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 2024-09-29.

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 8% 6% 5% 5% 5% 7% 8% 34%	102143
	Night	8% 10% 4 10% 6% 6% 6% 4 6% 7% 33%	96132
Transparency	Day	46% 9% 17% 21% 6%	101884
	Night	47% 9% 16% 21% 7% 1	96037
Seeing	Day	14% 11% 29% 28% 14% 4	15870
	Night	13% 8% 30% 33% 14% 2	24333

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	5% 14% 7% 16% 12% 6% 6% 4 5% 5% 19%	2219
	11th to 20th	Day	5% 8% 4 11% 7% 8% 9% 8% 10% 9% 23%	2199
	21st to end	Day	7% 11% 5% 13% 9% 6% 6% 3 5% 6% 29%	2442
February	1st to 10th	Day	6% 13% 5% 13% 7% 6% 6% 6% 8% 7% 23%	1520
	11th to 20th	Day	6% 11% 4 12% 8% 6% 5% 5% 7% 8% 27%	1631
	21st to end	Day	4 14% 5% 10% 9% 8% 7% 5% 8% 9% 23%	1413
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% 4 4 4 7% 9% 42%	2069
October	1st to 10th	Day	11% 13% 5% 8% 6% 5% 4 4 5% 8% 33%	1822
	11th to 20th	Day	11% 12% 3 8% 4 6% 5% 3 5% 6% 37%	1688
	21st to end	Day	12% 15% 4 12% 6% 4 4 4 6% 6% 27%	1676
November	1st to 10th	Day	12% 14% 5% 11% 7% 6% 6% 5% 5% 5% 24%	1488
	11th to 20th	Day	9% 13% 5% 15% 7% 6% 6% 4 6% 7% 24%	1375
	21st to end	Day	5% 12% 7% 14% 8% 6% 5% 4 5% 7% 27%	1330
December	1st to 10th	Day	5% 11% 5% 13% 7% 8% 7% 5% 9% 7% 22%	1158
	11th to 20th	Day	7% 13% 4 13% 8% 7% 5% 5% 6% 7% 25%	1439
	21st to end	Day	3 7% 3 9% 6% 6% 7% 4 7% 8% 39%	2280
January	1st to 10th	Night	5% 12% 5% 18% 11% 7% 7% 5% 5% 5% 19%	4726
	11th to 20th	Night	3 10% 4 10% 7% 8% 9% 7% 7% 7% 27%	4699
	21st to end	Night	6% 10% 5% 12% 8% 6% 5% 4 6% 7% 30%	5214
February	1st to 10th	Night	7% 11% 4 13% 8% 6% 6% 5% 7% 7% 26%	2676
	11th to 20th	Night	6% 12% 3 12% 7% 6% 5% 4 7% 7% 30%	2436
	21st to end	Night	3 9% 4 10% 7% 7% 8% 6% 8% 9% 29%	2041
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	9% 6% 2 6% 5% 5% 4 4 7% 8% 44%	2079
October	1st to 10th	Night	11% 8% 3 9% 5% 5% 5% 4 6% 7% 37%	2138
	11th to 20th	Night	9% 10% 4 8% 5% 5% 4 3 6% 7% 37%	2272
	21st to end	Night	11% 14% 5% 11% 6% 4 5% 3 5% 6% 30%	2661
November	1st to 10th	Night	12% 16% 5% 11% 7% 4 5% 4 5% 5% 26%	2590
	11th to 20th	Night	8% 14% 4 13% 9% 7% 5% 4 6% 7% 23%	2802
	21st to end	Night	6% 14% 5% 12% 8% 5% 6% 4 7% 7% 26%	2850
December	1st to 10th	Night	6% 13% 5% 11% 7% 7% 5% 4 6% 7% 29%	3020
	11th to 20th	Night	7% 12% 5% 13% 11% 8% 6% 5% 5% 6% 21%	3753
	21st to end	Night	3 8% 3 8% 6% 6% 6% 4 6% 8% 41%	5373

