Molalla
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Molalla clear sky chart from 2005-11-06 to 2026-09-14.

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	16% 8% 2 6% 4 4 4 3 5% 6% 42%	158540
	Night	19% 9% 3 7% 4 4 4 3 4 6% 37%	149945
Transparency	Day	43% 6% 12% 21% 14% 5%	153322
	Night	48% 6% 12% 18% 12% 4	146162
Seeing	Day	23% 8% 22% 27% 15% 4	16983
	Night	27% 6% 14% 30% 20% 3	25872

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	33% 17% 4 9% 6% 5% 5% 3 5% 4 9%	4722
	11th to 20th	Day	21% 9% 2 5% 4 3 4 4 5% 6% 37%	4740
	21st to end	Day	23% 8% 3 7% 5% 4 5% 4 6% 6% 30%	5698
February	1st to 10th	Day	28% 13% 3 8% 5% 4 5% 5% 5% 7% 17%	1890
	11th to 20th	Day	25% 15% 4 9% 7% 5% 4 3 4 4 20%	1845
	21st to end	Day	28% 16% 4 8% 5% 4 4 3 4 5% 20%	1653
March	1st to 10th	Day	16% 12% 4 9% 6% 6% 6% 5% 6% 7% 21%	4831
	11th to 20th	Day	25% 15% 3 8% 5% 4 4 3 4 4 26%	5110
	21st to end	Day	23% 13% 4 10% 6% 6% 6% 5% 7% 7% 13%	5736
April	1st to 10th	Day	26% 15% 3 8% 5% 5% 4 3 5% 6% 18%	2520
	11th to 20th	Day	22% 14% 4 8% 5% 5% 4 4 5% 5% 25%	2489
	21st to end	Day	22% 10% 3 9% 5% 4 4 3 6% 6% 26%	2704
May	1st to 10th	Day	14% 8% 2 6% 4 4 4 3 5% 7% 43%	8076
	11th to 20th	Day	15% 8% 3 8% 6% 5% 5% 4 6% 7% 32%	8160
	21st to end	Day	16% 7% 2 7% 4 4 4 4 6% 8% 36%	8992
June	1st to 10th	Day	22% 9% 3 6% 5% 4 3 4 5% 6% 34%	2940
	11th to 20th	Day	20% 9% 3 6% 5% 5% 5% 4 6% 7% 30%	2940
	21st to end	Day	10% 6% 2 6% 4 4 3 3 4 6% 52%	2940
July	1st to 10th	Day	4 2 1 3 2 3 3 3 4 5% 72%	8219
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 4 78%	8220
	21st to end	Day	4 2 1 2 2 2 2 2 3 5% 76%	8922
August	1st to 10th	Day	4 3 1 3 2 3 3 2 4 5% 70%	7609
	11th to 20th	Day	6% 3 1 4 3 3 4 3 6% 7% 60%	7563
	21st to end	Day	6% 5% 2 4 3 3 4 3 6% 8% 56%	7925
September	1st to 10th	Day	8% 3 2 5% 3 2 3 3 5% 8% 59%	2520
	11th to 20th	Day	11% 7% 3 6% 5% 3 5% 4 6% 6% 45%	2437
	21st to end	Day	16% 5% 2 6% 4 4 3 3 4 7% 47%	2107
October	1st to 10th	Day	17% 5% 2 4 3 3 3 3 4 6% 50%	3280
	11th to 20th	Day	18% 7% 2 8% 5% 5% 5% 4 5% 7% 34%	3261
	21st to end	Day	23% 9% 4 9% 5% 5% 5% 4 6% 8% 23%	3472
November	1st to 10th	Day	30% 10% 3 10% 5% 4 4 3 5% 7% 20%	1759
	11th to 20th	Day	29% 10% 4 9% 6% 5% 4 3 5% 5% 19%	1680
	21st to end	Day	25% 12% 3 8% 5% 5% 4 3 5% 6% 23%	1680
December	1st to 10th	Day	22% 9% 2 6% 4 4 4 4 6% 7% 32%	2700
	11th to 20th	Day	29% 12% 5% 11% 6% 5% 5% 4 5% 6% 12%	3108
	21st to end	Day	34% 16% 4 9% 5% 5% 4 3 4 4 12%	4092
January	1st to 10th	Night	32% 16% 4 9% 6% 5% 4 3 4 4 13%	8172
	11th to 20th	Night	21% 10% 2 5% 4 3 4 3 4 5% 37%	8220
	21st to end	Night	23% 10% 3 9% 4 3 3 2 4 5% 33%	8507
February	1st to 10th	Night	26% 14% 4 7% 6% 5% 5% 4 5% 6% 19%	2730
	11th to 20th	Night	29% 14% 3 8% 4 3 4 2 5% 5% 24%	2662
	21st to end	Night	28% 16% 3 7% 4 3 4 3 4 6% 21%	2152
