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 2024-03-08.

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	21% 9% 3 6% 5% 3 4 4 5% 6% 34%	78507
	Night	23% 10% 3 6% 5% 3 4 4 4 6% 32%	81076
Transparency	Day	52% 6% 12% 17% 11% 3	78210
	Night	54% 5% 11% 16% 10% 3	80894
Seeing	Day	24% 7% 21% 27% 16% 4	13695
	Night	28% 6% 13% 29% 21% 3	22839

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	34% 19% 4 8% 7% 3 5% 4 4 4 9%	2539
	11th to 20th	Day	38% 12% 4 7% 6% 3 3 4 3 3 19%	2540
	21st to end	Day	31% 12% 3 8% 7% 4 5% 5% 5% 6% 15%	3057
February	1st to 10th	Day	30% 11% 4 7% 6% 3 5% 5% 5% 7% 18%	1710
	11th to 20th	Day	26% 14% 4 7% 8% 4 5% 4 4 5% 20%	1665
	21st to end	Day	29% 16% 5% 6% 5% 3 4 4 4 5% 20%	1499
March	1st to 10th	Day	24% 12% 4 7% 7% 5% 6% 5% 6% 6% 19%	1953
	11th to 20th	Day	28% 13% 5% 8% 6% 3 4 4 4 5% 20%	1980
	21st to end	Day	28% 14% 5% 9% 7% 5% 5% 5% 4 5% 15%	2227
April	1st to 10th	Day	28% 14% 4 8% 6% 3 4 4 5% 6% 17%	2160
	11th to 20th	Day	25% 14% 4 7% 5% 3 5% 4 5% 5% 23%	2129
	21st to end	Day	23% 10% 4 8% 6% 3 5% 4 5% 7% 24%	2317
May	1st to 10th	Day	20% 10% 3 6% 5% 3 5% 4 4 6% 34%	2479
	11th to 20th	Day	21% 9% 4 6% 6% 3 5% 5% 5% 6% 30%	2477
	21st to end	Day	26% 8% 3 6% 5% 3 5% 4 5% 7% 27%	2723
June	1st to 10th	Day	24% 9% 3 6% 6% 3 4 4 5% 6% 31%	2520
	11th to 20th	Day	23% 8% 4 6% 6% 4 5% 5% 7% 6% 26%	2520
	21st to end	Day	10% 5% 3 5% 4 3 4 3 4 6% 54%	2520
July	1st to 10th	Day	6% 4 1 3 3 3 4 4 5% 7% 61%	2520
	11th to 20th	Day	7% 3 1 3 3 2 3 3 5% 6% 64%	2520
	21st to end	Day	6% 3 1 2 2 1 2 2 3 4 74%	2741
August	1st to 10th	Day	4 3 1 3 2 3 3 4 5% 7% 63%	2351
	11th to 20th	Day	5% 3 1 3 3 2 2 4 4 6% 67%	2298
	21st to end	Day	6% 4 2 4 4 2 4 4 6% 7% 57%	2437
September	1st to 10th	Day	8% 3 1 3 3 1 3 3 4 7% 63%	2160
	11th to 20th	Day	11% 6% 3 6% 6% 3 4 4 5% 6% 45%	2160
	21st to end	Day	16% 6% 2 5% 5% 3 3 4 5% 6% 45%	1898
October	1st to 10th	Day	19% 7% 2 4 4 3 4 6% 5% 6% 40%	1800
	11th to 20th	Day	19% 7% 3 6% 6% 3 4 4 5% 7% 36%	1800
	21st to end	Day	25% 8% 3 7% 5% 3 4 4 5% 5% 30%	1936
November	1st to 10th	Day	30% 9% 4 9% 6% 3 4 4 5% 6% 21%	1589
	11th to 20th	Day	30% 9% 4 8% 6% 3 5% 4 5% 5% 21%	1520
	21st to end	Day	26% 11% 4 8% 6% 4 4 4 5% 5% 24%	1520
December	1st to 10th	Day	26% 11% 4 7% 6% 3 4 4 5% 5% 26%	1520
