Lake Goodwin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Goodwin clear sky chart from 2005-11-06 to 2025-05-11.

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	20% 10% 3 7% 5% 4 4 3 5% 6% 32%	117689
	Night	23% 11% 3 8% 5% 4 4 3 4 6% 29%	119966
Transparency	Day	52% 9% 13% 17% 8% 1	117444
	Night	56% 9% 12% 15% 6% 1	119857
Seeing	Day	24% 10% 19% 25% 17% 6%	15713
	Night	30% 9% 13% 25% 20% 4	24212

By Month

Percentage Cloud Cover NW (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	35% 18% 5% 9% 5% 4 4 3 4 4 9%	3179
	11th to 20th	Day	18% 12% 3 8% 6% 5% 5% 4 6% 7% 25%	3499
	21st to end	Day	27% 12% 3 7% 5% 5% 5% 4 4 5% 22%	4073
February	1st to 10th	Day	30% 14% 4 10% 5% 4 4 4 5% 6% 16%	1800
	11th to 20th	Day	27% 14% 4 10% 5% 4 4 3 5% 5% 21%	1755
	21st to end	Day	28% 15% 3 9% 5% 4 4 3 5% 5% 19%	1545
March	1st to 10th	Day	20% 16% 4 9% 6% 5% 5% 4 5% 6% 20%	4606
	11th to 20th	Day	21% 13% 4 8% 5% 5% 5% 3 5% 6% 25%	5000
	21st to end	Day	25% 12% 4 10% 6% 6% 6% 4 6% 6% 15%	5676
April	1st to 10th	Day	23% 14% 4 9% 6% 5% 4 4 6% 7% 19%	2400
	11th to 20th	Day	20% 11% 3 8% 6% 5% 5% 3 5% 6% 27%	2408
	21st to end	Day	20% 11% 4 7% 6% 5% 5% 3 6% 6% 26%	2660
May	1st to 10th	Day	18% 8% 2 6% 4 4 3 3 5% 6% 39%	4560
	11th to 20th	Day	15% 6% 3 6% 4 4 5% 4 6% 9% 39%	4380
	21st to end	Day	28% 9% 3 8% 5% 4 4 3 5% 6% 25%	4813
June	1st to 10th	Day	21% 8% 3 7% 5% 4 5% 4 5% 7% 31%	2758
	11th to 20th	Day	20% 10% 3 8% 5% 5% 5% 4 6% 7% 28%	2850
	21st to end	Day	12% 7% 3 7% 5% 4 4 4 6% 7% 41%	2850
July	1st to 10th	Day	6% 4 2 4 3 2 2 2 3 4 67%	4740
	11th to 20th	Day	5% 3 1 3 3 2 2 3 3 5% 69%	4613
	21st to end	Day	12% 4 2 4 3 3 3 2 4 5% 58%	4790
August	1st to 10th	Day	5% 3 1 3 2 3 3 3 4 8% 64%	4354
	11th to 20th	Day	11% 6% 2 7% 4 4 5% 4 5% 8% 44%	4026
	21st to end	Day	14% 8% 3 7% 5% 4 3 3 3 6% 43%	4345
September	1st to 10th	Day	10% 7% 3 5% 4 4 4 2 5% 7% 50%	2280
	11th to 20th	Day	14% 8% 3 8% 4 4 5% 4 5% 6% 40%	2280
	21st to end	Day	18% 7% 3 7% 5% 4 3 4 6% 6% 37%	2008
October	1st to 10th	Day	18% 7% 3 8% 5% 4 5% 5% 6% 9% 31%	3180
	11th to 20th	Day	32% 10% 3 8% 5% 3 3 3 4 6% 24%	3161
	21st to end	Day	25% 12% 4 10% 6% 5% 5% 4 5% 6% 19%	3234
November	1st to 10th	Day	34% 10% 4 7% 5% 4 5% 4 5% 6% 16%	1597
	11th to 20th	Day	33% 10% 4 7% 4 5% 4 4 4 6% 21%	1600
