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 2025-02-25.

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% 4 6% 8% 33%	112077
	Night	8% 10% 4 10% 7% 6% 6% 4 6% 8% 31%	115164
Transparency	Day	46% 9% 18% 21% 6%	111818
	Night	48% 8% 17% 20% 7% 1	115069
Seeing	Day	14% 11% 29% 28% 14% 4	16228
	Night	13% 8% 30% 33% 14% 2	25024

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	4 13% 6% 16% 11% 7% 7% 4 6% 5% 21%	3179
	11th to 20th	Day	5% 11% 4 11% 7% 7% 8% 7% 8% 9% 25%	3159
	21st to end	Day	7% 12% 5% 14% 8% 6% 5% 3 5% 7% 27%	3498
February	1st to 10th	Day	6% 13% 5% 12% 7% 6% 6% 6% 9% 7% 23%	1600
	11th to 20th	Day	6% 10% 4 12% 8% 6% 6% 5% 6% 8% 28%	1720
	21st to end	Day	4 14% 4 10% 9% 8% 7% 5% 8% 9% 23%	1449
March	1st to 10th	Day	3 10% 5% 10% 7% 7% 8% 6% 8% 10% 28%	3129
	11th to 20th	Day	5% 9% 4 8% 6% 5% 6% 5% 9% 10% 34%	3489
	21st to end	Day	11% 14% 4 13% 6% 5% 4 4 5% 7% 28%	3825
April	1st to 10th	Day	8% 13% 4 9% 7% 5% 6% 5% 7% 7% 30%	2416
	11th to 20th	Day	12% 12% 4 8% 6% 6% 5% 5% 6% 7% 30%	2440
	21st to end	Day	14% 10% 3 9% 6% 5% 5% 4 7% 8% 29%	2524
May	1st to 10th	Day	14% 9% 3 7% 5% 6% 6% 5% 6% 8% 30%	4668
	11th to 20th	Day	16% 10% 3 7% 5% 5% 5% 4 6% 6% 32%	4694
	21st to end	Day	12% 9% 3 9% 6% 5% 6% 5% 7% 8% 30%	5161
June	1st to 10th	Day	16% 8% 3 7% 6% 5% 5% 6% 7% 7% 31%	2959
	11th to 20th	Day	17% 9% 3 8% 6% 5% 6% 5% 8% 8% 25%	3172
	21st to end	Day	11% 6% 2 8% 5% 6% 6% 5% 7% 9% 34%	3218
July	1st to 10th	Day	9% 5% 2 6% 5% 5% 5% 5% 6% 9% 44%	4910
	11th to 20th	Day	9% 4 2 6% 4 4 4 4 6% 10% 47%	4740
	21st to end	Day	15% 5% 2 5% 4 4 5% 4 6% 8% 41%	5138
August	1st to 10th	Day	12% 7% 3 6% 4 4 4 3 6% 7% 45%	4720
	11th to 20th	Day	9% 6% 2 7% 4 4 6% 5% 7% 9% 41%	4123
	21st to end	Day	10% 5% 2 6% 4 4 5% 4 6% 9% 44%	4521
September	1st to 10th	Day	12% 7% 2 7% 5% 4 5% 4 5% 8% 41%	2423
	11th to 20th	Day	14% 7% 3 7% 5% 4 4 4 6% 8% 38%	2124
	21st to end	Day	9% 7% 3 6% 6% 5% 4 4 7% 9% 41%	2090
October	1st to 10th	Day	10% 12% 4 8% 5% 5% 4 4 6% 9% 33%	3206
	11th to 20th	Day	13% 11% 3 8% 5% 5% 5% 4 5% 6% 34%	2949
	21st to end	Day	8% 16% 6% 11% 5% 4 5% 4 6% 7% 29%	2915
November	1st to 10th	Day	12% 14% 5% 11% 7% 6% 6% 4 6% 5% 24%	1568
	11th to 20th	Day	9% 13% 5% 15% 7% 6% 6% 4 6% 7% 24%	1447
	21st to end	Day	5% 12% 7% 14% 8% 6% 5% 4 5% 7% 26%	1400
December	1st to 10th	Day	8% 12% 6% 15% 7% 6% 6% 5% 8% 8% 19%	1978
	11th to 20th	Day	8% 16% 6% 14% 9% 6% 4 4 5% 6% 24%	2259
	21st to end	Day	3 9% 4 13% 8% 7% 7% 4 6% 7% 32%	3266
January	1st to 10th	Night	5% 11% 5% 16% 11% 8% 8% 6% 7% 6% 19%	6766
	11th to 20th	Night	4 10% 3 9% 7% 7% 8% 6% 6% 8% 31%	6739
	21st to end	Night	6% 10% 5% 12% 7% 6% 5% 4 6% 7% 31%	7458
February	1st to 10th	Night	6% 11% 4 13% 8% 6% 7% 5% 7% 7% 26%	2816
	11th to 20th	Night	6% 11% 3 12% 8% 7% 5% 4 7% 7% 30%	2567
	21st to end	Night	4 9% 4 10% 7% 7% 7% 6% 8% 9% 29%	2099
