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 2024-01-12.

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	10% 8% 3 6% 6% 3 5% 5% 5% 7% 43%	74759
	Night	12% 8% 3 6% 5% 3 5% 5% 5% 7% 41%	74984
Transparency	Day	41% 8% 12% 21% 14% 3	74462
	Night	44% 8% 13% 20% 12% 3	74802
Seeing	Day	22% 19% 30% 19% 9% 2	13406
	Night	22% 13% 25% 25% 13% 2	22511

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	21% 17% 5% 10% 8% 4 6% 5% 4 5% 15%	1519
	11th to 20th	Day	18% 13% 4 8% 9% 4 6% 6% 5% 7% 21%	1451
	21st to end	Day	14% 12% 4 9% 6% 4 7% 7% 6% 8% 23%	1652
February	1st to 10th	Day	13% 13% 4 8% 7% 4 7% 4 6% 7% 27%	1620
	11th to 20th	Day	14% 11% 3 6% 7% 5% 6% 6% 6% 7% 31%	1575
	21st to end	Day	13% 15% 6% 7% 7% 4 5% 6% 5% 7% 25%	1445
March	1st to 10th	Day	14% 15% 4 8% 7% 5% 7% 6% 5% 7% 21%	1815
	11th to 20th	Day	16% 13% 5% 8% 7% 4 6% 5% 5% 6% 25%	1980
	21st to end	Day	14% 14% 5% 8% 8% 5% 7% 6% 5% 6% 21%	2272
April	1st to 10th	Day	12% 12% 5% 9% 8% 4 6% 4 6% 8% 26%	2160
	11th to 20th	Day	10% 12% 4 7% 8% 5% 5% 5% 5% 6% 32%	2129
	21st to end	Day	6% 7% 3 7% 8% 5% 5% 5% 6% 10% 38%	2312
May	1st to 10th	Day	8% 5% 2 6% 7% 3 6% 6% 6% 8% 43%	2520
	11th to 20th	Day	9% 8% 4 6% 5% 4 6% 5% 8% 8% 37%	2477
	21st to end	Day	10% 6% 3 6% 6% 4 5% 6% 6% 8% 40%	2723
June	1st to 10th	Day	11% 6% 3 6% 6% 4 6% 5% 6% 7% 43%	2520
	11th to 20th	Day	6% 4 2 5% 5% 3 6% 5% 6% 8% 48%	2520
	21st to end	Day	3 3 2 4 5% 2 3 4 4 7% 63%	2520
July	1st to 10th	Day	1 2 1 2 3 1 3 3 4 6% 73%	2520
	11th to 20th	Day	3 2 1 2 2 2 4 3 3 5% 73%	2520
	21st to end	Day	2 1 1 1 1 1 1 2 2 3 83%	2741
August	1st to 10th	Day	2 1 1 2 2 2 3 3 4 5% 77%	2450
	11th to 20th	Day	3 2 1 2 2 2 2 4 3 6% 74%	2298
	21st to end	Day	2 2 1 3 4 3 3 4 5% 6% 67%	2408
September	1st to 10th	Day	3 2 1 2 2 2 3 3 4 6% 71%	2160
	11th to 20th	Day	5% 3 2 5% 4 3 4 5% 6% 8% 54%	2160
	21st to end	Day	9% 5% 1 5% 5% 4 4 4 4 7% 52%	1922
October	1st to 10th	Day	9% 7% 3 6% 4 3 4 5% 6% 7% 47%	1800
	11th to 20th	Day	14% 5% 2 6% 6% 4 5% 5% 5% 8% 41%	1800
	21st to end	Day	16% 8% 3 6% 6% 3 5% 5% 6% 5% 38%	1871
November	1st to 10th	Day	17% 11% 4 7% 7% 5% 6% 6% 6% 7% 26%	1617
	11th to 20th	Day	20% 13% 4 7% 8% 3 6% 4 5% 6% 22%	1520
	21st to end	Day	13% 12% 4 8% 6% 4 8% 5% 6% 7% 27%	1520
December	1st to 10th	Day	16% 12% 5% 9% 7% 3 5% 6% 3 4 30%	1520
	11th to 20th	Day	21% 16% 6% 8% 7% 4 6% 5% 5% 6% 16%	1928
	21st to end	Day	18% 14% 5% 11% 8% 4 6% 4 5% 5% 20%	2794
January	1st to 10th	Night	20% 17% 5% 9% 7% 3 6% 5% 5% 5% 17%	2646
	11th to 20th	Night	20% 11% 4 7% 6% 4 6% 6% 5% 8% 23%	2548
	21st to end	Night	15% 10% 4 6% 6% 4 7% 7% 7% 8% 27%	2704
February	1st to 10th	Night	13% 14% 4 7% 6% 4 6% 5% 6% 7% 28%	2340
	11th to 20th	Night	12% 11% 3 7% 6% 4 6% 5% 6% 7% 33%	2272
	21st to end	Night	11% 14% 4 8% 6% 4 7% 5% 6% 6% 28%	1810
