Cedar Hill Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cedar Hill Park clear sky chart from 2005-11-06 to 2026-07-31.

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	12% 8% 3 7% 4 4 4 4 5% 7% 42%	138216
	Night	13% 8% 3 7% 4 4 4 3 5% 6% 43%	135080
Transparency	Day	40% 5% 11% 25% 17% 3	141810
	Night	41% 4 11% 24% 18% 3	139566
Seeing	Day	17% 12% 28% 25% 14% 4	17997
	Night	17% 11% 29% 28% 13% 1	27753

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	11% 11% 5% 12% 5% 5% 3 3 5% 6% 33%	4691
	11th to 20th	Day	7% 9% 4 7% 4 5% 4 3 5% 7% 45%	5190
	21st to end	Day	16% 12% 4 8% 4 3 4 3 5% 5% 37%	5812
February	1st to 10th	Day	15% 11% 4 8% 4 4 4 3 5% 7% 35%	1890
	11th to 20th	Day	15% 9% 3 7% 6% 4 4 3 5% 6% 38%	2022
	21st to end	Day	14% 10% 2 6% 4 4 4 4 5% 7% 40%	1730
March	1st to 10th	Day	16% 12% 2 5% 3 2 2 3 3 4 48%	4706
	11th to 20th	Day	10% 7% 2 4 3 4 4 3 5% 6% 52%	5090
	21st to end	Day	13% 8% 3 7% 5% 5% 5% 4 5% 8% 37%	5859
April	1st to 10th	Day	12% 7% 2 7% 5% 4 4 4 6% 8% 42%	2520
	11th to 20th	Day	16% 9% 2 5% 4 4 4 3 5% 6% 41%	2494
	21st to end	Day	18% 6% 2 7% 5% 5% 4 3 5% 7% 37%	2520
May	1st to 10th	Day	15% 8% 3 7% 5% 5% 5% 4 6% 8% 33%	7114
	11th to 20th	Day	15% 8% 2 7% 4 4 4 4 6% 7% 38%	8154
	21st to end	Day	15% 8% 3 8% 5% 5% 5% 4 6% 7% 33%	9047
June	1st to 10th	Day	9% 6% 2 5% 4 5% 5% 4 6% 8% 45%	2940
	11th to 20th	Day	8% 4 2 5% 4 4 5% 4 6% 10% 48%	2940
	21st to end	Day	5% 4 2 5% 5% 5% 6% 4 7% 9% 47%	2940
July	1st to 10th	Day	10% 5% 2 6% 4 5% 4 3 5% 9% 46%	6500
	11th to 20th	Day	6% 5% 2 6% 5% 5% 5% 5% 8% 11% 41%	6500
	21st to end	Day	6% 5% 2 7% 5% 5% 6% 5% 8% 11% 40%	6613
August	1st to 10th	Day	5% 4 2 5% 4 4 5% 5% 7% 9% 52%	4216
	11th to 20th	Day	12% 5% 2 5% 5% 5% 4 4 6% 8% 44%	3849
	21st to end	Day	6% 4 2 5% 3 4 4 4 6% 10% 52%	4312
September	1st to 10th	Day	13% 5% 2 4 4 3 4 3 6% 7% 49%	2400
	11th to 20th	Day	10% 5% 2 5% 4 4 4 4 5% 8% 50%	2384
	21st to end	Day	9% 4 2 5% 5% 3 4 3 5% 7% 53%	2180
October	1st to 10th	Day	9% 4 2 6% 4 3 3 3 4 7% 56%	2000
	11th to 20th	Day	14% 5% 2 4 4 3 3 2 4 5% 53%	2000
	21st to end	Day	18% 8% 2 4 4 3 3 3 4 5% 47%	2200
November	1st to 10th	Day	12% 5% 2 5% 4 3 3 3 4 6% 54%	1854
	11th to 20th	Day	13% 7% 3 6% 4 4 2 3 5% 7% 47%	1890
	21st to end	Day	17% 11% 4 6% 3 3 3 3 3 5% 42%	1811
December	1st to 10th	Day	9% 10% 2 6% 4 3 3 3 4 6% 49%	2690
	11th to 20th	Day	12% 10% 5% 7% 5% 4 3 3 4 6% 40%	3088
	21st to end	Day	21% 17% 6% 9% 5% 4 4 3 4 4 25%	4070
January	1st to 10th	Night	13% 10% 6% 11% 5% 4 3 3 4 4 37%	8232
	11th to 20th	Night	9% 9% 4 11% 5% 5% 5% 3 4 5% 41%	7784
	21st to end	Night	16% 12% 4 8% 5% 4 3 2 4 4 37%	8402
February	1st to 10th	Night	16% 11% 4 8% 5% 3 3 3 5% 5% 36%	2730
	11th to 20th	Night	15% 9% 4 8% 4 4 4 2 4 6% 41%	2483
	21st to end	Night	15% 9% 3 8% 4 4 3 3 4 5% 42%	2076