	11th to 20th	Day	28% 9% 4 7% 6% 3 6% 5% 6% 8% 17%	1928
	21st to end	Day	30% 15% 4 8% 6% 4 4 5% 5% 5% 14%	2794
January	1st to 10th	Night	31% 18% 4 9% 7% 4 5% 4 3 4 12%	4406
	11th to 20th	Night	36% 13% 4 6% 5% 3 3 3 4 4 18%	4420
	21st to end	Night	34% 13% 4 8% 6% 3 4 3 4 5% 16%	4605
February	1st to 10th	Night	28% 13% 5% 7% 6% 3 6% 4 4 6% 18%	2470
	11th to 20th	Night	30% 13% 3 7% 4 3 4 3 5% 5% 24%	2402
	21st to end	Night	28% 15% 4 6% 6% 3 4 4 4 6% 21%	1954
March	1st to 10th	Night	23% 14% 4 7% 6% 2 5% 4 5% 6% 24%	2166
	11th to 20th	Night	25% 10% 4 6% 6% 4 5% 4 6% 8% 23%	1980
	21st to end	Night	26% 15% 5% 7% 6% 4 4 4 5% 6% 17%	2127
April	1st to 10th	Night	26% 16% 4 7% 5% 3 4 6% 4 5% 21%	1800
	11th to 20th	Night	22% 12% 4 7% 4 3 4 4 6% 6% 28%	1779
	21st to end	Night	26% 10% 4 6% 5% 2 4 4 5% 7% 27%	1641
May	1st to 10th	Night	21% 10% 4 5% 4 2 3 4 6% 6% 36%	1481
	11th to 20th	Night	21% 8% 3 5% 5% 3 5% 6% 4 7% 32%	1416
	21st to end	Night	22% 8% 3 6% 6% 3 5% 5% 6% 7% 29%	1552
June	1st to 10th	Night	20% 9% 3 5% 4 3 5% 5% 4 6% 36%	1440
	11th to 20th	Night	21% 10% 4 6% 6% 3 4 4 4 6% 33%	1440
	21st to end	Night	10% 6% 2 4 4 1 4 3 3 5% 57%	1440
July	1st to 10th	Night	7% 3 2 4 3 2 3 3 4 5% 65%	1440
	11th to 20th	Night	5% 3 1 3 3 2 2 3 4 5% 68%	1440
	21st to end	Night	2 1 1 2 1 2 2 3 4 4 78%	1576
August	1st to 10th	Night	3 3 1 2 3 2 2 3 5% 8% 69%	1584
	11th to 20th	Night	4 3 2 3 2 3 2 3 4 5% 69%	1602
	21st to end	Night	7% 3 2 4 3 2 3 3 3 6% 64%	1917
September	1st to 10th	Night	7% 4 2 3 3 1 2 3 4 4 67%	1800
	11th to 20th	Night	11% 5% 2 4 5% 3 5% 4 4 6% 52%	1800
	21st to end	Night	14% 5% 2 4 4 3 4 4 6% 6% 49%	2057
October	1st to 10th	Night	19% 6% 3 6% 4 2 3 3 4 4 45%	2160
	11th to 20th	Night	19% 6% 3 5% 4 3 3 4 5% 7% 40%	2160
	21st to end	Night	24% 9% 3 5% 5% 2 3 4 4 5% 36%	2418
November	1st to 10th	Night	30% 9% 3 7% 6% 3 4 5% 5% 6% 23%	2485
	11th to 20th	Night	32% 8% 3 7% 6% 3 4 5% 4 5% 23%	2660
	21st to end	Night	25% 11% 3 5% 5% 3 5% 5% 5% 5% 29%	2660
December	1st to 10th	Night	27% 9% 4 6% 5% 3 4 4 4 7% 27%	2660
	11th to 20th	Night	28% 12% 4 7% 6% 3 4 4 5% 7% 21%	3276
	21st to end	Night	26% 13% 5% 7% 6% 5% 5% 4 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	65% 5% 12% 13% 4 1	1953
	11th to 20th	Day	67% 4 9% 13% 6% 1	1980
	21st to end	Day	73% 6% 10% 10% 1	2227
April	1st to 10th	Day	69% 5% 12% 11% 4	2160
