Lac la Biche
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac la Biche clear sky chart from 2005-11-06 to 2026-07-01.

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% 9% 3 9% 6% 5% 5% 5% 7% 8% 34%	142341
	Night	8% 10% 4 10% 6% 6% 6% 4 6% 8% 32%	138609
Transparency	Day	46% 9% 17% 22% 7%	142037
	Night	48% 8% 16% 20% 7% 1	138498
Seeing	Day	14% 11% 29% 28% 14% 4	18154
	Night	13% 8% 30% 33% 14% 2	26670

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	6% 15% 6% 14% 9% 7% 7% 4 6% 6% 21%	4125
	11th to 20th	Day	4 9% 4 11% 6% 6% 7% 6% 8% 9% 30%	4119
	21st to end	Day	5% 11% 6% 13% 10% 6% 5% 4 6% 7% 26%	4531
February	1st to 10th	Day	6% 13% 5% 12% 7% 6% 6% 6% 9% 7% 24%	1680
	11th to 20th	Day	6% 10% 4 11% 8% 7% 6% 5% 7% 8% 29%	1809
	21st to end	Day	4 14% 4 10% 9% 8% 7% 5% 8% 9% 23%	1557
March	1st to 10th	Day	4 9% 5% 10% 7% 7% 7% 6% 8% 9% 28%	4608
	11th to 20th	Day	5% 10% 4 10% 7% 6% 6% 5% 7% 10% 30%	5109
	21st to end	Day	10% 16% 5% 13% 5% 4 4 3 5% 7% 27%	5607
April	1st to 10th	Day	8% 12% 4 9% 6% 5% 6% 4 7% 8% 31%	2670
	11th to 20th	Day	11% 12% 4 8% 6% 6% 6% 5% 6% 7% 31%	2700
	21st to end	Day	13% 10% 3 9% 6% 5% 5% 4 7% 8% 30%	2790
May	1st to 10th	Day	9% 6% 2 7% 5% 6% 6% 5% 7% 8% 39%	8656
	11th to 20th	Day	17% 11% 3 8% 5% 5% 5% 4 6% 7% 28%	8755
	21st to end	Day	10% 7% 2 7% 6% 5% 6% 5% 7% 9% 36%	9649
June	1st to 10th	Day	15% 8% 3 7% 6% 5% 5% 5% 7% 7% 32%	3271
	11th to 20th	Day	18% 9% 3 9% 6% 6% 6% 5% 7% 7% 25%	3506
	21st to end	Day	11% 6% 2 8% 5% 6% 6% 5% 7% 9% 34%	3556
July	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 10% 42%	7021
	11th to 20th	Day	8% 4 2 6% 4 5% 5% 4 7% 9% 45%	6780
	21st to end	Day	12% 5% 2 5% 4 4 5% 4 7% 9% 42%	7376
August	1st to 10th	Day	12% 7% 3 6% 4 4 4 3 6% 7% 45%	4870
	11th to 20th	Day	9% 6% 2 7% 4 4 6% 5% 7% 9% 40%	4256
	21st to end	Day	10% 5% 2 6% 4 4 5% 4 6% 8% 45%	4664
September	1st to 10th	Day	12% 7% 2 7% 5% 4 5% 4 6% 8% 41%	2550
	11th to 20th	Day	13% 7% 3 7% 4 4 4 4 6% 9% 39%	2236
	21st to end	Day	8% 7% 3 6% 6% 4 4 4 7% 9% 43%	2200
October	1st to 10th	Day	10% 12% 4 8% 5% 5% 4 4 6% 9% 34%	3307
	11th to 20th	Day	13% 11% 3 8% 5% 5% 5% 4 5% 6% 34%	3042
	21st to end	Day	8% 16% 6% 10% 5% 4 5% 4 6% 7% 29%	3008
November	1st to 10th	Day	12% 14% 5% 11% 6% 6% 6% 4 6% 5% 25%	1648
	11th to 20th	Day	9% 13% 4 14% 7% 6% 6% 4 6% 7% 25%	1519
	21st to end	Day	5% 12% 7% 14% 8% 6% 5% 4 5% 7% 27%	1470
December	1st to 10th	Day	8% 12% 5% 15% 7% 6% 7% 5% 8% 8% 18%	2039
	11th to 20th	Day	8% 15% 6% 14% 9% 6% 4 4 5% 6% 24%	2319
	21st to end	Day	3 9% 4 13% 8% 7% 7% 4 6% 7% 32%	3338
January	1st to 10th	Night	7% 13% 5% 15% 9% 7% 8% 5% 6% 6% 19%	8768
	11th to 20th	Night	3 9% 3 9% 6% 7% 8% 6% 6% 9% 34%	8779
	21st to end	Night	6% 11% 5% 12% 8% 7% 6% 4 6% 7% 29%	9650
February	1st to 10th	Night	6% 12% 4 12% 8% 6% 6% 5% 7% 7% 26%	2957
	11th to 20th	Night	6% 11% 3 12% 8% 6% 5% 4 7% 7% 31%	2698
