Lewisville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lewisville clear sky chart from 2005-11-06 to 2024-03-06.

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	14% 6% 2 5% 5% 3 5% 5% 5% 7% 44%	79051
	Night	13% 5% 2 4 4 2 3 4 5% 7% 51%	80524
Transparency	Day	39% 6% 10% 21% 19% 5%	78775
	Night	34% 5% 10% 21% 23% 8%	80320
Seeing	Day	15% 9% 23% 26% 21% 6%	14233
	Night	15% 8% 25% 31% 18% 2	24230

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	20% 11% 3 5% 3 2 3 2 3 4 45%	2847
	11th to 20th	Day	20% 7% 2 3 3 2 3 3 4 5% 48%	2850
	21st to end	Day	25% 7% 2 4 3 2 2 2 3 4 45%	3135
February	1st to 10th	Day	25% 8% 3 5% 3 3 3 3 3 5% 39%	1710
	11th to 20th	Day	22% 8% 3 5% 4 2 3 3 4 5% 41%	1766
	21st to end	Day	27% 7% 3 5% 4 2 3 2 4 4 39%	1727
March	1st to 10th	Day	19% 8% 3 5% 4 2 3 3 4 6% 42%	2035
	11th to 20th	Day	19% 6% 3 6% 5% 2 4 4 5% 6% 39%	1980
	21st to end	Day	17% 6% 3 6% 4 3 4 3 5% 6% 42%	2178
April	1st to 10th	Day	14% 6% 2 5% 6% 3 5% 4 5% 7% 43%	2087
	11th to 20th	Day	18% 5% 2 5% 5% 3 4 4 3 7% 44%	2134
	21st to end	Day	14% 6% 2 5% 5% 2 4 5% 5% 7% 44%	2160
May	1st to 10th	Day	15% 6% 3 5% 5% 3 5% 4 4 7% 42%	2168
	11th to 20th	Day	10% 7% 3 5% 6% 3 5% 6% 6% 8% 41%	2302
	21st to end	Day	10% 5% 3 6% 6% 3 7% 6% 6% 9% 38%	2531
June	1st to 10th	Day	7% 4 2 7% 5% 4 6% 7% 6% 10% 42%	2340
	11th to 20th	Day	7% 4 2 5% 6% 4 7% 7% 6% 10% 43%	2340
	21st to end	Day	5% 4 2 4 4 4 6% 6% 7% 10% 48%	2340
July	1st to 10th	Day	9% 4 2 6% 8% 4 7% 7% 8% 12% 32%	2340
	11th to 20th	Day	6% 3 1 5% 6% 4 6% 7% 8% 9% 44%	2340
	21st to end	Day	7% 3 2 5% 5% 4 7% 7% 8% 11% 41%	2546
August	1st to 10th	Day	4 3 2 4 5% 5% 6% 7% 8% 11% 46%	2328
	11th to 20th	Day	9% 4 2 5% 5% 3 5% 5% 6% 9% 46%	2172
	21st to end	Day	8% 5% 2 5% 6% 3 7% 7% 7% 9% 41%	2376
September	1st to 10th	Day	10% 5% 2 4 4 3 5% 5% 6% 8% 48%	2160
	11th to 20th	Day	12% 5% 2 5% 6% 3 5% 5% 5% 8% 44%	2044
	21st to end	Day	7% 3 2 4 4 3 4 4 5% 7% 56%	1932
October	1st to 10th	Day	8% 4 1 4 4 3 3 5% 5% 6% 58%	1800
	11th to 20th	Day	14% 6% 2 4 4 2 2 3 3 5% 55%	1800
	21st to end	Day	18% 5% 2 4 3 2 2 4 3 5% 52%	1980
November	1st to 10th	Day	13% 6% 2 4 3 3 3 3 5% 7% 52%	1858
	11th to 20th	Day	10% 5% 2 5% 5% 2 4 3 4 5% 54%	1900
	21st to end	Day	20% 6% 2 5% 4 3 3 3 3 4 46%	1839
December	1st to 10th	Day	17% 8% 3 5% 5% 2 4 3 4 4 46%	1710
	11th to 20th	Day	16% 9% 3 6% 5% 3 5% 3 4 5% 42%	2161
	21st to end	Day	16% 8% 3 6% 5% 3 4 4 4 6% 40%	3135
January	1st to 10th	Night	17% 8% 2 5% 4 2 2 3 3 4 49%	4108
	11th to 20th	Night	19% 5% 2 3 3 2 3 2 3 3 54%	4120
	21st to end	Night	23% 9% 2 5% 3 2 2 3 2 4 45%	4532
February	1st to 10th	Night	19% 8% 3 5% 3 2 2 3 5% 5% 46%	2470
	11th to 20th	Night	22% 7% 2 4 5% 2 3 4 4 4 43%	2314
	21st to end	Night	20% 7% 2 5% 4 2 2 2 3 4 47%	1727