	21st to end	Day	33% 12% 4 6% 5% 3 5% 4 5% 7% 17%	1600
December	1st to 10th	Day	22% 10% 3 7% 6% 6% 6% 4 6% 7% 22%	2620
	11th to 20th	Day	32% 16% 5% 10% 7% 4 4 3 4 4 12%	2951
	21st to end	Day	30% 17% 6% 10% 5% 5% 5% 3 4 4 11%	3498
January	1st to 10th	Night	32% 15% 4 11% 6% 4 4 3 4 4 11%	6766
	11th to 20th	Night	20% 11% 3 7% 4 4 5% 3 6% 9% 27%	6394
	21st to end	Night	25% 12% 3 8% 4 4 4 3 4 5% 27%	6882
February	1st to 10th	Night	30% 14% 4 7% 5% 4 4 3 4 5% 20%	2600
	11th to 20th	Night	26% 15% 4 9% 5% 4 4 3 4 5% 23%	2532
	21st to end	Night	28% 13% 3 8% 5% 4 5% 4 5% 5% 20%	2085
March	1st to 10th	Night	18% 15% 5% 11% 6% 6% 6% 4 6% 5% 18%	5272
	11th to 20th	Night	24% 14% 4 7% 4 4 4 3 4 5% 28%	4999
	21st to end	Night	30% 14% 4 9% 6% 5% 4 4 5% 4 15%	5298
April	1st to 10th	Night	25% 11% 3 10% 5% 4 5% 5% 6% 7% 19%	2000
	11th to 20th	Night	21% 10% 3 9% 5% 5% 4 4 5% 5% 28%	1940
	21st to end	Night	24% 11% 3 8% 7% 5% 4 3 4 5% 25%	1740
May	1st to 10th	Night	18% 8% 2 6% 4 3 3 3 4 4 44%	2620
	11th to 20th	Night	15% 7% 3 6% 5% 5% 3 3 5% 6% 43%	2519
	21st to end	Night	28% 9% 3 7% 5% 4 4 3 4 6% 26%	2762
June	1st to 10th	Night	20% 10% 2 6% 6% 4 5% 3 5% 7% 31%	1419
	11th to 20th	Night	23% 10% 4 8% 5% 4 5% 4 5% 5% 27%	1330
	21st to end	Night	14% 7% 2 6% 4 4 3 5% 6% 7% 42%	1330
July	1st to 10th	Night	8% 4 2 4 3 2 2 2 3 4 67%	2220
	11th to 20th	Night	5% 3 1 3 2 2 2 2 3 5% 73%	2343
	21st to end	Night	12% 4 1 4 3 3 3 3 5% 5% 57%	2762
August	1st to 10th	Night	5% 2 1 2 2 2 3 3 4 7% 69%	2574
	11th to 20th	Night	14% 6% 2 6% 3 3 3 3 4 6% 51%	2812
	21st to end	Night	17% 6% 2 6% 3 3 3 3 4 5% 48%	3328
September	1st to 10th	Night	9% 4 2 5% 3 4 4 3 5% 6% 55%	1900
	11th to 20th	Night	16% 8% 3 7% 4 4 4 3 4 5% 40%	1900
	21st to end	Night	17% 7% 3 8% 4 4 3 4 4 6% 41%	2167
October	1st to 10th	Night	16% 7% 3 8% 5% 5% 5% 3 6% 8% 35%	3800
	11th to 20th	Night	28% 8% 3 6% 4 4 3 3 4 6% 30%	3777
	21st to end	Night	29% 14% 4 8% 4 4 4 3 4 6% 21%	4327
November	1st to 10th	Night	33% 11% 3 7% 5% 4 4 3 4 5% 20%	2701
	11th to 20th	Night	33% 13% 3 7% 4 3 4 4 4 5% 21%	2800
	21st to end	Night	32% 12% 3 7% 5% 4 4 4 4 5% 19%	2800
December	1st to 10th	Night	22% 11% 3 7% 6% 4 5% 4 6% 6% 25%	4560
	11th to 20th	Night	31% 15% 5% 10% 5% 4 5% 3 4 5% 14%	5249
	21st to end	Night	29% 18% 5% 11% 6% 5% 4 3 4 4 10%	7458

