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 2025-08-05.

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	13% 8% 3 7% 5% 5% 5% 4 6% 8% 37%	125413
	Night	13% 8% 3 7% 4 4 4 4 5% 7% 40%	122682
Transparency	Day	42% 8% 12% 20% 15% 3	129125
	Night	40% 7% 11% 20% 17% 4	127014
Seeing	Day	17% 13% 23% 22% 16% 8%	15580
	Night	16% 10% 23% 28% 19% 3	25580

By Month

Percentage Cloud Cover SE (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	15% 15% 7% 12% 4 4 3 3 4 4 29%	4056
	11th to 20th	Day	15% 12% 7% 10% 3 3 3 2 3 5% 37%	4060
	21st to end	Day	20% 10% 5% 6% 4 3 3 3 4 6% 35%	4765
February	1st to 10th	Day	19% 12% 4 8% 5% 4 3 3 4 4 34%	2000
	11th to 20th	Day	20% 12% 5% 8% 5% 3 4 3 5% 4 31%	1948
	21st to end	Day	18% 11% 4 6% 5% 4 4 3 5% 5% 35%	1650
March	1st to 10th	Day	17% 10% 4 7% 4 5% 4 3 5% 6% 35%	4480
	11th to 20th	Day	12% 8% 3 6% 5% 4 4 3 4 5% 46%	4887
	21st to end	Day	14% 8% 2 6% 4 5% 4 4 5% 7% 41%	5548
April	1st to 10th	Day	12% 7% 2 6% 5% 5% 4 4 6% 7% 42%	2400
	11th to 20th	Day	13% 9% 2 6% 4 4 4 4 5% 6% 44%	2374
	21st to end	Day	13% 7% 4 6% 5% 4 4 4 6% 7% 39%	2497
May	1st to 10th	Day	17% 9% 2 6% 5% 5% 5% 5% 7% 9% 29%	5862
	11th to 20th	Day	15% 10% 3 10% 6% 6% 6% 5% 6% 6% 28%	5861
	21st to end	Day	14% 9% 3 8% 5% 5% 5% 4 5% 7% 36%	6433
June	1st to 10th	Day	9% 6% 3 7% 5% 5% 6% 5% 6% 9% 39%	2600
	11th to 20th	Day	5% 4 2 7% 6% 6% 6% 5% 8% 10% 43%	2600
	21st to end	Day	5% 5% 2 6% 6% 5% 6% 6% 9% 12% 37%	2600
July	1st to 10th	Day	6% 5% 2 7% 6% 6% 7% 6% 9% 11% 36%	5900
	11th to 20th	Day	8% 5% 2 8% 6% 6% 7% 6% 9% 12% 31%	5900
	21st to end	Day	11% 9% 4 9% 7% 6% 7% 6% 8% 10% 23%	6424
August	1st to 10th	Day	6% 4 2 5% 5% 6% 5% 5% 8% 11% 43%	4078
	11th to 20th	Day	7% 5% 2 7% 6% 6% 6% 5% 8% 11% 38%	3729
	21st to end	Day	7% 4 1 7% 6% 5% 5% 5% 6% 8% 45%	4180
September	1st to 10th	Day	12% 6% 2 8% 6% 4 5% 4 6% 8% 38%	2196
	11th to 20th	Day	13% 7% 2 8% 5% 4 5% 4 5% 7% 40%	2090
	21st to end	Day	12% 5% 2 6% 4 5% 5% 4 4 8% 45%	2090
October	1st to 10th	Day	10% 5% 2 4 4 3 4 4 4 6% 54%	2090
	11th to 20th	Day	13% 5% 1 4 3 3 3 2 5% 7% 53%	2051
	21st to end	Day	15% 6% 2 4 5% 3 3 4 5% 7% 47%	1933
November	1st to 10th	Day	11% 6% 2 4 3 4 3 3 5% 6% 53%	1762
	11th to 20th	Day	12% 8% 3 5% 4 3 3 4 4 7% 47%	1800
	21st to end	Day	14% 8% 3 6% 4 4 3 4 5% 7% 43%	1800
