McMinnville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the McMinnville 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% 36%	118413
	Night	17% 9% 3 8% 5% 4 4 3 5% 6% 36%	119620
Transparency	Day	46% 9% 12% 16% 12% 4	118157
	Night	47% 10% 12% 17% 11% 3	119465
Seeing	Day	17% 11% 20% 26% 20% 6%	15460
	Night	19% 8% 19% 33% 20% 2	24343

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	32% 15% 6% 12% 6% 6% 4 3 4 4 10%	3639
	11th to 20th	Day	25% 9% 3 10% 5% 5% 5% 4 5% 5% 22%	3640
	21st to end	Day	23% 10% 4 9% 5% 5% 5% 3 4 5% 28%	4464
February	1st to 10th	Day	23% 14% 5% 10% 6% 6% 6% 4 5% 6% 15%	1800
	11th to 20th	Day	23% 12% 5% 12% 7% 5% 5% 3 4 6% 18%	1755
	21st to end	Day	22% 14% 4 11% 6% 6% 5% 4 4 5% 18%	1546
March	1st to 10th	Day	15% 12% 4 9% 6% 7% 7% 5% 8% 8% 19%	4798
	11th to 20th	Day	21% 13% 5% 9% 6% 5% 4 3 4 5% 25%	5000
	21st to end	Day	19% 12% 5% 12% 8% 7% 7% 4 6% 7% 13%	5563
April	1st to 10th	Day	21% 12% 4 10% 7% 6% 5% 4 5% 6% 19%	2400
	11th to 20th	Day	18% 12% 3 8% 6% 5% 5% 4 5% 5% 28%	2383
	21st to end	Day	17% 9% 3 8% 7% 6% 6% 5% 6% 8% 26%	2600
May	1st to 10th	Day	16% 8% 3 7% 5% 5% 5% 4 6% 6% 35%	4445
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 4 5% 7% 50%	4517
	21st to end	Day	15% 7% 2 7% 6% 7% 7% 6% 7% 7% 28%	4886
June	1st to 10th	Day	16% 8% 4 9% 6% 4 5% 4 5% 6% 33%	2660
	11th to 20th	Day	13% 9% 3 8% 6% 6% 6% 6% 8% 7% 30%	2660
	21st to end	Day	5% 5% 2 6% 5% 4 5% 4 5% 7% 52%	2806
July	1st to 10th	Day	3 3 1 3 2 3 3 3 4 4 72%	4430
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 5% 75%	4420
	21st to end	Day	5% 2 1 2 2 2 2 2 4 5% 74%	4764
August	1st to 10th	Day	1 3 1 4 3 3 3 3 5% 6% 68%	4091
	11th to 20th	Day	5% 4 2 5% 4 4 5% 4 7% 8% 52%	4026
	21st to end	Day	6% 6% 2 4 3 3 4 3 5% 8% 56%	4320
September	1st to 10th	Day	5% 3 1 4 3 3 4 3 5% 8% 62%	2280
	11th to 20th	Day	8% 7% 3 7% 5% 4 4 4 7% 8% 44%	2256
	21st to end	Day	14% 5% 2 6% 5% 4 4 3 5% 6% 46%	2012
October	1st to 10th	Day	12% 6% 3 5% 4 4 4 4 6% 7% 47%	3180
	11th to 20th	Day	14% 6% 3 11% 7% 5% 7% 4 7% 8% 28%	3161
	21st to end	Day	19% 9% 4 9% 6% 6% 5% 4 7% 9% 22%	3420
November	1st to 10th	Day	22% 14% 4 11% 6% 6% 5% 5% 6% 6% 15%	1639
	11th to 20th	Day	27% 13% 4 9% 7% 6% 4 3 4 5% 18%	1600
	21st to end	Day	24% 11% 5% 11% 6% 5% 4 4 4 5% 22%	1600
December	1st to 10th	Day	18% 9% 4 8% 5% 5% 5% 4 6% 5% 31%	2620
	11th to 20th	Day	26% 13% 6% 11% 7% 6% 5% 4 5% 6% 11%	3028
	21st to end	Day	29% 15% 7% 14% 7% 5% 5% 4 4 3 6%	4004
January	1st to 10th	Night	30% 14% 5% 10% 6% 6% 5% 3 4 4 13%	6306
	11th to 20th	Night	24% 11% 4 8% 5% 4 4 3 6% 6% 26%	6320
	21st to end	Night	26% 10% 3 7% 4 3 4 2 3 5% 33%	6495
February	1st to 10th	Night	20% 13% 4 10% 7% 6% 5% 4 6% 7% 19%	2600
	11th to 20th	Night	22% 11% 3 9% 5% 4 6% 3 5% 5% 26%	2532
	21st to end	Night	21% 12% 4 10% 6% 5% 5% 4 5% 6% 23%	2082