March	1st to 10th	Night	13% 12% 5% 7% 7% 4 5% 5% 6% 7% 28%	2142
	11th to 20th	Night	14% 11% 3 6% 7% 4 6% 6% 6% 9% 28%	1980
	21st to end	Night	11% 12% 4 7% 8% 5% 6% 6% 5% 7% 27%	2084
April	1st to 10th	Night	12% 11% 4 6% 7% 4 5% 5% 6% 8% 32%	1800
	11th to 20th	Night	9% 8% 4 5% 4 4 5% 6% 6% 8% 41%	1779
	21st to end	Night	7% 7% 3 5% 7% 3 5% 6% 7% 9% 41%	1644
May	1st to 10th	Night	5% 5% 2 5% 6% 3 5% 5% 5% 6% 53%	1440
	11th to 20th	Night	8% 5% 2 4 5% 3 6% 6% 7% 9% 45%	1416
	21st to end	Night	4 5% 2 4 5% 4 5% 7% 8% 10% 46%	1552
June	1st to 10th	Night	8% 6% 3 4 6% 3 5% 5% 6% 8% 45%	1440
	11th to 20th	Night	6% 3 3 4 5% 3 4 5% 7% 8% 54%	1440
	21st to end	Night	3 2 2 3 4 2 4 3 4 7% 66%	1440
July	1st to 10th	Night	2 1 1 2 2 2 2 4 4 5% 75%	1440
	11th to 20th	Night	1 1 1 2 2 1 2 3 3 5% 79%	1440
	21st to end	Night	1 1 1 1 2 1 1 2 2 4 85%	1576
August	1st to 10th	Night	2 1 1 1 2 1 2 2 3 6% 78%	1486
	11th to 20th	Night	2 1 1 2 2 2 3 3 3 4 77%	1602
	21st to end	Night	2 2 1 2 2 1 2 3 4 6% 74%	1947
September	1st to 10th	Night	3 2 1 3 1 1 1 3 4 5% 76%	1800
	11th to 20th	Night	5% 3 2 3 4 4 4 5% 5% 6% 61%	1800
	21st to end	Night	7% 3 1 3 4 2 4 4 5% 7% 58%	2036
October	1st to 10th	Night	8% 5% 2 4 5% 3 4 4 5% 7% 54%	2160
	11th to 20th	Night	12% 6% 2 5% 4 3 4 4 6% 7% 47%	2160
	21st to end	Night	15% 7% 2 5% 5% 2 4 4 5% 6% 44%	2484
November	1st to 10th	Night	19% 9% 3 6% 6% 4 5% 5% 5% 7% 30%	2458
	11th to 20th	Night	20% 11% 3 7% 6% 4 6% 4 5% 6% 28%	2660
	21st to end	Night	13% 9% 3 6% 6% 4 6% 7% 6% 7% 33%	2660
December	1st to 10th	Night	17% 9% 3 7% 7% 3 6% 5% 5% 7% 30%	2660
	11th to 20th	Night	21% 14% 4 8% 7% 4 6% 6% 6% 6% 19%	3276
	21st to end	Night	18% 14% 7% 10% 7% 4 5% 4 5% 6% 20%	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	74% 8% 9% 7% 1	1519
	11th to 20th	Day	67% 7% 11% 10% 4 1	1451
	21st to end	Day	59% 11% 12% 12% 5%	1652
February	1st to 10th	Day	60% 10% 15% 12% 3	1620
	11th to 20th	Day	53% 11% 15% 17% 4 1	1584
	21st to end	Day	58% 9% 13% 11% 8% 1	1445
March	1st to 10th	Day	59% 9% 11% 15% 6%	1815
	11th to 20th	Day	59% 7% 11% 18% 5%	1980
	21st to end	Day	61% 10% 13% 13% 2	2272
April	1st to 10th	Day	55% 10% 12% 17% 5%	2160
	11th to 20th	Day	51% 7% 14% 17% 10% 2	2132
	21st to end	Day	42% 11% 16% 20% 10% 2	2312
May	1st to 10th	Day	37% 9% 15% 27% 12%	2520
	11th to 20th	Day	41% 8% 15% 25% 10% 1	2480
	21st to end	Day	40% 9% 19% 24% 7%	2724
June	1st to 10th	Day	40% 7% 15% 27% 10% 1	2520
	11th to 20th	Day	33% 9% 18% 30% 10% 1	2520
	21st to end	Day	22% 5% 16% 34% 18% 5%	2520
July	1st to 10th	Day	13% 6% 12% 29% 27% 12%	2451
	11th to 20th	Day	14% 4 9% 21% 37% 14%	2445
	21st to end	Day	8% 3 4 27% 43% 14%	2589
August	1st to 10th	Day	11% 5% 10% 31% 32% 11%	2433
	11th to 20th	Day	13% 4 10% 30% 32% 10%	2298
	21st to end	Day	18% 5% 11% 30% 32% 5%	2408
