Dallas (OR)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dallas (OR) clear sky chart from 2005-11-06 to 2025-05-26.

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	15% 8% 3 8% 5% 5% 5% 4 5% 6% 37%	118268
	Night	16% 8% 3 8% 5% 5% 4 3 5% 6% 38%	119835
Transparency	Day	46% 8% 12% 18% 13% 4	118014
	Night	46% 8% 12% 19% 12% 3	119679
Seeing	Day	15% 10% 20% 26% 21% 8%	15337
	Night	17% 6% 19% 36% 21% 2	24385

By Month

Percentage Cloud Cover SW (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	27% 15% 7% 15% 7% 5% 5% 3 3 4 9%	3639
	11th to 20th	Day	23% 9% 3 9% 7% 6% 5% 4 5% 5% 23%	3654
	21st to end	Day	18% 10% 3 9% 6% 6% 5% 4 5% 6% 29%	4510
February	1st to 10th	Day	23% 12% 3 11% 7% 7% 6% 4 5% 6% 15%	1800
	11th to 20th	Day	23% 14% 4 11% 6% 6% 5% 4 5% 5% 18%	1755
	21st to end	Day	21% 15% 5% 11% 6% 6% 5% 4 4 4 19%	1545
March	1st to 10th	Day	14% 11% 4 10% 7% 7% 7% 5% 6% 7% 20%	4820
	11th to 20th	Day	21% 13% 4 9% 6% 5% 4 4 4 4 27%	5000
	21st to end	Day	19% 11% 5% 11% 8% 7% 7% 5% 6% 7% 14%	5545
April	1st to 10th	Day	20% 12% 5% 10% 7% 8% 6% 4 5% 6% 19%	2400
	11th to 20th	Day	18% 11% 3 8% 6% 4 5% 4 5% 5% 29%	2383
	21st to end	Day	16% 9% 3 8% 6% 6% 6% 5% 6% 7% 28%	2600
May	1st to 10th	Day	17% 8% 3 8% 5% 5% 4 4 5% 5% 37%	4417
	11th to 20th	Day	10% 5% 2 5% 3 4 3 3 5% 7% 53%	4517
	21st to end	Day	15% 7% 2 7% 6% 6% 7% 5% 7% 7% 30%	4886
June	1st to 10th	Day	17% 8% 3 8% 6% 5% 5% 3 5% 5% 34%	2660
	11th to 20th	Day	14% 8% 3 7% 5% 6% 6% 5% 7% 8% 32%	2660
	21st to end	Day	7% 4 2 5% 4 4 4 3 5% 6% 56%	2660
July	1st to 10th	Day	3 2 1 3 2 2 2 2 3 5% 75%	4420
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 4 77%	4420
	21st to end	Day	4 3 1 2 1 2 2 2 3 4 77%	4730
August	1st to 10th	Day	2 3 1 3 2 3 3 2 4 6% 71%	4091
	11th to 20th	Day	5% 4 2 5% 4 4 5% 4 6% 8% 55%	4026
	21st to end	Day	7% 5% 2 4 3 3 3 3 5% 7% 59%	4320
September	1st to 10th	Day	6% 3 1 3 2 3 3 3 5% 7% 65%	2280
	11th to 20th	Day	9% 6% 2 7% 4 5% 4 4 5% 7% 45%	2247
	21st to end	Day	13% 5% 1 6% 4 4 5% 3 4 7% 47%	2018
October	1st to 10th	Day	11% 5% 2 6% 4 4 4 3 6% 6% 49%	3180
	11th to 20th	Day	13% 6% 3 9% 7% 6% 6% 4 6% 8% 30%	3161
	21st to end	Day	17% 10% 3 10% 6% 6% 7% 4 6% 8% 23%	3433
November	1st to 10th	Day	20% 11% 6% 11% 7% 7% 6% 4 6% 4 17%	1639
	11th to 20th	Day	23% 13% 4 11% 7% 6% 6% 3 5% 6% 17%	1600
