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 2024-01-12.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
34%
23222
8%
74695
6%
23183
36%
23183
13%
57129

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
21%
948
5%
2836
3%
946
23%
946
7%
2455
January11th to 20thNight
23%
815
8%
2629
6%
815
26%
815
8%
2186
January21st to endNight
24%
792
9%
2772
6%
792
28%
792
9%
2235
February1st to 10thNight
21%
720
6%
2520
5%
720
24%
720
8%
2085
February11th to 20thNight
24%
701
7%
2326
5%
700
28%
700
9%
1894
February21st to endNight
36%
592
11%
1776
9%
592
39%
592
13%
1400
March1st to 10thNight
28%
720
9%
2160
7%
720
31%
720
12%
1761
March11th to 20thNight
28%
720
10%
2077
6%
720
31%
720
12%
1673
March21st to endNight
31%
792
6%
2048
3%
792
32%
792
11%
1719
April1st to 10thNight
32%
720
6%
1800
3%
720
33%
720
12%
1482
April11th to 20thNight
33%
551
8%
1619
6%
551
35%
551
14%
1260
April21st to endNight
40%
522
8%
1602
7%
522
41%
522
14%
1212
May1st to 10thNight
46%
360
6%
1440
10%
360
48%
360
12%
1051
May11th to 20thNight
59%
354
9%
1286
11%
354
60%
354
20%
826
May21st to endNight
48%
388
4%
1358
3%
388
49%
388
16%
976
June1st to 10thNight
43%
360
1%
1260
0%
360
43%
360
15%
921
June11th to 20thNight
43%
360
0%
1250
0%
360
43%
360
11%
980
June21st to endNight
59%
360
0%
1080
0%
360
59%
360
25%
709
July1st to 10thNight
63%
350
2%
1215
0%
350
63%
350
26%
740
July11th to 20thNight
54%
348
5%
1218
3%
348
55%
348
22%
784
July21st to endNight
71%
394
12%
1452
16%
372
74%
372
35%
723
August1st to 10thNight
70%
358
13%
1424
19%
356
73%
356
26%
794
August11th to 20thNight
62%
414
18%
1482
22%
414
64%
414
28%
830
August21st to endNight
52%
601
17%
1789
15%
601
54%
601
26%
1171
September1st to 10thNight
46%
720
14%
1800
8%
720
48%
720
27%
1260
September11th to 20thNight
49%
720
13%
1921
9%
720
50%
720
23%
1370
September21st to endNight
39%
720
14%
1980
9%
720
43%
720
20%
1426
October1st to 10thNight
41%
720
11%
2041
9%
720
44%
720
19%
1480
October11th to 20thNight
34%
720
8%
2340
6%
720
38%
720
14%
1771
October21st to endNight
28%
792
8%
2574
6%
792
31%
792
11%
2017
November1st to 10thNight
20%
753
6%
2418
4%
753
22%
753
7%
2062
November11th to 20thNight
18%
950
6%
2841
3%
950
21%
950
8%
2412
November21st to endNight
22%
950
6%
2850
3%
950
24%
950
10%
2354
December1st to 10thNight
27%
950
10%
2850
7%
950
29%
950
11%
2308
December11th to 20thNight
22%
950
4%
3507
2%
949
24%
949
6%
3074
December21st to endNight
21%
1037
4%
5154
4%
1026
24%
1026
5%
3728

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 ForecastData
Points
Cloud CoverDay
9%15%7%11%8%45%5%5%6%24%
74764
Night
5%13%7%12%9%5%6%6%6%7%24%
74926
TransparencyDay
59%9%12%13%6%1
74454
Night
56%10%13%13%7%1
74755
SeeingDay
16%16%28%24%12%3
14251
Night
10%12%32%31%13%2
23236

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
116%10%17%12%9%8%6%5%5%12%
1329
11th to 20thDay
315%10%11%12%6%7%6%48%19%
1375
21st to endDay
112%8%16%11%6%7%7%7%8%18%
1584
February1st to 10thDay
213%9%18%12%6%7%6%46%17%