March	1st to 10th	Night	17% 13% 3 9% 6% 6% 6% 4 6% 6% 22%	5282
	11th to 20th	Night	23% 12% 3 7% 4 4 4 3 4 5% 29%	5110
	21st to end	Night	25% 15% 4 9% 5% 6% 5% 4 6% 7% 15%	5479
April	1st to 10th	Night	25% 15% 4 8% 5% 5% 4 4 5% 5% 21%	2100
	11th to 20th	Night	21% 13% 4 7% 3 4 4 3 5% 6% 29%	2079
	21st to end	Night	25% 11% 3 7% 5% 4 4 4 5% 6% 28%	1914
May	1st to 10th	Night	17% 8% 2 6% 3 3 3 3 5% 7% 43%	4848
	11th to 20th	Night	23% 8% 4 8% 4 4 4 3 4 5% 33%	4700
	21st to end	Night	18% 7% 2 6% 4 3 4 3 6% 8% 37%	5181
June	1st to 10th	Night	20% 9% 2 6% 4 4 5% 4 4 6% 38%	1680
	11th to 20th	Night	19% 10% 3 6% 5% 4 4 3 4 6% 37%	1680
	21st to end	Night	12% 6% 2 5% 4 2 4 4 3 5% 55%	1680
July	1st to 10th	Night	8% 2 1 3 2 2 2 2 4 4 70%	4740
	11th to 20th	Night	2 2 1 3 2 2 2 2 3 3 78%	4740
	21st to end	Night	3 2 1 3 2 2 2 2 4 5% 74%	5153
August	1st to 10th	Night	5% 2 1 3 2 2 3 3 4 6% 69%	5206
	11th to 20th	Night	9% 5% 2 6% 3 4 3 3 5% 6% 55%	5292
	21st to end	Night	8% 5% 2 5% 3 3 3 3 4 5% 58%	6313
September	1st to 10th	Night	8% 4 2 4 2 2 3 2 5% 5% 63%	2100
	11th to 20th	Night	12% 6% 2 5% 4 4 5% 3 4 5% 50%	2030
	21st to end	Night	13% 5% 2 5% 3 3 4 3 6% 7% 50%	2288
October	1st to 10th	Night	15% 5% 2 5% 3 3 3 2 4 6% 51%	3920
	11th to 20th	Night	16% 6% 3 6% 4 4 4 4 6% 8% 37%	3897
	21st to end	Night	24% 10% 4 7% 5% 4 4 4 5% 6% 26%	4334
November	1st to 10th	Night	30% 9% 3 8% 5% 5% 4 3 5% 7% 22%	2754
	11th to 20th	Night	33% 9% 3 9% 5% 4 4 3 4 4 21%	2940
	21st to end	Night	25% 12% 2 6% 5% 4 5% 4 5% 5% 27%	2940
December	1st to 10th	Night	19% 8% 3 6% 4 4 4 3 5% 7% 38%	4700
	11th to 20th	Night	31% 14% 4 9% 5% 5% 5% 3 4 5% 14%	5316
	21st to end	Night	30% 13% 4 9% 5% 5% 5% 3 4 5% 17%	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	77% 7% 6% 7% 4	4723
	11th to 20th	Day	45% 4 9% 16% 15% 11%	4740
	21st to end	Day	54% 5% 6% 14% 16% 4	5698
February	1st to 10th	Day	65% 6% 11% 11% 6%	1890
	11th to 20th	Day	69% 6% 8% 10% 5% 2	1854
	21st to end	Day	68% 4 10% 9% 9% 2	1653
March	1st to 10th	Day	59% 5% 16% 15% 5%	4831
	11th to 20th	Day	62% 5% 7% 17% 9% 1	5110
	21st to end	Day	68% 9% 12% 8% 3	5736
April	1st to 10th	Day	66% 5% 13% 12% 3	2520
	11th to 20th	Day	61% 5% 11% 13% 8% 2	2492
	21st to end	Day	59% 6% 11% 15% 7% 2	2704
May	1st to 10th	Day	40% 4 14% 27% 14%	8076
	11th to 20th	Day	44% 11% 17% 20% 7%	8163
	21st to end	Day	43% 8% 23% 21% 4	8994
June	1st to 10th	Day	52% 5% 15% 20% 7% 1	2940
	11th to 20th	Day	52% 6% 16% 18% 7% 1	2940
	21st to end	Day	34% 5% 17% 30% 10% 4	2940
July	1st to 10th	Day	14% 5% 11% 34% 18% 17%	8151
	11th to 20th	Day	13% 2 6% 20% 39% 21%	8145
	21st to end	Day	13% 3 15% 37% 28% 5%	8723
August	1st to 10th	Day	14% 4 8% 27% 29% 18%	6025
	11th to 20th	Day	21% 6% 18% 37% 14% 3	5962
	21st to end	Day	24% 5% 13% 33% 18% 6%	6216
