Lake Louise
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Louise clear sky chart from 2005-11-05 to 2017-09-16.

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
31%
15039
7%
46648
5%
15012
33%
15012
11%
36498

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 15thNight
19%
895
5%
2683
3%
893
20%
893
6%
2381
January16th to endNight
21%
768
7%
2688
6%
768
24%
768
7%
2227
February1st to 15thNight
20%
701
5%
2464
4%
700
22%
700
7%
2061
February16th to endNight
32%
632
7%
1932
7%
632
35%
632
11%
1548
March1st to 15thNight
20%
720
6%
2160
3%
720
23%
720
7%
1857
March16th to endNight
26%
768
6%
2029
3%
768
28%
768
9%
1727
April1st to 15thNight
31%
671
5%
1751
3%
671
32%
671
12%
1434
April16th to endNight
33%
528
7%
1608
4%
528
35%
528
10%
1270
May1st to 15thNight
46%
359
7%
1410
9%
359
49%
359
14%
955
May16th to endNight
42%
374
3%
1309
2%
374
42%
374
12%
982
June1st to 15thNight
40%
360
0%
1260
0%
360
40%
360
11%
966
June16th to endNight
44%
360
0%
1133
0%
360
44%
360
16%
811
July1st to 15thNight
53%
340
1%
1184
0%
340
53%
340
21%
741
July16th to endNight
56%
376
8%
1335
8%
354
64%
354
26%
753
August1st to 15thNight
65%
360
13%
1432
17%
358
69%
358
23%
803
August16th to endNight
51%
559
18%
1705
15%
559
54%
559
27%
1032
September1st to 15thNight
46%
720
13%
1821
7%
720
48%
720
26%
1242
September16th to endNight
42%
656
14%
1816
8%
656
46%
656
22%
1260
October1st to 15thNight
33%
660
10%
1963
8%
660
37%
660
14%
1490
October16th to endNight
29%
704
8%
2288
6%
704
33%
704
11%
1816
November1st to 15thNight
17%
768
6%
2397
4%
768
19%
768
7%
2073
November16th to endNight
19%
900
6%
2700
2%
900
22%
900
7%
2286
December1st to 15thNight
23%
900
8%
2700
5%
900
25%
900
8%
2274
December16th to endNight
19%
960
4%
2880
2%
960
22%
960
5%
2509

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%45%6%22%
48113
Night
5%12%7%12%9%46%5%5%6%24%
46802
TransparencyDay
62%9%11%11%4
47773
Night
57%10%12%13%5%
46648
SeeingDay
19%19%26%20%11%3
6087
Night
10%21%25%26%13%2
15047