	21st to end	Night	3 10% 4 10% 7% 7% 8% 6% 8% 9% 28%	2249
March	1st to 10th	Night	3 10% 5% 11% 7% 7% 7% 5% 7% 9% 29%	5500
	11th to 20th	Night	5% 11% 4 10% 5% 6% 6% 5% 7% 10% 33%	5110
	21st to end	Night	11% 16% 6% 12% 5% 5% 4 4 5% 7% 25%	5610
April	1st to 10th	Night	8% 10% 3 8% 6% 5% 6% 5% 7% 8% 35%	1948
	11th to 20th	Night	9% 9% 3 11% 6% 6% 6% 4 6% 8% 31%	1871
	21st to end	Night	13% 12% 3 8% 6% 4 4 4 6% 6% 33%	1829
May	1st to 10th	Night	11% 6% 2 6% 4 4 4 4 6% 9% 45%	4253
	11th to 20th	Night	16% 11% 4 9% 5% 5% 5% 5% 6% 6% 28%	4105
	21st to end	Night	12% 7% 3 8% 5% 5% 5% 4 7% 9% 34%	4522
June	1st to 10th	Night	18% 7% 3 8% 6% 6% 6% 5% 6% 6% 30%	1346
	11th to 20th	Night	17% 9% 3 8% 6% 6% 6% 5% 7% 5% 28%	1109
	21st to end	Night	11% 5% 2 8% 6% 6% 5% 5% 8% 8% 36%	1059
July	1st to 10th	Night	6% 5% 2 6% 4 5% 5% 5% 8% 11% 43%	2922
	11th to 20th	Night	7% 5% 2 6% 5% 5% 5% 4 7% 8% 46%	3180
	21st to end	Night	13% 5% 2 6% 3 3 4 4 6% 8% 44%	3467
August	1st to 10th	Night	10% 6% 2 7% 5% 4 5% 4 5% 7% 44%	2280
	11th to 20th	Night	10% 6% 3 7% 4 5% 5% 4 7% 9% 38%	2795
	21st to end	Night	10% 5% 2 5% 4 4 5% 4 6% 8% 45%	3245
September	1st to 10th	Night	12% 6% 2 5% 3 3 5% 4 7% 9% 44%	1850
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 6% 9% 43%	2160
	21st to end	Night	10% 6% 2 6% 5% 5% 4 4 7% 8% 44%	2200
October	1st to 10th	Night	8% 8% 2 8% 5% 5% 6% 5% 7% 9% 36%	3884
	11th to 20th	Night	11% 9% 3 7% 5% 5% 5% 4 7% 9% 36%	4105
	21st to end	Night	10% 11% 6% 11% 5% 5% 6% 5% 7% 8% 27%	4759
November	1st to 10th	Night	12% 16% 5% 11% 6% 4 5% 4 5% 5% 25%	2870
	11th to 20th	Night	8% 13% 4 12% 9% 6% 5% 4 6% 7% 25%	3098
	21st to end	Night	6% 14% 5% 12% 8% 6% 6% 3 6% 7% 26%	3150
December	1st to 10th	Night	9% 14% 5% 14% 7% 7% 6% 4 6% 7% 22%	5345
	11th to 20th	Night	6% 15% 6% 15% 10% 7% 5% 4 6% 6% 18%	6093
	21st to end	Night	3 9% 4 12% 9% 7% 5% 4 6% 7% 35%	7843

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	61% 7% 10% 16% 6%	4125
	11th to 20th	Day	48% 7% 18% 14% 12% 1	4140
	21st to end	Day	55% 9% 20% 10% 6%	4531
February	1st to 10th	Day	54% 9% 14% 14% 9%	1680
	11th to 20th	Day	50% 9% 15% 17% 8%	1818
	21st to end	Day	54% 9% 15% 16% 6%	1557
March	1st to 10th	Day	48% 9% 19% 19% 5%	4608
	11th to 20th	Day	46% 9% 17% 22% 6%	5110
	21st to end	Day	55% 7% 10% 20% 8%	5607
April	1st to 10th	Day	48% 9% 16% 17% 9%	2670
	11th to 20th	Day	50% 8% 13% 19% 9% 1	2700
	21st to end	Day	50% 8% 12% 20% 8% 1	2790
May	1st to 10th	Day	39% 7% 13% 28% 13% 1	8656
	11th to 20th	Day	53% 7% 10% 24% 7%	8759
	21st to end	Day	40% 11% 18% 21% 8% 1	9650
June	1st to 10th	Day	47% 10% 14% 20% 8% 1	3271
	11th to 20th	Day	54% 10% 13% 17% 5%	3506
	21st to end	Day	43% 12% 18% 20% 7%	3556
July	1st to 10th	Day	34% 10% 22% 27% 6%	6946
	11th to 20th	Day	33% 8% 15% 32% 11%	6699
	21st to end	Day	35% 9% 22% 28% 5%	7169
August	1st to 10th	Day	38% 9% 20% 31% 2	4852