December	1st to 10th	Day	13% 8% 3 7% 5% 5% 4 4 4 5% 41%	2930
	11th to 20th	Day	15% 13% 5% 11% 5% 5% 5% 3 5% 4 29%	3373
	21st to end	Day	14% 12% 6% 9% 5% 4 5% 4 5% 8% 28%	4466
January	1st to 10th	Night	15% 14% 5% 10% 4 3 3 2 4 5% 35%	5889
	11th to 20th	Night	18% 12% 4 7% 4 4 2 2 3 4 41%	5900
	21st to end	Night	17% 12% 4 7% 4 4 3 3 4 5% 39%	6189
February	1st to 10th	Night	19% 10% 4 8% 4 4 4 3 5% 6% 34%	2400
	11th to 20th	Night	23% 10% 3 8% 6% 4 3 3 4 5% 33%	2338
	21st to end	Night	21% 11% 3 6% 4 3 4 4 5% 6% 33%	1980
March	1st to 10th	Night	19% 12% 3 6% 5% 4 4 3 4 6% 33%	5373
	11th to 20th	Night	13% 6% 2 5% 3 4 4 4 6% 7% 48%	5072
	21st to end	Night	13% 8% 3 9% 5% 5% 4 3 5% 6% 40%	5422
April	1st to 10th	Night	12% 6% 2 5% 5% 4 5% 4 5% 8% 45%	2000
	11th to 20th	Night	15% 6% 2 5% 3 3 3 3 5% 7% 50%	1975
	21st to end	Night	13% 5% 2 6% 4 4 4 4 6% 8% 43%	1900
May	1st to 10th	Night	12% 10% 3 9% 5% 6% 5% 4 6% 8% 32%	4033
	11th to 20th	Night	14% 9% 4 9% 6% 5% 5% 4 6% 7% 30%	4032
	21st to end	Night	13% 7% 3 7% 5% 5% 5% 4 6% 9% 36%	4421
June	1st to 10th	Night	6% 7% 3 7% 5% 4 5% 5% 6% 9% 43%	1800
	11th to 20th	Night	4 4 2 4 4 4 4 4 7% 12% 51%	1800
	21st to end	Night	5% 5% 2 6% 4 5% 5% 5% 8% 10% 46%	1800
July	1st to 10th	Night	8% 5% 2 6% 4 5% 5% 5% 8% 11% 39%	4058
	11th to 20th	Night	7% 5% 2 6% 5% 5% 6% 5% 9% 13% 37%	4057
	21st to end	Night	8% 8% 3 9% 6% 6% 6% 6% 8% 12% 29%	4427
August	1st to 10th	Night	5% 4 1 5% 4 5% 5% 4 7% 11% 49%	2921
	11th to 20th	Night	6% 5% 2 5% 4 5% 5% 5% 7% 10% 46%	3100
	21st to end	Night	5% 4 2 4 4 4 5% 3 6% 9% 55%	3476
September	1st to 10th	Night	10% 6% 2 7% 3 5% 5% 4 6% 7% 46%	1963
	11th to 20th	Night	10% 6% 2 6% 5% 4 4 4 5% 8% 45%	2090
	21st to end	Night	9% 5% 2 6% 3 4 3 3 6% 6% 51%	2090
October	1st to 10th	Night	10% 4 2 5% 3 2 4 2 4 6% 59%	2090
	11th to 20th	Night	15% 5% 2 5% 3 4 3 2 4 5% 52%	2128
	21st to end	Night	14% 7% 2 5% 3 3 3 3 4 6% 50%	2660
November	1st to 10th	Night	12% 7% 2 5% 3 3 3 3 4 5% 52%	2536
	11th to 20th	Night	13% 8% 2 6% 4 3 3 3 5% 6% 48%	2600
	21st to end	Night	15% 9% 3 6% 3 4 4 4 5% 6% 43%	2600
December	1st to 10th	Night	16% 12% 3 8% 4 4 4 3 4 4 38%	4250
	11th to 20th	Night	19% 12% 4 8% 5% 4 3 3 4 5% 35%	4822
	21st to end	Night	12% 13% 5% 9% 5% 5% 5% 4 5% 7% 30%	6490

