Sainte-Julie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sainte-Julie clear sky chart from 2005-11-06 to 2024-01-22.

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
30%
22573
14%
74832
9%
22533
37%
22533
16%
53649

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
18%
760
9%
2649
4%
757
24%
757
8%
2106
January11th to 20thNight
20%
760
10%
2660
5%
760
26%
760
9%
2091
January21st to endNight
25%
800
12%
2798
8%
800
33%
800
13%
2042
February1st to 10thNight
18%
720
9%
2398
4%
720
25%
720
10%
1887
February11th to 20thNight
20%
703
12%
2166
5%
700
30%
700
14%
1623
February21st to endNight
25%
592
16%
1776
7%
592
36%
592
15%
1308
March1st to 10thNight
26%
720
15%
2160
10%
720
34%
720
15%
1611
March11th to 20thNight
25%
720
15%
2102
7%
720
33%
720
16%
1556
March21st to endNight
30%
792
21%
1980
9%
792
37%
792
22%
1458
April1st to 10thNight
26%
720
15%
1800
4%
720
31%
720
18%
1370
April11th to 20thNight
28%
711
16%
1775
4%
711
35%
711
22%
1293
April21st to endNight
27%
557
17%
1637
8%
557
34%
557
18%
1170
May1st to 10thNight
28%
432
16%
1512
11%
432
37%
432
17%
1033
May11th to 20thNight
32%
354
18%
1416
17%
354
42%
354
16%
921
May21st to endNight
33%
389
13%
1551
10%
388
46%
388
19%
982
June1st to 10thNight
34%
360
10%
1440
10%
360
43%
360
15%
974
June11th to 20thNight
40%
360
11%
1440
13%
360
47%
360
18%
907
June21st to endNight
43%
360
10%
1440
14%
360
49%
360
16%
969
July1st to 10thNight
47%
350
13%
1400
17%
350
54%
350
22%
842
July11th to 20thNight
52%
348
13%
1392
19%
348
56%
348
22%
835
July21st to endNight
50%
394
13%
1486
15%
372
55%
372
21%
910
August1st to 10thNight
55%
358
16%
1422
18%
356
59%
356
21%
869
August11th to 20thNight
53%
524
17%
1588
12%
524
56%
524
26%
1031
August21st to endNight
50%
792
18%
1980
10%
792
52%
792
30%
1352
September1st to 10thNight
47%
720
15%
1800
7%
720
50%
720
30%
1226
September11th to 20thNight
50%
720
20%
1890
11%
720
54%
720
33%
1204
September21st to endNight
43%
720
21%
1980
15%
720
48%
720
27%
1329
October1st to 10thNight
37%
720
20%
2078
13%
720
46%
720
23%
1416
October11th to 20thNight
31%
720
15%
2215
10%
720
40%
720
17%
1613
October21st to endNight
24%
792
11%
2574
7%
792
32%
792
14%
1915
November1st to 10thNight
24%
740
16%
2407
9%
740
34%
740
16%
1683
November11th to 20thNight
24%
760
18%
2524
11%
760
33%
760
15%
1804
November21st to endNight
20%
760
12%
2660
6%
760
28%
760
11%
2002
December1st to 10thNight
18%
760
8%
2660
4%
760
23%
760
8%
2143
December11th to 20thNight
16%
760
11%
3238
4%
759
25%
759
8%
2448
December21st to endNight
14%
825
7%
4838
2%
817
22%
817
5%
3726

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%9%37%6%35%5%5%7%33%
74836
Night
19%10%47%6%3445%6%32%
75100
TransparencyDay
51%6%12%20%10%1
74541
Night
54%5%10%19%10%1
74929
SeeingDay
22%11%28%24%12%3
13496
Night
24%9%29%28%10%1
22584

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 10thDay
21%17%6%10%7%4433321%
1517
11th to 20thDay
