Lac Lasalle
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac Lasalle clear sky chart from 2005-11-05 to 2017-04-26.

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
25%
14246
13%
45633
6%
14214
33%
14214
15%
32791

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
14%
720
8%
2506
2%
716
22%
716
8%
1979
January16th to endNight
18%
768
11%
2688
4%
768
26%
768
11%
1994
February1st to 15thNight
16%
704
10%
2308
3%
701
25%
701
11%
1759
February16th to endNight
18%
631
13%
1909
5%
631
28%
631
12%
1424
March1st to 15thNight
16%
720
13%
2160
6%
720
25%
720
12%
1640
March16th to endNight
26%
768
20%
1992
7%
768
35%
768
21%
1383
April1st to 15thNight
22%
718
16%
1796
4%
718
28%
718
19%
1325
April16th to endNight
25%
616
16%
1672
6%
616
32%
616
20%
1174
May1st to 15thNight
25%
336
15%
1326
11%
336
37%
336
15%
899
May16th to endNight
26%
343
13%
1369
10%
342
40%
342
17%
896
June1st to 15thNight
27%
330
7%
1320
5%
330
36%
330
12%
942
June16th to endNight
40%
330
7%
1320
9%
330
44%
330
17%
872
July1st to 15thNight
46%
310
12%
1240
16%
310
53%
310
25%
711
July16th to endNight
46%
348
10%
1306
10%
326
52%
326
21%
807
August1st to 15thNight
53%
331
13%
1312
12%
329
60%
329
20%
819
August16th to endNight
47%
684
17%
1734
9%
684
51%
684
33%
1116
September1st to 15thNight
40%
660
13%
1650
5%
660
43%
660
28%
1149
September16th to endNight
40%
657
19%
1796
11%
657
45%
657
30%
1166
October1st to 15thNight
27%
660
18%
1961
9%
660
38%
660
18%
1370
October16th to endNight
22%
704
11%
2249
5%
704
30%
704
13%
1698
November1st to 15thNight
24%
700
17%
2291
9%
700
34%
700
14%
1654
November16th to endNight
20%
720
12%
2520
7%
720
26%
720
10%
1888
December1st to 15thNight
15%
720
8%
2520
2%
720
21%
720
8%
1990
December16th to endNight
10%
768
10%
2688
2%
768
19%
768
7%
2136

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
18%10%47%6%3445%6%29%
46035
Night
16%9%46%5%3445%6%32%
45802
Cloud CoverDay
18%9%46%6%34446%30%
46044
Night
16%9%46%5%3445%6%33%
45808
TransparencyDay
54%6%11%17%9%1
45722
Night
51%7%11%18%9%1
45633
SeeingDay
23%15%30%20%7%2
4970
Night
22%15%31%22%7%
14246

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
19%15%6%9%8%3435%420%
1432
16th to endDay
11%14%7%10%6%35%445%26%
1536
February1st to 15thDay
10%16%6%9%8%35%5%45%23%
1551
16th to endDay
14%18%6%8%6%3443425%
1563
March1st to 15thDay
15%12%5%9%8%44325%26%
1790
16th to endDay
16%9%36%5%24346%36%
2229
April1st to 15thDay
21%11%35%5%23345%31%
2152
16th to endDay
20%10%35%5%23445%34%
2202
May1st to 15thDay
21%8%36%5%3345%6%30%
2301
16th to endDay
23%7%36%5%34446%30%
2394
June1st to 15thDay
23%7%36%6%35%5%5%7%25%
2310
16th to endDay
20%7%36%6%35%6%6%6%27%
2310
July1st to 15thDay
15%6%36%6%35%45%8%33%
2310
16th to endDay
14%6%37%6%36%5%6%9%29%
2458
August1st to 15thDay
17%7%37%6%46%6%6%6%27%
2307
16th to endDay
12%5%26%5%35%5%5%8%39%
2104
September1st to 15thDay
18%6%26%5%34447%35%
1980
16th to endDay
18%6%24423236%43%
1834
October1st to 15thDay
23%9%25%5%23446%31%
1669
16th to endDay
26%11%38%6%3444422%
1621
November1st to 15thDay
16%9%36%5%4445%7%29%
1566
16th to endDay
22%13%46%42335%5%26%
1440
December1st to 15thDay
22%16%7%8%5%235%4420%
1440
16th to endDay
20%17%6%9%5%2444419%
1536
January1st to 15thNight
15%15%6%9%8%35%5%5%6%19%
2506
16th to endNight
9%14%6%9%7%45%447%26%
2688
February1st to 15thNight
9%13%6%10%9%45%45%426%
2306
16th to endNight
13%13%5%8%6%35%45%6%27%
1909
March1st to 15thNight
17%11%48%5%36%45%5%27%
2147
16th to endNight
12%8%46%5%24345%40%
1992
April1st to 15thNight
22%8%35%5%33336%33%
1796
16th to endNight
19%7%25%4235%46%36%
1672
May1st to 15thNight
18%7%45%6%235%46%35%
1326
16th to endNight
21%5%35%42335%8%36%
1367
June1st to 15thNight
23%7%45%5%345%5%6%29%
1320
16th to endNight
18%5%25%425%5%47%37%
1320
July1st to 15thNight
11%415%43445%8%45%
1320
16th to endNight
9%5%24425%5%6%8%42%
1402
August1st to 15thNight
11%4245%35%5%6%9%40%
1322
16th to endNight
11%414433447%48%
1734
September1st to 15thNight
14%6%2443446%7%41%
1650
16th to endNight
17%413413346%47%
1796
October1st to 15thNight
18%6%26%6%24336%37%
1961
16th to endNight
24%9%26%5%24446%28%
2249
November1st to 15thNight
17%8%36%6%3446%7%30%
2291
16th to endNight
19%13%5%7%424345%27%
2520
December1st to 15thNight
19%14%5%9%5%25%446%21%
2520
16th to endNight
19%16%6%8%6%33445%21%
2688

