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 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	18% 9% 3 7% 4 4 4 3 5% 7% 35%	153725
	Night	22% 11% 3 8% 5% 4 4 3 4 6% 31%	146100
Transparency	Day	48% 8% 15% 18% 8% 1	153439
	Night	54% 9% 13% 17% 6% 1	145968
Seeing	Day	24% 10% 19% 25% 16% 5%	17546
	Night	30% 9% 13% 25% 20% 4	25768

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	38% 17% 5% 8% 5% 4 4 3 4 3 8%	4125
	11th to 20th	Day	18% 11% 4 8% 5% 5% 5% 4 6% 9% 27%	4571
	21st to end	Day	25% 11% 4 8% 5% 5% 5% 3 5% 6% 22%	5283
February	1st to 10th	Day	30% 13% 4 9% 5% 4 4 3 5% 6% 16%	1890
	11th to 20th	Day	26% 13% 4 9% 5% 4 4 3 5% 5% 21%	1845
	21st to end	Day	27% 15% 3 9% 5% 4 4 4 6% 5% 19%	1620
March	1st to 10th	Day	20% 15% 4 9% 6% 5% 5% 4 5% 6% 20%	4708
	11th to 20th	Day	22% 13% 4 8% 5% 5% 5% 3 5% 6% 25%	5110
	21st to end	Day	25% 11% 4 10% 5% 6% 6% 4 6% 6% 15%	5801
April	1st to 10th	Day	23% 14% 3 8% 6% 5% 5% 4 6% 7% 20%	2520
	11th to 20th	Day	20% 11% 3 8% 6% 5% 5% 3 5% 7% 26%	2530
	21st to end	Day	20% 11% 4 7% 6% 4 5% 3 6% 6% 27%	2793
May	1st to 10th	Day	13% 8% 3 7% 4 4 4 4 5% 6% 42%	8195
	11th to 20th	Day	19% 10% 3 8% 5% 5% 5% 4 6% 8% 29%	8160
	21st to end	Day	22% 7% 3 6% 4 4 4 3 6% 9% 33%	8993
June	1st to 10th	Day	20% 8% 3 7% 5% 4 4 4 5% 7% 33%	3048
	11th to 20th	Day	18% 9% 3 7% 5% 5% 5% 4 6% 7% 30%	3150
	21st to end	Day	13% 7% 3 7% 5% 4 4 4 6% 7% 39%	3150
July	1st to 10th	Day	9% 4 2 4 3 3 3 3 4 6% 58%	8820
	11th to 20th	Day	5% 4 1 4 3 2 2 2 4 5% 67%	8581
	21st to end	Day	9% 4 2 5% 3 4 4 3 5% 7% 56%	8916
August	1st to 10th	Day	7% 3 1 3 2 3 3 3 4 7% 65%	6380
	11th to 20th	Day	8% 5% 2 7% 4 4 4 4 5% 8% 50%	5923
	21st to end	Day	14% 7% 3 7% 4 4 4 4 5% 8% 40%	6322
September	1st to 10th	Day	10% 7% 3 6% 4 3 4 3 5% 8% 48%	2520
	11th to 20th	Day	14% 8% 3 8% 4 4 5% 3 5% 5% 41%	2437
	21st to end	Day	18% 7% 3 7% 5% 4 3 4 6% 7% 37%	2114
October	1st to 10th	Day	18% 7% 3 8% 5% 4 5% 5% 6% 9% 31%	3280
	11th to 20th	Day	32% 10% 3 8% 5% 4 3 3 4 6% 24%	3261
	21st to end	Day	26% 12% 4 10% 6% 5% 5% 4 5% 6% 18%	3337
November	1st to 10th	Day	33% 10% 3 7% 5% 4 5% 4 5% 7% 17%	1678
	11th to 20th	Day	34% 10% 4 7% 4 4 4 4 4 6% 20%	1680
	21st to end	Day	33% 12% 4 6% 5% 3 5% 4 5% 7% 17%	1680
December	1st to 10th	Day	23% 11% 3 8% 6% 6% 6% 4 5% 7% 22%	2700
	11th to 20th	Day	32% 16% 5% 10% 6% 4 4 3 4 4 12%	3029
	21st to end	Day	30% 17% 6% 10% 5% 5% 5% 3 4 4 11%	3575
January	1st to 10th	Night	32% 16% 4 11% 6% 5% 4 3 4 4 10%	8770
	11th to 20th	Night	20% 12% 3 7% 4 4 5% 3 6% 8% 29%	8322
	21st to end	Night	24% 12% 3 8% 4 4 4 3 4 6% 27%	8898
February	1st to 10th	Night	29% 14% 4 8% 5% 4 4 3 4 5% 20%	2730
	11th to 20th	Night	25% 15% 3 9% 5% 4 4 3 4 5% 23%	2662
	21st to end	Night	27% 14% 3 8% 5% 5% 5% 4 4 5% 20%	2186
March	1st to 10th	Night	18% 15% 5% 11% 6% 6% 6% 4 6% 5% 18%	5390
