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 2024-02-05.

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% 4 8% 7% 4 6% 6% 6% 8% 33%	77826
	Night	8% 9% 4 9% 8% 4 6% 6% 6% 7% 32%	80956
Transparency	Day	47% 10% 17% 20% 6%	77526
	Night	48% 8% 16% 20% 7% 1	80836
Seeing	Day	14% 11% 29% 28% 14% 4	14828
	Night	13% 7% 30% 33% 14% 2	23650

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% 8% 14% 14% 5% 6% 5% 5% 5% 19%	2219
	11th to 20th	Day	5% 7% 4 9% 8% 6% 7% 12% 9% 9% 23%	2199
	21st to end	Day	7% 10% 5% 11% 10% 5% 6% 5% 5% 6% 29%	2442
February	1st to 10th	Day	6% 11% 6% 11% 8% 5% 6% 7% 8% 7% 24%	1472
	11th to 20th	Day	7% 10% 5% 10% 10% 4 6% 7% 7% 8% 25%	1543
	21st to end	Day	5% 13% 5% 9% 9% 6% 8% 6% 8% 9% 23%	1332
March	1st to 10th	Day	6% 12% 5% 10% 9% 6% 7% 6% 7% 9% 22%	1790
	11th to 20th	Day	8% 11% 5% 7% 6% 4 5% 5% 6% 7% 34%	1979
	21st to end	Day	9% 14% 4 9% 7% 4 5% 5% 6% 8% 28%	2178
April	1st to 10th	Day	9% 11% 4 8% 8% 4 6% 6% 7% 7% 31%	2288
	11th to 20th	Day	12% 11% 4 7% 7% 4 6% 6% 6% 7% 30%	2310
	21st to end	Day	13% 9% 4 7% 7% 4 5% 6% 6% 8% 30%	2391
May	1st to 10th	Day	9% 8% 4 7% 6% 5% 6% 7% 7% 9% 32%	2654
	11th to 20th	Day	10% 5% 3 6% 6% 3 6% 6% 7% 8% 40%	2654
	21st to end	Day	14% 7% 3 5% 5% 4 4 5% 7% 8% 38%	2917
June	1st to 10th	Day	15% 8% 3 6% 6% 4 6% 6% 7% 8% 32%	2803
	11th to 20th	Day	18% 8% 4 8% 6% 4 6% 6% 7% 8% 25%	3005
	21st to end	Day	11% 6% 2 7% 6% 5% 6% 6% 7% 9% 33%	3049
July	1st to 10th	Day	12% 5% 3 6% 6% 3 6% 6% 6% 8% 39%	2800
	11th to 20th	Day	12% 5% 3 6% 6% 4 5% 5% 7% 11% 36%	2700
	21st to end	Day	9% 5% 3 5% 5% 3 6% 6% 7% 8% 42%	2938
August	1st to 10th	Day	11% 6% 2 5% 5% 3 5% 6% 8% 10% 39%	2686
	11th to 20th	Day	9% 5% 1 4 6% 3 6% 6% 7% 10% 43%	2358
	21st to end	Day	10% 6% 3 6% 6% 4 6% 6% 6% 8% 40%	2574
September	1st to 10th	Day	13% 7% 2 5% 6% 3 5% 5% 5% 8% 39%	2296
	11th to 20th	Day	14% 7% 3 6% 6% 3 4 5% 5% 8% 38%	2013
	21st to end	Day	9% 6% 3 5% 6% 4 4 5% 6% 10% 42%	1980
October	1st to 10th	Day	12% 12% 5% 7% 6% 4 5% 4 4 8% 33%	1822
	11th to 20th	Day	12% 11% 4 8% 5% 4 5% 5% 5% 6% 37%	1688
	21st to end	Day	12% 14% 4 11% 7% 3 4 5% 5% 7% 27%	1676
November	1st to 10th	Day	12% 13% 6% 10% 8% 5% 6% 6% 5% 5% 24%	1488
	11th to 20th	Day	9% 12% 5% 13% 10% 4 5% 5% 5% 7% 24%	1375
	21st to end	Day	5% 11% 7% 13% 9% 5% 5% 5% 4 8% 27%	1330
