Lac Echo
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac Echo clear sky chart from 2005-11-05 to 2017-12-20.

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
28%
14984
13%
48060
8%
14953
35%
14953
15%
34539

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
15%
720
7%
2506
2%
716
21%
716
7%
2043
January16th to endNight
20%
768
11%
2665
5%
768
27%
768
11%
2005
February1st to 15thNight
17%
703
11%
2287
4%
701
25%
701
10%
1768
February16th to endNight
21%
631
14%
1946
6%
631
32%
631
12%
1471
March1st to 15thNight
20%
720
13%
2115
6%
720
28%
720
13%
1616
March16th to endNight
28%
768
20%
2024
9%
768
37%
768
20%
1406
April1st to 15thNight
24%
718
16%
1796
6%
718
29%
718
19%
1315
April16th to endNight
26%
628
16%
1708
7%
628
33%
628
20%
1197
May1st to 15thNight
30%
360
16%
1440
14%
360
41%
360
15%
953
May16th to endNight
32%
375
13%
1497
10%
374
46%
374
17%
978
June1st to 15thNight
33%
360
8%
1440
7%
360
40%
360
14%
975
June16th to endNight
42%
360
8%
1440
12%
360
46%
360
19%
920
July1st to 15thNight
50%
340
13%
1360
16%
340
57%
340
26%
764
July16th to endNight
53%
376
13%
1418
16%
354
58%
354
27%
813
August1st to 15thNight
52%
413
13%
1484
12%
411
57%
411
24%
923
August16th to endNight
49%
711
20%
1857
10%
711
55%
711
36%
1161
September1st to 15thNight
42%
720
14%
1800
6%
720
45%
720
28%
1249
September16th to endNight
45%
717
22%
1953
14%
717
49%
717
32%
1240
October1st to 15thNight
30%
720
16%
2160
10%
720
38%
720
18%
1506
October16th to endNight
22%
768
11%
2418
6%
768
30%
768
13%
1843
November1st to 15thNight
26%
760
16%
2531
10%
760
35%
760
14%
1827
November16th to endNight
18%
780
9%
2730
6%
780
23%
780
8%
2155
December1st to 15thNight
16%
780
8%
2730
2%
780
22%
780
7%
2193
December16th to endNight
11%
788
10%
2755
4%
788
19%
788
7%
2218

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
19%10%46%5%34446%29%
48788
Night
17%11%46%5%34445%30%
48229
Cloud CoverDay
22%9%36%5%34445%29%
48797
Night
20%10%46%5%34345%31%
48235
TransparencyDay
54%411%19%9%1
48475
Night
54%411%19%9%
48060
SeeingDay
25%13%28%19%9%3
5747
Night
24%13%28%24%9%
14985

By Month

Percentage Cloud Cover NE (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
22%17%6%9%7%3432318%
1432
16th to endDay
14%17%5%8%6%45%45%422%
1557
February1st to 15thDay
12%16%6%12%8%44435%21%
1575
16th to endDay
16%15%7%7%7%3443425%
1527
March1st to 15thDay
17%14%5%8%6%34445%25%
1834
16th to endDay
15%9%46%5%3335%7%35%
2199
April1st to 15thDay
24%11%46%323335%31%
2152
16th to endDay
21%8%46%6%33435%34%
2263
May1st to 15thDay
22%9%36%5%24346%30%
2511
16th to endDay
20%7%46%5%3435%6%31%
2618
June1st to 15thDay
22%7%36%5%35%45%7%26%
2520
16th to endDay
21%5%25%5%25%5%6%8%29%
2520
July1st to 15thDay
15%6%35%5%35%5%6%8%33%
2520
16th to endDay
14%6%36%5%35%6%6%8%31%
2654
August1st to 15thDay
15%7%36%6%445%6%7%32%
2463
16th to endDay
13%6%25%5%3445%8%38%
2331
September1st to 15thDay
19%6%26%424347%38%
2160
16th to endDay
18%6%23323347%44%
2004
October1st to 15thDay
23%9%25%434446%31%
1800
16th to endDay
27%14%37%5%3443421%
1806
November1st to 15thDay
17%10%46%7%245%47%29%
1654
16th to endDay
24%14%6%8%6%2343321%
1560
December1st to 15thDay
21%18%7%10%5%35%435%13%
1560
16th to endDay
22%18%7%8%6%2333418%
1568
January1st to 15thNight
18%18%7%9%7%35%44416%
2506
16th to endNight
13%16%6%6%7%35%45%5%23%
2665
February1st to 15thNight
10%15%6%11%9%5%5%5%4423%
2285
16th to endNight
14%15%5%9%6%3445%5%25%
1946
March1st to 15thNight
20%11%5%9%5%34435%27%
2102
16th to endNight
14%9%45%5%3434440%
2024
April1st to 15thNight
25%9%34323336%33%
1796
16th to endNight
19%10%36%423445%36%
1708
May1st to 15thNight
21%10%45%433346%34%
1440
16th to endNight
17%7%26%5%25%45%6%35%
1495
June1st to 15thNight
20%8%25%6%3445%8%30%
1440
16th to endNight
17%5%245%26%5%5%7%36%
1440
July1st to 15thNight
12%5%243245%5%7%45%
1440
16th to endNight
9%5%245%245%5%9%44%
1514
August1st to 15thNight
12%5%25%436%6%6%8%39%
1494
16th to endNight
10%5%24324448%48%
1857
September1st to 15thNight
16%7%26%434445%40%
1800
16th to endNight
15%6%33423345%47%
1953
October1st to 15thNight
20%8%25%5%34436%35%
2160
16th to endNight
25%12%46%5%23345%25%
2418
November1st to 15thNight
20%10%46%5%35%446%29%
2531
16th to endNight
22%13%6%9%6%3433421%
2730
December1st to 15thNight
21%17%7%7%6%24435%18%
2730
16th to endNight
21%18%7%7%6%3444418%
2755

