Lake Louise
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Louise clear sky chart from 2005-11-06 to 2024-11-05.

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	7% 16% 6% 12% 7% 5% 5% 4 5% 6% 26%	105815
	Night	5% 15% 6% 13% 7% 6% 5% 4 6% 7% 25%	101773
Transparency	Day	29% 49% 7% 9% 5% 1	105571
	Night	29% 49% 8% 8% 5% 1	101664
Seeing	Day	16% 16% 29% 24% 12% 3	15425
	Night	10% 12% 32% 31% 13% 2	24183

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	1 16% 8% 23% 16% 11% 6% 4 4 3 8%	2219
	11th to 20th	Day	2 15% 7% 14% 9% 6% 5% 4 3 6% 30%	2388
	21st to end	Day	4 25% 11% 16% 7% 5% 4 3 5% 6% 13%	2794
February	1st to 10th	Day	2 15% 8% 20% 10% 8% 6% 4 4 6% 17%	1520
	11th to 20th	Day	1 15% 8% 23% 9% 5% 4 4 4 7% 18%	1603
	21st to end	Day	1 12% 10% 20% 13% 10% 5% 4 4 4 17%	1570
March	1st to 10th	Day	13% 9% 25% 12% 6% 5% 4 4 5% 18%	3138
	11th to 20th	Day	2 15% 10% 16% 7% 4 4 2 5% 5% 30%	3326
	21st to end	Day	2 21% 13% 21% 8% 5% 3 3 4 4 16%	4056
April	1st to 10th	Day	4 22% 11% 20% 8% 6% 4 3 4 4 13%	2280
	11th to 20th	Day	5% 24% 8% 15% 8% 5% 4 4 4 5% 17%	2421
	21st to end	Day	7% 26% 9% 13% 6% 5% 4 3 4 5% 17%	2487
May	1st to 10th	Day	10% 24% 6% 10% 5% 5% 4 3 5% 5% 22%	4420
	11th to 20th	Day	10% 19% 6% 10% 6% 6% 4 3 6% 8% 23%	4617
	21st to end	Day	13% 29% 6% 12% 5% 4 4 3 5% 5% 16%	5161
June	1st to 10th	Day	17% 18% 5% 9% 6% 5% 5% 4 5% 6% 20%	2850
	11th to 20th	Day	19% 18% 5% 9% 7% 5% 6% 4 5% 5% 15%	2851
	21st to end	Day	13% 12% 5% 10% 7% 6% 5% 4 7% 5% 26%	3040
July	1st to 10th	Day	9% 8% 2 7% 6% 5% 4 4 5% 6% 45%	4740
	11th to 20th	Day	7% 6% 2 6% 5% 4 4 4 6% 7% 51%	4740
	21st to end	Day	8% 6% 2 7% 6% 5% 6% 5% 6% 8% 40%	4853
August	1st to 10th	Day	7% 7% 2 7% 6% 5% 7% 5% 6% 9% 39%	4401
	11th to 20th	Day	10% 7% 3 8% 6% 6% 6% 5% 7% 7% 34%	4219
	21st to end	Day	12% 12% 3 8% 5% 5% 5% 4 6% 8% 33%	4500
September	1st to 10th	Day	12% 11% 3 8% 5% 4 4 3 5% 7% 37%	2280
	11th to 20th	Day	13% 15% 4 7% 4 4 4 3 5% 6% 35%	2152
	21st to end	Day	12% 18% 3 9% 6% 4 4 3 6% 5% 30%	2090
October	1st to 10th	Day	8% 21% 6% 9% 5% 4 4 4 6% 7% 25%	3360
	11th to 20th	Day	10% 19% 8% 8% 4 4 5% 4 6% 8% 24%	2842
	21st to end	Day	4 16% 8% 15% 5% 5% 6% 4 6% 7% 25%	3101
November	1st to 10th	Day	4 21% 7% 16% 8% 7% 6% 4 5% 6% 15%	1677
	11th to 20th	Day	2 15% 7% 16% 8% 7% 7% 6% 6% 7% 21%	1335
	21st to end	Day	3 16% 5% 16% 9% 6% 5% 6% 7% 7% 20%	1330
December	1st to 10th	Day	2 13% 7% 16% 11% 9% 7% 4 5% 5% 22%	1330
	11th to 20th	Day	4 20% 8% 15% 10% 9% 5% 4 6% 4 14%	1682
	21st to end	Day	2 21% 7% 13% 6% 6% 6% 5% 7% 7% 19%	2442
January	1st to 10th	Night	2 18% 10% 27% 13% 8% 5% 3 3 3 8%	4726
	11th to 20th	Night	1 14% 5% 15% 10% 8% 4 5% 8% 7% 24%	4539
	21st to end	Night	6% 28% 10% 15% 9% 5% 5% 3 4 4 10%	4862
February	1st to 10th	Night	2 15% 9% 20% 11% 8% 5% 4 5% 5% 14%	2660
