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 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	18% 9% 3 7% 4 4 4 3 5% 6% 38%	101540
	Night	21% 10% 3 7% 4 4 4 3 4 5% 35%	97590
Transparency	Day	47% 6% 12% 18% 13% 5%	101283
	Night	51% 6% 12% 16% 11% 4	97436
Seeing	Day	24% 8% 21% 27% 16% 4	14646
	Night	27% 6% 14% 29% 21% 3	23578

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% 19% 4 9% 6% 4 5% 3 4 4 9%	2539
	11th to 20th	Day	38% 12% 3 7% 6% 3 4 3 3 3 19%	2540
	21st to end	Day	31% 12% 3 9% 6% 5% 5% 4 5% 6% 15%	3057
February	1st to 10th	Day	30% 12% 3 8% 5% 4 5% 5% 5% 7% 18%	1710
	11th to 20th	Day	25% 15% 4 8% 7% 5% 4 3 4 5% 20%	1665
	21st to end	Day	28% 17% 4 7% 5% 4 4 3 4 5% 20%	1499
March	1st to 10th	Day	16% 13% 4 9% 6% 7% 6% 5% 7% 7% 20%	3282
	11th to 20th	Day	18% 11% 3 7% 4 3 3 4 4 4 38%	3490
	21st to end	Day	23% 14% 4 11% 7% 6% 5% 4 5% 5% 15%	3912
April	1st to 10th	Day	27% 16% 4 9% 5% 5% 4 3 5% 5% 18%	2280
	11th to 20th	Day	23% 15% 4 7% 5% 5% 4 4 5% 5% 24%	2249
	21st to end	Day	24% 11% 3 9% 5% 4 4 3 6% 6% 24%	2446
May	1st to 10th	Day	23% 11% 3 7% 4 4 4 3 4 5% 31%	4353
	11th to 20th	Day	13% 7% 2 6% 4 4 4 3 5% 6% 45%	4377
	21st to end	Day	23% 9% 3 8% 6% 5% 5% 4 6% 6% 25%	4813
June	1st to 10th	Day	23% 10% 3 6% 5% 4 3 4 5% 6% 32%	2660
	11th to 20th	Day	22% 9% 3 7% 6% 5% 5% 4 6% 7% 27%	2660
	21st to end	Day	10% 5% 2 5% 4 4 3 3 4 6% 54%	2660
July	1st to 10th	Day	4 3 1 2 2 3 3 2 4 5% 73%	4420
	11th to 20th	Day	4 2 1 2 2 2 2 2 3 4 75%	4420
	21st to end	Day	5% 3 1 2 2 2 2 2 3 4 73%	4790
August	1st to 10th	Day	3 3 1 4 3 3 3 3 4 6% 67%	4127
	11th to 20th	Day	5% 4 1 5% 3 3 4 4 6% 7% 58%	4026
	21st to end	Day	8% 6% 2 4 3 3 4 3 5% 7% 56%	4280
September	1st to 10th	Day	8% 3 1 4 2 2 2 3 5% 8% 62%	2280
	11th to 20th	Day	11% 6% 3 7% 5% 3 5% 4 6% 6% 44%	2280
	21st to end	Day	16% 6% 2 6% 4 4 3 3 4 7% 46%	2002
October	1st to 10th	Day	19% 7% 2 5% 3 4 4 5% 5% 6% 41%	1900
	11th to 20th	Day	19% 8% 3 9% 4 4 4 3 5% 7% 35%	1900
	21st to end	Day	25% 8% 3 8% 4 4 4 4 5% 6% 28%	2043
November	1st to 10th	Day	30% 10% 4 10% 5% 4 3 3 5% 6% 21%	1598
	11th to 20th	Day	30% 10% 4 8% 6% 5% 4 3 5% 5% 21%	1520
	21st to end	Day	26% 12% 3 8% 5% 5% 4 3 5% 5% 24%	1520
December	1st to 10th	Day	25% 12% 3 8% 5% 4 4 3 5% 5% 26%	1520
	11th to 20th	Day	28% 10% 4 8% 5% 5% 5% 5% 6% 8% 17%	1928
	21st to end	Day	29% 16% 4 9% 5% 5% 4 4 5% 5% 14%	2794
January	1st to 10th	Night	31% 19% 4 10% 6% 6% 4 3 3 4 12%	4406
	11th to 20th	Night	36% 14% 3 7% 5% 3 3 2 4 4 18%	4420
	21st to end	Night	34% 13% 3 9% 5% 4 4 2 5% 5% 16%	4605
February	1st to 10th	Night	28% 14% 4 7% 6% 5% 5% 3 5% 6% 18%	2470
	11th to 20th	Night	29% 14% 3 8% 4 4 4 2 5% 5% 24%	2402
	21st to end	Night	27% 17% 3 7% 5% 3 4 3 4 6% 20%	1954
March	1st to 10th	Night	15% 15% 4 10% 7% 6% 6% 4 6% 6% 21%	3591
