Saint-Jérôme
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saint-Jérôme clear sky chart from 2005-11-05 to 2017-09-17.

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
29%
14618
14%
46838
8%
14586
37%
14586
18%
32582

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
17%
720
9%
2506
4%
716
24%
716
10%
1906
January16th to endNight
20%
768
12%
2688
5%
768
29%
768
12%
1972
February1st to 15thNight
18%
704
10%
2308
4%
701
27%
701
13%
1733
February16th to endNight
21%
631
14%
1901
6%
631
31%
631
15%
1396
March1st to 15thNight
20%
720
14%
2160
8%
720
28%
720
15%
1603
March16th to endNight
30%
768
20%
1995
9%
768
38%
768
24%
1371
April1st to 15thNight
24%
718
17%
1796
5%
718
31%
718
21%
1326
April16th to endNight
25%
627
17%
1707
5%
627
35%
627
21%
1191
May1st to 15thNight
25%
378
15%
1458
9%
378
37%
378
15%
984
May16th to endNight
29%
375
13%
1497
11%
374
41%
374
18%
961
June1st to 15thNight
30%
360
8%
1440
5%
360
38%
360
15%
998
June16th to endNight
41%
360
8%
1440
11%
360
45%
360
18%
918
July1st to 15thNight
50%
340
13%
1360
17%
340
57%
340
26%
759
July16th to endNight
52%
376
12%
1418
14%
354
56%
354
25%
811
August1st to 15thNight
53%
361
14%
1432
15%
359
59%
359
21%
874
August16th to endNight
50%
755
20%
1901
10%
755
55%
755
37%
1184
September1st to 15thNight
47%
720
14%
1800
6%
720
50%
720
31%
1216
September16th to endNight
46%
665
21%
1818
13%
665
52%
665
33%
1130
October1st to 15thNight
31%
660
20%
1953
10%
660
42%
660
23%
1301
October16th to endNight
25%
704
12%
2252
6%
704
33%
704
16%
1618
November1st to 15thNight
26%
700
18%
2280
10%
700
37%
700
17%
1587
November16th to endNight
23%
720
14%
2520
8%
720
32%
720
13%
1794
December1st to 15thNight
19%
720
10%
2520
4%
720
27%
720
11%
1888
December16th to endNight
14%
768
12%
2688
4%
768
23%
768
9%
2061

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
17%8%36%6%35%45%6%32%
47954
Night
17%8%36%5%34446%34%
47007
Cloud CoverDay
17%8%36%5%35%5%5%6%33%
47963
Night
17%9%36%5%3445%6%33%
47013
TransparencyDay
50%5%11%20%10%1
47641
Night
50%411%20%10%1
46838
SeeingDay
21%11%29%24%11%2
5557
Night
22%9%31%26%9%
14618

