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 2024-11-02.

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% 8% 3 8% 5% 5% 5% 3 5% 6% 39%	101530
	Night	15% 8% 3 7% 5% 4 4 3 5% 5% 40%	97602
Transparency	Day	45% 8% 12% 18% 13% 4	101276
	Night	45% 8% 13% 19% 12% 4	97446
Seeing	Day	15% 10% 20% 26% 21% 8%	14709
	Night	17% 6% 19% 36% 21% 2	23620

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	25% 16% 8% 16% 8% 6% 5% 3 3 4 7%	2539
	11th to 20th	Day	33% 12% 4 9% 6% 5% 5% 3 4 4 15%	2540
	21st to end	Day	23% 14% 4 11% 7% 7% 6% 5% 5% 6% 13%	3146
February	1st to 10th	Day	24% 12% 3 11% 7% 6% 6% 4 5% 6% 16%	1710
	11th to 20th	Day	22% 13% 4 11% 6% 7% 5% 4 5% 4 18%	1665
	21st to end	Day	21% 15% 5% 11% 6% 7% 5% 4 4 4 19%	1470
March	1st to 10th	Day	14% 11% 4 11% 7% 7% 7% 5% 6% 7% 19%	3349
	11th to 20th	Day	15% 10% 3 8% 6% 5% 4 3 4 5% 38%	3490
	21st to end	Day	19% 11% 4 11% 8% 7% 7% 5% 5% 6% 18%	3871
April	1st to 10th	Day	20% 12% 5% 10% 6% 7% 6% 4 5% 6% 20%	2280
	11th to 20th	Day	19% 12% 3 9% 7% 5% 5% 4 6% 5% 27%	2262
	21st to end	Day	17% 9% 3 8% 6% 6% 6% 5% 6% 7% 27%	2470
May	1st to 10th	Day	17% 8% 3 8% 5% 5% 4 4 5% 5% 36%	4282
	11th to 20th	Day	10% 5% 2 5% 3 4 3 3 4 7% 54%	4377
	21st to end	Day	15% 7% 2 7% 6% 6% 7% 5% 7% 7% 30%	4813
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	13% 7% 2 7% 5% 5% 4 3 6% 5% 41%	1900
	11th to 20th	Day	14% 8% 4 9% 7% 6% 6% 3 5% 7% 31%	1900
	21st to end	Day	17% 11% 4 10% 6% 5% 5% 4 5% 6% 28%	2087
November	1st to 10th	Day	21% 11% 6% 11% 7% 7% 6% 4 5% 4 16%	1565
	11th to 20th	Day	22% 13% 4 11% 6% 6% 6% 3 5% 6% 18%	1520
	21st to end	Day	21% 11% 4 10% 7% 6% 5% 3 5% 5% 22%	1520
December	1st to 10th	Day	20% 14% 5% 11% 7% 4 4 3 5% 5% 23%	1520
	11th to 20th	Day	21% 10% 5% 14% 7% 7% 6% 4 7% 7% 13%	1928
	21st to end	Day	25% 16% 7% 18% 7% 5% 4 3 3 4 7%	2794
January	1st to 10th	Night	25% 18% 6% 11% 6% 6% 4 3 5% 4 12%	4406
	11th to 20th	Night	30% 15% 5% 9% 6% 4 4 3 4 4 17%	4416
	21st to end	Night	27% 12% 5% 11% 6% 5% 4 3 4 5% 17%	4521
February	1st to 10th	Night	18% 14% 4 10% 7% 5% 6% 4 5% 5% 22%	2470
	11th to 20th	Night	21% 11% 4 8% 6% 5% 5% 4 5% 5% 26%	2402
	21st to end	Night	19% 12% 4 10% 5% 6% 5% 4 5% 6% 24%	1983
March	1st to 10th	Night	11% 9% 3 10% 7% 8% 8% 6% 6% 6% 24%	3522
	11th to 20th	Night	12% 7% 2 6% 5% 4 4 4 6% 6% 44%	3490
	21st to end	Night	16% 12% 4 11% 7% 7% 6% 4 6% 6% 21%	3781
April	1st to 10th	Night	20% 10% 3 8% 5% 5% 5% 3 5% 7% 28%	1900
	11th to 20th	Night	15% 9% 3 6% 6% 5% 5% 3 5% 7% 35%	1861
	21st to end	Night	15% 7% 3 7% 6% 4 5% 5% 6% 7% 35%	1710
May	1st to 10th	Night	16% 8% 2 6% 4 4 4 3 4 5% 44%	2682
	11th to 20th	Night	8% 4 2 4 3 4 3 2 4 5% 61%	2516
	21st to end	Night	10% 5% 2 6% 4 5% 5% 5% 7% 8% 43%	2762
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	12% 5% 2 6% 4 3 4 3 5% 6% 51%	2280
	11th to 20th	Night	13% 6% 2 6% 4 5% 5% 5% 5% 7% 43%	2280
	21st to end	Night	18% 8% 3 8% 5% 4 4 3 5% 5% 39%	2510
November	1st to 10th	Night	21% 8% 3 9% 6% 5% 5% 4 6% 6% 27%	2531
	11th to 20th	Night	24% 9% 4 9% 6% 6% 5% 4 5% 5% 23%	2660
	21st to end	Night	19% 8% 3 10% 7% 5% 5% 3 5% 6% 29%	2660
December	1st to 10th	Night	21% 10% 4 9% 6% 5% 4 4 6% 5% 26%	2660
	11th to 20th	Night	21% 11% 5% 11% 7% 6% 5% 3 5% 6% 19%	3276
	21st to end	Night	22% 13% 5% 13% 7% 5% 5% 4 5% 5% 18%	4862