September	1st to 10th	Day	23% 5% 12% 28% 20% 11%	2520
	11th to 20th	Day	38% 7% 13% 21% 15% 7%	2437
	21st to end	Day	38% 5% 13% 20% 16% 7%	2107
October	1st to 10th	Day	36% 5% 7% 25% 22% 5%	3280
	11th to 20th	Day	48% 6% 16% 17% 11% 2	3261
	21st to end	Day	56% 7% 9% 18% 9% 1	3472
November	1st to 10th	Day	65% 5% 10% 14% 5% 1	1759
	11th to 20th	Day	66% 7% 9% 10% 6% 2	1680
	21st to end	Day	61% 6% 11% 7% 14% 1	1680
December	1st to 10th	Day	49% 5% 11% 10% 21% 3	2700
	11th to 20th	Day	71% 7% 11% 8% 3	3108
	21st to end	Day	74% 7% 8% 8% 2	4092
January	1st to 10th	Night	75% 6% 7% 8% 4 1	8172
	11th to 20th	Night	47% 4 9% 18% 13% 10%	8220
	21st to end	Night	56% 3 5% 11% 18% 7%	8507
February	1st to 10th	Night	66% 6% 10% 11% 6% 2	2730
	11th to 20th	Night	63% 6% 11% 11% 6% 3	2664
	21st to end	Night	65% 4 10% 12% 7% 2	2152
March	1st to 10th	Night	60% 6% 15% 13% 6% 1	5282
	11th to 20th	Night	57% 6% 11% 14% 11% 1	5110
	21st to end	Night	67% 7% 14% 11% 1	5479
April	1st to 10th	Night	65% 6% 13% 12% 4	2100
	11th to 20th	Night	57% 6% 15% 13% 7% 3	2079
	21st to end	Night	57% 6% 14% 14% 6% 3	1914
May	1st to 10th	Night	40% 4 13% 31% 11% 1	4846
	11th to 20th	Night	51% 8% 14% 21% 4 1	4700
	21st to end	Night	43% 9% 23% 21% 4	5182
June	1st to 10th	Night	50% 5% 17% 21% 7% 1	1680
	11th to 20th	Night	49% 5% 16% 21% 7% 1	1680
	21st to end	Night	33% 4 19% 27% 12% 4	1680
July	1st to 10th	Night	18% 4 9% 35% 20% 14%	4700
	11th to 20th	Night	14% 3 8% 18% 42% 17%	4692
	21st to end	Night	14% 3 20% 34% 25% 4	5040
August	1st to 10th	Night	11% 3 8% 33% 29% 16%	4114
	11th to 20th	Night	26% 6% 21% 33% 11% 4	4169
	21st to end	Night	26% 5% 14% 34% 14% 7%	4945
September	1st to 10th	Night	23% 5% 14% 28% 19% 10%	2100
	11th to 20th	Night	35% 8% 11% 24% 13% 10%	2030
	21st to end	Night	34% 4 15% 23% 15% 9%	2288
October	1st to 10th	Night	35% 5% 8% 27% 23% 3	3920
	11th to 20th	Night	43% 7% 16% 19% 12% 2	3897
	21st to end	Night	56% 7% 9% 16% 9% 2	4334
November	1st to 10th	Night	63% 5% 11% 11% 9% 1	2754
	11th to 20th	Night	66% 6% 9% 9% 7% 3	2940
	21st to end	Night	58% 7% 9% 10% 12% 4	2940
December	1st to 10th	Night	45% 5% 10% 17% 21% 2	4700
	11th to 20th	Night	71% 6% 10% 8% 4	5316
	21st to end	Night	68% 8% 13% 8% 2 1	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	40% 14% 18% 14% 13% 1	220
	11th to 20th	Day	35% 5% 17% 20% 17% 6%	220
	21st to end	Day	32% 9% 18% 21% 16% 4	419
February	1st to 10th	Day	37% 9% 20% 22% 10% 3	430
	11th to 20th	Day	37% 13% 21% 21% 6% 2	425
	21st to end	Day	41% 11% 21% 18% 9% 1	407
March	1st to 10th	Day	35% 13% 25% 20% 6% 1	540
	11th to 20th	Day	34% 9% 25% 19% 10% 3	540
	21st to end	Day	36% 12% 26% 20% 6% 1	594
April	1st to 10th	Day	35% 10% 20% 21% 11% 3	540
	11th to 20th	Day	31% 13% 25% 18% 10% 4	532
	21st to end	Day	28% 10% 27% 23% 10% 2	540
May	1st to 10th	Day	23% 9% 26% 26% 13% 3	543