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	3179
	11th to 20th	Day	54% 10% 13% 17% 6% 1	3523
	21st to end	Day	64% 6% 9% 14% 8%	4073
February	1st to 10th	Day	69% 10% 9% 8% 3 1	1800
	11th to 20th	Day	66% 9% 9% 8% 8% 1	1764
	21st to end	Day	66% 10% 10% 10% 4	1545
March	1st to 10th	Day	61% 11% 12% 13% 3	4606
	11th to 20th	Day	59% 9% 13% 18% 2	5000
	21st to end	Day	67% 12% 12% 9% 1	5676
April	1st to 10th	Day	63% 13% 14% 9% 1	2400
	11th to 20th	Day	57% 10% 12% 13% 7% 1	2408
	21st to end	Day	59% 11% 12% 13% 5%	2660
May	1st to 10th	Day	44% 11% 13% 23% 9%	4560
	11th to 20th	Day	38% 15% 24% 19% 4	4383
	21st to end	Day	61% 12% 17% 9% 1	4814
June	1st to 10th	Day	52% 11% 18% 13% 6% 1	2758
	11th to 20th	Day	56% 12% 16% 12% 3	2850
	21st to end	Day	41% 12% 19% 20% 7% 1	2850
July	1st to 10th	Day	22% 7% 11% 23% 24% 13%	4666
	11th to 20th	Day	19% 6% 10% 31% 31% 4	4532
	21st to end	Day	29% 6% 19% 31% 14% 2	4639
August	1st to 10th	Day	20% 8% 16% 37% 19% 1	4337
	11th to 20th	Day	38% 9% 21% 24% 6% 2	4065
	21st to end	Day	42% 8% 12% 26% 11% 1	4344
September	1st to 10th	Day	35% 8% 16% 24% 13% 4	2280
	11th to 20th	Day	44% 10% 14% 17% 15% 1	2280
	21st to end	Day	45% 10% 18% 17% 8% 2	2008
October	1st to 10th	Day	47% 10% 18% 22% 4	3180
	11th to 20th	Day	62% 6% 12% 12% 7%	3161
	21st to end	Day	66% 7% 12% 9% 7%	3234
November	1st to 10th	Day	67% 9% 12% 7% 4	1597
	11th to 20th	Day	65% 10% 9% 9% 6% 2	1600
	21st to end	Day	66% 8% 9% 10% 6% 1	1600
December	1st to 10th	Day	59% 8% 10% 14% 9%	2620
	11th to 20th	Day	75% 8% 8% 7% 1	2954
	21st to end	Day	76% 9% 10% 4 1	3498
January	1st to 10th	Night	75% 10% 7% 6% 2	6766
	11th to 20th	Night	52% 11% 13% 19% 5%	6432
	21st to end	Night	60% 7% 10% 16% 8%	6882
February	1st to 10th	Night	67% 7% 10% 10% 5% 1	2600
	11th to 20th	Night	64% 8% 10% 10% 6% 1	2534
	21st to end	Night	63% 9% 11% 12% 4	2085
March	1st to 10th	Night	61% 11% 12% 11% 5%	5272
	11th to 20th	Night	57% 9% 15% 18% 2	5000
	21st to end	Night	70% 10% 11% 8% 1	5298
April	1st to 10th	Night	62% 13% 14% 11% 2	2000
	11th to 20th	Night	56% 9% 13% 12% 8% 2	1940
	21st to end	Night	59% 10% 13% 12% 5% 1	1740
May	1st to 10th	Night	41% 10% 13% 26% 8% 1	2620
	11th to 20th	Night	37% 14% 24% 20% 5%	2519
	21st to end	Night	60% 14% 16% 10% 1	2762
June	1st to 10th	Night	53% 8% 19% 14% 5% 1	1419
	11th to 20th	Night	57% 11% 17% 13% 2	1330
	21st to end	Night	40% 9% 23% 19% 5% 3	1330
July	1st to 10th	Night	23% 5% 10% 25% 21% 15%	2185
	11th to 20th	Night	16% 5% 10% 28% 39% 2	2301
	21st to end	Night	30% 7% 13% 29% 18% 3	2674
August	1st to 10th	Night	17% 5% 15% 41% 19% 2	2566
	11th to 20th	Night	35% 7% 23% 24% 9% 2	2839
	21st to end	Night	40% 7% 16% 27% 10%	3328
September	1st to 10th	Night	30% 8% 17% 27% 13% 4	1900
	11th to 20th	Night	46% 7% 11% 18% 14% 3	1900
	21st to end	Night	45% 8% 14% 22% 9% 1	2167
October	1st to 10th	Night	45% 9% 18% 23% 4	3800
	11th to 20th	Night	55% 7% 15% 18% 5%	3777
	21st to end	Night	64% 8% 11% 11% 5%	4327
November	1st to 10th	Night	67% 8% 11% 10% 3 1	2701
	11th to 20th	Night	66% 8% 10% 10% 4 2	2800
	21st to end	Night	66% 9% 9% 9% 6% 1	2800
December	1st to 10th	Night	58% 11% 9% 17% 5%	4560
	11th to 20th	Night	72% 9% 10% 7% 2	5245
	21st to end	Night	75% 10% 8% 5% 2	7458

