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 2024-04-03.

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 6% 6% 3 5% 5% 6% 7% 37%	79254
	Night	14% 8% 3 6% 5% 3 4 4 5% 7% 41%	80884
Transparency	Day	44% 8% 11% 19% 15% 3	78977
	Night	42% 7% 11% 20% 17% 4	80680
Seeing	Day	17% 13% 23% 22% 17% 9%	13765
	Night	17% 10% 23% 28% 19% 3	23908

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	14% 12% 6% 10% 6% 3 5% 5% 5% 5% 28%	2836
	11th to 20th	Day	19% 12% 6% 10% 5% 3 5% 3 4 4 30%	2840
	21st to end	Day	24% 12% 7% 5% 5% 2 3 4 4 5% 30%	3325
February	1st to 10th	Day	20% 11% 5% 7% 6% 3 4 3 4 4 34%	1900
	11th to 20th	Day	20% 11% 5% 7% 6% 3 4 4 5% 5% 32%	1848
	21st to end	Day	19% 10% 4 6% 6% 3 4 4 5% 5% 33%	1570
March	1st to 10th	Day	14% 10% 4 6% 5% 3 5% 4 5% 6% 38%	1900
	11th to 20th	Day	19% 9% 4 6% 6% 3 4 4 4 5% 35%	2051
	21st to end	Day	15% 10% 3 6% 5% 4 6% 5% 6% 6% 34%	2332
April	1st to 10th	Day	12% 6% 3 6% 5% 3 5% 5% 6% 7% 43%	2184
	11th to 20th	Day	14% 8% 2 5% 5% 4 4 4 5% 6% 44%	2134
	21st to end	Day	14% 7% 4 6% 5% 3 4 5% 5% 8% 39%	2247
May	1st to 10th	Day	14% 6% 3 5% 5% 3 5% 5% 6% 8% 41%	2340
	11th to 20th	Day	13% 7% 3 7% 7% 4 6% 6% 5% 6% 37%	2301
	21st to end	Day	9% 6% 3 6% 6% 5% 7% 6% 6% 9% 38%	2531
June	1st to 10th	Day	9% 5% 3 7% 6% 4 6% 6% 6% 9% 39%	2340
	11th to 20th	Day	5% 4 2 5% 6% 4 6% 6% 7% 10% 44%	2340
	21st to end	Day	6% 4 2 5% 7% 4 6% 8% 8% 12% 38%	2340
July	1st to 10th	Day	9% 6% 3 6% 8% 5% 7% 7% 8% 10% 30%	2340
	11th to 20th	Day	10% 5% 2 7% 7% 4 7% 7% 8% 10% 33%	2340
	21st to end	Day	9% 6% 3 6% 7% 4 8% 8% 8% 10% 31%	2547
August	1st to 10th	Day	8% 5% 3 6% 8% 5% 6% 7% 9% 11% 32%	2291
	11th to 20th	Day	9% 6% 3 6% 7% 6% 6% 7% 6% 10% 33%	2125
	21st to end	Day	12% 6% 2 7% 7% 5% 7% 7% 7% 9% 31%	2376
September	1st to 10th	Day	13% 6% 3 6% 6% 3 5% 6% 6% 8% 37%	2081
	11th to 20th	Day	13% 7% 3 6% 7% 3 5% 5% 5% 7% 41%	1980
	21st to end	Day	11% 4 2 5% 5% 4 4 5% 4 8% 47%	1980
October	1st to 10th	Day	10% 5% 2 3 5% 2 4 5% 4 6% 53%	1980
	11th to 20th	Day	14% 5% 1 3 3 2 4 3 5% 7% 52%	1944
	21st to end	Day	15% 6% 2 4 5% 2 4 5% 5% 7% 46%	1832
November	1st to 10th	Day	11% 5% 2 3 3 2 4 3 5% 6% 56%	1672
	11th to 20th	Day	12% 7% 3 5% 4 3 3 4 4 6% 48%	1710
	21st to end	Day	15% 7% 3 5% 4 3 4 4 5% 7% 44%	1710
December	1st to 10th	Day	19% 11% 4 7% 5% 4 5% 4 5% 6% 32%	1710
	11th to 20th	Day	15% 12% 3 8% 6% 3 6% 4 5% 4 35%	2153
	21st to end	Day	16% 12% 6% 7% 6% 3 5% 5% 5% 7% 29%	3124
January	1st to 10th	Night	18% 14% 5% 7% 5% 2 3 3 4 5% 35%	4109
	11th to 20th	Night	19% 11% 5% 7% 6% 4 3 3 3 4 34%	4120
	21st to end	Night	21% 14% 4 6% 4 3 3 3 3 4 34%	4329
February	1st to 10th	Night	19% 9% 4 8% 5% 3 4 4 4 6% 34%	2280
	11th to 20th	Night	23% 9% 4 6% 7% 3 3 3 4 5% 34%	2218
	21st to end	Night	22% 11% 3 5% 5% 3 4 4 5% 6% 32%	1884