	11th to 20th	Night	25% 14% 4 7% 4 4 4 3 4 5% 27%	5109
	21st to end	Night	30% 14% 4 9% 6% 5% 4 3 5% 5% 15%	5415
April	1st to 10th	Night	25% 11% 3 10% 5% 4 5% 5% 6% 7% 20%	2100
	11th to 20th	Night	21% 10% 3 9% 5% 5% 5% 3 5% 5% 27%	2038
	21st to end	Night	24% 11% 3 8% 7% 4 4 3 4 5% 27%	1827
May	1st to 10th	Night	14% 7% 2 7% 5% 4 4 3 4 5% 46%	4724
	11th to 20th	Night	22% 9% 3 8% 5% 5% 4 3 5% 5% 30%	4700
	21st to end	Night	19% 7% 3 7% 5% 5% 5% 4 6% 8% 32%	5178
June	1st to 10th	Night	20% 10% 2 6% 6% 5% 5% 3 5% 6% 31%	1568
	11th to 20th	Night	21% 9% 4 7% 5% 4 5% 5% 4 6% 29%	1470
	21st to end	Night	16% 7% 2 6% 4 4 3 4 6% 6% 41%	1470
July	1st to 10th	Night	12% 5% 2 6% 3 3 2 2 3 5% 57%	4140
	11th to 20th	Night	6% 3 1 3 2 2 2 3 3 5% 71%	4375
	21st to end	Night	7% 4 2 5% 3 3 4 3 5% 7% 57%	5152
August	1st to 10th	Night	7% 2 1 2 1 2 2 2 3 5% 73%	3769
	11th to 20th	Night	11% 5% 2 5% 3 3 3 3 4 7% 55%	4142
	21st to end	Night	18% 6% 2 6% 3 3 3 3 4 5% 47%	4837
September	1st to 10th	Night	9% 4 2 5% 3 4 4 4 5% 6% 53%	2100
	11th to 20th	Night	16% 8% 3 7% 5% 4 4 3 4 5% 41%	2030
	21st to end	Night	17% 7% 3 8% 4 4 3 4 4 5% 41%	2281
October	1st to 10th	Night	16% 7% 3 8% 5% 5% 5% 3 6% 8% 35%	3920
	11th to 20th	Night	28% 8% 3 6% 4 4 3 3 4 6% 31%	3897
	21st to end	Night	28% 14% 4 8% 4 4 4 3 4 6% 21%	4466
November	1st to 10th	Night	33% 11% 3 7% 5% 4 4 3 4 5% 20%	2840
	11th to 20th	Night	34% 13% 3 7% 4 3 4 4 4 5% 20%	2940
	21st to end	Night	32% 12% 3 7% 5% 4 4 3 4 5% 19%	2940
December	1st to 10th	Night	23% 11% 3 7% 6% 4 5% 4 6% 6% 25%	4700
	11th to 20th	Night	32% 15% 5% 10% 5% 4 5% 3 4 5% 13%	5391
	21st to end	Night	29% 18% 5% 11% 6% 5% 4 3 4 5% 11%	7623

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	80% 7% 6% 6% 2	4125
	11th to 20th	Day	51% 9% 11% 19% 9%	4595
	21st to end	Day	63% 5% 8% 16% 8%	5284
February	1st to 10th	Day	68% 9% 9% 8% 3 1	1890
	11th to 20th	Day	65% 9% 9% 9% 8%	1854
	21st to end	Day	65% 10% 11% 10% 5%	1620
March	1st to 10th	Day	61% 11% 12% 13% 3	4708
	11th to 20th	Day	59% 9% 13% 18% 2	5110
	21st to end	Day	66% 12% 12% 9% 1	5801
April	1st to 10th	Day	61% 13% 15% 10% 1	2520
	11th to 20th	Day	57% 10% 12% 13% 6% 1	2530
	21st to end	Day	58% 11% 12% 14% 5%	2793
May	1st to 10th	Day	42% 8% 16% 25% 9%	8195
	11th to 20th	Day	51% 12% 20% 15% 2	8163
	21st to end	Day	48% 9% 24% 16% 2	8994
June	1st to 10th	Day	51% 11% 17% 15% 6% 1	3048
	11th to 20th	Day	53% 12% 16% 15% 4	3150
	21st to end	Day	43% 12% 18% 20% 7% 1	3150
July	1st to 10th	Day	28% 7% 19% 21% 18% 7%	8746
	11th to 20th	Day	21% 5% 13% 31% 27% 3	8500
	21st to end	Day	27% 6% 24% 31% 11% 1	8723
August	1st to 10th	Day	21% 6% 16% 31% 24% 3	6363
	11th to 20th	Day	33% 8% 26% 28% 5% 1	5962
	21st to end	Day	41% 8% 16% 26% 8%	6321
September	1st to 10th	Day	36% 8% 17% 23% 12% 4	2520
