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 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% 4 5% 4 5% 7% 41%	158898
	Night	15% 8% 3 7% 5% 4 4 3 5% 6% 40%	149842
Transparency	Day	42% 8% 13% 20% 13% 4	153669
	Night	44% 9% 13% 19% 12% 3	146071
Seeing	Day	16% 11% 20% 26% 20% 7%	17244
	Night	19% 8% 19% 33% 20% 2	25933

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	29% 15% 6% 12% 7% 7% 5% 3 4 3 8%	4722
	11th to 20th	Day	19% 7% 3 9% 5% 5% 5% 4 5% 5% 31%	4740
	21st to end	Day	20% 10% 4 10% 6% 5% 5% 3 5% 5% 27%	5783
February	1st to 10th	Day	23% 14% 5% 9% 6% 6% 6% 4 5% 7% 16%	1890
	11th to 20th	Day	23% 12% 5% 12% 7% 5% 5% 3 4 6% 18%	1845
	21st to end	Day	22% 14% 4 11% 6% 6% 5% 4 5% 5% 18%	1621
March	1st to 10th	Day	15% 12% 4 10% 6% 7% 7% 5% 7% 8% 19%	4904
	11th to 20th	Day	21% 13% 5% 9% 6% 5% 4 3 4 5% 25%	5110
	21st to end	Day	19% 11% 5% 12% 8% 7% 7% 4 6% 7% 14%	5685
April	1st to 10th	Day	20% 11% 4 10% 7% 6% 5% 4 6% 6% 20%	2520
	11th to 20th	Day	18% 11% 3 8% 6% 6% 5% 4 6% 6% 28%	2504
	21st to end	Day	16% 9% 3 9% 7% 6% 6% 5% 6% 7% 26%	2730
May	1st to 10th	Day	10% 6% 2 6% 4 4 4 4 6% 8% 46%	7980
	11th to 20th	Day	7% 6% 3 8% 6% 5% 6% 5% 7% 8% 39%	8160
	21st to end	Day	11% 6% 2 6% 5% 5% 6% 5% 6% 8% 40%	8992
June	1st to 10th	Day	15% 8% 3 9% 6% 4 5% 4 5% 6% 36%	2940
	11th to 20th	Day	12% 8% 3 8% 6% 6% 5% 5% 8% 7% 33%	2940
	21st to end	Day	6% 5% 2 6% 5% 4 5% 4 5% 7% 51%	3102
July	1st to 10th	Day	2 2 1 3 2 3 3 3 4 5% 72%	8243
	11th to 20th	Day	3 2 1 2 2 2 2 2 2 4 78%	8220
	21st to end	Day	3 2 1 2 2 2 3 3 4 6% 72%	8870
August	1st to 10th	Day	1 2 1 3 2 3 3 3 4 6% 70%	7547
	11th to 20th	Day	4 4 2 4 3 4 5% 4 7% 9% 56%	7563
	21st to end	Day	5% 5% 2 4 3 3 4 4 6% 9% 55%	8016
September	1st to 10th	Day	5% 3 1 5% 3 3 4 3 5% 8% 59%	2520
	11th to 20th	Day	8% 6% 2 7% 5% 4 4 4 7% 8% 45%	2494
	21st to end	Day	14% 5% 2 5% 5% 4 4 3 5% 7% 46%	2205
October	1st to 10th	Day	12% 6% 3 5% 4 4 4 4 6% 7% 46%	3280
	11th to 20th	Day	13% 6% 3 11% 7% 5% 7% 4 7% 8% 28%	3261
	21st to end	Day	19% 9% 4 9% 6% 6% 5% 4 7% 9% 22%	3529
November	1st to 10th	Day	22% 14% 4 11% 6% 5% 5% 5% 6% 6% 15%	1722
	11th to 20th	Day	26% 13% 4 9% 7% 7% 4 3 4 5% 18%	1680
	21st to end	Day	24% 10% 5% 11% 6% 5% 4 4 5% 5% 21%	1680
December	1st to 10th	Day	19% 9% 4 8% 5% 5% 5% 4 6% 5% 30%	2700
	11th to 20th	Day	26% 13% 6% 11% 7% 6% 5% 4 6% 6% 10%	3108
	21st to end	Day	29% 15% 7% 14% 7% 5% 5% 4 4 3 7%	4092
January	1st to 10th	Night	28% 14% 5% 12% 7% 6% 5% 3 4 4 12%	8172
	11th to 20th	Night	19% 8% 3 8% 5% 4 4 4 6% 5% 33%	8220
	21st to end	Night	23% 10% 4 8% 5% 4 4 3 4 5% 32%	8411
February	1st to 10th	Night	20% 13% 4 10% 7% 6% 5% 4 6% 6% 19%	2730
	11th to 20th	Night	22% 11% 3 9% 5% 4 6% 4 5% 5% 26%	2662
	21st to end	Night	21% 12% 4 10% 6% 5% 5% 4 5% 6% 23%	2183