	11th to 20th	Day	36% 12% 25% 21% 7%	4297
	21st to end	Day	35% 8% 30% 24% 3	4663
September	1st to 10th	Day	40% 9% 18% 26% 6% 1	2550
	11th to 20th	Day	42% 8% 21% 24% 6%	2236
	21st to end	Day	37% 9% 19% 25% 9% 1	2200
October	1st to 10th	Day	46% 7% 22% 22% 3	3307
	11th to 20th	Day	49% 6% 15% 25% 5%	3042
	21st to end	Day	54% 7% 20% 17% 2	3008
November	1st to 10th	Day	58% 9% 13% 16% 4	1648
	11th to 20th	Day	57% 9% 15% 15% 4	1519
	21st to end	Day	56% 8% 15% 17% 4	1470
December	1st to 10th	Day	60% 9% 13% 14% 4	2039
	11th to 20th	Day	60% 7% 15% 15% 3	2320
	21st to end	Day	49% 6% 13% 25% 5% 1	3338
January	1st to 10th	Night	61% 7% 11% 13% 8%	8769
	11th to 20th	Night	45% 6% 18% 20% 11% 1	8820
	21st to end	Night	53% 8% 21% 12% 6%	9650
February	1st to 10th	Night	54% 8% 14% 15% 9%	2957
	11th to 20th	Night	50% 7% 12% 20% 10%	2699
	21st to end	Night	48% 9% 17% 17% 9%	2249
March	1st to 10th	Night	47% 8% 18% 20% 6%	5500
	11th to 20th	Night	44% 9% 17% 25% 6%	5110
	21st to end	Night	54% 8% 11% 16% 10%	5610
April	1st to 10th	Night	44% 7% 17% 22% 11%	1948
	11th to 20th	Night	47% 9% 12% 18% 12% 3	1871
	21st to end	Night	49% 5% 11% 22% 11% 2	1829
May	1st to 10th	Night	34% 6% 12% 30% 15% 2	4253
	11th to 20th	Night	53% 7% 9% 25% 6%	4105
	21st to end	Night	42% 10% 17% 24% 6% 1	4526
June	1st to 10th	Night	51% 7% 13% 19% 8% 1	1346
	11th to 20th	Night	53% 9% 14% 18% 6% 1	1109
	21st to end	Night	41% 11% 18% 21% 8% 1	1059
July	1st to 10th	Night	30% 11% 24% 24% 11% 1	2888
	11th to 20th	Night	33% 7% 15% 34% 9% 1	3138
	21st to end	Night	34% 8% 22% 32% 4	3369
August	1st to 10th	Night	38% 8% 19% 33% 2	2273
	11th to 20th	Night	39% 11% 22% 22% 6%	2820
	21st to end	Night	35% 8% 26% 28% 4	3245
September	1st to 10th	Night	36% 8% 21% 27% 7% 2	1850
	11th to 20th	Night	36% 8% 19% 28% 9%	2160
	21st to end	Night	36% 8% 17% 27% 10% 1	2200
October	1st to 10th	Night	41% 8% 21% 23% 7%	3884
	11th to 20th	Night	43% 6% 18% 28% 5%	4105
	21st to end	Night	53% 7% 19% 17% 4	4759
November	1st to 10th	Night	59% 7% 12% 18% 4	2870
	11th to 20th	Night	57% 9% 15% 13% 5%	3098
	21st to end	Night	55% 9% 15% 16% 5%	3150
December	1st to 10th	Night	61% 8% 14% 12% 4	5345
	11th to 20th	Night	65% 7% 15% 10% 3	6091
	21st to end	Night	48% 6% 13% 21% 10% 1	7843

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% 12% 27% 37% 15% 3	220
	11th to 20th	Day	13% 10% 35% 29% 11% 3	220
	21st to end	Day	10% 12% 41% 24% 9% 3	242
February	1st to 10th	Day	9% 14% 38% 26% 10% 3	220
	11th to 20th	Day	10% 13% 33% 28% 14% 2	312
	21st to end	Day	10% 13% 34% 26% 13% 4	273
March	1st to 10th	Day	9% 17% 37% 27% 8% 1	509
	11th to 20th	Day	12% 14% 40% 24% 8% 2	540
	21st to end	Day	17% 15% 32% 27% 8% 1	594
April	1st to 10th	Day	13% 17% 32% 28% 8% 2	540
	11th to 20th	Day	16% 15% 31% 25% 11% 2	532
	21st to end	Day	17% 16% 31% 24% 9% 3	600
