Trois-Rivières
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Trois-Rivières clear sky chart from 2005-11-06 to 2024-03-28.

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%
22824
13%
81204
8%
22740
37%
22740
15%
58054

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
17%
755
9%
4388
3%
737
25%
737
5%
3181
January11th to 20thNight
19%
756
10%
4391
5%
740
26%
740
6%
3237
January21st to endNight
29%
829
8%
4859
9%
814
38%
814
8%
3577
February1st to 10thNight
21%
760
12%
2594
6%
760
31%
760
12%
1956
February11th to 20thNight
19%
743
12%
2271
4%
740
28%
740
12%
1741
February21st to endNight
25%
628
15%
1884
8%
628
34%
628
16%
1372
March1st to 10thNight
25%
760
15%
2280
9%
760
33%
760
16%
1695
March11th to 20thNight
24%
760
15%
2232
6%
760
33%
760
16%
1682
March21st to endNight
28%
821
20%
2051
7%
821
36%
821
21%
1510
April1st to 10thNight
26%
720
13%
1800
5%
720
30%
720
18%
1385
April11th to 20thNight
28%
681
17%
1745
5%
681
36%
681
22%
1255
April21st to endNight
25%
540
16%
1620
8%
540
34%
540
19%
1152
May1st to 10thNight
27%
450
15%
1530
9%
450
38%
450
16%
1080
May11th to 20thNight
31%
354
17%
1416
15%
354
43%
354
16%
934
May21st to endNight
29%
389
12%
1551
8%
388
44%
388
18%
988
June1st to 10thNight
34%
360
9%
1440
9%
360
42%
360
16%
943
June11th to 20thNight
42%
360
10%
1440
11%
360
47%
360
18%
912
June21st to endNight
41%
360
9%
1440
11%
360
46%
360
16%
952
July1st to 10thNight
44%
350
10%
1400
12%
350
52%
350
21%
869
July11th to 20thNight
51%
348
12%
1392
17%
348
55%
348
21%
853
July21st to endNight
46%
394
13%
1486
15%
372
51%
372
20%
918
August1st to 10thNight
58%
358
14%
1422
16%
356
63%
356
22%
862
August11th to 20thNight
49%
481
15%
1545
11%
481
52%
481
23%
1021
August21st to endNight
46%
782
18%
1970
9%
782
50%
782
30%
1324
September1st to 10thNight
46%
720
15%
1800
6%
720
50%
720
32%
1202
September11th to 20thNight
47%
720
19%
1916
11%
720
51%
720
33%
1210
September21st to endNight
41%
720
21%
1980
14%
720
46%
720
27%
1337
October1st to 10thNight
34%
720
21%
2042
12%
720
44%
720
23%
1408
October11th to 20thNight
31%
720
14%
2258
9%
720
39%
720
17%
1632
October21st to endNight
23%
792
11%
2574
5%
792
31%
792
14%
1915
November1st to 10thNight
27%
740
15%
2407
9%
740
35%
740
15%
1727
November11th to 20thNight
25%
760
17%
2512
11%
760
33%
760
14%
1847
November21st to endNight
23%
760
11%
2660
6%
760
30%
760
11%
2007
December1st to 10thNight
21%
807
9%
2759
3%
807
27%
807
10%
2183
December11th to 20thNight
19%
803
11%
3320
4%
802
27%
802
8%
2532
December21st to endNight
17%
823
8%
4829
4%
817
25%
817
5%
3655

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%47%6%35%5%5%7%32%
78361
Night
19%11%47%6%3445%6%31%
81605
TransparencyDay
52%5%12%21%10%1
78067
Night
55%5%11%19%10%1
81434
SeeingDay
22%11%29%24%11%3
13703
Night
24%9%29%29%9%1
22853

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
19%15%5%8%5%3435%6%26%
2517
11th to 20thDay