	11th to 20th	Night	16% 9% 2 5% 4 4 4 3 4 6% 41%	3490
	21st to end	Night	24% 16% 4 9% 6% 6% 5% 4 5% 6% 15%	3739
April	1st to 10th	Night	26% 16% 4 8% 4 4 4 4 4 5% 21%	1900
	11th to 20th	Night	21% 13% 4 7% 3 4 4 3 6% 6% 28%	1879
	21st to end	Night	26% 11% 3 7% 5% 4 4 4 5% 6% 26%	1732
May	1st to 10th	Night	26% 12% 3 6% 4 3 3 3 4 4 33%	2609
	11th to 20th	Night	16% 6% 3 6% 3 3 3 3 4 6% 46%	2516
	21st to end	Night	23% 9% 3 8% 5% 4 4 4 6% 6% 29%	2762
June	1st to 10th	Night	21% 9% 2 6% 4 4 5% 4 4 5% 36%	1520
	11th to 20th	Night	20% 11% 3 7% 5% 3 4 3 4 5% 34%	1520
	21st to end	Night	10% 6% 2 5% 3 2 4 3 3 5% 56%	1520
July	1st to 10th	Night	5% 3 1 4 2 2 2 1 3 3 76%	2540
	11th to 20th	Night	3 2 1 3 2 2 1 2 3 3 76%	2540
	21st to end	Night	4 2 1 3 2 2 2 2 3 4 76%	2761
August	1st to 10th	Night	2 2 1 2 2 2 2 2 4 6% 73%	2807
	11th to 20th	Night	6% 6% 2 6% 3 4 3 3 5% 7% 55%	2812
	21st to end	Night	11% 4 2 5% 2 2 2 2 3 5% 60%	3393
September	1st to 10th	Night	7% 4 1 4 2 2 3 2 4 4 66%	1900
	11th to 20th	Night	12% 6% 2 5% 5% 4 5% 3 4 5% 50%	1900
	21st to end	Night	13% 5% 1 5% 3 3 4 3 6% 7% 49%	2173
October	1st to 10th	Night	18% 7% 2 6% 3 3 3 2 4 5% 46%	2280
	11th to 20th	Night	19% 6% 3 7% 4 3 4 3 5% 7% 40%	2280
	21st to end	Night	24% 9% 3 6% 5% 3 3 3 4 5% 35%	2553
November	1st to 10th	Night	30% 9% 2 8% 5% 4 4 3 5% 7% 22%	2498
	11th to 20th	Night	32% 8% 3 8% 5% 4 5% 3 5% 4 23%	2660
	21st to end	Night	25% 12% 2 6% 5% 4 5% 4 5% 5% 29%	2660
December	1st to 10th	Night	27% 10% 4 7% 4 4 4 3 5% 6% 27%	2660
	11th to 20th	Night	28% 12% 3 8% 5% 4 4 3 5% 6% 21%	3276
	21st to end	Night	26% 14% 4 9% 5% 6% 5% 3 5% 5% 18%	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% 8% 6% 6% 2 1	2539
	11th to 20th	Day	72% 4 7% 9% 4 3	2540
	21st to end	Day	70% 7% 7% 9% 6% 1	3057
February	1st to 10th	Day	66% 6% 11% 11% 6%	1710
	11th to 20th	Day	69% 6% 8% 10% 4 2	1674
	21st to end	Day	68% 4 10% 9% 6% 2	1499
March	1st to 10th	Day	61% 5% 16% 14% 3	3282
	11th to 20th	Day	51% 5% 8% 23% 12% 1	3490
	21st to end	Day	70% 8% 10% 8% 4	3912
April	1st to 10th	Day	68% 5% 13% 11% 3	2280
	11th to 20th	Day	63% 5% 10% 12% 8% 3	2252
	21st to end	Day	61% 6% 12% 13% 7% 2	2446
May	1st to 10th	Day	54% 5% 14% 16% 11%	4353
	11th to 20th	Day	35% 9% 17% 26% 12% 1	4380
	21st to end	Day	57% 10% 17% 14% 2	4814
June	1st to 10th	Day	54% 5% 16% 18% 6% 1	2660
	11th to 20th	Day	56% 6% 17% 15% 6%	2660
	21st to end	Day	33% 4 17% 30% 11% 4	2660
July	1st to 10th	Day	15% 4 9% 19% 22% 31%	4351
	11th to 20th	Day	14% 3 7% 18% 37% 22%	4345
	21st to end	Day	15% 3 10% 27% 36% 8%	4639
August	1st to 10th	Day	18% 4 10% 29% 28% 11%	4111
	11th to 20th	Day	23% 7% 18% 34% 14% 4	4065
	21st to end	Day	28% 5% 13% 24% 22% 8%	4279
September	1st to 10th	Day	22% 4 11% 30% 21% 12%	2280