March	1st to 10th	Night	15% 12% 4 11% 7% 6% 7% 5% 7% 6% 22%	5082
	11th to 20th	Night	18% 11% 4 10% 6% 5% 4 3 4 6% 29%	5000
	21st to end	Night	20% 12% 4 11% 7% 7% 6% 4 5% 7% 17%	5412
April	1st to 10th	Night	19% 12% 4 10% 5% 5% 4 4 5% 6% 25%	2000
	11th to 20th	Night	15% 9% 3 8% 5% 5% 4 4 5% 7% 35%	1960
	21st to end	Night	16% 8% 3 7% 5% 4 5% 5% 6% 8% 34%	1800
May	1st to 10th	Night	18% 7% 2 5% 4 4 3 3 4 6% 43%	2735
	11th to 20th	Night	8% 4 1 5% 4 3 3 3 4 7% 58%	2596
	21st to end	Night	7% 7% 2 7% 5% 5% 6% 5% 7% 8% 41%	2805
June	1st to 10th	Night	13% 6% 2 8% 5% 5% 6% 4 5% 7% 39%	1520
	11th to 20th	Night	9% 7% 3 7% 6% 3 5% 4 5% 7% 45%	1520
	21st to end	Night	5% 4 2 5% 3 4 4 3 4 6% 62%	1357
July	1st to 10th	Night	3 1 1 2 1 1 2 1 2 3 82%	2503
	11th to 20th	Night	3 3 1 2 2 2 2 1 3 4 78%	2540
	21st to end	Night	2 1 2 1 1 2 2 3 4 81%	2784
August	1st to 10th	Night	2 2 1 2 1 2 2 2 3 6% 78%	2848
	11th to 20th	Night	5% 4 1 4 4 4 3 3 4 7% 61%	2812
	21st to end	Night	7% 4 1 4 2 3 4 2 4 5% 63%	3353
September	1st to 10th	Night	5% 3 1 3 2 3 3 3 4 5% 69%	1900
	11th to 20th	Night	8% 5% 2 6% 4 4 4 3 6% 6% 52%	1921
	21st to end	Night	10% 5% 2 5% 3 4 4 3 5% 6% 54%	2166
October	1st to 10th	Night	8% 4 2 5% 3 3 4 3 5% 7% 55%	3800
	11th to 20th	Night	13% 6% 3 7% 5% 5% 5% 4 7% 9% 36%	3777
	21st to end	Night	19% 9% 4 8% 5% 5% 4 4 6% 6% 30%	4147
November	1st to 10th	Night	22% 12% 3 9% 5% 5% 5% 4 5% 6% 24%	2659
	11th to 20th	Night	29% 10% 4 8% 5% 4 5% 3 5% 5% 22%	2800
	21st to end	Night	21% 9% 3 9% 5% 5% 4 4 7% 6% 27%	2800
December	1st to 10th	Night	16% 8% 3 7% 4 4 4 4 8% 8% 34%	4560
	11th to 20th	Night	31% 14% 5% 11% 6% 5% 4 3 4 5% 12%	5176
	21st to end	Night	29% 13% 5% 12% 7% 5% 5% 3 5% 5% 12%	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	76% 9% 5% 6% 3	3639
	11th to 20th	Day	60% 10% 7% 15% 6% 1	3640
	21st to end	Day	57% 9% 6% 11% 14% 3	4464
February	1st to 10th	Day	67% 11% 10% 8% 4	1800
	11th to 20th	Day	68% 11% 7% 8% 4 2	1764
	21st to end	Day	66% 10% 9% 9% 6% 1	1546
March	1st to 10th	Day	55% 13% 16% 11% 4	4798
	11th to 20th	Day	59% 8% 8% 17% 7%	5000
	21st to end	Day	67% 12% 12% 7% 3	5563
April	1st to 10th	Day	64% 10% 12% 12% 3	2400
	11th to 20th	Day	55% 10% 11% 13% 9% 2	2386
	21st to end	Day	55% 11% 13% 12% 8% 1	2600
May	1st to 10th	Day	45% 11% 13% 18% 12%	4445
	11th to 20th	Day	29% 10% 22% 25% 13% 1	4520
	21st to end	Day	46% 19% 20% 13% 2	4887
June	1st to 10th	Day	50% 9% 16% 18% 6% 1	2660
	11th to 20th	Day	49% 12% 19% 14% 6%	2660
	21st to end	Day	30% 8% 19% 28% 11% 4	2806
July	1st to 10th	Day	16% 5% 10% 16% 23% 30%	4361
	11th to 20th	Day	14% 4 7% 19% 38% 18%	4345
	21st to end	Day	14% 4 13% 28% 36% 6%	4613
August	1st to 10th	Day	16% 6% 12% 29% 26% 11%	4076
	11th to 20th	Day	25% 9% 20% 28% 13% 4	4065
	21st to end	Day	26% 7% 14% 26% 21% 6%	4319