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 15thDay
317%10%14%10%7%7%5%3415%
1265
16th to endDay
212%9%14%11%5%7%5%5%8%17%
1536
February1st to 15thDay
313%8%17%12%5%5%5%35%17%
1400
16th to endDay
110%10%18%12%6%6%5%45%16%
1540
March1st to 15thDay
118%11%15%9%47%45%5%15%
1800
16th to endDay
323%12%16%10%35%45%5%9%
2193
April1st to 15thDay
6%22%12%15%8%4434411%
2197
16th to endDay
8%23%9%13%7%3444416%
2352
May1st to 15thDay
8%21%7%8%5%3435%7%24%
2539
16th to endDay
17%17%5%8%7%35%5%5%5%18%
2802
June1st to 15thDay
21%17%6%8%7%44435%16%
2700
16th to endDay
17%13%6%10%7%46%5%5%5%19%
2820
July1st to 15thDay
14%9%38%7%45%45%7%28%
2700
16th to endDay
12%7%37%7%35%5%5%7%34%
2739
August1st to 15thDay
11%8%37%6%46%5%5%6%33%
2520
16th to endDay
12%10%36%6%3445%7%36%
2496
September1st to 15thDay
12%13%36%5%23445%37%
2139
16th to endDay
15%12%48%5%2435%5%31%
1816
October1st to 15thDay
10%17%6%9%8%25%6%5%6%20%
1665
16th to endDay
7%15%6%10%6%36%5%7%7%23%
1584
November1st to 15thDay
316%8%14%10%47%6%6%6%14%
1446
16th to endDay
312%6%13%9%5%6%6%6%6%21%
1260
December1st to 15thDay
211%8%16%11%7%7%5%6%419%
1260
16th to endDay
212%9%15%12%6%7%5%5%7%15%
1344
January1st to 15thNight
316%10%17%14%6%6%44410%
2683
16th to endNight
212%9%15%14%5%7%5%5%5%16%
2688
February1st to 15thNight
314%10%18%12%46%346%15%
2452
16th to endNight
19%7%17%11%6%7%5%46%22%
1932
March1st to 15thNight
214%11%15%10%5%7%6%5%6%14%
2160
16th to endNight
315%9%15%8%47%6%5%8%16%
2026
April1st to 15thNight
5%15%8%12%8%45%6%5%7%20%
1751
16th to endNight
413%6%11%7%5%6%6%5%8%24%
1608
May1st to 15thNight
7%12%47%5%25%45%7%37%
1409
16th to endNight
13%10%36%437%6%6%9%28%
1309
June1st to 15thNight
15%11%47%6%45%5%6%6%25%
1260
16th to endNight
11%9%3435%6%6%7%8%32%
1133
July1st to 15thNight
7%5%245%246%5%8%46%
1254
16th to endNight
5%5%1433446%8%51%
1427
August1st to 15thNight
6%425%3245%6%8%50%
1440
16th to endNight
7%42442435%8%50%
1705
September1st to 15thNight
8%9%35%5%2445%6%45%
1821
16th to endNight
11%8%24325%6%8%7%39%
1816
October1st to 15thNight
7%13%48%7%46%45%6%30%
1963
16th to endNight
5%15%6%13%8%45%6%5%7%22%
2288
November1st to 15thNight
417%10%16%11%45%45%5%12%
2397
16th to endNight
212%9%17%12%46%5%5%5%16%
2700
December1st to 15thNight
213%9%16%13%6%7%45%5%16%
2700
16th to endNight
111%9%16%16%6%7%6%6%5%10%
2880

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 15thDay
68%11%7%7%41
1265
16th to endDay
60%12%11%8%42
1536
February1st to 15thDay
67%8%10%6%5%1
1400
16th to endDay
66%9%10%7%5%
1540
March1st to 15thDay
69%10%9%7%2
1800
16th to endDay
76%8%8%5%1
2194
April1st to 15thDay
76%6%9%5%1
2197
16th to endDay
71%8%10%7%1
2352
May1st to 15thDay
59%8%15%11%4
2539
16th to endDay
68%7%12%8%2
2807
June1st to 15thDay
70%7%9%10%2
2700
16th to endDay
65%7%11%11%3
2820
July1st to 15thDay
56%8%11%14%8%
2541
16th to endDay
48%7%14%19%9%
2569
August1st to 15thDay
51%8%16%16%5%
2503
16th to endDay
47%7%15%22%6%1
2496
September1st to 15thDay
48%7%13%20%8%
2139
16th to endDay
53%7%12%18%6%
1816
October1st to 15thDay
62%9%10%12%4
1665
16th to endDay
56%13%14%12%2
1584
November1st to 15thDay
67%11%10%7%3
1446
16th to endDay
57%14%11%8%7%
1260
December1st to 15thDay
66%8%9%9%5%
1260
16th to endDay
63%13%11%45%1
1344
January1st to 15thNight
73%9%6%5%31
2683
16th to endNight
64%11%9%7%5%2
2688
February1st to 15thNight
69%6%9%6%42
2464
16th to endNight
61%8%10%11%6%1
1932
March1st to 15thNight
66%11%10%7%3
2160
16th to endNight
64%11%10%9%3
2029
April1st to 15thNight
59%11%15%9%3
1751
16th to endNight
57%11%16%10%3
1608
May1st to 15thNight
46%10%18%18%6%
1410
16th to endNight
51%12%16%15%3
1309
June1st to 15thNight
56%9%11%18%3
1260
16th to endNight
44%13%17%18%5%
1133
July1st to 15thNight
35%11%17%24%10%
1184
16th to endNight
30%9%16%29%13%
1335
August1st to 15thNight
29%11%20%31%5%
1432
16th to endNight
31%9%18%30%7%
1705
September1st to 15thNight
39%8%18%22%10%
1821
16th to endNight
40%11%17%21%8%
1816
October1st to 15thNight
53%10%13%15%7%
1963
16th to endNight
59%10%14%14%1
2288
November1st to 15thNight
70%9%8%6%4
2397
16th to endNight
65%11%8%7%42
2700
December1st to 15thNight
65%10%8%7%7%
2700
16th to endNight
70%9%8%6%3
2880