March	1st to 10th	Night	18% 6% 2 4 4 2 4 4 4 7% 45%	2041
	11th to 20th	Night	16% 7% 3 4 4 3 4 4 5% 7% 43%	1980
	21st to end	Night	16% 5% 3 4 5% 2 4 4 4 6% 47%	2178
April	1st to 10th	Night	11% 4 3 5% 4 3 4 4 5% 6% 51%	1872
	11th to 20th	Night	11% 5% 2 5% 4 3 4 4 5% 7% 49%	1775
	21st to end	Night	10% 4 3 5% 5% 2 4 3 4 9% 51%	1800
May	1st to 10th	Night	10% 5% 2 5% 4 3 4 4 5% 8% 50%	1787
	11th to 20th	Night	11% 5% 2 5% 4 3 4 5% 5% 8% 48%	1593
	21st to end	Night	8% 4 2 4 5% 3 5% 5% 7% 10% 46%	1745
June	1st to 10th	Night	4 4 2 4 4 3 4 7% 7% 11% 51%	1620
	11th to 20th	Night	5% 3 2 3 4 2 4 3 5% 7% 61%	1620
	21st to end	Night	4 3 2 4 4 3 5% 5% 6% 9% 57%	1620
July	1st to 10th	Night	5% 3 3 4 5% 4 5% 7% 7% 12% 46%	1620
	11th to 20th	Night	4 2 1 2 3 3 3 5% 6% 13% 57%	1620
	21st to end	Night	3 2 1 4 4 2 6% 6% 7% 11% 53%	1772
August	1st to 10th	Night	3 1 1 2 4 3 3 5% 7% 11% 59%	1611
	11th to 20th	Night	7% 3 1 4 4 3 4 5% 7% 11% 50%	1729
	21st to end	Night	6% 5% 2 4 4 3 6% 5% 7% 12% 46%	1980
September	1st to 10th	Night	7% 3 2 3 3 3 4 6% 5% 9% 55%	1800
	11th to 20th	Night	8% 5% 2 4 5% 3 4 4 6% 8% 51%	1911
	21st to end	Night	7% 3 2 3 4 3 3 4 4 7% 61%	2008
October	1st to 10th	Night	7% 3 1 3 3 2 3 3 4 6% 64%	2160
	11th to 20th	Night	11% 4 1 3 3 2 3 3 4 6% 59%	2160
	21st to end	Night	15% 6% 2 4 3 2 3 3 4 4 56%	2376
November	1st to 10th	Night	11% 5% 2 4 3 2 3 3 4 5% 58%	2220
	11th to 20th	Night	11% 4 3 5% 4 2 3 4 5% 5% 55%	2280
	21st to end	Night	16% 7% 3 4 5% 2 2 3 3 4 50%	2337
December	1st to 10th	Night	17% 6% 3 4 4 3 4 4 4 6% 47%	2470
	11th to 20th	Night	16% 6% 2 5% 4 3 4 5% 4 4 48%	3036
	21st to end	Night	18% 8% 2 4 4 2 3 3 3 5% 47%	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	46% 2 4 19% 24% 4	2848
	11th to 20th	Day	40% 3 9% 24% 21% 3	2850
	21st to end	Day	45% 2 5% 16% 23% 9%	3135
February	1st to 10th	Day	50% 4 5% 17% 17% 7%	1710
	11th to 20th	Day	47% 4 6% 19% 18% 7%	1775
	21st to end	Day	50% 3 6% 12% 21% 8%	1727
March	1st to 10th	Day	45% 4 6% 16% 19% 10%	2035
	11th to 20th	Day	47% 4 8% 19% 18% 4	1980
	21st to end	Day	43% 5% 8% 21% 20% 3	2178
April	1st to 10th	Day	41% 5% 8% 23% 17% 7%	2087
	11th to 20th	Day	42% 5% 7% 20% 20% 6%	2134
	21st to end	Day	39% 6% 9% 23% 21% 3	2160
May	1st to 10th	Day	42% 5% 9% 23% 16% 5%	2168
	11th to 20th	Day	40% 8% 12% 24% 14% 2	2306
	21st to end	Day	40% 8% 15% 22% 14% 1	2531
June	1st to 10th	Day	36% 9% 15% 25% 14% 1	2340
	11th to 20th	Day	35% 8% 13% 25% 18% 2	2340
	21st to end	Day	30% 7% 14% 27% 20% 2	2340
July	1st to 10th	Day	39% 10% 18% 22% 10% 1	2276
	11th to 20th	Day	31% 8% 18% 25% 16% 2	2271
	21st to end	Day	33% 9% 20% 26% 12% 1	2405
August	1st to 10th	Day	28% 9% 19% 29% 13% 1	2314
	11th to 20th	Day	34% 8% 15% 25% 16% 2	2172
	21st to end	Day	35% 10% 16% 23% 13% 3	2376
September	1st to 10th	Day	33% 7% 13% 19% 21% 8%	2160