December	1st to 10th	Day	5% 9% 6% 11% 8% 6% 9% 6% 8% 8% 22%	1158
	11th to 20th	Day	7% 12% 5% 11% 9% 5% 6% 6% 6% 7% 26%	1439
	21st to end	Day	4 7% 3 8% 7% 5% 7% 6% 7% 8% 39%	2280
January	1st to 10th	Night	5% 11% 6% 16% 13% 6% 7% 7% 5% 5% 19%	4726
	11th to 20th	Night	4 9% 4 8% 8% 6% 9% 9% 7% 7% 27%	4699
	21st to end	Night	6% 10% 5% 11% 9% 5% 5% 5% 6% 7% 30%	5214
February	1st to 10th	Night	7% 10% 4 11% 10% 5% 7% 7% 7% 7% 27%	2598
	11th to 20th	Night	6% 12% 4 11% 9% 5% 5% 5% 7% 7% 29%	2304
	21st to end	Night	4 8% 5% 8% 8% 5% 9% 8% 8% 9% 29%	1924
March	1st to 10th	Night	5% 11% 5% 11% 9% 4 6% 7% 6% 8% 28%	2166
	11th to 20th	Night	8% 11% 4 9% 6% 4 6% 6% 6% 8% 33%	1980
	21st to end	Night	9% 14% 6% 8% 6% 3 4 7% 7% 8% 28%	2178
April	1st to 10th	Night	9% 9% 3 6% 7% 4 6% 6% 6% 9% 35%	1671
	11th to 20th	Night	9% 8% 3 10% 8% 5% 6% 5% 6% 8% 31%	1601
	21st to end	Night	14% 11% 4 7% 6% 4 4 5% 6% 6% 33%	1568
May	1st to 10th	Night	10% 5% 3 7% 8% 4 5% 5% 6% 9% 38%	1303
	11th to 20th	Night	10% 5% 2 6% 6% 3 5% 5% 5% 8% 44%	1239
	21st to end	Night	15% 7% 3 6% 7% 3 4 5% 6% 8% 35%	1358
June	1st to 10th	Night	16% 7% 3 7% 7% 5% 7% 6% 6% 5% 30%	1154
	11th to 20th	Night	17% 7% 4 7% 7% 4 6% 6% 7% 6% 29%	951
	21st to end	Night	11% 5% 3 7% 8% 4 6% 6% 7% 8% 35%	907
July	1st to 10th	Night	10% 6% 2 5% 6% 3 5% 5% 7% 11% 41%	1156
	11th to 20th	Night	11% 5% 3 4 6% 3 7% 6% 8% 8% 39%	1260
	21st to end	Night	7% 4 3 4 4 2 5% 6% 7% 9% 48%	1379
August	1st to 10th	Night	9% 4 2 6% 6% 3 6% 7% 6% 9% 42%	1253
	11th to 20th	Night	9% 5% 3 5% 4 4 5% 6% 7% 9% 44%	1538
	21st to end	Night	11% 7% 3 5% 6% 3 6% 5% 6% 7% 42%	1782
September	1st to 10th	Night	13% 6% 3 5% 4 2 5% 5% 6% 8% 42%	1664
	11th to 20th	Night	12% 6% 3 5% 5% 3 4 4 6% 9% 42%	1944
	21st to end	Night	9% 5% 2 5% 5% 4 5% 5% 7% 8% 45%	1980
October	1st to 10th	Night	11% 8% 3 8% 7% 4 5% 6% 6% 7% 37%	2138
	11th to 20th	Night	10% 10% 4 7% 6% 4 5% 4 6% 8% 37%	2272
	21st to end	Night	11% 13% 5% 10% 8% 3 5% 4 5% 7% 30%	2661
November	1st to 10th	Night	13% 15% 5% 10% 7% 3 5% 5% 5% 5% 26%	2590
	11th to 20th	Night	8% 13% 5% 11% 10% 5% 7% 5% 6% 7% 23%	2802
	21st to end	Night	6% 12% 7% 10% 10% 4 6% 5% 6% 8% 26%	2850
December	1st to 10th	Night	7% 11% 6% 10% 8% 5% 6% 5% 6% 7% 29%	3020
	11th to 20th	Night	7% 12% 5% 12% 12% 6% 7% 6% 5% 6% 21%	3753