1440
11th to 20thDay
214%10%22%10%45%5%47%17%
1517
21st to endDay
210%9%19%15%8%7%44418%
1480
March1st to 10thDay
115%10%19%12%5%7%5%5%5%17%
1800
11th to 20thDay
217%11%17%9%45%45%6%20%
1881
21st to endDay
325%12%16%11%45%445%12%
2306
April1st to 10thDay
5%19%12%19%10%5%5%34413%
2160
11th to 20thDay
6%22%9%13%9%45%5%46%17%
2292
21st to endDay
8%24%10%12%6%44445%18%
2356
May1st to 10thDay
8%24%8%10%6%45%45%6%21%
2520
11th to 20thDay
9%15%5%8%7%45%5%5%7%29%
2605
21st to endDay
17%19%48%7%345%5%5%23%
2917
June1st to 10thDay
18%16%6%8%7%45%5%5%6%20%
2700
11th to 20thDay
21%17%6%8%7%46%5%5%5%15%
2700
21st to endDay
12%12%5%9%7%46%5%7%6%27%
2880
July1st to 10thDay
13%9%38%8%45%5%5%8%33%
2700
11th to 20thDay
13%9%47%6%45%45%7%35%
2700
21st to endDay
9%6%37%6%45%5%6%7%43%
2776
August1st to 10thDay
10%8%37%6%46%6%5%7%38%
2507
11th to 20thDay
11%7%36%6%35%5%6%8%41%
2416
21st to endDay
13%12%48%6%45%45%7%34%
2566
September1st to 10thDay
13%12%37%6%3445%7%35%
2160
11th to 20thDay
13%14%46%5%3445%6%35%
2039
21st to endDay
12%18%48%7%3445%5%30%
1980
October1st to 10thDay
11%16%6%9%7%345%45%29%
1916
11th to 20thDay
8%17%7%8%7%35%6%6%8%25%
1620
21st to endDay
6%17%7%12%6%46%6%7%7%22%
1782
November1st to 10thDay
419%8%14%10%47%6%5%6%15%
1641
11th to 20thDay
213%8%13%10%5%7%7%6%7%21%
1335
21st to endDay
315%6%15%9%5%5%6%7%7%20%
1330
December1st to 10thDay
311%8%15%12%7%8%5%6%5%22%
1330
11th to 20thDay
5%18%9%13%12%7%6%5%6%414%
1682
21st to endDay
320%7%11%8%47%6%7%8%19%
2442
January1st to 10thNight
216%10%19%14%6%7%5%45%12%
2836
11th to 20thNight
315%8%15%14%6%7%5%7%6%14%
2629
21st to endNight
112%9%16%14%6%8%6%6%6%15%
2772
February1st to 10thNight
213%10%18%13%6%7%5%5%6%15%
2520
11th to 20thNight
313%8%21%10%5%6%5%5%7%18%
2324
21st to endNight
110%9%16%12%7%8%5%46%22%
1776
March1st to 10thNight
212%10%16%11%5%7%7%5%6%19%
2160
11th to 20thNight
214%10%13%9%5%6%6%6%8%21%
2077
21st to endNight
215%10%17%8%47%5%5%7%19%
2048
April1st to 10thNight
415%9%15%9%5%5%6%6%8%20%
1800
11th to 20thNight
314%7%11%9%47%6%7%8%24%
1619
21st to endNight
5%15%6%9%6%5%7%6%5%7%28%
1602
May1st to 10thNight
7%17%5%8%6%36%5%5%6%32%
1440
11th to 20thNight
7%7%37%5%46%6%7%9%38%
1286
21st to endNight
14%13%46%435%6%6%8%32%
1358
June1st to 10thNight
16%12%46%5%45%5%6%6%31%
1260
11th to 20thNight
14%15%47%7%46%5%7%8%23%
1250
21st to endNight
9%6%25%45%5%8%8%10%38%
1080
July1st to 10thNight
9%6%244347%7%9%47%
1250
11th to 20thNight
10%9%26%6%345%5%8%42%
1260
21st to endNight
45%2433445%8%58%
1537
August1st to 10thNight
7%5%24445%6%6%8%50%
1432
11th to 20thNight
8%5%35%425%46%9%50%
1482
21st to endNight
8%8%36%5%35%46%8%43%
1789
September1st to 10thNight
9%9%35%6%45%6%6%8%41%
1800
11th to 20thNight
11%12%36%5%35%47%6%38%
1921
21st to endNight
9%14%35%5%35%6%7%7%36%
1980
October1st to 10thNight
8%15%49%6%4446%7%34%
2041
11th to 20thNight
6%14%6%9%8%5%6%5%6%6%28%
2340
21st to endNight
5%17%7%13%9%36%5%6%8%21%
2574
November1st to 10thNight
6%20%9%16%10%5%6%5%5%6%13%
2418
11th to 20thNight
