Trout Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Trout Lake clear sky chart from 2005-11-06 to 2025-11-18.

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	8% 8% 2 6% 4 4 4 3 5% 6% 48%	136091
	Night	11% 9% 3 6% 4 4 4 4 5% 7% 44%	131593
Transparency	Day	37% 7% 11% 23% 16% 6%	130816
	Night	41% 8% 12% 22% 13% 4	127869
Seeing	Day	21% 19% 30% 19% 8% 2	15816
	Night	21% 13% 26% 25% 13% 2	24769

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	18% 21% 6% 9% 7% 5% 4 4 5% 7% 13%	3639
	11th to 20th	Day	13% 14% 3 6% 4 4 4 3 4 5% 40%	3640
	21st to end	Day	22% 13% 3 7% 4 3 4 3 4 5% 32%	4170
February	1st to 10th	Day	12% 15% 4 9% 6% 6% 6% 4 6% 7% 26%	1800
	11th to 20th	Day	14% 13% 3 7% 6% 6% 4 4 6% 7% 29%	1755
	21st to end	Day	12% 18% 5% 8% 6% 5% 4 4 5% 8% 25%	1612
March	1st to 10th	Day	9% 13% 4 8% 6% 6% 7% 5% 6% 8% 29%	4559
	11th to 20th	Day	11% 14% 3 7% 4 5% 5% 3 5% 5% 36%	5000
	21st to end	Day	13% 15% 4 9% 7% 7% 7% 5% 7% 7% 20%	5722
April	1st to 10th	Day	11% 13% 4 9% 6% 6% 6% 4 6% 8% 27%	2400
	11th to 20th	Day	9% 12% 3 7% 7% 5% 4 4 5% 6% 36%	2369
	21st to end	Day	6% 8% 3 8% 7% 6% 5% 4 6% 9% 38%	2570
May	1st to 10th	Day	8% 5% 2 5% 4 4 5% 3 5% 7% 53%	6320
	11th to 20th	Day	5% 5% 2 5% 4 4 5% 4 7% 8% 52%	6277
	21st to end	Day	6% 5% 2 5% 4 5% 5% 4 6% 8% 49%	6902
June	1st to 10th	Day	10% 6% 2 6% 5% 5% 5% 4 6% 7% 45%	2800
	11th to 20th	Day	6% 5% 2 6% 4 5% 5% 4 6% 8% 49%	2800
	21st to end	Day	3 3 2 5% 4 3 3 3 5% 6% 63%	2800
July	1st to 10th	Day	1 1 1 2 1 1 1 1 3 4 83%	6319
	11th to 20th	Day	1 1 1 1 1 2 2 2 2 3 84%	6320
	21st to end	Day	2 1 1 2 2 1 2 2 3 5% 79%	6880
August	1st to 10th	Day	2 2 1 3 2 2 3 3 4 5% 72%	6064
	11th to 20th	Day	2 2 1 4 2 3 3 3 5% 6% 69%	5796
	21st to end	Day	4 4 2 4 4 4 4 3 5% 7% 60%	6055
September	1st to 10th	Day	3 2 1 2 2 3 3 3 5% 7% 70%	2400
	11th to 20th	Day	5% 3 2 5% 4 4 4 4 5% 7% 57%	2400
	21st to end	Day	9% 5% 1 5% 4 5% 4 3 4 7% 54%	2134
October	1st to 10th	Day	5% 5% 2 5% 3 3 3 3 6% 8% 57%	3280
	11th to 20th	Day	9% 5% 2 7% 5% 5% 6% 5% 7% 8% 41%	3261
	21st to end	Day	15% 9% 2 6% 5% 5% 6% 4 6% 7% 34%	3348
November	1st to 10th	Day	17% 12% 3 7% 6% 6% 5% 5% 7% 6% 26%	1791
	11th to 20th	Day	19% 15% 4 9% 7% 5% 5% 4 5% 6% 21%	1656
	21st to end	Day	13% 14% 3 9% 6% 6% 7% 5% 6% 7% 27%	1600
December	1st to 10th	Day	12% 8% 3 9% 6% 4 4 4 3 6% 41%	2620
	11th to 20th	Day	23% 17% 5% 10% 6% 6% 5% 4 6% 5% 14%	3028
	21st to end	Day	18% 16% 4 12% 6% 6% 5% 4 6% 5% 16%	4004
January	1st to 10th	Night	20% 21% 5% 10% 7% 5% 5% 4 5% 7% 13%	6306
	11th to 20th	Night	14% 11% 3 7% 4 4 3 3 4 7% 39%	6320
	21st to end	Night	20% 13% 3 6% 4 4 4 3 4 6% 34%	6780
February	1st to 10th	Night	13% 15% 4 8% 5% 5% 6% 4 5% 7% 28%	2600
	11th to 20th	Night	12% 13% 3 7% 5% 5% 5% 5% 6% 7% 32%	2532
	21st to end	Night	12% 15% 4 9% 5% 6% 6% 4 6% 6% 28%	2017