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	63% 8% 11% 14% 4	2219
	11th to 20th	Day	51% 8% 16% 15% 8% 1	2220
	21st to end	Day	53% 10% 18% 13% 7%	2442
February	1st to 10th	Day	56% 9% 14% 13% 8%	1520
	11th to 20th	Day	52% 10% 15% 17% 7%	1640
	21st to end	Day	55% 9% 14% 15% 7%	1413
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	37% 9% 20% 23% 9% 1	2069
October	1st to 10th	Day	50% 7% 19% 19% 5%	1822
	11th to 20th	Day	48% 6% 14% 26% 6%	1688
	21st to end	Day	55% 8% 16% 17% 4	1676
November	1st to 10th	Day	60% 9% 12% 16% 3	1488
	11th to 20th	Day	58% 9% 16% 14% 3	1375
	21st to end	Day	55% 9% 16% 16% 4	1330
December	1st to 10th	Day	55% 10% 12% 16% 6% 1	1158
	11th to 20th	Day	55% 10% 15% 17% 4	1440
	21st to end	Day	41% 7% 14% 30% 8% 1	2280
January	1st to 10th	Night	63% 9% 10% 12% 5% 1	4726
	11th to 20th	Night	51% 7% 14% 20% 7% 1	4740
	21st to end	Night	51% 10% 20% 14% 5%	5214
February	1st to 10th	Night	55% 8% 14% 16% 8%	2676
	11th to 20th	Night	51% 7% 13% 19% 9%	2437
	21st to end	Night	47% 9% 17% 17% 9%	2041
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	35% 9% 17% 27% 11% 2	2079
October	1st to 10th	Night	45% 8% 15% 23% 9%	2138
	11th to 20th	Night	44% 7% 16% 26% 6%	2272
	21st to end	Night	53% 7% 14% 19% 7%	2661
November	1st to 10th	Night	59% 7% 11% 18% 4	2590
	11th to 20th	Night	59% 10% 16% 12% 4	2802
	21st to end	Night	55% 9% 16% 16% 4	2850
December	1st to 10th	Night	53% 7% 15% 17% 7% 1	3020
	11th to 20th	Night	63% 8% 14% 11% 4	3751
	21st to end	Night	39% 8% 16% 23% 13% 2	5373

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% 28% 38% 13% 3	180
	11th to 20th	Day	12% 9% 31% 32% 12% 3	180
	21st to end	Day	10% 12% 39% 26% 9% 4	198
February	1st to 10th	Day	10% 14% 40% 26% 9% 1	180
	11th to 20th	Day	11% 14% 32% 26% 15% 2	254
	21st to end	Day	8% 14% 33% 25% 15% 4	225
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% 26% 11% 2	483
October	1st to 10th	Day	17% 11% 30% 28% 12% 2	292
	11th to 20th	Day	18% 14% 38% 25% 5%	270
	21st to end	Day	23% 15% 31% 20% 9% 2	297
November	1st to 10th	Day	25% 11% 28% 26% 8% 2	270
	11th to 20th	Day	16% 11% 44% 19% 8%	201
	21st to end	Day	11% 12% 41% 24% 8% 4	180
December	1st to 10th	Day	8% 10% 35% 31% 11% 4	180
	11th to 20th	Day	13% 11% 39% 26% 11%	180
	21st to end	Day	8% 9% 29% 33% 16% 6%	198
January	1st to 10th	Night	11% 9% 33% 35% 11% 1	950
	11th to 20th	Night	11% 10% 31% 37% 10% 1	950
	21st to end	Night	15% 11% 35% 28% 9% 2	1045
February	1st to 10th	Night	11% 8% 32% 33% 14% 2	776
	11th to 20th	Night	10% 8% 31% 37% 13% 1	744
	21st to end	Night	6% 5% 31% 37% 19% 2	628
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	756
October	1st to 10th	Night	16% 6% 31% 35% 11% 2	720
	11th to 20th	Night	16% 5% 34% 32% 11% 2	720
	21st to end	Night	18% 11% 31% 29% 10% 1	879
November	1st to 10th	Night	19% 8% 33% 30% 8% 2	925
	11th to 20th	Night	14% 10% 34% 29% 9% 3	950
	21st to end	Night	11% 10% 40% 28% 10% 1	950
December	1st to 10th	Night	13% 9% 33% 29% 13% 2	950
	11th to 20th	Night	12% 11% 34% 32% 9% 2	950
	21st to end	Night	9% 6% 31% 35% 16% 3	1045

Page generated at 2024-09-26 07:52:21. Version ac07

Copyright © 2024 Attilla Danko.