	11th to 20th	Day	38% 7% 13% 20% 14% 7%	2280
	21st to end	Day	39% 5% 14% 20% 15% 7%	2002
October	1st to 10th	Day	43% 6% 10% 21% 16% 5%	1900
	11th to 20th	Day	49% 6% 13% 16% 14% 3	1900
	21st to end	Day	56% 6% 8% 15% 14% 2	2043
November	1st to 10th	Day	66% 5% 10% 13% 5% 1	1598
	11th to 20th	Day	65% 7% 9% 10% 7% 2	1520
	21st to end	Day	62% 5% 9% 7% 15% 1	1520
December	1st to 10th	Day	60% 7% 9% 11% 10% 3	1520
	11th to 20th	Day	65% 7% 13% 11% 4	1928
	21st to end	Day	71% 8% 10% 8% 3 1	2794
January	1st to 10th	Night	77% 6% 6% 6% 3 1	4406
	11th to 20th	Night	71% 4 8% 11% 4 2	4420
	21st to end	Night	72% 4 7% 9% 6% 1	4605
February	1st to 10th	Night	68% 6% 9% 10% 6% 2	2470
	11th to 20th	Night	63% 5% 12% 11% 7% 2	2404
	21st to end	Night	66% 4 10% 11% 6% 2	1954
March	1st to 10th	Night	61% 6% 16% 13% 4	3591
	11th to 20th	Night	45% 7% 13% 19% 15% 1	3490
	21st to end	Night	69% 8% 12% 10% 1	3739
April	1st to 10th	Night	66% 6% 13% 11% 4	1900
	11th to 20th	Night	57% 6% 15% 12% 6% 3	1879
	21st to end	Night	59% 5% 14% 14% 5% 3	1732
May	1st to 10th	Night	54% 5% 13% 18% 8% 2	2609
	11th to 20th	Night	36% 7% 17% 29% 7% 2	2516
	21st to end	Night	52% 12% 23% 11% 3	2762
June	1st to 10th	Night	51% 5% 17% 21% 5%	1520
	11th to 20th	Night	53% 5% 17% 19% 5% 1	1520
	21st to end	Night	32% 4 19% 28% 11% 5%	1520
July	1st to 10th	Night	16% 4 7% 20% 27% 26%	2500
	11th to 20th	Night	15% 3 7% 19% 35% 22%	2492
	21st to end	Night	12% 4 13% 28% 36% 7%	2674
August	1st to 10th	Night	13% 3 11% 37% 27% 9%	2799
	11th to 20th	Night	28% 6% 21% 28% 12% 4	2839
	21st to end	Night	28% 4 12% 29% 17% 10%	3393
September	1st to 10th	Night	21% 4 13% 29% 20% 11%	1900
	11th to 20th	Night	34% 8% 11% 24% 13% 10%	1900
	21st to end	Night	34% 5% 16% 22% 15% 9%	2173
October	1st to 10th	Night	42% 4 9% 22% 18% 5%	2280
	11th to 20th	Night	44% 6% 12% 18% 16% 4	2280
	21st to end	Night	52% 6% 8% 14% 15% 4	2553
November	1st to 10th	Night	62% 5% 12% 11% 9% 1	2498
	11th to 20th	Night	64% 6% 10% 9% 8% 3	2660
	21st to end	Night	58% 6% 9% 10% 13% 4	2660
December	1st to 10th	Night	59% 5% 11% 12% 11% 3	2660
	11th to 20th	Night	64% 6% 12% 11% 7% 1	3276
	21st to end	Night	66% 9% 12% 10% 3 1	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	38% 14% 19% 14% 13% 2	180
	11th to 20th	Day	43% 5% 17% 18% 13% 4	180
	21st to end	Day	35% 8% 17% 20% 16% 4	357
February	1st to 10th	Day	38% 8% 20% 21% 10% 3	370
	11th to 20th	Day	38% 12% 21% 21% 6% 2	365
	21st to end	Day	41% 11% 20% 17% 9% 1	349
March	1st to 10th	Day	34% 12% 26% 21% 7% 1	460
	11th to 20th	Day	31% 8% 26% 20% 11% 3	460
	21st to end	Day	36% 12% 25% 21% 6% 1	506
April	1st to 10th	Day	37% 11% 20% 20% 10% 2	460
	11th to 20th	Day	33% 13% 25% 16% 9% 3	452
	21st to end	Day	31% 10% 26% 21% 10% 2	460
May	1st to 10th	Day	26% 9% 25% 25% 12% 3	463
	11th to 20th	Day	27% 8% 20% 26% 15% 4	488