March	1st to 10th	Night	18% 12% 2 5% 3 3 3 2 3 5% 42%	5410
	11th to 20th	Night	11% 9% 2 5% 3 3 4 3 4 6% 49%	5090
	21st to end	Night	17% 9% 3 8% 6% 5% 4 4 5% 6% 34%	5312
April	1st to 10th	Night	12% 6% 2 6% 4 4 4 3 5% 7% 46%	2100
	11th to 20th	Night	14% 8% 3 6% 4 4 3 3 5% 7% 44%	2075
	21st to end	Night	19% 7% 2 6% 3 3 3 3 4 7% 41%	2100
May	1st to 10th	Night	17% 7% 3 7% 5% 4 4 3 6% 8% 35%	5737
	11th to 20th	Night	13% 6% 2 5% 4 4 4 4 6% 8% 43%	4731
	21st to end	Night	15% 10% 3 8% 6% 5% 5% 4 6% 8% 32%	5139
June	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 6% 9% 48%	1680
	11th to 20th	Night	6% 4 2 4 4 4 4 4 6% 9% 53%	1680
	21st to end	Night	4 4 2 4 4 5% 4 4 7% 9% 55%	1680
July	1st to 10th	Night	10% 4 2 6% 4 4 4 3 6% 9% 47%	3698
	11th to 20th	Night	5% 5% 2 6% 4 5% 4 4 6% 9% 49%	3697
	21st to end	Night	6% 5% 2 6% 5% 5% 5% 5% 9% 11% 43%	4461
August	1st to 10th	Night	5% 3 1 4 3 4 3 3 6% 9% 59%	2941
	11th to 20th	Night	10% 5% 2 6% 5% 4 4 3 6% 8% 48%	3200
	21st to end	Night	5% 3 1 5% 3 4 4 4 5% 10% 57%	3586
September	1st to 10th	Night	11% 6% 2 5% 4 3 3 2 6% 6% 52%	2000
	11th to 20th	Night	9% 5% 1 5% 3 3 4 4 5% 7% 53%	2000
	21st to end	Night	10% 5% 1 4 3 4 5% 3 5% 5% 54%	2212
October	1st to 10th	Night	8% 4 2 5% 3 3 3 2 5% 7% 61%	2400
	11th to 20th	Night	14% 5% 2 5% 3 2 3 2 5% 6% 54%	2400
	21st to end	Night	19% 8% 2 4 2 2 3 3 3 6% 48%	2640
November	1st to 10th	Night	10% 6% 2 5% 3 3 2 3 5% 6% 55%	2661
	11th to 20th	Night	14% 6% 3 5% 4 3 3 3 4 6% 49%	2730
	21st to end	Night	18% 10% 3 5% 3 3 3 2 5% 5% 43%	2804
December	1st to 10th	Night	12% 10% 3 7% 4 3 3 3 4 5% 46%	4720
	11th to 20th	Night	14% 8% 4 7% 4 4 3 3 4 6% 42%	5339
	21st to end	Night	23% 17% 4 8% 5% 4 4 3 4 5% 23%	7150

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	51% 3 11% 23% 9% 2	4692
	11th to 20th	Day	40% 3 8% 26% 19% 4	5190
	21st to end	Day	50% 2 10% 18% 15% 5%	5812
February	1st to 10th	Day	49% 5% 10% 23% 11% 1	1890
	11th to 20th	Day	48% 4 9% 20% 15% 4	2032
	21st to end	Day	44% 4 9% 23% 15% 4	1730
March	1st to 10th	Day	42% 3 5% 22% 22% 7%	4706
	11th to 20th	Day	33% 3 8% 25% 24% 7%	5090
	21st to end	Day	44% 5% 14% 27% 10% 1	5861
April	1st to 10th	Day	39% 5% 12% 25% 18% 1	2520
	11th to 20th	Day	42% 5% 11% 22% 16% 4	2494
	21st to end	Day	46% 6% 10% 24% 13% 1	2520
May	1st to 10th	Day	47% 6% 10% 24% 13%	7149
	11th to 20th	Day	45% 4 10% 22% 18% 1	8158
	21st to end	Day	50% 5% 9% 18% 16% 1	9061
June	1st to 10th	Day	35% 8% 11% 27% 17% 2	2940
	11th to 20th	Day	30% 7% 11% 27% 21% 4	2940
	21st to end	Day	29% 9% 17% 25% 16% 5%	2940
July	1st to 10th	Day	36% 4 10% 30% 18% 2	6431
	11th to 20th	Day	35% 5% 16% 28% 13% 1	6425
	21st to end	Day	37% 4 17% 29% 11% 1	6429
August	1st to 10th	Day	27% 6% 16% 35% 16%	4202
	11th to 20th	Day	38% 5% 13% 25% 17% 2	3885
	21st to end	Day	29% 5% 14% 35% 15% 3	4311