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%13%48%6%34445%23%
1432
16th to endDay
11%15%48%7%35%445%29%
1536
February1st to 15thDay
14%12%49%7%5%6%445%24%
1554
16th to endDay
15%14%5%8%7%34345%27%
1572
March1st to 15thDay
16%10%48%8%45%44428%
1790
16th to endDay
16%8%35%5%34345%39%
2229
April1st to 15thDay
23%9%3442344433%
2152
16th to endDay
19%7%35%5%3344437%
2252
May1st to 15thDay
21%6%36%6%24446%30%
2503
16th to endDay
20%6%35%435%5%5%7%31%
2618
June1st to 15thDay
22%7%246%25%5%5%7%29%
2520
16th to endDay
18%6%26%6%37%6%6%7%28%
2520
July1st to 15thDay
12%5%25%5%46%6%6%8%36%
2520
16th to endDay
11%5%35%6%46%6%7%9%34%
2654
August1st to 15thDay
12%6%26%7%46%7%6%8%32%
2514
16th to endDay
9%4235%35%5%5%9%44%
2292
September1st to 15thDay
16%5%25%4345%48%39%
2160
16th to endDay
14%6%24323346%48%
1847
October1st to 15thDay
21%8%26%434446%34%
1675
16th to endDay
22%9%47%7%34346%26%
1620
November1st to 15thDay
14%8%446%35%5%6%7%32%
1578
16th to endDay
22%9%27%33445%6%30%
1440
December1st to 15thDay
22%13%5%7%6%35%345%23%
1440
16th to endDay
23%13%5%7%5%24345%23%
1536
January1st to 15thNight
16%14%6%8%6%35%45%5%23%
2506
16th to endNight
11%11%5%9%7%46%5%45%28%
2688
February1st to 15thNight
10%12%5%10%8%36%5%5%5%25%
2306
16th to endNight
15%11%47%6%35%445%29%
1901
March1st to 15thNight
18%9%48%5%345%45%29%
2147
16th to endNight
14%9%35%5%23435%41%
1995
April1st to 15thNight
24%6%46%423345%34%
1796
16th to endNight
20%6%25%5%2445%6%37%
1707
May1st to 15thNight
20%6%36%6%3444435%
1458
16th to endNight
21%5%24424346%37%
1495
June1st to 15thNight
23%7%36%3235%47%31%
1440
16th to endNight
17%5%25%6%245%5%8%37%
1440
July1st to 15thNight
9%5%145%245%6%9%44%
1440
16th to endNight
10%434435%47%8%42%
1514
August1st to 15thNight
10%5%36%5%35%45%8%40%
1442
16th to endNight
11%41342435%7%49%
1901
September1st to 15thNight
13%5%35%4345%5%7%42%
1800
16th to endNight
17%313323446%49%
1818
October1st to 15thNight
18%5%35%434446%39%
1953
16th to endNight
23%8%36%433445%32%
2252
November1st to 15thNight
18%8%26%5%3445%6%33%
2280
16th to endNight
20%11%46%5%23345%30%
2520
December1st to 15thNight
20%13%46%5%3435%6%25%
2520
16th to endNight
22%14%6%7%5%34335%23%
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%12%48%6%34345%24%
1432
16th to endDay
12%14%47%7%35%5%5%5%29%
1536
February1st to 15thDay
13%14%48%6%47%5%5%5%25%
1554
16th to endDay
16%13%5%8%6%25%44427%
1572
March1st to 15thDay
17%11%47%8%4435%427%
1800
16th to endDay
16%8%36%5%24345%39%
2228
April1st to 15thDay
22%9%35%43344433%
2152
16th to endDay
19%7%35%5%34445%37%
2252
May1st to 15thDay
21%6%45%6%34446%31%
2503
16th to endDay
20%5%25%5%35%5%5%7%32%
2618
June1st to 15thDay
21%7%35%5%35%5%48%30%
2520
16th to endDay
17%6%36%6%46%5%7%8%28%
2520
July1st to 15thDay
12%425%6%36%6%6%8%37%
2520
16th to endDay
11%5%25%5%46%6%8%9%35%
2654
August1st to 15thDay
11%6%37%6%46%6%6%8%33%
2514
16th to endDay
9%4146%35%5%5%9%45%
2292
September1st to 15thDay
15%5%244345%5%8%40%
2160
16th to endDay
13%425%324346%48%
1847
October1st to 15thDay
21%7%25%5%24445%35%
1675
16th to endDay
21%8%47%6%345%45%27%
1620
November1st to 15thDay
14%9%36%5%35%45%7%33%
1578
16th to endDay
21%9%36%434446%30%
1440
December1st to 15thDay
23%12%5%8%424445%22%
1440
16th to endDay
24%12%47%6%24345%23%
1536
January1st to 15thNight
16%14%6%8%7%2445%5%22%
2506
16th to endNight
11%12%5%9%7%45%446%27%
2688
February1st to 15thNight
11%12%411%7%46%5%5%5%24%
2299
16th to endNight
16%10%5%8%5%35%45%5%29%
1901
March1st to 15thNight
19%10%46%5%34445%29%
2160
16th to endNight
15%9%36%5%24335%41%
1995
April1st to 15thNight
24%7%45%423335%34%
1796
16th to endNight
20%7%25%433446%37%
1707
May1st to 15thNight
20%7%37%5%34345%34%
1458
16th to endNight
20%6%25%42445%7%36%
1495
June1st to 15thNight
23%7%36%43345%6%31%
1440
16th to endNight
17%5%16%435%46%7%36%
1440
July1st to 15thNight
9%424335%6%7%10%42%
1440
16th to endNight
10%434335%5%7%9%42%
1514
August1st to 15thNight
10%5%26%5%3446%9%39%
1442
16th to endNight
11%31441345%8%48%
1901
September1st to 15thNight
13%5%246%2436%8%42%
1800
16th to endNight
16%424323446%48%
1818
October1st to 15thNight
