Roseburg Airport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Roseburg Airport clear sky chart from 2005-11-06 to 2025-07-06.

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	15% 8% 3 7% 4 4 4 3 5% 6% 41%	124199
	Night	17% 10% 3 7% 4 4 4 3 5% 6% 38%	123434
Transparency	Day	42% 6% 12% 20% 14% 6%	123950
	Night	46% 6% 13% 19% 12% 4	123270
Seeing	Day	18% 12% 24% 26% 15% 5%	15677
	Night	20% 7% 14% 31% 24% 3	24692

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	28% 16% 5% 10% 6% 4 5% 3 5% 5% 13%	3639
	11th to 20th	Day	25% 10% 3 8% 5% 4 4 3 4 6% 26%	3842
	21st to end	Day	18% 10% 3 6% 4 4 4 3 5% 8% 35%	4510
February	1st to 10th	Day	23% 11% 3 8% 5% 5% 6% 6% 7% 7% 18%	1800
	11th to 20th	Day	23% 13% 4 10% 6% 4 5% 4 6% 5% 20%	1755
	21st to end	Day	24% 15% 5% 9% 6% 4 4 3 5% 6% 19%	1568
March	1st to 10th	Day	16% 11% 5% 11% 5% 6% 5% 4 6% 7% 22%	4868
	11th to 20th	Day	21% 13% 4 8% 4 5% 4 3 5% 6% 26%	5000
	21st to end	Day	23% 12% 4 9% 6% 5% 5% 4 6% 7% 18%	5519
April	1st to 10th	Day	21% 14% 4 9% 7% 5% 5% 3 5% 5% 20%	2400
	11th to 20th	Day	19% 13% 4 10% 4 4 4 4 5% 5% 28%	2369
	21st to end	Day	20% 9% 4 7% 5% 4 4 4 5% 7% 30%	2570
May	1st to 10th	Day	13% 6% 2 6% 4 5% 5% 4 6% 6% 43%	5964
	11th to 20th	Day	12% 8% 3 8% 5% 4 4 4 5% 6% 42%	6277
	21st to end	Day	11% 6% 2 6% 4 4 4 4 5% 8% 46%	6902
June	1st to 10th	Day	17% 9% 3 7% 4 4 4 3 4 7% 39%	2800
	11th to 20th	Day	14% 7% 2 6% 4 4 4 3 6% 7% 43%	2800
	21st to end	Day	7% 5% 1 4 3 3 4 2 5% 6% 60%	2800
July	1st to 10th	Day	3 2 1 2 1 1 1 2 2 3 81%	4491
	11th to 20th	Day	4 3 1 2 2 2 2 2 3 3 76%	4420
	21st to end	Day	3 4 1 2 2 2 2 2 3 4 75%	4582
August	1st to 10th	Day	3 4 1 4 2 2 3 2 3 5% 70%	4091
	11th to 20th	Day	3 5% 1 4 2 3 3 3 4 6% 65%	4026
	21st to end	Day	5% 5% 2 3 3 2 2 2 3 6% 67%	4282
September	1st to 10th	Day	5% 3 1 3 2 2 3 2 4 6% 68%	2280
	11th to 20th	Day	9% 6% 2 5% 2 3 4 3 5% 7% 53%	2237
	21st to end	Day	10% 5% 2 5% 3 4 4 3 5% 7% 52%	2024
October	1st to 10th	Day	8% 6% 2 6% 4 3 3 2 4 6% 56%	3180
	11th to 20th	Day	12% 7% 3 8% 5% 5% 5% 4 6% 8% 36%	3161
	21st to end	Day	17% 10% 4 10% 4 5% 5% 5% 6% 8% 27%	3448
November	1st to 10th	Day	25% 10% 3 9% 5% 6% 4 4 6% 7% 21%	1742
	11th to 20th	Day	26% 11% 4 9% 7% 5% 5% 4 6% 6% 18%	1600
	21st to end	Day	23% 10% 4 8% 5% 5% 3 4 5% 8% 25%	1600
December	1st to 10th	Day	15% 6% 3 6% 5% 4 5% 5% 6% 9% 37%	2620
	11th to 20th	Day	27% 14% 4 9% 6% 5% 5% 3 6% 7% 14%	3028
	21st to end	Day	29% 17% 5% 11% 6% 5% 5% 3 5% 4 8%	4004
January	1st to 10th	Night	32% 14% 4 10% 5% 4 4 4 5% 5% 11%	6306
	11th to 20th	Night	23% 12% 3 9% 5% 4 5% 3 5% 8% 24%	6123
	21st to end	Night	22% 11% 4 7% 4 4 3 2 3 4 36%	6468
February	1st to 10th	Night	22% 14% 4 9% 6% 5% 5% 3 6% 6% 21%	2600
	11th to 20th	Night	23% 15% 4 7% 5% 4 3 3 5% 7% 25%	2532
	21st to end	Night	21% 14% 3 8% 5% 4 4 3 6% 6% 25%	2060