20%14%5%10%6%445%35%24%
1520
21st to endDay
13%13%48%7%46%5%6%6%28%
1592
February1st to 10thDay
17%16%5%9%6%44446%24%
1561
11th to 20thDay
15%12%6%10%7%45%5%5%5%27%
1681
21st to endDay
19%13%6%7%7%4444428%
1480
March1st to 10thDay
16%12%5%9%8%45%445%28%
1797
11th to 20thDay
17%12%47%6%4445%6%32%
1854
21st to endDay
19%11%47%6%34445%33%
2376
April1st to 10thDay
23%10%47%5%43445%30%
2160
11th to 20thDay
21%8%36%5%34346%37%
2134
21st to endDay
22%9%36%6%35%446%32%
2322
May1st to 10thDay
20%8%37%5%35%5%46%35%
2463
11th to 20thDay
17%7%37%5%445%5%7%37%
2478
21st to endDay
18%6%26%5%35%6%6%8%35%
2725
June1st to 10thDay
21%7%36%5%45%5%6%7%31%
2520
11th to 20thDay
16%6%25%4445%5%8%40%
2520
21st to endDay
20%8%36%6%36%46%8%31%
2520
July1st to 10thDay
11%6%36%6%35%6%6%8%40%
2520
11th to 20thDay
13%5%35%6%36%6%8%10%36%
2520
21st to endDay
12%6%35%6%45%6%7%10%37%
2744
August1st to 10thDay
12%7%36%6%45%6%6%10%36%
2506
11th to 20thDay
10%5%36%6%45%5%7%9%41%
2292
21st to endDay
13%5%25%6%35%5%6%8%42%
2376
September1st to 10thDay
11%6%25%6%36%6%6%8%41%
2160
11th to 20thDay
16%6%2443345%8%48%
2070
21st to endDay
16%6%25%4445%6%7%40%
1980
October1st to 10thDay
20%6%36%6%35%5%5%7%33%
1880
11th to 20thDay
19%8%37%7%46%6%6%6%28%
1744
21st to endDay
27%9%46%434445%29%
1782
November1st to 10thDay
18%10%5%6%6%345%5%6%32%
1671
11th to 20thDay
18%11%47%6%45%6%47%29%
1653
21st to endDay
23%10%5%7%6%35%5%5%6%25%
1520
December1st to 10thDay
25%13%6%10%6%35%35%5%19%
1520
11th to 20thDay
23%13%5%7%6%3445%5%26%
1906
21st to endDay
27%15%5%9%6%4433319%
2772
January1st to 10thNight
19%17%7%9%7%3444421%
2649
11th to 20thNight
17%15%7%10%6%45%445%23%
2660
21st to endNight
14%13%6%9%7%45%446%29%
2798
February1st to 10thNight
16%15%7%11%8%45%446%21%
2398
11th to 20thNight
15%11%6%9%7%36%44429%
2164
21st to endNight
16%14%5%8%6%4444431%
1776
March1st to 10thNight
18%13%5%8%7%35%445%29%
2150
11th to 20thNight
19%13%5%6%6%34445%31%
2102
21st to endNight
19%11%37%5%3443438%
1980
April1st to 10thNight
25%9%37%5%35%446%30%
1800
11th to 20thNight
22%7%46%5%3445%6%34%
1775
21st to endNight
22%10%35%5%35%446%33%
1637
May1st to 10thNight
20%8%46%6%34447%34%
1512
11th to 20thNight
19%8%36%5%345%5%6%37%
1415
21st to endNight
17%6%36%435%5%5%7%39%
1550
June1st to 10thNight
22%7%36%5%345%5%7%32%
1440
11th to 20thNight
17%6%36%5%35%5%6%8%37%
1440
21st to endNight
16%7%38%5%36%5%5%9%33%
1440
July1st to 10thNight
12%5%25%7%35%5%6%9%40%
1440
11th to 20thNight
10%6%35%5%45%6%8%9%39%
1440
21st to endNight
12%436%6%35%6%7%9%39%
1574
August1st to 10thNight
14%5%35%5%35%6%6%9%40%
1432
11th to 20thNight
13%5%26%6%35%5%6%8%41%
1588
21st to endNight
13%6%25%6%346%6%8%41%
1980
September1st to 10thNight
13%6%36%6%345%5%7%43%
1800
11th to 20thNight
16%6%25%422347%49%
1890
21st to endNight
17%6%35%5%3335%8%42%
1980
October1st to 10thNight
18%6%35%5%35%447%39%
2078
11th to 20thNight
21%8%47%6%35%5%5%5%32%
2215
21st to endNight
25%9%47%6%35%44430%
2574