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	55% 7% 9% 15% 13% 2	4057
	11th to 20th	Day	50% 5% 4 16% 24% 1	4060
	21st to end	Day	49% 5% 8% 22% 12% 5%	4765
February	1st to 10th	Day	55% 4 8% 16% 16% 2	2000
	11th to 20th	Day	56% 4 7% 16% 14% 3	1958
	21st to end	Day	50% 5% 8% 14% 17% 5%	1650
March	1st to 10th	Day	49% 7% 7% 12% 17% 8%	4480
	11th to 20th	Day	39% 5% 8% 18% 21% 9%	4887
	21st to end	Day	42% 6% 10% 26% 15% 1	5550
April	1st to 10th	Day	39% 8% 12% 22% 17% 3	2400
	11th to 20th	Day	40% 6% 8% 18% 23% 4	2374
	21st to end	Day	43% 7% 11% 25% 13% 1	2497
May	1st to 10th	Day	47% 11% 13% 20% 8% 1	5897
	11th to 20th	Day	52% 11% 13% 17% 7%	5865
	21st to end	Day	45% 10% 9% 20% 14% 2	6447
June	1st to 10th	Day	39% 11% 14% 21% 13% 1	2600
	11th to 20th	Day	33% 11% 19% 21% 15% 2	2600
	21st to end	Day	34% 14% 18% 18% 13% 3	2600
July	1st to 10th	Day	35% 12% 20% 22% 10% 1	5835
	11th to 20th	Day	39% 14% 23% 20% 4 1	5831
	21st to end	Day	49% 13% 18% 16% 4	6240
August	1st to 10th	Day	29% 12% 17% 29% 12% 1	4065
	11th to 20th	Day	35% 10% 17% 24% 13% 1	3765
	21st to end	Day	32% 11% 12% 27% 16% 1	4179
September	1st to 10th	Day	41% 11% 12% 16% 15% 5%	2196
	11th to 20th	Day	41% 9% 11% 19% 17% 2	2090
	21st to end	Day	38% 7% 12% 21% 18% 5%	2090
October	1st to 10th	Day	23% 6% 7% 17% 35% 11%	3480
	11th to 20th	Day	22% 4 7% 23% 29% 15%	3382
	21st to end	Day	26% 5% 10% 23% 26% 10%	3157
November	1st to 10th	Day	31% 6% 9% 21% 27% 6%	1762
	11th to 20th	Day	39% 4 6% 22% 23% 6%	1800
	21st to end	Day	41% 6% 7% 21% 21% 4	1800
December	1st to 10th	Day	43% 6% 6% 21% 22% 2	2930
	11th to 20th	Day	57% 6% 7% 16% 12% 2	3370
	21st to end	Day	51% 6% 12% 19% 10% 2	4466
January	1st to 10th	Night	50% 5% 9% 17% 16% 1	5889
	11th to 20th	Night	49% 4 6% 14% 21% 6%	5900
	21st to end	Night	49% 4 5% 17% 19% 6%	6189
February	1st to 10th	Night	51% 5% 10% 17% 16% 2	2400
	11th to 20th	Night	56% 4 6% 15% 14% 4	2339
	21st to end	Night	52% 4 8% 16% 15% 4	1980
March	1st to 10th	Night	52% 6% 7% 13% 18% 5%	5373
	11th to 20th	Night	34% 6% 7% 19% 20% 13%	5072
	21st to end	Night	44% 6% 9% 24% 15% 2	5422
April	1st to 10th	Night	36% 8% 11% 22% 20% 3	2000
	11th to 20th	Night	35% 5% 9% 22% 22% 6%	1975
	21st to end	Night	37% 8% 12% 26% 15% 1	1900
May	1st to 10th	Night	47% 10% 14% 19% 9% 1	4060
	11th to 20th	Night	51% 11% 13% 16% 9%	4033
	21st to end	Night	40% 12% 14% 22% 12% 1	4429
June	1st to 10th	Night	37% 9% 15% 24% 13% 2	1800
	11th to 20th	Night	23% 9% 20% 30% 15% 2	1800
	21st to end	Night	30% 10% 17% 26% 13% 4	1800
July	1st to 10th	Night	33% 12% 19% 22% 12% 2	4015
	11th to 20th	Night	33% 12% 25% 23% 5% 2	4006
	21st to end	Night	43% 12% 22% 17% 5% 1	4297
August	1st to 10th	Night	25% 10% 14% 34% 16% 1	2910
	11th to 20th	Night	29% 11% 23% 23% 13% 1	3130
	21st to end	Night	23% 10% 13% 32% 20% 1	3476
September	1st to 10th	Night	34% 10% 14% 20% 17% 5%	1963
	11th to 20th	Night	36% 8% 12% 20% 21% 2	2090
	21st to end	Night	32% 7% 12% 23% 22% 5%	2090
October	1st to 10th	Night	22% 6% 8% 22% 30% 14%	3480
	11th to 20th	Night	22% 4 5% 22% 28% 17%	3523
	21st to end	Night	24% 4 7% 25% 29% 11%	4373
November	1st to 10th	Night	34% 5% 8% 21% 24% 7%	2536
	11th to 20th	Night	36% 5% 8% 19% 25% 8%	2600
	21st to end	Night	43% 4 6% 21% 20% 5%	2600
December	1st to 10th	Night	49% 5% 7% 14% 23% 2	4250
	11th to 20th	Night	50% 6% 6% 18% 17% 2	4824
	21st to end	Night	50% 8% 12% 20% 9% 1	6490