	21st to end	Night	3 7% 4 7% 7% 5% 6% 6% 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	55% 9% 14% 13% 8%	1472
	11th to 20th	Day	54% 10% 16% 16% 5%	1552
	21st to end	Day	54% 9% 15% 15% 7%	1332
March	1st to 10th	Day	56% 10% 19% 12% 3	1790
	11th to 20th	Day	49% 8% 15% 20% 7%	1980
	21st to end	Day	54% 9% 14% 18% 4	2178
April	1st to 10th	Day	49% 10% 16% 17% 8%	2288
	11th to 20th	Day	52% 8% 13% 18% 8% 1	2310
	21st to end	Day	51% 9% 13% 19% 8% 1	2391
May	1st to 10th	Day	46% 10% 13% 21% 11%	2654
	11th to 20th	Day	40% 8% 14% 25% 12% 1	2658
	21st to end	Day	43% 9% 13% 25% 10% 1	2918
June	1st to 10th	Day	48% 11% 14% 20% 6%	2803
	11th to 20th	Day	55% 11% 14% 16% 4	3005
	21st to end	Day	43% 13% 19% 20% 5%	3049
July	1st to 10th	Day	39% 12% 19% 24% 5% 1	2725
	11th to 20th	Day	41% 12% 26% 20% 1	2619
	21st to end	Day	36% 12% 25% 24% 3	2775
August	1st to 10th	Day	38% 13% 26% 22% 2	2668
	11th to 20th	Day	34% 12% 27% 23% 4	2358
	21st to end	Day	40% 11% 23% 23% 3	2574
September	1st to 10th	Day	43% 9% 18% 23% 5% 1	2296
	11th to 20th	Day	44% 8% 20% 23% 5%	2013
	21st to end	Day	37% 9% 19% 24% 9% 1	1980
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	54% 8% 14% 16% 8%	2598
	11th to 20th	Night	52% 7% 13% 19% 8%	2305
	21st to end	Night	47% 9% 17% 18% 9%	1924
March	1st to 10th	Night	51% 8% 15% 20% 6%	2166
	11th to 20th	Night	47% 8% 13% 24% 7% 1	1980
	21st to end	Night	51% 8% 16% 17% 7%	2178
April	1st to 10th	Night	43% 6% 18% 22% 11%	1671
	11th to 20th	Night	48% 9% 11% 18% 11% 3	1601
	21st to end	Night	50% 5% 12% 22% 9% 2	1568
May	1st to 10th	Night	42% 6% 15% 23% 13% 2	1303
	11th to 20th	Night	37% 7% 11% 27% 16% 1	1239
	21st to end	Night	46% 6% 12% 22% 11% 2	1358
June	1st to 10th	Night	51% 8% 14% 18% 8% 1	1154
	11th to 20th	Night	53% 10% 13% 18% 6% 1	951
	21st to end	Night	42% 11% 19% 21% 6% 1	907
July	1st to 10th	Night	33% 13% 21% 25% 6% 1	1122
	11th to 20th	Night	39% 12% 23% 24% 3	1218
	21st to end	Night	29% 11% 26% 31% 3	1302
August	1st to 10th	Night	37% 10% 23% 28% 2	1246
	11th to 20th	Night	33% 11% 27% 23% 6%	1538
	21st to end	Night	40% 9% 18% 29% 4	1782
September	1st to 10th	Night	38% 9% 21% 24% 7% 2	1664
	11th to 20th	Night	37% 8% 20% 27% 8%	1944
	21st to end	Night	34% 9% 17% 28% 11% 1	1980
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	11% 13% 39% 26% 10% 1	168