March	1st to 10th	Night	15% 12% 4 11% 7% 6% 7% 5% 7% 6% 22%	5196
	11th to 20th	Night	18% 11% 4 10% 6% 5% 4 3 4 6% 28%	5110
	21st to end	Night	20% 12% 4 10% 7% 7% 6% 4 5% 7% 17%	5532
April	1st to 10th	Night	18% 12% 4 10% 5% 5% 4 4 5% 6% 27%	2100
	11th to 20th	Night	15% 9% 3 8% 5% 5% 5% 4 5% 7% 34%	2059
	21st to end	Night	16% 8% 2 7% 5% 4 5% 5% 5% 8% 34%	1890
May	1st to 10th	Night	12% 5% 2 4 3 4 3 3 5% 7% 52%	4946
	11th to 20th	Night	8% 6% 2 6% 4 4 5% 4 5% 8% 47%	4700
	21st to end	Night	6% 6% 2 6% 4 4 5% 4 7% 9% 47%	5181
June	1st to 10th	Night	12% 6% 2 7% 5% 5% 6% 4 5% 7% 42%	1680
	11th to 20th	Night	8% 7% 2 6% 5% 3 5% 4 5% 7% 48%	1680
	21st to end	Night	5% 4 1 5% 3 4 4 3 4 6% 61%	1499
July	1st to 10th	Night	2 1 1 1 1 1 2 2 4 6% 81%	4675
	11th to 20th	Night	2 2 2 1 2 2 1 3 4 81%	4740
	21st to end	Night	2 2 1 2 2 2 2 2 4 5% 76%	5204
August	1st to 10th	Night	2 2 1 3 2 2 3 2 4 5% 75%	5275
	11th to 20th	Night	7% 4 1 4 3 3 3 3 4 6% 61%	5292
	21st to end	Night	5% 3 1 4 3 3 4 3 5% 7% 64%	6218
September	1st to 10th	Night	5% 3 1 4 2 3 3 3 4 5% 66%	2100
	11th to 20th	Night	7% 5% 2 6% 4 4 4 3 5% 6% 53%	2123
	21st to end	Night	9% 4 2 5% 3 3 4 3 5% 7% 55%	2370
October	1st to 10th	Night	9% 4 2 5% 3 3 4 3 5% 7% 54%	3920
	11th to 20th	Night	13% 6% 3 7% 5% 5% 5% 4 7% 8% 36%	3897
	21st to end	Night	19% 9% 4 8% 5% 5% 4 4 6% 6% 30%	4280
November	1st to 10th	Night	23% 11% 3 9% 5% 5% 5% 3 5% 6% 23%	2795
	11th to 20th	Night	28% 11% 4 9% 5% 5% 5% 3 5% 5% 21%	2940
	21st to end	Night	22% 9% 3 10% 5% 5% 4 4 7% 6% 26%	2940
December	1st to 10th	Night	16% 8% 3 7% 4 4 4 4 8% 8% 33%	4700
	11th to 20th	Night	31% 14% 5% 11% 6% 5% 4 3 4 5% 12%	5316
	21st to end	Night	28% 13% 5% 12% 7% 6% 5% 3 5% 5% 12%	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	78% 9% 5% 6% 3	4723
	11th to 20th	Day	51% 9% 7% 13% 14% 5%	4740
	21st to end	Day	57% 8% 6% 12% 15% 2	5783
February	1st to 10th	Day	66% 11% 10% 8% 4	1890
	11th to 20th	Day	68% 11% 7% 9% 4 2	1854
	21st to end	Day	66% 10% 9% 9% 6% 1	1621
March	1st to 10th	Day	56% 13% 16% 11% 4	4904
	11th to 20th	Day	60% 8% 8% 17% 7%	5110
	21st to end	Day	66% 12% 12% 7% 3	5685
April	1st to 10th	Day	62% 10% 13% 13% 3	2520
	11th to 20th	Day	55% 10% 12% 13% 8% 2	2507
	21st to end	Day	55% 11% 12% 13% 8% 1	2730
May	1st to 10th	Day	35% 8% 13% 29% 15%	7980
	11th to 20th	Day	36% 11% 21% 23% 8%	8163
	21st to end	Day	37% 12% 24% 21% 5%	8994
June	1st to 10th	Day	48% 8% 16% 19% 8% 1	2940
	11th to 20th	Day	46% 11% 18% 17% 7% 1	2940
	21st to end	Day	31% 8% 18% 28% 12% 4	3102
July	1st to 10th	Day	14% 5% 15% 33% 16% 17%	8175
	11th to 20th	Day	13% 3 7% 20% 40% 17%	8145
	21st to end	Day	13% 4 17% 37% 26% 3	8671
August	1st to 10th	Day	13% 4 10% 29% 28% 16%	5976
	11th to 20th	Day	21% 8% 20% 35% 13% 3	5962
	21st to end	Day	23% 6% 17% 32% 16% 4	6283
September	1st to 10th	Day	23% 7% 15% 26% 19% 10%	2520
