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 2026-04-02.

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% 9% 4 9% 6% 5% 6% 5% 6% 8% 34%	134537
	Night	6% 11% 5% 11% 7% 6% 6% 5% 7% 8% 30%	135923
Transparency	Day	46% 6% 16% 22% 8% 1	134191
	Night	51% 6% 14% 21% 8% 1	135849
Seeing	Day	13% 9% 24% 29% 20% 6%	19043
	Night	14% 9% 26% 31% 17% 3	26830

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	3 10% 8% 20% 8% 7% 7% 7% 6% 5% 19%	2847
	11th to 20th	Day	4 11% 4 9% 6% 5% 6% 7% 7% 8% 32%	3164
	21st to end	Day	3 12% 7% 16% 9% 8% 5% 4 6% 6% 24%	4090
February	1st to 10th	Day	4 13% 6% 13% 7% 8% 7% 4 7% 6% 26%	1470
	11th to 20th	Day	5% 12% 4 14% 7% 6% 6% 5% 5% 7% 29%	1635
	21st to end	Day	4 13% 7% 14% 7% 5% 6% 4 5% 7% 27%	1557
March	1st to 10th	Day	1 7% 6% 16% 7% 6% 6% 5% 7% 7% 32%	4476
	11th to 20th	Day	4 16% 7% 16% 8% 8% 7% 5% 6% 5% 19%	4923
	21st to end	Day	3 11% 4 7% 6% 4 5% 4 5% 8% 43%	5980
April	1st to 10th	Day	6% 14% 5% 11% 7% 5% 4 5% 5% 6% 30%	2463
	11th to 20th	Day	5% 12% 3 8% 6% 6% 5% 4 6% 7% 37%	2736
	21st to end	Day	9% 14% 5% 11% 6% 6% 6% 5% 6% 7% 27%	2800
May	1st to 10th	Day	5% 7% 2 7% 5% 5% 5% 5% 7% 9% 43%	7082
	11th to 20th	Day	8% 10% 3 9% 6% 6% 6% 5% 7% 9% 32%	7193
	21st to end	Day	9% 7% 3 7% 5% 5% 6% 5% 8% 9% 36%	8168
June	1st to 10th	Day	15% 10% 3 7% 5% 6% 5% 4 7% 8% 29%	3600
	11th to 20th	Day	15% 8% 3 7% 5% 6% 6% 5% 7% 8% 30%	3600
	21st to end	Day	11% 7% 2 7% 5% 5% 6% 5% 8% 9% 34%	3600
July	1st to 10th	Day	11% 6% 2 6% 4 5% 6% 5% 9% 12% 33%	8033
	11th to 20th	Day	11% 6% 2 7% 5% 5% 5% 4 7% 9% 39%	7686
	21st to end	Day	8% 6% 2 5% 5% 4 5% 5% 7% 10% 43%	7877
August	1st to 10th	Day	8% 5% 2 6% 4 4 4 4 6% 7% 49%	5019
	11th to 20th	Day	14% 7% 2 7% 5% 4 4 3 5% 7% 42%	4569
	21st to end	Day	15% 8% 3 8% 5% 6% 5% 4 5% 7% 32%	4966
September	1st to 10th	Day	14% 7% 3 8% 5% 4 5% 5% 6% 7% 37%	2455
	11th to 20th	Day	11% 10% 3 5% 5% 5% 5% 4 7% 10% 35%	2400
	21st to end	Day	14% 11% 3 8% 5% 4 5% 4 5% 7% 34%	2121
October	1st to 10th	Day	7% 11% 5% 9% 6% 5% 5% 3 5% 7% 37%	3280
	11th to 20th	Day	10% 17% 7% 10% 5% 3 4 3 6% 7% 29%	2919
	21st to end	Day	8% 15% 6% 14% 5% 6% 5% 4 5% 5% 26%	2842
November	1st to 10th	Day	9% 15% 5% 12% 7% 6% 6% 4 5% 6% 25%	1452
	11th to 20th	Day	7% 17% 7% 14% 9% 7% 5% 4 5% 5% 21%	1260
	21st to end	Day	6% 14% 5% 14% 7% 7% 6% 4 6% 8% 24%	1218
December	1st to 10th	Day	6% 13% 5% 16% 10% 8% 8% 5% 7% 5% 17%	1493
	11th to 20th	Day	2 10% 8% 17% 8% 8% 9% 5% 5% 5% 21%	1539
	21st to end	Day	5% 9% 4 11% 8% 7% 8% 5% 8% 7% 29%	2024
January	1st to 10th	Night	3 12% 7% 19% 9% 7% 7% 6% 7% 6% 19%	10041
	11th to 20th	Night	3 8% 4 9% 7% 7% 7% 6% 9% 9% 31%	9720
	21st to end	Night	3 12% 6% 16% 8% 6% 5% 4 6% 8% 26%	10147
February	1st to 10th	Night	3 11% 6% 13% 8% 8% 6% 6% 6% 7% 26%	3150
	11th to 20th	Night	4 14% 4 12% 8% 5% 5% 4 7% 7% 30%	2868