	11th to 20th	Day	27% 12% 20% 24% 14% 4	568
	21st to end	Day	22% 4 22% 32% 16% 5%	617
June	1st to 10th	Day	24% 8% 19% 29% 15% 4	570
	11th to 20th	Day	21% 8% 30% 26% 13% 1	570
	21st to end	Day	10% 5% 25% 38% 16% 5%	570
July	1st to 10th	Day	6% 3 22% 41% 24% 4	566
	11th to 20th	Day	4 5% 24% 41% 22% 5%	564
	21st to end	Day	5% 2 19% 42% 24% 7%	619
August	1st to 10th	Day	5% 5% 16% 44% 23% 8%	567
	11th to 20th	Day	5% 2 18% 39% 28% 8%	557
	21st to end	Day	8% 6% 22% 36% 21% 7%	627
September	1st to 10th	Day	9% 4 24% 34% 22% 6%	570
	11th to 20th	Day	14% 7% 21% 33% 20% 5%	543
	21st to end	Day	19% 7% 22% 31% 17% 4	530
October	1st to 10th	Day	22% 8% 22% 24% 18% 6%	530
	11th to 20th	Day	25% 7% 18% 29% 16% 5%	530
	21st to end	Day	29% 10% 24% 20% 11% 5%	533
November	1st to 10th	Day	36% 12% 15% 22% 11% 3	280
	11th to 20th	Day	31% 12% 21% 16% 13% 7%	220
	21st to end	Day	34% 6% 19% 20% 15% 6%	220
December	1st to 10th	Day	38% 9% 14% 17% 15% 8%	220
	11th to 20th	Day	46% 10% 17% 15% 9% 2	220
	21st to end	Day	47% 8% 17% 12% 12% 3	242
January	1st to 10th	Night	40% 11% 14% 20% 14% 1	840
	11th to 20th	Night	36% 6% 13% 24% 18% 3	840
	21st to end	Night	33% 6% 15% 28% 15% 3	924
February	1st to 10th	Night	34% 8% 17% 26% 13% 2	840
	11th to 20th	Night	38% 9% 15% 23% 15% 1	824
	21st to end	Night	40% 7% 17% 27% 9%	692
March	1st to 10th	Night	34% 9% 17% 28% 12% 1	840
	11th to 20th	Night	32% 7% 18% 29% 13% 1	840
	21st to end	Night	36% 9% 18% 25% 10% 2	924
April	1st to 10th	Night	33% 8% 15% 27% 16% 1	840
	11th to 20th	Night	31% 7% 16% 31% 13% 3	831
	21st to end	Night	33% 5% 15% 31% 15% 2	654
May	1st to 10th	Night	26% 4 16% 33% 20% 2	467
	11th to 20th	Night	24% 6% 15% 28% 25% 1	414
	21st to end	Night	24% 4 14% 33% 24% 3	455
June	1st to 10th	Night	24% 5% 15% 32% 22% 2	420
	11th to 20th	Night	25% 4 15% 36% 18% 1	420
	21st to end	Night	15% 4 13% 39% 29% 1	420
July	1st to 10th	Night	9% 2 8% 41% 38% 2	410
	11th to 20th	Night	7% 1 11% 46% 33% 2	408
	21st to end	Night	3 2 7% 43% 41% 4	460
August	1st to 10th	Night	5% 2 6% 32% 48% 8%	597
	11th to 20th	Night	7% 2 6% 32% 46% 8%	624
	21st to end	Night	7% 3 11% 40% 34% 4	852
September	1st to 10th	Night	10% 2 12% 38% 34% 4	840
	11th to 20th	Night	15% 4 8% 32% 35% 6%	812
	21st to end	Night	16% 3 12% 34% 29% 5%	800
October	1st to 10th	Night	20% 5% 15% 31% 25% 4	800
	11th to 20th	Night	23% 6% 13% 30% 25% 4	800
	21st to end	Night	29% 6% 19% 27% 14% 4	880
November	1st to 10th	Night	34% 7% 15% 30% 13% 1	820
	11th to 20th	Night	39% 12% 13% 23% 11% 2	840
	21st to end	Night	31% 7% 14% 31% 16% 2	840
December	1st to 10th	Night	34% 5% 13% 29% 16% 3	840
	11th to 20th	Night	41% 8% 14% 24% 12% 1	840
	21st to end	Night	41% 10% 16% 21% 10% 1	924

Page generated at 2026-09-11 01:11:55. Version ac07

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