March	1st to 10th	Night	17% 9% 4 4 5% 3 4 4 5% 7% 39%	2280
	11th to 20th	Night	17% 9% 3 6% 5% 3 4 5% 4 6% 37%	2128
	21st to end	Night	15% 8% 4 5% 5% 3 6% 5% 5% 6% 39%	2280
April	1st to 10th	Night	12% 5% 3 4 5% 3 5% 4 5% 8% 47%	1820
	11th to 20th	Night	15% 5% 2 4 3 2 3 3 4 7% 50%	1775
	21st to end	Night	14% 5% 3 5% 5% 2 5% 4 6% 8% 44%	1710
May	1st to 10th	Night	11% 6% 3 5% 5% 2 6% 5% 5% 7% 47%	1620
	11th to 20th	Night	12% 5% 2 6% 5% 3 5% 5% 6% 8% 43%	1592
	21st to end	Night	7% 4 2 6% 6% 4 6% 6% 6% 11% 42%	1744
June	1st to 10th	Night	5% 6% 3 6% 6% 3 5% 6% 6% 9% 44%	1620
	11th to 20th	Night	4 3 2 3 4 3 4 5% 8% 12% 53%	1620
	21st to end	Night	5% 5% 3 5% 5% 4 6% 5% 7% 10% 45%	1620
July	1st to 10th	Night	8% 5% 3 7% 5% 3 5% 7% 9% 12% 36%	1620
	11th to 20th	Night	7% 4 2 4 6% 3 6% 5% 7% 12% 43%	1620
	21st to end	Night	7% 5% 2 5% 5% 4 7% 7% 8% 12% 38%	1771
August	1st to 10th	Night	5% 4 2 5% 6% 4 6% 6% 8% 12% 42%	1643
	11th to 20th	Night	7% 6% 2 5% 5% 4 6% 6% 6% 9% 43%	1776
	21st to end	Night	9% 5% 3 5% 4 3 5% 5% 8% 11% 42%	1980
September	1st to 10th	Night	10% 6% 2 5% 4 3 5% 5% 6% 8% 46%	1859
	11th to 20th	Night	10% 6% 3 5% 6% 3 4 5% 5% 8% 45%	1980
	21st to end	Night	7% 5% 2 5% 4 3 4 4 6% 7% 53%	1980
October	1st to 10th	Night	10% 4 2 4 3 2 3 3 4 6% 58%	1980
	11th to 20th	Night	16% 5% 2 4 4 3 3 4 4 5% 50%	2016
	21st to end	Night	15% 7% 2 4 4 3 3 4 4 6% 49%	2520
November	1st to 10th	Night	12% 6% 2 5% 4 2 3 3 4 5% 54%	2406
	11th to 20th	Night	13% 7% 2 5% 4 2 4 3 5% 7% 48%	2470
	21st to end	Night	15% 8% 4 5% 4 2 4 5% 4 6% 43%	2470
December	1st to 10th	Night	19% 11% 4 6% 5% 4 5% 4 4 5% 32%	2470
	11th to 20th	Night	16% 10% 4 6% 5% 2 4 4 4 6% 39%	3042
	21st to end	Night	14% 14% 4 8% 7% 4 5% 6% 5% 7% 27%	4532

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	54% 8% 7% 15% 14% 2	2837
	11th to 20th	Day	56% 7% 5% 13% 18% 2	2840
	21st to end	Day	55% 5% 8% 20% 12% 1	3325
February	1st to 10th	Day	55% 3 7% 15% 17% 2	1900
	11th to 20th	Day	55% 4 6% 17% 14% 4	1858
	21st to end	Day	52% 5% 8% 13% 16% 5%	1570
March	1st to 10th	Day	46% 6% 8% 16% 18% 6%	1900
	11th to 20th	Day	51% 6% 11% 16% 14% 3	2051
	21st to end	Day	49% 7% 11% 20% 12% 1	2332
April	1st to 10th	Day	38% 8% 11% 22% 17% 3	2184
	11th to 20th	Day	41% 6% 8% 17% 24% 4	2134
	21st to end	Day	42% 7% 10% 25% 14% 1	2247
May	1st to 10th	Day	40% 8% 12% 25% 13% 3	2340
	11th to 20th	Day	46% 10% 12% 19% 12%	2305
	21st to end	Day	40% 11% 14% 20% 13% 1	2531
June	1st to 10th	Day	39% 11% 15% 21% 13% 1	2340
	11th to 20th	Day	32% 11% 19% 21% 15% 2	2340
	21st to end	Day	35% 13% 18% 18% 13% 3	2340
July	1st to 10th	Day	43% 12% 16% 17% 9% 3	2275
	11th to 20th	Day	43% 13% 17% 15% 10% 3	2271
	21st to end	Day	41% 14% 16% 20% 8% 1	2405
August	1st to 10th	Day	41% 14% 19% 17% 8% 1	2278
	11th to 20th	Day	44% 11% 14% 17% 12% 1	2125
	21st to end	Day	44% 14% 14% 16% 10% 2	2376
