Joliette
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Joliette clear sky chart from 2005-11-05 to 2017-08-12.

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
34%
14459
14%
46474
9%
14427
40%
14427
18%
32945

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
23%
720
10%
2506
6%
716
29%
716
10%
1913
January16th to endNight
29%
768
11%
2688
7%
768
35%
768
13%
1996
February1st to 15thNight
26%
704
10%
2327
5%
701
32%
701
13%
1776
February16th to endNight
29%
631
13%
1893
8%
631
37%
631
16%
1410
March1st to 15thNight
28%
720
15%
2159
11%
720
33%
720
16%
1621
March16th to endNight
36%
768
19%
2001
9%
768
42%
768
25%
1411
April1st to 15thNight
30%
718
16%
1796
5%
718
36%
718
21%
1342
April16th to endNight
29%
607
16%
1687
6%
607
37%
607
22%
1182
May1st to 15thNight
33%
393
15%
1473
13%
393
41%
393
17%
1007
May16th to endNight
34%
375
12%
1497
13%
374
42%
374
16%
997
June1st to 15thNight
35%
360
8%
1440
7%
360
42%
360
15%
992
June16th to endNight
43%
360
8%
1440
10%
360
46%
360
16%
957
July1st to 15thNight
54%
340
11%
1360
17%
340
59%
340
23%
805
July16th to endNight
56%
376
12%
1418
17%
354
59%
354
23%
846
August1st to 15thNight
61%
354
14%
1403
17%
352
63%
352
19%
891
August16th to endNight
55%
676
18%
1726
10%
676
57%
676
34%
1123
September1st to 15thNight
51%
660
13%
1650
7%
660
53%
660
29%
1145
September16th to endNight
48%
657
21%
1812
14%
657
53%
657
32%
1151
October1st to 15thNight
35%
660
20%
1936
11%
660
45%
660
23%
1307
October16th to endNight
30%
704
11%
2269
7%
704
36%
704
17%
1629
November1st to 15thNight
31%
700
17%
2277
12%
700
39%
700
17%
1609
November16th to endNight
27%
720
14%
2508
9%
720
34%
720
14%
1843
December1st to 15thNight
25%
720
10%
2520
5%
720
31%
720
12%
1903
December16th to endNight
19%
768
12%
2688
5%
768
27%
768
10%
2089

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%5%35%45%6%33%
47505
Night
18%9%36%5%24445%34%
46644
TransparencyDay
49%6%12%19%9%1
47192
Night
51%6%11%19%10%1
46475
SeeingDay
21%6%25%26%15%4
5428
Night
22%5%28%31%10%
14459