May	1st to 10th	Day	10% 17% 28% 26% 15% 4	753
	11th to 20th	Day	15% 9% 26% 27% 17% 5%	775
	21st to end	Day	16% 8% 25% 29% 18% 4	844
June	1st to 10th	Day	20% 12% 29% 26% 10% 3	780
	11th to 20th	Day	21% 9% 23% 26% 16% 6%	926
	21st to end	Day	13% 6% 22% 32% 21% 7%	990
July	1st to 10th	Day	12% 7% 25% 30% 22% 4	831
	11th to 20th	Day	14% 5% 24% 30% 19% 8%	718
	21st to end	Day	11% 7% 25% 28% 21% 8%	794
August	1st to 10th	Day	13% 6% 20% 30% 21% 10%	726
	11th to 20th	Day	11% 8% 29% 33% 15% 5%	518
	21st to end	Day	11% 10% 25% 29% 20% 6%	583
September	1st to 10th	Day	15% 14% 28% 23% 16% 4	530
	11th to 20th	Day	17% 9% 26% 32% 12% 4	530
	21st to end	Day	12% 15% 35% 26% 11% 2	530
October	1st to 10th	Day	16% 11% 31% 29% 11% 2	354
	11th to 20th	Day	19% 13% 38% 24% 5%	330
	21st to end	Day	21% 15% 35% 19% 8% 2	363
November	1st to 10th	Day	22% 11% 30% 27% 8% 2	330
	11th to 20th	Day	16% 11% 44% 20% 9%	245
	21st to end	Day	10% 11% 39% 26% 10% 5%	220
December	1st to 10th	Day	10% 11% 35% 31% 10% 4	220
	11th to 20th	Day	13% 12% 41% 24% 10%	220
	21st to end	Day	10% 8% 28% 33% 16% 6%	242
January	1st to 10th	Night	11% 9% 33% 34% 11% 1	1050
	11th to 20th	Night	11% 11% 32% 35% 9% 1	1050
	21st to end	Night	15% 11% 36% 28% 9% 2	1155
February	1st to 10th	Night	11% 8% 31% 34% 14% 2	857
	11th to 20th	Night	10% 7% 31% 38% 13% 1	824
	21st to end	Night	6% 6% 30% 37% 18% 2	692
March	1st to 10th	Night	9% 8% 34% 34% 14% 1	840
	11th to 20th	Night	13% 7% 35% 31% 12% 1	840
	21st to end	Night	16% 8% 28% 34% 13% 2	924
April	1st to 10th	Night	11% 7% 32% 34% 15% 1	668
	11th to 20th	Night	11% 8% 34% 33% 13% 1	623
	21st to end	Night	17% 9% 27% 32% 14% 1	630
May	1st to 10th	Night	12% 8% 27% 34% 16% 3	469
	11th to 20th	Night	13% 7% 26% 34% 17% 3	414
	21st to end	Night	18% 6% 23% 33% 19% 2	455
June	1st to 10th	Night	22% 5% 25% 33% 14% 1	420
	11th to 20th	Night	18% 7% 22% 28% 24% 1	420
	21st to end	Night	13% 4 18% 36% 26% 3	420
July	1st to 10th	Night	10% 6% 20% 37% 26% 1	390
	11th to 20th	Night	11% 4 19% 40% 24% 2	388
	21st to end	Night	9% 4 19% 40% 24% 4	438
August	1st to 10th	Night	11% 4 14% 37% 29% 5%	398
	11th to 20th	Night	11% 5% 23% 39% 21% 2	528
	21st to end	Night	13% 3 22% 39% 22% 1	660
September	1st to 10th	Night	15% 5% 23% 33% 22% 2	600
	11th to 20th	Night	14% 5% 23% 40% 16%	760
	21st to end	Night	12% 8% 32% 34% 13% 1	800
October	1st to 10th	Night	16% 7% 32% 34% 11% 1	800
	11th to 20th	Night	16% 5% 34% 33% 10% 2	800
	21st to end	Night	18% 11% 33% 28% 9% 1	977
November	1st to 10th	Night	19% 9% 33% 29% 8% 1	1025
	11th to 20th	Night	14% 10% 35% 29% 9% 3	1050
	21st to end	Night	10% 10% 39% 28% 11% 1	1050
December	1st to 10th	Night	13% 10% 34% 29% 12% 2	1050
	11th to 20th	Night	12% 12% 35% 31% 9% 2	1050
	21st to end	Night	10% 6% 31% 35% 15% 3	1155

Page generated at 2026-06-28 00:10:50. Version ac07

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