	21st to end	Day	21% 12% 4 11% 7% 7% 5% 3 5% 5% 22%	1600
December	1st to 10th	Day	17% 10% 4 11% 6% 5% 4 3 5% 5% 31%	2620
	11th to 20th	Day	24% 13% 5% 14% 8% 6% 6% 4 6% 6% 10%	3028
	21st to end	Day	29% 17% 7% 17% 7% 5% 4 3 3 3 6%	4004
January	1st to 10th	Night	27% 17% 5% 11% 6% 6% 4 3 4 4 13%	6306
	11th to 20th	Night	21% 12% 4 8% 6% 4 4 3 4 6% 28%	6303
	21st to end	Night	20% 10% 4 8% 5% 4 4 2 4 5% 34%	6468
February	1st to 10th	Night	17% 14% 4 10% 8% 5% 6% 4 5% 6% 21%	2600
	11th to 20th	Night	21% 11% 4 8% 6% 5% 5% 4 5% 5% 26%	2532
	21st to end	Night	20% 11% 4 10% 5% 6% 5% 4 5% 6% 25%	2084
March	1st to 10th	Night	12% 8% 3 9% 7% 9% 8% 6% 7% 7% 24%	5071
	11th to 20th	Night	17% 12% 3 9% 5% 5% 4 3 5% 5% 32%	5000
	21st to end	Night	19% 12% 4 11% 7% 6% 6% 4 6% 7% 18%	5429
April	1st to 10th	Night	20% 10% 3 9% 5% 5% 5% 3 5% 7% 28%	2000
	11th to 20th	Night	15% 9% 3 6% 6% 5% 4 3 5% 7% 37%	1960
	21st to end	Night	14% 7% 3 7% 6% 4 5% 5% 6% 7% 36%	1800
May	1st to 10th	Night	16% 8% 2 6% 4 4 4 3 4 5% 45%	2767
	11th to 20th	Night	8% 5% 2 4 3 4 3 3 4 5% 59%	2596
	21st to end	Night	10% 5% 2 6% 4 4 5% 5% 7% 8% 43%	2805
June	1st to 10th	Night	15% 6% 3 6% 5% 4 4 3 6% 6% 43%	1520
	11th to 20th	Night	11% 7% 2 4 4 3 4 3 6% 7% 49%	1520
	21st to end	Night	4 5% 1 5% 3 3 3 2 4 6% 65%	1520
July	1st to 10th	Night	2 1 2 1 1 1 1 2 3 84%	2540
	11th to 20th	Night	3 2 1 2 2 1 1 1 2 3 81%	2540
	21st to end	Night	2 1 1 2 1 1 1 1 3 4 83%	2819
August	1st to 10th	Night	1 2 1 2 1 2 3 2 4 4 79%	2848
	11th to 20th	Night	6% 3 1 4 2 3 3 3 4 7% 65%	2812
	21st to end	Night	7% 3 2 4 2 2 3 2 3 4 68%	3353
September	1st to 10th	Night	4 2 1 3 2 2 3 2 3 6% 71%	1900
	11th to 20th	Night	8% 4 2 6% 4 4 4 4 4 6% 54%	1928
	21st to end	Night	9% 4 2 5% 3 4 4 2 5% 7% 56%	2161
October	1st to 10th	Night	9% 4 2 5% 3 3 3 3 5% 7% 56%	3800
	11th to 20th	Night	12% 6% 2 6% 5% 5% 5% 5% 6% 9% 39%	3777
	21st to end	Night	19% 9% 3 9% 5% 5% 5% 4 6% 6% 30%	4134
November	1st to 10th	Night	21% 8% 3 9% 6% 5% 5% 4 6% 6% 27%	2654
	11th to 20th	Night	25% 10% 4 10% 7% 6% 5% 4 5% 5% 22%	2800
	21st to end	Night	19% 8% 3 10% 7% 6% 5% 3 5% 6% 29%	2800
December	1st to 10th	Night	14% 8% 3 8% 5% 5% 4 3 5% 8% 36%	4560
	11th to 20th	Night	28% 14% 6% 12% 6% 6% 4 3 4 4 13%	5176
	21st to end	Night	25% 12% 5% 13% 7% 6% 5% 4 4 4 14%	6952