	21st to end	Night	5% 14% 5% 13% 9% 6% 6% 5% 7% 5% 25%	2249
March	1st to 10th	Night	2 8% 4 13% 6% 5% 6% 6% 10% 9% 31%	5632
	11th to 20th	Night	5% 13% 7% 18% 10% 7% 6% 4 5% 7% 18%	5294
	21st to end	Night	2 8% 4 10% 7% 5% 5% 4 6% 8% 40%	5237
April	1st to 10th	Night	5% 15% 4 9% 6% 4 5% 5% 7% 7% 31%	1958
	11th to 20th	Night	5% 11% 3 9% 6% 6% 5% 5% 6% 8% 35%	1613
	21st to end	Night	9% 18% 4 10% 6% 7% 5% 4 6% 6% 25%	1600
May	1st to 10th	Night	4 7% 3 7% 5% 5% 6% 4 5% 8% 46%	2875
	11th to 20th	Night	8% 9% 4 7% 4 6% 6% 5% 8% 11% 32%	2702
	21st to end	Night	9% 6% 2 8% 5% 6% 6% 5% 9% 10% 32%	2704
June	1st to 10th	Night	15% 10% 3 6% 5% 4 5% 3 7% 9% 32%	800
	11th to 20th	Night	13% 8% 2 8% 4 4 7% 5% 7% 8% 36%	800
	21st to end	Night	10% 6% 2 6% 5% 5% 5% 5% 9% 10% 39%	800
July	1st to 10th	Night	10% 6% 2 7% 5% 4 6% 4 9% 13% 36%	1924
	11th to 20th	Night	9% 6% 4 7% 4 5% 5% 5% 8% 10% 38%	2260
	21st to end	Night	7% 4 2 5% 4 6% 6% 5% 7% 10% 44%	2966
August	1st to 10th	Night	8% 5% 2 5% 3 4 4 3 5% 6% 54%	2116
	11th to 20th	Night	12% 4 2 6% 4 4 4 4 7% 9% 43%	2477
	21st to end	Night	13% 8% 3 7% 5% 5% 6% 5% 8% 9% 32%	2933
September	1st to 10th	Night	12% 8% 3 7% 5% 4 5% 4 6% 8% 37%	1945
	11th to 20th	Night	13% 9% 2 7% 5% 4 5% 5% 8% 9% 33%	2000
	21st to end	Night	14% 11% 3 8% 4 5% 5% 4 6% 7% 32%	2276
October	1st to 10th	Night	9% 8% 4 9% 4 5% 5% 5% 7% 10% 35%	3920
	11th to 20th	Night	11% 16% 5% 9% 5% 4 4 3 5% 7% 33%	4225
	21st to end	Night	7% 17% 5% 11% 4 5% 5% 4 6% 6% 30%	4948
November	1st to 10th	Night	11% 17% 6% 13% 8% 5% 4 3 3 5% 25%	3044
	11th to 20th	Night	7% 19% 7% 14% 8% 6% 5% 3 4 5% 21%	3360
	21st to end	Night	6% 14% 5% 10% 7% 6% 5% 5% 6% 7% 28%	3402
December	1st to 10th	Night	4 14% 7% 15% 10% 8% 6% 4 6% 6% 20%	5890
	11th to 20th	Night	3 13% 7% 16% 8% 6% 6% 6% 7% 5% 24%	6873
	21st to end	Night	3 9% 4 10% 7% 7% 8% 6% 7% 8% 31%	9174

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	64% 5% 12% 12% 7%	2847
	11th to 20th	Day	47% 5% 11% 22% 14% 1	3180
	21st to end	Day	60% 4 16% 13% 6%	4091
February	1st to 10th	Day	57% 6% 9% 19% 10% 1	1470
	11th to 20th	Day	54% 6% 15% 17% 8%	1643
	21st to end	Day	56% 5% 14% 19% 6%	1557
March	1st to 10th	Day	49% 4 11% 23% 13%	4476
	11th to 20th	Day	64% 6% 9% 15% 6%	4923
	21st to end	Day	38% 5% 16% 28% 12% 1	5980
April	1st to 10th	Day	53% 5% 13% 19% 9% 1	2463
	11th to 20th	Day	44% 5% 12% 27% 11% 1	2736
	21st to end	Day	54% 7% 14% 18% 7%	2800
May	1st to 10th	Day	35% 7% 12% 25% 15% 6%	7082
	11th to 20th	Day	44% 8% 14% 20% 14%	7197
	21st to end	Day	41% 7% 13% 24% 14% 1	8169
June	1st to 10th	Day	49% 7% 13% 23% 7%	3600
	11th to 20th	Day	48% 8% 15% 22% 6%	3600
	21st to end	Day	43% 8% 20% 22% 7%	3600
July	1st to 10th	Day	40% 8% 22% 27% 3	7946
	11th to 20th	Day	40% 8% 25% 23% 4	7593
	21st to end	Day	34% 7% 25% 31% 3	7656
August	1st to 10th	Day	33% 7% 18% 28% 15%	5000