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	79% 9% 5% 5% 2 1	2539
	11th to 20th	Day	71% 8% 8% 9% 2 2	2540
	21st to end	Day	72% 9% 7% 7% 5%	3146
February	1st to 10th	Day	68% 9% 9% 10% 4	1710
	11th to 20th	Day	67% 9% 9% 10% 4 1	1674
	21st to end	Day	68% 7% 9% 10% 6% 1	1470
March	1st to 10th	Day	62% 9% 14% 12% 3	3349
	11th to 20th	Day	49% 7% 9% 24% 11%	3490
	21st to end	Day	64% 11% 12% 8% 4	3871
April	1st to 10th	Day	65% 8% 12% 12% 4	2280
	11th to 20th	Day	58% 9% 10% 13% 8% 2	2265
	21st to end	Day	55% 10% 12% 14% 7% 1	2470
May	1st to 10th	Day	47% 9% 12% 20% 12%	4282
	11th to 20th	Day	29% 7% 18% 30% 15% 1	4380
	21st to end	Day	45% 15% 22% 15% 2	4814
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	42% 7% 10% 19% 18% 3	1900
	11th to 20th	Day	50% 8% 11% 17% 12% 1	1900
	21st to end	Day	55% 8% 9% 14% 13% 1	2087
November	1st to 10th	Day	66% 8% 10% 12% 4	1565
	11th to 20th	Day	65% 9% 9% 9% 6% 1	1520
	21st to end	Day	61% 10% 7% 11% 11% 1	1520
December	1st to 10th	Day	63% 7% 9% 12% 9% 1	1520
	11th to 20th	Day	67% 10% 10% 11% 2	1928
	21st to end	Day	79% 7% 7% 4 3	2794
January	1st to 10th	Night	73% 9% 8% 5% 4 1	4406
	11th to 20th	Night	70% 6% 7% 11% 4 2	4416
	21st to end	Night	72% 6% 8% 8% 6% 1	4521
February	1st to 10th	Night	63% 10% 11% 12% 4	2470
	11th to 20th	Night	57% 10% 12% 13% 6% 2	2404
	21st to end	Night	60% 8% 12% 11% 7% 2	1983
March	1st to 10th	Night	57% 9% 12% 17% 4	3522
	11th to 20th	Night	40% 9% 14% 26% 11% 1	3490
	21st to end	Night	62% 10% 12% 14% 2	3781
April	1st to 10th	Night	56% 9% 16% 13% 6%	1900
	11th to 20th	Night	48% 8% 17% 17% 7% 3	1861
	21st to end	Night	47% 9% 14% 21% 7% 2	1710
May	1st to 10th	Night	40% 8% 14% 27% 10% 1	2682
	11th to 20th	Night	26% 5% 17% 35% 16% 3	2516
	21st to end	Night	32% 14% 34% 17% 3	2762
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	34% 6% 10% 27% 18% 4	2280
	11th to 20th	Night	39% 9% 13% 21% 15% 3	2280
	21st to end	Night	46% 8% 11% 18% 15% 2	2510
November	1st to 10th	Night	57% 9% 10% 16% 7%	2531
	11th to 20th	Night	62% 8% 10% 11% 7% 2	2660
	21st to end	Night	55% 8% 11% 11% 13% 2	2660
December	1st to 10th	Night	58% 8% 11% 12% 11% 1	2660
	11th to 20th	Night	64% 9% 9% 12% 6%	3276
	21st to end	Night	66% 10% 11% 9% 3	4862