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
20%12%37%7%45%34425%
1432
16th to endDay
12%16%36%6%3445%5%30%
1536
February1st to 15thDay
11%16%48%7%35%45%427%
1534
16th to endDay
16%13%5%8%6%34345%28%
1580
March1st to 15thDay
16%11%37%6%35%5%4430%
1790
16th to endDay
14%8%46%5%23345%40%
2222
April1st to 15thDay
21%8%35%424346%34%
2152
16th to endDay
20%7%245%3444438%
2271
May1st to 15thDay
21%7%36%6%245%46%31%
2487
16th to endDay
20%5%35%6%345%5%6%32%
2618
June1st to 15thDay
22%6%245%25%5%5%8%31%
2520
16th to endDay
18%5%37%6%36%5%6%8%28%
2520
July1st to 15thDay
13%425%5%46%5%7%8%35%
2520
16th to endDay
12%426%436%7%6%10%35%
2654
August1st to 15thDay
12%5%26%5%47%7%7%8%32%
2448
16th to endDay
10%3145%345%7%8%45%
2121
September1st to 15thDay
17%315%5%35%5%47%40%
1980
16th to endDay
15%5%24323347%47%
1818
October1st to 15thDay
20%7%35%5%34445%35%
1693
16th to endDay
23%8%37%5%34445%29%
1603
November1st to 15thDay
15%8%36%6%35%45%6%33%
1581
16th to endDay
22%8%26%5%3335%5%32%
1449
December1st to 15thDay
24%12%45%5%34435%26%
1440
16th to endDay
25%14%46%5%2343425%
1536
January1st to 15thNight
17%14%6%9%5%24445%25%
2506
16th to endNight
12%12%5%7%7%45%5%45%28%
2688
February1st to 15thNight
11%13%5%10%8%46%44426%
2325
16th to endNight
17%10%48%5%35%5%45%29%
1893
March1st to 15thNight
19%10%47%6%24445%30%
2147
16th to endNight
14%9%45%423435%41%
2001
April1st to 15thNight
24%7%35%43335%5%32%
1796
16th to endNight
22%7%2431446%6%36%
1687
May1st to 15thNight
21%8%26%424445%34%
1473
16th to endNight
23%5%145%33446%35%
1495
June1st to 15thNight
22%8%35%43345%6%32%
1440
16th to endNight
17%7%25%5%35%5%5%9%33%
1440
July1st to 15thNight
11%415%5%345%6%7%43%
1440
16th to endNight
12%4244345%6%8%42%
1514
August1st to 15thNight
11%426%4445%7%8%39%
1413
16th to endNight
12%41443445%6%47%
1726
September1st to 15thNight
14%5%25%42346%7%42%
1650
16th to endNight
16%5%23323336%49%
1812
October1st to 15thNight
17%6%36%5%14445%40%
1936
16th to endNight
25%8%26%423345%33%
2269
November1st to 15thNight
20%8%36%5%34436%34%
2277
16th to endNight
22%10%47%5%34325%31%
2508
December1st to 15thNight
23%11%46%5%24335%28%
2520
16th to endNight
23%15%5%7%5%2333425%
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%10%15%6%
1433
16th to endDay
54%5%11%18%9%
1536
February1st to 15thDay
58%411%18%5%
1536
16th to endDay
58%48%16%9%1
1580
March1st to 15thDay
56%411%14%10%1
1800
16th to endDay
46%5%11%18%14%4
2222
April1st to 15thDay
52%49%19%11%3
2152
16th to endDay
47%5%9%18%13%4
2271
May1st to 15thDay
51%5%9%18%12%2
2487
16th to endDay
50%6%11%18%11%1
2622
June1st to 15thDay
50%6%13%17%10%1
2520
16th to endDay
50%9%11%20%8%1
2520
July1st to 15thDay
41%8%15%22%11%
2371
16th to endDay
42%10%16%22%8%
2487
August1st to 15thDay
45%9%17%20%6%
2434
16th to endDay
33%8%20%26%10%
2121
September1st to 15thDay
41%6%15%24%11%
1980
16th to endDay
38%5%12%31%11%
1818
October1st to 15thDay
50%5%11%21%9%
1693
16th to endDay
56%5%13%18%6%
1603
November1st to 15thDay
50%6%13%20%9%
1581
16th to endDay
53%5%13%19%7%
1449
December1st to 15thDay
61%6%11%16%4
1440
16th to endDay
63%49%11%9%
1536
January1st to 15thNight
61%5%10%15%6%
2506
16th to endNight
57%6%11%15%7%1
2688
February1st to 15thNight
61%410%16%6%
2327
16th to endNight
56%49%16%11%1
1893
March1st to 15thNight
56%5%8%16%10%1
2160
16th to endNight
47%48%18%16%3
2001
April1st to 15thNight
54%36%18%14%2
1796
16th to endNight
47%6%8%18%15%3
1687
May1st to 15thNight
51%5%9%16%13%4
1473
16th to endNight
48%6%8%21%12%2
1497
June1st to 15thNight
52%5%11%17%11%1
1440
16th to endNight
47%8%11%18%13%1
1440
July1st to 15thNight
36%7%14%26%13%1
1360
16th to endNight
36%8%17%23%12%
1418
August1st to 15thNight
39%11%14%24%10%
1403
16th to endNight
35%6%15%28%13%
1726
September1st to 15thNight
40%8%13%24%12%
1650
16th to endNight
37%5%11%32%12%
1812
October1st to 15thNight
45%5%11%23%13%
1936
16th to endNight
54%413%18%8%
2269
November1st to 15thNight
51%6%12%18%9%1
2277
16th to endNight
57%410%19%7%
2508
December1st to 15thNight
59%6%12%17%4
2520
16th to endNight
63%5%8%13%7%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
30%11%21%30%6%
60
16th to endDay
31%6%21%29%6%4
64
February1st to 15thDay
31%11%31%22%3
87
16th to endDay
24%5%30%29%10%
239
March1st to 15thDay
25%7%29%28%7%
270
16th to endDay
22%5%30%26%12%3
288
April1st to 15thDay
24%12%24%24%10%3
270
16th to endDay
22%9%28%21%14%2
270
May1st to 15thDay
26%7%27%23%11%3
288
16th to endDay
21%8%29%21%16%2
331
June1st to 15thDay
26%7%24%25%13%2
315
16th to endDay
19%5%26%29%17%2
315
July1st to 15thDay
15%225%29%20%6%
305
16th to endDay
14%215%36%27%3
326
August1st to 15thDay
14%317%30%27%7%
297
16th to endDay
10%221%28%23%13%
268
September1st to 15thDay
14%418%28%20%12%
255
16th to endDay
18%5%25%20%18%11%
254
October1st to 15thDay
21%7%24%26%17%2
255
16th to endDay
30%7%22%23%14%
243
November1st to 15thDay
20%5%32%26%13%1
235
16th to endDay
34%5%21%24%13%
69
December1st to 15thDay
30%6%26%25%8%3
60
16th to endDay
40%7%39%12%
64
January1st to 15thNight
25%9%30%27%7%
720
16th to endNight
18%6%33%32%8%
768
February1st to 15thNight
18%6%35%30%8%
704
16th to endNight
21%5%33%32%6%
631
March1st to 15thNight
25%5%32%31%4
720
16th to endNight
19%5%31%32%11%
768
April1st to 15thNight
27%6%30%29%5%
718
16th to endNight
26%7%31%25%8%
607
May1st to 15thNight
25%330%31%7%1
393
16th to endNight
25%231%31%8%
375
June1st to 15thNight
28%326%31%10%
360
16th to endNight
19%226%37%14%
360
July1st to 15thNight
12%224%39%18%1
340
16th to endNight
12%219%47%16%1
376
August1st to 15thNight
13%114%44%24%1
354
16th to endNight
15%220%37%22%1
676
September1st to 15thNight
18%319%40%16%1
660
16th to endNight
19%224%33%17%2
657
October1st to 15thNight
21%429%32%10%
660
16th to endNight
31%5%27%26%8%
704
November1st to 15thNight
24%5%31%25%12%1
700
16th to endNight
27%7%29%23%9%1
720
December1st to 15thNight
30%5%29%27%6%
720
16th to endNight
30%8%30%23%6%1
768
Page generated at 2017-08-13 14:16:33. Version ac04

Copyright 2017 A. Danko


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