13%14%7%8%8%35%445%29%
2520
21st to endDay
12%14%7%9%7%35%5%5%7%26%
2772
February1st to 10thDay
15%16%5%8%7%5%5%435%26%
1582
11th to 20thDay
15%13%5%10%7%36%5%5%5%26%
1796
21st to endDay
16%13%5%9%6%45%35%5%29%
1570
March1st to 10thDay
16%11%47%6%445%47%32%
1897
11th to 20thDay
18%12%47%6%34446%33%
1943
21st to endDay
18%10%37%6%35%5%5%5%33%
2460
April1st to 10thDay
23%9%46%5%345%5%5%31%
2160
11th to 20thDay
22%6%25%4345%5%6%38%
2163
21st to endDay
23%10%36%6%3445%6%31%
2340
May1st to 10thDay
22%7%36%5%3445%6%35%
2446
11th to 20thDay
18%6%36%6%445%6%7%37%
2478
21st to endDay
19%6%37%6%35%5%5%6%33%
2725
June1st to 10thDay
21%7%35%6%45%5%6%7%31%
2520
11th to 20thDay
16%7%35%5%45%5%6%8%37%
2520
21st to endDay
20%8%37%5%45%5%5%6%30%
2520
July1st to 10thDay
14%5%35%6%35%6%7%9%37%
2520
11th to 20thDay
14%6%25%5%36%6%8%9%35%
2520
21st to endDay
14%6%36%6%36%7%7%9%34%
2744
August1st to 10thDay
16%6%25%6%36%6%7%11%30%
2506
11th to 20thDay
13%5%26%6%36%5%6%8%39%
2336
21st to endDay
14%5%25%5%45%5%6%8%41%
2384
September1st to 10thDay
16%5%35%5%35%5%6%8%40%
2160
11th to 20thDay
17%5%2442335%7%47%
2044
21st to endDay
20%6%2443445%6%41%
1980
October1st to 10thDay
21%7%36%5%3445%8%34%
1916
11th to 20thDay
22%7%38%7%45%46%7%27%
1702
21st to endDay
28%9%37%5%24346%27%
1782
November1st to 10thDay
20%9%36%6%35%445%34%
1671
11th to 20thDay
21%12%48%6%3445%5%28%
1665
21st to endDay
24%13%46%6%34446%26%
1520
December1st to 10thDay
28%14%5%7%6%3344324%
1409
11th to 20thDay
23%14%6%8%6%24335%26%
1801
21st to endDay
24%16%5%9%5%3344423%
2772
January1st to 10thNight
18%16%6%9%6%34445%24%
4429
11th to 20thNight
13%15%5%10%9%5%5%5%5%5%25%
4440
21st to endNight
15%14%5%11%8%35%5%5%5%24%
4884
February1st to 10thNight
14%14%6%10%8%45%5%5%5%26%
2594
11th to 20thNight
14%14%6%11%7%35%445%26%
2269
21st to endNight
16%13%47%6%35%44432%
1884
March1st to 10thNight
18%12%49%7%25%445%30%
2270
11th to 20thNight
19%13%48%6%44445%30%
2231
21st to endNight
18%11%46%425%445%36%
2051
April1st to 10thNight
25%10%47%5%2445%6%29%
1800
11th to 20thNight
21%8%25%5%24447%37%
1745
21st to endNight
23%10%45%424346%34%
1620
May1st to 10thNight
24%9%37%5%35%435%33%
1530
11th to 20thNight
20%8%36%6%3445%7%35%
1415
21st to endNight
20%6%35%434448%38%
1550
June1st to 10thNight
21%7%345%35%5%6%9%32%
1440
11th to 20thNight
20%6%25%426%5%5%8%37%
1440
21st to endNight
19%8%35%5%36%6%7%8%32%
1440
July1st to 10thNight
13%5%36%6%45%6%8%10%35%
1440
11th to 20thNight
14%5%26%5%36%5%6%9%38%
1440
21st to endNight
13%6%26%6%45%47%8%39%
1574
August1st to 10thNight
14%5%25%5%45%6%6%10%39%
1432
11th to 20thNight
15%6%36%6%35%5%6%7%38%
1545
21st to endNight
15%5%246%34448%43%
1970
September1st to 10thNight
16%5%25%5%245%6%7%44%
1800
11th to 20thNight
18%424423347%48%
1916
21st to endNight
19%6%25%5%34446%42%
1980
October1st to 10thNight
20%6%25%6%35%45%5%39%
2042
11th to 20thNight
23%8%36%5%35%35%5%33%
2258
21st to endNight
28%7%36%6%3445%6%28%