March	1st to 10th	Night	19% 14% 5% 10% 5% 4 5% 4 6% 7% 21%	5011
	11th to 20th	Night	17% 14% 4 10% 5% 5% 4 3 5% 7% 25%	5000
	21st to end	Night	23% 14% 4 10% 6% 5% 5% 4 5% 6% 19%	5456
April	1st to 10th	Night	23% 13% 4 8% 5% 5% 4 4 5% 6% 24%	2000
	11th to 20th	Night	19% 12% 3 7% 6% 4 4 3 4 6% 32%	1979
	21st to end	Night	19% 9% 4 6% 5% 5% 4 5% 6% 7% 32%	1825
May	1st to 10th	Night	17% 8% 2 5% 4 3 3 4 4 5% 43%	4009
	11th to 20th	Night	12% 10% 3 9% 5% 4 4 3 4 5% 43%	3616
	21st to end	Night	12% 5% 2 5% 3 3 3 2 4 6% 53%	3972
June	1st to 10th	Night	15% 6% 2 5% 4 4 4 4 5% 7% 44%	1600
	11th to 20th	Night	10% 6% 3 5% 4 3 4 2 4 6% 54%	1600
	21st to end	Night	8% 3 1 2 2 2 3 2 3 5% 70%	1600
July	1st to 10th	Night	2 1 1 1 1 1 2 1 2 3 84%	2580
	11th to 20th	Night	2 2 1 2 2 2 2 1 2 3 82%	2540
	21st to end	Night	4 2 1 2 1 2 1 1 2 3 80%	2973
August	1st to 10th	Night	2 2 1 3 2 2 2 2 4 4 76%	2848
	11th to 20th	Night	3 3 1 3 3 4 3 2 4 6% 69%	2812
	21st to end	Night	5% 3 1 3 2 2 2 2 3 4 73%	3392
September	1st to 10th	Night	5% 2 1 2 1 2 2 2 4 5% 75%	1900
	11th to 20th	Night	7% 4 2 4 4 4 3 3 4 7% 59%	1938
	21st to end	Night	11% 5% 2 5% 3 3 3 2 5% 7% 55%	2156
October	1st to 10th	Night	7% 6% 2 5% 3 3 2 2 4 5% 61%	3800
	11th to 20th	Night	10% 7% 3 8% 4 4 4 3 6% 8% 43%	3777
	21st to end	Night	18% 11% 5% 10% 6% 5% 4 3 4 6% 28%	4121
November	1st to 10th	Night	23% 9% 3 7% 5% 4 5% 3 6% 8% 26%	2552
	11th to 20th	Night	27% 11% 3 10% 5% 4 5% 3 5% 6% 20%	2800
	21st to end	Night	22% 10% 4 7% 5% 4 4 4 6% 7% 28%	2800
December	1st to 10th	Night	14% 8% 2 7% 4 5% 4 4 7% 8% 37%	4560
	11th to 20th	Night	27% 14% 5% 10% 5% 4 4 3 5% 7% 14%	5176
	21st to end	Night	26% 13% 4 10% 6% 5% 5% 4 7% 6% 13%	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	72% 6% 9% 9% 3 1	3639
	11th to 20th	Day	55% 7% 7% 21% 7% 3	3842
	21st to end	Day	47% 6% 9% 15% 15% 8%	4510
February	1st to 10th	Day	60% 8% 14% 12% 5% 1	1800
	11th to 20th	Day	62% 8% 12% 12% 5% 2	1764
	21st to end	Day	65% 7% 9% 11% 7% 1	1568
March	1st to 10th	Day	56% 7% 13% 20% 4	4868
	11th to 20th	Day	57% 7% 9% 18% 8%	5000
	21st to end	Day	61% 9% 16% 12% 2	5519
April	1st to 10th	Day	65% 7% 12% 12% 4	2400
	11th to 20th	Day	58% 7% 12% 14% 8% 2	2372
	21st to end	Day	52% 7% 16% 16% 8% 1	2570
May	1st to 10th	Day	38% 7% 13% 24% 18%	5964
	11th to 20th	Day	41% 7% 15% 24% 12% 1	6280
	21st to end	Day	34% 9% 26% 27% 4	6904
June	1st to 10th	Day	47% 5% 16% 24% 7%	2800
	11th to 20th	Day	40% 7% 15% 27% 10% 1	2800
	21st to end	Day	25% 5% 16% 34% 17% 3	2800
July	1st to 10th	Day	11% 2 8% 17% 23% 38%	4422
	11th to 20th	Day	14% 3 5% 17% 30% 30%	4345
	21st to end	Day	14% 3 7% 23% 42% 12%	4437
August	1st to 10th	Day	18% 4 8% 25% 35% 10%	4076
	11th to 20th	Day	19% 4 12% 34% 24% 6%	4065
	21st to end	Day	20% 3 12% 28% 29% 7%	4281
September	1st to 10th	Day	19% 3 7% 27% 29% 14%	2280