March	1st to 10th	Night	7% 11% 4 8% 6% 6% 6% 6% 7% 8% 30%	5332
	11th to 20th	Night	11% 15% 3 6% 4 4 5% 4 5% 6% 37%	5000
	21st to end	Night	12% 14% 3 9% 7% 6% 6% 5% 6% 8% 24%	5253
April	1st to 10th	Night	11% 11% 3 7% 7% 5% 5% 4 7% 8% 33%	2000
	11th to 20th	Night	8% 8% 3 6% 4 5% 5% 5% 6% 7% 43%	1979
	21st to end	Night	6% 7% 2 6% 6% 4 5% 5% 8% 9% 41%	1826
May	1st to 10th	Night	8% 5% 2 5% 3 3 3 3 4 5% 59%	3640
	11th to 20th	Night	4 4 1 4 3 4 5% 4 6% 7% 58%	3616
	21st to end	Night	5% 6% 1 3 3 4 5% 5% 8% 10% 50%	3972
June	1st to 10th	Night	8% 7% 3 6% 5% 4 4 3 6% 8% 46%	1600
	11th to 20th	Night	5% 4 2 4 4 4 4 4 6% 8% 56%	1600
	21st to end	Night	3 2 2 4 3 3 4 3 5% 6% 66%	1600
July	1st to 10th	Night	1 1 1 1 1 2 3 4 4 82%	3640
	11th to 20th	Night	1 1 1 1 1 1 2 1 2 3 85%	3640
	21st to end	Night	1 1 1 1 1 1 1 3 6% 83%	3970
August	1st to 10th	Night	1 2 1 3 2 2 3 3 4 6% 73%	3732
	11th to 20th	Night	4 2 1 3 2 3 3 3 5% 5% 71%	4052
	21st to end	Night	3 3 1 4 3 3 4 3 5% 6% 65%	4940
September	1st to 10th	Night	3 2 1 3 1 2 2 3 4 5% 74%	2000
	11th to 20th	Night	4 3 1 4 3 4 4 4 5% 6% 62%	2000
	21st to end	Night	7% 3 1 4 3 3 4 3 5% 7% 59%	2264
October	1st to 10th	Night	5% 3 2 3 3 3 4 3 5% 7% 62%	3920
	11th to 20th	Night	8% 5% 2 5% 4 4 5% 4 8% 9% 45%	3897
	21st to end	Night	14% 8% 2 7% 4 4 5% 4 7% 7% 38%	4455
November	1st to 10th	Night	19% 10% 2 7% 5% 6% 5% 5% 6% 7% 29%	2724
	11th to 20th	Night	20% 12% 3 8% 5% 6% 5% 3 5% 6% 27%	2898
	21st to end	Night	13% 10% 2 7% 6% 6% 6% 5% 6% 7% 33%	2800
December	1st to 10th	Night	11% 7% 2 7% 6% 5% 4 4 6% 8% 41%	4560
	11th to 20th	Night	26% 15% 4 10% 6% 6% 5% 4 5% 5% 14%	5176
	21st to end	Night	23% 14% 5% 10% 6% 5% 5% 3 5% 6% 18%	6952

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	73% 13% 7% 5% 1	3639
	11th to 20th	Day	49% 6% 14% 23% 7% 1	3640
	21st to end	Day	57% 7% 6% 19% 12%	4170
February	1st to 10th	Day	59% 10% 14% 13% 4	1800
	11th to 20th	Day	54% 11% 14% 16% 5%	1764
	21st to end	Day	58% 8% 13% 11% 8% 1	1612
March	1st to 10th	Day	49% 10% 9% 18% 13% 1	4559
	11th to 20th	Day	50% 7% 9% 27% 7%	5000
	21st to end	Day	59% 11% 14% 12% 3	5722
April	1st to 10th	Day	54% 10% 13% 18% 5%	2400
	11th to 20th	Day	47% 7% 14% 19% 11% 2	2372
	21st to end	Day	41% 11% 15% 22% 9% 1	2570
May	1st to 10th	Day	32% 7% 9% 28% 23% 2	6320
	11th to 20th	Day	28% 10% 16% 31% 15% 1	6280
	21st to end	Day	32% 9% 20% 30% 8%	6904
June	1st to 10th	Day	38% 7% 15% 26% 12% 2	2800
	11th to 20th	Day	31% 9% 16% 30% 13% 1	2800
	21st to end	Day	22% 5% 16% 34% 18% 5%	2800
July	1st to 10th	Day	8% 3 6% 24% 30% 29%	6251
	11th to 20th	Day	9% 2 4 15% 35% 35%	6245
	21st to end	Day	10% 3 7% 34% 33% 12%	6681
August	1st to 10th	Day	13% 4 6% 22% 35% 20%	4412
	11th to 20th	Day	16% 5% 10% 41% 21% 6%	4195
	21st to end	Day	23% 5% 10% 25% 33% 5%	4358