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	26% 27% 30% 12% 5%	300
	11th to 20th	Day	31% 30% 25% 11% 3 1	300
	21st to end	Day	22% 31% 36% 9% 3	330
February	1st to 10th	Day	25% 30% 30% 13% 3	300
	11th to 20th	Day	37% 28% 27% 6% 2 1	300
	21st to end	Day	32% 29% 30% 8% 1	249
March	1st to 10th	Day	28% 22% 33% 12% 4	300
	11th to 20th	Day	25% 25% 29% 16% 5% 1	459
	21st to end	Day	25% 19% 34% 15% 6% 1	550
April	1st to 10th	Day	20% 22% 26% 21% 10%	500
	11th to 20th	Day	18% 20% 30% 22% 9% 2	492
	21st to end	Day	18% 17% 29% 24% 11% 2	500
May	1st to 10th	Day	17% 17% 30% 22% 10% 4	503
	11th to 20th	Day	15% 10% 27% 25% 15% 8%	527
	21st to end	Day	14% 8% 22% 27% 17% 12%	573
June	1st to 10th	Day	12% 7% 20% 27% 22% 13%	530
	11th to 20th	Day	5% 4 17% 31% 25% 17%	530
	21st to end	Day	6% 4 19% 27% 25% 18%	530
July	1st to 10th	Day	10% 2 13% 30% 25% 20%	525
	11th to 20th	Day	9% 5% 10% 23% 29% 24%	524
	21st to end	Day	11% 3 11% 25% 29% 22%	576
August	1st to 10th	Day	10% 6% 13% 26% 27% 17%	502
	11th to 20th	Day	9% 4 15% 29% 31% 11%	479
	21st to end	Day	12% 3 9% 23% 32% 20%	539
September	1st to 10th	Day	10% 6% 11% 27% 31% 16%	490
	11th to 20th	Day	14% 5% 14% 25% 28% 14%	490
	21st to end	Day	16% 5% 17% 27% 28% 8%	490
October	1st to 10th	Day	13% 7% 18% 31% 22% 9%	490
	11th to 20th	Day	13% 11% 29% 28% 15% 4	490
	21st to end	Day	20% 11% 29% 26% 11% 3	382
November	1st to 10th	Day	17% 10% 35% 27% 9% 3	300
	11th to 20th	Day	16% 18% 37% 23% 5%	300
	21st to end	Day	20% 18% 32% 19% 8% 2	300
December	1st to 10th	Day	27% 22% 30% 16% 5% 1	300
	11th to 20th	Day	25% 23% 27% 18% 7%	300
	21st to end	Day	23% 25% 32% 15% 4 1	330
January	1st to 10th	Night	23% 20% 31% 23% 4	800
	11th to 20th	Night	26% 21% 30% 19% 4	800
	21st to end	Night	20% 19% 37% 21% 3	880
February	1st to 10th	Night	24% 16% 33% 24% 3	800
	11th to 20th	Night	30% 18% 30% 20% 2	783
	21st to end	Night	28% 20% 30% 21% 1	660
March	1st to 10th	Night	24% 16% 31% 26% 4	800
	11th to 20th	Night	21% 16% 32% 24% 6% 1	800
	21st to end	Night	20% 14% 31% 25% 8%	860
April	1st to 10th	Night	16% 15% 29% 29% 11%	600
	11th to 20th	Night	17% 11% 31% 29% 10% 2	593
	21st to end	Night	15% 9% 30% 34% 11% 1	600
May	1st to 10th	Night	13% 9% 30% 29% 19% 1	600
	11th to 20th	Night	15% 5% 23% 34% 19% 4	591
	21st to end	Night	9% 4 16% 36% 30% 5%	650
June	1st to 10th	Night	7% 5% 15% 37% 32% 5%	600
	11th to 20th	Night	4 2 14% 35% 36% 9%	600
	21st to end	Night	5% 2 12% 35% 37% 8%	600
July	1st to 10th	Night	10% 3 6% 27% 44% 10%	585
	11th to 20th	Night	8% 2 8% 26% 43% 12%	582
	21st to end	Night	8% 2 7% 30% 41% 11%	657
August	1st to 10th	Night	7% 3 5% 29% 47% 9%	579
	11th to 20th	Night	7% 2 9% 36% 40% 6%	564
	21st to end	Night	9% 2 7% 27% 46% 9%	627
September	1st to 10th	Night	12% 3 9% 30% 39% 8%	633
	11th to 20th	Night	12% 3 14% 30% 35% 6%	760
	21st to end	Night	11% 2 16% 34% 33% 4	760
October	1st to 10th	Night	11% 6% 16% 32% 28% 7%	760
	11th to 20th	Night	17% 8% 23% 31% 19% 2	760
	21st to end	Night	17% 10% 24% 33% 15% 3	836
November	1st to 10th	Night	17% 8% 21% 34% 17% 2	780
	11th to 20th	Night	15% 15% 29% 29% 11% 1	800
	21st to end	Night	20% 14% 27% 30% 9% 1	800
December	1st to 10th	Night	26% 14% 28% 26% 6%	800
	11th to 20th	Night	23% 14% 29% 27% 7% 1	800
	21st to end	Night	24% 18% 28% 25% 5%	880

Page generated at 2025-08-02 00:32:23. Version ac07

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