	11th to 20th	Day	12% 15% 32% 26% 14% 1	226
	21st to end	Day	8% 13% 31% 26% 17% 5%	198
March	1st to 10th	Day	9% 17% 38% 26% 9% 1	392
	11th to 20th	Day	11% 14% 41% 24% 7% 2	420
	21st to end	Day	16% 14% 33% 28% 9% 1	462
April	1st to 10th	Day	12% 18% 33% 27% 8% 2	420
	11th to 20th	Day	17% 13% 29% 26% 11% 3	412
	21st to end	Day	17% 16% 32% 25% 8% 2	471
May	1st to 10th	Day	10% 16% 27% 29% 15% 4	603
	11th to 20th	Day	13% 8% 27% 29% 18% 5%	625
	21st to end	Day	17% 7% 25% 28% 18% 5%	679
June	1st to 10th	Day	18% 10% 31% 28% 11% 2	630
	11th to 20th	Day	21% 8% 24% 25% 17% 5%	755
	21st to end	Day	13% 7% 22% 32% 20% 7%	810
July	1st to 10th	Day	12% 6% 26% 30% 22% 4	720
	11th to 20th	Day	15% 5% 24% 32% 18% 5%	618
	21st to end	Day	11% 6% 26% 30% 21% 7%	684
August	1st to 10th	Day	14% 6% 21% 30% 20% 9%	626
	11th to 20th	Day	10% 8% 32% 33% 14% 4	438
	21st to end	Day	11% 10% 27% 28% 19% 5%	495
September	1st to 10th	Day	18% 15% 30% 22% 12% 3	450
	11th to 20th	Day	19% 11% 28% 29% 11% 2	450
	21st to end	Day	11% 14% 34% 27% 12% 2	450
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	12% 8% 31% 33% 14% 2	754
	11th to 20th	Night	11% 8% 31% 36% 13% 1	704
	21st to end	Night	6% 5% 31% 38% 19% 2	592
March	1st to 10th	Night	9% 7% 33% 35% 14% 2	720
	11th to 20th	Night	13% 6% 36% 30% 13% 1	720
	21st to end	Night	16% 8% 28% 33% 14% 2	792
April	1st to 10th	Night	10% 6% 32% 34% 16% 2	573
	11th to 20th	Night	12% 7% 32% 34% 14% 1	533
	21st to end	Night	18% 9% 28% 32% 13% 1	540
May	1st to 10th	Night	12% 8% 26% 33% 18% 3	403
	11th to 20th	Night	11% 6% 26% 36% 17% 3	354
	21st to end	Night	19% 5% 23% 31% 20% 2	389
June	1st to 10th	Night	20% 4 24% 35% 15% 1	360
	11th to 20th	Night	17% 7% 23% 28% 24% 2	360
	21st to end	Night	13% 4 19% 35% 27% 3	360
July	1st to 10th	Night	11% 5% 21% 38% 25% 1	350
	11th to 20th	Night	12% 4 20% 40% 21% 2	348
	21st to end	Night	9% 4 20% 39% 25% 4	394
August	1st to 10th	Night	11% 4 15% 38% 28% 5%	358
	11th to 20th	Night	10% 4 24% 37% 22% 2	474
	21st to end	Night	14% 3 21% 40% 21% 1	594
September	1st to 10th	Night	16% 5% 24% 31% 22% 2	540
	11th to 20th	Night	14% 6% 25% 39% 16%	684
	21st to end	Night	11% 8% 30% 35% 15% 1	720
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 2024-02-02 03:20:31. Version ac07

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