September	1st to 10th	Day	41% 12% 12% 17% 15% 4	2081
	11th to 20th	Day	42% 10% 11% 19% 17% 2	1980
	21st to end	Day	36% 7% 11% 22% 19% 5%	1980
October	1st to 10th	Day	32% 7% 8% 21% 25% 6%	1980
	11th to 20th	Day	31% 6% 10% 21% 23% 9%	1944
	21st to end	Day	36% 6% 8% 19% 24% 5%	1832
November	1st to 10th	Day	30% 5% 9% 21% 28% 6%	1672
	11th to 20th	Day	38% 5% 6% 22% 23% 7%	1710
	21st to end	Day	41% 6% 7% 21% 22% 4	1710
December	1st to 10th	Day	53% 5% 6% 19% 13% 3	1710
	11th to 20th	Day	51% 6% 8% 15% 17% 2	2150
	21st to end	Day	51% 6% 12% 18% 11% 2	3124
January	1st to 10th	Night	50% 7% 8% 17% 17% 2	4109
	11th to 20th	Night	54% 5% 7% 12% 16% 6%	4120
	21st to end	Night	55% 4 6% 14% 18% 2	4329
February	1st to 10th	Night	51% 5% 9% 16% 16% 2	2280
	11th to 20th	Night	55% 5% 6% 15% 14% 5%	2219
	21st to end	Night	54% 4 8% 15% 13% 5%	1884
March	1st to 10th	Night	46% 6% 9% 14% 18% 7%	2280
	11th to 20th	Night	48% 7% 8% 19% 15% 3	2128
	21st to end	Night	46% 7% 11% 23% 13% 2	2280
April	1st to 10th	Night	35% 8% 11% 23% 21% 3	1820
	11th to 20th	Night	35% 5% 9% 21% 22% 7%	1775
	21st to end	Night	37% 8% 12% 27% 15% 1	1710
May	1st to 10th	Night	37% 7% 11% 24% 19% 2	1620
	11th to 20th	Night	38% 11% 16% 21% 13% 1	1593
	21st to end	Night	34% 12% 15% 23% 13% 2	1745
June	1st to 10th	Night	36% 9% 15% 25% 13% 2	1620
	11th to 20th	Night	21% 9% 22% 31% 14% 2	1620
	21st to end	Night	31% 9% 17% 25% 13% 4	1620
July	1st to 10th	Night	35% 14% 18% 18% 12% 2	1575
	11th to 20th	Night	30% 11% 19% 23% 12% 4	1566
	21st to end	Night	34% 13% 18% 22% 11% 2	1672
August	1st to 10th	Night	32% 11% 19% 26% 11%	1632
	11th to 20th	Night	34% 12% 20% 17% 15% 2	1776
	21st to end	Night	33% 13% 16% 24% 12% 2	1980
September	1st to 10th	Night	34% 10% 15% 20% 17% 4	1859
	11th to 20th	Night	36% 8% 12% 20% 21% 2	1980
	21st to end	Night	30% 7% 11% 24% 23% 6%	1980
October	1st to 10th	Night	28% 6% 9% 24% 25% 9%	1980
	11th to 20th	Night	36% 6% 8% 21% 21% 8%	2016
	21st to end	Night	36% 4 7% 22% 24% 7%	2520
November	1st to 10th	Night	33% 5% 7% 22% 25% 8%	2406
	11th to 20th	Night	36% 5% 8% 19% 25% 8%	2470
	21st to end	Night	43% 4 6% 21% 21% 5%	2470
December	1st to 10th	Night	53% 5% 9% 17% 14% 3	2470
	11th to 20th	Night	45% 6% 7% 17% 20% 4	3044
	21st to end	Night	52% 9% 10% 16% 11% 1	4532

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	24% 27% 31% 13% 5%	270
	11th to 20th	Day	31% 30% 24% 11% 3 1	270
	21st to end	Day	22% 30% 37% 9% 3	297
February	1st to 10th	Day	27% 27% 30% 13% 3	270
	11th to 20th	Day	36% 26% 29% 6% 2 1	270
	21st to end	Day	34% 30% 28% 7% 1	225
March	1st to 10th	Day	27% 23% 34% 13% 3	270
	11th to 20th	Day	24% 25% 29% 16% 5% 1	421
	21st to end	Day	24% 19% 34% 16% 7% 1	506
April	1st to 10th	Day	18% 20% 26% 23% 12%	428
	11th to 20th	Day	18% 17% 30% 22% 10% 2	412