	11th to 20th	Day	36% 10% 14% 20% 14% 5%	2494
	21st to end	Day	37% 9% 13% 21% 15% 4	2205
October	1st to 10th	Day	35% 8% 8% 26% 21% 2	3280
	11th to 20th	Day	52% 9% 14% 13% 12% 1	3261
	21st to end	Day	55% 9% 10% 16% 9% 1	3529
November	1st to 10th	Day	67% 10% 10% 10% 3	1722
	11th to 20th	Day	69% 9% 9% 7% 6% 1	1680
	21st to end	Day	64% 10% 7% 9% 9% 1	1680
December	1st to 10th	Day	52% 9% 9% 18% 11%	2700
	11th to 20th	Day	72% 10% 10% 7% 1	3108
	21st to end	Day	78% 9% 6% 4 2	4092
January	1st to 10th	Night	73% 10% 8% 7% 3 1	8172
	11th to 20th	Night	48% 10% 8% 15% 14% 6%	8220
	21st to end	Night	55% 7% 6% 11% 18% 3	8411
February	1st to 10th	Night	63% 11% 11% 11% 4	2730
	11th to 20th	Night	59% 10% 12% 10% 6% 2	2664
	21st to end	Night	60% 10% 12% 11% 6% 2	2183
March	1st to 10th	Night	54% 12% 14% 14% 5%	5196
	11th to 20th	Night	54% 11% 10% 18% 6% 1	5110
	21st to end	Night	62% 13% 14% 10% 1	5532
April	1st to 10th	Night	57% 9% 15% 14% 5%	2100
	11th to 20th	Night	48% 9% 17% 15% 8% 3	2059
	21st to end	Night	46% 11% 16% 18% 8% 2	1890
May	1st to 10th	Night	30% 6% 13% 36% 13% 1	4944
	11th to 20th	Night	34% 8% 19% 30% 8% 1	4700
	21st to end	Night	30% 12% 29% 24% 5%	5182
June	1st to 10th	Night	41% 9% 17% 24% 8% 1	1680
	11th to 20th	Night	35% 10% 19% 27% 9% 1	1680
	21st to end	Night	25% 7% 19% 32% 12% 4	1499
July	1st to 10th	Night	8% 4 15% 34% 22% 17%	4635
	11th to 20th	Night	10% 3 9% 18% 44% 16%	4692
	21st to end	Night	12% 3 19% 37% 25% 4	5091
August	1st to 10th	Night	8% 3 7% 32% 36% 14%	4169
	11th to 20th	Night	21% 6% 21% 36% 13% 4	4169
	21st to end	Night	18% 6% 19% 35% 17% 4	4876
September	1st to 10th	Night	20% 7% 15% 28% 20% 10%	2100
	11th to 20th	Night	31% 8% 16% 23% 15% 8%	2123
	21st to end	Night	29% 7% 16% 23% 18% 6%	2370
October	1st to 10th	Night	28% 8% 10% 33% 20% 2	3920
	11th to 20th	Night	43% 9% 18% 17% 11% 2	3897
	21st to end	Night	52% 9% 10% 18% 9% 1	4280
November	1st to 10th	Night	60% 10% 11% 13% 6%	2795
	11th to 20th	Night	65% 9% 9% 9% 6% 1	2940
	21st to end	Night	57% 11% 10% 9% 11% 2	2940
December	1st to 10th	Night	44% 12% 10% 19% 15%	4700
	11th to 20th	Night	75% 8% 8% 7% 2	5316
	21st to end	Night	69% 14% 10% 6% 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	37% 16% 20% 16% 9% 2	220
	11th to 20th	Day	30% 11% 17% 24% 12% 6%	220
	21st to end	Day	24% 12% 20% 22% 17% 5%	452
February	1st to 10th	Day	27% 16% 22% 17% 16% 3	430
	11th to 20th	Day	29% 14% 27% 18% 11% 2	425
	21st to end	Day	27% 21% 20% 21% 10% 1	389
March	1st to 10th	Day	24% 17% 24% 24% 9% 2	540
	11th to 20th	Day	25% 16% 21% 21% 13% 3	540
	21st to end	Day	25% 17% 24% 23% 10% 1	594
April	1st to 10th	Day	23% 16% 22% 20% 12% 6%	540
	11th to 20th	Day	23% 15% 24% 22% 10% 5%	532
	21st to end	Day	19% 14% 25% 24% 14% 4	540
May	1st to 10th	Day	13% 15% 23% 27% 18% 5%	543