	11th to 20th	Day	43% 10% 14% 18% 14% 1	2437
	21st to end	Day	45% 10% 18% 18% 8% 2	2114
October	1st to 10th	Day	47% 10% 18% 22% 4	3280
	11th to 20th	Day	62% 6% 12% 13% 7%	3261
	21st to end	Day	66% 7% 12% 9% 7%	3337
November	1st to 10th	Day	67% 9% 13% 8% 4	1678
	11th to 20th	Day	65% 9% 9% 9% 5% 2	1680
	21st to end	Day	67% 8% 9% 10% 6% 1	1680
December	1st to 10th	Day	60% 7% 10% 14% 9%	2700
	11th to 20th	Day	76% 8% 8% 7% 1	3032
	21st to end	Day	75% 9% 10% 4 1	3575
January	1st to 10th	Night	77% 9% 6% 6% 2	8770
	11th to 20th	Night	52% 10% 11% 20% 7%	8360
	21st to end	Night	59% 7% 8% 18% 8%	8898
February	1st to 10th	Night	67% 8% 10% 10% 5% 1	2730
	11th to 20th	Night	63% 8% 10% 11% 7% 1	2664
	21st to end	Night	63% 9% 11% 12% 4	2186
March	1st to 10th	Night	61% 11% 12% 11% 5%	5390
	11th to 20th	Night	58% 9% 14% 17% 2	5110
	21st to end	Night	70% 10% 11% 8% 1	5415
April	1st to 10th	Night	61% 12% 14% 11% 2	2100
	11th to 20th	Night	57% 9% 13% 12% 7% 1	2038
	21st to end	Night	58% 10% 13% 12% 6%	1827
May	1st to 10th	Night	40% 8% 13% 31% 8%	4721
	11th to 20th	Night	52% 11% 17% 16% 3	4700
	21st to end	Night	50% 11% 22% 15% 2	5182
June	1st to 10th	Night	53% 7% 18% 14% 6% 1	1568
	11th to 20th	Night	54% 10% 17% 15% 3	1470
	21st to end	Night	41% 9% 22% 20% 5% 3	1470
July	1st to 10th	Night	32% 6% 16% 23% 15% 8%	4105
	11th to 20th	Night	18% 6% 13% 29% 33% 2	4333
	21st to end	Night	27% 7% 21% 32% 11% 2	5040
August	1st to 10th	Night	16% 4 15% 41% 19% 4	3761
	11th to 20th	Night	29% 7% 30% 26% 7% 1	4169
	21st to end	Night	41% 7% 19% 26% 7% 1	4837
September	1st to 10th	Night	31% 8% 19% 27% 12% 4	2100
	11th to 20th	Night	45% 7% 12% 19% 14% 3	2030
	21st to end	Night	45% 8% 14% 23% 9% 1	2281
October	1st to 10th	Night	46% 9% 18% 23% 4	3920
	11th to 20th	Night	55% 7% 14% 18% 6%	3897
	21st to end	Night	64% 8% 12% 11% 5%	4466
November	1st to 10th	Night	67% 8% 11% 10% 3 1	2840
	11th to 20th	Night	67% 8% 9% 9% 4 2	2940
	21st to end	Night	66% 9% 9% 9% 6% 1	2940
December	1st to 10th	Night	59% 11% 9% 16% 5%	4700
	11th to 20th	Night	72% 9% 10% 7% 2	5387
	21st to end	Night	75% 10% 8% 5% 1	7623

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% 10% 16% 15% 10% 7%	220
	11th to 20th	Day	30% 15% 12% 18% 17% 8%	220
	21st to end	Day	39% 9% 16% 16% 15% 5%	274
February	1st to 10th	Day	40% 13% 16% 19% 10% 3	430
	11th to 20th	Day	37% 11% 19% 21% 9% 2	425
	21st to end	Day	36% 15% 19% 20% 9% 2	388
March	1st to 10th	Day	34% 14% 22% 18% 10% 2	540
	11th to 20th	Day	37% 14% 13% 18% 13% 5%	540
	21st to end	Day	32% 14% 25% 19% 9% 1	594
April	1st to 10th	Day	31% 12% 21% 21% 11% 4	540
	11th to 20th	Day	23% 15% 25% 21% 11% 5%	532
	21st to end	Day	25% 14% 20% 24% 13% 4	540
May	1st to 10th	Day	17% 11% 24% 29% 15% 3	543
	11th to 20th	Day	25% 9% 19% 24% 17% 6%	568