	11th to 20th	Day	42% 6% 17% 21% 13%	4613
	21st to end	Day	50% 6% 22% 19% 3	4965
September	1st to 10th	Day	45% 8% 21% 22% 5%	2455
	11th to 20th	Day	44% 6% 25% 23% 3	2400
	21st to end	Day	50% 6% 18% 21% 5%	2121
October	1st to 10th	Day	47% 4 16% 29% 4	3280
	11th to 20th	Day	56% 5% 15% 20% 4	2919
	21st to end	Day	59% 6% 15% 16% 4	2842
November	1st to 10th	Day	60% 5% 11% 20% 4	1452
	11th to 20th	Day	65% 4 13% 11% 5%	1260
	21st to end	Day	56% 7% 13% 17% 7%	1218
December	1st to 10th	Day	67% 7% 12% 11% 3	1493
	11th to 20th	Day	64% 5% 10% 17% 4	1540
	21st to end	Day	51% 6% 17% 17% 8%	2024
January	1st to 10th	Night	63% 5% 9% 14% 9%	10042
	11th to 20th	Night	46% 6% 15% 19% 14% 1	9766
	21st to end	Night	56% 5% 14% 17% 7%	10147
February	1st to 10th	Night	55% 5% 10% 20% 10%	3150
	11th to 20th	Night	51% 6% 13% 21% 9% 1	2870
	21st to end	Night	57% 5% 9% 21% 7%	2249
March	1st to 10th	Night	43% 6% 11% 27% 13%	5632
	11th to 20th	Night	65% 5% 8% 15% 6%	5295
	21st to end	Night	39% 6% 15% 27% 12% 1	5237
April	1st to 10th	Night	48% 6% 15% 22% 9%	1958
	11th to 20th	Night	46% 5% 10% 26% 12% 1	1613
	21st to end	Night	56% 7% 11% 18% 7% 1	1600
May	1st to 10th	Night	34% 6% 14% 21% 19% 5%	2873
	11th to 20th	Night	41% 8% 15% 22% 14%	2702
	21st to end	Night	39% 9% 17% 23% 11% 1	2704
June	1st to 10th	Night	47% 6% 13% 28% 5% 1	800
	11th to 20th	Night	44% 7% 19% 21% 10%	800
	21st to end	Night	37% 9% 21% 22% 10%	800
July	1st to 10th	Night	37% 9% 26% 26% 2	1902
	11th to 20th	Night	38% 8% 27% 24% 3	2230
	21st to end	Night	32% 6% 26% 31% 5%	2882
August	1st to 10th	Night	32% 6% 16% 32% 15%	2110
	11th to 20th	Night	35% 8% 17% 27% 13%	2499
	21st to end	Night	46% 8% 21% 23% 3	2933
September	1st to 10th	Night	44% 6% 21% 23% 5%	1945
	11th to 20th	Night	45% 7% 21% 23% 4	2000
	21st to end	Night	51% 6% 14% 22% 6%	2276
October	1st to 10th	Night	43% 5% 18% 25% 7%	3920
	11th to 20th	Night	51% 4 14% 25% 5%	4225
	21st to end	Night	53% 5% 18% 21% 3	4948
November	1st to 10th	Night	63% 4 10% 17% 5%	3044
	11th to 20th	Night	66% 4 11% 14% 5% 1	3360
	21st to end	Night	54% 6% 13% 19% 7% 1	3402
December	1st to 10th	Night	64% 5% 12% 13% 6%	5890
	11th to 20th	Night	59% 4 10% 19% 6% 1	6871
	21st to end	Night	48% 7% 16% 19% 10% 1	9174

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	7% 9% 26% 33% 23% 2	220
	11th to 20th	Day	16% 13% 29% 22% 15% 5%	220
	21st to end	Day	12% 14% 30% 25% 17% 2	242
February	1st to 10th	Day	10% 11% 35% 25% 16% 3	220
	11th to 20th	Day	8% 8% 34% 30% 16% 4	231
	21st to end	Day	12% 9% 30% 31% 15% 3	355
March	1st to 10th	Day	4 9% 29% 32% 19% 7%	505
	11th to 20th	Day	8% 11% 29% 25% 20% 6%	540
	21st to end	Day	9% 9% 25% 34% 18% 5%	594
April	1st to 10th	Day	11% 11% 28% 31% 14% 4	505
	11th to 20th	Day	11% 6% 27% 28% 20% 8%	492
	21st to end	Day	16% 14% 22% 28% 16% 4	500
May	1st to 10th	Day	12% 11% 31% 28% 14% 4	823
