Dallas
Clear Sky Chart
History

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

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	11% 5% 2 5% 3 3 4 3 5% 7% 51%	101169
	Night	11% 5% 2 4 3 3 3 3 4 7% 56%	97997
Transparency	Day	31% 6% 10% 24% 22% 7%	104912
	Night	28% 5% 10% 23% 24% 11%	102381
Seeing	Day	12% 8% 23% 29% 22% 6%	15148
	Night	13% 7% 29% 35% 15% 1	24993

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% 5% 1 5% 3 3 3 3 4 6% 54%	2847
	11th to 20th	Day	12% 5% 2 3 2 2 2 2 4 5% 61%	2850
	21st to end	Day	23% 10% 3 4 2 2 2 1 2 4 46%	3135
February	1st to 10th	Day	18% 7% 2 7% 3 3 3 2 3 5% 45%	1824
	11th to 20th	Day	17% 7% 3 5% 3 3 3 2 3 5% 48%	1849
	21st to end	Day	22% 6% 2 4 3 2 2 1 3 4 52%	1598
March	1st to 10th	Day	16% 6% 2 5% 3 3 3 3 5% 7% 48%	3436
	11th to 20th	Day	18% 7% 2 6% 5% 4 5% 3 4 6% 41%	3480
	21st to end	Day	15% 7% 2 6% 4 4 4 4 6% 7% 42%	3814
April	1st to 10th	Day	12% 6% 3 6% 3 3 4 4 6% 6% 47%	2090
	11th to 20th	Day	13% 7% 2 6% 4 4 4 3 6% 7% 45%	2164
	21st to end	Day	13% 6% 2 5% 5% 3 4 3 5% 7% 47%	2408
May	1st to 10th	Day	20% 8% 3 7% 4 3 3 4 5% 7% 37%	4082
	11th to 20th	Day	15% 6% 2 6% 3 4 4 3 4 6% 47%	4082
	21st to end	Day	15% 8% 3 6% 4 5% 5% 4 7% 8% 36%	4477
June	1st to 10th	Day	6% 4 2 4 4 4 6% 4 7% 10% 50%	2470
	11th to 20th	Day	5% 4 2 6% 4 4 5% 4 7% 9% 52%	2470
	21st to end	Day	5% 3 2 4 4 4 4 4 6% 8% 54%	2470
July	1st to 10th	Day	6% 4 2 5% 4 4 5% 4 6% 9% 52%	4120
	11th to 20th	Day	3 2 1 3 3 3 4 4 6% 9% 62%	4120
	21st to end	Day	6% 5% 2 6% 5% 5% 6% 4 7% 11% 43%	4465
August	1st to 10th	Day	1 1 1 3 2 3 3 3 5% 8% 70%	4104
	11th to 20th	Day	4 2 1 3 2 3 4 4 7% 9% 61%	4041
	21st to end	Day	3 2 1 5% 4 4 5% 4 8% 10% 55%	4065
September	1st to 10th	Day	9% 4 2 5% 3 4 3 3 6% 8% 53%	2090
	11th to 20th	Day	10% 5% 2 6% 5% 4 4 3 5% 7% 48%	2090
	21st to end	Day	7% 4 2 4 3 3 3 3 5% 7% 58%	2090
October	1st to 10th	Day	5% 3 1 4 3 4 4 3 5% 7% 61%	2038
	11th to 20th	Day	13% 3 1 4 2 2 3 2 4 5% 61%	1900
	21st to end	Day	14% 5% 2 4 2 2 2 2 3 4 60%	2090
November	1st to 10th	Day	13% 6% 2 4 3 2 3 2 4 5% 55%	1908
	11th to 20th	Day	7% 4 2 4 4 3 4 3 4 6% 59%	1786
	21st to end	Day	16% 7% 2 4 3 2 2 2 4 6% 52%	1710
December	1st to 10th	Day	16% 5% 2 5% 3 3 3 3 5% 6% 50%	1710
	11th to 20th	Day	16% 6% 3 6% 4 3 3 3 5% 4 47%	2161
	21st to end	Day	18% 6% 2 4 3 3 3 3 3 5% 50%	3135
January	1st to 10th	Night	13% 5% 2 5% 3 3 3 2 3 5% 58%	4108
	11th to 20th	Night	13% 4 1 3 2 2 2 2 3 4 65%	4120
	21st to end	Night	20% 7% 3 5% 3 2 2 2 3 4 49%	4532
February	1st to 10th	Night	15% 6% 2 5% 3 3 3 3 4 5% 52%	2371
	11th to 20th	Night	16% 7% 2 5% 3 3 3 2 3 5% 50%	2218
	21st to end	Night	18% 6% 2 4 3 2 3 2 4 5% 52%	1854
March	1st to 10th	Night	15% 8% 2 7% 4 3 4 3 5% 5% 44%	3419
	11th to 20th	Night	16% 6% 2 5% 3 3 4 3 5% 7% 46%	3480