18%5%346%2435%6%39%
1953
16th to endNight
23%8%36%5%23335%32%
2252
November1st to 15thNight
19%8%25%5%35%446%33%
2280
16th to endNight
20%11%36%5%33445%30%
2520
December1st to 15thNight
22%13%46%5%24345%25%
2520
16th to endNight
22%15%5%8%5%2433424%
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
62%5%9%15%6%
1433
16th to endDay
55%6%10%18%8%1
1536
February1st to 15thDay
60%310%18%5%
1556
16th to endDay
59%39%16%9%1
1572
March1st to 15thDay
59%310%15%9%1
1800
16th to endDay
46%310%19%15%4
2229
April1st to 15thDay
52%47%19%12%3
2152
16th to endDay
49%47%20%13%4
2252
May1st to 15thDay
53%48%18%13%2
2503
16th to endDay
49%6%10%19%12%1
2622
June1st to 15thDay
52%5%11%18%10%1
2520
16th to endDay
51%8%10%20%8%1
2520
July1st to 15thDay
40%7%14%24%12%
2371
16th to endDay
42%8%16%22%8%
2487
August1st to 15thDay
46%8%15%20%8%
2500
16th to endDay
35%6%18%26%11%
2292
September1st to 15thDay
41%6%12%25%12%
2160
16th to endDay
37%313%32%11%
1847
October1st to 15thDay
50%5%10%22%11%
1675
16th to endDay
58%5%12%16%6%
1620
November1st to 15thDay
48%6%14%18%10%
1578
16th to endDay
54%5%12%18%7%
1440
December1st to 15thDay
63%5%11%14%4
1440
16th to endDay
63%5%10%12%8%
1536
January1st to 15thNight
61%5%10%16%5%
2506
16th to endNight
57%5%10%16%8%1
2688
February1st to 15thNight
59%411%17%6%
2308
16th to endNight
56%39%17%10%
1901
March1st to 15thNight
56%5%8%18%9%1
2160
16th to endNight
46%310%19%16%3
1995
April1st to 15thNight
52%36%21%15%1
1796
16th to endNight
47%48%19%15%3
1707
May1st to 15thNight
51%47%17%14%4
1458
16th to endNight
46%5%11%21%14%1
1497
June1st to 15thNight
52%5%10%19%10%
1440
16th to endNight
45%6%12%20%14%1
1440
July1st to 15thNight
32%8%15%27%15%
1360
16th to endNight
36%6%19%24%12%
1418
August1st to 15thNight
40%7%17%23%10%
1432
16th to endNight
32%5%17%31%12%
1901
September1st to 15thNight
40%5%14%25%13%
1800
16th to endNight
35%412%33%12%
1818
October1st to 15thNight
45%411%25%12%
1953
16th to endNight
53%5%13%19%7%
2252
November1st to 15thNight
51%413%19%8%2
2280
16th to endNight
55%411%20%7%
2520
December1st to 15thNight
60%413%17%3
2520
16th to endNight
64%310%14%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
15%30%23%26%5%
60
16th to endDay
25%17%35%15%41
64
February1st to 15thDay
31%24%33%10%1
87
16th to endDay
25%13%32%22%5%
231
March1st to 15thDay
24%18%30%22%4
270
16th to endDay
21%12%33%18%11%2
288
April1st to 15thDay
28%15%30%15%8%1
270
16th to endDay
18%18%28%21%11%1
270
May1st to 15thDay
28%12%28%20%7%2
288
16th to endDay
22%13%31%22%8%1
331
June1st to 15thDay
25%12%32%20%7%1
315
16th to endDay
22%8%26%32%8%1
315
July1st to 15thDay
15%6%34%25%14%3
305
16th to endDay
13%325%38%15%3
326
August1st to 15thDay
13%5%23%35%19%3
313
16th to endDay
11%426%30%15%11%
332
September1st to 15thDay
16%5%25%24%20%6%
315
16th to endDay
17%10%25%23%15%9%
259
October1st to 15thDay
24%9%27%21%15%1
255
16th to endDay
28%12%28%23%7%
247
November1st to 15thDay
20%13%34%19%9%1
232
16th to endDay
31%15%26%21%5%
60
December1st to 15thDay
23%13%35%23%5%
60
16th to endDay
35%23%35%4
64
January1st to 15thNight
22%15%34%22%5%
720
16th to endNight
17%12%40%22%7%
768
February1st to 15thNight
17%12%40%22%5%
704
16th to endNight
22%11%37%23%4
631
March1st to 15thNight
24%11%36%23%3
720
16th to endNight
19%11%33%27%7%
768
April1st to 15thNight
26%12%28%26%4
718
16th to endNight
24%12%33%21%7%
627
May1st to 15thNight
22%6%35%24%7%2
378
16th to endNight
24%6%34%26%8%
375
June1st to 15thNight
30%6%27%28%8%
360
16th to endNight
21%427%31%14%
360
July1st to 15thNight
10%5%31%34%17%
340
16th to endNight
13%325%41%14%1
376
August1st to 15thNight
14%219%40%21%1
361
16th to endNight
13%5%24%32%21%2
755
September1st to 15thNight
16%426%36%14%1
720
16th to endNight
19%5%25%26%19%3
665
October1st to 15thNight
21%8%30%27%10%1
660
16th to endNight
29%9%29%23%6%
704
November1st to 15thNight
23%10%32%24%9%
700
16th to endNight
27%12%28%20%9%1
720
December1st to 15thNight
29%12%31%21%4
720
16th to endNight
32%12%32%18%4
768
Page generated at 2017-09-18 08:38:21. Version ac04

Copyright 2017 A. Danko


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