	11th to 20th	Day	38% 7% 11% 18% 20% 6%	2044
	21st to end	Day	27% 6% 11% 20% 24% 11%	1932
October	1st to 10th	Day	26% 5% 11% 22% 23% 13%	1800
	11th to 20th	Day	34% 3 5% 17% 27% 15%	1800
	21st to end	Day	36% 3 6% 18% 26% 11%	1980
November	1st to 10th	Day	33% 4 8% 20% 25% 10%	1858
	11th to 20th	Day	35% 4 6% 17% 28% 10%	1900
	21st to end	Day	44% 3 6% 16% 24% 7%	1839
December	1st to 10th	Day	43% 4 7% 19% 18% 8%	1710
	11th to 20th	Day	44% 3 6% 16% 24% 6%	2159
	21st to end	Day	45% 4 7% 16% 21% 6%	3135
January	1st to 10th	Night	40% 3 5% 16% 30% 6%	4108
	11th to 20th	Night	37% 3 6% 21% 26% 7%	4120
	21st to end	Night	46% 3 6% 15% 21% 8%	4532
February	1st to 10th	Night	42% 3 7% 18% 20% 9%	2470
	11th to 20th	Night	45% 4 6% 18% 20% 8%	2315
	21st to end	Night	43% 3 6% 15% 20% 12%	1727
March	1st to 10th	Night	39% 4 7% 17% 21% 12%	2041
	11th to 20th	Night	41% 5% 9% 17% 20% 8%	1980
	21st to end	Night	39% 5% 8% 19% 24% 5%	2178
April	1st to 10th	Night	35% 3 10% 23% 18% 11%	1872
	11th to 20th	Night	35% 5% 9% 19% 21% 11%	1775
	21st to end	Night	32% 5% 10% 24% 25% 4	1800
May	1st to 10th	Night	34% 6% 10% 25% 17% 9%	1787
	11th to 20th	Night	34% 6% 13% 27% 18% 2	1594
	21st to end	Night	32% 8% 14% 27% 17% 1	1746
June	1st to 10th	Night	24% 9% 17% 28% 19% 3	1620
	11th to 20th	Night	23% 6% 12% 32% 25% 4	1620
	21st to end	Night	23% 7% 14% 26% 25% 5%	1620
July	1st to 10th	Night	27% 10% 20% 26% 14% 2	1575
	11th to 20th	Night	18% 8% 22% 31% 18% 4	1566
	21st to end	Night	22% 8% 20% 34% 14% 2	1673
August	1st to 10th	Night	18% 7% 21% 34% 20% 1	1601
	11th to 20th	Night	27% 8% 14% 28% 19% 4	1729
	21st to end	Night	29% 9% 19% 22% 18% 3	1980
September	1st to 10th	Night	26% 8% 14% 20% 22% 10%	1800
	11th to 20th	Night	30% 6% 11% 22% 22% 8%	1911
	21st to end	Night	24% 5% 10% 21% 28% 13%	2008
October	1st to 10th	Night	22% 4 9% 24% 24% 16%	2160
	11th to 20th	Night	28% 4 7% 16% 28% 18%	2160
	21st to end	Night	33% 4 6% 16% 25% 16%	2376
November	1st to 10th	Night	29% 4 8% 18% 27% 13%	2220
	11th to 20th	Night	31% 4 8% 17% 27% 12%	2280
	21st to end	Night	40% 4 6% 17% 26% 9%	2337
December	1st to 10th	Night	40% 5% 8% 18% 21% 8%	2470
	11th to 20th	Night	40% 5% 7% 14% 24% 11%	3037
	21st to end	Night	41% 3 7% 20% 24% 5%	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	26% 14% 41% 17% 2	270
	11th to 20th	Day	26% 19% 38% 13% 3 1	270
	21st to end	Day	27% 23% 32% 15% 3	297
February	1st to 10th	Day	33% 15% 34% 14% 4	270
	11th to 20th	Day	34% 20% 34% 9% 2	270
	21st to end	Day	42% 26% 25% 6% 1	225
March	1st to 10th	Day	29% 17% 35% 15% 4	255
	11th to 20th	Day	24% 26% 34% 14% 2	240
	21st to end	Day	23% 23% 35% 16% 3	264
April	1st to 10th	Day	20% 17% 37% 19% 6%	347
	11th to 20th	Day	26% 16% 28% 21% 9% 1	412
	21st to end	Day	19% 14% 33% 24% 8% 2	420