	21st to end	Night	13% 6% 2 6% 4 3 3 3 4 6% 49%	3817
April	1st to 10th	Night	10% 5% 1 4 3 3 3 4 5% 8% 54%	2090
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 5% 6% 50%	1964
	21st to end	Night	11% 6% 2 4 3 3 3 3 5% 6% 55%	1767
May	1st to 10th	Night	20% 8% 2 6% 4 4 3 3 5% 7% 38%	2823
	11th to 20th	Night	12% 6% 2 6% 5% 3 3 3 4 6% 49%	2823
	21st to end	Night	12% 6% 2 5% 4 4 4 3 5% 9% 47%	3090
June	1st to 10th	Night	5% 2 1 3 4 4 4 4 6% 9% 58%	1710
	11th to 20th	Night	4 3 1 3 3 3 3 3 5% 11% 62%	1710
	21st to end	Night	3 3 1 4 3 3 4 4 6% 10% 58%	1710
July	1st to 10th	Night	4 3 1 4 3 3 3 3 5% 10% 60%	2850
	11th to 20th	Night	3 2 1 2 2 2 3 2 5% 10% 67%	2850
	21st to end	Night	4 4 2 5% 4 4 5% 4 7% 9% 53%	3098
August	1st to 10th	Night	1 1 2 1 1 2 2 4 9% 77%	2836
	11th to 20th	Night	3 2 1 2 2 2 2 2 6% 10% 68%	2798
	21st to end	Night	3 2 1 3 2 3 4 3 6% 9% 63%	3588
September	1st to 10th	Night	8% 5% 2 5% 3 3 3 3 6% 8% 56%	2090
	11th to 20th	Night	11% 4 2 4 3 3 3 3 5% 7% 54%	2090
	21st to end	Night	6% 3 1 3 2 3 3 4 4 7% 64%	2090
October	1st to 10th	Night	6% 3 1 3 3 3 3 3 5% 7% 64%	2122
	11th to 20th	Night	12% 4 1 3 2 2 3 2 4 5% 64%	2280
	21st to end	Night	15% 5% 2 3 2 2 3 2 3 3 61%	2508
November	1st to 10th	Night	10% 5% 2 5% 3 3 3 2 3 4 61%	2292
	11th to 20th	Night	7% 5% 1 4 3 3 4 3 5% 5% 59%	2391
	21st to end	Night	15% 6% 2 5% 2 3 3 3 3 6% 53%	2470
December	1st to 10th	Night	13% 5% 2 4 3 3 3 2 4 5% 55%	2470
	11th to 20th	Night	14% 6% 2 5% 4 3 3 3 4 5% 51%	3036
	21st to end	Night	17% 6% 1 4 3 2 2 2 3 5% 54%	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	30% 5% 7% 20% 33% 6%	2848
	11th to 20th	Day	28% 3 9% 22% 31% 8%	2850
	21st to end	Day	44% 2 5% 18% 23% 8%	3135
February	1st to 10th	Day	42% 4 7% 17% 21% 10%	1824
	11th to 20th	Day	42% 3 7% 19% 20% 9%	1859
	21st to end	Day	39% 2 5% 15% 24% 14%	1598
March	1st to 10th	Day	35% 6% 8% 16% 28% 8%	3436
	11th to 20th	Day	43% 6% 10% 21% 16% 4	3480
	21st to end	Day	38% 7% 12% 20% 19% 5%	3814
April	1st to 10th	Day	36% 6% 10% 20% 18% 10%	2090
	11th to 20th	Day	38% 6% 9% 17% 21% 8%	2164
	21st to end	Day	36% 7% 9% 20% 24% 5%	2408
May	1st to 10th	Day	45% 7% 10% 18% 15% 4	4120
	11th to 20th	Day	38% 6% 9% 23% 23% 2	4086
	21st to end	Day	43% 9% 13% 20% 11% 5%	4489
June	1st to 10th	Day	26% 9% 17% 28% 17% 3	2470
	11th to 20th	Day	28% 6% 14% 29% 19% 5%	2470
	21st to end	Day	26% 7% 12% 29% 22% 4	2470
July	1st to 10th	Day	27% 8% 15% 38% 12% 1	4056
	11th to 20th	Day	17% 6% 12% 40% 22% 3	4051
	21st to end	Day	32% 8% 15% 31% 14%	4325
August	1st to 10th	Day	12% 5% 12% 29% 36% 5%	4090
	11th to 20th	Day	18% 6% 14% 41% 19% 2	4080
	21st to end	Day	22% 9% 18% 35% 14% 2	4064
September	1st to 10th	Day	29% 5% 10% 23% 21% 12%	2090