September	1st to 10th	Day	33% 5% 11% 26% 20% 5%	2400
	11th to 20th	Day	33% 5% 9% 26% 24% 2	2384
	21st to end	Day	30% 6% 8% 27% 26% 3	2180
October	1st to 10th	Day	18% 3 6% 20% 45% 9%	3260
	11th to 20th	Day	23% 3 6% 22% 36% 10%	3240
	21st to end	Day	33% 3 7% 28% 26% 3	3538
November	1st to 10th	Day	33% 3 12% 26% 20% 5%	1854
	11th to 20th	Day	38% 4 8% 24% 21% 5%	1890
	21st to end	Day	45% 3 9% 26% 16%	1811
December	1st to 10th	Day	37% 3 11% 33% 16% 1	2690
	11th to 20th	Day	46% 3 11% 23% 16% 1	3085
	21st to end	Day	63% 4 11% 13% 7% 1	4070
January	1st to 10th	Night	52% 3 12% 24% 9%	8233
	11th to 20th	Night	46% 3 5% 25% 17% 3	7784
	21st to end	Night	52% 3 10% 19% 15% 1	8402
February	1st to 10th	Night	50% 5% 10% 21% 13% 1	2730
	11th to 20th	Night	46% 4 9% 22% 16% 3	2484
	21st to end	Night	45% 3 9% 23% 16% 4	2076
March	1st to 10th	Night	47% 3 5% 21% 20% 3	5410
	11th to 20th	Night	38% 3 9% 23% 21% 7%	5090
	21st to end	Night	50% 5% 9% 24% 11% 1	5312
April	1st to 10th	Night	37% 4 12% 26% 18% 3	2100
	11th to 20th	Night	40% 4 10% 24% 17% 4	2075
	21st to end	Night	45% 4 10% 24% 16% 2	2100
May	1st to 10th	Night	48% 6% 13% 21% 11% 1	5767
	11th to 20th	Night	39% 4 13% 25% 17% 2	4732
	21st to end	Night	50% 6% 11% 18% 13% 2	5149
June	1st to 10th	Night	33% 6% 14% 26% 18% 4	1680
	11th to 20th	Night	25% 8% 11% 28% 24% 4	1680
	21st to end	Night	24% 7% 16% 29% 19% 7%	1680
July	1st to 10th	Night	34% 5% 11% 28% 20% 2	3660
	11th to 20th	Night	31% 5% 15% 32% 14% 2	3652
	21st to end	Night	34% 4 21% 28% 12% 1	4334
August	1st to 10th	Night	23% 6% 18% 33% 20% 1	2931
	11th to 20th	Night	35% 5% 15% 25% 17% 3	3230
	21st to end	Night	24% 4 14% 35% 19% 3	3586
September	1st to 10th	Night	33% 5% 9% 26% 22% 6%	2000
	11th to 20th	Night	30% 5% 10% 25% 26% 3	2000
	21st to end	Night	30% 6% 9% 23% 28% 4	2212
October	1st to 10th	Night	15% 3 6% 16% 50% 10%	3920
	11th to 20th	Night	22% 3 7% 22% 35% 11%	3899
	21st to end	Night	32% 3 8% 26% 27% 5%	4252
November	1st to 10th	Night	31% 4 12% 26% 22% 5%	2661
	11th to 20th	Night	37% 4 8% 24% 23% 4	2730
	21st to end	Night	44% 4 9% 25% 18% 1	2804
December	1st to 10th	Night	41% 3 9% 31% 15% 1	4720
	11th to 20th	Night	45% 3 12% 22% 18% 1	5341
	21st to end	Night	62% 5% 12% 14% 6% 1	7150

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	27% 22% 33% 15% 3 1	330
	11th to 20th	Day	27% 28% 33% 11%	330
	21st to end	Day	20% 29% 37% 12% 2	363
February	1st to 10th	Day	25% 24% 35% 14% 2	330
	11th to 20th	Day	30% 29% 26% 12% 3 1	330
	21st to end	Day	29% 23% 35% 12% 1	273
March	1st to 10th	Day	24% 24% 40% 11% 2	330
	11th to 20th	Day	34% 18% 33% 11% 2 1	330
	21st to end	Day	30% 20% 35% 12% 3	484
April	1st to 10th	Day	23% 20% 35% 17% 5%	540
	11th to 20th	Day	27% 19% 31% 17% 6%	532
	21st to end	Day	24% 14% 37% 19% 6% 1	540