	21st to end	Day	24% 4 22% 30% 16% 5%	529
June	1st to 10th	Day	24% 8% 18% 30% 16% 4	490
	11th to 20th	Day	24% 9% 29% 23% 14% 2	490
	21st to end	Day	10% 5% 25% 38% 17% 6%	490
July	1st to 10th	Day	7% 3 23% 38% 24% 4	486
	11th to 20th	Day	4 5% 21% 43% 22% 5%	484
	21st to end	Day	6% 2 17% 44% 24% 7%	531
August	1st to 10th	Day	5% 3 16% 45% 24% 7%	487
	11th to 20th	Day	5% 2 17% 38% 30% 8%	477
	21st to end	Day	8% 6% 22% 36% 22% 6%	539
September	1st to 10th	Day	9% 5% 23% 35% 22% 6%	490
	11th to 20th	Day	14% 7% 21% 33% 21% 5%	490
	21st to end	Day	20% 7% 21% 31% 17% 4	490
October	1st to 10th	Day	21% 8% 21% 24% 19% 7%	490
	11th to 20th	Day	24% 7% 18% 29% 17% 6%	490
	21st to end	Day	29% 10% 25% 20% 11% 5%	492
November	1st to 10th	Day	36% 11% 16% 24% 10% 3	233
	11th to 20th	Day	28% 11% 21% 17% 15% 8%	180
	21st to end	Day	34% 7% 19% 18% 15% 7%	180
December	1st to 10th	Day	37% 9% 14% 18% 14% 7%	180
	11th to 20th	Day	44% 10% 18% 16% 10% 2	180
	21st to end	Day	46% 7% 19% 13% 13% 3	198
January	1st to 10th	Night	40% 10% 14% 19% 16% 2	760
	11th to 20th	Night	39% 7% 13% 22% 17% 3	760
	21st to end	Night	35% 6% 13% 28% 15% 3	836
February	1st to 10th	Night	36% 8% 15% 26% 13% 2	760
	11th to 20th	Night	38% 9% 14% 23% 16% 1	744
	21st to end	Night	40% 7% 16% 27% 10%	628
March	1st to 10th	Night	33% 9% 18% 27% 13% 1	760
	11th to 20th	Night	29% 7% 17% 30% 15% 1	760
	21st to end	Night	36% 9% 18% 25% 11% 2	836
April	1st to 10th	Night	34% 8% 15% 26% 15% 1	760
	11th to 20th	Night	31% 7% 16% 29% 14% 3	751
	21st to end	Night	34% 6% 15% 30% 14% 2	592
May	1st to 10th	Night	27% 4 17% 31% 19% 2	423
	11th to 20th	Night	22% 5% 15% 29% 28% 1	374
	21st to end	Night	25% 3 13% 32% 23% 3	411
June	1st to 10th	Night	25% 4 13% 33% 23% 2	380
	11th to 20th	Night	27% 4 15% 34% 18% 1	380
	21st to end	Night	13% 3 14% 39% 30% 1	380
July	1st to 10th	Night	9% 2 8% 41% 38% 2	370
	11th to 20th	Night	7% 1 11% 45% 33% 2	368
	21st to end	Night	3 2 6% 44% 41% 5%	416
August	1st to 10th	Night	4 1 5% 32% 49% 8%	539
	11th to 20th	Night	6% 2 6% 30% 47% 9%	564
	21st to end	Night	8% 3 11% 39% 35% 5%	770
September	1st to 10th	Night	9% 2 11% 38% 35% 4	760
	11th to 20th	Night	15% 3 8% 32% 36% 7%	760
	21st to end	Night	17% 3 12% 34% 30% 5%	760
October	1st to 10th	Night	21% 4 14% 30% 26% 4	760
	11th to 20th	Night	22% 6% 11% 30% 26% 5%	760
	21st to end	Night	30% 6% 18% 26% 15% 5%	836
November	1st to 10th	Night	35% 6% 15% 30% 13% 1	744
	11th to 20th	Night	38% 11% 12% 24% 13% 2	760
	21st to end	Night	31% 7% 13% 31% 16% 2	760
December	1st to 10th	Night	34% 5% 13% 30% 15% 3	760
	11th to 20th	Night	40% 7% 14% 25% 13% 1	760
	21st to end	Night	42% 9% 15% 22% 11% 1	836

Page generated at 2024-10-29 22:22:53. Version ac07

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