	11th to 20th	Day	35% 7% 11% 19% 22% 7%	2090
	21st to end	Day	24% 5% 9% 22% 26% 13%	2090
October	1st to 10th	Day	14% 3 6% 14% 33% 29%	3389
	11th to 20th	Day	17% 3 5% 21% 32% 22%	3140
	21st to end	Day	23% 4 6% 27% 30% 10%	3428
November	1st to 10th	Day	32% 4 8% 22% 24% 10%	1908
	11th to 20th	Day	27% 4 10% 20% 29% 10%	1786
	21st to end	Day	35% 3 6% 22% 24% 10%	1710
December	1st to 10th	Day	35% 5% 8% 21% 23% 7%	1710
	11th to 20th	Day	40% 5% 6% 14% 26% 9%	2159
	21st to end	Day	38% 4 6% 23% 22% 9%	3135
January	1st to 10th	Night	29% 4 7% 19% 32% 10%	4108
	11th to 20th	Night	26% 3 7% 20% 29% 14%	4120
	21st to end	Night	41% 4 5% 15% 26% 9%	4532
February	1st to 10th	Night	37% 4 7% 17% 21% 14%	2371
	11th to 20th	Night	38% 3 7% 16% 25% 11%	2218
	21st to end	Night	36% 4 8% 15% 21% 16%	1854
March	1st to 10th	Night	41% 5% 7% 13% 22% 11%	3419
	11th to 20th	Night	37% 7% 11% 19% 20% 7%	3480
	21st to end	Night	36% 5% 9% 20% 25% 5%	3817
April	1st to 10th	Night	29% 5% 11% 21% 20% 14%	2090
	11th to 20th	Night	34% 6% 8% 19% 18% 15%	1964
	21st to end	Night	30% 5% 9% 22% 28% 5%	1767
May	1st to 10th	Night	44% 8% 10% 19% 13% 7%	2850
	11th to 20th	Night	35% 7% 13% 19% 25% 2	2824
	21st to end	Night	33% 9% 15% 25% 13% 6%	3099
June	1st to 10th	Night	20% 8% 16% 30% 20% 5%	1710
	11th to 20th	Night	18% 5% 13% 34% 21% 8%	1710
	21st to end	Night	19% 7% 14% 28% 26% 6%	1710
July	1st to 10th	Night	19% 6% 15% 43% 14% 2	2805
	11th to 20th	Night	14% 5% 12% 41% 25% 4	2796
	21st to end	Night	24% 7% 16% 35% 16% 1	2999
August	1st to 10th	Night	7% 3 11% 32% 41% 6%	2826
	11th to 20th	Night	13% 4 14% 40% 24% 5%	2825
	21st to end	Night	16% 7% 21% 34% 20% 3	3588
September	1st to 10th	Night	26% 6% 11% 21% 24% 11%	2090
	11th to 20th	Night	30% 5% 13% 19% 22% 11%	2090
	21st to end	Night	20% 5% 9% 22% 29% 16%	2090
October	1st to 10th	Night	12% 3 6% 15% 28% 36%	3538
	11th to 20th	Night	15% 2 5% 19% 32% 26%	3779
	21st to end	Night	25% 3 4 22% 30% 16%	4120
November	1st to 10th	Night	28% 4 7% 19% 27% 14%	2292
	11th to 20th	Night	25% 5% 8% 20% 28% 15%	2391
	21st to end	Night	34% 4 7% 16% 27% 11%	2470
December	1st to 10th	Night	32% 5% 7% 22% 23% 12%	2470
	11th to 20th	Night	36% 4 6% 15% 27% 12%	3037
	21st to end	Night	34% 3 7% 18% 26% 13%	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% 14% 36% 26% 4	270
	11th to 20th	Day	19% 16% 37% 21% 6% 1	270
	21st to end	Day	20% 14% 39% 19% 9%	297
February	1st to 10th	Day	21% 19% 36% 20% 4	270
	11th to 20th	Day	23% 21% 39% 14% 3	270
	21st to end	Day	28% 21% 36% 12% 3	225
March	1st to 10th	Day	23% 19% 35% 19% 4	270
	11th to 20th	Day	25% 13% 40% 17% 4	270
	21st to end	Day	16% 21% 42% 16% 5%	297
April	1st to 10th	Day	19% 17% 37% 20% 7%	270
	11th to 20th	Day	20% 14% 36% 24% 6%	362
	21st to end	Day	16% 17% 35% 24% 7% 1	588