214%11%16%13%5%7%6%5%5%16%
2841
21st to endNight
215%9%18%11%5%7%7%6%5%16%
2850
December1st to 10thNight
214%7%13%14%6%7%6%5%6%19%
2850
11th to 20thNight
5%17%8%15%15%8%8%5%6%49%
3510
21st to endNight
415%7%12%11%6%9%7%7%7%15%
5214

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
69%12%8%7%31
1329
11th to 20thDay
62%11%10%10%5%2
1375
21st to endDay
57%13%14%8%6%1
1584
February1st to 10thDay
66%9%10%5%7%3
1440
11th to 20thDay
67%8%10%9%5%1
1525
21st to endDay
67%9%8%9%5%2
1480
March1st to 10thDay
68%9%10%8%5%1
1800
11th to 20thDay
65%9%10%10%6%
1882
21st to endDay
74%8%8%6%3
2306
April1st to 10thDay
74%7%11%6%2
2160
11th to 20thDay
68%8%11%9%31
2292
21st to endDay
69%8%10%11%21
2356
May1st to 10thDay
64%9%12%12%2
2520
11th to 20thDay
53%10%16%15%6%
2609
21st to endDay
61%8%15%12%4
2918
June1st to 10thDay
63%9%12%12%31
2700
11th to 20thDay
68%9%10%10%3
2700
21st to endDay
55%10%14%14%6%1
2880
July1st to 10thDay
50%9%13%18%10%1
2626
11th to 20thDay
48%8%13%21%9%
2619
21st to endDay
40%7%12%27%14%1
2622
August1st to 10thDay
46%8%16%20%9%1
2490
11th to 20thDay
42%9%17%21%11%
2416
21st to endDay
49%7%13%21%8%1
2566
September1st to 10thDay
48%8%17%19%8%1
2160
11th to 20thDay
50%7%12%20%10%
2039
21st to endDay
55%8%14%17%7%
1980
October1st to 10thDay
56%8%11%18%6%
1916
11th to 20thDay
56%11%15%14%3
1620
21st to endDay
59%11%14%9%6%1
1782
November1st to 10thDay
67%11%10%8%31
1641
11th to 20thDay
59%11%15%8%7%
1335
21st to endDay
57%12%14%9%6%2
1330
December1st to 10thDay
62%10%9%11%7%1
1330
11th to 20thDay
65%12%11%6%5%1
1684
21st to endDay
55%10%15%9%9%2
2442
January1st to 10thNight
71%9%8%6%42
2836
11th to 20thNight
64%11%9%9%5%2
2629
21st to endNight
62%11%10%8%7%2
2772
February1st to 10thNight
68%8%8%7%7%3
2520
11th to 20thNight
64%9%12%9%6%1
2326
21st to endNight
62%6%10%11%8%3
1776
March1st to 10thNight
61%10%12%8%8%1
2160
11th to 20thNight
60%10%12%11%6%1
2077
21st to endNight
63%11%10%10%5%
2048
April1st to 10thNight
61%10%16%10%4
1800
11th to 20thNight
56%11%16%10%6%1
1619
21st to endNight
54%10%16%15%41
1602
May1st to 10thNight
53%11%14%17%6%
1440
11th to 20thNight
39%12%20%20%9%
1286
21st to endNight
50%10%16%18%6%
1358
June1st to 10thNight
53%9%12%21%5%1
1260
11th to 20thNight
58%11%14%13%4
1250
21st to endNight
35%14%22%23%7%1
1080
July1st to 10thNight
33%12%16%28%11%1
1215
11th to 20thNight
41%9%15%25%10%
1218
21st to endNight
25%8%15%36%15%1
1452
August1st to 10thNight
30%11%20%29%9%
1424
11th to 20thNight
31%9%20%32%8%
1482
21st to endNight
39%9%16%26%9%1
1789
September1st to 10thNight
40%10%18%23%9%1
1800
11th to 20thNight
45%10%17%18%10%1
1921
21st to endNight
44%12%17%19%8%
1980
October1st to 10thNight
50%8%15%21%7%
2041
11th to 20thNight
55%9%14%15%6%
2340
21st to endNight
60%9%14%12%5%
2574
November1st to 10thNight
70%8%9%6%5%2
2418
11th to 20thNight
67%10%9%7%6%1
2841
21st to endNight
63%10%11%8%43
2850
December1st to 10thNight
62%10%9%9%9%1
2850
11th to 20thNight
68%13%8%6%41
3507
21st to endNight