November1st to 10thNight
20%9%46%6%345%5%6%32%
2407
11th to 20thNight
21%10%48%5%345%45%32%
2524
21st to endNight
24%12%5%7%6%3434427%
2660
December1st to 10thNight
23%15%6%9%6%35%445%20%
2660
11th to 20thNight
23%15%5%7%6%34435%25%
3288
21st to endNight
27%16%5%9%5%3434422%
4884

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%49%13%5%
1518
11th to 20thDay
64%410%12%9%
1520
21st to endDay
56%6%11%18%9%1
1592
February1st to 10thDay
63%48%17%6%2
1561
11th to 20thDay
60%5%11%15%9%1
1690
21st to endDay
61%39%16%10%2
1480
March1st to 10thDay
58%49%17%10%2
1800
11th to 20thDay
53%5%12%15%13%2
1854
21st to endDay
53%410%19%12%2
2376
April1st to 10thDay
57%48%18%11%2
2160
11th to 20thDay
48%5%8%23%14%2
2134
21st to endDay
54%5%9%17%12%3
2322
May1st to 10thDay
50%410%19%15%2
2463
11th to 20thDay
46%6%10%20%16%2
2482
21st to endDay
46%6%14%19%13%3
2725
June1st to 10thDay
51%7%10%19%11%2
2520
11th to 20thDay
42%6%11%25%14%3
2520
21st to endDay
51%7%12%20%10%1
2520
July1st to 10thDay
40%8%12%28%12%1
2450
11th to 20thDay
41%8%15%28%9%
2445
21st to endDay
41%9%16%25%9%
2591
August1st to 10thDay
43%8%16%26%8%
2492
11th to 20thDay
38%7%18%26%11%
2292
21st to endDay
38%7%15%26%13%
2376
September1st to 10thDay
38%7%14%27%13%
2160
11th to 20thDay
36%5%12%33%14%1
2070
21st to endDay
42%7%14%26%11%1
1980
October1st to 10thDay
50%6%13%22%10%
1880
11th to 20thDay
54%7%13%19%7%
1744
21st to endDay
58%412%18%8%1
1782
November1st to 10thDay
50%7%13%20%9%1
1671
11th to 20thDay
55%6%12%15%11%
1653
21st to endDay
60%7%13%14%6%
1520
December1st to 10thDay
69%5%10%12%4
1520
11th to 20thDay
61%5%10%18%6%
1906
21st to endDay
69%6%12%8%5%
2772
January1st to 10thNight
67%5%9%14%5%
2649
11th to 20thNight
65%5%9%13%7%1
2660
21st to endNight
57%5%9%17%11%1
2798
February1st to 10thNight
66%49%15%6%1
2398
11th to 20thNight
58%410%19%9%1
2166
21st to endNight
56%49%16%13%1
1776
March1st to 10thNight
58%49%17%10%2
2160
11th to 20thNight
57%49%15%13%3
2103
21st to endNight
52%37%19%14%4
1980
April1st to 10thNight
56%48%17%13%2
1800
11th to 20thNight
51%48%21%15%2
1775
21st to endNight
53%47%19%13%3
1637
May1st to 10thNight
51%47%18%14%5%
1512
11th to 20thNight
48%6%8%17%17%4
1416
21st to endNight
44%6%11%20%15%3
1551
June1st to 10thNight
51%6%9%22%11%1
1440
11th to 20thNight
44%7%10%21%14%3
1440
21st to endNight
48%8%10%20%14%
1440
July1st to 10thNight
39%8%12%25%16%1
1400
11th to 20thNight
38%8%13%28%13%
1392
21st to endNight
40%8%17%25%10%
1486
August1st to 10thNight
40%8%16%25%11%
1422
11th to 20thNight
40%7%16%24%12%
1588
21st to endNight
40%7%13%27%12%1
1980
September1st to 10thNight
40%7%12%25%15%1
1800
11th to 20thNight
37%5%14%31%13%1
1890
21st to endNight
41%7%10%26%15%1
1980
October1st to 10thNight
46%5%10%25%13%1
2078
11th to 20thNight
54%5%10%23%7%
2215
21st to endNight
59%5%11%16%9%1
2574
November1st to 10thNight
53%412%21%8%1
2407
11th to 20thNight
54%5%12%18%10%2
2524
21st to endNight
60%5%11%17%6%
2660
