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 2026-09-29.

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% 7% 3 7% 5% 5% 4 3 5% 6% 43%	158687
	Night	14% 8% 3 7% 5% 4 4 3 5% 6% 42%	150145
Transparency	Day	40% 8% 13% 21% 14% 4	153460
	Night	42% 7% 13% 21% 13% 4	146373
Seeing	Day	14% 10% 20% 26% 21% 8%	17107
	Night	16% 6% 19% 36% 21% 2	25978

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% 16% 6% 14% 7% 6% 5% 3 4 4 8%	4722
	11th to 20th	Day	18% 7% 2 9% 7% 5% 5% 4 5% 6% 32%	4754
	21st to end	Day	16% 10% 3 10% 6% 6% 6% 4 5% 6% 27%	5843
February	1st to 10th	Day	23% 12% 3 11% 7% 7% 6% 4 5% 6% 16%	1890
	11th to 20th	Day	22% 14% 4 11% 6% 6% 5% 4 5% 4 18%	1845
	21st to end	Day	21% 15% 5% 11% 6% 7% 5% 4 4 4 18%	1620
March	1st to 10th	Day	14% 11% 4 11% 7% 7% 7% 5% 6% 7% 20%	4927
	11th to 20th	Day	22% 13% 4 9% 6% 5% 4 4 4 4 26%	5110
	21st to end	Day	19% 11% 5% 11% 8% 7% 7% 5% 6% 7% 14%	5667
April	1st to 10th	Day	19% 12% 4 10% 7% 7% 6% 4 5% 6% 20%	2520
	11th to 20th	Day	18% 11% 3 8% 7% 5% 5% 4 5% 6% 28%	2504
	21st to end	Day	16% 9% 3 8% 6% 6% 6% 5% 6% 7% 29%	2730
May	1st to 10th	Day	10% 6% 2 6% 4 4 4 4 6% 7% 48%	7927
	11th to 20th	Day	9% 6% 2 7% 5% 6% 5% 4 6% 9% 42%	8160
	21st to end	Day	11% 6% 2 6% 5% 5% 6% 4 6% 7% 42%	8992
June	1st to 10th	Day	16% 8% 3 7% 6% 4 5% 3 5% 6% 37%	2940
	11th to 20th	Day	13% 7% 3 6% 5% 5% 6% 5% 7% 8% 35%	2940
	21st to end	Day	7% 5% 2 5% 5% 5% 4 3 5% 7% 54%	2940
July	1st to 10th	Day	2 2 1 2 2 2 2 2 3 5% 77%	8219
	11th to 20th	Day	3 2 1 2 1 2 2 1 3 4 79%	8220
	21st to end	Day	3 2 1 2 1 2 2 2 3 5% 76%	8810
August	1st to 10th	Day	2 3 1 3 2 2 3 2 3 6% 74%	7547
	11th to 20th	Day	4 3 1 4 3 3 4 4 6% 8% 60%	7563
	21st to end	Day	6% 5% 1 4 3 3 3 3 5% 9% 59%	8016
September	1st to 10th	Day	6% 3 1 4 3 3 3 3 5% 7% 62%	2520
	11th to 20th	Day	8% 6% 2 7% 4 5% 5% 4 5% 7% 47%	2483
	21st to end	Day	13% 5% 1 6% 3 4 5% 3 4 7% 47%	2211
October	1st to 10th	Day	11% 5% 2 6% 4 4 4 3 6% 6% 49%	3280
	11th to 20th	Day	13% 6% 3 9% 7% 6% 6% 4 6% 8% 30%	3261
	21st to end	Day	17% 10% 4 10% 6% 6% 7% 4 6% 8% 22%	3543
November	1st to 10th	Day	21% 11% 6% 11% 7% 7% 6% 4 6% 5% 16%	1723
	11th to 20th	Day	23% 13% 4 11% 7% 6% 5% 3 4 6% 17%	1680
	21st to end	Day	21% 11% 4 11% 7% 6% 5% 4 5% 5% 21%	1680
December	1st to 10th	Day	17% 10% 4 11% 6% 5% 4 3 5% 5% 30%	2700
	11th to 20th	Day	24% 13% 5% 14% 8% 6% 6% 4 6% 6% 10%	3108
	21st to end	Day	28% 17% 7% 17% 7% 5% 4 3 3 3 6%	4092
January	1st to 10th	Night	27% 16% 5% 12% 7% 6% 4 3 5% 4 12%	8172
	11th to 20th	Night	17% 9% 3 9% 6% 4 4 3 4 6% 36%	8203
	21st to end	Night	19% 10% 4 9% 5% 5% 4 3 4 5% 32%	8371
February	1st to 10th	Night	17% 14% 4 10% 8% 5% 6% 4 5% 6% 22%	2730
	11th to 20th	Night	21% 11% 4 8% 6% 5% 5% 4 5% 5% 25%	2662
	21st to end	Night	20% 11% 4 10% 5% 6% 5% 4 5% 6% 25%	2185
