Cedar Hill
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cedar Hill clear sky chart from 2005-11-06 to 2024-01-31.

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	10% 5% 2 4 4 3 4 4 5% 7% 51%	75088
	Night	10% 4 2 4 4 2 3 4 5% 7% 56%	75065
Transparency	Day	32% 6% 10% 22% 22% 8%	74813
	Night	28% 5% 10% 22% 24% 12%	74860
Seeing	Day	11% 6% 21% 29% 24% 9%	14030
	Night	12% 6% 28% 36% 17% 1	24072

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	13% 6% 2 3 3 2 2 3 3 6% 56%	1707
	11th to 20th	Day	15% 5% 2 4 3 2 2 3 4 6% 53%	1710
	21st to end	Day	16% 5% 2 3 2 3 2 3 4 6% 53%	1872
February	1st to 10th	Day	15% 7% 3 6% 5% 3 3 3 3 6% 47%	1746
	11th to 20th	Day	17% 8% 3 5% 4 2 3 4 3 4 47%	1749
	21st to end	Day	21% 5% 2 4 3 2 2 2 3 4 52%	1500
March	1st to 10th	Day	17% 6% 2 4 4 3 3 3 5% 7% 45%	1980
	11th to 20th	Day	15% 7% 2 4 5% 2 4 4 4 6% 47%	1980
	21st to end	Day	11% 6% 3 4 4 3 4 3 4 7% 50%	2178
April	1st to 10th	Day	11% 5% 3 5% 5% 2 5% 4 5% 7% 48%	1980
	11th to 20th	Day	12% 6% 2 4 5% 3 4 5% 5% 7% 46%	2034
	21st to end	Day	11% 5% 2 4 5% 3 5% 4 5% 6% 49%	2290
May	1st to 10th	Day	12% 4 3 5% 5% 3 5% 4 6% 7% 46%	2340
	11th to 20th	Day	11% 5% 2 5% 5% 4 6% 5% 5% 7% 43%	2302
	21st to end	Day	10% 6% 3 6% 6% 3 6% 6% 7% 9% 39%	2531
June	1st to 10th	Day	4 3 2 4 5% 3 5% 5% 6% 9% 53%	2340
	11th to 20th	Day	5% 2 2 5% 5% 3 5% 5% 6% 10% 53%	2340
	21st to end	Day	5% 4 2 4 5% 3 5% 5% 6% 8% 53%	2340
July	1st to 10th	Day	7% 5% 2 5% 5% 4 6% 5% 7% 10% 43%	2340
	11th to 20th	Day	3 2 1 3 4 3 4 6% 5% 8% 61%	2340
	21st to end	Day	3 2 2 4 5% 3 6% 6% 8% 11% 50%	2546
August	1st to 10th	Day	2 1 1 3 3 2 4 5% 7% 11% 62%	2328
	11th to 20th	Day	7% 4 2 4 4 3 5% 5% 8% 9% 49%	2301
	21st to end	Day	4 3 1 5% 4 4 5% 6% 7% 10% 51%	2298
September	1st to 10th	Day	8% 4 2 5% 4 2 4 4 4 7% 55%	1980
	11th to 20th	Day	11% 4 2 5% 5% 3 5% 4 6% 8% 46%	1980
	21st to end	Day	7% 3 2 4 4 2 3 5% 6% 8% 57%	1980
October	1st to 10th	Day	4 3 1 3 4 3 4 5% 5% 7% 61%	1941
	11th to 20th	Day	12% 3 1 3 2 2 4 4 4 5% 60%	1800
	21st to end	Day	14% 4 2 4 3 1 2 2 3 4 61%	1980
November	1st to 10th	Day	12% 5% 1 4 4 2 2 3 4 5% 57%	1858
	11th to 20th	Day	7% 4 2 4 5% 2 4 3 5% 6% 59%	1781
	21st to end	Day	15% 6% 2 4 4 3 3 3 3 5% 53%	1710
December	1st to 10th	Day	15% 5% 2 4 3 3 4 4 4 6% 50%	1710
	11th to 20th	Day	14% 6% 3 6% 5% 2 4 4 4 5% 46%	2161
	21st to end	Day	17% 7% 2 4 4 2 3 3 3 5% 50%	3135
January	1st to 10th	Night	11% 5% 2 3 3 2 4 3 4 5% 58%	2458
	11th to 20th	Night	14% 5% 2 4 3 1 3 3 4 6% 56%	2470
	21st to end	Night	14% 6% 2 4 3 2 3 3 4 5% 55%	2711
February	1st to 10th	Night	15% 6% 2 4 4 2 3 3 3 5% 53%	2228
	11th to 20th	Night	15% 6% 2 5% 4 2 3 3 4 6% 50%	2098
	21st to end	Night	18% 5% 2 4 3 2 3 3 4 5% 51%	1754
March	1st to 10th	Night	14% 6% 3 6% 4 3 3 3 6% 8% 45%	1980