March	1st to 10th	Night	3 11% 5% 11% 7% 6% 7% 6% 7% 9% 27%	3740
	11th to 20th	Night	5% 9% 2 8% 5% 6% 6% 5% 7% 10% 37%	3490
	21st to end	Night	10% 13% 5% 13% 6% 5% 5% 5% 6% 7% 25%	3828
April	1st to 10th	Night	9% 10% 3 8% 6% 5% 6% 5% 6% 8% 34%	1762
	11th to 20th	Night	9% 9% 3 12% 6% 6% 6% 4 6% 8% 30%	1691
	21st to end	Night	13% 12% 3 8% 6% 5% 4 4 6% 7% 33%	1655
May	1st to 10th	Night	18% 7% 3 7% 5% 5% 4 4 6% 8% 32%	2291
	11th to 20th	Night	16% 9% 3 8% 5% 4 5% 4 5% 7% 35%	2199
	21st to end	Night	13% 7% 3 8% 6% 5% 5% 5% 7% 8% 32%	2414
June	1st to 10th	Night	17% 7% 3 7% 6% 7% 6% 5% 7% 6% 30%	1218
	11th to 20th	Night	17% 8% 3 8% 6% 6% 6% 5% 7% 5% 28%	1003
	21st to end	Night	11% 5% 3 8% 7% 6% 5% 4 8% 8% 36%	958
July	1st to 10th	Night	7% 5% 2 5% 4 4 5% 4 8% 10% 45%	2046
	11th to 20th	Night	6% 5% 2 5% 4 5% 6% 4 7% 9% 48%	2220
	21st to end	Night	15% 5% 2 4 3 3 4 4 6% 8% 46%	2414
August	1st to 10th	Night	11% 6% 2 7% 5% 4 5% 4 5% 7% 43%	2210
	11th to 20th	Night	10% 6% 3 7% 4 5% 5% 4 7% 9% 39%	2708
	21st to end	Night	10% 6% 2 5% 4 4 5% 4 6% 8% 45%	3146
September	1st to 10th	Night	13% 6% 3 6% 3 3 5% 4 6% 8% 43%	1757
	11th to 20th	Night	13% 6% 2 6% 4 4 4 3 6% 9% 42%	2052
	21st to end	Night	10% 6% 2 6% 5% 5% 4 4 7% 8% 44%	2090
October	1st to 10th	Night	8% 8% 2 8% 5% 5% 6% 5% 7% 9% 36%	3765
	11th to 20th	Night	11% 9% 3 8% 5% 5% 5% 4 7% 9% 36%	3979
	21st to end	Night	10% 11% 6% 11% 5% 5% 6% 5% 7% 8% 26%	4611
November	1st to 10th	Night	12% 16% 5% 11% 6% 4 5% 4 5% 5% 25%	2730
	11th to 20th	Night	8% 14% 4 13% 9% 7% 5% 4 6% 7% 23%	2950
	21st to end	Night	6% 14% 5% 12% 8% 6% 6% 4 7% 7% 25%	3000
December	1st to 10th	Night	9% 14% 5% 14% 7% 6% 6% 4 6% 7% 22%	5186
	11th to 20th	Night	7% 15% 6% 15% 10% 7% 6% 4 6% 6% 19%	5933
	21st to end	Night	3 9% 4 12% 9% 7% 6% 4 5% 6% 35%	7673

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% 15% 7%	3179
	11th to 20th	Day	53% 8% 15% 12% 12% 1	3180
	21st to end	Day	54% 9% 22% 11% 5%	3498
February	1st to 10th	Day	54% 9% 14% 13% 10%	1600
	11th to 20th	Day	51% 9% 15% 17% 7%	1729
	21st to end	Day	55% 9% 15% 15% 7%	1449
March	1st to 10th	Day	47% 10% 20% 19% 4	3129
	11th to 20th	Day	40% 11% 21% 22% 6%	3490
	21st to end	Day	53% 9% 12% 20% 6%	3825
April	1st to 10th	Day	49% 10% 16% 17% 9%	2416
	11th to 20th	Day	51% 8% 13% 19% 9% 1	2440
	21st to end	Day	51% 9% 12% 19% 8% 1	2524
May	1st to 10th	Day	49% 9% 12% 22% 8%	4668
	11th to 20th	Day	49% 8% 11% 22% 10%	4698
	21st to end	Day	44% 13% 17% 18% 7%	5162
June	1st to 10th	Day	48% 10% 14% 20% 7% 1	2959
	11th to 20th	Day	54% 11% 14% 17% 5%	3172
	21st to end	Day	43% 12% 18% 20% 6%	3218
July	1st to 10th	Day	35% 11% 21% 27% 6%	4835
	11th to 20th	Day	31% 9% 19% 29% 12% 1	4659
	21st to end	Day	38% 10% 22% 25% 5%	4976
August	1st to 10th	Day	38% 9% 20% 31% 2	4702
	11th to 20th	Day	35% 11% 25% 21% 7%	4164