	21st to end	Day	18% 17% 27% 23% 12% 2	420
May	1st to 10th	Day	16% 15% 29% 25% 11% 5%	423
	11th to 20th	Day	13% 9% 26% 25% 17% 9%	447
	21st to end	Day	12% 6% 20% 28% 20% 15%	485
June	1st to 10th	Day	12% 5% 18% 27% 23% 15%	450
	11th to 20th	Day	6% 3 16% 28% 28% 20%	450
	21st to end	Day	7% 4 20% 28% 24% 18%	450
July	1st to 10th	Day	11% 2 12% 27% 25% 23%	445
	11th to 20th	Day	9% 5% 10% 21% 28% 26%	444
	21st to end	Day	9% 2 10% 26% 28% 24%	488
August	1st to 10th	Day	11% 5% 11% 26% 28% 19%	446
	11th to 20th	Day	10% 3 12% 30% 33% 12%	439
	21st to end	Day	14% 3 10% 22% 31% 20%	495
September	1st to 10th	Day	11% 4 10% 26% 33% 16%	450
	11th to 20th	Day	14% 4 13% 24% 29% 16%	450
	21st to end	Day	14% 4 17% 28% 30% 8%	450
October	1st to 10th	Day	13% 7% 18% 31% 22% 9%	450
	11th to 20th	Day	14% 12% 29% 27% 14% 4	450
	21st to end	Day	21% 12% 27% 25% 11% 3	347
November	1st to 10th	Day	16% 10% 33% 29% 10% 3	270
	11th to 20th	Day	14% 19% 39% 24% 4	270
	21st to end	Day	18% 19% 34% 19% 9% 2	270
December	1st to 10th	Day	29% 20% 29% 17% 5% 1	270
	11th to 20th	Day	24% 21% 28% 18% 8%	270
	21st to end	Day	23% 26% 32% 15% 3	297
January	1st to 10th	Night	23% 19% 31% 22% 4	760
	11th to 20th	Night	26% 22% 29% 19% 4	760
	21st to end	Night	20% 19% 37% 21% 3	836
February	1st to 10th	Night	23% 15% 33% 25% 3	760
	11th to 20th	Night	29% 17% 31% 21% 2	743
	21st to end	Night	29% 21% 30% 19% 1	628
March	1st to 10th	Night	23% 15% 32% 26% 4	760
	11th to 20th	Night	21% 16% 32% 24% 7% 1	760
	21st to end	Night	20% 14% 31% 26% 9%	817
April	1st to 10th	Night	15% 13% 29% 31% 12%	546
	11th to 20th	Night	18% 10% 31% 29% 11% 2	533
	21st to end	Night	15% 8% 28% 35% 12% 1	540
May	1st to 10th	Night	12% 9% 29% 30% 19% 1	540
	11th to 20th	Night	15% 5% 21% 34% 21% 4	531
	21st to end	Night	8% 3 14% 36% 34% 6%	584
June	1st to 10th	Night	7% 3 14% 36% 33% 5%	540
	11th to 20th	Night	3 2 13% 35% 37% 10%	540
	21st to end	Night	5% 2 12% 37% 35% 8%	540
July	1st to 10th	Night	11% 2 6% 26% 44% 11%	525
	11th to 20th	Night	8% 2 8% 27% 42% 13%	522
	21st to end	Night	8% 2 7% 31% 42% 11%	591
August	1st to 10th	Night	7% 2 4 30% 48% 10%	537
	11th to 20th	Night	7% 1 8% 35% 41% 6%	534
	21st to end	Night	10% 2 6% 27% 46% 9%	594
September	1st to 10th	Night	12% 2 9% 30% 40% 8%	599
	11th to 20th	Night	12% 3 13% 30% 36% 6%	720
	21st to end	Night	10% 2 16% 33% 33% 5%	720
October	1st to 10th	Night	12% 6% 17% 31% 27% 7%	720
	11th to 20th	Night	17% 8% 23% 30% 19% 2	720
	21st to end	Night	17% 10% 24% 32% 14% 3	792
November	1st to 10th	Night	16% 8% 20% 35% 18% 3	740
	11th to 20th	Night	15% 15% 29% 29% 11% 1	760
	21st to end	Night	20% 13% 27% 30% 9% 1	760
December	1st to 10th	Night	26% 14% 28% 26% 6%	760
	11th to 20th	Night	22% 14% 29% 28% 7% 1	760
	21st to end	Night	24% 18% 29% 25% 5%	836

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