Percentage Cloud Cover SE (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
22%18%6%9%8%3432418%
1432
16th to endDay
14%17%5%8%6%45%45%422%
1557
February1st to 15thDay
13%15%6%12%8%44435%21%
1575
16th to endDay
17%15%7%7%6%3433325%
1527
March1st to 15thDay
25%11%46%5%2333329%
1844
16th to endDay
24%7%35%323245%35%
2198
April1st to 15thDay
27%10%45%41223430%
2152
16th to endDay
24%8%36%5%3333433%
2263
May1st to 15thDay
31%8%25%5%23335%28%
2511
16th to endDay
29%6%25%5%23345%30%
2618
June1st to 15thDay
26%7%35%5%3435%6%27%
2520
16th to endDay
24%5%25%5%25%46%7%30%
2520
July1st to 15thDay
15%6%35%5%35%5%5%8%34%
2520
16th to endDay
14%6%36%5%36%6%6%9%31%
2654
August1st to 15thDay
26%425%5%34445%32%
2463
16th to endDay
23%414423347%38%
2331
September1st to 15thDay
18%6%26%424446%38%
2160
16th to endDay
18%6%24322346%44%
2004
October1st to 15thDay
23%9%25%434446%32%
1800
16th to endDay
27%15%37%43443421%
1806
November1st to 15thDay
20%10%46%5%34445%30%
1654
16th to endDay
25%14%5%9%42433323%
1560
December1st to 15thDay
22%18%7%9%6%35%435%14%
1560
16th to endDay
22%19%7%9%6%2333418%
1568
January1st to 15thNight
18%18%6%9%7%45%44416%
2506
16th to endNight
12%16%6%7%8%35%5%45%23%
2665
February1st to 15thNight
12%14%6%11%8%4444424%
2278
16th to endNight
16%14%5%9%6%3435%426%
1946
March1st to 15thNight
29%8%36%42432429%
2115
16th to endNight
23%8%2442333341%
2024
April1st to 15thNight
26%9%34323336%33%
1796
16th to endNight
21%9%45%423435%36%
1708
May1st to 15thNight
26%8%45%42333433%
1440
16th to endNight
22%5%25%43445%6%34%
1495
June1st to 15thNight
21%8%35%6%2445%7%31%
1440
16th to endNight
19%5%235%25%5%47%37%
1440
July1st to 15thNight
12%5%2442446%7%45%
1440
16th to endNight
9%5%25%435%46%9%43%
1514
August1st to 15thNight
16%42442445%7%42%
1494
16th to endNight
17%324323446%48%
1857
September1st to 15thNight
16%7%25%5%33445%41%
1800
16th to endNight
15%6%24323245%48%
1953
October1st to 15thNight
20%8%35%5%24445%36%
2160
16th to endNight
24%12%36%5%33345%26%
2418
November1st to 15thNight
24%9%45%5%34335%31%
2531
16th to endNight
25%13%5%8%5%3432424%
2730
December1st to 15thNight
22%16%7%6%6%2433419%
2730
16th to endNight
21%18%6%7%6%2443420%
2755

