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 2024-11-02.

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% 5% 5% 4 4 5% 6% 38%	101702
	Night	17% 9% 3 7% 5% 4 4 3 5% 6% 38%	97387
Transparency	Day	45% 10% 12% 16% 12% 4	101446
	Night	46% 10% 13% 17% 11% 4	97232
Seeing	Day	17% 11% 20% 26% 20% 6%	14834
	Night	19% 8% 19% 33% 20% 2	23579

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% 14% 6% 13% 7% 6% 4 3 3 3 8%	2539
	11th to 20th	Day	35% 12% 4 10% 5% 5% 4 3 3 3 15%	2540
	21st to end	Day	31% 13% 5% 11% 6% 5% 5% 3 4 4 12%	3114
February	1st to 10th	Day	24% 14% 5% 9% 6% 6% 5% 4 5% 6% 15%	1710
	11th to 20th	Day	23% 12% 5% 12% 7% 5% 5% 3 4 6% 18%	1665
	21st to end	Day	22% 15% 4 11% 6% 6% 4 4 4 5% 18%	1471
March	1st to 10th	Day	18% 14% 5% 10% 6% 7% 6% 4 6% 7% 17%	3340
	11th to 20th	Day	17% 10% 3 9% 6% 4 3 3 4 6% 35%	3490
	21st to end	Day	20% 12% 5% 11% 7% 6% 6% 4 5% 6% 17%	3876
April	1st to 10th	Day	21% 12% 4 10% 7% 6% 5% 4 6% 6% 20%	2280
	11th to 20th	Day	19% 12% 3 8% 6% 5% 5% 4 5% 5% 26%	2262
	21st to end	Day	17% 9% 3 9% 7% 5% 6% 5% 6% 8% 24%	2470
May	1st to 10th	Day	16% 9% 3 7% 5% 5% 4 4 6% 6% 35%	4309
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 5% 7% 51%	4377
	21st to end	Day	15% 7% 2 7% 6% 7% 7% 6% 7% 7% 28%	4813
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	15% 7% 3 7% 5% 4 5% 4 5% 6% 38%	1900
	11th to 20th	Day	15% 8% 4 10% 6% 4 6% 4 6% 7% 30%	1900
	21st to end	Day	22% 10% 4 9% 5% 4 4 3 4 6% 28%	2074
November	1st to 10th	Day	23% 14% 4 11% 6% 5% 5% 4 6% 6% 15%	1565
	11th to 20th	Day	27% 13% 4 9% 7% 6% 4 3 4 5% 19%	1520
	21st to end	Day	24% 11% 4 10% 6% 5% 4 4 4 5% 23%	1520
December	1st to 10th	Day	23% 13% 6% 9% 5% 5% 5% 3 5% 3 22%	1520
	11th to 20th	Day	26% 12% 5% 9% 6% 6% 5% 4 7% 8% 13%	1928
	21st to end	Day	29% 15% 7% 14% 7% 6% 5% 4 4 3 7%	2794
January	1st to 10th	Night	29% 14% 5% 11% 6% 6% 5% 3 5% 4 11%	4406
	11th to 20th	Night	33% 13% 4 9% 5% 4 4 3 4 4 17%	4420
	21st to end	Night	35% 13% 4 8% 5% 4 4 3 4 4 16%	4548
February	1st to 10th	Night	21% 13% 4 10% 6% 6% 5% 4 6% 6% 19%	2470
	11th to 20th	Night	22% 11% 3 8% 5% 4 6% 3 5% 5% 27%	2402
	21st to end	Night	20% 12% 4 11% 7% 5% 5% 4 5% 6% 23%	1981
March	1st to 10th	Night	15% 14% 4 12% 7% 6% 6% 4 5% 6% 22%	3533
	11th to 20th	Night	15% 8% 3 7% 5% 4 4 3 5% 8% 39%	3490
	21st to end	Night	20% 13% 4 10% 7% 7% 5% 4 5% 6% 19%	3777
April	1st to 10th	Night	20% 12% 4 9% 5% 5% 4 4 5% 6% 26%	1900
	11th to 20th	Night	16% 10% 3 8% 5% 5% 4 4 5% 7% 33%	1861
	21st to end	Night	17% 8% 3 7% 5% 4 5% 5% 6% 8% 33%	1710
May	1st to 10th	Night	18% 7% 2 5% 4 4 3 3 5% 6% 42%	2651
	11th to 20th	Night	8% 4 1 5% 3 3 3 2 4 7% 59%	2516
	21st to end	Night	7% 7% 2 7% 5% 5% 6% 5% 7% 8% 41%	2762
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	11% 6% 2 6% 4 4 4 3 5% 5% 49%	2280
	11th to 20th	Night	14% 6% 3 5% 4 5% 4 4 6% 8% 41%	2280
	21st to end	Night	20% 8% 4 6% 4 3 3 4 5% 5% 38%	2523
November	1st to 10th	Night	23% 12% 3 9% 5% 5% 5% 3 5% 6% 24%	2535
	11th to 20th	Night	28% 10% 3 8% 5% 4 6% 3 5% 5% 22%	2660
	21st to end	Night	22% 9% 3 9% 5% 5% 4 4 6% 6% 28%	2660
December	1st to 10th	Night	23% 12% 4 8% 5% 4 5% 3 5% 6% 25%	2660
	11th to 20th	Night	27% 11% 4 10% 6% 5% 4 4 5% 7% 16%	3276
	21st to end	Night	26% 13% 4 11% 6% 5% 4 3 6% 6% 15%	4862