	11th to 20th	Night	3 14% 7% 22% 8% 6% 5% 4 5% 7% 19%	2458
	21st to end	Night	1 13% 9% 18% 10% 8% 6% 4 4 6% 21%	1884
March	1st to 10th	Night	1 11% 8% 19% 12% 8% 8% 6% 6% 6% 16%	3736
	11th to 20th	Night	1 13% 9% 14% 7% 6% 6% 4 7% 10% 23%	3652
	21st to end	Night	2 18% 14% 19% 7% 5% 4 4 5% 6% 17%	3595
April	1st to 10th	Night	4 18% 8% 16% 7% 6% 5% 4 6% 7% 19%	1900
	11th to 20th	Night	2 15% 6% 13% 7% 6% 7% 5% 8% 8% 24%	1710
	21st to end	Night	4 17% 5% 11% 6% 7% 6% 5% 6% 7% 27%	1691
May	1st to 10th	Night	9% 19% 6% 10% 5% 4 4 3 4 5% 29%	2540
	11th to 20th	Night	8% 14% 4 11% 5% 6% 6% 5% 7% 8% 27%	2274
	21st to end	Night	10% 24% 5% 9% 4 5% 5% 4 4 6% 23%	2414
June	1st to 10th	Night	15% 15% 3 8% 5% 5% 5% 3 6% 5% 30%	1330
	11th to 20th	Night	13% 16% 3 8% 6% 6% 5% 5% 7% 7% 23%	1319
	21st to end	Night	8% 7% 2 6% 4 6% 6% 6% 8% 10% 38%	1140
July	1st to 10th	Night	8% 6% 1 4 3 3 4 4 6% 7% 53%	2210
	11th to 20th	Night	5% 5% 2 4 4 3 4 3 6% 9% 56%	2220
	21st to end	Night	6% 9% 2 4 3 3 4 3 5% 8% 52%	2695
August	1st to 10th	Night	8% 6% 3 6% 4 5% 5% 4 6% 10% 44%	2529
	11th to 20th	Night	9% 6% 2 6% 3 4 5% 4 7% 9% 45%	2611
	21st to end	Night	10% 10% 3 7% 4 4 4 3 5% 8% 41%	3167
September	1st to 10th	Night	8% 8% 3 6% 5% 5% 4 5% 6% 8% 42%	1900
	11th to 20th	Night	11% 13% 3 6% 4 4 5% 3 7% 6% 38%	2028
	21st to end	Night	9% 15% 3 6% 4 4 4 5% 7% 7% 35%	2090
October	1st to 10th	Night	6% 16% 4 9% 6% 5% 5% 4 7% 8% 31%	3603
	11th to 20th	Night	6% 17% 8% 10% 5% 5% 4 3 5% 7% 29%	4086
	21st to end	Night	5% 19% 9% 12% 6% 5% 6% 4 6% 6% 23%	4457
November	1st to 10th	Night	5% 21% 9% 18% 9% 6% 5% 4 5% 5% 13%	2482
	11th to 20th	Night	2 16% 9% 18% 11% 7% 7% 4 5% 5% 16%	2841
	21st to end	Night	2 17% 7% 19% 10% 7% 7% 5% 6% 5% 16%	2850
December	1st to 10th	Night	2 15% 6% 16% 11% 8% 6% 4 5% 6% 19%	2850
	11th to 20th	Night	5% 18% 7% 17% 13% 10% 7% 4 6% 4 9%	3510
	21st to end	Night	4 16% 7% 14% 9% 9% 8% 5% 7% 7% 15%	5214

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	49% 42% 5% 2 1 1	2219
	11th to 20th	Day	33% 38% 6% 6% 10% 7%	2412
	21st to end	Day	43% 45% 7% 4 1	2794
February	1st to 10th	Day	23% 67% 4 2 3 1	1520
	11th to 20th	Day	24% 65% 4 3 3	1611
	21st to end	Day	23% 65% 2 5% 4 1	1570
March	1st to 10th	Day	39% 42% 5% 6% 8% 1	3138
	11th to 20th	Day	27% 44% 15% 11% 3	3327
	21st to end	Day	39% 45% 5% 6% 5% 1	4056
April	1st to 10th	Day	26% 66% 5% 3 1	2280
	11th to 20th	Day	22% 67% 5% 4 1	2421
	21st to end	Day	24% 66% 4 6% 1	2487
May	1st to 10th	Day	36% 42% 8% 11% 3	4420
	11th to 20th	Day	34% 43% 10% 10% 3	4621
	21st to end	Day	41% 43% 9% 5% 2	5162
June	1st to 10th	Day	20% 67% 4 8% 2	2850
	11th to 20th	Day	24% 66% 3 5% 2	2851
	21st to end	Day	23% 65% 4 5% 3	3040
July	1st to 10th	Day	21% 39% 4 12% 21% 3	4666
	11th to 20th	Day	16% 38% 6% 20% 19% 1	4659
	21st to end	Day	25% 40% 7% 13% 13% 2	4700