May	1st to 10th	Day	19% 10% 33% 29% 7% 1	431
	11th to 20th	Day	13% 8% 30% 31% 14% 4	625
	21st to end	Day	13% 5% 25% 35% 18% 5%	679
June	1st to 10th	Day	9% 3 15% 35% 31% 8%	630
	11th to 20th	Day	7% 2 17% 39% 28% 7%	630
	21st to end	Day	6% 3 15% 36% 30% 11%	630
July	1st to 10th	Day	8% 2 12% 33% 35% 11%	621
	11th to 20th	Day	5% 1 9% 30% 41% 14%	618
	21st to end	Day	6% 1 7% 33% 40% 13%	684
August	1st to 10th	Day	6% 1 9% 29% 43% 13%	626
	11th to 20th	Day	10% 2 7% 32% 37% 13%	486
	21st to end	Day	11% 1 6% 22% 38% 21%	495
September	1st to 10th	Day	8% 1 10% 24% 41% 16%	450
	11th to 20th	Day	8% 3 12% 30% 36% 11%	334
	21st to end	Day	10% 3 14% 37% 24% 13%	270
October	1st to 10th	Day	6% 3 29% 39% 18% 5%	270
	11th to 20th	Day	14% 7% 32% 30% 11% 4	270
	21st to end	Day	28% 11% 31% 19% 10% 1	297
November	1st to 10th	Day	16% 9% 31% 28% 14% 1	270
	11th to 20th	Day	13% 14% 40% 25% 6% 1	270
	21st to end	Day	26% 18% 27% 20% 8% 1	270
December	1st to 10th	Day	20% 19% 36% 17% 7% 1	270
	11th to 20th	Day	26% 17% 33% 17% 6% 1	270
	21st to end	Day	23% 23% 36% 13% 3 1	297
January	1st to 10th	Night	24% 13% 32% 26% 5%	950
	11th to 20th	Night	25% 15% 32% 22% 6%	950
	21st to end	Night	23% 14% 33% 27% 2	1045
February	1st to 10th	Night	24% 14% 34% 23% 5%	950
	11th to 20th	Night	26% 14% 38% 19% 3	840
	21st to end	Night	26% 20% 31% 21% 3	471
March	1st to 10th	Night	23% 11% 34% 27% 5%	557
	11th to 20th	Night	18% 15% 35% 26% 5% 1	540
	21st to end	Night	18% 13% 37% 25% 7%	594
April	1st to 10th	Night	14% 12% 39% 27% 8%	540
	11th to 20th	Night	13% 15% 34% 26% 11% 1	533
	21st to end	Night	12% 11% 37% 31% 9% 1	540
May	1st to 10th	Night	11% 8% 35% 33% 11% 1	540
	11th to 20th	Night	13% 6% 31% 31% 18% 2	531
	21st to end	Night	8% 4 23% 38% 24% 4	584
June	1st to 10th	Night	5% 2 11% 42% 36% 3	540
	11th to 20th	Night	5% 1 13% 46% 33% 2	540
	21st to end	Night	4 1 14% 36% 37% 8%	540
July	1st to 10th	Night	4 1 10% 36% 42% 7%	525
	11th to 20th	Night	5% 7% 34% 45% 9%	522
	21st to end	Night	3 1 7% 38% 41% 10%	591
August	1st to 10th	Night	3 1 8% 34% 45% 9%	537
	11th to 20th	Night	8% 8% 40% 37% 7%	534
	21st to end	Night	9% 1 5% 32% 44% 9%	594
September	1st to 10th	Night	8% 1 8% 32% 44% 6%	540
	11th to 20th	Night	11% 1 11% 33% 40% 4	540
	21st to end	Night	8% 2 11% 39% 36% 4	568
October	1st to 10th	Night	9% 1 16% 41% 28% 5%	720
	11th to 20th	Night	14% 6% 24% 36% 20% 1	720
	21st to end	Night	16% 8% 27% 30% 17% 2	792
November	1st to 10th	Night	13% 6% 27% 36% 17% 1	740
	11th to 20th	Night	13% 11% 30% 36% 11%	760
	21st to end	Night	21% 11% 30% 25% 12%	817
December	1st to 10th	Night	19% 11% 32% 30% 7%	950
	11th to 20th	Night	23% 12% 28% 29% 7%	950
	21st to end	Night	23% 15% 29% 27% 6%	1045

Page generated at 2024-03-03 05:28:54. Version ac07

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