December1st to 10thNight
67%6%11%13%4
2660
11th to 20thNight
63%49%17%7%
3288
21st to endNight
67%410%15%4
4884

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
29%13%30%18%10%
180
11th to 20thDay
28%14%33%19%6%
180
21st to endDay
21%12%34%21%11%1
178
February1st to 10thDay
35%18%33%14%1
214
11th to 20thDay
25%12%36%24%31
349
21st to endDay
29%12%29%26%4
346
March1st to 10thDay
23%12%32%25%8%
420
11th to 20thDay
22%15%33%21%8%1
420
21st to endDay
27%10%31%21%10%1
462
April1st to 10thDay
30%12%29%20%7%2
420
11th to 20thDay
28%18%22%19%9%3
412
21st to endDay
29%12%30%18%10%2
420
May1st to 10thDay
24%11%32%20%10%3
423
11th to 20thDay
17%10%31%26%12%3
447
21st to endDay
19%13%32%22%11%3
485
June1st to 10thDay
24%10%27%27%9%2
450
11th to 20thDay
17%9%25%30%16%2
450
21st to endDay
22%8%27%26%14%4
450
July1st to 10thDay
13%8%23%32%18%6%
445
11th to 20thDay
14%5%29%33%15%4
444
21st to endDay
15%6%27%32%18%3
488
August1st to 10thDay
14%5%23%30%21%6%
446
11th to 20thDay
11%5%22%34%20%9%
439
21st to endDay
15%8%25%24%18%11%
495
September1st to 10thDay
12%6%29%29%15%8%
450
11th to 20thDay
17%7%21%27%16%11%
450
21st to endDay
17%8%28%21%19%7%
450
October1st to 10thDay
23%12%26%22%14%3
450
11th to 20thDay
23%12%30%21%12%1
421
21st to endDay
32%12%26%23%6%
396
November1st to 10thDay
27%13%28%22%9%
365
11th to 20thDay
26%14%31%20%7%2
313
21st to endDay
32%10%31%20%6%1
180
December1st to 10thDay
36%8%22%23%8%3
180
11th to 20thDay
26%21%36%14%4
180
21st to endDay
30%21%26%18%41
198
January1st to 10thNight
28%11%31%25%5%
760
11th to 20thNight
26%11%33%23%7%
760
21st to endNight
21%10%33%28%7%1
800
February1st to 10thNight
23%10%36%25%5%1
720
11th to 20thNight
21%11%37%25%5%1
703
21st to endNight
24%10%31%30%5%
592
March1st to 10thNight
25%9%31%28%6%
720
11th to 20thNight
28%10%31%24%7%
720
21st to endNight
24%7%31%29%7%1
792
April1st to 10thNight
30%11%26%27%6%
720
11th to 20thNight
26%13%28%25%7%1
711
21st to endNight
27%11%29%25%7%1
557
May1st to 10thNight
26%8%31%26%7%2
432
11th to 20thNight
23%9%30%29%9%1
354
21st to endNight
19%7%35%31%9%
389
June1st to 10thNight
24%429%31%10%1
360
11th to 20thNight
20%430%34%13%
360
21st to endNight
18%5%27%36%14%1
360
July1st to 10thNight
13%5%28%39%15%1
350
11th to 20thNight
12%125%46%14%2
348
21st to endNight
13%324%43%16%1
394
August1st to 10thNight
14%5%17%43%20%2
358
11th to 20thNight
13%320%39%23%2
524
21st to endNight
16%5%20%37%20%2
792
September1st to 10thNight
16%423%40%16%1
720
11th to 20thNight
18%5%21%35%19%3
720
21st to endNight
20%5%26%31%15%3
720
October1st to 10thNight
22%8%28%30%12%1
720
11th to 20thNight
27%9%26%28%9%
720
21st to endNight
29%9%31%25%6%
792
November1st to 10thNight
25%11%32%23%8%1
740
11th to 20thNight
27%11%31%21%9%1
760
21st to endNight
29%12%30%20%8%
760
December1st to 10thNight
31%11%29%22%6%
760
11th to 20thNight
29%12%33%20%6%1
760
21st to endNight
34%12%30%18%6%
836
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