	11th to 20th	Day	13% 9% 22% 31% 19% 5%	922
	21st to end	Day	14% 7% 23% 30% 23% 4	1006
June	1st to 10th	Day	18% 8% 22% 28% 19% 5%	930
	11th to 20th	Day	17% 7% 16% 31% 21% 7%	930
	21st to end	Day	12% 6% 17% 27% 27% 10%	930
July	1st to 10th	Day	15% 4 17% 28% 26% 9%	916
	11th to 20th	Day	13% 5% 19% 25% 29% 11%	912
	21st to end	Day	14% 5% 13% 31% 28% 9%	1013
August	1st to 10th	Day	11% 6% 14% 28% 29% 11%	824
	11th to 20th	Day	19% 8% 26% 27% 17% 4	580
	21st to end	Day	18% 7% 22% 32% 16% 4	583
September	1st to 10th	Day	18% 8% 25% 26% 18% 5%	530
	11th to 20th	Day	13% 8% 29% 31% 16% 3	530
	21st to end	Day	17% 16% 33% 20% 11% 3	530
October	1st to 10th	Day	17% 12% 35% 23% 9% 4	530
	11th to 20th	Day	19% 12% 30% 27% 9% 3	346
	21st to end	Day	14% 11% 31% 25% 12% 6%	242
November	1st to 10th	Day	10% 8% 38% 30% 11% 3	220
	11th to 20th	Day	11% 12% 26% 35% 13% 3	220
	21st to end	Day	15% 15% 27% 25% 15% 4	220
December	1st to 10th	Day	10% 15% 29% 27% 15% 5%	220
	11th to 20th	Day	7% 10% 30% 33% 15% 6%	220
	21st to end	Day	9% 6% 26% 36% 17% 6%	242
January	1st to 10th	Night	10% 9% 26% 34% 17% 4	1160
	11th to 20th	Night	14% 13% 28% 29% 14% 3	1160
	21st to end	Night	13% 13% 31% 29% 12% 1	1220
February	1st to 10th	Night	8% 10% 30% 34% 15% 3	950
	11th to 20th	Night	10% 12% 31% 33% 14% 2	832
	21st to end	Night	12% 8% 26% 34% 15% 4	692
March	1st to 10th	Night	7% 7% 29% 31% 22% 4	840
	11th to 20th	Night	11% 10% 24% 32% 20% 3	840
	21st to end	Night	9% 5% 21% 37% 22% 5%	924
April	1st to 10th	Night	12% 8% 24% 36% 19% 2	752
	11th to 20th	Night	12% 6% 22% 34% 23% 3	425
	21st to end	Night	20% 7% 23% 30% 18% 2	400
May	1st to 10th	Night	11% 9% 28% 34% 16% 1	400
	11th to 20th	Night	13% 9% 23% 31% 24% 1	394
	21st to end	Night	15% 4 21% 34% 25% 1	433
June	1st to 10th	Night	18% 5% 23% 30% 22% 3	400
	11th to 20th	Night	16% 5% 16% 35% 26% 2	400
	21st to end	Night	12% 4 18% 29% 32% 5%	400
July	1st to 10th	Night	17% 4 17% 32% 26% 5%	390
	11th to 20th	Night	12% 3 18% 33% 30% 5%	388
	21st to end	Night	14% 4 17% 32% 28% 6%	438
August	1st to 10th	Night	9% 5% 13% 33% 32% 8%	398
	11th to 20th	Night	19% 5% 24% 32% 16% 5%	396
	21st to end	Night	19% 5% 18% 36% 18% 4	465
September	1st to 10th	Night	17% 7% 24% 29% 21% 3	745
	11th to 20th	Night	17% 7% 27% 32% 13% 3	800
	21st to end	Night	20% 10% 28% 30% 11% 1	800
October	1st to 10th	Night	19% 10% 32% 25% 13% 1	800
	11th to 20th	Night	21% 9% 33% 25% 11% 1	800
	21st to end	Night	18% 9% 27% 29% 13% 3	880
November	1st to 10th	Night	17% 12% 30% 28% 11% 3	992
	11th to 20th	Night	16% 9% 31% 29% 14% 2	1160
	21st to end	Night	13% 11% 27% 30% 15% 4	1160
December	1st to 10th	Night	11% 13% 31% 30% 14% 2	1160
	11th to 20th	Night	12% 10% 27% 33% 15% 3	1160
	21st to end	Night	10% 7% 26% 31% 21% 5%	1276

Page generated at 2026-03-30 00:18:38. Version ac07

Copyright © 2026 Attilla Danko.