	11th to 20th	Day	30% 5% 14% 27% 18% 7%	2237
	21st to end	Day	31% 4 14% 26% 18% 7%	2024
October	1st to 10th	Day	30% 5% 9% 20% 20% 17%	3180
	11th to 20th	Day	41% 8% 18% 21% 10% 2	3161
	21st to end	Day	51% 7% 11% 17% 12% 2	3448
November	1st to 10th	Day	60% 7% 11% 15% 7% 1	1742
	11th to 20th	Day	64% 7% 10% 10% 7% 3	1600
	21st to end	Day	56% 6% 10% 11% 13% 3	1600
December	1st to 10th	Day	42% 7% 8% 20% 19% 4	2620
	11th to 20th	Day	66% 7% 13% 11% 3	3028
	21st to end	Day	74% 7% 9% 7% 2 1	4004
January	1st to 10th	Night	72% 6% 8% 10% 3 1	6306
	11th to 20th	Night	54% 7% 10% 20% 6% 2	6123
	21st to end	Night	53% 4 6% 15% 14% 9%	6468
February	1st to 10th	Night	61% 7% 12% 13% 6% 1	2600
	11th to 20th	Night	60% 6% 12% 15% 6% 1	2534
	21st to end	Night	59% 7% 13% 14% 5% 2	2060
March	1st to 10th	Night	59% 7% 15% 14% 4	5011
	11th to 20th	Night	56% 9% 11% 17% 4 3	5000
	21st to end	Night	63% 8% 17% 10% 2	5456
April	1st to 10th	Night	61% 7% 15% 13% 4	2000
	11th to 20th	Night	54% 7% 16% 16% 5% 3	1979
	21st to end	Night	52% 8% 18% 16% 5% 1	1825
May	1st to 10th	Night	41% 6% 13% 28% 12%	4006
	11th to 20th	Night	43% 6% 15% 28% 7% 1	3616
	21st to end	Night	33% 7% 33% 25% 3	3972
June	1st to 10th	Night	39% 8% 16% 31% 5%	1600
	11th to 20th	Night	34% 5% 20% 33% 8% 1	1600
	21st to end	Night	19% 4 20% 38% 18% 2	1600
July	1st to 10th	Night	9% 2 8% 20% 27% 34%	2540
	11th to 20th	Night	10% 2 5% 22% 37% 25%	2492
	21st to end	Night	12% 2 8% 29% 40% 9%	2880
August	1st to 10th	Night	13% 3 9% 31% 37% 8%	2839
	11th to 20th	Night	17% 5% 16% 35% 23% 4	2839
	21st to end	Night	17% 4 12% 30% 31% 6%	3392
September	1st to 10th	Night	14% 3 8% 33% 29% 13%	1900
	11th to 20th	Night	25% 6% 14% 31% 18% 6%	1938
	21st to end	Night	30% 5% 13% 27% 18% 8%	2156
October	1st to 10th	Night	26% 4 10% 21% 29% 9%	3800
	11th to 20th	Night	38% 6% 23% 22% 10% 2	3777
	21st to end	Night	55% 7% 11% 16% 9% 2	4121
November	1st to 10th	Night	54% 7% 14% 13% 10% 1	2552
	11th to 20th	Night	63% 7% 10% 10% 7% 3	2800
	21st to end	Night	54% 6% 10% 14% 12% 4	2800
December	1st to 10th	Night	40% 6% 11% 22% 19% 2	4560
	11th to 20th	Night	68% 6% 12% 10% 4	5176
	21st to end	Night	65% 9% 14% 9% 2 1	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	34% 17% 22% 17% 10% 2	200
	11th to 20th	Day	30% 13% 15% 23% 10% 9%	285
	21st to end	Day	23% 13% 22% 18% 18% 5%	440
February	1st to 10th	Day	25% 13% 21% 23% 15% 2	400
	11th to 20th	Day	31% 16% 22% 20% 9% 2	395
	21st to end	Day	30% 18% 19% 24% 8% 1	374
March	1st to 10th	Day	28% 17% 23% 23% 9% 1	500
	11th to 20th	Day	26% 15% 22% 21% 14% 2	500
	21st to end	Day	29% 17% 24% 21% 9% 2	550
April	1st to 10th	Day	23% 19% 24% 21% 11% 1	500
	11th to 20th	Day	25% 18% 25% 20% 9% 3	492
	21st to end	Day	24% 18% 25% 21% 9% 4	500
May	1st to 10th	Day	19% 15% 28% 22% 12% 4	503