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
20%13%6%8%7%4434421%
1432
16th to endDay
11%16%6%9%6%35%44427%
1536
February1st to 15thDay
10%15%6%9%8%45%5%45%24%
1551
16th to endDay
14%17%6%9%6%34435%25%
1563
March1st to 15thDay
15%12%5%10%7%35%335%26%
1800
16th to endDay
15%9%36%5%24446%36%
2228
April1st to 15thDay
22%10%35%6%23345%32%
2152
16th to endDay
19%10%35%5%24435%34%
2202
May1st to 15thDay
21%8%36%5%34446%30%
2301
16th to endDay
22%7%35%5%35%436%30%
2394
June1st to 15thDay
23%7%35%6%36%5%5%7%25%
2310
16th to endDay
20%6%36%5%35%6%7%6%27%
2310
July1st to 15thDay
15%6%35%6%45%5%6%7%33%
2310
16th to endDay
14%6%26%7%46%6%6%7%29%
2458
August1st to 15thDay
15%6%37%6%46%7%5%6%28%
2307
16th to endDay
11%5%25%6%35%5%5%8%40%
2104
September1st to 15thDay
18%6%35%5%345%47%36%
1980
16th to endDay
17%6%24423236%44%
1834
October1st to 15thDay
23%7%36%423446%31%
1669
16th to endDay
25%11%47%6%33445%23%
1621
November1st to 15thDay
16%8%46%5%445%5%8%30%
1566
16th to endDay
22%12%46%4335%45%27%
1440
December1st to 15thDay
22%15%5%7%6%24445%20%
1440
16th to endDay
20%16%6%9%6%24345%21%
1536
January1st to 15thNight
15%14%5%9%8%35%447%21%
2506
16th to endNight
10%13%6%9%6%45%5%46%27%
2688
February1st to 15thNight
9%13%5%10%8%45%45%5%25%
2299
16th to endNight
13%13%5%8%6%3445%6%28%
1909
March1st to 15thNight
17%11%48%445%45%5%27%
2160
16th to endNight
12%8%37%434435%41%
1992
April1st to 15thNight
23%8%345%3424434%
1796
16th to endNight
20%7%25%5%2445%6%36%
1672
May1st to 15thNight
17%8%36%6%33445%36%
1326
16th to endNight
21%5%345%24347%37%
1367
June1st to 15thNight
23%8%445%3345%7%29%
1320
16th to endNight
18%4244345%6%8%36%
1320
July1st to 15thNight
12%315%5%25%45%8%45%
1320
16th to endNight
9%5%25%5%245%6%6%43%
1402
August1st to 15thNight
11%5%25%336%5%7%8%40%
1322
16th to endNight
11%41442445%7%49%
1734
September1st to 15thNight
13%6%25%42445%7%41%
1650
16th to endNight
17%31431335%7%47%
1796
October1st to 15thNight
18%6%35%5%3435%5%38%
1961
16th to endNight
24%8%35%5%2445%7%29%
2249
November1st to 15thNight
17%9%36%5%345%5%6%32%
2291
16th to endNight
19%12%5%7%424445%28%
2520
December1st to 15thNight
19%13%5%7%6%25%45%6%22%
2520
16th to endNight
19%15%5%9%5%34335%22%
2688