2574
November1st to 10thNight
21%9%37%6%35%45%5%32%
2407
11th to 20thNight
21%10%48%5%44445%30%
2512
21st to endNight
25%13%47%5%34345%27%
2660
December1st to 10thNight
24%13%5%9%6%3445%422%
2759
11th to 20thNight
23%14%5%9%6%34345%25%
3380
21st to endNight
27%19%5%8%42333423%
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
60%5%13%17%5%
2518
11th to 20thDay
57%6%10%20%7%
2520
21st to endDay
58%6%10%19%6%1
2772
February1st to 10thDay
61%39%18%8%2
1582
11th to 20thDay
59%5%12%14%9%1
1805
21st to endDay
58%310%18%9%2
1570
March1st to 10thDay
53%411%19%11%2
1900
11th to 20thDay
54%412%14%14%2
1943
21st to endDay
52%5%9%20%11%3
2460
April1st to 10thDay
55%410%17%11%2
2160
11th to 20thDay
48%49%23%13%2
2163
21st to endDay
56%49%16%13%3
2340
May1st to 10thDay
50%49%20%14%3
2446
11th to 20thDay
46%5%10%21%15%2
2482
21st to endDay
51%5%10%18%14%2
2725
June1st to 10thDay
51%6%11%21%9%2
2520
11th to 20thDay
46%5%12%24%12%2
2520
21st to endDay
54%6%11%18%10%1
2520
July1st to 10thDay
41%8%15%27%9%
2450
11th to 20thDay
42%6%17%26%9%
2445
21st to endDay
45%8%16%23%7%
2591
August1st to 10thDay
46%7%18%23%5%
2492
11th to 20thDay
42%7%17%25%9%
2336
21st to endDay
40%6%15%27%12%
2384
September1st to 10thDay
41%5%16%25%12%1
2160
11th to 20thDay
38%5%15%31%12%1
2044
21st to endDay
44%5%13%27%11%
1980
October1st to 10thDay
49%410%26%10%
1916
11th to 20thDay
57%5%13%21%4
1702
21st to endDay
58%5%11%18%7%1
1782
November1st to 10thDay
54%412%21%9%1
1671
11th to 20thDay
58%411%17%10%
1665
21st to endDay
60%6%13%17%41
1520
December1st to 10thDay
66%410%16%5%
1409
11th to 20thDay
64%37%19%6%
1802
21st to endDay
66%410%11%8%
2772
January1st to 10thNight
62%6%14%13%5%
4429
11th to 20thNight
61%7%10%17%41
4440
21st to endNight
62%5%12%14%7%
4884
February1st to 10thNight
61%48%17%9%1
2594
11th to 20thNight
61%5%8%15%10%1
2271
21st to endNight
56%39%17%13%2
1884
March1st to 10thNight
57%410%17%10%2
2280
11th to 20thNight
58%48%14%13%3
2232
21st to endNight
52%47%21%13%4
2051
April1st to 10thNight
57%48%16%13%2
1800
11th to 20thNight
49%5%8%22%15%2
1745
21st to endNight
52%48%18%15%3
1620
May1st to 10thNight
55%37%16%15%4
1530
11th to 20thNight
50%49%17%16%4
1416
21st to endNight
46%5%11%19%16%3
1551
June1st to 10thNight
49%5%12%21%12%1
1440
11th to 20thNight
45%6%9%22%14%4
1440
21st to endNight
49%6%12%20%12%1
1440
July1st to 10thNight
41%8%15%23%12%1
1400
11th to 20thNight
41%7%14%26%11%1
1392
21st to endNight
41%7%16%24%10%
1486
August1st to 10thNight
38%8%18%28%7%
1422
11th to 20thNight
44%6%17%24%9%
1545
21st to endNight
41%6%14%28%12%
1970
September1st to 10thNight
40%5%15%27%12%2
1800
11th to 20thNight
37%415%31%11%1
1916
21st to endNight
44%5%10%27%14%
1980
October1st to 10thNight
47%5%8%26%13%
2042
11th to 20thNight
53%6%12%22%7%
2258
21st to endNight
58%5%11%17%9%
2574
November1st to 10thNight
55%5%11%20%8%1
2407
11th to 20thNight
57%5%11%17%9%1
2512
21st to endNight
61%5%12%16%7%
2660