	11th to 20th	Night	13% 5% 2 4 4 3 4 5% 4 6% 50%	1980
	21st to end	Night	10% 5% 2 4 4 3 4 3 4 6% 55%	2178
April	1st to 10th	Night	8% 5% 2 3 3 3 3 4 5% 8% 55%	1980
	11th to 20th	Night	12% 5% 3 5% 4 2 3 3 4 7% 52%	1872
	21st to end	Night	10% 5% 2 4 4 2 3 2 5% 8% 55%	1666
May	1st to 10th	Night	9% 5% 3 3 5% 3 4 4 6% 8% 51%	1620
	11th to 20th	Night	10% 4 3 5% 4 3 3 4 7% 10% 48%	1593
	21st to end	Night	8% 4 2 4 5% 3 4 5% 6% 10% 49%	1745
June	1st to 10th	Night	4 2 2 3 4 2 4 4 6% 9% 59%	1620
	11th to 20th	Night	3 2 1 3 3 2 3 5% 5% 9% 64%	1620
	21st to end	Night	3 2 2 3 4 2 4 5% 7% 11% 58%	1620
July	1st to 10th	Night	4 3 2 3 4 2 5% 5% 7% 13% 53%	1620
	11th to 20th	Night	2 2 1 1 2 2 2 3 4 9% 71%	1620
	21st to end	Night	1 1 1 2 4 2 5% 5% 7% 11% 61%	1772
August	1st to 10th	Night	2 1 1 1 1 1 2 3 5% 10% 73%	1611
	11th to 20th	Night	4 2 2 4 3 2 3 4 5% 10% 59%	1600
	21st to end	Night	4 3 1 3 4 3 4 5% 7% 9% 57%	2050
September	1st to 10th	Night	7% 4 2 4 4 2 3 4 5% 8% 56%	1980
	11th to 20th	Night	11% 4 2 4 4 3 3 4 5% 7% 53%	1980
	21st to end	Night	6% 3 1 2 3 2 3 4 5% 7% 63%	1980
October	1st to 10th	Night	5% 3 2 3 3 2 3 4 5% 7% 64%	1998
	11th to 20th	Night	11% 4 1 3 3 1 2 2 4 6% 63%	2160
	21st to end	Night	15% 5% 2 3 3 2 2 2 3 4 61%	2376
November	1st to 10th	Night	10% 5% 2 3 3 2 3 3 3 4 61%	2220
	11th to 20th	Night	6% 4 2 4 3 2 4 4 4 6% 60%	2397
	21st to end	Night	14% 4 2 4 3 2 3 3 4 5% 53%	2470
December	1st to 10th	Night	12% 5% 2 4 3 2 3 3 4 6% 55%	2470
	11th to 20th	Night	12% 6% 3 5% 4 2 4 4 4 6% 51%	3036
	21st to end	Night	15% 6% 2 5% 3 2 2 3 3 5% 55%	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	31% 4 7% 20% 30% 9%	1708
	11th to 20th	Day	33% 3 7% 24% 26% 7%	1710
	21st to end	Day	33% 4 6% 18% 28% 11%	1872
February	1st to 10th	Day	40% 3 7% 17% 21% 11%	1746
	11th to 20th	Day	42% 4 7% 18% 20% 10%	1759
	21st to end	Day	39% 3 5% 16% 22% 16%	1500
March	1st to 10th	Day	40% 5% 8% 16% 21% 12%	1980
	11th to 20th	Day	39% 6% 8% 17% 23% 8%	1980
	21st to end	Day	36% 5% 10% 20% 20% 9%	2178
April	1st to 10th	Day	35% 6% 11% 19% 18% 10%	1980
	11th to 20th	Day	37% 7% 9% 19% 21% 8%	2034
	21st to end	Day	35% 6% 9% 20% 24% 6%	2290
May	1st to 10th	Day	35% 7% 10% 22% 18% 8%	2340
	11th to 20th	Day	39% 7% 12% 20% 19% 3	2306
	21st to end	Day	39% 9% 13% 22% 15% 2	2531
June	1st to 10th	Day	26% 9% 15% 30% 17% 4	2340
	11th to 20th	Day	27% 7% 13% 29% 19% 5%	2340
	21st to end	Day	27% 7% 12% 26% 23% 4	2340
July	1st to 10th	Day	33% 8% 18% 26% 14% 1	2276
	11th to 20th	Day	18% 8% 14% 34% 22% 4	2271
	21st to end	Day	22% 9% 19% 34% 16% 1	2405
August	1st to 10th	Day	15% 6% 16% 34% 26% 3	2314
	11th to 20th	Day	28% 8% 17% 26% 18% 3	2301
	21st to end	Day	25% 8% 15% 29% 19% 4	2298
September	1st to 10th	Day	29% 6% 9% 23% 24% 9%	1980