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
66%6%7%14%5%
1433
16th to endDay
59%5%9%15%9%1
1536
February1st to 15thDay
61%410%16%6%
1553
16th to endDay
61%5%7%14%8%1
1563
March1st to 15thDay
61%48%14%9%1
1800
16th to endDay
47%5%9%17%14%4
2229
April1st to 15thDay
54%48%18%11%3
2152
16th to endDay
51%6%6%18%12%3
2202
May1st to 15thDay
53%5%8%17%12%1
2301
16th to endDay
53%7%9%17%10%1
2398
June1st to 15thDay
57%7%11%13%8%1
2310
16th to endDay
54%7%11%17%7%1
2310
July1st to 15thDay
45%8%15%21%8%
2161
16th to endDay
50%8%15%16%7%
2291
August1st to 15thDay
52%10%14%17%5%
2293
16th to endDay
40%8%18%21%9%
2104
September1st to 15thDay
47%7%13%21%10%
1980
16th to endDay
43%412%28%9%
1834
October1st to 15thDay
53%6%10%19%9%
1669
16th to endDay
63%6%11%12%5%
1621
November1st to 15thDay
51%8%15%14%9%
1566
16th to endDay
58%7%10%16%6%
1440
December1st to 15thDay
65%6%10%12%4
1440
16th to endDay
66%6%8%10%8%
1536
January1st to 15thNight
63%7%10%13%4
2506
16th to endNight
56%7%10%15%8%1
2688
February1st to 15thNight
59%6%10%16%6%
2308
16th to endNight
55%6%10%16%9%1
1909
March1st to 15thNight
56%7%8%16%9%1
2160
16th to endNight
45%5%10%18%17%2
1992
April1st to 15thNight
52%38%20%12%1
1796
16th to endNight
46%6%11%17%14%2
1672
May1st to 15thNight
49%6%10%16%13%4
1326
16th to endNight
46%6%10%21%12%1
1369
June1st to 15thNight
53%8%11%17%8%
1320
16th to endNight
45%8%11%20%12%
1320
July1st to 15thNight
34%7%18%26%11%
1240
16th to endNight
37%10%18%23%10%
1306
August1st to 15thNight
38%10%19%23%8%
1312
16th to endNight
34%7%17%29%10%
1734
September1st to 15thNight
40%9%15%25%10%
1650
16th to endNight
37%6%14%30%10%
1796
October1st to 15thNight
47%6%11%21%11%
1961
16th to endNight
55%8%11%17%7%
2249
November1st to 15thNight
51%7%12%18%7%2
2291
16th to endNight
57%7%10%16%6%
2520
December1st to 15thNight
62%8%11%14%3
2520
16th to endNight
64%7%9%11%6%1
2688

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
26%16%35%20%1
60
16th to endDay
25%20%35%12%33
64
February1st to 15thDay
32%27%31%5%2
86
16th to endDay
26%21%31%17%3
222
March1st to 15thDay
23%22%31%18%3
270
16th to endDay
22%19%29%18%7%2
288
April1st to 15thDay
30%19%27%14%6%1
270
16th to endDay
25%14%33%17%7%1
254
May1st to 15thDay
25%18%30%17%5%2
228
16th to endDay
27%15%31%17%7%
267
June1st to 15thDay
30%13%31%17%6%
255
16th to endDay
17%12%37%25%6%1
255
July1st to 15thDay
15%10%38%25%6%2
245
16th to endDay
17%6%31%31%10%2
270
August1st to 15thDay
20%7%27%29%11%4
253
16th to endDay
13%8%31%23%13%9%
268
September1st to 15thDay
18%10%27%24%11%7%
255
16th to endDay
19%13%25%20%13%7%
254
October1st to 15thDay
26%14%26%20%9%2
255
16th to endDay
32%15%27%16%7%
247
November1st to 15thDay
20%20%30%20%6%1
220
16th to endDay
35%23%25%15%1
60
December1st to 15thDay
28%26%28%13%3
60
16th to endDay
40%28%28%3
64
January1st to 15thNight
24%20%33%16%4
720
16th to endNight
16%18%36%22%41
768
February1st to 15thNight
17%20%37%18%5%
704
16th to endNight
21%16%37%19%3
631
March1st to 15thNight
24%18%36%18%2
720
16th to endNight
17%18%32%23%6%1
768
April1st to 15thNight
26%17%29%21%4
718
16th to endNight
25%17%29%20%6%
616
May1st to 15thNight
20%11%36%22%6%2
336
16th to endNight
22%9%38%21%7%
343
June1st to 15thNight
25%9%32%25%6%
330
16th to endNight
20%329%31%13%1
330
July1st to 15thNight
13%8%27%33%15%1
310
16th to endNight
12%429%39%12%1
348
August1st to 15thNight
14%423%38%18%
331
16th to endNight
14%7%27%30%19%1
684
September1st to 15thNight
17%7%30%30%11%1
660
16th to endNight
19%11%25%25%15%2
657
October1st to 15thNight
22%14%28%23%10%
660
16th to endNight
30%13%29%19%6%
704
November1st to 15thNight
22%17%29%21%8%1
700
16th to endNight
25%22%25%17%6%1
720
December1st to 15thNight
28%20%29%17%3
720
16th to endNight
29%19%32%14%31
768
Page generated at 2017-04-27 17:48:47. Version ac04

Copyright 2017 A. Danko


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