	11th to 20th	Day	23% 16% 25% 21% 10% 4	528
	21st to end	Day	20% 13% 24% 26% 12% 5%	573
June	1st to 10th	Day	15% 16% 24% 25% 14% 6%	530
	11th to 20th	Day	12% 20% 32% 24% 10% 2	530
	21st to end	Day	5% 8% 31% 35% 16% 5%	530
July	1st to 10th	Day	4 7% 30% 36% 17% 6%	507
	11th to 20th	Day	3 7% 30% 39% 14% 7%	484
	21st to end	Day	3 3 29% 37% 21% 6%	531
August	1st to 10th	Day	4 3 26% 40% 19% 8%	487
	11th to 20th	Day	3 6% 20% 37% 24% 10%	477
	21st to end	Day	5% 7% 26% 32% 22% 9%	539
September	1st to 10th	Day	6% 7% 24% 31% 23% 9%	490
	11th to 20th	Day	10% 10% 24% 33% 18% 5%	490
	21st to end	Day	12% 8% 27% 26% 20% 7%	490
October	1st to 10th	Day	15% 11% 19% 27% 22% 7%	490
	11th to 20th	Day	16% 10% 18% 27% 23% 7%	490
	21st to end	Day	22% 12% 22% 22% 17% 5%	539
November	1st to 10th	Day	21% 15% 20% 24% 16% 4	313
	11th to 20th	Day	24% 13% 21% 24% 14% 6%	200
	21st to end	Day	24% 13% 15% 25% 23% 2	200
December	1st to 10th	Day	24% 10% 17% 24% 17% 9%	200
	11th to 20th	Day	34% 15% 16% 22% 11% 3	200
	21st to end	Day	34% 14% 16% 20% 13% 2	220
January	1st to 10th	Night	33% 11% 18% 22% 14% 3	800
	11th to 20th	Night	26% 12% 13% 26% 18% 5%	800
	21st to end	Night	25% 6% 14% 29% 21% 4	880
February	1st to 10th	Night	25% 10% 16% 29% 20% 2	800
	11th to 20th	Night	28% 9% 15% 29% 17% 1	784
	21st to end	Night	26% 10% 16% 33% 15%	660
March	1st to 10th	Night	28% 11% 16% 29% 15% 1	800
	11th to 20th	Night	22% 12% 15% 32% 18% 1	800
	21st to end	Night	29% 12% 16% 28% 14% 1	880
April	1st to 10th	Night	25% 13% 19% 26% 16% 2	800
	11th to 20th	Night	21% 11% 20% 28% 18% 2	791
	21st to end	Night	21% 8% 16% 32% 21% 2	625
May	1st to 10th	Night	21% 6% 16% 31% 24% 2	561
	11th to 20th	Night	13% 7% 14% 34% 30% 2	394
	21st to end	Night	16% 6% 16% 31% 28% 3	433
June	1st to 10th	Night	16% 6% 13% 35% 29% 2	400
	11th to 20th	Night	8% 6% 23% 39% 22% 3	400
	21st to end	Night	9% 2 10% 42% 37% 1	400
July	1st to 10th	Night	5% 2 8% 41% 42% 2	380
	11th to 20th	Night	2 1 13% 49% 34%	368
	21st to end	Night	3 2 6% 42% 42% 4	540
August	1st to 10th	Night	3 1 5% 37% 48% 6%	567
	11th to 20th	Night	3 1 6% 34% 50% 6%	564
	21st to end	Night	4 3 14% 37% 36% 6%	769
September	1st to 10th	Night	5% 2 15% 34% 41% 3	760
	11th to 20th	Night	8% 4 11% 35% 34% 8%	760
	21st to end	Night	12% 5% 13% 34% 32% 5%	760
October	1st to 10th	Night	11% 4 15% 36% 28% 7%	760
	11th to 20th	Night	14% 5% 12% 31% 32% 6%	760
	21st to end	Night	23% 7% 14% 30% 20% 6%	836
November	1st to 10th	Night	23% 8% 15% 31% 22% 2	780
	11th to 20th	Night	30% 9% 15% 28% 16% 2	800
	21st to end	Night	24% 10% 12% 31% 20% 4	800
December	1st to 10th	Night	24% 9% 12% 27% 22% 5%	800
	11th to 20th	Night	32% 10% 14% 27% 15% 3	800
	21st to end	Night	38% 11% 15% 24% 12% 1	880

Page generated at 2025-07-02 22:30:14. Version ac07

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