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	77% 8% 5% 7% 3	3639
	11th to 20th	Day	54% 13% 8% 18% 7% 1	3654
	21st to end	Day	55% 9% 6% 12% 15% 3	4510
February	1st to 10th	Day	69% 9% 9% 10% 4	1800
	11th to 20th	Day	67% 9% 9% 10% 4 2	1764
	21st to end	Day	67% 7% 8% 10% 6% 1	1545
March	1st to 10th	Day	58% 10% 15% 13% 4	4820
	11th to 20th	Day	59% 7% 7% 18% 8%	5000
	21st to end	Day	66% 11% 12% 8% 3	5545
April	1st to 10th	Day	65% 8% 12% 12% 4	2400
	11th to 20th	Day	56% 9% 10% 14% 9% 2	2386
	21st to end	Day	54% 10% 13% 15% 8% 1	2600
May	1st to 10th	Day	46% 9% 12% 20% 12%	4417
	11th to 20th	Day	30% 7% 18% 30% 14% 1	4520
	21st to end	Day	45% 15% 22% 15% 2	4887
June	1st to 10th	Day	50% 8% 16% 20% 6% 1	2660
	11th to 20th	Day	47% 10% 19% 18% 6%	2660
	21st to end	Day	28% 7% 19% 29% 13% 4	2660
July	1st to 10th	Day	14% 4 9% 18% 23% 32%	4351
	11th to 20th	Day	13% 3 6% 20% 39% 19%	4345
	21st to end	Day	12% 4 12% 28% 38% 7%	4581
August	1st to 10th	Day	15% 5% 11% 31% 26% 13%	4076
	11th to 20th	Day	26% 8% 18% 29% 15% 4	4065
	21st to end	Day	24% 7% 14% 26% 22% 6%	4319
September	1st to 10th	Day	19% 5% 13% 31% 21% 12%	2280
	11th to 20th	Day	35% 9% 15% 20% 16% 6%	2247
	21st to end	Day	37% 6% 15% 23% 14% 5%	2018
October	1st to 10th	Day	33% 8% 8% 25% 25% 2	3180
	11th to 20th	Day	47% 10% 15% 16% 11% 1	3161
	21st to end	Day	52% 11% 9% 17% 10% 1	3433
November	1st to 10th	Day	65% 8% 10% 12% 4	1639
	11th to 20th	Day	66% 9% 9% 9% 6% 1	1600
	21st to end	Day	62% 10% 7% 10% 10% 1	1600
December	1st to 10th	Day	51% 8% 10% 18% 12%	2620
	11th to 20th	Day	72% 9% 9% 8% 1	3028
	21st to end	Day	79% 8% 7% 4 2	4004
January	1st to 10th	Night	73% 8% 8% 6% 4 1	6306
	11th to 20th	Night	54% 8% 8% 21% 8% 1	6303
	21st to end	Night	55% 5% 6% 14% 16% 4	6468
February	1st to 10th	Night	62% 10% 11% 12% 5%	2600
	11th to 20th	Night	57% 10% 12% 13% 6% 2	2534
	21st to end	Night	59% 8% 12% 12% 7% 2	2084
March	1st to 10th	Night	55% 9% 13% 17% 6%	5071
	11th to 20th	Night	53% 10% 11% 19% 8% 1	5000
	21st to end	Night	62% 11% 14% 12% 2	5429
April	1st to 10th	Night	56% 9% 15% 14% 6%	2000
	11th to 20th	Night	46% 8% 17% 18% 8% 3	1960
	21st to end	Night	47% 9% 14% 21% 7% 2	1800
May	1st to 10th	Night	40% 8% 13% 27% 11% 1	2767
	11th to 20th	Night	27% 5% 16% 34% 15% 2	2596
	21st to end	Night	32% 14% 34% 17% 3	2805
June	1st to 10th	Night	41% 8% 16% 28% 6% 1	1520
	11th to 20th	Night	33% 8% 22% 28% 8%	1520
	21st to end	Night	23% 4 19% 36% 13% 4	1520
July	1st to 10th	Night	9% 2 9% 21% 28% 31%	2500
	11th to 20th	Night	12% 3 8% 19% 31% 27%	2492
	21st to end	Night	8% 3 12% 29% 40% 8%	2731
August	1st to 10th	Night	10% 4 10% 35% 34% 9%	2839
	11th to 20th	Night	18% 7% 22% 37% 13% 5%	2839
	21st to end	Night	20% 5% 15% 30% 24% 6%	3353
September	1st to 10th	Night	15% 5% 14% 32% 23% 11%	1900
	11th to 20th	Night	30% 7% 14% 25% 16% 8%	1928
	21st to end	Night	28% 7% 16% 24% 18% 7%	2161
October	1st to 10th	Night	26% 7% 9% 33% 22% 3	3800
	11th to 20th	Night	39% 8% 21% 20% 10% 2	3777
	21st to end	Night	50% 8% 12% 19% 9% 1	4134
November	1st to 10th	Night	56% 10% 11% 16% 7%	2654
	11th to 20th	Night	63% 8% 10% 10% 7% 2	2800
	21st to end	Night	55% 9% 11% 11% 13% 2	2800
December	1st to 10th	Night	43% 9% 10% 22% 16%	4560
	11th to 20th	Night	72% 9% 7% 8% 4	5176
	21st to end	Night	68% 12% 10% 8% 2	6952