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% 11% 16% 16% 12% 8%	200
	11th to 20th	Day	32% 16% 12% 18% 16% 7%	200
	21st to end	Day	41% 9% 16% 15% 14% 5%	250
February	1st to 10th	Day	40% 13% 16% 18% 10% 3	400
	11th to 20th	Day	39% 11% 18% 21% 10% 2	395
	21st to end	Day	36% 14% 19% 20% 9% 2	361
March	1st to 10th	Day	32% 14% 23% 18% 11% 2	500
	11th to 20th	Day	33% 14% 13% 20% 14% 5%	500
	21st to end	Day	32% 14% 24% 18% 9% 1	550
April	1st to 10th	Day	32% 13% 21% 21% 11% 4	500
	11th to 20th	Day	23% 15% 26% 21% 11% 5%	492
	21st to end	Day	26% 14% 19% 24% 13% 4	500
May	1st to 10th	Day	17% 12% 24% 30% 15% 3	503
	11th to 20th	Day	22% 8% 19% 25% 19% 6%	489
	21st to end	Day	24% 11% 19% 24% 16% 7%	529
June	1st to 10th	Day	21% 10% 23% 28% 15% 3	588
	11th to 20th	Day	21% 10% 27% 25% 14% 3	680
	21st to end	Day	12% 7% 24% 31% 21% 5%	680
July	1st to 10th	Day	12% 5% 20% 35% 25% 4	671
	11th to 20th	Day	8% 6% 18% 36% 25% 7%	593
	21st to end	Day	9% 3 15% 36% 27% 10%	531
August	1st to 10th	Day	12% 3 11% 36% 27% 11%	487
	11th to 20th	Day	7% 4 14% 34% 28% 13%	477
	21st to end	Day	14% 6% 21% 30% 21% 9%	539
September	1st to 10th	Day	15% 7% 19% 35% 19% 6%	490
	11th to 20th	Day	16% 9% 19% 30% 22% 5%	490
	21st to end	Day	22% 10% 20% 26% 17% 6%	490
October	1st to 10th	Day	24% 9% 18% 24% 18% 7%	490
	11th to 20th	Day	31% 10% 17% 20% 16% 6%	490
	21st to end	Day	34% 11% 18% 20% 12% 5%	413
November	1st to 10th	Day	40% 11% 20% 16% 10% 3	215
	11th to 20th	Day	38% 13% 11% 16% 12% 11%	200
	21st to end	Day	37% 9% 20% 13% 10% 12%	200
December	1st to 10th	Day	42% 11% 10% 10% 15% 15%	200
	11th to 20th	Day	47% 13% 13% 16% 10% 2	200
	21st to end	Day	45% 10% 13% 23% 8% 2	220
January	1st to 10th	Night	44% 11% 11% 19% 12% 2	900
	11th to 20th	Night	38% 11% 10% 20% 18% 2	823
	21st to end	Night	37% 8% 13% 23% 16% 4	880
February	1st to 10th	Night	39% 9% 12% 26% 12% 3	800
	11th to 20th	Night	34% 11% 12% 25% 16% 2	784
	21st to end	Night	37% 9% 14% 24% 13% 3	660
March	1st to 10th	Night	33% 14% 14% 22% 15% 2	800
	11th to 20th	Night	36% 13% 13% 21% 14% 3	800
	21st to end	Night	36% 13% 17% 22% 10% 1	880
April	1st to 10th	Night	31% 12% 14% 25% 16% 2	800
	11th to 20th	Night	26% 11% 18% 25% 15% 3	752
	21st to end	Night	30% 9% 15% 28% 14% 3	540
May	1st to 10th	Night	19% 9% 14% 34% 22% 3	400
	11th to 20th	Night	21% 4 15% 26% 30% 4	375
	21st to end	Night	25% 6% 12% 26% 26% 6%	411
June	1st to 10th	Night	25% 5% 15% 29% 23% 3	380
	11th to 20th	Night	26% 7% 13% 34% 18% 2	380
	21st to end	Night	17% 3 13% 36% 26% 5%	380
July	1st to 10th	Night	12% 4 9% 35% 36% 4	370
	11th to 20th	Night	8% 4 11% 36% 36% 5%	368
	21st to end	Night	9% 2 8% 33% 41% 7%	416
August	1st to 10th	Night	12% 1 6% 26% 43% 13%	397
	11th to 20th	Night	10% 2 5% 23% 45% 15%	564
	21st to end	Night	14% 4 9% 29% 36% 8%	731
September	1st to 10th	Night	13% 3 9% 34% 32% 9%	760
	11th to 20th	Night	20% 6% 10% 21% 32% 10%	760
	21st to end	Night	24% 7% 11% 27% 25% 7%	760
October	1st to 10th	Night	22% 6% 11% 28% 26% 8%	760
	11th to 20th	Night	31% 8% 13% 22% 21% 6%	760
	21st to end	Night	33% 10% 14% 24% 15% 4	836
November	1st to 10th	Night	39% 11% 14% 23% 12% 1	780
	11th to 20th	Night	41% 11% 15% 17% 13% 3	800
	21st to end	Night	39% 8% 13% 20% 14% 5%	800
December	1st to 10th	Night	35% 8% 12% 22% 18% 5%	800
	11th to 20th	Night	43% 11% 13% 20% 11% 1	815
	21st to end	Night	43% 13% 16% 18% 9% 1	990

Page generated at 2025-05-08 06:33:54. Version ac07

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