September	1st to 10th	Day	20% 8% 15% 27% 20% 11%	2280
	11th to 20th	Day	37% 10% 15% 18% 14% 6%	2256
	21st to end	Day	38% 9% 14% 20% 15% 5%	2012
October	1st to 10th	Day	34% 8% 8% 26% 21% 2	3180
	11th to 20th	Day	52% 9% 14% 12% 12% 1	3161
	21st to end	Day	55% 9% 10% 16% 10% 1	3420
November	1st to 10th	Day	67% 10% 10% 10% 3	1639
	11th to 20th	Day	68% 9% 9% 7% 6% 1	1600
	21st to end	Day	64% 10% 7% 9% 10% 1	1600
December	1st to 10th	Day	51% 9% 10% 18% 12%	2620
	11th to 20th	Day	72% 10% 10% 7% 1	3028
	21st to end	Day	79% 9% 6% 4 2	4004
January	1st to 10th	Night	72% 10% 7% 6% 4 1	6306
	11th to 20th	Night	56% 11% 7% 18% 7% 1	6320
	21st to end	Night	54% 8% 6% 12% 15% 4	6495
February	1st to 10th	Night	63% 11% 11% 11% 4	2600
	11th to 20th	Night	59% 10% 13% 10% 6% 2	2534
	21st to end	Night	60% 10% 12% 10% 6% 2	2082
March	1st to 10th	Night	54% 12% 14% 14% 5%	5082
	11th to 20th	Night	53% 11% 10% 19% 6% 1	5000
	21st to end	Night	62% 13% 14% 10% 1	5412
April	1st to 10th	Night	58% 10% 14% 13% 5%	2000
	11th to 20th	Night	47% 10% 17% 15% 9% 3	1960
	21st to end	Night	47% 11% 16% 17% 7% 2	1800
May	1st to 10th	Night	39% 10% 16% 25% 10% 1	2735
	11th to 20th	Night	27% 6% 18% 33% 14% 2	2596
	21st to end	Night	34% 19% 30% 13% 4	2805
June	1st to 10th	Night	43% 9% 17% 23% 7% 1	1520
	11th to 20th	Night	37% 11% 20% 25% 7%	1520
	21st to end	Night	25% 7% 20% 32% 12% 4	1357
July	1st to 10th	Night	10% 4 9% 20% 26% 31%	2463
	11th to 20th	Night	12% 4 7% 19% 33% 24%	2492
	21st to end	Night	9% 3 13% 28% 38% 8%	2697
August	1st to 10th	Night	10% 4 9% 36% 32% 8%	2839
	11th to 20th	Night	23% 7% 22% 31% 12% 5%	2839
	21st to end	Night	23% 6% 16% 27% 23% 6%	3353
September	1st to 10th	Night	17% 7% 14% 29% 21% 11%	1900
	11th to 20th	Night	32% 8% 16% 22% 13% 8%	1921
	21st to end	Night	30% 8% 16% 22% 18% 7%	2166
October	1st to 10th	Night	28% 8% 9% 33% 20% 2	3800
	11th to 20th	Night	43% 9% 18% 17% 11% 2	3777
	21st to end	Night	52% 9% 10% 17% 10% 2	4147
November	1st to 10th	Night	59% 10% 11% 13% 6%	2659
	11th to 20th	Night	64% 9% 9% 9% 7% 2	2800
	21st to end	Night	56% 11% 11% 9% 11% 2	2800
December	1st to 10th	Night	43% 12% 9% 20% 15%	4560
	11th to 20th	Night	74% 9% 8% 7% 2	5176
	21st to end	Night	69% 14% 10% 6% 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	39% 17% 19% 16% 9% 2	200
	11th to 20th	Day	33% 13% 16% 21% 12% 6%	200
	21st to end	Day	26% 12% 19% 20% 18% 5%	420
February	1st to 10th	Day	27% 16% 22% 16% 15% 3	400
	11th to 20th	Day	29% 14% 27% 17% 11% 2	395
	21st to end	Day	27% 21% 20% 20% 11% 1	362
March	1st to 10th	Day	25% 17% 24% 23% 9% 2	500
	11th to 20th	Day	24% 17% 20% 21% 14% 3	500
	21st to end	Day	25% 18% 24% 22% 10% 1	550
April	1st to 10th	Day	25% 17% 23% 19% 12% 4	500
	11th to 20th	Day	24% 15% 23% 23% 10% 5%	492
	21st to end	Day	19% 14% 24% 24% 14% 4	500