	11th to 20th	Day	20% 13% 18% 27% 17% 6%	568
	21st to end	Day	12% 8% 21% 28% 21% 10%	617
June	1st to 10th	Day	15% 11% 20% 26% 20% 8%	570
	11th to 20th	Day	12% 12% 24% 30% 18% 4	570
	21st to end	Day	6% 8% 22% 33% 25% 7%	732
July	1st to 10th	Day	5% 3 15% 35% 31% 11%	577
	11th to 20th	Day	4 5% 18% 35% 28% 11%	564
	21st to end	Day	2 3 13% 31% 37% 13%	619
August	1st to 10th	Day	3 3 12% 31% 35% 17%	567
	11th to 20th	Day	3 3 10% 30% 35% 20%	557
	21st to end	Day	5% 4 17% 33% 28% 12%	627
September	1st to 10th	Day	7% 4 19% 27% 32% 11%	570
	11th to 20th	Day	9% 8% 17% 27% 30% 9%	570
	21st to end	Day	12% 7% 22% 31% 21% 7%	563
October	1st to 10th	Day	16% 9% 20% 26% 21% 8%	530
	11th to 20th	Day	18% 12% 17% 26% 19% 8%	530
	21st to end	Day	24% 13% 27% 20% 10% 6%	566
November	1st to 10th	Day	25% 18% 21% 21% 11% 3	260
	11th to 20th	Day	27% 15% 20% 17% 15% 5%	220
	21st to end	Day	27% 13% 19% 18% 19% 5%	220
December	1st to 10th	Day	33% 10% 14% 22% 14% 7%	220
	11th to 20th	Day	33% 15% 22% 19% 10% 2	220
	21st to end	Day	33% 17% 20% 19% 10% 1	242
January	1st to 10th	Night	34% 13% 18% 22% 12% 2	840
	11th to 20th	Night	29% 11% 17% 25% 18% 2	840
	21st to end	Night	26% 8% 16% 31% 17% 2	924
February	1st to 10th	Night	23% 11% 20% 30% 15% 1	840
	11th to 20th	Night	24% 11% 21% 27% 16% 1	824
	21st to end	Night	26% 14% 20% 31% 10%	692
March	1st to 10th	Night	23% 11% 23% 29% 13% 1	840
	11th to 20th	Night	22% 10% 22% 31% 14% 1	840
	21st to end	Night	25% 10% 25% 27% 12% 1	924
April	1st to 10th	Night	22% 10% 21% 28% 18%	840
	11th to 20th	Night	18% 11% 24% 33% 13% 1	811
	21st to end	Night	19% 7% 21% 36% 16% 1	630
May	1st to 10th	Night	12% 6% 22% 40% 19% 1	500
	11th to 20th	Night	13% 5% 21% 38% 22% 1	414
	21st to end	Night	11% 5% 21% 39% 22% 1	455
June	1st to 10th	Night	13% 5% 21% 39% 22%	420
	11th to 20th	Night	10% 4 24% 45% 17% 1	420
	21st to end	Night	7% 2 18% 50% 23%	420
July	1st to 10th	Night	3 1 13% 52% 31% 1	410
	11th to 20th	Night	4 1 19% 50% 25%	408
	21st to end	Night	2 1 10% 50% 35% 1	473
August	1st to 10th	Night	3 1 9% 43% 39% 5%	627
	11th to 20th	Night	6% 1 8% 39% 43% 3	624
	21st to end	Night	6% 2 14% 44% 31% 2	821
September	1st to 10th	Night	6% 2 17% 40% 33% 2	840
	11th to 20th	Night	8% 4 15% 36% 32% 5%	840
	21st to end	Night	10% 5% 14% 41% 27% 3	832
October	1st to 10th	Night	14% 3 21% 34% 25% 3	800
	11th to 20th	Night	16% 7% 15% 34% 25% 4	800
	21st to end	Night	23% 7% 21% 28% 17% 4	880
November	1st to 10th	Night	24% 10% 19% 32% 14%	820
	11th to 20th	Night	30% 11% 21% 25% 12% 1	840
	21st to end	Night	25% 7% 20% 28% 17% 2	840
December	1st to 10th	Night	26% 8% 18% 29% 17% 2	840
	11th to 20th	Night	33% 10% 21% 23% 13% 1	840
	21st to end	Night	31% 14% 22% 23% 10% 1	924

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

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