	11th to 20th	Day	63% 5% 11% 12% 6% 3	2132
	21st to end	Day	61% 6% 12% 12% 8% 2	2317
May	1st to 10th	Day	53% 5% 14% 19% 9% 1	2479
	11th to 20th	Day	56% 6% 13% 18% 6% 1	2480
	21st to end	Day	57% 7% 16% 18% 2	2724
June	1st to 10th	Day	54% 5% 16% 18% 5% 1	2520
	11th to 20th	Day	57% 6% 18% 15% 5%	2520
	21st to end	Day	33% 4 18% 30% 10% 5%	2520
July	1st to 10th	Day	24% 6% 15% 28% 23% 5%	2451
	11th to 20th	Day	21% 4 11% 26% 31% 7%	2445
	21st to end	Day	14% 3 8% 31% 37% 7%	2589
August	1st to 10th	Day	20% 6% 14% 34% 21% 5%	2334
	11th to 20th	Day	19% 4 14% 33% 23% 8%	2298
	21st to end	Day	25% 5% 12% 29% 24% 4	2437
September	1st to 10th	Day	22% 4 11% 29% 21% 12%	2160
	11th to 20th	Day	38% 7% 12% 21% 15% 8%	2160
	21st to end	Day	40% 5% 13% 19% 16% 7%	1898
October	1st to 10th	Day	44% 6% 10% 20% 15% 5%	1800
	11th to 20th	Day	49% 6% 13% 15% 14% 3	1800
	21st to end	Day	56% 6% 8% 14% 14% 2	1936
November	1st to 10th	Day	65% 5% 10% 14% 5% 1	1589
	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	62% 5% 12% 15% 6%	2166
	11th to 20th	Night	60% 7% 12% 13% 6% 2	1980
	21st to end	Night	68% 6% 13% 12% 1	2127
April	1st to 10th	Night	67% 6% 12% 11% 5%	1800
	11th to 20th	Night	58% 6% 15% 12% 6% 3	1779
	21st to end	Night	59% 5% 14% 13% 6% 3	1641
May	1st to 10th	Night	49% 6% 15% 20% 8% 2	1481
	11th to 20th	Night	52% 6% 16% 17% 5% 4	1416
	21st to end	Night	54% 8% 16% 18% 5%	1552
June	1st to 10th	Night	51% 6% 17% 21% 5%	1440
	11th to 20th	Night	54% 5% 18% 18% 5% 1	1440
	21st to end	Night	32% 4 20% 28% 11% 5%	1440
July	1st to 10th	Night	24% 5% 13% 29% 24% 7%	1400
	11th to 20th	Night	20% 4 11% 26% 31% 8%	1392
	21st to end	Night	10% 3 10% 33% 34% 10%	1488
August	1st to 10th	Night	15% 4 16% 39% 19% 6%	1576
	11th to 20th	Night	19% 3 14% 35% 21% 8%	1602
	21st to end	Night	23% 5% 11% 36% 20% 6%	1917
September	1st to 10th	Night	21% 4 13% 30% 21% 11%	1800
	11th to 20th	Night	33% 7% 11% 25% 13% 10%	1800
	21st to end	Night	35% 5% 15% 20% 16% 9%	2057
October	1st to 10th	Night	43% 4 9% 21% 17% 6%	2160
	11th to 20th	Night	44% 6% 11% 17% 17% 4	2160
	21st to end	Night	51% 6% 8% 14% 16% 4	2418
November	1st to 10th	Night	62% 5% 12% 11% 9% 1	2485
	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% 27% 21% 7% 1	449
	11th to 20th	Day	33% 9% 25% 20% 11% 2	420
	21st to end	Day	37% 11% 24% 21% 6%	462
