March	1st to 10th	Day	19% 17% 31% 23% 9% 1	500
	11th to 20th	Day	18% 13% 41% 21% 6%	500
	21st to end	Day	18% 15% 37% 21% 9% 1	550
April	1st to 10th	Day	17% 14% 34% 24% 11%	500
	11th to 20th	Day	12% 14% 29% 26% 16% 3	492
	21st to end	Day	10% 9% 29% 29% 17% 7%	480
May	1st to 10th	Day	9% 13% 30% 27% 17% 5%	463
	11th to 20th	Day	16% 4 18% 32% 21% 9%	487
	21st to end	Day	11% 4 19% 25% 25% 17%	529
June	1st to 10th	Day	11% 2 15% 29% 31% 12%	490
	11th to 20th	Day	11% 3 14% 26% 28% 18%	490
	21st to end	Day	6% 2 14% 30% 31% 17%	490
July	1st to 10th	Day	9% 1 7% 22% 31% 29%	485
	11th to 20th	Day	8% 2 10% 19% 38% 23%	484
	21st to end	Day	6% 1 9% 28% 36% 19%	532
August	1st to 10th	Day	14% 3 12% 23% 29% 19%	486
	11th to 20th	Day	14% 2 11% 22% 34% 19%	479
	21st to end	Day	13% 3 11% 21% 30% 23%	539
September	1st to 10th	Day	9% 2 11% 29% 31% 18%	490
	11th to 20th	Day	17% 3 13% 23% 30% 13%	490
	21st to end	Day	19% 2 15% 25% 27% 12%	490
October	1st to 10th	Day	16% 3 20% 29% 23% 9%	490
	11th to 20th	Day	11% 5% 21% 31% 23% 9%	490
	21st to end	Day	12% 6% 25% 27% 22% 7%	539
November	1st to 10th	Day	18% 6% 24% 27% 19% 6%	495
	11th to 20th	Day	18% 11% 34% 26% 8% 3	378
	21st to end	Day	10% 14% 36% 25% 13% 1	300
December	1st to 10th	Day	25% 13% 36% 22% 4	300
	11th to 20th	Day	21% 10% 35% 23% 9% 1	300
	21st to end	Day	27% 14% 33% 17% 7% 2	330
January	1st to 10th	Night	19% 14% 33% 27% 7%	800
	11th to 20th	Night	19% 11% 34% 30% 6%	800
	21st to end	Night	19% 13% 37% 28% 4	880
February	1st to 10th	Night	19% 12% 31% 34% 5%	800
	11th to 20th	Night	22% 13% 34% 28% 2	783
	21st to end	Night	16% 15% 35% 29% 5%	660
March	1st to 10th	Night	18% 11% 33% 33% 6%	800
	11th to 20th	Night	17% 11% 38% 27% 8%	800
	21st to end	Night	14% 12% 38% 28% 8%	880
April	1st to 10th	Night	14% 15% 31% 30% 10%	800
	11th to 20th	Night	13% 10% 31% 31% 14%	791
	21st to end	Night	10% 8% 27% 41% 13%	667
May	1st to 10th	Night	10% 7% 30% 39% 15% 1	570
	11th to 20th	Night	11% 3 25% 37% 20% 3	561
	21st to end	Night	9% 2 15% 38% 31% 5%	617
June	1st to 10th	Night	12% 2 15% 39% 25% 5%	570
	11th to 20th	Night	10% 2 13% 34% 32% 10%	570
	21st to end	Night	7% 2 12% 38% 35% 6%	570
July	1st to 10th	Night	9% 2 10% 34% 37% 9%	555
	11th to 20th	Night	10% 1 5% 31% 45% 8%	552
	21st to end	Night	8% 1 9% 32% 44% 6%	624
August	1st to 10th	Night	12% 1 10% 27% 42% 8%	567
	11th to 20th	Night	14% 1 7% 32% 40% 6%	564
	21st to end	Night	12% 1 9% 28% 44% 7%	781
September	1st to 10th	Night	11% 2 10% 30% 42% 6%	760
	11th to 20th	Night	15% 2 12% 27% 39% 5%	760
	21st to end	Night	17% 2 14% 33% 30% 4	760
October	1st to 10th	Night	15% 3 18% 32% 28% 5%	760
	11th to 20th	Night	15% 6% 20% 33% 23% 3	760
	21st to end	Night	12% 6% 22% 33% 25% 2	836
November	1st to 10th	Night	15% 6% 23% 34% 19% 3	780
	11th to 20th	Night	16% 8% 28% 33% 14% 1	800
	21st to end	Night	15% 8% 26% 36% 15% 1	800
December	1st to 10th	Night	18% 12% 27% 33% 10% 1	800
	11th to 20th	Night	19% 9% 25% 35% 11% 2	800
	21st to end	Night	23% 12% 25% 31% 8%	880

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