September	1st to 10th	Day	15% 5% 11% 31% 27% 11%	2400
	11th to 20th	Day	26% 7% 13% 26% 20% 7%	2400
	21st to end	Day	31% 5% 13% 28% 18% 5%	2134
October	1st to 10th	Day	26% 7% 11% 33% 22% 2	3280
	11th to 20th	Day	38% 9% 17% 22% 13% 1	3261
	21st to end	Day	48% 10% 10% 22% 9% 1	3348
November	1st to 10th	Day	56% 9% 13% 17% 4 1	1791
	11th to 20th	Day	65% 9% 11% 11% 3 1	1656
	21st to end	Day	57% 10% 11% 14% 7% 1	1600
December	1st to 10th	Day	46% 9% 15% 24% 6%	2620
	11th to 20th	Day	74% 9% 9% 7% 1	3028
	21st to end	Day	70% 11% 9% 10% 1	4004
January	1st to 10th	Night	74% 12% 7% 5% 1	6306
	11th to 20th	Night	48% 9% 15% 22% 6%	6320
	21st to end	Night	55% 7% 8% 19% 10%	6780
February	1st to 10th	Night	57% 8% 16% 15% 3 1	2600
	11th to 20th	Night	52% 11% 12% 18% 6% 1	2534
	21st to end	Night	56% 8% 12% 16% 7%	2017
March	1st to 10th	Night	47% 9% 12% 21% 10% 1	5332
	11th to 20th	Night	48% 8% 12% 25% 6%	5000
	21st to end	Night	56% 12% 15% 16% 2	5253
April	1st to 10th	Night	47% 10% 17% 18% 6% 1	2000
	11th to 20th	Night	39% 9% 17% 21% 11% 2	1979
	21st to end	Night	36% 12% 16% 24% 10% 1	1826
May	1st to 10th	Night	29% 6% 8% 28% 28% 1	3637
	11th to 20th	Night	23% 11% 18% 34% 13% 2	3616
	21st to end	Night	26% 12% 26% 28% 7%	3972
June	1st to 10th	Night	37% 6% 14% 31% 10% 3	1600
	11th to 20th	Night	26% 7% 18% 33% 15% 1	1600
	21st to end	Night	20% 5% 15% 36% 19% 5%	1600
July	1st to 10th	Night	8% 3 8% 22% 32% 27%	3600
	11th to 20th	Night	8% 2 6% 14% 36% 34%	3592
	21st to end	Night	7% 2 8% 34% 32% 16%	3857
August	1st to 10th	Night	11% 3 7% 22% 37% 20%	2714
	11th to 20th	Night	13% 4 14% 41% 21% 7%	2929
	21st to end	Night	17% 5% 12% 28% 31% 7%	3559
September	1st to 10th	Night	15% 3 12% 30% 29% 12%	2000
	11th to 20th	Night	24% 7% 12% 28% 20% 10%	2000
	21st to end	Night	24% 7% 15% 29% 20% 6%	2264
October	1st to 10th	Night	23% 6% 8% 38% 23% 1	3920
	11th to 20th	Night	34% 8% 19% 26% 13% 1	3897
	21st to end	Night	44% 9% 9% 25% 11% 1	4455
November	1st to 10th	Night	53% 10% 13% 18% 7%	2724
	11th to 20th	Night	60% 8% 12% 13% 5% 1	2898
	21st to end	Night	51% 11% 14% 17% 7% 1	2800
December	1st to 10th	Night	42% 11% 14% 29% 4	4560
	11th to 20th	Night	73% 10% 9% 7% 1	5176
	21st to end	Night	68% 10% 9% 10% 2	6952

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% 21% 26% 11% 5%	200
	11th to 20th	Day	35% 19% 26% 14% 6% 1	200
	21st to end	Day	34% 20% 21% 17% 8%	295
February	1st to 10th	Day	34% 26% 22% 15% 3 1	400
	11th to 20th	Day	38% 24% 24% 12% 3	395
	21st to end	Day	38% 19% 26% 13% 4	396
March	1st to 10th	Day	32% 20% 32% 13% 3	500
	11th to 20th	Day	29% 24% 27% 14% 6% 1	500
	21st to end	Day	33% 25% 27% 11% 3	550
April	1st to 10th	Day	32% 26% 23% 11% 6% 2	500
	11th to 20th	Day	28% 28% 24% 12% 5% 2	492
	21st to end	Day	24% 26% 28% 15% 6% 1	500
May	1st to 10th	Day	21% 23% 29% 18% 7% 2	503