April	1st to 10th	Day	38% 10% 20% 20% 10% 2	420
	11th to 20th	Day	35% 12% 24% 16% 9% 4	412
	21st to end	Day	30% 10% 27% 22% 10% 2	420
May	1st to 10th	Day	25% 9% 26% 25% 12% 3	423
	11th to 20th	Day	29% 9% 20% 24% 15% 3	448
	21st to end	Day	24% 3 22% 31% 16% 5%	485
June	1st to 10th	Day	24% 8% 19% 29% 16% 4	450
	11th to 20th	Day	25% 9% 28% 24% 13% 2	450
	21st to end	Day	9% 4 24% 39% 18% 6%	450
July	1st to 10th	Day	8% 3 21% 40% 24% 4	446
	11th to 20th	Day	5% 5% 21% 43% 22% 5%	444
	21st to end	Day	6% 2 16% 44% 25% 7%	487
August	1st to 10th	Day	5% 3 15% 44% 24% 8%	447
	11th to 20th	Day	5% 2 16% 38% 30% 8%	437
	21st to end	Day	7% 5% 22% 37% 23% 5%	495
September	1st to 10th	Day	9% 5% 25% 34% 22% 5%	450
	11th to 20th	Day	14% 6% 18% 34% 22% 5%	450
	21st to end	Day	21% 7% 20% 31% 17% 4	450
October	1st to 10th	Day	22% 8% 21% 23% 19% 7%	450
	11th to 20th	Day	24% 6% 17% 29% 17% 6%	450
	21st to end	Day	30% 8% 24% 20% 12% 6%	451
November	1st to 10th	Day	36% 11% 17% 24% 10% 3	230
	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	750
	11th to 20th	Night	30% 7% 17% 31% 14% 1	720
	21st to end	Night	36% 9% 17% 24% 12% 2	792
April	1st to 10th	Night	35% 8% 14% 27% 15% 1	720
	11th to 20th	Night	31% 7% 16% 28% 15% 3	711
	21st to end	Night	34% 5% 15% 30% 15% 2	561
May	1st to 10th	Night	26% 4 16% 31% 20% 2	401
	11th to 20th	Night	23% 5% 15% 28% 28% 1	354
	21st to end	Night	25% 4 13% 32% 23% 3	389
June	1st to 10th	Night	24% 4 13% 32% 24% 2	360
	11th to 20th	Night	28% 3 15% 34% 19% 1	360
	21st to end	Night	13% 3 14% 39% 30% 1	360
July	1st to 10th	Night	9% 2 8% 39% 40% 2	350
	11th to 20th	Night	7% 1 11% 46% 32% 3	348
	21st to end	Night	3 1 6% 45% 41% 5%	394
August	1st to 10th	Night	5% 2 5% 31% 48% 9%	510
	11th to 20th	Night	5% 2 6% 29% 49% 9%	534
	21st to end	Night	8% 3 11% 38% 35% 5%	729
September	1st to 10th	Night	10% 2 12% 39% 34% 4	720
	11th to 20th	Night	14% 2 8% 32% 37% 7%	720
	21st to end	Night	17% 3 12% 33% 30% 5%	720
October	1st to 10th	Night	21% 4 14% 29% 26% 5%	720
	11th to 20th	Night	23% 5% 11% 29% 27% 5%	720
	21st to end	Night	30% 5% 18% 26% 16% 5%	792
November	1st to 10th	Night	34% 6% 15% 30% 13% 1	740
	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 2024-03-05 04:24:04. Version ac07

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