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
71%36%11%4
1433
16th to endDay
62%410%14%8%
1557
February1st to 15thDay
64%39%16%5%
1577
16th to endDay
62%38%15%9%1
1527
March1st to 15thDay
60%310%16%7%1
1844
16th to endDay
47%39%19%15%4
2199
April1st to 15thDay
55%37%18%12%2
2152
16th to endDay
53%36%19%13%3
2263
May1st to 15thDay
55%36%18%13%1
2511
16th to endDay
52%5%11%17%11%1
2622
June1st to 15thDay
55%411%19%8%
2520
16th to endDay
49%5%14%20%9%
2520
July1st to 15thDay
43%5%14%25%10%
2371
16th to endDay
47%6%16%20%9%
2487
August1st to 15thDay
48%6%15%21%6%
2449
16th to endDay
42%5%15%26%8%
2331
September1st to 15thDay
45%412%25%11%
2160
16th to endDay
40%414%31%9%
2004
October1st to 15thDay
53%311%21%9%
1800
16th to endDay
66%411%13%3
1806
November1st to 15thDay
53%5%13%18%7%1
1654
16th to endDay
66%310%12%5%
1560
December1st to 15thDay
71%49%10%2
1560
16th to endDay
70%48%10%5%
1568
January1st to 15thNight
70%49%11%3
2506
16th to endNight
60%49%16%7%
2665
February1st to 15thNight
63%39%17%5%
2287
16th to endNight
59%39%17%9%
1946
March1st to 15thNight
60%38%18%7%1
2115
16th to endNight
47%39%20%16%3
2024
April1st to 15thNight
52%37%20%14%1
1796
16th to endNight
49%38%19%15%2
1708
May1st to 15thNight
52%27%19%14%3
1440
16th to endNight
47%5%11%21%12%1
1497
June1st to 15thNight
51%5%12%21%8%
1440
16th to endNight
44%6%13%22%12%
1440
July1st to 15thNight
34%5%15%27%15%
1360
16th to endNight
35%5%16%28%12%
1418
August1st to 15thNight
39%7%19%24%8%
1484
16th to endNight
33%418%32%10%
1857
September1st to 15thNight
44%412%25%12%
1800
16th to endNight
38%313%35%8%
1953
October1st to 15thNight
49%49%23%12%
2160
16th to endNight
59%412%17%5%
2418
November1st to 15thNight
54%5%12%17%9%
2531
16th to endNight
66%410%13%4
2730
December1st to 15thNight
68%311%11%4
2730
16th to endNight
68%38%12%5%
2755

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
33%20%25%16%5%
60
16th to endDay
35%10%35%13%21
67
February1st to 15thDay
35%21%35%5%2
90
16th to endDay
31%20%26%18%2
186
March1st to 15thDay
28%17%30%17%5%
270
16th to endDay
23%20%27%17%9%1
288
April1st to 15thDay
30%20%27%15%5%
270
16th to endDay
27%19%27%14%8%2
270
May1st to 15thDay
35%10%26%17%6%2
288
16th to endDay
25%15%32%16%9%1
331
June1st to 15thDay
28%13%31%20%5%
315
16th to endDay
20%11%34%22%8%2
315
July1st to 15thDay
17%10%34%25%8%3
305
16th to endDay
15%6%34%28%12%3
326
August1st to 15thDay
18%5%22%36%13%4
313
16th to endDay
16%7%29%23%14%8%
332
September1st to 15thDay
19%9%26%20%15%9%
315
16th to endDay
20%10%21%21%16%9%
314
October1st to 15thDay
28%15%23%19%11%2
315
16th to endDay
36%15%26%13%7%
307
November1st to 15thDay
24%12%32%22%7%
218
16th to endDay
36%25%27%10%
90
December1st to 15thDay
30%17%40%11%1
90
16th to endDay
45%22%29%2
72
January1st to 15thNight
30%14%31%18%4
720
16th to endNight
23%14%31%22%7%
768
February1st to 15thNight
19%17%35%21%5%
704
16th to endNight
22%19%29%22%4
631
March1st to 15thNight
27%17%29%21%4
720
16th to endNight
20%18%27%24%8%
768
April1st to 15thNight
29%15%27%22%3
718
16th to endNight
25%16%27%22%7%
628
May1st to 15thNight
27%9%26%26%8%1
360
16th to endNight
18%11%33%24%10%
375
June1st to 15thNight
22%9%28%30%8%
360
16th to endNight
18%5%28%34%12%1
360
July1st to 15thNight
12%5%26%37%17%
340
16th to endNight
12%325%39%16%1
376
August1st to 15thNight
15%222%36%20%2
413
16th to endNight
13%5%24%33%20%2
711
September1st to 15thNight
21%6%25%27%16%2
720
16th to endNight
19%7%25%26%18%2
717
October1st to 15thNight
25%12%26%23%10%1
720
16th to endNight
33%12%26%19%7%
768
November1st to 15thNight
27%14%27%18%10%
760
16th to endNight
30%18%25%16%7%
780
December1st to 15thNight
30%19%26%19%3
780
16th to endNight
32%14%31%14%5%1
788
Page generated at 2017-12-21 07:04:50. Version ac04

Copyright 2017 A. Danko


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