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% 12% 4 3 2 1	2539
	11th to 20th	Day	73% 9% 6% 8% 2 1	2540
	21st to end	Day	73% 10% 6% 6% 4	3114
February	1st to 10th	Day	67% 12% 10% 8% 4	1710
	11th to 20th	Day	68% 11% 8% 8% 4 1	1674
	21st to end	Day	66% 10% 9% 8% 5% 2	1471
March	1st to 10th	Day	60% 14% 15% 9% 3	3340
	11th to 20th	Day	49% 9% 9% 22% 10%	3490
	21st to end	Day	64% 14% 12% 7% 4	3876
April	1st to 10th	Day	63% 10% 13% 11% 3	2280
	11th to 20th	Day	57% 11% 11% 12% 7% 2	2265
	21st to end	Day	57% 11% 13% 11% 7% 1	2470
May	1st to 10th	Day	46% 12% 14% 17% 12%	4309
	11th to 20th	Day	28% 10% 22% 26% 13% 1	4380
	21st to end	Day	46% 19% 20% 13% 2	4814
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	44% 9% 10% 19% 15% 3	1900
	11th to 20th	Day	52% 9% 14% 13% 12% 1	1900
	21st to end	Day	58% 8% 9% 12% 13% 1	2074
November	1st to 10th	Day	68% 10% 9% 10% 3	1565
	11th to 20th	Day	67% 9% 9% 7% 6% 1	1520
	21st to end	Day	63% 10% 7% 9% 10% 1	1520
December	1st to 10th	Day	64% 9% 8% 10% 8% 1	1520
	11th to 20th	Day	67% 12% 11% 9% 1	1928
	21st to end	Day	79% 10% 5% 3 2	2794
January	1st to 10th	Night	72% 12% 7% 4 3 1	4406
	11th to 20th	Night	70% 9% 6% 10% 4 1	4420
	21st to end	Night	71% 9% 8% 7% 5% 1	4548
February	1st to 10th	Night	64% 11% 10% 11% 4	2470
	11th to 20th	Night	58% 10% 13% 10% 6% 2	2404
	21st to end	Night	60% 11% 12% 10% 6% 2	1981
March	1st to 10th	Night	56% 14% 14% 13% 3	3533
	11th to 20th	Night	40% 14% 12% 24% 9% 1	3490
	21st to end	Night	61% 14% 12% 12% 1	3777
April	1st to 10th	Night	58% 10% 14% 13% 5%	1900
	11th to 20th	Night	49% 10% 17% 14% 8% 3	1861
	21st to end	Night	48% 11% 15% 16% 7% 2	1710
May	1st to 10th	Night	40% 10% 16% 24% 9% 1	2651
	11th to 20th	Night	25% 6% 18% 34% 15% 2	2516
	21st to end	Night	34% 19% 30% 13% 4	2762
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	36% 8% 10% 25% 17% 3	2280
	11th to 20th	Night	40% 10% 14% 18% 15% 3	2280
	21st to end	Night	47% 9% 11% 16% 15% 2	2523
November	1st to 10th	Night	58% 10% 11% 14% 6%	2535
	11th to 20th	Night	63% 9% 9% 9% 7% 2	2660
	21st to end	Night	56% 11% 10% 9% 12% 2	2660
December	1st to 10th	Night	59% 10% 10% 10% 10% 1	2660
	11th to 20th	Night	66% 11% 10% 9% 4	3276
	21st to end	Night	65% 15% 11% 6% 2	4862