August	1st to 10th	Day	22% 43% 8% 21% 6%	4384
	11th to 20th	Day	29% 44% 10% 14% 2	4261
	21st to end	Day	30% 41% 15% 11% 3	4499
September	1st to 10th	Day	22% 60% 7% 8% 3	2280
	11th to 20th	Day	24% 60% 4 9% 3	2152
	21st to end	Day	25% 61% 5% 7% 2	2090
October	1st to 10th	Day	38% 41% 12% 6% 3	3360
	11th to 20th	Day	37% 40% 11% 11% 1	2842
	21st to end	Day	34% 42% 10% 12% 3	3101
November	1st to 10th	Day	30% 61% 5% 3 2	1677
	11th to 20th	Day	22% 63% 8% 3 4	1335
	21st to end	Day	20% 65% 6% 5% 3 2	1330
December	1st to 10th	Day	25% 62% 5% 5% 3	1330
	11th to 20th	Day	37% 52% 6% 3 2	1684
	21st to end	Day	32% 40% 11% 7% 8% 2	2442
January	1st to 10th	Night	54% 39% 3 2 2 1	4726
	11th to 20th	Night	30% 39% 5% 6% 12% 7%	4577
	21st to end	Night	48% 44% 4 2 2	4862
February	1st to 10th	Night	25% 65% 3 3 4 1	2660
	11th to 20th	Night	22% 65% 4 3 4 1	2460
	21st to end	Night	19% 66% 4 5% 4 2	1884
March	1st to 10th	Night	30% 48% 9% 6% 7%	3736
	11th to 20th	Night	25% 45% 15% 12% 3 1	3652
	21st to end	Night	40% 43% 6% 6% 4 1	3595
April	1st to 10th	Night	18% 68% 7% 5% 2	1900
	11th to 20th	Night	17% 68% 7% 5% 3	1710
	21st to end	Night	19% 66% 6% 6% 3	1691
May	1st to 10th	Night	35% 42% 7% 14% 3	2540
	11th to 20th	Night	34% 45% 7% 10% 4	2274
	21st to end	Night	37% 43% 10% 9% 1	2414
June	1st to 10th	Night	14% 67% 5% 12% 2	1330
	11th to 20th	Night	18% 66% 5% 7% 4	1319
	21st to end	Night	13% 66% 6% 10% 5%	1140
July	1st to 10th	Night	18% 37% 6% 17% 19% 3	2175
	11th to 20th	Night	12% 37% 6% 23% 21% 1	2178
	21st to end	Night	21% 36% 9% 18% 14% 1	2610
August	1st to 10th	Night	21% 42% 8% 23% 5%	2521
	11th to 20th	Night	22% 41% 19% 16% 2	2635
	21st to end	Night	28% 39% 19% 11% 2	3167
September	1st to 10th	Night	18% 61% 8% 9% 4	1900
	11th to 20th	Night	21% 61% 5% 8% 4	2028
	21st to end	Night	21% 62% 8% 8% 2	2090
October	1st to 10th	Night	32% 44% 14% 7% 3	3603
	11th to 20th	Night	36% 40% 11% 12% 1	4086
	21st to end	Night	35% 42% 8% 12% 2	4457
November	1st to 10th	Night	31% 59% 4 4 2	2482
	11th to 20th	Night	26% 63% 5% 2 3 1	2841
	21st to end	Night	24% 63% 5% 4 2 2	2850
December	1st to 10th	Night	26% 62% 3 4 4	2850
	11th to 20th	Night	35% 56% 4 3 2	3507
	21st to end	Night	31% 42% 14% 5% 7% 2	5214

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	6% 20% 27% 28% 13% 6%	180
	11th to 20th	Day	3 19% 36% 29% 11% 2	180
	21st to end	Day	8% 20% 39% 21% 9% 3	198
February	1st to 10th	Day	14% 23% 35% 19% 5% 4	180
	11th to 20th	Day	8% 20% 33% 26% 11% 2	261
	21st to end	Day	9% 21% 33% 26% 9% 2	382
March	1st to 10th	Day	12% 26% 32% 18% 10% 3	460
	11th to 20th	Day	11% 23% 34% 20% 9% 2	460
	21st to end	Day	12% 22% 30% 23% 10% 2	506
April	1st to 10th	Day	14% 23% 36% 19% 8%	460
	11th to 20th	Day	13% 22% 30% 23% 10% 3	452
	21st to end	Day	16% 22% 28% 21% 10% 3	460
May	1st to 10th	Day	19% 13% 30% 25% 10% 3	463