	21st to end	Day	35% 9% 31% 23% 2	4520
September	1st to 10th	Day	41% 9% 18% 25% 6% 1	2423
	11th to 20th	Day	43% 8% 20% 23% 5%	2124
	21st to end	Day	38% 9% 20% 23% 9% 1	2090
October	1st to 10th	Day	47% 7% 22% 22% 3	3206
	11th to 20th	Day	49% 6% 16% 25% 4	2949
	21st to end	Day	54% 7% 21% 16% 2	2915
November	1st to 10th	Day	59% 9% 13% 16% 3	1568
	11th to 20th	Day	58% 9% 15% 15% 3	1447
	21st to end	Day	56% 9% 15% 16% 4	1400
December	1st to 10th	Day	60% 9% 14% 14% 4	1978
	11th to 20th	Day	60% 7% 15% 15% 2	2260
	21st to end	Day	49% 6% 14% 25% 6% 1	3266
January	1st to 10th	Night	60% 8% 12% 12% 7% 1	6766
	11th to 20th	Night	49% 6% 14% 19% 11% 1	6780
	21st to end	Night	50% 8% 23% 14% 4	7458
February	1st to 10th	Night	54% 8% 13% 15% 10%	2816
	11th to 20th	Night	50% 7% 13% 20% 9%	2568
	21st to end	Night	47% 9% 17% 17% 9%	2099
March	1st to 10th	Night	48% 9% 17% 22% 4	3740
	11th to 20th	Night	39% 10% 20% 24% 6%	3490
	21st to end	Night	51% 10% 14% 19% 6%	3828
April	1st to 10th	Night	44% 7% 17% 21% 11% 1	1762
	11th to 20th	Night	48% 9% 11% 18% 11% 2	1691
	21st to end	Night	49% 5% 12% 21% 10% 2	1655
May	1st to 10th	Night	47% 8% 12% 23% 10% 1	2291
	11th to 20th	Night	46% 8% 10% 24% 11% 1	2199
	21st to end	Night	44% 13% 17% 18% 7% 1	2414
June	1st to 10th	Night	51% 8% 14% 18% 8% 1	1218
	11th to 20th	Night	53% 9% 13% 18% 6% 1	1003
	21st to end	Night	41% 11% 18% 21% 8% 1	958
July	1st to 10th	Night	29% 11% 24% 26% 8% 1	2012
	11th to 20th	Night	30% 9% 17% 34% 8% 1	2178
	21st to end	Night	34% 8% 22% 30% 5%	2337
August	1st to 10th	Night	38% 8% 19% 34% 1	2203
	11th to 20th	Night	38% 11% 22% 23% 7%	2733
	21st to end	Night	35% 8% 26% 28% 3	3146
September	1st to 10th	Night	37% 8% 20% 26% 7% 2	1757
	11th to 20th	Night	38% 8% 20% 27% 8%	2052
	21st to end	Night	36% 9% 17% 27% 11% 1	2090
October	1st to 10th	Night	41% 8% 22% 23% 6%	3765
	11th to 20th	Night	44% 6% 18% 28% 4	3979
	21st to end	Night	53% 7% 19% 17% 4	4611
November	1st to 10th	Night	59% 7% 12% 18% 4	2730
	11th to 20th	Night	58% 9% 16% 12% 4	2950
	21st to end	Night	56% 9% 15% 16% 4	3000
December	1st to 10th	Night	61% 8% 14% 12% 4 1	5186
	11th to 20th	Night	65% 7% 15% 10% 3	5931
	21st to end	Night	48% 6% 13% 21% 10% 1	7673

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% 11% 27% 37% 15% 3	200
	11th to 20th	Day	13% 9% 33% 32% 11% 3	200
	21st to end	Day	11% 12% 42% 23% 8% 4	220
February	1st to 10th	Day	9% 14% 39% 27% 9% 3	200
	11th to 20th	Day	10% 13% 32% 28% 15% 2	283
	21st to end	Day	9% 14% 33% 26% 14% 4	237
March	1st to 10th	Day	9% 17% 38% 26% 9% 1	431
	11th to 20th	Day	11% 15% 41% 25% 7% 2	460
	21st to end	Day	16% 14% 33% 27% 8% 1	506
April	1st to 10th	Day	13% 18% 33% 26% 7% 2	460
	11th to 20th	Day	17% 14% 30% 25% 12% 3	452
	21st to end	Day	17% 17% 32% 25% 8% 2	514
May	1st to 10th	Day	10% 16% 27% 27% 15% 5%	653