	21st to end	Day	23% 10% 21% 24% 16% 7%	617
June	1st to 10th	Day	20% 11% 22% 28% 15% 4	678
	11th to 20th	Day	19% 10% 28% 26% 14% 3	780
	21st to end	Day	13% 7% 24% 31% 20% 5%	780
July	1st to 10th	Day	12% 5% 21% 35% 23% 4	771
	11th to 20th	Day	8% 6% 20% 36% 23% 6%	685
	21st to end	Day	8% 4 16% 36% 25% 10%	619
August	1st to 10th	Day	12% 4 12% 35% 26% 11%	567
	11th to 20th	Day	8% 4 14% 33% 29% 12%	557
	21st to end	Day	14% 6% 20% 31% 21% 9%	627
September	1st to 10th	Day	14% 7% 19% 33% 20% 7%	570
	11th to 20th	Day	16% 9% 19% 30% 22% 5%	543
	21st to end	Day	22% 10% 20% 25% 17% 6%	530
October	1st to 10th	Day	23% 10% 19% 23% 18% 7%	530
	11th to 20th	Day	31% 10% 18% 19% 15% 6%	530
	21st to end	Day	35% 12% 18% 18% 12% 5%	450
November	1st to 10th	Day	41% 11% 21% 16% 9% 3	236
	11th to 20th	Day	39% 13% 11% 15% 12% 10%	220
	21st to end	Day	39% 9% 20% 13% 10% 10%	220
December	1st to 10th	Day	43% 12% 10% 9% 13% 13%	220
	11th to 20th	Day	49% 11% 15% 15% 9% 2	220
	21st to end	Day	45% 9% 13% 22% 8% 4	242
January	1st to 10th	Night	44% 12% 12% 18% 12% 2	950
	11th to 20th	Night	38% 10% 10% 20% 19% 2	865
	21st to end	Night	36% 8% 13% 23% 17% 3	924
February	1st to 10th	Night	38% 10% 12% 26% 12% 3	840
	11th to 20th	Night	33% 11% 13% 25% 17% 2	824
	21st to end	Night	37% 10% 14% 24% 12% 3	692
March	1st to 10th	Night	34% 14% 14% 22% 15% 2	840
	11th to 20th	Night	38% 12% 13% 21% 13% 3	840
	21st to end	Night	35% 13% 18% 22% 10% 1	924
April	1st to 10th	Night	30% 12% 14% 25% 17% 2	840
	11th to 20th	Night	26% 12% 18% 24% 16% 3	790
	21st to end	Night	29% 9% 16% 29% 14% 3	567
May	1st to 10th	Night	19% 9% 13% 35% 23% 3	420
	11th to 20th	Night	22% 6% 14% 27% 28% 4	414
	21st to end	Night	24% 6% 13% 27% 25% 5%	455
June	1st to 10th	Night	25% 4 15% 30% 23% 3	420
	11th to 20th	Night	23% 7% 13% 36% 19% 2	420
	21st to end	Night	18% 4 13% 35% 25% 5%	420
July	1st to 10th	Night	12% 3 10% 37% 34% 3	410
	11th to 20th	Night	8% 4 12% 38% 34% 4	408
	21st to end	Night	8% 2 9% 33% 41% 7%	460
August	1st to 10th	Night	12% 1 6% 30% 41% 12%	439
	11th to 20th	Night	10% 3 5% 24% 44% 14%	624
	21st to end	Night	14% 4 9% 30% 35% 7%	808
September	1st to 10th	Night	12% 3 10% 34% 33% 8%	840
	11th to 20th	Night	20% 6% 11% 22% 32% 10%	812
	21st to end	Night	24% 7% 11% 28% 24% 7%	800
October	1st to 10th	Night	21% 7% 12% 28% 25% 8%	800
	11th to 20th	Night	31% 7% 13% 23% 20% 6%	800
	21st to end	Night	33% 10% 14% 24% 14% 4	880
November	1st to 10th	Night	39% 12% 14% 24% 11% 1	820
	11th to 20th	Night	41% 11% 14% 18% 13% 3	840
	21st to end	Night	40% 8% 13% 20% 13% 5%	840
December	1st to 10th	Night	37% 8% 12% 22% 18% 5%	840
	11th to 20th	Night	45% 12% 13% 19% 11% 1	857
	21st to end	Night	42% 13% 16% 18% 10% 1	1045

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

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