57%10%16%8%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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
6%20%27%28%13%6%
180
11th to 20thDay
420%35%28%11%2
162
21st to endDay
7%18%42%20%10%3
176
February1st to 10thDay
16%24%34%18%6%3
160
11th to 20thDay
9%22%35%26%9%1
235
21st to endDay
8%20%34%27%9%2
346
March1st to 10thDay
12%25%32%18%11%3
420
11th to 20thDay
12%24%34%20%8%3
420
21st to endDay
13%23%30%22%10%3
462
April1st to 10thDay
14%21%35%20%9%
420
11th to 20thDay
14%22%29%22%9%3
412
21st to endDay
18%21%28%20%10%4
420
May1st to 10thDay
19%13%30%25%10%3
423
11th to 20thDay
14%9%23%27%21%7%
576
21st to endDay
22%8%16%28%20%6%
679
June1st to 10thDay
23%10%23%26%15%3
630
11th to 20thDay
26%10%27%23%12%3
630
21st to endDay
16%10%23%29%16%6%
810
July1st to 10thDay
15%8%22%28%23%4
621
11th to 20thDay
19%8%25%27%17%4
618
21st to endDay
12%10%31%25%17%6%
522
August1st to 10thDay
13%12%30%29%13%2
447
11th to 20thDay
14%16%31%24%12%2
437
21st to endDay
20%16%30%22%11%2
495
September1st to 10thDay
27%18%26%18%10%1
450
11th to 20thDay
23%15%29%24%8%1
450
21st to endDay
28%20%26%18%6%2
450
October1st to 10thDay
24%16%26%21%9%3
442
11th to 20thDay
17%22%27%21%12%1
270
21st to endDay
15%21%32%23%6%2
297
November1st to 10thDay
12%19%36%23%7%3
270
11th to 20thDay
14%23%39%17%5%1
183
21st to endDay
7%27%31%19%9%7%
180
December1st to 10thDay
7%18%31%27%9%8%
180
11th to 20thDay
6%21%38%27%8%1
180
21st to endDay
7%11%32%31%16%3
198
January1st to 10thNight
8%19%39%26%6%2
950
11th to 20thNight
7%17%41%29%5%2
815
21st to endNight
6%15%41%29%7%2
792
February1st to 10thNight
9%14%38%22%12%5%
720
11th to 20thNight
9%13%37%30%10%2
704
21st to endNight
49%35%33%17%3
592
March1st to 10thNight
6%13%39%28%13%1
720
11th to 20thNight
7%18%33%30%10%1
720
21st to endNight
6%12%32%32%15%4
792
April1st to 10thNight
7%12%30%34%16%2
720
11th to 20thNight
8%10%36%32%14%1
551
21st to endNight
12%13%24%34%15%2
522
May1st to 10thNight
11%7%23%37%21%3
360
11th to 20thNight
10%6%18%34%27%5%
354
21st to endNight
16%6%20%28%26%4
389
June1st to 10thNight
18%8%22%31%18%4
360
11th to 20thNight
18%8%23%33%16%2
360
21st to endNight
11%5%19%31%31%3
360
July1st to 10thNight
11%216%42%27%2
350
11th to 20thNight
14%418%38%24%1
348
21st to endNight
6%215%46%29%2
394
August1st to 10thNight
8%213%41%32%3
358
11th to 20thNight
11%6%15%40%25%3
414
21st to endNight
13%5%22%40%17%2
601
September1st to 10thNight
16%7%24%30%19%4
720
11th to 20thNight
17%7%20%33%20%5%
720
21st to endNight
18%11%25%29%14%3
720
October1st to 10thNight
17%8%24%35%14%2
720
11th to 20thNight
14%10%31%33%11%2
720
21st to endNight
13%15%33%28%10%1
792
November1st to 10thNight
14%15%38%24%8%1
753
11th to 20thNight
11%19%40%25%41
950
21st to endNight
8%16%40%26%7%2
950
December1st to 10thNight
7%13%40%28%9%3
950
11th to 20thNight
7%13%42%28%7%2
950
21st to endNight
5%12%43%29%8%2
1045
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Copyright 2024 Attilla Danko


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