	11th to 20th	Day	35% 8% 11% 19% 20% 7%	1980
	21st to end	Day	25% 5% 9% 24% 24% 13%	1980
October	1st to 10th	Day	21% 7% 11% 23% 21% 17%	1941
	11th to 20th	Day	27% 5% 7% 16% 26% 19%	1800
	21st to end	Day	30% 3 6% 18% 26% 17%	1980
November	1st to 10th	Day	31% 4 9% 22% 24% 10%	1858
	11th to 20th	Day	26% 4 10% 21% 29% 11%	1781
	21st to end	Day	35% 4 6% 21% 24% 11%	1710
December	1st to 10th	Day	34% 5% 9% 21% 24% 8%	1710
	11th to 20th	Day	39% 5% 7% 14% 25% 10%	2159
	21st to end	Day	37% 4 5% 22% 23% 10%	3135
January	1st to 10th	Night	29% 3 7% 20% 28% 13%	2458
	11th to 20th	Night	32% 3 8% 19% 27% 11%	2470
	21st to end	Night	34% 3 5% 16% 26% 16%	2711
February	1st to 10th	Night	36% 5% 7% 15% 22% 15%	2228
	11th to 20th	Night	37% 4 7% 16% 26% 11%	2098
	21st to end	Night	37% 4 8% 14% 20% 17%	1754
March	1st to 10th	Night	37% 5% 8% 16% 20% 14%	1980
	11th to 20th	Night	35% 6% 9% 15% 25% 10%	1980
	21st to end	Night	30% 6% 11% 20% 25% 8%	2178
April	1st to 10th	Night	28% 5% 10% 22% 20% 14%	1980
	11th to 20th	Night	33% 5% 10% 18% 18% 15%	1872
	21st to end	Night	28% 5% 11% 22% 28% 6%	1666
May	1st to 10th	Night	32% 6% 11% 23% 19% 9%	1620
	11th to 20th	Night	31% 7% 16% 25% 18% 3	1594
	21st to end	Night	29% 9% 16% 26% 17% 3	1746
June	1st to 10th	Night	21% 8% 14% 32% 20% 5%	1620
	11th to 20th	Night	17% 6% 15% 34% 21% 7%	1620
	21st to end	Night	20% 7% 14% 26% 26% 6%	1620
July	1st to 10th	Night	21% 11% 15% 36% 14% 3	1575
	11th to 20th	Night	11% 4 15% 37% 26% 7%	1566
	21st to end	Night	14% 7% 21% 36% 20% 2	1673
August	1st to 10th	Night	9% 4 15% 37% 30% 5%	1601
	11th to 20th	Night	21% 7% 15% 29% 22% 6%	1600
	21st to end	Night	21% 7% 14% 33% 21% 4	2050
September	1st to 10th	Night	24% 7% 12% 22% 24% 10%	1980
	11th to 20th	Night	31% 5% 13% 19% 20% 11%	1980
	21st to end	Night	20% 5% 10% 22% 27% 16%	1980
October	1st to 10th	Night	20% 4 10% 27% 19% 19%	1998
	11th to 20th	Night	25% 3 8% 17% 24% 22%	2160
	21st to end	Night	29% 3 4 17% 26% 21%	2376
November	1st to 10th	Night	28% 4 7% 20% 27% 15%	2220
	11th to 20th	Night	24% 4 9% 20% 28% 15%	2397
	21st to end	Night	34% 4 7% 16% 27% 12%	2470
December	1st to 10th	Night	32% 4 8% 21% 23% 13%	2470
	11th to 20th	Night	35% 3 6% 15% 27% 13%	3037
	21st to end	Night	33% 3 6% 17% 26% 14%	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	19% 13% 34% 27% 7%	270
	11th to 20th	Day	19% 12% 36% 26% 5% 2	270
	21st to end	Day	19% 12% 38% 21% 9% 1	294
February	1st to 10th	Day	22% 12% 35% 25% 6%	240
	11th to 20th	Day	25% 13% 40% 18% 4	240
	21st to end	Day	30% 15% 33% 19% 3	198
March	1st to 10th	Day	18% 18% 37% 21% 5%	240
	11th to 20th	Day	16% 16% 38% 22% 7% 2	240
	21st to end	Day	12% 17% 41% 21% 8% 1	264
April	1st to 10th	Day	14% 17% 35% 24% 10% 1	240