May	1st to 10th	Day	14% 16% 23% 26% 17% 5%	503
	11th to 20th	Day	20% 12% 18% 28% 16% 6%	528
	21st to end	Day	13% 9% 20% 28% 21% 9%	550
June	1st to 10th	Day	16% 11% 20% 27% 20% 6%	490
	11th to 20th	Day	13% 13% 25% 28% 17% 4	490
	21st to end	Day	5% 9% 21% 35% 25% 6%	636
July	1st to 10th	Day	5% 4 16% 37% 29% 9%	496
	11th to 20th	Day	3 5% 17% 35% 29% 11%	484
	21st to end	Day	2 3 13% 33% 38% 11%	531
August	1st to 10th	Day	3 2 12% 33% 36% 15%	487
	11th to 20th	Day	3 3 9% 32% 34% 18%	477
	21st to end	Day	5% 4 18% 34% 29% 10%	539
September	1st to 10th	Day	6% 3 22% 27% 32% 10%	490
	11th to 20th	Day	10% 7% 18% 27% 30% 8%	490
	21st to end	Day	13% 8% 23% 31% 19% 7%	490
October	1st to 10th	Day	16% 9% 20% 25% 22% 8%	490
	11th to 20th	Day	18% 10% 17% 27% 19% 9%	490
	21st to end	Day	23% 14% 27% 19% 11% 6%	523
November	1st to 10th	Day	25% 18% 21% 20% 12% 4	237
	11th to 20th	Day	29% 15% 21% 16% 15% 6%	200
	21st to end	Day	26% 14% 19% 17% 20% 6%	200
December	1st to 10th	Day	31% 10% 15% 22% 16% 8%	200
	11th to 20th	Day	32% 15% 23% 20% 9% 2	200
	21st to end	Day	34% 18% 19% 16% 11% 1	220
January	1st to 10th	Night	35% 13% 17% 21% 13% 2	800
	11th to 20th	Night	30% 11% 17% 23% 17% 2	800
	21st to end	Night	27% 7% 16% 30% 17% 3	880
February	1st to 10th	Night	23% 11% 20% 29% 15% 2	800
	11th to 20th	Night	25% 11% 21% 27% 16% 1	784
	21st to end	Night	25% 14% 20% 30% 10%	660
March	1st to 10th	Night	23% 11% 23% 29% 14% 1	800
	11th to 20th	Night	22% 10% 21% 32% 15% 1	800
	21st to end	Night	25% 10% 24% 27% 13% 1	880
April	1st to 10th	Night	23% 10% 21% 28% 17% 1	800
	11th to 20th	Night	17% 11% 24% 33% 13% 1	772
	21st to end	Night	19% 8% 21% 35% 17% 1	600
May	1st to 10th	Night	12% 7% 23% 39% 18% 1	476
	11th to 20th	Night	14% 5% 21% 38% 22% 1	394
	21st to end	Night	12% 6% 22% 38% 22% 1	422
June	1st to 10th	Night	14% 5% 20% 39% 22%	380
	11th to 20th	Night	11% 4 25% 42% 17% 1	380
	21st to end	Night	6% 2 20% 49% 22%	380
July	1st to 10th	Night	3 1 14% 53% 29% 1	370
	11th to 20th	Night	5% 2 18% 50% 25% 1	368
	21st to end	Night	2 1 11% 51% 33% 1	427
August	1st to 10th	Night	3 1 9% 42% 40% 5%	567
	11th to 20th	Night	5% 1 9% 38% 45% 3	564
	21st to end	Night	7% 3 15% 43% 31% 2	743
September	1st to 10th	Night	5% 2 17% 39% 34% 2	760
	11th to 20th	Night	8% 4 15% 36% 33% 5%	760
	21st to end	Night	10% 5% 14% 40% 26% 3	760
October	1st to 10th	Night	14% 3 21% 33% 25% 4	760
	11th to 20th	Night	16% 6% 15% 34% 25% 4	760
	21st to end	Night	23% 7% 22% 27% 17% 4	836
November	1st to 10th	Night	24% 9% 19% 32% 15%	780
	11th to 20th	Night	30% 11% 21% 24% 13% 1	800
	21st to end	Night	24% 7% 20% 28% 18% 3	800
December	1st to 10th	Night	25% 8% 18% 29% 18% 2	800
	11th to 20th	Night	33% 10% 21% 24% 12% 1	800
	21st to end	Night	32% 14% 21% 23% 9% 1	880

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