May	1st to 10th	Day	13% 14% 36% 30% 7% 1	653
	11th to 20th	Day	15% 7% 32% 30% 13% 3	675
	21st to end	Day	13% 7% 29% 32% 16% 3	734
June	1st to 10th	Day	6% 3 16% 40% 26% 9%	680
	11th to 20th	Day	6% 3 19% 41% 25% 7%	680
	21st to end	Day	4 2 13% 39% 32% 9%	680
July	1st to 10th	Day	6% 1 12% 35% 33% 12%	671
	11th to 20th	Day	2 1 7% 37% 40% 13%	668
	21st to end	Day	3 1 7% 32% 43% 13%	739
August	1st to 10th	Day	2 7% 34% 45% 11%	676
	11th to 20th	Day	8% 1 5% 36% 41% 9%	665
	21st to end	Day	4 1 5% 31% 42% 17%	476
September	1st to 10th	Day	8% 1 9% 22% 44% 17%	300
	11th to 20th	Day	4 2 7% 29% 43% 15%	300
	21st to end	Day	12% 3 9% 31% 31% 15%	300
October	1st to 10th	Day	2 2 23% 33% 32% 9%	300
	11th to 20th	Day	10% 7% 30% 31% 18% 3	300
	21st to end	Day	22% 12% 24% 25% 16% 2	330
November	1st to 10th	Day	21% 7% 33% 26% 9% 3	285
	11th to 20th	Day	11% 11% 31% 31% 12% 3	270
	21st to end	Day	20% 13% 33% 26% 7% 1	270
December	1st to 10th	Day	18% 13% 34% 23% 9% 3	270
	11th to 20th	Day	21% 12% 39% 20% 8%	270
	21st to end	Day	20% 14% 40% 21% 6%	297
January	1st to 10th	Night	14% 9% 38% 31% 8%	950
	11th to 20th	Night	19% 12% 32% 32% 4 1	950
	21st to end	Night	18% 12% 34% 31% 6%	1045
February	1st to 10th	Night	20% 11% 36% 27% 5%	851
	11th to 20th	Night	20% 12% 39% 26% 3	744
	21st to end	Night	21% 17% 41% 19% 3	598
March	1st to 10th	Night	19% 12% 36% 28% 5%	570
	11th to 20th	Night	17% 10% 41% 29% 4	570
	21st to end	Night	14% 13% 41% 27% 5%	627
April	1st to 10th	Night	11% 13% 44% 28% 5%	570
	11th to 20th	Night	16% 12% 41% 26% 5%	563
	21st to end	Night	15% 9% 41% 28% 6% 1	570
May	1st to 10th	Night	10% 9% 41% 32% 6% 1	570
	11th to 20th	Night	10% 6% 37% 32% 13% 1	561
	21st to end	Night	9% 5% 34% 38% 13% 1	617
June	1st to 10th	Night	5% 2 19% 48% 24% 2	570
	11th to 20th	Night	4 2 28% 51% 15%	570
	21st to end	Night	3 1 19% 47% 27% 3	570
July	1st to 10th	Night	4 16% 46% 30% 4	555
	11th to 20th	Night	3 12% 49% 33% 2	552
	21st to end	Night	2 8% 50% 35% 4	624
August	1st to 10th	Night	2 6% 54% 35% 3	567
	11th to 20th	Night	6% 1 8% 48% 33% 5%	564
	21st to end	Night	3 1 8% 41% 41% 5%	627
September	1st to 10th	Night	9% 2 10% 40% 35% 4	570
	11th to 20th	Night	12% 2 10% 40% 34% 2	570
	21st to end	Night	7% 1 16% 41% 31% 5%	570
October	1st to 10th	Night	7% 1 22% 39% 28% 3	602
	11th to 20th	Night	13% 5% 28% 37% 16% 1	760
	21st to end	Night	17% 8% 28% 31% 15% 1	836
November	1st to 10th	Night	12% 4 32% 37% 14% 1	764
	11th to 20th	Night	9% 10% 32% 35% 14% 1	871
	21st to end	Night	19% 10% 34% 28% 9% 1	950
December	1st to 10th	Night	16% 9% 36% 33% 6%	950
	11th to 20th	Night	20% 9% 33% 31% 6%	950
	21st to end	Night	18% 10% 35% 30% 6%	1045

Page generated at 2024-11-03 12:19:03. Version ac07

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