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	29% 17% 22% 18% 12% 3	180
	11th to 20th	Day	27% 14% 16% 27% 12% 4	180
	21st to end	Day	24% 10% 19% 26% 16% 5%	407
February	1st to 10th	Day	25% 16% 19% 21% 15% 5%	370
	11th to 20th	Day	27% 11% 27% 19% 13% 3	365
	21st to end	Day	21% 23% 22% 18% 13% 2	334
March	1st to 10th	Day	21% 13% 28% 25% 10% 2	460
	11th to 20th	Day	23% 10% 24% 23% 17% 4	460
	21st to end	Day	23% 16% 23% 22% 14% 2	506
April	1st to 10th	Day	23% 17% 23% 18% 15% 5%	460
	11th to 20th	Day	23% 13% 26% 21% 12% 6%	452
	21st to end	Day	17% 14% 27% 23% 14% 4	460
May	1st to 10th	Day	14% 15% 23% 24% 18% 6%	463
	11th to 20th	Day	18% 11% 20% 24% 17% 10%	488
	21st to end	Day	12% 10% 20% 25% 22% 11%	529
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	19% 14% 24% 25% 13% 6%	536
November	1st to 10th	Day	22% 12% 24% 26% 12% 3	217
	11th to 20th	Day	19% 12% 25% 19% 18% 7%	180
	21st to end	Day	23% 11% 22% 21% 18% 7%	180
December	1st to 10th	Day	26% 11% 16% 27% 12% 7%	180
	11th to 20th	Day	29% 9% 19% 29% 10% 3	180
	21st to end	Day	27% 11% 24% 21% 14% 3	198
January	1st to 10th	Night	29% 9% 21% 25% 13% 3	760
	11th to 20th	Night	26% 9% 18% 25% 18% 3	760
	21st to end	Night	23% 6% 17% 34% 18% 3	836
February	1st to 10th	Night	20% 7% 23% 30% 18% 2	760
	11th to 20th	Night	22% 8% 21% 31% 17% 1	744
	21st to end	Night	22% 11% 23% 32% 12%	628
March	1st to 10th	Night	18% 9% 23% 34% 15% 1	760
	11th to 20th	Night	20% 6% 21% 35% 17% 1	760
	21st to end	Night	22% 8% 24% 29% 16% 1	836
April	1st to 10th	Night	23% 8% 21% 30% 18% 1	760
	11th to 20th	Night	17% 8% 25% 33% 16% 1	733
	21st to end	Night	15% 5% 18% 41% 20% 1	570
May	1st to 10th	Night	12% 4 25% 40% 17% 1	470
	11th to 20th	Night	12% 4 18% 44% 21% 1	374
	21st to end	Night	11% 3 22% 39% 23% 1	411
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% 6% 22% 31% 18% 4	836
November	1st to 10th	Night	22% 6% 19% 35% 17% 1	744
	11th to 20th	Night	25% 9% 20% 29% 14% 2	760
	21st to end	Night	20% 6% 19% 34% 19% 2	760
December	1st to 10th	Night	24% 5% 19% 33% 17% 3	760
	11th to 20th	Night	26% 8% 24% 27% 14% 1	760
	21st to end	Night	28% 9% 23% 27% 12% 1	836

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