September	1st to 10th	Day	14% 5% 10% 31% 27% 12%	2160
	11th to 20th	Day	27% 7% 14% 23% 21% 8%	2160
	21st to end	Day	33% 5% 13% 26% 17% 5%	1922
October	1st to 10th	Day	36% 8% 13% 26% 15% 3	1800
	11th to 20th	Day	40% 7% 16% 22% 14% 1	1800
	21st to end	Day	48% 9% 10% 22% 11% 1	1871
November	1st to 10th	Day	57% 9% 12% 18% 4 1	1617
	11th to 20th	Day	64% 8% 12% 11% 3 1	1520
	21st to end	Day	57% 10% 10% 15% 7% 1	1520
December	1st to 10th	Day	62% 8% 10% 14% 5%	1520
	11th to 20th	Day	72% 9% 11% 6% 2	1928
	21st to end	Day	69% 8% 9% 11% 2	2794
January	1st to 10th	Night	70% 9% 10% 9% 1	2646
	11th to 20th	Night	64% 9% 12% 10% 4 1	2548
	21st to end	Night	57% 10% 15% 14% 3 1	2704
February	1st to 10th	Night	58% 8% 16% 15% 3	2340
	11th to 20th	Night	51% 11% 13% 18% 6% 1	2274
	21st to end	Night	56% 8% 13% 16% 7%	1810
March	1st to 10th	Night	53% 9% 14% 17% 6% 1	2142
	11th to 20th	Night	52% 8% 14% 20% 5% 1	1980
	21st to end	Night	56% 11% 14% 16% 3	2084
April	1st to 10th	Night	49% 10% 16% 17% 7% 1	1800
	11th to 20th	Night	41% 9% 17% 20% 9% 3	1779
	21st to end	Night	37% 12% 17% 23% 10% 1	1644
May	1st to 10th	Night	31% 7% 18% 29% 14% 1	1440
	11th to 20th	Night	33% 9% 20% 26% 10% 2	1416
	21st to end	Night	31% 11% 25% 24% 9% 1	1552
June	1st to 10th	Night	38% 7% 14% 30% 9% 2	1440
	11th to 20th	Night	28% 8% 20% 33% 11%	1440
	21st to end	Night	20% 5% 14% 37% 19% 5%	1440
July	1st to 10th	Night	13% 5% 14% 28% 28% 12%	1400
	11th to 20th	Night	10% 4 11% 24% 33% 18%	1392
	21st to end	Night	7% 2 6% 22% 44% 19%	1488
August	1st to 10th	Night	11% 3 12% 32% 32% 12%	1478
	11th to 20th	Night	12% 4 12% 29% 33% 10%	1602
	21st to end	Night	12% 5% 10% 33% 32% 8%	1947
September	1st to 10th	Night	13% 3 12% 30% 29% 12%	1800
	11th to 20th	Night	25% 8% 12% 25% 20% 11%	1800
	21st to end	Night	25% 7% 15% 27% 20% 6%	2036
October	1st to 10th	Night	31% 6% 12% 26% 23% 2	2160
	11th to 20th	Night	37% 7% 14% 24% 15% 3	2160
	21st to end	Night	42% 7% 10% 24% 16% 1	2484
November	1st to 10th	Night	52% 9% 12% 19% 8%	2458
	11th to 20th	Night	58% 9% 13% 14% 5% 1	2660
	21st to end	Night	51% 11% 13% 17% 7% 1	2660
December	1st to 10th	Night	58% 10% 12% 16% 4	2660
	11th to 20th	Night	68% 10% 11% 9% 2	3276
	21st to end	Night	67% 9% 9% 11% 3	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	39% 21% 24% 11% 5%	180
	11th to 20th	Day	36% 19% 27% 12% 6% 1	163
	21st to end	Day	32% 20% 23% 18% 8%	244
February	1st to 10th	Day	36% 24% 21% 16% 3	340
	11th to 20th	Day	40% 21% 24% 12% 2	335
	21st to end	Day	37% 20% 25% 14% 4	331
March	1st to 10th	Day	33% 20% 30% 12% 3	420
	11th to 20th	Day	31% 22% 27% 14% 6%	420
	21st to end	Day	34% 23% 27% 11% 4	462
April	1st to 10th	Day	35% 24% 22% 12% 5% 2	420
	11th to 20th	Day	32% 27% 22% 12% 5% 2	412
	21st to end	Day	26% 26% 28% 15% 5% 1	420