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	30% 16% 23% 19% 11% 3	200
	11th to 20th	Day	25% 14% 16% 27% 13% 4	201
	21st to end	Day	23% 10% 19% 26% 17% 6%	440
February	1st to 10th	Day	25% 16% 20% 21% 14% 5%	400
	11th to 20th	Day	27% 12% 28% 19% 12% 3	395
	21st to end	Day	22% 23% 20% 20% 12% 2	361
March	1st to 10th	Day	20% 13% 29% 25% 11% 2	500
	11th to 20th	Day	25% 11% 23% 21% 17% 3	500
	21st to end	Day	23% 16% 23% 22% 13% 2	550
April	1st to 10th	Day	23% 17% 22% 18% 15% 5%	500
	11th to 20th	Day	21% 13% 26% 22% 14% 5%	492
	21st to end	Day	16% 13% 26% 24% 16% 5%	500
May	1st to 10th	Day	14% 14% 23% 25% 19% 6%	503
	11th to 20th	Day	18% 12% 21% 24% 16% 9%	528
	21st to end	Day	11% 10% 20% 25% 22% 11%	550
June	1st to 10th	Day	15% 10% 20% 24% 23% 8%	490
	11th to 20th	Day	14% 9% 26% 29% 18% 3	490
	21st to end	Day	5% 7% 19% 29% 32% 8%	490
July	1st to 10th	Day	3 4 17% 35% 29% 12%	486
	11th to 20th	Day	2 3 18% 33% 32% 12%	484
	21st to end	Day	2 3 14% 32% 36% 13%	531
August	1st to 10th	Day	3 2 11% 32% 34% 18%	487
	11th to 20th	Day	2 3 10% 28% 35% 21%	477
	21st to end	Day	5% 4 15% 32% 30% 13%	539
September	1st to 10th	Day	6% 3 18% 29% 31% 13%	490
	11th to 20th	Day	9% 7% 17% 27% 29% 11%	490
	21st to end	Day	11% 6% 22% 29% 25% 6%	490
October	1st to 10th	Day	12% 10% 21% 24% 24% 9%	490
	11th to 20th	Day	14% 12% 17% 25% 24% 9%	490
	21st to end	Day	18% 14% 24% 25% 13% 6%	536
November	1st to 10th	Day	21% 14% 24% 25% 13% 4	237
	11th to 20th	Day	22% 14% 24% 19% 17% 6%	200
	21st to end	Day	22% 12% 21% 22% 17% 8%	200
December	1st to 10th	Day	25% 10% 15% 27% 16% 7%	200
	11th to 20th	Day	29% 11% 21% 28% 9% 3	200
	21st to end	Day	28% 12% 25% 20% 13% 2	220
January	1st to 10th	Night	29% 9% 22% 25% 13% 3	800
	11th to 20th	Night	25% 9% 19% 26% 19% 3	800
	21st to end	Night	22% 6% 17% 34% 18% 3	880
February	1st to 10th	Night	20% 7% 24% 30% 18% 2	800
	11th to 20th	Night	22% 9% 22% 30% 16% 1	784
	21st to end	Night	22% 11% 22% 32% 12%	660
March	1st to 10th	Night	17% 9% 23% 35% 15% 1	800
	11th to 20th	Night	21% 7% 21% 34% 16% 1	800
	21st to end	Night	22% 9% 23% 28% 16% 1	880
April	1st to 10th	Night	22% 8% 20% 31% 17% 1	800
	11th to 20th	Night	17% 8% 25% 34% 15% 1	772
	21st to end	Night	15% 5% 18% 42% 20% 1	600
May	1st to 10th	Night	12% 3 25% 41% 17% 1	495
	11th to 20th	Night	12% 5% 18% 43% 21% 1	394
	21st to end	Night	11% 3 22% 39% 23% 1	422
June	1st to 10th	Night	15% 3 18% 42% 22%	380
	11th to 20th	Night	11% 1 26% 44% 16% 1	380
	21st to end	Night	7% 2 16% 55% 21%	380
July	1st to 10th	Night	4 2 13% 57% 24% 1	370
	11th to 20th	Night	4 1 20% 51% 24%	368
	21st to end	Night	1 1 13% 53% 30% 1	450
August	1st to 10th	Night	3 1 8% 45% 38% 4	567
	11th to 20th	Night	4 7% 40% 44% 3	564
	21st to end	Night	6% 1 16% 44% 32% 1	743
September	1st to 10th	Night	4 2 15% 41% 36% 1	760
	11th to 20th	Night	8% 3 14% 37% 32% 6%	760
	21st to end	Night	9% 4 13% 40% 29% 3	760
October	1st to 10th	Night	12% 3 19% 39% 26% 3	760
	11th to 20th	Night	15% 4 15% 36% 26% 4	760
	21st to end	Night	19% 7% 22% 31% 18% 4	836
November	1st to 10th	Night	22% 6% 19% 36% 17% 1	780
	11th to 20th	Night	26% 10% 20% 29% 14% 2	800
	21st to end	Night	20% 6% 20% 33% 19% 3	800
December	1st to 10th	Night	23% 5% 18% 33% 18% 3	800
	11th to 20th	Night	27% 8% 24% 27% 13% 1	800
	21st to end	Night	28% 10% 24% 26% 12% 1	880

Page generated at 2025-05-23 06:21:03. Version ac07

Copyright © 2025 Attilla Danko.