March	1st to 10th	Night	12% 8% 3 9% 7% 9% 8% 6% 7% 7% 23%	5184
	11th to 20th	Night	17% 12% 3 9% 5% 5% 4 3 5% 5% 32%	5110
	21st to end	Night	19% 11% 4 11% 7% 6% 6% 4 6% 7% 18%	5549
April	1st to 10th	Night	19% 10% 3 9% 5% 5% 5% 3 5% 7% 28%	2100
	11th to 20th	Night	15% 9% 3 6% 6% 5% 4 3 5% 7% 36%	2059
	21st to end	Night	14% 7% 3 7% 5% 4 5% 5% 6% 7% 37%	1890
May	1st to 10th	Night	11% 5% 2 4 3 3 3 3 5% 7% 54%	5005
	11th to 20th	Night	10% 6% 2 6% 3 5% 4 3 5% 7% 48%	4700
	21st to end	Night	8% 4 2 5% 4 4 5% 4 7% 9% 48%	5181
June	1st to 10th	Night	14% 6% 3 6% 4 4 4 3 6% 5% 45%	1680
	11th to 20th	Night	10% 6% 2 4 4 3 4 3 6% 7% 51%	1680
	21st to end	Night	5% 5% 1 4 3 3 3 2 4 6% 64%	1680
July	1st to 10th	Night	1 1 1 1 1 1 1 3 4 84%	4740
	11th to 20th	Night	2 2 1 2 2 2 2 1 2 3 83%	4740
	21st to end	Night	2 2 1 2 2 1 1 2 3 4 79%	5267
August	1st to 10th	Night	2 2 1 3 2 2 3 2 4 4 76%	5275
	11th to 20th	Night	6% 3 1 3 2 3 3 2 4 6% 66%	5292
	21st to end	Night	5% 3 2 3 2 2 3 3 4 5% 68%	6218
September	1st to 10th	Night	5% 3 1 3 2 3 3 3 4 6% 68%	2100
	11th to 20th	Night	8% 4 2 5% 4 4 4 4 4 6% 56%	2132
	21st to end	Night	8% 4 2 5% 3 3 4 2 5% 7% 57%	2365
October	1st to 10th	Night	9% 4 2 5% 3 3 3 3 5% 7% 55%	3920
	11th to 20th	Night	12% 6% 2 6% 5% 6% 5% 5% 6% 9% 39%	3897
	21st to end	Night	18% 9% 3 9% 5% 5% 5% 4 6% 6% 31%	4266
November	1st to 10th	Night	21% 8% 3 9% 6% 5% 5% 5% 6% 6% 26%	2790
	11th to 20th	Night	25% 10% 4 10% 6% 5% 5% 4 5% 5% 21%	2940
	21st to end	Night	19% 8% 3 11% 7% 6% 5% 3 5% 5% 28%	2940
December	1st to 10th	Night	15% 8% 3 8% 5% 5% 4 3 5% 8% 35%	4700
	11th to 20th	Night	28% 14% 6% 12% 6% 6% 4 3 4 4 13%	5316
	21st to end	Night	25% 12% 5% 13% 7% 6% 5% 4 5% 4 14%	7106

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% 6% 3	4723
	11th to 20th	Day	43% 12% 10% 15% 14% 6%	4754
	21st to end	Day	55% 8% 6% 13% 15% 3	5843
February	1st to 10th	Day	68% 9% 9% 10% 4	1890
	11th to 20th	Day	67% 9% 9% 10% 4 2	1854
	21st to end	Day	67% 7% 8% 10% 6% 1	1620
March	1st to 10th	Day	58% 10% 15% 13% 4	4927
	11th to 20th	Day	59% 7% 7% 18% 8%	5110
	21st to end	Day	66% 11% 12% 8% 3	5667
April	1st to 10th	Day	63% 8% 12% 13% 3	2520
	11th to 20th	Day	56% 8% 11% 14% 9% 2	2507
	21st to end	Day	53% 10% 12% 15% 8% 1	2730
May	1st to 10th	Day	34% 7% 13% 32% 14%	7927
	11th to 20th	Day	36% 10% 20% 25% 9% 1	8163
	21st to end	Day	35% 11% 25% 23% 5%	8994
June	1st to 10th	Day	47% 8% 16% 20% 7% 1	2940
	11th to 20th	Day	44% 10% 18% 20% 8% 1	2940
	21st to end	Day	29% 8% 18% 29% 13% 4	2940
July	1st to 10th	Day	12% 4 14% 35% 18% 17%	8151
	11th to 20th	Day	12% 3 6% 20% 43% 16%	8145
	21st to end	Day	12% 4 17% 37% 26% 4	8613
August	1st to 10th	Day	11% 4 8% 29% 30% 18%	5976
	11th to 20th	Day	21% 7% 18% 37% 14% 3	5962
	21st to end	Day	21% 7% 17% 33% 18% 4	6283
September	1st to 10th	Day	21% 5% 14% 29% 20% 10%	2520