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 15thDay
6%25%38%15%15%
60
16th to endDay
7%343%26%12%6%
64
February1st to 15thDay
8%16%38%28%6%1
60
16th to endDay
6%21%30%31%11%
206
March1st to 15thDay
12%35%36%12%2
270
16th to endDay
14%25%31%22%4
288
April1st to 15thDay
15%28%32%16%6%
269
16th to endDay
18%26%27%14%10%2
270
May1st to 15thDay
18%19%24%24%10%1
316
16th to endDay
24%16%14%17%18%9%
517
June1st to 15thDay
27%18%17%20%12%4
495
16th to endDay
21%20%24%18%12%3
615
July1st to 15thDay
19%14%20%22%20%3
475
16th to endDay
19%21%25%21%9%1
408
August1st to 15thDay
19%13%27%25%11%2
315
16th to endDay
20%20%30%18%9%
332
September1st to 15thDay
28%17%26%17%8%1
315
16th to endDay
28%22%26%15%5%
256
October1st to 15thDay
22%26%26%17%6%1
195
16th to endDay
12%7%30%29%14%6%
96
November1st to 15thDay
8%14%46%25%21
81
16th to endDay
5%16%26%21%13%16%
60
December1st to 15thDay
8%6%30%23%18%13%
60
16th to endDay
339%35%21%
64
January1st to 15thNight
7%29%31%22%6%1
898
16th to endNight
9%25%30%23%9%2
768
February1st to 15thNight
10%24%28%19%12%5%
704
16th to endNight
420%27%32%12%3
632
March1st to 15thNight
7%27%33%23%7%
720
16th to endNight
6%23%26%28%11%2
768
April1st to 15thNight
7%23%23%29%14%1
671
16th to endNight
10%23%21%27%15%2
528
May1st to 15thNight
10%19%15%30%20%2
360
16th to endNight
17%19%14%17%24%6%
375
June1st to 15thNight
17%19%13%25%20%3
360
16th to endNight
13%18%17%27%20%2
360
July1st to 15thNight
9%13%15%35%25%1
340
16th to endNight
6%19%12%34%25%1
376
August1st to 15thNight
6%11%10%33%35%2
360
16th to endNight
10%13%20%32%19%2
559
September1st to 15thNight
12%13%20%27%18%7%
720
16th to endNight
14%16%22%25%17%3
656
October1st to 15thNight
16%15%25%28%11%2
660
16th to endNight
12%17%26%30%10%2
704
November1st to 15thNight
13%25%32%20%6%1
768
16th to endNight
9%26%34%22%5%2
900
December1st to 15thNight
7%23%31%24%9%2
900
16th to endNight
6%23%33%24%10%1
960
Page generated at 2017-09-16 15:07:01. Version ac04

Copyright 2017 A. Danko


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