May	1st to 10th	Day	23% 15% 34% 21% 7%	543
	11th to 20th	Day	21% 13% 30% 23% 10% 3	745
	21st to end	Day	15% 8% 34% 26% 13% 5%	844
June	1st to 10th	Day	11% 8% 25% 29% 21% 5%	780
	11th to 20th	Day	10% 4 26% 38% 16% 5%	780
	21st to end	Day	6% 7% 29% 37% 16% 5%	780
July	1st to 10th	Day	11% 3 16% 31% 28% 12%	771
	11th to 20th	Day	6% 4 21% 40% 23% 6%	768
	21st to end	Day	8% 4 18% 34% 29% 7%	845
August	1st to 10th	Day	8% 3 17% 39% 26% 7%	721
	11th to 20th	Day	13% 4 18% 29% 28% 8%	519
	21st to end	Day	10% 2 15% 31% 31% 10%	583
September	1st to 10th	Day	13% 4 17% 31% 29% 7%	530
	11th to 20th	Day	9% 2 15% 33% 28% 13%	530
	21st to end	Day	12% 8% 22% 30% 19% 8%	510
October	1st to 10th	Day	11% 9% 26% 38% 13% 3	330
	11th to 20th	Day	17% 15% 34% 23% 9% 2	330
	21st to end	Day	32% 19% 28% 18% 4	363
November	1st to 10th	Day	17% 13% 42% 17% 8% 3	330
	11th to 20th	Day	21% 20% 34% 16% 7% 2	330
	21st to end	Day	30% 16% 31% 17% 6% 1	330
December	1st to 10th	Day	20% 21% 35% 16% 6% 2	330
	11th to 20th	Day	24% 20% 35% 17% 4	330
	21st to end	Day	26% 23% 36% 11% 3	363
January	1st to 10th	Night	20% 21% 33% 22% 4	1050
	11th to 20th	Night	22% 23% 34% 18% 3	1050
	21st to end	Night	19% 20% 38% 21% 2	1155
February	1st to 10th	Night	23% 19% 34% 22% 2	1050
	11th to 20th	Night	24% 19% 36% 19% 2	848
	21st to end	Night	23% 19% 37% 20% 2	692
March	1st to 10th	Night	26% 17% 34% 21% 2	809
	11th to 20th	Night	25% 13% 35% 23% 4	630
	21st to end	Night	26% 13% 34% 23% 4	693
April	1st to 10th	Night	17% 16% 38% 24% 5%	630
	11th to 20th	Night	20% 13% 35% 25% 7%	623
	21st to end	Night	24% 11% 37% 23% 6%	630
May	1st to 10th	Night	18% 9% 33% 31% 9%	630
	11th to 20th	Night	19% 7% 27% 32% 15% 1	621
	21st to end	Night	12% 6% 25% 35% 18% 3	683
June	1st to 10th	Night	11% 4 21% 38% 25% 1	630
	11th to 20th	Night	8% 2 24% 45% 20% 1	630
	21st to end	Night	5% 3 24% 44% 23% 2	630
July	1st to 10th	Night	10% 1 11% 38% 33% 6%	615
	11th to 20th	Night	5% 3 13% 44% 32% 4	612
	21st to end	Night	7% 1 16% 40% 32% 3	687
August	1st to 10th	Night	8% 1 14% 40% 35% 2	597
	11th to 20th	Night	8% 2 13% 40% 34% 4	594
	21st to end	Night	7% 1 15% 35% 39% 4	660
September	1st to 10th	Night	13% 2 16% 35% 30% 5%	600
	11th to 20th	Night	10% 3 13% 35% 33% 6%	600
	21st to end	Night	11% 6% 23% 30% 26% 4	795
October	1st to 10th	Night	8% 5% 27% 34% 22% 4	800
	11th to 20th	Night	17% 12% 29% 27% 15% 1	800
	21st to end	Night	25% 13% 31% 25% 6%	880
November	1st to 10th	Night	14% 10% 38% 29% 9%	820
	11th to 20th	Night	19% 15% 33% 26% 7%	840
	21st to end	Night	24% 15% 32% 23% 6%	914
December	1st to 10th	Night	24% 13% 33% 25% 4 1	1050
	11th to 20th	Night	24% 15% 31% 26% 4	1050
	21st to end	Night	25% 18% 34% 21% 3	1155

Page generated at 2026-07-28 02:25:20. Version ac07

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