	11th to 20th	Day	34% 8% 14% 22% 16% 5%	2483
	21st to end	Day	36% 6% 15% 23% 15% 5%	2211
October	1st to 10th	Day	34% 8% 8% 24% 24% 2	3280
	11th to 20th	Day	47% 10% 15% 16% 12% 1	3261
	21st to end	Day	52% 11% 9% 17% 10% 1	3543
November	1st to 10th	Day	65% 8% 10% 12% 4	1723
	11th to 20th	Day	67% 9% 9% 9% 6% 1	1680
	21st to end	Day	62% 10% 7% 10% 10% 1	1680
December	1st to 10th	Day	52% 8% 10% 18% 12%	2700
	11th to 20th	Day	72% 9% 9% 8% 2	3108
	21st to end	Day	79% 8% 7% 4 2	4092
January	1st to 10th	Night	72% 9% 8% 7% 3	8172
	11th to 20th	Night	44% 8% 9% 18% 15% 6%	8203
	21st to end	Night	55% 5% 6% 13% 18% 3	8371
February	1st to 10th	Night	61% 10% 11% 12% 5%	2730
	11th to 20th	Night	57% 10% 12% 13% 7% 2	2664
	21st to end	Night	59% 8% 12% 12% 7% 1	2185
March	1st to 10th	Night	55% 9% 13% 16% 6%	5184
	11th to 20th	Night	53% 9% 10% 19% 8% 1	5110
	21st to end	Night	62% 11% 14% 12% 2	5549
April	1st to 10th	Night	55% 9% 16% 15% 6%	2100
	11th to 20th	Night	47% 8% 16% 17% 8% 3	2059
	21st to end	Night	46% 9% 14% 22% 7% 2	1890
May	1st to 10th	Night	29% 6% 12% 39% 13% 1	5003
	11th to 20th	Night	34% 7% 19% 30% 9% 1	4700
	21st to end	Night	29% 10% 32% 26% 4	5182
June	1st to 10th	Night	39% 8% 16% 29% 7% 1	1680
	11th to 20th	Night	31% 7% 21% 30% 10% 1	1680
	21st to end	Night	23% 5% 19% 36% 14% 4	1680
July	1st to 10th	Night	6% 2 16% 35% 24% 17%	4700
	11th to 20th	Night	10% 2 9% 18% 40% 20%	4692
	21st to end	Night	11% 3 18% 37% 27% 4	5153
August	1st to 10th	Night	7% 3 7% 30% 37% 16%	4169
	11th to 20th	Night	16% 6% 20% 42% 13% 4	4169
	21st to end	Night	16% 5% 18% 39% 18% 5%	4876
September	1st to 10th	Night	17% 6% 15% 30% 22% 10%	2100
	11th to 20th	Night	28% 7% 14% 26% 17% 7%	2132
	21st to end	Night	27% 7% 16% 25% 18% 7%	2365
October	1st to 10th	Night	26% 7% 9% 33% 22% 3	3920
	11th to 20th	Night	39% 8% 21% 20% 11% 2	3897
	21st to end	Night	50% 8% 12% 19% 9% 1	4266
November	1st to 10th	Night	57% 10% 10% 16% 6%	2790
	11th to 20th	Night	63% 8% 10% 11% 7% 2	2940
	21st to end	Night	56% 9% 11% 11% 12% 2	2940
December	1st to 10th	Night	44% 9% 10% 22% 15%	4700
	11th to 20th	Night	72% 9% 7% 9% 3	5316
	21st to end	Night	67% 12% 11% 8% 2	7106

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% 18% 10% 3	220
	11th to 20th	Day	23% 13% 16% 31% 13% 5%	221
	21st to end	Day	22% 11% 20% 26% 16% 5%	473
February	1st to 10th	Day	24% 16% 20% 21% 15% 4	430
	11th to 20th	Day	27% 12% 28% 20% 12% 3	425
	21st to end	Day	22% 22% 21% 20% 12% 2	388
March	1st to 10th	Day	20% 14% 28% 25% 10% 2	540
	11th to 20th	Day	25% 11% 24% 21% 15% 3	540
	21st to end	Day	23% 16% 24% 23% 13% 2	594
April	1st to 10th	Day	22% 16% 21% 20% 16% 5%	540
	11th to 20th	Day	21% 13% 26% 22% 14% 5%	532
	21st to end	Day	16% 13% 27% 23% 16% 5%	540
May	1st to 10th	Day	13% 13% 22% 26% 20% 6%	543