	11th to 20th	Day	14% 9% 27% 28% 17% 5%	675
	21st to end	Day	16% 8% 25% 29% 19% 4	734
June	1st to 10th	Day	20% 11% 30% 26% 10% 2	680
	11th to 20th	Day	20% 9% 24% 25% 17% 5%	812
	21st to end	Day	13% 6% 21% 32% 21% 7%	870
July	1st to 10th	Day	12% 6% 25% 31% 23% 4	775
	11th to 20th	Day	14% 5% 24% 30% 19% 7%	668
	21st to end	Day	12% 6% 25% 29% 20% 8%	739
August	1st to 10th	Day	13% 6% 21% 30% 20% 9%	676
	11th to 20th	Day	10% 8% 30% 33% 14% 5%	478
	21st to end	Day	11% 10% 26% 29% 18% 5%	539
September	1st to 10th	Day	17% 14% 30% 22% 14% 3	490
	11th to 20th	Day	18% 10% 28% 29% 12% 3	490
	21st to end	Day	12% 14% 34% 27% 11% 2	490
October	1st to 10th	Day	17% 11% 30% 28% 11% 2	323
	11th to 20th	Day	19% 13% 38% 26% 5%	300
	21st to end	Day	21% 15% 35% 19% 9% 2	330
November	1st to 10th	Day	23% 10% 28% 28% 8% 2	300
	11th to 20th	Day	16% 11% 44% 20% 8%	223
	21st to end	Day	10% 12% 41% 26% 8% 4	200
December	1st to 10th	Day	9% 12% 33% 33% 10% 4	200
	11th to 20th	Day	13% 12% 40% 25% 11%	200
	21st to end	Day	8% 9% 27% 33% 17% 6%	220
January	1st to 10th	Night	11% 9% 34% 34% 12% 1	1000
	11th to 20th	Night	11% 10% 32% 36% 10% 1	1000
	21st to end	Night	14% 11% 36% 28% 9% 2	1100
February	1st to 10th	Night	11% 7% 31% 34% 14% 2	816
	11th to 20th	Night	10% 7% 31% 38% 13% 1	784
	21st to end	Night	6% 5% 31% 37% 18% 2	646
March	1st to 10th	Night	9% 8% 33% 34% 14% 1	760
	11th to 20th	Night	13% 7% 36% 30% 13% 1	760
	21st to end	Night	16% 8% 28% 33% 13% 2	836
April	1st to 10th	Night	11% 7% 33% 33% 15% 1	604
	11th to 20th	Night	11% 7% 33% 34% 14% 1	563
	21st to end	Night	17% 9% 27% 32% 13% 1	570
May	1st to 10th	Night	13% 8% 25% 33% 18% 3	425
	11th to 20th	Night	12% 7% 26% 35% 17% 3	374
	21st to end	Night	18% 6% 23% 31% 20% 2	411
June	1st to 10th	Night	21% 4 25% 34% 14% 1	380
	11th to 20th	Night	18% 7% 22% 28% 23% 2	380
	21st to end	Night	12% 4 19% 35% 26% 3	380
July	1st to 10th	Night	11% 5% 20% 38% 26% 1	370
	11th to 20th	Night	12% 4 20% 40% 23% 2	368
	21st to end	Night	10% 4 19% 39% 24% 4	416
August	1st to 10th	Night	11% 4 14% 37% 28% 5%	378
	11th to 20th	Night	10% 5% 23% 39% 22% 2	501
	21st to end	Night	14% 3 22% 39% 21% 1	627
September	1st to 10th	Night	16% 5% 24% 32% 21% 2	570
	11th to 20th	Night	15% 5% 25% 39% 16%	722
	21st to end	Night	12% 8% 31% 35% 14% 1	760
October	1st to 10th	Night	16% 6% 31% 35% 10% 1	760
	11th to 20th	Night	16% 5% 34% 33% 10% 2	760
	21st to end	Night	18% 11% 32% 29% 10% 1	928
November	1st to 10th	Night	19% 9% 33% 29% 9% 2	975
	11th to 20th	Night	14% 11% 34% 29% 9% 3	1000
	21st to end	Night	11% 10% 39% 28% 11% 1	1000
December	1st to 10th	Night	13% 10% 34% 29% 13% 2	1000
	11th to 20th	Night	12% 11% 34% 32% 9% 2	1000
	21st to end	Night	9% 6% 31% 35% 16% 3	1100

Page generated at 2025-02-22 04:51:34. Version ac07

Copyright © 2025 Attilla Danko.