	11th to 20th	Day	23% 19% 30% 15% 11% 3	528
	21st to end	Day	16% 21% 30% 20% 10% 2	573
June	1st to 10th	Day	20% 22% 26% 20% 10% 2	530
	11th to 20th	Day	23% 24% 34% 13% 6% 1	530
	21st to end	Day	9% 19% 35% 25% 9% 2	530
July	1st to 10th	Day	6% 14% 47% 24% 8% 2	526
	11th to 20th	Day	6% 13% 43% 26% 10% 2	524
	21st to end	Day	5% 13% 36% 28% 13% 4	575
August	1st to 10th	Day	5% 9% 38% 28% 15% 5%	527
	11th to 20th	Day	4 12% 37% 28% 15% 5%	517
	21st to end	Day	9% 16% 35% 25% 13% 4	583
September	1st to 10th	Day	5% 14% 32% 32% 13% 4	530
	11th to 20th	Day	12% 15% 34% 28% 10% 1	530
	21st to end	Day	17% 17% 28% 25% 11% 1	530
October	1st to 10th	Day	18% 19% 31% 19% 12% 1	530
	11th to 20th	Day	28% 17% 21% 21% 11% 3	530
	21st to end	Day	31% 21% 23% 16% 6% 3	461
November	1st to 10th	Day	35% 19% 27% 16% 3	297
	11th to 20th	Day	39% 20% 19% 14% 7% 2	214
	21st to end	Day	31% 17% 26% 19% 8%	200
December	1st to 10th	Day	33% 13% 19% 21% 12% 3	200
	11th to 20th	Day	40% 20% 28% 8% 5%	200
	21st to end	Day	34% 21% 24% 15% 5% 1	220
January	1st to 10th	Night	37% 14% 24% 16% 9% 1	800
	11th to 20th	Night	31% 12% 24% 21% 11% 1	800
	21st to end	Night	28% 10% 23% 27% 11% 2	880
February	1st to 10th	Night	31% 16% 23% 21% 8%	800
	11th to 20th	Night	30% 17% 21% 22% 10% 1	784
	21st to end	Night	32% 15% 25% 21% 7%	660
March	1st to 10th	Night	27% 16% 23% 23% 11% 1	800
	11th to 20th	Night	25% 17% 23% 24% 9% 1	800
	21st to end	Night	29% 16% 30% 17% 8% 1	880
April	1st to 10th	Night	26% 16% 28% 22% 8% 2	800
	11th to 20th	Night	19% 23% 25% 19% 11% 3	791
	21st to end	Night	16% 19% 31% 21% 11% 1	626
May	1st to 10th	Night	15% 14% 29% 27% 14% 2	400
	11th to 20th	Night	13% 14% 24% 30% 16% 2	394
	21st to end	Night	9% 12% 31% 28% 17% 3	433
June	1st to 10th	Night	18% 13% 25% 28% 15% 1	400
	11th to 20th	Night	11% 20% 33% 25% 11%	400
	21st to end	Night	6% 12% 33% 35% 13% 1	400
July	1st to 10th	Night	3 8% 37% 36% 16%	390
	11th to 20th	Night	3 8% 38% 37% 13% 1	388
	21st to end	Night	3 7% 31% 36% 20% 3	438
August	1st to 10th	Night	3 6% 28% 39% 21% 3	459
	11th to 20th	Night	4 6% 25% 31% 26% 8%	594
	21st to end	Night	7% 11% 29% 32% 18% 3	844
September	1st to 10th	Night	6% 8% 28% 35% 20% 3	800
	11th to 20th	Night	9% 10% 27% 27% 22% 6%	800
	21st to end	Night	11% 13% 22% 29% 23% 3	800
October	1st to 10th	Night	16% 12% 23% 31% 15% 3	800
	11th to 20th	Night	21% 13% 21% 25% 16% 4	800
	21st to end	Night	25% 14% 24% 23% 11% 3	880
November	1st to 10th	Night	31% 12% 25% 24% 7%	820
	11th to 20th	Night	35% 14% 23% 17% 10% 1	828
	21st to end	Night	23% 14% 25% 25% 12% 1	800
December	1st to 10th	Night	28% 12% 25% 22% 12% 1	800
	11th to 20th	Night	35% 12% 24% 21% 8% 1	800
	21st to end	Night	39% 15% 25% 15% 6%	880

Page generated at 2025-11-14 21:56:01. Version ac07

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