December1st to 10thNight
66%411%14%5%
2759
11th to 20thNight
63%48%18%7%
3380
21st to endNight
67%38%17%5%1
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
28%9%34%24%41
180
11th to 20thDay
26%15%32%19%7%1
180
21st to endDay
18%9%38%23%11%1
198
February1st to 10thDay
27%16%38%17%2
210
11th to 20thDay
23%12%38%24%3
404
21st to endDay
23%15%34%24%4
382
March1st to 10thDay
25%12%30%27%7%
460
11th to 20thDay
25%15%32%21%5%2
460
21st to endDay
24%12%33%20%9%2
490
April1st to 10thDay
29%10%28%25%8%
420
11th to 20thDay
25%16%29%20%8%3
412
21st to endDay
30%10%34%16%8%1
420
May1st to 10thDay
24%14%33%19%9%2
423
11th to 20thDay
19%9%36%23%11%3
447
21st to endDay
20%14%36%17%12%2
485
June1st to 10thDay
21%12%32%24%8%2
450
11th to 20thDay
19%11%28%25%14%3
450
21st to endDay
22%7%26%27%16%2
450
July1st to 10thDay
14%8%25%33%17%2
445
11th to 20thDay
16%7%28%32%14%3
444
21st to endDay
16%8%25%31%17%3
488
August1st to 10thDay
16%6%23%31%19%5%
446
11th to 20thDay
14%7%21%32%20%6%
439
21st to endDay
16%9%28%19%18%9%
495
September1st to 10thDay
17%7%29%27%14%7%
450
11th to 20thDay
16%9%24%28%16%8%
450
21st to endDay
20%8%26%23%16%6%
450
October1st to 10thDay
23%12%24%26%12%3
450
11th to 20thDay
25%10%29%23%11%2
401
21st to endDay
32%11%28%22%7%
396
November1st to 10thDay
27%14%27%25%6%1
365
11th to 20thDay
27%15%27%25%6%
325
21st to endDay
31%19%23%19%6%2
180
December1st to 10thDay
36%10%24%22%6%2
180
11th to 20thDay
26%19%33%15%6%1
180
21st to endDay
32%16%27%16%7%2
198
January1st to 10thNight
30%9%31%24%5%
760
11th to 20thNight
28%10%32%25%6%
760
21st to endNight
19%7%32%35%7%
836
February1st to 10thNight
19%9%38%27%6%1
760
11th to 20thNight
22%11%37%24%5%1
743
21st to endNight
25%10%31%28%5%
628
March1st to 10thNight
24%10%32%31%4
760
11th to 20thNight
24%13%32%26%6%
760
21st to endNight
23%12%31%27%8%
821
April1st to 10thNight
30%10%27%27%7%
720
11th to 20thNight
25%12%30%27%5%
681
21st to endNight
29%10%30%24%7%
540
May1st to 10thNight
28%9%28%28%7%
450
11th to 20thNight
25%6%32%30%6%1
354
21st to endNight
23%7%33%28%8%
389
June1st to 10thNight
24%6%27%35%8%1
360
11th to 20thNight
22%424%39%11%
360
21st to endNight
19%427%36%14%
360
July1st to 10thNight
15%5%27%37%14%1
350
11th to 20thNight
15%422%42%16%1
348
21st to endNight
15%425%40%15%1
394
August1st to 10thNight
15%315%46%21%1
358
11th to 20thNight
15%323%40%19%1
481
21st to endNight
17%5%24%35%18%2
782
September1st to 10thNight
17%5%26%38%13%2
720
11th to 20thNight
19%6%24%31%19%1
720
21st to endNight
21%7%26%29%15%2
720
October1st to 10thNight
21%7%30%30%11%
720
11th to 20thNight
25%10%26%29%9%1
720
21st to endNight
30%9%32%24%5%
792
November1st to 10thNight
26%11%27%28%7%1
740
11th to 20thNight
27%10%31%22%10%1
760
21st to endNight
32%12%25%24%7%
760
December1st to 10thNight
31%10%28%24%7%
807
11th to 20thNight
29%10%30%24%7%
803
21st to endNight
34%11%25%23%6%1
836
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