	11th to 20th	Day	14% 10% 23% 26% 20% 7%	624
	21st to end	Day	22% 10% 18% 26% 19% 5%	734
June	1st to 10th	Day	22% 12% 25% 25% 14% 2	680
	11th to 20th	Day	26% 10% 26% 22% 12% 3	681
	21st to end	Day	16% 10% 23% 29% 16% 6%	870
July	1st to 10th	Day	14% 9% 22% 28% 23% 4	671
	11th to 20th	Day	18% 8% 25% 27% 18% 4	668
	21st to end	Day	13% 11% 30% 24% 16% 5%	568
August	1st to 10th	Day	13% 12% 31% 28% 14% 3	487
	11th to 20th	Day	13% 16% 31% 25% 12% 3	477
	21st to end	Day	21% 16% 31% 20% 11% 1	539
September	1st to 10th	Day	25% 17% 27% 19% 10% 2	490
	11th to 20th	Day	22% 15% 29% 24% 8% 1	490
	21st to end	Day	31% 20% 24% 17% 6% 1	490
October	1st to 10th	Day	26% 16% 26% 20% 9% 3	481
	11th to 20th	Day	19% 20% 28% 21% 11% 1	300
	21st to end	Day	15% 21% 32% 23% 7% 2	330
November	1st to 10th	Day	13% 19% 36% 22% 7% 3	282
	11th to 20th	Day	14% 23% 39% 17% 5% 1	183
	21st to end	Day	7% 27% 31% 19% 9% 7%	180
December	1st to 10th	Day	7% 18% 31% 27% 9% 8%	180
	11th to 20th	Day	6% 21% 38% 27% 8% 1	180
	21st to end	Day	7% 11% 32% 31% 16% 3	198
January	1st to 10th	Night	8% 19% 39% 26% 6% 2	950
	11th to 20th	Night	7% 16% 41% 29% 5% 2	852
	21st to end	Night	7% 15% 40% 29% 7% 2	836
February	1st to 10th	Night	8% 14% 38% 22% 13% 5%	760
	11th to 20th	Night	9% 12% 36% 29% 12% 2	744
	21st to end	Night	5% 10% 34% 32% 16% 3	628
March	1st to 10th	Night	5% 13% 40% 28% 12% 1	760
	11th to 20th	Night	6% 17% 34% 31% 10% 1	760
	21st to end	Night	6% 11% 32% 33% 15% 3	836
April	1st to 10th	Night	7% 13% 30% 33% 15% 2	760
	11th to 20th	Night	8% 10% 36% 33% 13% 1	582
	21st to end	Night	12% 13% 25% 34% 15% 2	551
May	1st to 10th	Night	11% 7% 23% 37% 20% 2	380
	11th to 20th	Night	10% 7% 18% 35% 26% 5%	374
	21st to end	Night	15% 7% 20% 28% 26% 4	411
June	1st to 10th	Night	18% 9% 22% 31% 17% 3	380
	11th to 20th	Night	17% 8% 24% 33% 16% 2	380
	21st to end	Night	11% 5% 20% 32% 30% 3	380
July	1st to 10th	Night	11% 3 16% 42% 27% 2	370
	11th to 20th	Night	13% 4 17% 39% 25% 1	368
	21st to end	Night	6% 3 15% 45% 28% 2	416
August	1st to 10th	Night	9% 2 12% 41% 32% 3	378
	11th to 20th	Night	11% 5% 15% 41% 25% 3	438
	21st to end	Night	14% 5% 23% 40% 17% 2	635
September	1st to 10th	Night	15% 7% 23% 31% 19% 4	760
	11th to 20th	Night	17% 7% 20% 33% 19% 4	760
	21st to end	Night	19% 12% 26% 28% 14% 3	760
October	1st to 10th	Night	17% 9% 25% 34% 14% 2	760
	11th to 20th	Night	15% 10% 30% 33% 10% 2	760
	21st to end	Night	13% 15% 33% 28% 10% 1	836
November	1st to 10th	Night	14% 15% 38% 24% 8% 1	773
	11th to 20th	Night	11% 19% 40% 25% 4 1	950
	21st to end	Night	8% 16% 40% 26% 7% 2	950
December	1st to 10th	Night	7% 13% 40% 28% 9% 3	950
	11th to 20th	Night	7% 13% 42% 28% 7% 2	950
	21st to end	Night	5% 12% 43% 29% 8% 2	1045

Page generated at 2024-11-03 00:11:10. Version ac07

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