May	1st to 10th	Day	20% 23% 30% 17% 7% 2	423
	11th to 20th	Day	22% 18% 30% 15% 12% 3	448
	21st to end	Day	16% 21% 30% 21% 10% 2	485
June	1st to 10th	Day	20% 23% 25% 20% 10% 2	450
	11th to 20th	Day	23% 24% 33% 13% 7% 1	450
	21st to end	Day	8% 20% 36% 25% 10% 2	450
July	1st to 10th	Day	6% 13% 49% 24% 7% 1	446
	11th to 20th	Day	7% 14% 42% 24% 11% 2	444
	21st to end	Day	5% 13% 36% 28% 13% 4	487
August	1st to 10th	Day	5% 9% 38% 28% 15% 5%	447
	11th to 20th	Day	4 10% 37% 28% 17% 5%	437
	21st to end	Day	8% 17% 36% 23% 12% 3	495
September	1st to 10th	Day	6% 16% 33% 30% 11% 4	450
	11th to 20th	Day	13% 15% 33% 25% 12%	450
	21st to end	Day	18% 18% 28% 24% 11% 1	450
October	1st to 10th	Day	18% 19% 30% 19% 13% 2	450
	11th to 20th	Day	28% 16% 19% 22% 12% 3	450
	21st to end	Day	33% 18% 22% 17% 7% 3	386
November	1st to 10th	Day	33% 17% 30% 16% 4	243
	11th to 20th	Day	38% 19% 19% 14% 8% 2	180
	21st to end	Day	31% 18% 23% 20% 7%	180
December	1st to 10th	Day	34% 14% 20% 18% 10% 3	180
	11th to 20th	Day	39% 19% 28% 8% 5%	180
	21st to end	Day	32% 20% 26% 16% 5% 1	198
January	1st to 10th	Night	38% 13% 24% 15% 9% 1	760
	11th to 20th	Night	32% 11% 23% 21% 11% 1	728
	21st to end	Night	27% 10% 23% 28% 11% 2	792
February	1st to 10th	Night	32% 16% 22% 20% 9%	720
	11th to 20th	Night	30% 16% 21% 22% 11% 1	704
	21st to end	Night	31% 15% 25% 21% 8%	592
March	1st to 10th	Night	28% 16% 20% 23% 12% 1	720
	11th to 20th	Night	26% 16% 23% 25% 9% 1	720
	21st to end	Night	29% 16% 29% 17% 9% 1	792
April	1st to 10th	Night	27% 15% 27% 21% 8% 2	720
	11th to 20th	Night	20% 22% 24% 20% 11% 3	711
	21st to end	Night	16% 18% 30% 22% 12% 2	564
May	1st to 10th	Night	14% 13% 29% 27% 14% 2	360
	11th to 20th	Night	14% 11% 24% 31% 18% 3	354
	21st to end	Night	9% 11% 32% 27% 18% 3	389
June	1st to 10th	Night	17% 13% 25% 28% 16% 1	360
	11th to 20th	Night	11% 19% 31% 27% 13%	360
	21st to end	Night	6% 12% 30% 36% 14% 1	360
July	1st to 10th	Night	3 6% 36% 37% 17%	350
	11th to 20th	Night	3 7% 38% 36% 14% 1	348
	21st to end	Night	3 7% 27% 38% 22% 3	394
August	1st to 10th	Night	3 6% 26% 39% 23% 3	412
	11th to 20th	Night	4 4 22% 32% 29% 9%	534
	21st to end	Night	6% 11% 30% 31% 18% 4	759
September	1st to 10th	Night	7% 8% 27% 33% 21% 4	720
	11th to 20th	Night	9% 9% 25% 27% 24% 6%	720
	21st to end	Night	11% 13% 22% 29% 23% 3	720
October	1st to 10th	Night	17% 11% 23% 30% 16% 3	720
	11th to 20th	Night	22% 11% 19% 26% 17% 4	720
	21st to end	Night	27% 14% 22% 23% 12% 3	792
November	1st to 10th	Night	30% 11% 27% 25% 7%	740
	11th to 20th	Night	35% 13% 23% 18% 10% 1	760
	21st to end	Night	23% 14% 25% 24% 12% 1	760
December	1st to 10th	Night	28% 13% 26% 22% 11% 1	760
	11th to 20th	Night	35% 11% 24% 21% 8% 1	760
	21st to end	Night	39% 15% 25% 15% 6%	836

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