	11th to 20th	Day	18% 12% 36% 26% 8% 1	312
	21st to end	Day	14% 13% 37% 24% 9% 2	550
May	1st to 10th	Day	11% 10% 33% 36% 8% 1	603
	11th to 20th	Day	15% 6% 28% 32% 15% 4	625
	21st to end	Day	12% 6% 25% 32% 20% 5%	679
June	1st to 10th	Day	4 2 13% 40% 29% 12%	630
	11th to 20th	Day	5% 2 16% 43% 27% 8%	630
	21st to end	Day	3 1 12% 36% 34% 13%	630
July	1st to 10th	Day	6% 2 8% 30% 39% 15%	621
	11th to 20th	Day	2 6% 31% 43% 17%	618
	21st to end	Day	3 3 28% 49% 17%	684
August	1st to 10th	Day	3 5% 32% 44% 16%	626
	11th to 20th	Day	9% 1 4 30% 44% 13%	615
	21st to end	Day	5% 1 4 23% 38% 29%	417
September	1st to 10th	Day	8% 4 17% 41% 29%	270
	11th to 20th	Day	4 1 6% 20% 44% 24%	270
	21st to end	Day	10% 2 6% 23% 37% 21%	270
October	1st to 10th	Day	1 1 15% 33% 36% 13%	270
	11th to 20th	Day	10% 6% 27% 29% 21% 7%	270
	21st to end	Day	23% 9% 22% 25% 17% 4	297
November	1st to 10th	Day	19% 4 30% 28% 14% 4	270
	11th to 20th	Day	9% 8% 31% 33% 16% 3	270
	21st to end	Day	17% 12% 34% 23% 11% 1	270
December	1st to 10th	Day	17% 6% 36% 26% 13% 2	270
	11th to 20th	Day	18% 12% 34% 27% 9%	270
	21st to end	Day	19% 11% 40% 21% 9%	297
January	1st to 10th	Night	13% 8% 37% 33% 9%	950
	11th to 20th	Night	17% 13% 33% 31% 6% 1	950
	21st to end	Night	17% 10% 35% 32% 7%	1043
February	1st to 10th	Night	18% 9% 39% 29% 4 1	788
	11th to 20th	Night	17% 12% 41% 27% 3	704
	21st to end	Night	20% 13% 43% 22% 2	570
March	1st to 10th	Night	16% 13% 36% 29% 6%	540
	11th to 20th	Night	15% 8% 41% 30% 6%	540
	21st to end	Night	12% 11% 41% 31% 5%	594
April	1st to 10th	Night	10% 9% 44% 31% 6%	540
	11th to 20th	Night	14% 9% 42% 29% 6%	533
	21st to end	Night	12% 8% 43% 28% 8% 1	540
May	1st to 10th	Night	9% 8% 39% 37% 6% 1	540
	11th to 20th	Night	10% 4 33% 37% 15% 1	531
	21st to end	Night	8% 4 30% 40% 17% 1	584
June	1st to 10th	Night	5% 1 15% 50% 26% 2	540
	11th to 20th	Night	3 2 21% 55% 18% 1	540
	21st to end	Night	3 1 16% 44% 33% 4	540
July	1st to 10th	Night	4 1 10% 45% 36% 5%	525
	11th to 20th	Night	3 8% 44% 43% 1	522
	21st to end	Night	1 1 5% 49% 41% 4	591
August	1st to 10th	Night	2 4 47% 42% 3	537
	11th to 20th	Night	5% 6% 44% 39% 6%	534
	21st to end	Night	4 1 4 39% 46% 7%	594
September	1st to 10th	Night	8% 9% 41% 38% 5%	540
	11th to 20th	Night	12% 2 8% 37% 39% 3	540
	21st to end	Night	6% 1 12% 41% 34% 5%	540
October	1st to 10th	Night	6% 1 18% 44% 28% 3	558
	11th to 20th	Night	12% 4 24% 39% 18% 2	720
	21st to end	Night	17% 7% 28% 33% 15% 1	792
November	1st to 10th	Night	11% 4 28% 41% 15% 1	740
	11th to 20th	Night	8% 8% 31% 39% 14%	877
	21st to end	Night	17% 9% 35% 29% 10% 1	950
December	1st to 10th	Night	15% 8% 35% 35% 6%	950
	11th to 20th	Night	17% 9% 33% 35% 6%	950
	21st to end	Night	17% 9% 35% 33% 6%	1045

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