	11th to 20th	Day	17% 13% 21% 24% 16% 8%	568
	21st to end	Day	10% 10% 21% 25% 23% 10%	617
June	1st to 10th	Day	14% 10% 20% 25% 22% 8%	570
	11th to 20th	Day	12% 8% 26% 33% 18% 3	570
	21st to end	Day	5% 8% 18% 31% 31% 8%	570
July	1st to 10th	Day	3 4 16% 35% 30% 12%	566
	11th to 20th	Day	2 3 20% 34% 30% 11%	564
	21st to end	Day	2 3 14% 32% 36% 14%	619
August	1st to 10th	Day	3 2 12% 32% 34% 18%	567
	11th to 20th	Day	2 3 10% 29% 35% 20%	557
	21st to end	Day	5% 5% 15% 32% 30% 14%	627
September	1st to 10th	Day	6% 3 17% 28% 32% 13%	570
	11th to 20th	Day	9% 7% 16% 27% 29% 12%	570
	21st to end	Day	11% 6% 22% 29% 25% 6%	563
October	1st to 10th	Day	13% 9% 21% 25% 23% 9%	530
	11th to 20th	Day	14% 13% 17% 25% 23% 8%	530
	21st to end	Day	19% 13% 24% 26% 12% 6%	580
November	1st to 10th	Day	21% 14% 24% 25% 13% 3	261
	11th to 20th	Day	21% 15% 24% 19% 15% 5%	220
	21st to end	Day	23% 11% 20% 23% 16% 7%	220
December	1st to 10th	Day	25% 13% 15% 25% 15% 6%	220
	11th to 20th	Day	28% 12% 22% 27% 9% 2	220
	21st to end	Day	27% 14% 25% 20% 12% 2	242
January	1st to 10th	Night	29% 9% 22% 25% 12% 3	840
	11th to 20th	Night	24% 9% 18% 28% 19% 3	840
	21st to end	Night	22% 6% 17% 35% 18% 3	924
February	1st to 10th	Night	19% 7% 24% 31% 17% 2	840
	11th to 20th	Night	22% 9% 22% 31% 16% 1	824
	21st to end	Night	23% 11% 22% 33% 12%	692
March	1st to 10th	Night	18% 10% 23% 35% 14% 1	840
	11th to 20th	Night	22% 7% 21% 34% 15% 1	840
	21st to end	Night	22% 9% 23% 28% 15% 1	924
April	1st to 10th	Night	21% 8% 20% 32% 18% 1	840
	11th to 20th	Night	17% 8% 25% 34% 15% 1	811
	21st to end	Night	14% 5% 18% 42% 20% 1	630
May	1st to 10th	Night	11% 3 24% 42% 18% 2	520
	11th to 20th	Night	12% 6% 19% 43% 20%	414
	21st to end	Night	11% 3 21% 40% 24% 1	455
June	1st to 10th	Night	14% 4 19% 43% 20%	420
	11th to 20th	Night	10% 1 25% 45% 17% 1	420
	21st to end	Night	8% 1 15% 53% 22%	420
July	1st to 10th	Night	3 1 12% 57% 26% 1	410
	11th to 20th	Night	3 1 20% 52% 23%	408
	21st to end	Night	1 1 13% 52% 32% 2	498
August	1st to 10th	Night	3 1 8% 46% 37% 4	627
	11th to 20th	Night	4 8% 41% 44% 3	624
	21st to end	Night	5% 1 15% 46% 32% 2	821
September	1st to 10th	Night	5% 3 15% 41% 35% 1	840
	11th to 20th	Night	7% 3 14% 38% 32% 6%	840
	21st to end	Night	9% 4 13% 41% 29% 3	832
October	1st to 10th	Night	11% 3 18% 39% 26% 3	800
	11th to 20th	Night	15% 4 16% 36% 25% 4	800
	21st to end	Night	19% 7% 23% 31% 17% 4	880
November	1st to 10th	Night	22% 7% 19% 36% 16% 1	820
	11th to 20th	Night	26% 10% 20% 28% 14% 2	840
	21st to end	Night	20% 6% 20% 33% 18% 2	840
December	1st to 10th	Night	22% 7% 18% 33% 17% 3	840
	11th to 20th	Night	27% 8% 25% 26% 13% 1	840
	21st to end	Night	28% 10% 24% 26% 12% 1	924

Page generated at 2026-09-26 01:18:43. Version ac07

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