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% 17% 16% 9% 2	180
	11th to 20th	Day	36% 12% 16% 19% 12% 4	180
	21st to end	Day	27% 12% 19% 21% 18% 3	388
February	1st to 10th	Day	28% 15% 22% 16% 16% 3	370
	11th to 20th	Day	30% 14% 25% 17% 12% 2	365
	21st to end	Day	27% 21% 21% 19% 11% 1	335
March	1st to 10th	Day	27% 17% 23% 23% 8% 2	460
	11th to 20th	Day	24% 15% 20% 23% 15% 3	460
	21st to end	Day	25% 19% 24% 21% 10% 1	506
April	1st to 10th	Day	24% 18% 24% 18% 12% 4	460
	11th to 20th	Day	25% 16% 24% 22% 8% 5%	452
	21st to end	Day	21% 16% 25% 25% 12% 2	460
May	1st to 10th	Day	14% 16% 24% 25% 16% 5%	463
	11th to 20th	Day	20% 10% 18% 28% 17% 7%	488
	21st to end	Day	13% 9% 20% 28% 20% 9%	529
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	24% 13% 27% 19% 11% 6%	523
November	1st to 10th	Day	27% 18% 20% 21% 11% 3	217
	11th to 20th	Day	26% 13% 23% 15% 16% 7%	180
	21st to end	Day	26% 14% 19% 18% 17% 6%	180
December	1st to 10th	Day	33% 11% 15% 21% 13% 7%	180
	11th to 20th	Day	32% 13% 23% 20% 9% 2	180
	21st to end	Day	33% 17% 19% 17% 13% 2	198
January	1st to 10th	Night	34% 13% 16% 21% 13% 2	760
	11th to 20th	Night	31% 12% 16% 23% 17% 2	760
	21st to end	Night	28% 7% 16% 29% 17% 3	836
February	1st to 10th	Night	24% 11% 19% 29% 15% 2	760
	11th to 20th	Night	25% 11% 20% 27% 17% 1	744
	21st to end	Night	24% 15% 21% 29% 11%	628
March	1st to 10th	Night	24% 11% 23% 28% 14% 1	760
	11th to 20th	Night	21% 9% 21% 33% 15% 1	760
	21st to end	Night	25% 10% 25% 26% 13% 1	836
April	1st to 10th	Night	24% 11% 21% 27% 17% 1	760
	11th to 20th	Night	18% 11% 25% 31% 14% 1	733
	21st to end	Night	20% 8% 21% 35% 15% 1	570
May	1st to 10th	Night	13% 7% 24% 39% 17% 1	452
	11th to 20th	Night	14% 5% 19% 38% 23% 1	374
	21st to end	Night	12% 6% 22% 38% 21% 1	411
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% 8% 21% 27% 17% 4	836
November	1st to 10th	Night	24% 10% 19% 32% 15%	744
	11th to 20th	Night	30% 10% 21% 25% 13% 1	760
	21st to end	Night	25% 7% 20% 28% 17% 2	760
December	1st to 10th	Night	26% 8% 18% 29% 16% 2	760
	11th to 20th	Night	32% 10% 21% 24% 13% 1	760
	21st to end	Night	31% 13% 21% 24% 10% 1	836

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